Catalytic coupling of CH₄ with CHF₃ for the synthesis of VDF over LaOF catalyst

Abstract

The oxidative coupling of methane (OCM) with CHF3 facilitates the synthesis of vinylidene fluoride (VDF). The aim is to utilize CHF3, which is otherwise considered a waste with a very high global warming potential. This study focuses on the effect of a LaOF catalyst on OCM occurring in the presence of CHF3, which engenders a promoting effect of O2 on CH4 activation. It examines the structural and phase changes of the lanthanum catalyst during the reaction and then speculates on the reaction mechanism. In combining OCM with CHF3, both the conversion of CH4 and the formation rate of VDF are almost tripled at 700°C. However, at higher temperatures, gas‐phase reactions play a dominating role in the conversion of CH4 and LaOF catalyst plays a very minor role in the reaction system at elevated temperatures. Irrespective of the reaction temperature, VDF is produced via the gas‐phase coupling of CH3 radicals with CF2. During pretreatment or during the reaction itself, La2O3 is fluorinated by CHF3 and HF, yielding the formation of surface LaOF and LaF3 species. LaF3 is a relatively inactive catalyst for CH4 conversion, whereas, in comparison LaOF appears to play a very important role in the activation of CH4 at low temperatures. The activation mechanism of CH4 at relatively low temperatures is similar with that postulated to occur during the OCM. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.

Experimental and DFT Mechanistic Study of Dehydrohalogenation of 1-Chloro-1,1-difluoroethane over Metal Fluorides

“…It explains low reaction rates at 300 and 350 °C. We suggest that the formation of ZnOCl and ZnOF is responsible for the relatively high reaction rates at reaction temperatures of 400 and 450 °C. , Similarly, formation of intermediates such as LaOF is responsible for the high conversion rate of HCFC-142b over the LaF 3 catalyst. , …”

“…45,46 Similarly, formation of intermediates such as LaOF is responsible for the high conversion rate of HCFC-142b over the LaF 3 catalyst. 6,38 Clearly, the conversion rate of HCFC-142b correlates with the acidic sites of metal fluorides. Consequently, the relationship between the amount of acidic sites and conversion rate was attempted, and the results are disclosed in Figure 7.…”

“…E slab,X , E slab , and E X are the energy of surface covered by X, the energy of the surface without X adsorption, and the energy of X, respectively. 38 Industrial Based on the approach developed by Reuter and Scheffler, 39 for the surface system, the surface free energy γ(T,P) in fluorine pressure p and temperature T is defined as…”

“…E slab,X , E slab , and E X are the energy of surface covered by X, the energy of the surface without X adsorption, and the energy of X, respectively …”

BaF(p-BDC)0.5 as the Catalyst Precursor for the Catalytic Dehydrochlorination of 1-Chloro-1,1-Difluoroethane to Vinylidene Fluoride

“…Although VDF can be produced via the dehydrofluorination of 1,1,1-trifluoroethane (HFC-143a) [6] or via simple co-pyrolysis of CHF 3 with CH 4 at elevated temperatures [7][8][9], the reaction conditions are rather harsh. Similarly, the co-pyrolysis of chlorodifluoromethane and methane also leads to the formation of VDF [10].…”