Title of Invention	METHOD FOR THE PRODUCTION OF ACROLEIN
Abstract	ABSTRACT 2756/MAS/97 A METHOD FOR PRODUCING ACROLEIN The present invention relates to a method for producing acrolein by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed bed multitubular reactor which comprises a) using a plurality catalysts differing the activities in the amount of the catalytically active component supported on the carrier and the higher catalytic activity being displayed by the carriers supporting the larger amount of the catalytically active component and the catalytically active components having a composition represented by the following formula wherein Mo, Bi, Ni, Co and Fe represent molybdenum, bismuth, nickel, cobalt and iron, respectively, Y is at least one element selected from the group of tin, zinc, tungsten, chromium, manganese, magnesium, antimony and titanium, Z is at least one element selected from the group of potassium, rubidium, thallium and cesium, and a, b, c, d, f, g, h and x represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron respectively, Y, Z and oxygen, a = 12, b = 0.1 to 7, c + d =0.5 to 20, f = 0.5 to 8, g = 0 to 2, h = 0 to 1 and X is determined by the oxidized condition of each element, b) setting a catalyst layer in a reaction tube, which is formed by dividing it into plural portions in the tube axial direction, and c) arranging the aforementioned plural supported catalysts in such a manner that the activity becomes high toward the outlet from the inlet of the maternal gas in the reaction tube axial direction.

Title of Invention

METHOD FOR THE PRODUCTION OF ACROLEIN

Abstract

ABSTRACT 2756/MAS/97 A METHOD FOR PRODUCING ACROLEIN The present invention relates to a method for producing acrolein by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed bed multitubular reactor which comprises a) using a plurality catalysts differing the activities in the amount of the catalytically active component supported on the carrier and the higher catalytic activity being displayed by the carriers supporting the larger amount of the catalytically active component and the catalytically active components having a composition represented by the following formula wherein Mo, Bi, Ni, Co and Fe represent molybdenum, bismuth, nickel, cobalt and iron, respectively, Y is at least one element selected from the group of tin, zinc, tungsten, chromium, manganese, magnesium, antimony and titanium, Z is at least one element selected from the group of potassium, rubidium, thallium and cesium, and a, b, c, d, f, g, h and x represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron respectively, Y, Z and oxygen, a = 12, b = 0.1 to 7, c + d =0.5 to 20, f = 0.5 to 8, g = 0 to 2, h = 0 to 1 and X is determined by the oxidized condition of each element, b) setting a catalyst layer in a reaction tube, which is formed by dividing it into plural portions in the tube axial direction, and c) arranging the aforementioned plural supported catalysts in such a manner that the activity becomes high toward the outlet from the inlet of the maternal gas in the reaction tube axial direction.

