Title of Invention

"A PROCESS FOR PRODUCTION OF LINEAR ALKYL BENZENES"

Abstract

This invention relates to a process for the production of linear alkyl benzenes. More specifically it refers to an integrated process in which benzene is alkylated with the products obtained by the oxidation of linear paraffins. A process for production of linear alkyl benzenes comprising the steps of reacting linear paraffin with an oxygen containing gas in the presence of a solid catalyst containing an organotransition metal complex selected from pthalocyanin or porphyrin wherein some or all of the hydrogen atoms of the solid organ transition metal complex encapsulated in solid matrix have been substituted by one or more electron withdrawing groups in presence of solvent at a temperature in the range of 20°C to 100°C and a pressure in the range of 5 to 1000 psi to obtain alcohol

Full Text

This invention relates to an integrated process for the production of linear alkyl benzenes. More specifically it refers to an integrated process in which benzene is alkylated with the products obtained by the oxidation of linear paraffins. Detergents are important household consumables and contain synthetic surfactants as the active ingredients. Linear alkyl benzene sulfonates have been the the surfactants of choice for the past two decades as they are cost effective and biodegradable. Conventionally, they are obtained by the sulfonation of Linear Alkyl Benzenes, hereinafter designated as LAB, which are produced by the catalytic alkylation of benzene with linear olefins with carbon numbers, usually from 10 to 14. The linear olefins themselves are produced by the dehydrogenation of n-alkanes obtained from kerosene range fractions via separation using molecular sieves. The alkylation of benzene with olefins is generally carried out at present in the industry using HF or A1C13 as the catalysts, the former catalyst being the more in vogue. U.S. Pat. Nos. 3,494,970 and 3,830,865 describe a process for the production of LAB using HF catalysts. U.S. Pat.Nos. 3,631,123, 3,674,885 and 3,703,559 describe the use of Lewis acid catalysts such as A1C13 in the production of LAB. In addition to the use of the above liquid phase acid catalysts, solid acid catalysts such as clays and zeolites have also been used in the production of LAB. U.S. Pat.No. 4,046,826 uses a natural or synthetic trioctahedral clay of the hectorite type ion exchanged with metallic cations for the alkylation of benzene with heavy olefins, basically 1-dodecene. U.S. Pat.No. 4,070,407 assigned to Mobil Oil Co. describes the use of a crystalline aluminium silicate zeolite as a catalyst for the alkylation of benzene with olefins, alcohols and alkyl halides to produce alkyl benzenes. European Patent application Eu 0,353,813 Al describes a process for the alkylation of benzene with C2-C20 mono olefins in the presence of an aluminium - magnesium silicate catalyst. Our earlier U.S. Pat. 5,453,553 discloses a process for the production of linear alkyl benzenes using a transition metal containing zeolites in the presence of molecular hydrogen, the added hydrogen enabling substantially long cycle lengths between two successive regenerations. In present commercial practice, the normal olefins used in the alkylation of benzene are produced mainly by the dehydrogenation of the normal alkanes at high temperatures over supported metal catalysts containing principally platinum as the metal component. A typical dehydrogenation process is the Pacol process offered by Universal Oil Products, USA and described by B. Vora, P. Pijado, T. Imai and T. Fritsch in Chemistry and Industry issue of 19 March 1990, pages 187 to 191. The disadvantages of such dehydrogenation reactions are manifold. For example, temperatures as high as 450-500°C are necessary to obtain reasonable olefin production, such high temperatures leading to faster catalyst deactivation and limiting the cycle length of the catalyst. In fact, the typical cycle length of the catalyst used in the Pacol process is 3-4 weeks. Even at such high temperatures, the amount of olefins produced is limited, the olefin content of the product being only about 10-13%, the rest being unreacted paraffins. More importantly, the high temperatures used also lead to the production of substantial amounts of diolefinic material which oligomerize into heavy polymeric material or large molecular weight diphenyl alkanes during the subsequent alkylation reaction to produce the linear alkyl benzenes. The diolefins