Cracking assistant for improving low-carbon olefin concentration

Abstract

The invention discloses a cracking assistant for improving a low-carbon olefin concentration. The cracking assistant comprises a modified MFI molecular sieve, a first clay-containing phosphor-aluminum inorganic binder and other inorganic binders, and second clay or no second clay. The first clay-containing phosphor-aluminum inorganic binder comprises an aluminum component, a phosphor component and first clay. The modified MFI molecular sieve contains phosphor and one or more of transition metals such as Fe, Co, Ni, Cu, Mn, Zn, Sn and Bi. There is not an absorption peak at the wavelength of 1633cm<-1> in a modified MFI molecular sieve infrared spectra obtained by trimethylpyridine as a probe molecule. Phosphorus distribution D is in a range of 0-0.8 and is a TEM-EDX-characterized ratio of phosphorus content of a part of a molecular sieve crystal grain to phosphorus content of the center of the molecular sieve crystal grain, wherein a distance between the part of the molecular sieve crystal grain and the edge of the molecular sieve crystal grain is 1 / 5 of a distance between the edge of the molecular sieve crystal grain and the center of the molecular sieve crystal grain. The cracking assistant is used for catalytic cracking, can improve a catalytic cracking liquefied gas yield, can improve yields of low-carbon olefins such as ethane, propylene and isobutene, can improve a low-carbon olefin concentration of catalytic cracking liquefied gas, can improve a heavy oil conversion capacity of a catalyst composition, and can improve the selectivity of dry gas and coke.

Description

Technical field [0001] The invention relates to a cracking aid used for catalytic cracking to produce low-carbon olefins. Background technique [0002] Low-carbon olefins are important organic chemical raw materials, and their demand is increasing year by year. Fluidized catalytic cracking is an important method for producing low-carbon olefins. In order to increase the yield of low-carbon olefins, it is an effective technical approach to use catalysts or additives containing zeolite with MFI structure in the catalytic cracking process. [0003] USP 3,758,403 earlier disclosed that the method of adding ZSM-5 zeolite to the catalytic cracking catalyst can increase the octane number of gasoline and increase C 3 ~C 4 The yield of olefins. For example, after adding 1.5, 2.5, 5 to 10% of ZSM-5 zeolite to a conventional catalyst containing 10% REY, the gasoline octane number will increase and the yield of low-carbon olefins will increase; the use of ZSM-5 zeolite will help It also has ...

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Problems solved by technology

[0021] At present, for the vast majority of catalytic cracking units, under the premise of the same liquefied gas yield, increasing the propylene concentration in the liquefied gas is an important way to improve the economic benefits of the catalytic cracking unit. The propylene additive of transition metal modified MFI molecular sieve is used in catalytic cracking process, the concentration of propylene in liquefied gas is low, the yield of dry gas and coke is high, and when the addition amount is large, the conversion capacity of heavy oil will be weakened

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