Regeneration of Activated Carbon Supported Gold Catalyst for Hydrochlorination of Acetylene

Jianfen Xi

Vinyl chloride monomer (VCM) is traditionally produced by mercuric chloride (HgCl2) catalysed acetylene hydrochlorination. However, Hg catalyst often deactivates rapidly, while also releasing Hg during the reaction, posing a severe threat to the environment and human health. Gold catalyst is regarded as the best of the alternatives. It exhibits much higher stability and selectivity compared to other candidate catalysts. However, it still deactivates during industrial application. Previous research suggests that the deactivation is caused by a combination of gold reduction and carbonaceous material occlusion of active sites. In this project, samples of industrially-spent gold catalyst were used for regeneration trials to comparatively investigate various regeneration methods. Four different methods are employed to reactivate the spent catalyst: employing two organic aqua regia methods (SOCl2/DMF, and SOCl2/pyridine), H2O2, and ozonation. The catalytic performance of regenerated samples was evaluated by observing the conversion of acetylene. A combination of characterization techniques was used to elucidate likely mechanisms of reactivation. Both the removal of carbonaceous substances and the oxidation of Au0 to Au3+ were variously observed in the restoration of active sites. Samples processed by SOCl2/DMF, ozone and H2O2 exhibited catalytic performance with ca.75% conversion of acetylene, which was comparable to the performance of fresh, industrially-produced Au catalyst. Although SOCl2/pyridine could oxidize Au metal, the high absorption of carbon was suggested as reducing the activity after regeneration. The catalytic performance is roughly unchanged when the Au3+ makes up 8.8% to 16.5% of the gold present. When the proportion of Au3+ exceeds 16.5%, the activity was observed to decrease to a minimum at 19.3%, before the performance recovered as the proportion further increased; suggesting there might be a threshold proportion of Au3+ for best performance. In terms of operation cost and general environmental friendliness, H2O2 regeneration was judged as the most promising for further development to industrial-scale application. Keywords: Regeneration, Gold-containing catalyst, Spent, Organic mixtures, Ozonation, Hydrogen Peroxide

Regeneration of Activated Carbon Supported Gold Catalyst for Hydrochlorination of Acetylene

Files and links (1)

Abstract

Details

Metrics