Publication Catalysis 2010
A. C. Gluhoi, J. W. Bakker, B. E. Nieuwenhuys, Catal. Today 2010, 154, 13.
The hydrogenation of C2H2 in the presence and the absence of C2H4 has been studied over un-promoted and promoted Au/Al2O3. A no. of parameters have been varied: the Au particle size, the pre-treatment conditions (hydrogen vs. oxygen) and the nature of the promoters. Promoters include ceria, lithium and barium oxides. Our results show that hydrogenation of C2H2 proceeds with 100% selectivity towards C2H4, both in the presence and the absence of C2H4. Moreover, there is a strong dependence of the catalytic performance on the size of the Au particles: Au particles below 3 nm enhance the C2H2 conversion both in the absence and the presence of C2H4, without decreasing the selectivity to C2H4. Furthermore, metallic Au and Ce4+ appear to be more effective than Au3+ and Ce3+.
Our findings also indicate that Li2O has a beneficial effect on C2H2 conversion, while BaO has a slight detrimental effect, both having no influence on the selectivity to C2H4. The key to 100% selectivity to C2H4 resides in non-competitive adsorption of C2H2 and C2H4 on the Au surface when both hydrocarbons are present in the feed. The deactivation during C2H2 hydrogenation is a reversible process and is due to accumulation of C deposits on the catalyst surface, as result of C2H2 adsorption on different active Au sites. These deposits can be easily burned off by a thermal treatment in oxygen.