METHOD FOR PREPARING HYDROCARBON CATALYTIC CRACKING CATALYST COMPOSITIONS

Abstract: Impregnation of a crystalline aluminosilicate-containing cracking catalyst with a metal component of Group IVB enhan­ ces the catalytic activity, gasoline selectivity and thermal and hydrothermal stability of the catalyst, and further improves the catalyst's capacity of producing a high-octane gasoline.

Description: BACKGROUND OF THE INVENTION The present invention relates to a method for preparing hydrocarbon cracking catalyst compositions, in particular relates to a method for preparing catalyst compositions which exhibit high catalytic activity, gasoline selectivity and thermal and hydrothermal stability, and further can produce a high-octane gasoline. Catalytic cracking of hydrocarbon basically aims at the production of gasoline. Therefore, the catalysts used are required to possess high catalytic activity and gasoline selectivity, and are preferably capable of producing a high-octane gasoline. In addition, thermal and hydrothermal stability for repeated use is also one of the requisites for cracking catalysts because it is customary in the commercially practiced catalytic cracking process to repeat the operation which comprises regenerating the deactivated catalysts which have been used in the reaction and thereafter employing the thus regenerated catalysts again in the reaction. In the typical hydrocarbon catalytic cracking process, there has generally been used a catalyst which comprises a crystalline aluminosilicate dispersed in a porous matrix selected from silica, silica-alumina, silica-magnesia and the like. When these catalysts are classified from the viewpoint of the exchangeable cations of the crystalline aluminosilicate, they can be roughly classified into those in which the crystalline aluminosilicate dispersed in the porous matrix takes the hydrogen form and those in which it is ion-exchanged with rare earth metal. The former catalyst is generally inferior in catalytic activity and gasoline selectivity but advantageous in that it can produce a high-octane gasoline, as compared with the latter catalyst, and the latter catalyst, in contrast, is superior in catalytic activity and gasoline selectivity but disadvantageous in that it can not produce a high-octane gasoline. However, the latter catalyst possesses thermal and hydrothermal stability exceeding that of the former catalyst, because the crystalline aluminosilicate has been ion-exchanged by the rare earth metal in the case of the latter catalyst. It is to be noted that even the former catalyst (using the crystalline aluminosilicate taking the hydrogen form) can improve the thermal and hydrothermal stability of the catalyst by using the so-called ultra-stable crystalline aluminosilicate. In such a case, however, merits and demerits as stated above are caused depending on whether the ultra-stable crystalline aluminosilicate takes the hydrogen form or the rare earth form; that is, when the former is used, it is impossible to expect the catalytic activity, gasoline selectivity and thermal and hydrothermal stability to such an extent that can be expected when the latter is used, and when the latter is used in contrast with this, it is impossible to produce a high-octane gasoline to such an extent as with the former. In summary, for conventional catalytic cracking catalysts which comprise a crystalline aluminosilicate in dispersed a porous matrix, limits are set to the improvement of catalytic activity, gasoline selectivity and thermal and hydrothermal stability when the aluminosilicate takes the hydrogen form, and limits are set to the improvement of the octane number of the product gasoline when the aluminosilicate takes the rare earth form. US-A-1 4263174 describes for example a catalyst powder comprising a zeolite and a porous carrier which contains zirconia, which powder is impregnated with a rare earth metal compound. SUMMARY OF THE INVENTION We have carried out various studies so as to develop further improved cracking catalysts to find that when a metal component Group IVB of the Periodic Table which gives a higher melting oxide than silica is introduced into a catalyst which comprises a crystalline aluminosilicate dispersed in a porous matrix, the catalyst using the crystalline aluminosilicate in the hydrogen form can improve its own catalytic activity, gasoline selectivity and thermal and hydrothermal stability without affecting the octane number of the gasoline to be produced, while a catalyst using the aluminosilicate in the rare earth form can improve the octane number of the gasoline to be produced without affecting its own catalytic activity, gasoline selectivity and thermal and hydrothermal stability. The method for preparing hydrocarbon cracking catalyst compositions according to the present invention is characterized by the steps of spray drying an aqueous slurry of a mixture of a precursor of a porous matrix and a crystalline aluminosilicate to thereby prepare fine spherical particles, washing the particles and drying them, and thereafter introducing a metal component of Group IVB of the Periodic Table into the particles. DETAILED DESCRIPTION In the present invention, the precursor of the porous matrix denotes hydrosol or hydrogel which gives, on drying, a silica-containing porous inorganic oxide as represented by silica, silica-alumina, silica-magnesia or the like. As an additive to this precursor, there can be employed one or more of alumina, kaolin, bentonite and the like on condition that the amount of silica derived from the hydrosol or hydrogel is 5 wt.