Title of Invention

A PROCESS FOR THE PREPARATION OF FLUID CATALYTIC CRACKING CATALYST.

Abstract

Present invention deals with an improved process for the preparation of Fluid catalyst cracking catalyst by using catalytic active matrix and 60% dealuminated zeolite Y by hydrothermal treatment of NH4Y as compared to by treating NH4Y zeolite with the aq. solution of ammonium hexafluorosilicate, which creats mesoporoes up to the range of more than 150 A diameter which helps larger pores of resid fee to diffuse in to the pores of zeolite while the zeolite prepared by hexafluorosilicate method does not create larger pores in zeolite and the use of hexafluorosilicate is hazardous and is not environment friendly which is more selective and enhanced metal tolerance activity.

Full Text

This invention relates to an improved process for the preparation of fluid catalytic cracking catalyst. In particular, the invention relates to a process for the preparation of cracking catalyst using dealuminated Y type zeolite and catalytically active silica-alumina matrix as important components. The invention more specifically relates to a process for the preparation of fluid catalytic cracking catalyst using 60 % dealuminated zeolite-Y and catalytically active silica-alumina matrix which results in improved catalytic performance with respect to bottoms cracking and increased metal tolerance for processing the heavier feeds heavily contaminated with metals (Ni + V). Fluid catalytic cracking (FCC) occupies an important place in petroleum refining industry for the conversion of heavier petroleum fractions into valuable products like LPG, gasoline and middle distillate [Total cycle oil (TCO)] a blending component for diesel pool. It is well known that heavier feeds are heavily contaminated with metals like vanadium, nickel and iron. These metals particularly vanadium and nickel causes catalyst deactivation and promote undesirable non selective cracking. For the processing of heavier feeds, increase in heat load, higher thermal instability increased contaminated metals and decreased hydrogen availability dictate the catalyst requirement to meet the following objective: * Higher thermal and hydrothemral stability * Enhanced metal tolerance * High TCO selectivity * Minimum coke yield * Increased bottoms cracking i.e. reduced yield of material boiling above 370°C In the past the vacuum gas oil (VGO) fraction was the feedstock for the FCC units and became the major share of diesel and gasoline pool. The residual portions were not typically processed in this manner. Faced with the pressing demands of transportation fuels today the concept of "Bottom of the barrel" upgrading or resid processing has emerged. Many FCC units in India now using the blend of resid and VGO and many new units constructed recently will process resid exclusively. The resid portion of FCC feed is heavily laden with contaminan metals such as Nickel, Vanadium, Iron and Copper. The amount of carbon residue called conradson carbon, is also much higher than the vacuum gas oil fraction. The increased amount of metals and carbon residue in resid feeds cause catalyst deactivation and reduce selectivity, converting less oi' the feed into valuable products and pushing the units to the limits and constraints of their operating design. Keeping these consideration in mind as a result to extensive research work carried out by us, catalyst formulation has been developed which is more selective and have enhanced metal tolerance activity. The FCC catalyst is mainly composed of two parts, the zeolite and matrix component. The matrix unlike zeolite, is mesoporous amorphous material. In resid cracking the matrix plays an important role. The resid feed having larger hydrocarbon molecules cannot diffuse into micropores of zeolite. When these larger molecules are cracked, the contaminant metals are initially deposited on the catalyst surface, so the matrix must be able to provide different functionalities. In other words, the matrix must be able to control the contaminant metals like Nickel and Vanadium so that their contribution to contaminant selectivity such as formation of coke and dry gas (i.e. H2, C1 + C2) is minimized. Dealuminated zeolite-Y to the appropriate level of dealumination can withstand the process conditions used in the regeneration of coked catalyst and retention of activity and crystallinity of the zeolite part of the FCC catalyst is improved. Mesopores created during dealumination of zeolite are also helpful in the cracking of larger molecules present in the heavier feeds. Dealumination of zeolite results in decrease in unit cell size (UCS) and increase in the silica to alumina ratio of the zeolitic frame work which in turn affects the physicochemical properties and increase the thermal and hydrothermal stability. Such changes in zeolite