Enhancement of Au/AC acetylene hydrochlorination catalyst activity and stability via nitrogen-modified activated carbon support

Abstract

Improving the durability of Au3+ catalyst is an important step in increasing its utility when performing catalyzed acetylene hydrochlorination. Using nitrogen-modified activated carbon (NAC) as support, Au/NAC1 catalyst demonstrated excellent activity and stability when compared with the undoped Au/AC1 under the conditions of 180°C and 1480h−1 of gas hourly space velocity (C2H2 based). Moreover, the Au/NAC1 catalyst delivered a stable performance during a 300h test with the conversion of acetylene and the selectivity of vinyl chloride both reaching more than 99.9% at C2H2 hourly space velocity 100h−1, which substantially exceeds the best results reported in previous literature. The removal of carboxylic groups from the activated carbon surface and the introduction of nitrogen atoms as anchor sites by thermal pretreatment with urea are preferential to stabilize the catalytic active Au3+ species and inhibit the reduction of Au3+ to Au0 in the preparation process of Au/NAC1 catalysts. In addition, increasing the electron density of Au3+ via electron transfer from nitrogen atoms to the Au3+ center can increase the adsorption of hydrogen chloride and inhibit the reduction of Au3+ to Au0 during acetylene hydrochlorination and hence improve the catalytic stability. The excellent catalytic performance of the Au/NAC1 catalyst demonstrated its potential as an alternative to mercury chloride catalysts for acetylene hydrochlorination.