High-activity tungsten-based catalyst

Abstract

The invention discloses a high-activity tungsten-based catalyst and belongs to the field of chemical synthesis. The high-activity tungsten-based catalyst is composed of, by mass, 60-100% of tungsten ions and 0-40% of auxiliaries. Total amount of fluorine or tungsten hexafluoride fed at an activation stage is equal to a sum of theoretical amount of fluorine or tungsten hexafluoride consumed by a precursor of the tungsten ions and theoretical amount of fluorine or tungsten hexafluoride consumed by metal element auxiliaries, and hexavalent tungsten is prone to loss, so that tungsten ion reduction is controlled in a trivalent, tetravalent or pentavalent state to the greatest extent when consumption of fluorine is calculated. The tungsten-based catalyst is high in using temperature, high in catalytic activity and long in service life and is mainly used for vapor-phase catalysis of halogenated olefin at high temperature for fluorine-chlorine exchange reaction to prepare fluorine-containing olefin.

Description

technical field [0001] The invention relates to a tungsten-based catalyst, in particular to gas-phase catalyzed fluorine-chlorine exchange reaction of halogenated olefins at high temperature to prepare fluorine-containing olefins. Background technique [0002] In order to fulfill the Montreal Protocol aimed at protecting the Earth's ozone layer, countries around the world have launched hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs) with zero ODP values, thereby phasing out chlorofluorocarbons (CFCs) and hydrofluorocarbons (CFCs) with non-zero ODP values Chlorocarbons (HCFCs). At present, HFCs and HFOs have been widely used as refrigerants, cleaning agents, foaming agents, fire extinguishing agents, etching agents, etc. [0003] At present, the industrial production of HFCs or HFOs mostly adopts the method of gas-phase catalytic fluorine-chlorine exchange reaction of halogenated organic substances. This method has the advantages of simple process, easy continuous la...

AI Technical Summary

Problems solved by technology

However, with the deepening of research, people found that chromium catalyst still has the defects of low use temperature, low catalytic activity, short service life, and difficulty in recycling. More importantly, chromium is toxic and can cause great harm to people. Especially high-valent chromium has strong carcinogenicity

According to research, hexavalent chromium is 100 times more toxic than trivalent chromium, and is easily absorbed and accumulated in the body, and its metabolism and clearance are slow

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