A ligand coordination approach for high reaction stability of an Au–Cu bimetallic carbon-based catalyst in the acetylene hydrochlorination process†
The research and development of a non-mercury catalyst for China's PVC (polyvinyl chloride) industry is extremely urgent. Gold (Au) loaded on activated charcoal (AC), as a potential novel catalyst with high activity, has been regarded as an ideal substitute for mercury. However, the deactivation of a gold catalyst caused by acetylene for long-term industrial applications is a big challenge. In this work, a new methodology of ligand screening and design for gold catalysis was constructed. Trichloroisocyanuric acid (TCCA) was proved to be an excellent ligand. Besides, copper (Cu) was added and proved to be a favorable synergistic metal so that the content of Au in the catalyst could be further reduced to 0.2 wt% (weight percentage). Experimentally, the best ratio of each component was optimized to be Au : Cu : TCCA = 1 : 5 : 20. The prepared 0.2 wt% Au catalyst had a conversion of over 98% with over 99% selectivity during 24 h operation under the temperature of 180 °C and GHSV (gas hourly space velocity) of 90 h−1. Then, an over 6800 h pilot trial has been carried out to demonstrate its promising capability for practical applications. Moreover, several characterization methods accompanied by DFT calculations were used, and it was proved that the high stability after TCCA introduction may come from its high ability to prevent high valence Au from being reduced and to inhibit the coking effect and that the electron interaction between Au and Cu could facilitate the dispersion of Au and lead to higher catalytic activity.