Full Text	[Field of the Invention] This invention relates to a method in which acrolein and acrylic acid are produced by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed bed multitubular reactor. [Prior Art] A number of complex oxide catalysts containing molybdenum, bismuth and iron have already been proposed for use in the production of acrolein and acrylic acid by a method in which propylene is subjected to vapor phase catalytic oxidation, and some of them are now industrially used. Their typical examples include those which are disclosed in Japanese Patent Publication (KOKOKU) No. 47-27490 (1972), Japanese Patent Publication (KOKOKU) No. 47-42241 (1972) and Japanese Patent Publication (KOKOKU) No. 48-1645 (1973). However, industrial production of acrolein or acrylic acid using these catalysts causes various problems. One of these problems is generation of a local abnormally high temperature part (hot spot) in the catalyst layer. Generation of the hot spot is caused by the exothermic reaction of said vapor phase catalytic reaction. In order to improve productivity in the industrial production of acrolein and acrylic acid, a means is generally employed in which the concentration of the starting material propylene is increased or the space velocity of the reaction gas is increased, but heat accumulation at the hot spot is increased under such high load reaction conditions. Increase in heat accumulation at the hot spot causes shortened catalyst life, increased formation of by-products due to over oxidation reaction and, in the worst case, runaway reaction. If the activity of a part of the catalyst wherein the hot spot is generated is decreased, the activity of the whole catalyst is probably lowered due to migration of hot spots to other layers (parts) of the catalyst. In order to avoid generation of such hot spot or excessive heat accumulation at the hot spot, one must unwillingly accept low productivity or must take a countermeasure for example by reducing the reaction tube diameter, which, however, are economically disadvantageous. In consequence, various studies have been reported, in order to avoid the aforementioned danger in reaction operations caused by the hot spot to ensure economy in the aforementioned industrial production. For example, a method in which a catalyst wherein the hot spot could be generated is diluted with an inert substance (Japanese Patent Publication (KOKOKU) No. 53-30688 (1978)) and a method in which the catalyst to be used is made into a tublar shape (Japanese Patent Publication (KOKOKU) No. 62-36739 (1987)) have been proposed. Also, reaction methods have been proposed in which two or more reaction zones are arranged in a reaction tube, and in which the reaction is carried out by packing a plurality of catalysts having different activities. Examples of such a type of methods so far reported include a method in which a plurality of catalysts whose activities are controlled by changing composition of catalytically active components (kind and/or quantity of an alkali metal in particular) are packed in a reaction tube along its axis in such a manner that catalysts having higher activities are arranged toward the outlet side from the inlet side of the material gas (Japanese Patent Publication (KOKOKU) No. 63-38331 (1988)) and a method in which a plurality of catalysts having different occupying volumes are packed in a plurality of reaction zones in such a manner that the occupying volume becomes small toward the outlet side from the inlet side of the reaction tube (Japanese Patent Application Kokai No. 4-217932 (1992)). However, in the method in which a catalyst is diluted with an inert substance, an intensive effort is required in uniformly mixing the inert substance for dilution with the catalyst, but their uniform packing cannot always be effected by this method, thus not only causing frequent generation of hot spots but also entailing inconvenience in carrying out the reaction, because the position and temperature of the hot spot vary in each reaction tube, so that this is not a satisfactory method as a means to prevent generation of hot spot. The method in which the activity of catalyst is controlled by making it into a tublar shape cannot also be said as a sufficient means for preventing the generation of hot spots or excessive heat accumulation at the hot spot under high load reaction conditions. namely under conditions of high starting material concentration and high space velocity. In the method in which the activity of catalyst is controlled by changing kind and/or quantity of an alkali metal, its amount to be added is markedly small in comparison with those of other components, so that extent of activity variation of the catalyst by its adding is extremely large and the handling at the time of catalyst preparation therefore becomes considerably difficult. In addition, activity control of the catalyst becomes more difficult due to the influence of alkali metals slightly contained in other starting materials which are added in large amounts. When a plurality of catalysts having different active components are used, these catalysts show different periodical changes during their use for a prolonged period of time, so that it is necessary to optimize the catalyst layer length, the catalyst activity and the like factors taking the periodical changes into consideration, thus requiring complex operations. In the method in which a plurality of catalysts having different occupying volumes are packed in a reaction tube in such a manner that the occupying volume becomes small toward its outlet side from the inlet side of the reaction tube, thereby arranging a plurality of reaction zones in the axial direction of the reaction tube, it is necessary to control the ratio of occupying volumes of adjacent two reaction zones within a specified range, and it also requires further complex operations in achieving its optimization when the shape, composition and the like factors of the catalysts are different from one another, in addition to the occupying volumes of the catalysts to be used. The present invention contemplates resolving the aforementioned problems in the prior art, thereby providing a method by which acrolein and acrylic acid can be produced from propylene with a high efficiency. That is, it contemplates providing a method in which acrolein and acrylic acid are produced by subjecting propylene to vapor phase catalytic oxidation under high load reaction conditions, which is a simple and easy method that can effect the production stably for a prolonged period of time by inhibiting generation of hot spots or excessive heat accumulation at the hot spot of the catalyst layer, obtaining the products of interest with high yields and preventing the catalyst from its deterioration by thermal load. [Summary of the Invention] In the exothermic reaction such as the case of the vapor phase catalytic oxidation reaction of the present invention, catalytically active components are generally used by molding them into various shapes which components are mostly occupied by the catalytically active components. Since the catalyst can be regarded as the reaction field of vapor phase catalytic oxidation, the exothermic reaction occurs exactly on the catalyst. Thus, the heat generated by the reaction is concentrated to induce generation of hot spots. In view of the above, the inventors of the present invention have conducted intensive studies with the aim of obtaining the products of interest stably for a prolonged period of time by avoiding the concentration of heat of reaction generated on the catalyst, and found as a result of the efforts that the aforementioned object can be achieved when a plurality of supported catalysts having different activities, which are prepared by controlling the amount of a powder that contains catalytically active components to be supported (coated) on an inert carrier and calcining temperature and calcining time of the catalysts, are used by arranging them in a specified manner. In this connection, the term "activity" as used herein means reactivity of propylene and has the same meaning as conversion ratio. Accordingly, the present invention relates to: (1) a method for producing acrolein and acrylic acid by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed bed multitubular reactor, which comprises a) using a plurality of supported catalysts having different activities, which carry a powder that contains catalytically active components having a composition represented by the folowing formula Mo^B^Ni^COdFe^YgZhO, (wherein Mo, Bi, Ni, Co and Fe represent molybdenum, bismuth, nickel, cobalt and iron, respectively, Y is at least one element selected from the group of tin, zinc, tungsten, chromium, manganese, magnesium, antimony and titanium, Z is at least one element selected from the group of potassium, rubidium, thallium and cesium, and a, b, c, d, f, g, h and x represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, Y, Z and oxygen, respectively, a = 12,b = 0.1 to 7, c + d = 0.6 to 20, f = 0.5 to 8, g = 0 to 2, h = 0 to 1 and X is determined by the oxidized condition of each element), b) setting a catalyst layer in a reaction tube, which is formed by dividing it into plural portions in the tube axial direction, and c) arranging the aforementioned plural supported catalysts in such order that the activity becomes high toward the outlet from the inlet of the material gas in the reaction tube axial direction, (2) the method according to the above item (1) wherein the catalysts are used whose activity strength is controlled by means of the supported amount of the powder that contains catalytically active components, when it is supported on a carrier, and/or the calcining treatment of the powder that contains catalytically active components after it is supported on the carrier, (3) the method according to the above item (1) or (2) wherein the plural catalysts to be used have the same composition of catalytically active components, (4) the method according to any one of the above items (1) to (3) wherein the carrier of the plural catalysts to be used is the same, {5) the method according to any one of the above items (1) to (4) wherein the powder that contains catalytically active components further contains a molding additive and/or a strength improving agent, and (6) the method according to any one of the above items (1) to (5) wherein it uses a catalyst in which particle size of the catalyst is 3.5 to 16 mm, the amount of the catalytically active component-containing powder to be supported on the carrier is 10 to 60% by weight (catalytically active components/(catalytically active components + carrier + strength improving agent (optional component)), and the calcining temperature of the catalytically active component-containing powder after it is supported is 450 to 650°C. [Detailed Description of the Invention] The following describes the present invention in detail. The catalyst to be used in the present invention can be obtained by a method in which a powder that contains catalytically active components having a composition of the following formula is supported v on a carrier and then calcined. J/iO h LoV *■■ 1 V^ r Mo,Bi,Ni,Co,Fe,Y,ZhO, (In this formula. Mo, Bi, Ni, Co and Fe represent molybdenum, bismuth,^Xy 4 nickel, cobalt and iron, respectively, Y is at least one element ^/^ selected from the group of tin, zinc, tungsten, chromium, manganese, magnesium, antimony and titanium, Z is at least one element selected from the group of potassium, rubidium, thallium and cesium, and a, b, c, d, f, g, h and x represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, Y, Z and oxygen, a = 12, b = 0.1 to 7, c+d=0.5to20, f=0.5to8, g=0to2, h=Otol and x is determined by the oxidized condition of each element.) In the above definition, it is desirable that a = 12, b = 0.5to4, c + d=lto 12, f = 0.5to5, g = Otol and h = 0.01tb0.5. The powder containing catalytically active components is prepared by a coprecipitation, spray drying or the like means, using nitrate, ammonium salt, hydroxide, oxide, acetate and the like salts of respective metal elements as the starting materials with no particular limitation. The