composition and properties have a significant impact on catalytic activity, selectivity and stability. The dealumination to the appropriate level also modifies the acidity pattern of the zeolite and hence the activity and coke selectivity. Because of lower concentration of active sites, hydrogen transfer reactions are suppressed and thereby produce less coke and more olefinic products resulting in higher olefinicity of LPG. The catalytically active matrix serves one valuable purpose i.e. the cracking of larger molecules with increased accessibility of active sites of the matrix to the reacting molecules. The inclusion of active matrix in the catalyst formulation therefore leads to the decrease in the yield of bottoms i.e. the material boiling above 370°C. The active matrix preparation based on either silica-alumina gel prepared by sodium containing ingredients as a source of silica and alumina or alumina sol prepared by alumina chlorohydrate suffers the disadvantages of low apparent bulk density (ABD), poor attrition resistance due to low solid content of the catalyst slurry at pumpability for the spray drying, lower product yield due to losses incurred in the washing steps involved during the removal of impurities. The matrix prepared by the process of the present invention based on silica alumina sol prepared by using soda free materials like commercially available silica sol and disperal alumina hydrate, and allowing to stand for a period of 20-30 min. till the thickening of the slurry starts. To make the slurry free flowing, appropriate quantity of acidified slica soi is added. Silica sol added at this stage build silica layer around catalyst particle and capture Ni and V from heavy layer. The advantages of the present invention for the preparation of fluid cracking catalyst over the known processes in the prior art are as follows : 1: FCC catalysts slurry using the active matrix prepared by the process of the present invention meets the pumpable characteristics required for spray drying. 2. Solid content of the catalyst slurry is higher, 30 % resulting in higher ABD and attrition properties. 3. The catalyst prepared by the process of the present invention eliminates the washing steps to remove impurities giving higher product yield improving the process economics. 4. The catalyst prepared by the process of present invention eliminates the step of kaolin clay modification. 5. The catalyst prepared by the process of the present invention contain significantly higher percentage of larger pore in the 50 - 150 A° region and is ;nore resistant towards metal deactivation for the processing of heavier feeds containing larger molecules and heavily contaminated with metals like vanadium and nickel. First allowing the slurry to start thickening and then adding appropriate quantity silica sol to make it free flowing build silica layer around catalyst particles to trap Ni and V in the heavier feed. 6. Increased metal tolerance of catalyst reduces the catalyst replacement rate in the process which makes the process more economical. 7. Increased metal tolerance of catalyst eliminates the use of separate additive as metal traps and catchers, which also improves the economics of the process. The objective of the present invention is therefore, to provide a process for the preparation of FCC catalyst using 60 % dealuminated zeolite-Y and catalytically active matrix with increased bottoms conversion, better middle distillate and coke selectivity with improved physical properties. In carrying out the present invention, as a result of extensive research carried out by us, FCC catalyst was prepared having the active matrix, dealuminted zeolite Y to 60 % level of dealumination. The composition of the finished catalyst is presented in detail in Table-1. Accordingly, the present invention provides a process for the preparation of fluid catalytic cracking (FCC) catalyst which comprises : (i) Preparing silica-alumina sol by mixing commercial silica sol and dispersal alumina hydrate at controlled pH of 2.8 and allowing to age for a period of 20-30 min. till the thickening of the slurry starts, adding acidified silica sol to make the slurry free flowing to build silica layer around catalyst particles and capture Ni and V from heavy feed. (ii) Peptizing the dispersal alumina hydrate by adding nitric acid solution, (iii) Exchanging NaY to NH4Y zeolite by treating with an aqueous solution of an ammonium salt at reflux temperature, (iv) Subjecting to hydrothermal treatment of NH4Y zeolite in the presence of 100 % steam in the temperature range of 550 to 650°C for the duration of 1/2 to 1 1/2 hours to achieve 60 % dealuniination. (v) Treating with mineral acid other than H2SO4 for removing non framework aluminium, (vi) Dispersing 25 to 30 % of 60 % dealuminated zeolite-Y in silica-alumina active matrix consisting of 