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  Fluid-bed catalyst for the preparation of ethylene and propylene by catalytic crackingUSPTO Application #: 20070042904Title: Fluid-bed catalyst for the preparation of ethylene and propylene by catalytic cracking Abstract: The present invention relates to a fluid-bed catalyst for the preparation of ethylene and propylene by catalytic cracking. The main technical problems to be solved are a relatively high reaction temperature, and low activities and poor selectivities of the catalyst at a low temperature, during the reaction for preparing ethylene and propylene by catalytically cracking naphtha. The technical solution of the catalyst is a composition of the chemical formula Mo1.0VaAbBcCdOX based on stoichiometric ratio. It has satisfactorily solved the above-mentioned problems, and is useful in the industrial production of ethylene and propylene by catalytically cracking naphtha. (end of abstract) Agent: Birch Stewart Kolasch & Birch - Falls Church, VA, US Inventors: Zaiku Xie, Hui Yao, Weimin Yang, Guangwei Ma, Jingxian Xiao, Liang Chen USPTO Applicaton #: 20070042904 - Class: 502305000 (USPTO) Related Patent Categories: Catalyst, Solid Sorbent, Or Support Therefor: Product Or Process Of Making, Catalyst Or Precursor Therefor, Metal, Metal Oxide Or Metal Hydroxide, Of Group Vi (i.e., Cr, Mo, W Or Po) The Patent Description & Claims data below is from USPTO Patent Application 20070042904. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to a fluid-bed catalyst for the preparation of ethylene and propylene by catalytic cracking, and in particular, a fluid-bed catalyst for the preparation of ethylene and propylene by catalytically cracking naphtha. BACKGROUND ART [0002] Currently, steam thermocracking is the most popular method for preparing ethylene and propylene, and naphtha is the raw material used most frequently. However, steam pyrolysis of naphtha has the disadvantages including a high reaction temperature, strict process conditions, high requirements for devices, especially furnace pipe materials, a large amount of CO.sub.2 that is released and big loss. It has become an issue attracting more and more attention to seek a suitable cracking catalyst, which does not effect the above disadvantages. [0003] In the patents U.S. Pat. No. 4,620,051 and U.S. Pat. No. 4,705,769 of Royal Philips Electronics (US), an oxide catalyst comprising manganese oxide or ferric oxide as the active component, the rare earth element La and the alkaline earth metal Mg is used for cracking C.sub.3 and C.sub.4 raw materials. The Mn,Mg/Al.sub.2O.sub.3 catalyst is put in a fixed-bed reactor in a laboratory, the temperature is 700.degree. C., the mol ratio of water to butane is 1:1, the butane conversion may reach 80%, and the ethylene and propylene selectivities are 34% and 20%, respectively. It is alleged in said two patents that naphtha and fluid-bed reactors are also usable. [0004] The patent CN1317546A of Enichem SPA (IT) relates to a catalyst of the chemical formula 12CaO.7Al.sub.2O.sub.3 for steam pyrolysis reactions. The raw material may be naphtha, the operational temperature is from 720 to 800.degree. C., the pressure is from 1.1 to 1.8 atm, the contact time is from 0.07 to 0.2 second, and the ethylene and propylene yield may reach 43%. [0005] In the patent USSR Pat 1298240.1987 (USSR), Zr.sub.2O.sub.3 supported on a pumacite or ceramic is used, the temperature is from 660 to 780.degree. C., the space velocity of the moderate device is from 2 to 5 h.sup.-1, the weight ratio of water to naphtha is 1:1. The raw materials are N-paraffin C.sub.7-17, cyclohexane and straight gasoline, the ethylene yield may reach 46% and the propylene yield may reach 8.8%. [0006] The patent CN1480255A (CN) introduces an oxide catalyst for the preparation of ethylene and propylene by catalytically cracking the raw material naphtha at a temperature of 780.degree. C., wherein the ethylene and propylene yield may reach 47%. [0007] To sum up, the current technology of preparation of ethylene and propylene by catalytic cracking requires a relatively high reaction temperature, but the yields of ethylene and propylene are not remarkably increased. CONTENTS OF THE INVENTION [0008] The technical problems to be solved by the present invention are to remove the disadvantages of the prior catalytic cracking technology, including a high reaction temperature, and low activities and poor selectivities of the catalyst at a low temperature. The present invention provides a novel fluid-bed catalyst for the preparation of ethylene and propylene by catalytic cracking. Said catalyst has the advantages of a low reaction temperature, superior catalytic activities, and high selectivity for ethylene and propylene. [0009] In order to solve the above technical problems, the present invention employs the following technical solution: a fluid-bed catalyst for the preparation of ethylene and propylene by catalytic cracking, said fluid-bed catalyst comprising a support selected from at least one of SiO.sub.2, Al.sub.2O.sub.3, molecular sieves and composite molecular sieves, and a composition of the following chemical formula based on stoichiometric ratio: Mo.sub.1.0V.sub.aA.sub.bB.sub.cC.sub.dO.sub.X, wherein A is selected from at least one element of Groups VIII, IB, IIB, VIIB, VIB, IA and IIA; B is selected from at least one of rare earth elements; C is selected from at least one of Bi and P; a is from 0.01 to 0.5; b is from 0.01 to 0.5; c is from 0.01 to 0.5; d is from 0 to 0.5; and X represents the total number of oxygen atoms that meets the valances of the elements in the catalyst, wherein the molecular sieve is at least one of ZSM-5, Y, .beta., MCM-22, SAPO-34 