powder containing catalytically active components is usually subjected to preliminary calcination at a temperature of from 200 to 600°C for from 2 to 24 hours prior to its supporting on a carrier. The preliminary calcination is carried out preferably in the atmosphere of air or in a stream of nitrogen. The thus obtained powder by the preliminary calcination is called preliminarily calcined powder hereinafter. In addition, in a plurality of catalysts having different activities, compositions of the catalytically active components of these catalysts (preliminarily calcined powder) may be the same or different from one another, but preferably the same. When the preliminarily calcined powder described above is supported on a carrier, it is desirable to mix it with a molding additive and/or a strength improving agent. Illustrative examples of the molding additive include crystalline cellulose, starch, stearic acid and the like, and those of the strength improving agent include ceramic fibers, carbon fibers, whiskers and the like. The molding additive or strength improving agent is used in an amount of 30% by weight or less based on the preliminarily calcined powder. The molding additive and/or strength improving agent may be mixed in advance with the aforementioned preliminarily calcined powder prior to molding or, as will be described later, may be added to a molding machine simultaneously with or before or after the addition of the preliminarily calcined powder and the like. The carrier can be made into spherical, cylindrical, tublar and the like shapes with no specific limitation, but a spherical shape is particularly desirable when production efficiency and mechanical strength of the catalyst are taken into consideration. Also, it is desirable to use a binder when the preliminarily calcined powder is supported on the carrier. Illustrative examples of the binder include water, an alcohol, a polyhydric alcohol such as glycerol or the like or a mixture thereof. The binder is used in an amount of from 10 to 60% by weight based on the preliminarily calcined powder. Any material can be used as the carrier as long as it is inert and porous or can be made into porous granules, and its examples include a-alumina, silicon carbide, pumice, silica, zirconium oxide, titanium oxide and the like. The carrier may have a particle size of preferably from 3 to 12 mm. Types of the carrier for a plurality of catalysts may be the same or different from one another, but they may preferably be the same. The powder that contains the catalytically active components (the powder containing preliminarily calcined powder, if necessary further containing a molding additive and/or a strength improving agent, to be referred to as catalytically active component-containing powder hereinafter) can be supported on the carrier by any method such as a tumbling granulation method, a method using a centrifugal f luidized bed coating apparatus and a wash coating method, with no particular limitation, but the tumbling granulation method is desirable when catalyst production efficiency and the like are taken into consideration. Illustratively, this is a method in which a fixed cylindrical container whose bottom part is equipped with a disc having even or irregular surface is used, and a carrier charged in the container is vigorously mixed through the repetition of rotation and revolution effected by high speed spinning of the disc, to which the catalytically active component-containing powder and, if necessary, a binder are added so that said powder is supported on the carrier. According to the present invention, a plurality of catalysts having different activities are used which are obtained by calcining a powder that contains the aforementioned active components and is supported on a carrier. The catalysts whose activity is controlled by means of the supported amount of the catalytically active components in the catalytically active component-containing powder and/or the calcination temperature and calcination time of the catalytically active component-containing powder after supporting it on a carrier, are used in a certain arrangement in a specified combination. That is, a plurality of reaction zones are provided in the catalyst layer, and the supported catalysts having different activities are arranged in respective reaction zones in such a manner that the activity becomes high toward the outlet from the inlet of the starting material gas in the reaction tube axial direction. The activities of the catalysts are controlled by the amount of the catalytically active components to be supported and the activity becomes high as the supported amount increases. The supported amount is preferably from 5 to 80% by weight, more preferably from 10 to 60% by weight. In this connection, the supported amount is represented by "weight of catalytically active components/(weight of catalytically active components + weight of carrier + weight of strength improving agent (optional component)", and is referred to as catalyst supported ratio hereinafter. The term "weight of catalytically active components" as used herein means weight of the preliminarily calcined powder. According to the present invention, the activity of catalyst is also controlled by calcination temperature and the activity becomes high as the calcination temperature is reduced. The calcination temperature is preferably from 450 to 650°C, more preferably from 480 to 600°C. The calcination time is generally from 3 to 30 hours, preferably from 4 to 15 hours. Within this range of calcination time, the catalyst activity becomes high as the baking time is shortened. The preferred combination of calcination temperature and time is varied depending on the supported amount of catalytically active components. For example, when the catalyst layer is divided into two parts a catalyst prepared by calcination at 500-650°C for 4-15 hours is preferably combined with a catalyst prepared by calcination at 450-550°C for 4-10 hours while the catalyst layer is divided into three parts a catalyst prepared by calcination at 500-650°C for 4-15 hours is preferably combined with a catalyst prepared by calcination at 500-580°C for 4-15 hours and a catalyst prepared by calcination at 450-550°C for 4-10 hours. The catalyst activity is decreased as the particle size of catalyst is increased if the catalyst supports catalytically active components having the same composition. The particle size of catalyst is determined by the particle size of carrier and the carrier supported ratio, and it is preferably determined by taking inner diameter of the reaction tube and the like into consideration. In the case of the catalysts to be used in the present invention in which the same carrier is used for a plurality of catalysts having different activities, particle size of the catalysts becomes slightly large as the amounts to be supported increase, when the catalytically active components are supported on the carrier under the same conditions, but is almost the same as long as the supported amounts are not changed greatly. The particle size of catalyst is usually 3.5 to 16 mm. According to the present invention, a fixed bed multitubular reactor is used as the reactor, and the number of reaction tubes, the packing length of the catalyst, the number of divided portions of catalyst layer and the like vary depending on the operation conditions, so that these factors may be decided in each case in such a manner that optimum operation results are obtained. With regard to the division of catalyst layer, prevention of the generation of hot spots or heat accumulation in the hot spot becomes easy as the number of divided portions increases, but the object can be achieved practically by dividing it into 2 to 3 portions. Inner diameter of the reaction tube is generally from about 15 to 50 mm. For example, when the inner diameter of reaction tube is 21 to 27 mm in that case, it is desirable to use a combination of catalysts having a particle size of 3.5 to 8 mm whose activities are controlled by adjusting the supported amount in the catalysts to 15 to 60% by weight, and the calcination temperature to 480 to 580°C. The production method of the present invention may be applied to a once-through (one-pass) operation method or a recycling method, and can be carried out under conditions generally used on them. For example, the reaction may be carried out by introducing a mixture gas consisting of 1 to 10% by volume, preferably 4 to 9% by volume, of propylene as the starting material, 3 to 20% by volume, preferably 4 to 18% by volume, of molecular oxygen, 0 to 60% by volume, preferably 4 to 50% by volume, of water vapor and 20 to 80% by volume, preferably 30 to 60% by voliame, of an inert gas (nitrogen, carbon dioxide or the like) onto the aforementioned catalysts at a temperature of 250 to 450°C, under a pressure of atmospheric pressure to 10 atm and at a space velocity ( = material gas flow volume/apparent volume of packed catalysts) of 300 to 5,000 hr"^ [Effects of the Invention] According to the present invention, run away reaction caused by the generation of hot spot and over oxidation reaction can be avoided and constant operation can be made for a prolonged period of time without employing industrially disadvantageous methods, even under high load reaction conditions in which concentration of the starting material is increased and/or the space velocity is increased, so that the method of the present invention is an outstandingly superior method in comparison with the prior art methods. When the reaction is carried out according to the present invention by supporting a catalytically active component-containing powder on a carrier, calcining the resultant and then packing a plurality of the thus obtained catalysts having different activities in each of a plurality of reaction zones arranged in the reaction tube axial direction in such order that the catalyst with lower activity is placed from the inlet of the starting material, the danger of causing runaway reaction due to the generation of hot spots or heat accumulation at the hot spot can be avoided and formation of by-products due to over oxidation reaction can be prevented, even under high load reaction conditions, so that the intended acrolein and acrylic acid can be obtained with high selectivity and high yield. The productivity can also be improved markedly, because deterioration of the catalyst due to locally exceeded thermal load can be prevented and the catalyst therefore can be used stably for a prolonged period of time. Thus, the production method of the present invention is a markedly useful method for the production of acrolein and acrylic acid. [Examples] The present invention is described further illustratively with reference to the following examples. The conversion ratio, the selectivity and the yield per pass in the present invention are defined as follows. Propylene conversion ratio (mol %) = (mol number of reacted propylene)/(mol number of supplied propylene) x 100 Total selectivity (mol %) = (mol number of formed acrolein and acrylic acid)/(mol number of reacted propylene) x 100 Yield (mol %) = (mol number of formed acrolein or acrylic acid)/(mol number of supplied propylene) x 100 Example 1 (Preparation of catalyst - 1) An aqueous solution (A) was obtained by dissolving 423.8 g of ammonium molybdate and 2.02 g of potassium nitrate in 3,000 ml of distilled water which was heated and stirred. Separately from this, an aqueous solution (B) was prepared by dissolving 302.7 g of cobalt nitrate, 162.9 g of nickel nitrate and 145.4 g of ferric nitrate in 1,000 ml of distilled water, and an aqueous solution (C) by dissolving 164.9 g of bismuth nitrate in 200 ml of distilled water which had been acidified by adding 25 ml of concentrated nitric acid. The aqueous solutions (B) and (C) were mixed, and the mixture solution was added dropwise to the aqueous solution (A) which was vigorously stirred. The thus formed suspension was dried using a spray dryer and subjected to 3 hours of preliminary calcination at 440°C, thereby obtaining 570 g of preliminarily calcined powder. Thereafter, 200 g of the preliminarily calcined