40 % silica-alumina sol, 10 % peptized alumina and 20-25 % kaolin clay, (vii) Treating the resultant obtained in step (vi) with rare earth salt such as lanthanum nitrate so as to get 1.0-3.0 % lanthanum exchanged, (viii) Filtering, washing, drying and then calcining the resultant obtained in in step (vii) at a temperature in the range of 400 to 600°C, (ix) thermal shocking the catalyst at 500-700°C for a period of 1 to 3 hours, (x) Metal dopping the resultant obtained in step (ix) with Nickel and vanadium salts. According to an embodiment of the present invention exchange of NaY zeolite to the NH4Y zeolite is affected by treatment with an aqueous solution of ammonium salt generally of 1-3 N strength at a temperature in the range of 70-100°C. The salt such as that of ammonium chloride sulfate or nitrate preferably ammonium nitrate may be used. This step is required to bring down the sodium content to less than 1%, where the concentration of the ammonium salt solution is so adjusted to have 2-6 equivalents of the cation per equivalent of total base exchange capacity. The NH4Y zeolite formed is heated to a temperature in the range of 550 to 650°C over a period of 1/2 to l½ hours in presence of steam in a specified anid controlled manner to achieve a degree of dealumination to 60%. The dealuminated zeolite-y obtained from the step (b) is treated with mineral acid to further enhance the crystallinity and pore size of the zeolite-y and reducing sodium content to less than 0.1%. The concentration of the acid in the range of 0.1 to 6N is so chosen that it does not affect the frame work aluminium. The acid used may be selected from any mono basic acid like hydrochloric acid or nitric acid. The dealuminated zeolite-y was then dispersed in active matrix prepared by the process of the present invention. Silica-alumina sol and peptized alumina constituted the active matrix. The silica-alumina matrix prepared by the process of the present invention is catalytically more active for the cracking of larger molecules present in me heavier FCC feedstocks and is better coke selective and metal resistant. The fresh catalyst prepared was dopped with nickel and vanadium salt by the well established method, artificially deactivated by hydrothermal treatment at high temperature in presence of steam at predetermined conditions of temperature, duration and steam partial pressure. Hydro thermally deactivated catalyst sample was subjected to detailed evaluation of catalytic activity and product selectivities in Micro Activity Test (MAT) unit at predetermined conditions of temperature, duration of reaction, cat/oil ratio etc. The invention may be practiced as illustrated in the following examples, which should not be construed to limit the scope of the present invention. Example -1 In a typical procedure, 600 ml commercial silica sol containing 32% silica of pH 9.5 was taken in a separating funnel. The silica sol was mixed slowly in acidified water (1320 ml water + 6 ml cone HNO3) by stirring. The final pH of diluted silica sol was 2.4 and silica concentration 10%. 68.8 g of fine power of disperal alumina was mixed with vigorous stirring. The silica-alumina sol was vigorously stirred for 20 minutes to disperse alumina in silica sol. The pH of silica-alumina sol was maintained between 2.7 to 2.8 by the addition of nitric acid. The silica-alumina sol prepared above was taken in a baffled vessel and added slowly 120g kaolin powder (anhydrous basis) with vigorous stirring maintaining me pH of the system at 2.8. After 10 minutes, 180g of 60% dealuminated zeolite-Y was added with vigorous stirring maintaining pH at 2.8. In other 10 minutes, 85.7g of peptized disperal alumina (60g anhydrous basis) was added with vigorous stirring maintaining the pH -3.0. The slurry was allowed to stand for 10-15 minutes till the thickening of slurry is observed. The appropriate quantity of acidified silica sol (10-15 ml) was added to make the slurry free flowing and pumpable suitable for spray drying. The above slurry was spray dried to get the desired particle size material. The spray dried material was calcined for 2 hours at 350°C. The catalyst prepared above was exchanged with lanthanum at 85°C for 2 hours. The solid to liquid ratio was kept 1:4. The concentration of lanthanum nitrate solution was 2.3%. The lanthanum exchanged catalyst was filtered, washed and dried in oven at 110°C for 16 hours. The dried material was calcined at 500°C for 2 hours. It was then sieved to get 100-230 mesh size particles. Example - 2 The catalyst prepared in example-1 was dopped with Nickel and Vanadium metals using the following method. 1. Thermal shock treatment (a) 30g fresh FCC catalyst was put in furnace at the temperature; of 593°C for one hour. (b) Allowed the catalyst to cool to 250°C and kept in dessicator. 