% or more of the final catalyst composition. As the crystalline aluminosilicate, there can be employed material in the hydrogen or rare earth form, and the so-called ultra-stable crystalline aluminosilicate is naturally included therein. The crystalline aluminosilicate in the hydrogen form is generally prepared by the steps of exchanging the alkali metal ions of a natural or synthetic crystalline aluminosilicate with ammonium ions and calcining the resulting aluminosilicate in the ammonium form. The catalyst composition prepared by the method according to the present invention is subjected to substantially the same heat treatment as the above calcination during its preparation and during its actual use as the catalyst. Therefore, the present invention can also use the crystalline aluminosilicate in the ammonium form. The amount of crystalline aluminosilicate is generally in the range of 5-50 wt.% of the final catalyst composition. According to the method of the present invention, the above mentioned precursor of the porous matrix is mixed with the crystalline aluminosilicate, the same being added with alumina, kaolin, bentonite or the like in case of necessity, and thereafter the aqueous slurry of this mixture is spray-dried in the usual manner, whereby fine spherical particles are prepared. The aqueous slurry in this instance may be adjusted so as to have an optional solid concentration within the range where spray-drying is applicable. In spray-drying, there may be employed the conditions which have conventionally been employed in the preparation of cracking catalysts. The fine spherical particles obtained by spray-drying are washed until the alkali metal content therein is reduced to 1.0 wt.% or less as oxide, and thereafter dried. Then, the metal component selected from Group IVB of the Periodic Table is introduced into the dried particles As the compounds used for metal introduction there may be used chlorides, sulfates, nitrates and acetates of Group IVB metal such as titanium, zirconium, hafnium or the like. This introduction is carried out by impregnating the fine spherical particles with an aqueous solution containing one or more kinds of Group IVB metal compounds. In this instance, it is preferable that impregnation of the metal component selected from Group IVB of the Periodic Table should be carried out by preparing an aqueous IVB metal compound solution of a volume more than 2 times that of the fine spherical particles, and dipping them in said solution while stirring at least for 10 minutes. The amount of the metal component of Group IVB of the Periodic Table introduced is adjusted to be in the range of 0.3-8 wt.% of the final catalyst composition (as oxide). The reason is that outside this range it is impossible to improve the catalytic performance as intended by the present invention, and especially when the metal component of Group IVB is introduced in an amount exceeding the above range, the catalytic activity of the catalyst deteriorates. The fine spherical particles into which the predetermined amount of the metal component of Group IVB has been introduced, are washed if necessary and dried, whereby the catalyst composition according to the present invention can be obtained. Although the theoretical ground why the catalyst composition obtained according to the present invention exhibits a superior hydrocarbon catalytic cracking performance is not always clear, it is believed that in the method of the present invention wherein the fine spherical particle is first prepared from the mixture of the precursor of the porous matrix and the crystalline aluminosilicate and then the metal component of Group IVB is introduced in this particle, a part of the metal component of Group IVB introduced in the catalyst combines with the porous matrix and the other part thereof ion-exchanges with the crystalline aluminosilicate, and thus the performance of the catalyst is improved depending on the mode of the existence of said metal component in the composition. In this connection, it is to be noted that when the metal component of Group IVB is added to the aqueous slurry containing the precursor of the porous matrix and the crystalline aluminosilicate, this metal component contacts the precursor of high pH to deposit thereon and so does not ion-exchange with the crystalline aluminosilicate, and therefore it is impossible to obtain the catalyst of high efficiency as prepared by the method of the present invention even by the way of spray-drying the aqueous slurry added previously with the metal component of Group IVB. Next, the present invention will be explained more concretely with reference to examples. It is to be noted that the present invention should not be limited to these examples. Example 1 A commercially available water glass No. 3 (JIS K 1408) was diluted to prepare a water glass solution having a SiO₂ concentration of 12.73%. This water glass solution and sulfuric acid regulated to have a concentration of 25% were mixed in the ratios of 20 ℓ/min. and 5.6 ℓ/min. continuously for 10 minutes, thereby preparing a silica hydrosol. This hydrosol was mixed with kaolin so that the kaolin weight can become 60% based on the weight of the final composition, and was further mixed with a 30% aqueous slurry of ammonium exchanged Y type crystalline aluminosilicate, designated as NH₄-Y, (exchange rate 92%) so that the crystalline aluminosilicate weight can become 20% based on the weight of the final catalyst composition. This mixture was spray-dried in a hot air at a temperature of 220°C, and the resulting fine spherical particles were washed and thereafter dried to thereby prepare Catalyst A. Next, 4 zirconium acetate solutions having such different concentrations that the zirconium contents in the catalyst would be 0.3 wt.