powder was mixed with 10 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and the crystalline cellulose was obtained. A 300 g portion of alumina carrier having an average particle size of 3.5 mm was put into a tumbling granulator and then the just described mixture and 90 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 40% by weight (to be referred to as active component-supported particles hereinafter). The active component-supported particles were dried at room temperature for 15 hours and then calcined at 560°C for 5 hours in the flow of air to obtain a catalyst (1). The catalyst (1) was found to have an average particle size of 4.0 mm, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi=1.7, Ni=2.8, Fe=1.8, Co =5.2 and K = 0.1 in atomic ratio. (Preparation of catalyst - 2) A 300 g portion of the preliminarily baked powder obtained in Preparation of catalyst - 1 was mixed with 15 g of crystalline cellulose as a molding additive, and thus obtained a mixture of the preliminarily clcined powder and the crystalline cellulose was obtained. A 300 g portion of alumina carrier having an average particle size of 3.5 mm was put into a tumbling granulator and then the above-mentioned mixture and 135 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 50% by weight. The thus obtained active component-supported particles were dried at room temperature for 15 hours and then calcined at 520°C for 5 hours in the flow of air to obtain a catalyst (2). The catalyst (2) was found to have an average particle size of 4.1 mm, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Oxidation reaction) The aforementioned catalysts (1) and (2) were packed in a reaction tube of 21 mm in inner diameter and 5 m in length made of stainless steel (SUS 304) and equipped with a thermocouple, in respective packed layer lengths of 105 cm and 295 cm at central area of the reaction tube starting from the starting material gas inlet toward the outlet. While keeping the reaction bath temperature at 337°C and the catalyst layer inlet pressure at 1.53 kg/cm^ G, the reaction was carried out by passing a mixture gas consisting of 8% by volume of propylene, 14% by volume of oxygen, 25% by volume of water vapor and 53% by volume of nitrogen through the tube at a space velocity of 1,860 hr'^. In this case, maximum temperatures of the catalyst layers starting from the inlet were 388°C and 400°C, respectively, the propylene conversion ratio was 97.1%, the acrolein yield was 80.9%, the acrylic acid yield was 8.1% and the total selectivity for acrolein and acrylic acid was 91.7%, and decrease in reaction performance was not observed even after continuation of the reaction for 1,000 hours or more. Example 2 (Preparation of catalyst - 3) A catalyst (3) was obtained in the same manner as described in Preparation of catalyst - 1, except that the calcining temperature was changed to 540°C. The catalyst (3) was found to have an average particle size of 4.0 ram, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Oxidation reaction) The aforementioned catalysts (3) and (2) were packed in a reaction tube of 21 mm in inner diameter and 5 m in length made of stainless steel (SUS 304) and equipped with a thermocouple, in respective packed layer lengths of 105 cm and 295 cm starting from the starting material gas inlet toward the outlet. While keeping the reaction bath temperature at 333°C and the catalyst layer inlet pressure at 1.17 kg/cm^ G, the reaction was carried out by passing a mixture gas consisting of 8% by volume of propylene, 14% by volume of oxygen, 25% by volume of water vapor and 53% by volume of nitrogen through the tube at a space velocity of 1,550 hr"^. In this case, maximum temperatures of the catalyst layers starting from the inlet were 401°C and 373°C, respectively, the propylene conversion ratio was 98.1%, the acrolein yield was 81.3%, the acrylic acid yield was 8.6% and the total selectivity for acrolein and acrylic acid was 91.6%, and decrease in reaction performance was not observed even after continuation of the reaction for 1,000 hours or more. Example 3 (Preparation of catalyst - 4) A 100 g portion of the preliminarily calcined powder obtained in Preparation of catalyst - 1 was mixed with 5 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and the crystalline cellulose was obtained. A 300 g portion of alumina carrier having an average particle size of 4 mm was put into a tumbling granulator and then the just described mixture and 45 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 25% by weight. The thus obtained active component-supported particles were dried at room temperature for 15 hours and then calcined at 520°C for 5 hours in the flow of air to obtain a catalyst (4 ). The catalyst (4) was found to have an average particle size of 4.3 mm, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Preparation of catalyst - 5) A 150 g portion of the preliminarily calcined powder obtained in Preparation of catalyst - 1 was mixed with 7.5 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and the crystalline cellulose was obtained. A 300 g portion of alumina carrier having an average particle size of 4 mm was put into a tumbling granulator and then the described mixture and 70 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 33% by weight. The thus obtained active component-supported particles were dried at room temperature for 15 hours and then calcined at 520°C for 5 hours in the flow of air to obtain a catalyst (5). The catalyst (5) was found to have an average particle size of 4.5 ram, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Preparation of catalyst - 6) A 200 g portion of the preliminarily calcined powder obtained in Preparation of catalyst - 1 was mixed with 10 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and crystalline cellulose was obtained. A 300 g portion of alumina carrier having an average particle size of 4 mm was put into a tumbling granulator and then the described mixture and 90 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 40% by weight. The thus obtained active component-supported particles were dried at room temperature for 15 hours and then calcined at 520°C for 5 hours in the flow of air to obtain a catalyst (6). The catalyst (6) was found to have an average particle size of 4.5 ram, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Oxidation reaction) The aforementioned catalysts {4), {5) and (6) were packed in a reaction tube of 27 mm in inner diameter and 5 m in length made of stainless steel (SUS 304) and equipped with a thermocouple, in respective packed layer lengths of 100 cm, 100 cm and 150 cm starting from the starting material gas inlet toward the outlet. While keeping the reaction bath temperature at 334°C and the catalyst layer inlet pressure at 1.35 kg/cm^ G, the reaction was carried out by passing a mixture gas consisting of 7% by volume of propylene, 13% by volume of oxygen, 10% by volume of water vapor and 70% by volume of nitrogen through the tube at a space velocity of 1,800 hr"^. In this case, maximum temperatures of the catalyst layers starting from the inlet were 404°C, 385°C and 352°C, respectively, the propylene conversion ratio was 96.6%, the acrolein yield was 84 .2%, the acrylic acid yield was 6.2% and the total selectivity for acrolein and acrylic acid was 93.6%, and decrease in reaction performance was not observed even after continuation of the reaction for 1,000 hours or more. Example 4 The reaction was carried out in the same manner as described in Example 3, except that the space velocity was changed to 1,500 hr"\ the reaction bath temperature to 332°C and the catalyst layer inlet pressure to 1.1 kg/cm^ G. In this case, maximum temperatures of the catalyst layers were 398°C, 381°C and 350°C, respectively, the propylene conversion ratio was 96.4%, the acrolein yield was 84.3%, the acrylic acid yield was 6.0% and the total selectivity for acrolein and acrylic acid was 93.6%, and decrease in the reaction results was not observed even after continuation of the reaction for 1,000 hours or more. Example 5 (Preparation of catalyst - 7) A 200 g portion of the preliminarily calcined powder obtained in Preparation of catalyst - 1 was mixed with 10 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and the crystalline cellulose was obtained. A 300 g portion of alumina carrier having an average particle size of 4 mm was put into a tumbling granulator and then the described mixture and 90 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 40% by weight. The thus obtained active component-supported particles were dried at room temperature for 15 hours and then calcined at 550°C for 5 hours in the flow of air to obtain a catalyst (7 ). The catalyst (7) was found to have an average particle size of 4.5 mm, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Oxidation reaction) The aforementioned catalysts (7) and (6) were packed in a reaction tube of 21 mm in inner diameter and 5 m in length made of stainless steel (SUS 304) and equipped with a thermocouple, in respective packed layer lengths of 105 cm and 295 cm starting from the starting material gas inlet toward the outlet. While keeping the reaction bath temperature at 339°C and the catalyst layer inlet pressure at 1.81 kg/cm^ G, the reaction was carried out by passing a mixture gas consisting of 8% by volume of propylene, 14% by volume of oxygen, 25% by volume of water vapor and 53% by volume of nitrogen through the tube at a space velocity of 1,860 hr'^. In this case, maximum temperatures of the catalyst layers starting from the inlet were 406°C and 397°C, respectively, the propylene conversion ratio was 97.4%, the acrolein yield was 79.9%, the acrylic acid yield was 8.9% and the total selectivity for acrolein and acrylic acid was 91.2%, and decrease in reaction performance was not observed even after continuation of the reaction for 1,000 hours or more. WE CLAIM: 1. A method for producing acrolein by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed bed multitubular reactor which comprises a) using a plurality catalysts differing the activities in the amount of the catalytically active component supported on the carrier and the higher catalytic activity being displayed by the carriers supporting the larger amount of the catalytically active component and the catalytically active components having a composition represented by the following formula wherein Mo, Bi, Ni, Co and Fe represent molybdenum, bismuth, nickel, cobalt and iron, respectively, Y is at least one element selected from the group of tin, zinc, tungsten, chromium, manganese, magnesium, antimony and titanium, Z is at least one element selected from the group of potassium, rubidium, thallium and cesium, and a, b, c, d, f, g, h and x represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron respectively, Y, Z and oxygen, a = 12, b = 0.1 to 7, c + d =0.5 to 20, f = 0.5 to 8, g = 0 to 2, h = 0 to 1 and X is determined by the oxidized condition of each element, b) setting a catalyst layer in a reaction tube, which is formed by dividing it into plural portions in the tube axial direction, and c) arranging the aforementioned plural supported catalysts in such a manner that the activity becomes high toward the outlet from the inlet of the maternal gas in the reaction tube axial direction. 2. The method as claimed in claim 1, wherein the catalysts are used whose activity is controlled by means of by the supported amount of the powder that contains catalytically active components, when it is supported on a carrier, and/or the calcinations treatment of the powder that contains catalytically active components after it is supported on the carrier. 3. The method as claimed in claim 1 or 2, wherein the plurality catalysts to be used have the same composition of catalytically active components. 4. The method as claimed in any one of claims 1 to 3, wherein the carrier of the plural catalysts to be used is the same. 5. The method as claimed in any one of claims 1 to 4, wherein the powder that contains catalytically components contains a molding additives and/or a strength improving agent. 6. A method for producing acrolein substantially as herein described and exemplified.

