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...

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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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