MCM22 molecular sieve

In 1990, MOBIL company first reported the synthesis of MCM-22 molecular sieve. Because MCM-22 molecular sieve contains two pore systems of 12-membered ring and 10-membered ring, and as a catalyst carrier, it has good hydrothermal stability and large The pore structure, specific surface area and micropore volume have attracted great attention from domestic and foreign researchers. MCM-22 molecular sieve has broad application prospects in catalytic cracking, isomerization, anaerobic aromatization of methane, and alkylation of benzene and short-chain olefins.
1. Structural characteristics of MCM-22 molecular sieve
MCM-22 molecular sieve has two sets of non-interconnected multi-dimensional pore systems (Figure 1). One set is a two-dimensional sinusoidal channel with an effective aperture of (0.4nm×0.59nm), and the other set is composed of a super cage containing a twelve-membered ring (0.71nm×0.71nm×1.82nm), and its opening is also ten yuan ring.
MCM-22 molecular sieve is slightly smaller than β zeolite, which is also a twelve-membered ring (the pore size of the linear channel is about 0.57nm×0.75nm, and the pore size of the nonlinear tortuous channel is about 0.56nm×0.65nm). Therefore, MCM-22 molecular sieve has better selectivity for certain reactions. For example, when benzene is alkylated with acetonitrile and propionate to produce styrene and cumene, the by-products of diethylbenzene and dicumene are due to It is hindered in the ten-membered ring channel of MCM-22 molecular sieve, and has high selectivity. The MCM-22 molecular sieve has a larger pore volume than the ten-membered ZSM-5. When more branched chain isomers participate in the reaction, its entry into the ZSM-5 ten-membered ring channel is hindered, but MCM- The twelve-membered ring channel of 22 molecular sieve is unblocked for multi-branched compounds, and more IC is generated. In addition, the difference in the diffusion properties of different molecules also reflects its shape selectivity.

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