Full Text

[Field of the Invention]
This invention relates to a method in which acrolein and acrylic acid are produced by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed bed multitubular reactor. [Prior Art]
A number of complex oxide catalysts containing molybdenum, bismuth and iron have already been proposed for use in the production of acrolein and acrylic acid by a method in which propylene is subjected to vapor phase catalytic oxidation, and some of them are now industrially used. Their typical examples include those which are disclosed in Japanese Patent Publication (KOKOKU) No. 47-27490 (1972), Japanese Patent Publication (KOKOKU) No. 47-42241 (1972) and Japanese Patent Publication (KOKOKU) No. 48-1645 (1973).
However, industrial production of acrolein or acrylic acid using these catalysts causes various problems.
One of these problems is generation of a local abnormally high temperature part (hot spot) in the catalyst layer. Generation of the hot spot is caused by the exothermic reaction of said vapor phase catalytic reaction. In order to improve productivity in the industrial production of acrolein and acrylic acid, a means is generally employed in which the concentration of the starting material propylene is increased or the space velocity of the reaction

gas is increased, but heat accumulation at the hot spot is increased under such high load reaction conditions. Increase in heat accumulation at the hot spot causes shortened catalyst life, increased formation of by-products due to over oxidation reaction and, in the worst case, runaway reaction.
If the activity of a part of the catalyst wherein the hot spot is generated is decreased, the activity of the whole catalyst is probably lowered due to migration of hot spots to other layers (parts) of the catalyst.
In order to avoid generation of such hot spot or excessive heat accumulation at the hot spot, one must unwillingly accept low productivity or must take a countermeasure for example by reducing the reaction tube diameter, which, however, are economically disadvantageous.
In consequence, various studies have been reported, in order to avoid the aforementioned danger in reaction operations caused by the hot spot to ensure economy in the aforementioned industrial production. For example, a method in which a catalyst wherein the hot spot could be generated is diluted with an inert substance (Japanese Patent Publication (KOKOKU) No. 53-30688 (1978)) and a method in which the catalyst to be used is made into a tublar shape (Japanese Patent Publication (KOKOKU) No. 62-36739 (1987)) have been proposed.
Also, reaction methods have been proposed in which two or more reaction zones are arranged in a reaction tube, and in which the reaction is carried out by packing a plurality of catalysts having

different activities. Examples of such a type of methods so far reported include a method in which a plurality of catalysts whose activities are controlled by changing composition of catalytically active components (kind and/or quantity of an alkali metal in particular) are packed in a reaction tube along its axis in such a manner that catalysts having higher activities are arranged toward the outlet side from the inlet side of the material gas (Japanese Patent Publication (KOKOKU) No. 63-38331 (1988)) and a method in which a plurality of catalysts having different occupying volumes are packed in a plurality of reaction zones in such a manner that the occupying volume becomes small toward the outlet side from the inlet side of the reaction tube (Japanese Patent Application Kokai No. 4-217932 (1992)).
However, in the method in which a catalyst is diluted with an inert substance, an intensive effort is required in uniformly mixing the inert substance for dilution with the catalyst, but their uniform packing cannot always be effected by this method, thus not only causing frequent generation of hot spots but also entailing inconvenience in carrying out the reaction, because the position and temperature of the hot spot vary in each reaction tube, so that this is not a satisfactory method as a means to prevent generation of hot spot.
The method in which the activity of catalyst is controlled by making it into a tublar shape cannot also be said as a sufficient means for preventing the generation of hot spots or excessive heat accumulation at the hot spot under high load reaction conditions.

namely under conditions of high starting material concentration and high space velocity.
In the method in which the activity of catalyst is controlled by changing kind and/or quantity of an alkali metal, its amount to be added is markedly small in comparison with those of other components, so that extent of activity variation of the catalyst by its adding is extremely large and the handling at the time of catalyst preparation therefore becomes considerably difficult. In addition, activity control of the catalyst becomes more difficult due to the influence of alkali metals slightly contained in other starting materials which are added in large amounts. When a plurality of catalysts having different active components are used, these catalysts show different periodical changes during their use for a prolonged period of time, so that it is necessary to optimize the catalyst layer length, the catalyst activity and the like factors taking the periodical changes into consideration, thus requiring complex operations.
In the method in which a plurality of catalysts having different occupying volumes are packed in a reaction tube in such a manner that the occupying volume becomes small toward its outlet side from the inlet side of the reaction tube, thereby arranging a plurality of reaction zones in the axial direction of the reaction tube, it is necessary to control the ratio of occupying volumes of adjacent two reaction zones within a specified range, and it also requires further complex operations in achieving its optimization when the shape, composition and the like factors of the catalysts

are different from one another, in addition to the occupying volumes of the catalysts to be used.
The present invention contemplates resolving the aforementioned problems in the prior art, thereby providing a method by which acrolein and acrylic acid can be produced from propylene with a high efficiency.
That is, it contemplates providing a method in which acrolein and acrylic acid are produced by subjecting propylene to vapor phase catalytic oxidation under high load reaction conditions, which is a simple and easy method that can effect the production stably for a prolonged period of time by inhibiting generation of hot spots or excessive heat accumulation at the hot spot of the catalyst layer, obtaining the products of interest with high yields and preventing the catalyst from its deterioration by thermal load. [Summary of the Invention]
In the exothermic reaction such as the case of the vapor phase catalytic oxidation reaction of the present invention, catalytically active components are generally used by molding them into various shapes which components are mostly occupied by the catalytically active components. Since the catalyst can be regarded as the reaction field of vapor phase catalytic oxidation, the exothermic reaction occurs exactly on the catalyst. Thus, the heat generated by the reaction is concentrated to induce generation of hot spots. In view of the above, the inventors of the present invention have conducted intensive studies with the aim of obtaining the products of interest stably for a prolonged period of time by avoiding the concentration

of heat of reaction generated on the catalyst, and found as a result of the efforts that the aforementioned object can be achieved when a plurality of supported catalysts having different activities, which are prepared by controlling the amount of a powder that contains catalytically active components to be supported (coated) on an inert carrier and calcining temperature and calcining time of the catalysts, are used by arranging them in a specified manner.
In this connection, the term "activity" as used herein means reactivity of propylene and has the same meaning as conversion ratio.
Accordingly, the present invention relates to: (1) a method for producing acrolein and acrylic acid by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed bed multitubular reactor, which comprises
a) using a plurality of supported catalysts having different activities, which carry a powder that contains catalytically active components having a composition represented by the folowing formula
Mo^B^Ni^COdFe^YgZhO, (wherein Mo, Bi, Ni, Co and Fe represent molybdenum, bismuth, nickel, cobalt and iron, respectively, Y is at least one element selected from the group of tin, zinc, tungsten, chromium, manganese, magnesium, antimony and titanium, Z is at least one element selected from the group of potassium, rubidium, thallium and cesium, and a, b, c, d, f, g, h and x represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, Y, Z and oxygen, respectively, a = 12,b = 0.1 to 7, c + d = 0.6 to 20, f = 0.5 to 8, g = 0 to 2, h = 0 to 1 and

X is determined by the oxidized condition of each element),
b) setting a catalyst layer in a reaction tube, which is formed by dividing it into plural portions in the tube axial direction, and
c) arranging the aforementioned plural supported catalysts in such order that the activity becomes high toward the outlet from the inlet of the material gas in the reaction tube axial direction,

(2) the method according to the above item (1) wherein the catalysts are used whose activity strength is controlled by means of the supported amount of the powder that contains catalytically active components, when it is supported on a carrier, and/or the calcining treatment of the powder that contains catalytically active components after it is supported on the carrier,
(3) the method according to the above item (1) or (2) wherein the plural catalysts to be used have the same composition of catalytically active components,
(4) the method according to any one of the above items (1) to (3) wherein the carrier of the plural catalysts to be used is the same, {5) the method according to any one of the above items (1) to (4) wherein the powder that contains catalytically active components further contains a molding additive and/or a strength improving agent, and
(6) the method according to any one of the above items (1) to (5) wherein it uses a catalyst in which particle size of the catalyst is 3.5 to 16 mm, the amount of the catalytically active component-containing powder to be supported on the carrier is 10 to 60% by weight (catalytically active components/(catalytically

active components + carrier + strength improving agent (optional
component)), and the calcining temperature of the catalytically
active component-containing powder after it is supported is 450 to
650°C.
[Detailed Description of the Invention]
The following describes the present invention in detail.