also transform into undesirable cyclic components such as alkyl indanes and alkyl tetralenes in the presence of the alkylation catalysts. These undesirable components decrease the biodegradibility of the final detergent. The formation of diolefinic materials during the dehydrogenation reduces the overall yield of LAB, due to the formation of heavy polymeric materials called tar polymers and diphenyl alkanes, called heavy alkyl benzenes in the alkylation reactor. It is therefore essential to remove the diolefins in the olefin feed to improve the yield of and quality of the LAB produced. This is at present carried out in some commercial units by partial or selective hydrogenation of the diolefins using a metal catalyst with molecular hydrogen in another reactor. For example, a selective hydrogenation process called the DeFine process to selectively hydrogenate the diole- fins impurities present in the paraffin mixture coming out from the Pacol reactor is described by B. Vora, P. Pujado, T. Imai and T. Fritsch in "Chemistry and Industry" issue of 19th March, 1990, pages 187 to 191. The introduction of an additional processing step, namely, the selective hydrogenation of the diolefins results in escalation of investment and production costs. Other disadvantages of the high temperatures used in the dehydrogenation reaction are the formation of non-normal olefins and alkanes due to isomerization and undesirable aromatics by cycli-zation. The presence of non-normal alkenes and aromatic compounds lowers the biodegradabili-ty of the LAB besides affecting detergency. Many of the problems associated with the dehydrogenation of paraffins to obtain olefins described earlier can be mitigated to a large extent by the use of long chain alcohols as the source of olefins. However, alcohols are expensive to manufacture and the direct oxidation of long chain alkanes to alcohols is not commercially practiced to any significant extent. The usual oxidants such as permanganates and chromic acid do not convert the alkanes to alcohols. More expensive oxidants such as organic peroxides and hydrogen peroxide are known to oxidize alkanes to alcohols with poor yields, especially in the presence of expensive metal complexes and transition metal molecular sieves. A typical example of such a method of producing alcohols from paraffin in the oxidation of n-hexane with aqueous hydrogen peroxide in the presence of the titanosilicate, TS-1 is described by D.R.C. Huybrechts, L. De Bruycker and P.A. Jacobs in Nature; Vol. 345; year 1990; pages 240 to 242. Commercially, primary alcohols are produced by the oligomerization of ethylene followed by the oxidation and hydrolysis by the Ziegler process or by methanolysis of natural oils or fats followed by hydrogenation. Long chain alcohols are also made from olefins and synthesis gas via hydroformylation processes. In these processes, transition metal complexes of cobalt or rhodium serve as catalysts in the liquid phase in forming an aldehyde or an alcohol having one or more carbon atom than the olefin feed. The aldehyde formed is later converted into the corresponding alcohol by hydrogenation. The hydroformylation reaction between the olefin and the syngas is conducted in the range of 100 to 300°C and at pressures upto 300 bars. An elegant method of synthesis of long chain alcohols using a source of molecular oxygen such as air has been described in our copending Indian application, which refers to a process for the oxidation of paraffin to linear alcohols which comprises reacting the paraffin with molecular oxygen in the presence of a solid catalyst containing an organotransition metal complex containing electron withdrawing groups in the temperature range of 20°C to 100°C at a pressure in the range of 5 to 1000 psi. The transformation of alcohols to olefins is extensively described in the literature and is well known in the present art. Acidic solid catalysts such as alumina, silica-alumina and ion-exchange resins besides liquid catalysts such as concentrated sulfuric acid can be used to dehydrate alcohols to olefins. A simpler and more economical procedure is the direct use of alcohols as alkylation agents in the manufacture of alkyl benzenes. Such alkylations are again well known and occur over many solid acids such as zeolites, clays and amorphous oxides such as alumina and silica-alumina. In the present day art, liquid phase acid catalysts such as HF and A1C13 are mostly used in the alkylation of benzene with olefins. One limitation of