The Direct Oxidation Of Ethylene Together In Acetic Acid: Catalyst Acidity And Carrier And Reaction Mechanism

The preparation conditions of catalyst have been optimized and the effects of acidity and support on the catalytic activity have been studied in this paper. It has been found that activity is higher when H2PdCl4 was used as precursor and reduced by H2/N2 at 300癈. It also has been proposed that the higher acidity of acid used in catalyst and the higher acidity of acid exhibited on support, the higher of catalytic activity. In all supports used in experiments, SiO2 is the best one.The mechanism of oxidation of ethylene to acetic acid when steam existed also has been investigated. The results reveal that the ethylene is oxidized to acetaldehyde first, and then acetaldehyde is oxidized to acetic acid; the reaction mainly takes place on the site where Pd and SiW12 interact each other; in catalyst Pd(0) is the main state of Pd which has activity.The none Pd-SiW12 based catalysts for the oxidation of ethylene to acetic acid have also been studied. It has showed that none Pd-SiW12 based catalysts are much less than Pd-SiW12 based catalysts on catalytic activity, therefore, it can be considered Pd is indispensable in high activity catalyst.