The catalyst to be used in the present invention can be obtained
by a method in which a powder that contains catalytically active
components having a composition of the following formula is supported v
on a carrier and then calcined. J/iO h LoV *■■
1 V^ r
Mo,Bi,Ni,Co,Fe,Y,ZhO,

(In this formula. Mo, Bi, Ni, Co and Fe represent molybdenum, bismuth,^Xy
4
nickel, cobalt and iron, respectively, Y is at least one element ^/^ selected from the group of tin, zinc, tungsten, chromium, manganese, magnesium, antimony and titanium, Z is at least one element selected from the group of potassium, rubidium, thallium and cesium, and a, b, c, d, f, g, h and x represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron, Y, Z and oxygen, a = 12, b = 0.1 to 7, c+d=0.5to20, f=0.5to8, g=0to2, h=Otol and x is determined by the oxidized condition of each element.) In the above definition, it is desirable that a = 12, b = 0.5to4, c + d=lto 12, f = 0.5to5, g = Otol and h = 0.01tb0.5. The powder containing catalytically active components is prepared by a coprecipitation, spray drying or the like means, using nitrate, ammonium salt, hydroxide, oxide, acetate and the like salts of respective metal elements as the starting materials with no particular limitation.

The powder containing catalytically active components is usually subjected to preliminary calcination at a temperature of from 200 to 600°C for from 2 to 24 hours prior to its supporting on a carrier. The preliminary calcination is carried out preferably in the atmosphere of air or in a stream of nitrogen. The thus obtained powder by the preliminary calcination is called preliminarily calcined powder hereinafter. In addition, in a plurality of catalysts having different activities, compositions of the catalytically active components of these catalysts (preliminarily calcined powder) may be the same or different from one another, but preferably the same.
When the preliminarily calcined powder described above is supported on a carrier, it is desirable to mix it with a molding additive and/or a strength improving agent. Illustrative examples of the molding additive include crystalline cellulose, starch, stearic acid and the like, and those of the strength improving agent include ceramic fibers, carbon fibers, whiskers and the like. The molding additive or strength improving agent is used in an amount of 30% by weight or less based on the preliminarily calcined powder. The molding additive and/or strength improving agent may be mixed in advance with the aforementioned preliminarily calcined powder prior to molding or, as will be described later, may be added to a molding machine simultaneously with or before or after the addition of the preliminarily calcined powder and the like.
The carrier can be made into spherical, cylindrical, tublar and the like shapes with no specific limitation, but a spherical shape is particularly desirable when production efficiency and mechanical

strength of the catalyst are taken into consideration. Also, it is desirable to use a binder when the preliminarily calcined powder is supported on the carrier. Illustrative examples of the binder include water, an alcohol, a polyhydric alcohol such as glycerol or the like or a mixture thereof. The binder is used in an amount of from 10 to 60% by weight based on the preliminarily calcined powder.
Any material can be used as the carrier as long as it is inert and porous or can be made into porous granules, and its examples include a-alumina, silicon carbide, pumice, silica, zirconium oxide, titanium oxide and the like. The carrier may have a particle size of preferably from 3 to 12 mm. Types of the carrier for a plurality of catalysts may be the same or different from one another, but they may preferably be the same.
The powder that contains the catalytically active components (the powder containing preliminarily calcined powder, if necessary further containing a molding additive and/or a strength improving agent, to be referred to as catalytically active component-containing powder hereinafter) can be supported on the carrier by any method such as a tumbling granulation method, a method using a centrifugal f luidized bed coating apparatus and a wash coating method, with no particular limitation, but the tumbling granulation method is desirable when catalyst production efficiency and the like are taken into consideration. Illustratively, this is a method in which a fixed cylindrical container whose bottom part is equipped with a disc having even or irregular surface is used, and a carrier charged in the container is vigorously mixed through the repetition of

rotation and revolution effected by high speed spinning of the disc, to which the catalytically active component-containing powder and, if necessary, a binder are added so that said powder is supported on the carrier.
According to the present invention, a plurality of catalysts
having different activities are used which are obtained by calcining a powder that contains the aforementioned active components and is supported on a carrier. The catalysts whose activity is controlled by means of the supported amount of the catalytically active components in the catalytically active component-containing powder and/or the calcination temperature and calcination time of the catalytically active component-containing powder after supporting it on a carrier, are used in a certain arrangement in a specified combination. That is, a plurality of reaction zones are provided in the catalyst layer, and the supported catalysts having different activities are arranged in respective reaction zones in such a manner that the activity becomes high toward the outlet from the inlet of the starting material gas in the reaction tube axial direction.
The activities of the catalysts are controlled by the amount of the catalytically active components to be supported and the activity becomes high as the supported amount increases. The supported amount is preferably from 5 to 80% by weight, more preferably from 10 to 60% by weight.
In this connection, the supported amount is represented by "weight of catalytically active components/(weight of catalytically active components + weight of carrier + weight of strength improving

agent (optional component)", and is referred to as catalyst supported ratio hereinafter. The term "weight of catalytically active components" as used herein means weight of the preliminarily calcined powder.
According to the present invention, the activity of catalyst is also controlled by calcination temperature and the activity becomes high as the calcination temperature is reduced. The calcination temperature is preferably from 450 to 650°C, more preferably from 480 to 600°C.
The calcination time is generally from 3 to 30 hours, preferably from 4 to 15 hours. Within this range of calcination time, the catalyst activity becomes high as the baking time is shortened.
The preferred combination of calcination temperature and time is varied depending on the supported amount of catalytically active components. For example, when the catalyst layer is divided into two parts a catalyst prepared by calcination at 500-650°C for 4-15 hours is preferably combined with a catalyst prepared by calcination at 450-550°C for 4-10 hours while the catalyst layer is divided into three parts a catalyst prepared by calcination at 500-650°C for 4-15 hours is preferably combined with a catalyst prepared by calcination at 500-580°C for 4-15 hours and a catalyst prepared by calcination at 450-550°C for 4-10 hours.
The catalyst activity is decreased as the particle size of catalyst is increased if the catalyst supports catalytically active components having the same composition.
The particle size of catalyst is determined by the particle

size of carrier and the carrier supported ratio, and it is preferably determined by taking inner diameter of the reaction tube and the like into consideration. In the case of the catalysts to be used in the present invention in which the same carrier is used for a plurality of catalysts having different activities, particle size of the catalysts becomes slightly large as the amounts to be supported increase, when the catalytically active components are supported on the carrier under the same conditions, but is almost the same as long as the supported amounts are not changed greatly. The particle size of catalyst is usually 3.5 to 16 mm.
According to the present invention, a fixed bed multitubular reactor is used as the reactor, and the number of reaction tubes, the packing length of the catalyst, the number of divided portions of catalyst layer and the like vary depending on the operation conditions, so that these factors may be decided in each case in such a manner that optimum operation results are obtained. With regard to the division of catalyst layer, prevention of the generation of hot spots or heat accumulation in the hot spot becomes easy as the number of divided portions increases, but the object can be achieved practically by dividing it into 2 to 3 portions.
Inner diameter of the reaction tube is generally from about 15 to 50 mm. For example, when the inner diameter of reaction tube is 21 to 27 mm in that case, it is desirable to use a combination of catalysts having a particle size of 3.5 to 8 mm whose activities are controlled by adjusting the supported amount in the catalysts to 15 to 60% by weight, and the calcination temperature to 480 to