2. Metal dopping (1500 ppm Nickel and 2000 ppm Vanadium) (a) Weigh accurately 0.75g Nickel Naphthanate and 2g Vanadium Naphthanate and added Benzene to make it 24 g (Ni + V Salt). (b) Added 24g benzene solution containing Ni and V salt to 30g thermally shocked catalyst and stirr with glass rod to homogenize the mixture . (c) Keep 30 minutes at RT to dry. (d) Keep overnight in oven at 110°C. (e) Calcined at 537°C for 3 hours. (f) Steam deactivate the catalyst at 788°C for 3 hrs in 100 % steam. Example - 3 The catalyst prepared in example-1 was dopped with (2000 ppm Ni and 3000 ppm V). The procedure in same as in example-2 except that 1.0 g Nickel Naphthanate and 3g Vanadium Naphthate is taken. Example-4 The catalyst prepared in example-1 was dopped with (5000 ppm Ni and 5000 ppm V). The procedure is same as in exaple-2 except that 2.5g Nickel Naphthate and 5.0g Vanadium Naphthate is taken. The metal dopped catalyst samples were hydrothermally deactivated in presence of 100 % steam at 788°C for 3 hrs and subjected to evaluation in Micro-Activity Test Unit. The performance data showing the metal tolerance capability of the catalyst prepared by the process of the present invention in comparison to commercially proven reference commercial catalyst has been presented in Table-2. The data clearly show that percent drop in conversion with the catalyst is only 10.7 where as it is 24.0 and 75.0 respectively with reference commercial catalyst. Thus, the present invention provides a process for the preparation of catalyst which has higher metal tolerance and can be effectively used for the cracking of feed stocks heavily contaminated with metals like Nickel and Vanadium which are known poisons for FCC catalyst. Due to higher metal tolerance, rate of addition of fresh catalyst to the inventory to compensate for the loss in activity as a result of metal deactivation is expected to be significantly reduced, making the process more economical. Higher metal tolerance of catalyst prepared by the process of the present invention will eliminate the use of costly metal traps/catches used as additive. Table-l Composition of FCC Catalyst (Table Removed) Table-2 Metal Tolerance Capability of FCC Catalysts Reaction Conditions Temperature : 510°C W/F(minute) : 0.5 (Table Removed) We Claim 1. A process for the preparation of fluid catalytic cracking (FCC) catalyst which comprises : (i) Preparing silica-alumina sol by mixing commercial silica sol and disperal alumina hydrate at controlled pH of 2.8 and allowing to age for a period of 20-30 min. till the thickening of the slurry starts, adding acidified silica sol to make the slurry free flowing to build silica layer around catalyst particles and capture Ni and V from heavy feed. (ii) Peptizing the disperal alumina hydrate by adding nitric acid solution, (iii) Exchanging NaY to NH4Y zeolite by treating with an aqueous solution of an ammonium salt at reflux temperature, (iv) Subjecting to hydrothermal treatment of NH4Y zeolite in the presence of 100 % steam in the temperature range of 550 to 650°C for the duration of 1/2 to 1 1/2 hours to achieve 60 % dealumination. (v) Treating with mineral acid other than H2SO4 for removing non framework aluminium, (vi) Dispersing 25 to 30 % of 60 % dealuminated zeolite-Y in silica-alumina active matrix consisting of 40 % silica-alumina sol, 10 % peptized alumina and 20-25 % kaolin clay, (vii) Treating the resultant obtained in step (vi) with rare earth salt such as lanthanum nitrate so as to get 1.0-3.0 % lanthanum exchanged, (viii) Filtering, washing, drying and then calcining the resultant obtained in in step (vii) at a temperature in the range of 400 to 600°C, (ix) thermal shocking the catalyst at 500-700°C for a period of 1 to 3 hours, (x) Metal dopping the resultant obtained in step (ix) with Nickel and vanadium salts. 2. A process as claimed in claim 1 wherein the ion exchange is affected by treatment with an aqueous solution of ammonium salt ranging from 1 to 3N at a temperature in the range of 70-100°C. 3. A process as claimed in claims 1 and 2 wherein the ammonium salt used are selected from ammonium chloride, sulfate or nitrate preferably ammonium nitrate. 4. A process as claimed in claim 3 wherein the concentration of the ammonium salt solution is so adjusted to provide 2-6 equivalents of the cation per equivalent of total base exchange capacity. 5. A process in claims 1 to 8 wherein salt used in step (X) is selected from corresponding octuates and sulphonate. 6. A process for the preparation of fluid catalytic cracking (FCC) catalyst substantially as here in described with reference to the examples.

Documents:

243-del-2000-abstract.pdf

243-del-2000-claims.pdf

243-del-2000-correspondence-others.pdf

243-del-2000-correspondence-po.pdf

243-del-2000-description (complete).pdf

243-del-2000-form-1.pdf

243-del-2000-form-19.pdf

243-del-2000-form-2.pdf