these catalysts is the corrosive nature of these acids leading to laborious and costly procedures and equipment for their handling. A second limitation is the presence of environmental hazards during the handling and disposal of the spent catalysts. A third limitation is the toxicity, especially that of HF to the plant personnel in case of leaks due to accidents or plant upsets. The above disadvantages due to the use of HF have been overcome by the development of solid catalysts. Two such typical catalysts are disclosed by the Patent application Eu 0,353,813 Al assigned to Petresa and out recent U.S.Pat. No. 5,453,553. U.S.Pat. No. 5,453,553 reveals that the presence of molecular hydrogen during the alkylation reaction prolongs the solid catalyst life by reducing the deactivation rate. In view of the many disadvantageous features of the existing processes for the production of LAB, it was the objective of the work leading to the present invention to discover a novel integrated process for the manufacture of LAB by the alkylation of benzene with olefins derived from the alcohols prepared and described in our copending patent application or directly with the alcohols prepared as above using a solid acid catalyst without recourse to the use of environmentally unsafe HF or AICl3. Another objective of the present invention is to avoid the formation of non-normal alkyl benzenes with extraneous undesirable aromatics such as alkyl naphthalene, alkyl tetralins and alkyl indanes which lower the biodegradability of LAB. The above objective is readily realized if the alkylating agent namely, the olefin is obtained at temperatures much below the 450°-500 used at present in the industry. Besides, the use of other alkylation's agents such as alcohols prepared by oxidation of paraffin's at temperatures below 100° also achieve the same objective. Another objective of the present invention is to maximize the yield of linear alkyl benzenes amongst the homogenous. This objective is also realized if the paraffins are not transformed into diolefinie material which takes place at the high temperatures used at present during the dehydrogenation of the linear alkanes. Accordingly the present invention provides a process for production of linear alkyl benzenes comprising the steps of a) reacting linear paraffin with an oxygen containing gas in the presence of a solid catalyst containing an organ transition metal complex selected from pthalocyarin or porphyrin wherein same or all of the hydrogen atoms of the solid organotransition metal complex have been substituted by one or more electron withdrawing groups in presence of solvent at a temperature in the range of 20°C to 100°Cand a pressure in the range of 5 to 1000 psi to obtain alcohol b) reacting the alcohol with a mixture of benzene and molecular hydrogen in the presence of an alkylation catalyst containing acid at a temperature in the range of 25 to 200°C and separating the linear alkyl benzenes from the reaction mixture by conventional methods. It has now been found in accordance with the present invention that long chain paraffins can be converted into linear alkyl benzenes (LAB) by an integrated process which consists of the steps of conversion of the long chain paraffins into alcohols by reaction with molecular oxygen in the presence of a solid catalyst containing an organotransition metal complex in a first reaction zone and alkylation of the resulting linear alcohols or their dehydration product, the linear olefins with benzene using an alkylation catalyst in a second reaction zone to linear alkyl benzene. In one embodiment of the present invention, the alcohols produced by the oxidation of alkanes can be converted into olefins by dehydration over an acidic catalyst and the olefins used to alkylate benzene using solid acid catalysts or using conventional alkylating agents such as HF or AICI3. In another embodiment of the present invention, the oxidation of the long chain paraffins is carried out in the presence of a solid catalyst containing an organotransition metal complex containing electron withdrawing groups selected from the halogens, fluorine, chlorine, bromine or iodine or the nitro or cyano groups. The transition metal component of the complex is selected from iron, cobalt, copper, chromium, manganese or mixtures thereof. Some non limiting examples of such organotransition metal complex used in such oxidation reactions are the halo phthalocyanins or prophyrins of copper, cobalt, chromium, manganese and