A kind of synthetic method of titanium-silicon molecular sieve with high skeleton titanium content

Abstract

The invention provides a synthesis method of a titanium-silicon molecular sieve with a high content of framework titanium. Due to the steps of dealcoholizing stepwise, pre-crystallizing, then adding an appropriate amount of a fatty amine compound into a molecular sieve, and crystallizing hydrothermally further, the loss of framework titanium in the process of synthesizing the molecular sieve can be reduced and the formation of non-framework titanium can be avoided.

Description

technical field [0001] The invention belongs to the technical field of petrochemical catalysis, and in particular relates to a preparation method of a TS-1 titanium-silicon molecular sieve with an MFI structure. Background technique [0002] Titanium-silicon molecular sieve TS-1 is a Pentasil-type heteroatom molecular sieve containing skeleton titanium atoms. In addition to maintaining the topological structure of the original MFI molecular sieve, TS-1 has a special skeleton Si-O-Ti bond due to the uniform distribution of titanium atoms in the skeleton, which makes it have both catalytic oxidation activity and shape-selective catalytic performance. [0003] In 1981, USP4410501 disclosed the synthesis method of TS-1 for the first time. After 40 years of continuous development and research, the hydrothermal synthesis of TS-1 has formed two systems, one is using tetrapropylammonium hydroxide (TPAOH ) as a template to synthesize titanium-silicon molecular sieve, which is calle...

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Problems solved by technology

One is to modify the prepared TS-1 titanium-silicon molecular sieve, mainly using the modification of inorganic base or organic base to generate holes in TS-1 to promote the diffusion of reactants and products. Adding a separate modification process after completion will increase the production process and cost. The addition of alkaline substances will often introduce new impurities, which is not conducive to the separation and purification of TS-1 products, and may also cause certain corrosion to equipment role, increased maintenance costs

The second is to control the synthesis conditions of TS-1 titanium-silicon molecular sieve. It is generally believed that the reason for the generation of non-skeletal titanium is that the hydrolysis speed of the silicon source and the titanium source are inconsistent, which makes it very difficult to accurately grasp the hydrolysis conditions and make them match each other, resulting in local inhomogeneity. In the improved preparation process, the silicon source is often pre-hydrolyzed to a certain extent, or fatty acids are added to the titanium source to slow down the hydrolysis rate of the titanium source, so that the hydrolysis rate of the silicon source and the titanium source are as consistent as possible. Although some progress has been made in inhibiting the formation of non-framework titanium, the generation of non-framework titanium has not been completely avoided.

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