Hydrodehalogenation catalyst and preparation method of chlorotrifluoroethylene and trifluoroethylene

Abstract

The invention discloses a hydrodehalogenation catalyst and a preparation method of chlorotrifluoroethylene and trifluoroethylene. The catalyst carrier for the hydrodehalogenation catalyst comprises a porous carbon-metal halide compound formed by firing a porous carbon substrate and a metal halide modifier, and the amount of metal halide in the catalyst carrier accounts for 0.01-10% by weight.

Description

technical field [0001] The invention relates to a hydrodehalogenation catalyst and a method for simultaneously preparing chlorotrifluoroethylene and trifluoroethylene. In addition to improved product selectivity, the catalysts of the present invention also have improved service life, thereby reducing operating costs. [0002] technical background [0003] Fluorine-containing olefins such as chlorotrifluoroethylene (CTFE) and trifluoroethylene (TrFE) have high added value in the field of fluorine chemical industry. One of the important raw materials of fluorine fine chemicals. At present, the industry mainly adopts zinc powder to reduce 1,1,2-trifluorotrichloroethane to produce CTFE, but this route consumes a lot of zinc powder and has high environmental protection costs, so a new process route is urgently needed to replace it. [0004] The synthesis of trifluoroethylene (TrFE) mainly includes the hydrogenation of CTFE and the cracking of tetrafluoroethane (HFC-134a), but it...

AI Technical Summary

Problems solved by technology

At present, the industry mainly uses zinc powder to reduce 1,1,2-trifluorotrichloroethane to produce CTFE. However, this route consumes a lot of zinc powder and has high environmental protection costs. A new process route is urgently needed to replace it.

[0004] The synthesis of trifluoroethylene (TrFE) mainly includes the hydrogenation of CTFE and the cracking of tetrafluoroethane (HFC-134a), but at present, due to the limited source of raw materials and immature catalytic technology, its large-scale industrial application is still restricted.

However, the study found that both types of catalysts have different degrees of deactivation problems.

[0007] Chinese patent CN1065261 discloses that the noble metal-supported activated carbon catalyst with copper as a cocatalyst can be used for the hydrodechlorination of 1,1,2-trifluorotrichloroethane to produce chlorotrifluoroethylene and trifluoroethylene, and the adjustment of the copper content can change the three The formation ratio of chlorofluoroethylene and trifluoroethylene, and different noble metals such as palladium and platinum also affect the ratio of the two. The selectivity of chlorotrifluoroethylene and trifluoroethylene is usually greater than 90%, but the life of the catalyst is not long , the inactivation phenomenon appeared after 300 hours of reaction

[0008] Chinese patent CN1460549 has reported that the catalyst with coconut shell carbon as the carrier and copper palladium as the main active component is used for CFC-113 hydrodechlorination to prepare CTFE, and it is found that some alkali metals and alkaline earth metals can significantly improve the efficiency of CTFE as modification aids. Selectivity (>85%), but the catalyst still has obvious deactivation phenomenon, and the service life is less than 1000 hours

However, from the perspective of the carrier preparation process, due to the generally low specific surface area of ​​metal fluorides such as aluminum fluoride and the limited loading and dispersion of active metals, it is difficult to use these metal fluorides alone as carriers to prepare catalysts. The method to prepare aluminum fluoride with high specific surface area still has a lot of alumina components, which is unfavorable for the hydrogenation catalyst and the long-term operation reaction under the atmosphere of hydrogen chloride or hydrogen fluoride. Compared with the catalyst directly supported by activated carbon, its long-term service life is also in doubt

[0012] Although the existing catalysts can achieve a higher conversion rate of CFC-113, the performance of the catalyst is mostly aimed at improving the selectivity of CTFE, and other products of hydrogenation are less concerned, and it is difficult to obtain high-quality TrFE, and according to the polymer Monomer requirements, but also to minimize unwanted impurities in fluoroolefins