Low-carbon olefins from methyl chloride
Stian Svelle et al. Studied H-SAPO-34 molecular sieve catalyzed the reaction of CH3C1 and CH3Br to produce lower olefins. The total volume flow of halogenated alkane and He at 450 ° C was 10 m L · min. Under the conditions of CH3C1 and CH3Br partial pressure of 10 kPa and space velocity of 0.8 h-1, the initial conversion of CH3Cl was 62.5%, and the reaction was performed for 2 h. The selectivity of ethylene and propylene was 55% and 28%, respectively. The initial conversion of CH3Br was 47.5%. After 2 h of reaction, the selectivities of ethylene and propylene were 58% and 24%, respectively. The effect of CH3 C1 partial pressure change on the reaction results shows that the olefins produced by CH3C1 follow the first-order reaction rate equation at (350 ～ 450) ℃. Under the same reaction conditions, the reaction of methane halide to produce lower olefins shows similar rules in the reaction induction period, product distribution, distribution of hydrocarbon species in the carbon pool in the catalyst, and MTO reaction. When using halogenated alkanes as raw materials to prepare low-carbon olefins, the catalyst bed can be filled with propylene before the raw materials are introduced, which can shorten the reaction induction period.
Zhang Dazhi et al. Synthesized a series of M gSAPO-34 molecular sieves with different magnesium contents. A fixed-bed microreactor was used to investigate the effect of M g —SA PO-34 molecular sieves on methyl chloride at a reaction temperature of 450 ° C, a space velocity of 3.2 h-1 and (CH 3C1): V (N2) = 1: 1 For catalytic performance, SAPO-34 and Mg-SA PO-34 exhibited high initial activity, with ethylene and propylene selectivity reaching 80%. With SA PO-34 molecular sieves, except for M g, which has the highest M g content—SA PO-34, M g enters the SA PO-34 molecular sieve framework, which is conducive to maintaining high catalytic activity. Other M g modified SA PO-34 The decrease rate of molecular sieve catalytic activity is less than SA PO-34, and the catalyst life is significantly improved. SAPO-34 catalyzed the selectivity of ethylene in the reaction of methyl chloride, while Mg-SAPO-34 catalyzed the selectivity of propylene in methyl chloride. It may be that due to the presence of Mg, fewer si atoms enter the molecular sieve framework, the acidic sites are reduced, and the acid density and the strength of the acidic center are reduced. Weak acidity is beneficial to reduce hydrogen transfer reaction and improve low-carbon olefin yield
