Evolution of Lewis acidity by mechanochemical and fluorination treatment of silicon carbide as novel catalyst for dehydrofluorination reactions

Abstract

Transforming potent greenhouse gasses, hydrofluorocarbons (HFCs) to hydrofluoroolefins (HFOs) is an environmentally friendly and low energy input route compared with traditional incineration method. During the conversion process, Lewis acidity of the catalysts play a vital role in the activity. Here, inspired by the fluorinated metal oxide, a novel nonmetallic catalyst SiC was fabricated via sequentially mechanochemical treatment and fluorination. With series characterizations, it demonstrated that on the super surface of SiC, there are thin layers of graphite, COOH species, SiO2 and Si4C4-xO2 substrates. Through the mechanochemical treatment, the layers of graphite, COOH species and partial SiO2 could be grinded off. Hence, the exposed SiO2 residue could be removed via the fluorination by HFC-152a and HF forming volatile SiF4. At the same time, the transition layer, Si4C4-xO2 was fluorinated to Si4C4-xF2 accompanied with enhanced Lewis acidity. As a result, the activity of the treated SiC was significantly superior than the unmilled SiC. These findings provide a feasible way to develop the catalytic performances of nonmetallic catalysts for the dehydrofluorination.