iron. One feature of the present invention is that it is not necessary to separate the alcohols from the unreacted paraffins or the solvent if any used during the oxidation. Only the solid catalyst is separated and the entire reaction product is mixed with benzene in the desired proportions and contacted with the alkylation catalyst for conversion into alkyl benzenes. The unreacted paraffins and the solvent remain inert during the alkvlation reaction. Another feature of the present invention is the use of solid acid catalysts such as amorphous silica-alumina clays or zeolites for the alkylation of benzene with the alcohols in the second reaction zone. The clays used could be acidic clays such as montmorillonite, vermiculites, hec-torites or sepiolite or similar well known materials. The zeolites used may be chosen from the Group X, Y, modernite, ZSM-12, or beta. These zeolites have been described by R. Szostak in Handbook of Molecular Sieves published by Van Nostrand Reinhold, New York, 1992. Another feature of the present invention is that the alkylation reaction is conducted in the presence of added molecular hydrogen to prolong the life of the solid acid catalyst. An advantageous feature of the presence of hydrogen during the alkylation reaction is the hydrogenation of the trace quantities of aldehydes and ketones, if any, present in the oxidation product into alcohols, thereby increasing the overall selectivity of the process with respect to the long chain paraffins. In one embodiment of the process of the present invention, the oxidation of linear alkanes is carried with oxygen or air or oxygen diluted with an inert gas such as nitrogen or argon. Our copending Indian Patent Application describes in more detail the process for the oxidation of linear alkanes to linear alcohols. In another embodiment, the oxidation of the linear alkanes is carried out in the presence of solvents such as acetonitrile, methanol, water or butanol or any solvent which remains inert during the above reaction. In yet another embodiment, the organotransition metal complex catalyst may be encapsulated in a solid matrix to enhance the dispersion and thereby the effectiveness of the catalyst. Examples of such solid matrices include inorganic oxides like silica, alumina, molecular sieves, zeolites as well as organic polymeric materials like polystyrene. In yet another embodiment, the rates of the oxidation reaction are enhanced by the addition of very small catalytic quantities of a promoter. Examples of such promoters include organic peroxides such as alkyl hydroperoxide, dialkylperoxides and such compounds. In one more embodiment, small quantities of aldehydes or ketones produced in the first reaction zone along with the alcohols are hydrogenated with hydrogen in the presence of a transition metal present in the alkylation catalyst in the second reaction zone. U.S. Pat. 5,453,553 describes an alkylation catalyst possessing such characteristics. According to another embodiment, the solid acids used in the alkylation namely the clay materials, the zeolites or acidic amorphous silica-alumina may advantageously contain transition metal such as iron, cobalt, nickel, platinum, palladium, iridium or mixtures thereof. The transition metals may occupy either framework or exchange positions in the solid acids or remain occluded on the internal or external surfaces. According to another embodiment, other activating oxides such as the rare earth oxides which comprise of mixtures of oxides of the elements belonging to the lanthanide series, such as lanthanum, cerium, erbium, praseodymium etc. may also be present in ion exchange positions or as occluded materials in the solid acids. According to one more embodiment, the solid acids are generally formulated with conventional binders such as silica, alumina, clays etc. into a suitable form such as extrudates or spheres or granules to give greater mechanical strength to the catalyst particles. The process of the present invention is illustrated with the following examples which are only illustrative in character and should not be construed as limitations of the process. Example 1 This example illustrates the oxidation of a linear paraffin using air and a solid transition metal complex in the first reaction zone. In an autoclave, 15 g of n-dodecane, 30 g of acetonitrile solvent and 0.3 g of solid iron tetradeca chlorophthalocyanine ocmplex were stirred at 60°C with continuous bubbling of air for 8 hours. At the end of the reaction, the solid