580°C.
The production method of the present invention may be applied to a once-through (one-pass) operation method or a recycling method, and can be carried out under conditions generally used on them. For example, the reaction may be carried out by introducing a mixture gas consisting of 1 to 10% by volume, preferably 4 to 9% by volume, of propylene as the starting material, 3 to 20% by volume, preferably 4 to 18% by volume, of molecular oxygen, 0 to 60% by volume, preferably 4 to 50% by volume, of water vapor and 20 to 80% by volume, preferably 30 to 60% by voliame, of an inert gas (nitrogen, carbon dioxide or the like) onto the aforementioned catalysts at a temperature of 250 to 450°C, under a pressure of atmospheric pressure to 10 atm and at a space velocity ( = material gas flow volume/apparent volume of packed catalysts) of 300 to 5,000 hr"^ [Effects of the Invention]
According to the present invention, run away reaction caused by the generation of hot spot and over oxidation reaction can be avoided and constant operation can be made for a prolonged period of time without employing industrially disadvantageous methods, even under high load reaction conditions in which concentration of the starting material is increased and/or the space velocity is increased, so that the method of the present invention is an outstandingly superior method in comparison with the prior art methods.
When the reaction is carried out according to the present invention by supporting a catalytically active component-containing

powder on a carrier, calcining the resultant and then packing a plurality of the thus obtained catalysts having different activities in each of a plurality of reaction zones arranged in the reaction tube axial direction in such order that the catalyst with lower activity is placed from the inlet of the starting material, the danger of causing runaway reaction due to the generation of hot spots or heat accumulation at the hot spot can be avoided and formation of by-products due to over oxidation reaction can be prevented, even under high load reaction conditions, so that the intended acrolein and acrylic acid can be obtained with high selectivity and high yield. The productivity can also be improved markedly, because deterioration of the catalyst due to locally exceeded thermal load can be prevented and the catalyst therefore can be used stably for a prolonged period of time.
Thus, the production method of the present invention is a markedly useful method for the production of acrolein and acrylic acid. [Examples]
The present invention is described further illustratively with reference to the following examples.
The conversion ratio, the selectivity and the yield per pass in the present invention are defined as follows.
Propylene conversion ratio (mol %) = (mol number of reacted propylene)/(mol number of supplied propylene) x 100
Total selectivity (mol %) = (mol number of formed acrolein and acrylic acid)/(mol number of reacted propylene) x 100

Yield (mol %) = (mol number of formed acrolein or acrylic acid)/(mol number of supplied propylene) x 100 Example 1 (Preparation of catalyst - 1)
An aqueous solution (A) was obtained by dissolving 423.8 g of ammonium molybdate and 2.02 g of potassium nitrate in 3,000 ml of distilled water which was heated and stirred.
Separately from this, an aqueous solution (B) was prepared by dissolving 302.7 g of cobalt nitrate, 162.9 g of nickel nitrate and 145.4 g of ferric nitrate in 1,000 ml of distilled water, and an aqueous solution (C) by dissolving 164.9 g of bismuth nitrate in 200 ml of distilled water which had been acidified by adding 25 ml of concentrated nitric acid. The aqueous solutions (B) and (C) were mixed, and the mixture solution was added dropwise to the aqueous solution (A) which was vigorously stirred.
The thus formed suspension was dried using a spray dryer and subjected to 3 hours of preliminary calcination at 440°C, thereby obtaining 570 g of preliminarily calcined powder. Thereafter, 200 g of the preliminarily calcined powder was mixed with 10 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and the crystalline cellulose was obtained.
A 300 g portion of alumina carrier having an average particle size of 3.5 mm was put into a tumbling granulator and then the just described mixture and 90 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of

the mixture on the carrier, thereby obtaining particles having a supported ratio of 40% by weight (to be referred to as active component-supported particles hereinafter).
The active component-supported particles were dried at room temperature for 15 hours and then calcined at 560°C for 5 hours in the flow of air to obtain a catalyst (1). The catalyst (1) was found to have an average particle size of 4.0 mm, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi=1.7, Ni=2.8, Fe=1.8, Co =5.2 and K = 0.1 in atomic ratio. (Preparation of catalyst - 2)
A 300 g portion of the preliminarily baked powder obtained in Preparation of catalyst - 1 was mixed with 15 g of crystalline cellulose as a molding additive, and thus obtained a mixture of the preliminarily clcined powder and the crystalline cellulose was obtained.
A 300 g portion of alumina carrier having an average particle size of 3.5 mm was put into a tumbling granulator and then the above-mentioned mixture and 135 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 50% by weight.
The thus obtained active component-supported particles were dried at room temperature for 15 hours and then calcined at 520°C for 5 hours in the flow of air to obtain a catalyst (2). The catalyst (2) was found to have an average particle size of 4.1 mm, and the composition of its catalytically active components, excluding oxygen,

was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Oxidation reaction)
The aforementioned catalysts (1) and (2) were packed in a reaction tube of 21 mm in inner diameter and 5 m in length made of stainless steel (SUS 304) and equipped with a thermocouple, in respective packed layer lengths of 105 cm and 295 cm at central area of the reaction tube starting from the starting material gas inlet toward the outlet. While keeping the reaction bath temperature at 337°C and the catalyst layer inlet pressure at 1.53 kg/cm^ G, the reaction was carried out by passing a mixture gas consisting of 8% by volume of propylene, 14% by volume of oxygen, 25% by volume of water vapor and 53% by volume of nitrogen through the tube at a space velocity of 1,860 hr'^. In this case, maximum temperatures of the catalyst layers starting from the inlet were 388°C and 400°C, respectively, the propylene conversion ratio was 97.1%, the acrolein yield was 80.9%, the acrylic acid yield was 8.1% and the total selectivity for acrolein and acrylic acid was 91.7%, and decrease in reaction performance was not observed even after continuation of the reaction for 1,000 hours or more. Example 2 (Preparation of catalyst - 3)
A catalyst (3) was obtained in the same manner as described in Preparation of catalyst - 1, except that the calcining temperature was changed to 540°C. The catalyst (3) was found to have an average particle size of 4.0 ram, and the composition of its catalytically

active components, excluding oxygen, was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Oxidation reaction)
The aforementioned catalysts (3) and (2) were packed in a reaction tube of 21 mm in inner diameter and 5 m in length made of stainless steel (SUS 304) and equipped with a thermocouple, in respective packed layer lengths of 105 cm and 295 cm starting from the starting material gas inlet toward the outlet. While keeping the reaction bath temperature at 333°C and the catalyst layer inlet pressure at 1.17 kg/cm^ G, the reaction was carried out by passing a mixture gas consisting of 8% by volume of propylene, 14% by volume of oxygen, 25% by volume of water vapor and 53% by volume of nitrogen through the tube at a space velocity of 1,550 hr"^. In this case, maximum temperatures of the catalyst layers starting from the inlet were 401°C and 373°C, respectively, the propylene conversion ratio was 98.1%, the acrolein yield was 81.3%, the acrylic acid yield was 8.6% and the total selectivity for acrolein and acrylic acid was 91.6%, and decrease in reaction performance was not observed even after continuation of the reaction for 1,000 hours or more. Example 3 (Preparation of catalyst - 4)
A 100 g portion of the preliminarily calcined powder obtained in Preparation of catalyst - 1 was mixed with 5 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and the crystalline cellulose was obtained.

A 300 g portion of alumina carrier having an average particle size of 4 mm was put into a tumbling granulator and then the just described mixture and 45 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 25% by weight.
The thus obtained active component-supported particles were dried at room temperature for 15 hours and then calcined at 520°C for 5 hours in the flow of air to obtain a catalyst (4 ). The catalyst (4) was found to have an average particle size of 4.3 mm, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Preparation of catalyst - 5)
A 150 g portion of the preliminarily calcined powder obtained in Preparation of catalyst - 1 was mixed with 7.5 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and the crystalline cellulose was obtained.
A 300 g portion of alumina carrier having an average particle size of 4 mm was put into a tumbling granulator and then the described mixture and 70 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 33% by weight.
The thus obtained active component-supported particles were

dried at room temperature for 15 hours and then calcined at 520°C for 5 hours in the flow of air to obtain a catalyst (5). The catalyst
(5) was found to have an average particle size of 4.5 ram, and the
composition of its catalytically active components, excluding oxygen,
was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in
atomic ratio.
(Preparation of catalyst - 6)
A 200 g portion of the preliminarily calcined powder obtained in Preparation of catalyst - 1 was mixed with 10 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and crystalline cellulose was obtained.
A 300 g portion of alumina carrier having an average particle size of 4 mm was put into a tumbling granulator and then the described mixture and 90 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 40% by weight.
The thus obtained active component-supported particles were dried at room temperature for 15 hours and then calcined at 520°C for 5 hours in the flow of air to obtain a catalyst (6). The catalyst
(6) was found to have an average particle size of 4.5 ram, and the
composition of its catalytically active components, excluding oxygen,
was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in
atomic ratio.
(Oxidation reaction)

