Molecular sieves with shape-selective properties and their direct synthesis

Abstract

The invention relates to a molecular sieve with shape-selective performance and a direct synthesis method thereof. The content of aluminum on the outer surface of the molecular sieve is lower than that of bulk phase aluminum; in the room-temperature static absorption test of the molecular sieve, pX / mX is larger than 8, wherein pX is p-xylene, and mX is m-xylene. The molecular sieve can be applied to the shape-selective catalytic reaction of toluene and / or benzene and alkylating reagents.

Description

technical field [0001] The invention relates to a molecular sieve with shape-selective performance and a direct synthesis method thereof. Background technique [0002] As one of the most important basic organic chemical raw materials, the demand for p-xylene has shown a strong growth trend in the past five years. Due to the rapid development of the downstream main product PTA industry, the market demand for PX will continue to rise rapidly in the next few years. It is expected that the average annual growth rate of demand will be 24.9%, and the annual consumption growth rate will reach 22.4%. By 2010, China's PTA plant consumption of PX will reach 5.4-6.1 million tons, and the construction of production capacity is far behind the growth of demand. The gap between China's PX demand and production will further expand. [0003] Aromatic alkylation is a catalytic reaction in which aromatic compounds react with an alkylating agent to produce p-xylene. At present, the most studi...

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Problems solved by technology

[0010] Generally speaking, an amorphous silicon oxide layer will form on the surface of ZSM-5 molecular sieve after being treated with a silicon-containing organic solution. A series of ZSM-5 with different surface structures can be obtained by changing the organic silicon treatment conditions and processes, but the process is cumbersome and the production high cost

In the synthesis process of core-shell molecular sieves, different surface structures can induce the growth of shell structures with different coverages, but the core-shell molecular sieves synthesized by this method need to be synthesized step by step, that is, the core-phase molecular sieves are synthesized first, and the silicalite is adhered to the core-shell molecular sieves. -1 and then secondary growth to obtain core-shell molecular sieves, the preparation steps are numerous, and the repeatability of industrial operations is poor

[0011] It can be seen from the above that the technology of aromatic hydrocarbon alkylation has made some progress in recent years, but the shape-selective modification methods used often have problems such as many preparation steps and poor repeatability of industrial operations.

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