catalyst was separated from the mixture by filtration and the residue in the flask homogenized with a small quantity (10 ml) of acetone and analyzed by gas chromatography using a 50 m long capillary column (HP 1). The composition of the mixture in mole percent was 83% n-dodecane, 14% 1-dodecanol, 1% 1-dodecanal and 2% of 2-dodecanol, with traces of 2-dodecanone. Example 2 This example illustrates the integrated process of the present invention comprising the oxidation of n-decane with air in a first reaction zone and the alkylation of benzene with the reaction product to linear alkyl benzenes in a second reaction zone. In an autoclave, 15 g of n-decane, 30 g of acetonitrile solvent and 0.3 g of solid manganese tetra-decachlorophthalocyanine were stirred at 60°C with a continuous bubbling of air for 6 hours. At the end of the reaction, the catalyst was separated from the liquid by filtration. 25 g benzene was added to the mixture and the contents placed inside a 300 ml stainless steel autoclave supplied by Parr Instruments, USA. 1.0 g of a Re-HY zeolite powder containing 12 wt % of rare earth oxides and 0.02 wt % of Pd was added to the contents. The autoclave was sealed and pressurized with hydrogen to 150 psi. The contents were stirred and heated to 140°C while maintaining the pressure at 150 psi. The heating and stirring was maintained for 4 hours. At the end of the four hours, the autoclave was cooled and depressurized. The catalyst was separated by filtration and the product analyzed by gas chromatography using a 50 m HPl capillary column. The product contained (on a Benzene free basis) 11.8% of the linear alkyl benzenes, namely decyl benzenes and 88.2% of unreacted decane. Non-normal alkanes, isodecyl benzenes and undesirable aromat-ics such as naphthalenes were not detected in the product. We Claim: 1. A process for production of linear alkyl benzenes comprising the steps of a) reacting linear paraffin with an oxygen containing gas in the presence of a solid catalyst containing an organotransition metal complex selected from pthalocyanin or porphyrin wherein some or all of the hydrogen atoms of the solid organ transition metal complex encapsulated in solid matrix have been substituted by one or more electron withdrawing groups in presence of solvent at a temperature in the range of 20°C to 100oC and a pressure in the range of 5 to 1000 psi to obtain alcohol b) reacting the alcohol with a mixture of benzene and molecular hydrogen in the presence of an alkylation catalyst containing acid at a temperature in the range of 25 to 200°C and separating the linear alkyl benzenes from the reaction mixture by conventional methods. 2. A process according to claim 1 wherein the linear paraffin contain from 8 to 20 carbon atoms. 3. A process according to claims 1-2 wherein the transition metal of the organotransition metal complex is selected from iron, cobalt, copper, chromium, manganese or mixtures thereof. 4. A process according to claims 1-3 wherein the said electron withdrawing group is selected from the halogens, the nitro group, the cyano group or mixtures thereof. 5. A process according to claim 1 wherein the alkylation catalyst a transition metal selected from the group consisting of iron, cobalt, nickel, platinum, palladium, iridium and mixtures thereof in intimate contact with a zeolite selected from the group containing modern, beta, X, Y and ZSM-12. 6. A process according to claims 1-4 wherein the solvents used is acetonitrile, ethanol. 7. A process according to claim 1 - 5 wherein a promoter used is alkyl hydro peroxides. 8. A process according to claim wherein the solid matrix used is an inorganic oxide is selected from silica, alumina, alumina silicates or zeolites. 9. A process according to claim 9 wherein the solid matrix is an organic polymer, selected from polystyrene. 10. A process according to claim 9, wherein the solid matrix contains both an inorganic oxide and an organic polymer. 11. A process according to claim 1 wherein the alkylation's catalyst contains acids selected from as HF or AICI3. 12. A process for the production of linear alkyl benzenes substantially as herein described with reference to the examples.

Documents:

662-del-1996-abstract.pdf

662-del-1996-claims.pdf

662-del-1996-complete specification (granted).pdf

662-del-1996-correspondence-others.pdf

662-del-1996-correspondence-po.pdf

662-del-1996-description (complete).pdf

662-del-1996-form-1.pdf

662-del-1996-form-2.pdf

662-del-1996-form-3.pdf

662-del-1996-form-4.pdf