Lichun Li,Xiaoli Wei,Shenglan Zhou,Zhongsheng Jia,Chuanzhao Wang,Houlin Yu,Sen Wu,Ying Li,Wenfeng Han
Hydrochlorofluorocarbon (HCFC) has been widely applied as the third-generation refrigerant globally, however, the global warming potential of such gases is often 100 and 1000 times higher than that of CO2. Dehydrochlorination reaction offers an encouraging strategy to transform the high-global-warming-potential gases of hydrochlorofluorocarbons (HCFCs) to low-global-warming-potential gases of hydrofluoroolefins (HFOs). However, the handling of a large amount of byproduct HCl remains one of the major challenges blocking the industrialization of dehydrochlorination of HCFC-142a for the production of vinylidene fluoride (VDF). A one-pot cascade reaction combining dehydrochlorination of HCFC-142b and hydrochlorination of acetylene was first proposed to spontaneously produce valuable monomers of VDF and vinyl chloride monomer (VCM) while eliminating the tedious HCl treatment step. Both thermodynamic calculations and experimental results validate the feasibility of the cascade reaction. Five different heterogeneous catalysts were screened for the proposed cascade reaction, including monocomponent catalyst BaF2, NAC, bifunctional BaF2/NAC catalyst, and bicomponent BaF2-NAC-S and BaF2-NAC-M catalysts. Among them, the mixed BaF2-NAC-M catalyst demonstrated the best catalytic performance, with BaF2 mainly acting as the dehydrochlorination site and NAC mainly acting as the hydrochlorination site. The corresponding reaction mechanism was also proposed.
Zhikun Wang,Wenfeng Han,Haodong Tang,Ying Li,Huazhang Liu
N-doped ordered mesoporous carbons (NOMC) were prepared with mixed solution of urea and sucrose as carbon source and nitrogen source. SBA-15 was adopted as the hard template. The effect of urea to sucrose molar ratio on NOMC was investigated. NOMC samples were characterized by techniques such as BET, TEM, XPS and TG. The catalytic performances of NOMC catalysts were evaluated for the pyrolysis of 1-chloro-1,1-difluoroethane (HCFC-142b, CH 3 CClF 2 ) to vinylidene fluoride (VDF, CH 2 =CF 2 ). The catalytic reactions were carried out at 400 °C and space velocity of 600 h −1 (based on HCFC-142b). The results indicate that NOMC exhibits a stable activity at 400 °C with high HCFC-142b conversion and selectivity to VDF. The textural parameters of NOMC play a major role in VDF selectivity and N species over the carbon surface are responsible for NOMC catalytic performance. Compared with the temperatures of industrial manufacture of VDF at 650–700 °C, the NOMC catalysts provide a promising pathway to produce VDF at much lower temperatures (below 400 °C).
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