ZSM-48 molecular sieve with low silica-alumina ratio and preparation method thereof

Abstract

The invention discloses a ZSM-48 molecular sieve with a low silica-alumina ratio and a preparation method thereof. The molecular sieve has the following properties: the molar ratio of silica to alumina is 25-50; the specific surface is 250-400 m2/g; the pore volume is 0.25-0.35 cm3/g; the average pore size is 3-5 nm. The preparation method comprises the following steps: (1) well mixing a seed crystal S, a template R, a silicon source, an aluminium source, sodium hydroxide and water to prepare a reaction mixture, wherein the composition of the reaction mixture is as follows: on a basis of oxide, the molar ratio of R to SiO2 is 0.05-0.2, the molar ratio of SiO2 to Al2O3 is 30-50, the molar ratio of Na2O to SiO2 is 0.06-0.1, the molar ratio of H2O to SiO2 is 15-23, the mass ratio of S to SiO2 is 0.05-0.5, S is the ZSM-48 molecular sieve, and R is 12-crown ether-4; (2) performing hydrothermal crystallization of the reaction mixture prepared in step (1) at 150-170 DEG C for 4-8 days, performing filtration, washing, drying, and roasting of the crystallization product to obtain the ZSM-48 molecular sieve with a low silica-alumina ratio. The ZSM-48 molecular sieve prepared by the method of the invention has a low silica-alumina ratio, and has good application prospects in technical fields of isodewaxing and the like.

Description

technical field [0001] The invention relates to a preparation method of a molecular sieve, in particular to a ZSM-48 molecular sieve with a low silicon-aluminum ratio and a preparation method thereof. Background technique [0002] In 1983, the patent USP4397827 reported the synthesis of ZSM-48 molecular sieve for the first time. ZSM-48 molecular sieve is a molecular sieve with ten-membered ring channel structure, and the pore size is 0.53nm×0.56nm. The pure silicon ZSM-48 molecular sieve has attracted wide attention for its good selectivity of low-carbon olefins in the reaction of synthesis gas to olefins. [0003] At present, the research focus of ZSM-48 molecular sieve is still on its synthesis process. The synthesis process of this molecular sieve has the following characteristics: (1) The silicon-aluminum ratio of the synthesized molecular sieve is high. The ratio is greater than 100; (2) If a low-cost template is used, although the cost of synthesizing molecular sieve...

AI Technical Summary

Problems solved by technology

Although the more expensive template agent hexamethylenediamine chloride is used in this patent, its effect is indeed very significant. The silicon-aluminum ratio of the feed is reduced to 100, the silicon-aluminum ratio of the product reaches about 100, and the crystallization time is also shortened. reduced to 48 hours

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