Ru催化加氢选择性脱除F-T合成水相中的含氧化合物

摘要

Removal of oxygenates in aqueous phase product of Fischer-Tropsch (F-T) process was studied by the catalytic hydrogenation over supported Ru catalysts. The catalytic performance of several Ru catalysts supported on different metal oxides such as ZrO2, TiO2, SiO2 andγ-Al2O3 was investigated. In the catalytic hydrogenation processes, aldehydes, ketones and esters are more readily to be transformed than carboxylic acid and alcohol. The Ru/ZrO2 and Ru/TiO2 catalysts exhibited excellent hydrogenation activity, and under the conditions of 200℃, 9.8 MPa pressure and 3.0 h-1 WHSV, the carboxylic acids, aldehydes, alcohols, ketones and esters all are transformed to C1- C6 alkanes with overall conversion of above 92%. However, the Ru/Al2O3 catalyst displays the lowest activity towards alcohols with below 30% of conversion at the same conditions, although other oxygenates, including carboxylic acids, aldehydes, ketones and esters, are transformed with considerable conversion of above 87%, indicating that the Ru/Al2O3catalyst was of selectivity for the conversion of oxygenates and the most of alcohols can not be transformed. The results from H2-TPR and NH3-TPD reveal that the synergy between metal and alumina is conductive to the hydrogenation of carboxylic acids and inhibits the hydrogenation-decarbonylation of alcohols. On the contrary, the catalysts with weak metal-support interaction and low acidity improve the hydrogenation activity for carboxylic acids and alcohols. However, there was a good stability of 400 h for Ru/Al2O3catalyst, although the degeneration of catalytic activity was also observed after running 400 h. The results from X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 physisorption show that the change of textural and structural properties is the key factors for activity degeneration of Ru/Al2O3catalyst, because of the transformation ofγ-alumina to boehmite and of the great decrease of surface area from 197 m2·g-1 to 21 m2·g-1 and loss of porosity.%采用催化加氢技术脱除F-T合成水相中羧酸、醛、醇、酮、酯含氧化合物，考察了Ru/ZrO2、Ru/TiO2、Ru/SiO2和Ru/Al2O34种Ru催化剂的反应性能。相对于酸、醇，水中的醛、酮、酯更易被转化。其中Ru/ZrO2和Ru/TiO2具有良好的加氢脱羰活性，在200℃、9.8 MPa、3.0 h-1空速下，酸、醛、醇、酮、酯均转化为C1～C6的烷烃，总转化率达92%。同条件下，虽然Ru/Al2O3对酸、醛、酮、酯的转化活性较高（＞87%），但对醇的转化不到30%，具有选择性转化特点。H2-TPR和NH3-TPD结果表明，Ru/Al2O3催化剂的金属活性位与载体酸性位的协同作用有利于羧酸的加氢反应，能抑制醇的加氢脱羰活性；而金属-载体相互作用较弱和酸度较低的催化剂有利于羧酸、醇发生加氢脱羰反应。Ru/Al2O3催化剂运行500 h后失活，XRD、SEM和N2-物理吸附表明，载体结构物相和织构性质的改变以及活性组分的流失是导致催化剂失活的主要因素。