The aforementioned catalysts {4), {5) and (6) were packed in a reaction tube of 27 mm in inner diameter and 5 m in length made of stainless steel (SUS 304) and equipped with a thermocouple, in respective packed layer lengths of 100 cm, 100 cm and 150 cm starting from the starting material gas inlet toward the outlet. While keeping the reaction bath temperature at 334°C and the catalyst layer inlet pressure at 1.35 kg/cm^ G, the reaction was carried out by passing a mixture gas consisting of 7% by volume of propylene, 13% by volume of oxygen, 10% by volume of water vapor and 70% by volume of nitrogen through the tube at a space velocity of 1,800 hr"^. In this case, maximum temperatures of the catalyst layers starting from the inlet were 404°C, 385°C and 352°C, respectively, the propylene conversion ratio was 96.6%, the acrolein yield was 84 .2%, the acrylic acid yield was 6.2% and the total selectivity for acrolein and acrylic acid was 93.6%, and decrease in reaction performance was not observed even after continuation of the reaction for 1,000 hours or more. Example 4
The reaction was carried out in the same manner as described in Example 3, except that the space velocity was changed to 1,500 hr"\ the reaction bath temperature to 332°C and the catalyst layer inlet pressure to 1.1 kg/cm^ G. In this case, maximum temperatures of the catalyst layers were 398°C, 381°C and 350°C, respectively, the propylene conversion ratio was 96.4%, the acrolein yield was 84.3%, the acrylic acid yield was 6.0% and the total selectivity for acrolein and acrylic acid was 93.6%, and decrease in the reaction results was not observed even after continuation of the reaction for 1,000 hours

or more.
Example 5
(Preparation of catalyst - 7)
A 200 g portion of the preliminarily calcined powder obtained in Preparation of catalyst - 1 was mixed with 10 g of crystalline cellulose as a molding additive, and thus a mixture of the preliminarily calcined powder and the crystalline cellulose was obtained.
A 300 g portion of alumina carrier having an average particle size of 4 mm was put into a tumbling granulator and then the described mixture and 90 g of 33% by weight glycerol aqueous solution as a binder were simultaneously added thereto to effect support of the mixture on the carrier, thereby obtaining particles having a supported ratio of 40% by weight.
The thus obtained active component-supported particles were dried at room temperature for 15 hours and then calcined at 550°C for 5 hours in the flow of air to obtain a catalyst (7 ). The catalyst (7) was found to have an average particle size of 4.5 mm, and the composition of its catalytically active components, excluding oxygen, was Mo = 12, Bi = 1.7, Ni = 2.8, Fe = 1.8, Co = 5.2 and K = 0.1 in atomic ratio. (Oxidation reaction)
The aforementioned catalysts (7) and (6) were packed in a reaction tube of 21 mm in inner diameter and 5 m in length made of stainless steel (SUS 304) and equipped with a thermocouple, in respective packed layer lengths of 105 cm and 295 cm starting from

the starting material gas inlet toward the outlet. While keeping the reaction bath temperature at 339°C and the catalyst layer inlet pressure at 1.81 kg/cm^ G, the reaction was carried out by passing a mixture gas consisting of 8% by volume of propylene, 14% by volume of oxygen, 25% by volume of water vapor and 53% by volume of nitrogen through the tube at a space velocity of 1,860 hr'^. In this case, maximum temperatures of the catalyst layers starting from the inlet were 406°C and 397°C, respectively, the propylene conversion ratio was 97.4%, the acrolein yield was 79.9%, the acrylic acid yield was 8.9% and the total selectivity for acrolein and acrylic acid was 91.2%, and decrease in reaction performance was not observed even after continuation of the reaction for 1,000 hours or more.

WE CLAIM:
1. A method for producing acrolein by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a fixed bed multitubular reactor which comprises a) using a plurality catalysts differing the activities in the amount of the catalytically active component supported on the carrier and the higher catalytic activity being displayed by the carriers supporting the larger amount of the catalytically active component and the catalytically active components having a composition represented by the following formula wherein Mo, Bi, Ni, Co and Fe represent molybdenum, bismuth, nickel, cobalt and iron, respectively, Y is at least one element selected from the group of tin, zinc, tungsten, chromium, manganese, magnesium, antimony and titanium, Z is at least one element selected from the group of potassium, rubidium, thallium and cesium, and a, b, c, d, f, g, h and x represent the number of atoms of molybdenum, bismuth, nickel, cobalt, iron respectively, Y, Z and oxygen, a = 12, b = 0.1 to 7, c + d =0.5 to 20, f = 0.5 to 8, g = 0 to 2, h = 0 to 1 and X is determined by the oxidized condition of each element, b) setting a catalyst layer in a reaction tube, which is formed by dividing it into plural portions in the tube axial direction, and c) arranging the aforementioned plural supported catalysts in such a manner that the activity becomes high toward the outlet from the inlet of the maternal gas in the reaction tube axial direction.

2. The method as claimed in claim 1, wherein the catalysts are used
whose activity is controlled by means of by the supported amount of the
powder that contains catalytically active components, when it is supported
on a carrier, and/or the calcinations treatment of the powder that contains
catalytically active components after it is supported on the carrier.
3. The method as claimed in claim 1 or 2, wherein the plurality catalysts
to be used have the same composition of catalytically active components.
4. The method as claimed in any one of claims 1 to 3, wherein the carrier
of the plural catalysts to be used is the same.
5. The method as claimed in any one of claims 1 to 4, wherein the
powder that contains catalytically components contains a molding additives
and/or a strength improving agent.
6. A method for producing acrolein substantially as herein described and
exemplified.

Documents:

2756-mas-1997 abstract-duplicate.pdf

2756-mas-1997 abstract.pdf

2756-mas-1997 claims-duplicate.pdf

2756-mas-1997 claims.pdf

2756-mas-1997 correspondence-others.pdf

2756-mas-1997 correspondence-po.pdf

2756-mas-1997 description(complete)-duplicate.pdf

2756-mas-1997 description(complete).pdf

2756-mas-1997 form-1.pdf

2756-mas-1997 form-19.pdf

2756-mas-1997 form-26.pdf

2756-mas-1997 form-4.pdf

2756-mas-1997 form-6.pdf

2756-mas-1997 others.pdf

2756-mas-1997 petition.pdf

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Patent Number

200394

Indian Patent Application Number

2756/MAS/1997

PG Journal Number

08/2007

Publication Date

23-Feb-2007

Grant Date

15-May-2006

Date of Filing

02-Dec-1997

Name of Patentee

NIPPON KAYAKU KABUSHIKI KAISHA

Applicant Address

11-2 FUJIMI 1-CHOME, CHIYODA-KU, TOKYO,

Inventors:

#	Inventor's Name	Inventor's Address
1	KOICHI WADA	2-14-2, SOYAGI, YAMATO-SHI, KANAGAWA-KEN,
2	YOSHIMASA SEO	2959-1, OOAZA-KOORI, SANYO-CHO, ASA-GUN, YAMAGUCHI-KEN
3	AKIRA IWAMOTO	187-11, OOAZA-KIWANAMI, UBE-SHI, YAMAGUCHI-KEN,
4	ATSUSHI SUDO	340-4 HARAICHI, ANNAKA-SHI, GUNMA-KEN
5	FUMIO SAKAI	HODOTA, GUNMA-MACHI, GUNMA-KEN
6	KAZUO SHIRAISHI	208 DHYA, ANNAKA-SHI, GUNMA-KEN
7	HIROYOSHI NOWATARI	762-31, KURAGANO-MACHI, TAKASAKI-SHI, GUNMA-KEN

PCT International Classification Number

C07C27/14

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	336298/96	1996-12-03	Japan