| Carbon materials are, in general, very good absorbents of microwaves, which are easily heated by microwave radiation. In this paper, we use carbon materials as support for Pt catalyst to enhance the dehydrogenation of decalin under microwave heating.Firstly, we investigated the ability of different carbon materials absorbing microwave and transforming into heat in the liquid decalin, and the effect of pretreatment with low concentrations of acid and alkali on this ability. The CNTs were found to be the best microwave absorber. It can heat up the reactants to boiling point in2min under microwave radiation. The pretreatment have no obvious influence on the absorbing capacity of carbon materials. Microwave heating is preferable than conventional heating for this reaction.Several methods were used to cut CNTs. The microwave absorbing abilities were studied after cutting and the result showed that oxygen-contained functional groups introduced by partial oxidation would reduce this ability. However, catalytic oxidation had no bad effects on the absorbing microwave as carbon can be totally oxidized into CO2at certain sites, but the residual metals were detrimental for dehydrogenation. It was observed that the more the Pt particles were introduced inside CNTs, the worse the catalytic activity would be, which may contribute to the strong adsorption of H2on CNTs.The conditions of conventional and microwave assisted EG process to prepare5%Pt/CNTs were optimized. Temperatures, duration of heating, stirring speed were investigated for the conventional heating process. A yield of644.02mol H2/mol Pt in2h was achieved under the optimized reduction conditions. Meanwhile, mode and duration of microwave heating, pH values, ratio of CNTs and ethylene glycol were also studied for microwave assisted EG process. Excellent activity was observed for the catalyst reduced by consecutive microwave heating for2min with a real Pt loading of3.25%, yielding800.80mol H2/mol Pt in2h. Microwave assisted EG process was preferable in both energy consumption and catalytic activity. |