and mordenite, and the composite molecular sieve is a composite grown together from at least two molecular sieves of ZSM-5, Y, .beta., MCM-22, SAPO-34 and mordenite, and wherein the amount of the catalyst support as used is from 20 to 80% by weight on the basis of the weight of the catalyst. [0010] In this technical solution, a is preferably from 0.01 to 0.3, b is preferably from 0.01 to 0.3, c is preferably from 0.01 to 0.3 and d is preferably from 0.01 to 0.3. The element of Group VIII is preferably selected from at least one of Fe, Co and Ni, the element of Group IB is preferably selected from at least one of Cu and Ag, the element of Group IIB is preferably Zn, the element of Group VIIB is preferably selected from at least one of Mn and Re, the element of Group VIB is preferably selected from at least one of Cr, Mo and W, the element of Group IA is preferably selected from at least one of Li, Na and K, and the element of Group IIA is preferably selected from at least one of Ca, Mg, Sr and Ba. The rare earth element is preferably selected from at least one of La and Ce. When Cr is a component of the catalyst, the ratio of Mo: Cr is 1:0.01 to 0.5 based on stoichiometric ratio. In a preferred catalyst support, the molecular sieve is selected from at least one of ZSM-5, Y zeolite, mordenite and .beta. zeolite, and the composite molecular sieve is selected from at least one of ZSM-5/mordenite, ZSM-5/Y zeolite and ZSM-5/.beta. zeolite. The silica-alumina mol ratios, SiO.sub.2/Al.sub.2O.sub.3, of said molecular sieve and said composite molecular sieve are from 10 to 500, preferably from 20 to 300. The amount of the catalyst support as used is preferably from 30 to 50% by weight on the basis of the weight of the catalyst. [0011] The fluid-bed catalyst of the present invention for the preparation of ethylene and propylene by catalytic cracking is useful for catalytically cracking heavy oil, light diesel oil, light gasoline, catalytically cracked gasoline, gas oil, condensate oil, C.sub.4 olefin or C.sub.5 olefin. [0012] The catalyst of the present invention is prepared by the following process; the raw material Mo is from ammonium molybdate or phospho-molybdic acid, V is from ammonium metavanadate or vanadium pentoxide, Bi is from bismuth nitrate, A elements are from the corresponding nitrate, oxalate, acetate, oxide or soluble halide, B elements are from the corresponding nitrate, oxalate, acetate, oxide or soluble halide, and phosphorus is from phosphoric acid, triammonium phosphate, diammonium phosphate, ammonium biphosphate; the catalyst is shaped by heating and refluxing a slurry comprising the component elements and a support in a water bath at a temperature of 70 to 80.degree. C. for 5 hours, spray drying the slurry, and sintering the resultant powder in a muffle furnace at a temperature of 600 to 750.degree. C. for 3 to 10 hours. [0013] In the present invention, a series of transition metals and rare earth metals having cryosorption property, oxidation reduction property and dual functional acidic and basic sites complexation are used, which have relatively high low-temperature activities and play an oxidation catalysis effect on the raw materials. At a relatively low temperature of 600 to 650.degree. C., the catalyst is used in a reaction of catalytically cracking naphtha, resulting in a total yield of ethylene and propylene of up to 45.3% and achieving a better technical effect. [0014] The relevant catalyst is checked and evaluated with naphtha as the raw material (see Table 1 for specific indices). The reaction temperature ranges from 600 to 650.degree. C., the load of the catalyst is from 0.5 to 2 g naphtha/g catalysth, and the weight ratio of water to naphtha is 1.5 to 3:1. The internal diameter of the fluid-bed reactor is 39 mm, and the reaction pressure is from 0 to 0.2 MPa TABLE-US-00001 TABLE 1 Indices of the naphtha raw material Items data Density (at 20.degree. C.) kg/m.sup.3 704.6 Distillation range Initial distillation range .degree. C. 40 Final distillation range .degree. C. 160 Saturated vapor pressure (at 20.degree. C.) kPa 50.2 Paraffin % (by weight) 65.2 N-paraffin % 32.5 Cycloparaffin % 28.4 Olefin % (by weight) 0.17 Aromatic hydrocarbon % (by weight) 6.2 [0015] The present invention is further illustrated hereinbelow by the Examples. SPECIFIC EMBODIMENTS Example 1 [0016] 5.89 g bismuth nitrate was measured, and dissolved in 10 ml 1:1 concentrated nitric acid to produce a yellow solution. 30 g ammonium molybdate was measured and dissolved in 200 ml water. The ammonium molybdate aqueous solution was then added into the bismuth nitrate solution. The resultant mixed solution was stirred to prepare solution (I). [0017] 3 g ammonium metavanadate was measured and added in 100 ml water. Then, 2 ml 80% phosphoric acid was dripped and 3 g oxalic acid was added into the mixture of ammonium metavanadate and water. The resultant mixture was heated till ammonium metavanadate was completely dissolved, thus to prepare solution (II). [0018] 7.86 g cobalt nitrate, 5.58 g cerium nitrate and 6.72 g calcium nitrate were measured and dissolved in 250 ml water to prepare solution (III). [0019] Solutions (I), (II) and (III) were mixed. The mixed solution was heated and stirred in a water bath at a temperature of 70 to 80.degree. C. 26 g silica was measured and added into the mixed solution. The resultant solution was refluxed for 5 hours, and dried with a spray drier for shaping. The resultant powder was sieved, and put into a muffle furnace. The temperature was then elevated to 740.degree. C. The powder was sintered for 5 hours. After it was cooled, the catalyst was sieved. Continue reading... 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