%, 2.0 wt.%, 7.5 wt.% and 9 wt.% as oxide were prepared. 100 g of catalyst A was dispersed in each solution. This dispersion was stirred at room temperature for 30 minutes. Then, the solution was removed therefrom by means of Nutche, and the particles washed and dried. Catalysts A-1, A-2, A-3 and A-4 were thus obtained. Example 2 Catalyst A obtained in Example 1 was calcined at 600°C for 2 hours. 100 g of this catalyst was impregnated with 23 ml of an aqueous titanium lactate solution corresponding to the pore volume (0.23 ml/g) of said catalyst, kept standing at room temperature for 1 hour and thereafter dried at 120°C for 12 hours to thereby obtain Catalyst A-5. This catalyst was observed to contain titanium in an amount of 1.9 wt.% as oxide. Example 3 Catalyst B was obtained according to the exactly same procedure as Example 1 except that rare earth exchanged Y type crystalline aluminosilicate, designated as RE-Y, (exchange rate 67%) was employed in place of the ammonium exchanged Y type crystalline aluminosilicate. Said Catalyst B was divided into three portions and dispersed in aqueous solutions of titanium chloride, zirconium acetate and hafnium acetate respectively. These dispersions were stirred at room temperature for 30 minutes, and thereafter the solutions were removed therefrom. The resulting particles were washed and dried to thereby prepare - Catalysts B-1 to B-3. The amounts of metals of Group IVB in said catalysts are as shown below. Comparative Example A silica hydrosol was prepared according to the same procedure as Example 1. This silica hydrosol was divided into two parts. One part was mixed with an aqueous zirconium sulfate solution, and the other part with an aqueous titanium sulfate solution. Next, kaolin was added to each slurry so that the kaolin content can become 50% based on the weight of the final catalyst, and an aqueous slurry of NH₄-Y (exchange rate 92%) whose concentration had previously been adjusted to be 30% was further added thereto so that said slurry can become 20% based on the weight of the final catalyst. Each mixture was spray dried in hot air at 220°C, and thereafter washed and dried to thereby prepare Catalyst C and Catalyst D. Catalyst C was observed to contain 2.0 wt.% of zirconium and Catalyst D was observed to contain 2.0 wt.% of titanium respectively as oxide. Catalytic Performance Test The catalysts obtained in the above mentioned Examples and Comparative Example were calcined at 600°C for 2 hours, thereafter subjected to 17 hours' treatment at 750°C in a 100% steam atmosphere, and further calcined at 600°C for 1 hour. The thus treated catalysts were subjected to catalytic activity test. A hydrodesulfurized vacuum gas oil was employed as the feed oil. As the reaction conditions there were employed the following conditions: reaction temperature = 482°C, WHSV = 2.2hr -1 , and catalyst/oil ratio = 5.6. In order to measure the thermal and hydrothermal stability, a part of each catalyst was calcined at 600°C for 2 hours, thereafter subjected to 17 hours' treatment at 810°C in a 100% steam atmosphere, and then calcined at 600°C for 1 hour. These catalysts were subjected to the catalytic activity test. The obtained catalytic activity test results are shown in the following table. As is evident from the results shown in the table, the catalysts obtained according to the method of the present invention are superior in the thermal and hydrothermal stability, and further can produce high octane gasolines.

Claims: A method for preparing hydrocarbon catalytic cracking catalyst compositions which comprises preparing fine spherical particles by spray-drying an aqueous slurry containing a precursor of a porous matrix and a crystalline aluminosilicate washing and drying the particles, and thereafter introducing a metal component into the particles, characterised in that the metal component is selected from Group IVB of the Periodic Table and is introduced into the particles in an amount of 0.3 - 8 wt.% of the final catalyst composition (as oxide). A method according to claim 1 wherein said metal component is one or more of titanium, zirconium and hafnium. A method according to claim 1 or claim 2 wherein at least 5 wt.% of the final catalyst composition is silica derived from the precursor of the porous matrix. A method according to any preceding claim wherein the crystalline aluminosilicate is used in the hydrogen form, the ammonium form or the rare earth form. A method according to any preceding claim wherein crystalline aluminosilicate amounts to 5-50 wt.% of the final catalyst composition. A method according to any preceding claim wherein said metal component of Group IVB is introduced by impregnation.

Inventors: HIRAI, TOSHIHARU, OGATA, MASAMITSU, SATO, GORO
Applicants: CATALYSTS & CHEMICALS INDUSTRIES CO., LTD.
Application year: 1985
Main classification: B01J29
IPC codes: C10G11, B01J29