乙烯直接催化氧化合成醋酸I. 负载型Pd-杂多酸催化剂的组成

研究了负载型Pd-杂多酸催化剂对乙烯直接氧化合成醋酸的催化作用，由固定床反应器考评其催化性能，借助XRD对催化剂进行表征。结果表明以SiO

Direct Catalytic Oxidation of Ethylene to Acetic Acid I. The Composition of Loaded Pd-Heteropoly Acid Catalyst

The effect of Pd-HSiW-Cr-Te/SiO2 on direct oxidation of ethylene to acetic acid was researched in a fixed-bed reactor, and the catalyst was investigated by XRD. The results showed that Pd-HSiW-Cr-Te/SiO2 was an ideal catalyst for direct oxidation of C2H4 to acetic acid. Pd and HSiW were the necessary active components and had excellent effect, the suitable contents of them were wPd=0.03 and wHSiW=0.60(both based on carrier weight). In order to improve the catalytic performance of Pd-HSiW/SiO2, a series of promotors were studied. As a consequence, Te and Cr had excellent effect. By adding trace Te and Cr, the by-products CO2 and CH3CHO could be decreased greatly. The suitable contents of Te and Cr were Te∶Pd=1∶20 and Cr∶Pd=1∶30(atom ratio). It was discovered by XRD that on the catalyst there was an active structure between Pd and HSiW, and the form of Te and Cr was in oxidative state: Te2O5 and CrO2. When the reaction conditions were as follows: T=190°C,p=0.80MPa,SV=4 000h-1, and the composition of reaction mixture gas was C2H4∶O2∶N2∶H2O=50∶6∶14∶30(mol ratio). The catalyst had ideal catalytic performance: the conversion of C2H4 and the selectivity of acetic acid could reach 3.5% and 84.1% respectively, and the by-products CO2 and CH3CHO were 12.4% and 1.1%. The once-through space time yield of acetic acid could reach 157.8g/(L.h).