Sn改性Raney Ni催化分解N,N-二甲基甲酰胺的研究

为了研究Sn含量和还原温度对Sn-RaneyNi催化剂的物理化学结构和催化分解N,N-二甲基甲酰胺(DMF)活性的影响,利用沉淀法制备了一系列不同Sn含量的Sn-RaneyNi催化剂,采用N2物理吸附、X射线衍射(XRD)和氢气程序升温还原(H2-TPR)等方法对不同Sn含量和不同还原温度制得的Sn-RaneyNi催化剂的比表面积、物相组成和还原性能进行了表征。以N,N-二甲基甲酰胺(DMF)为模型化合物,对Sn-RaneyNi催化剂的催化分解活性进行了评价。XRD表征结果表明,n(Sn)/n(Ni)为0.1的催化剂分别在723K和823K下还原生成Ni3Sn4和Ni3Sn合金晶相;n(Sn)/n(Ni)为0.15的催化剂在723K下还原形成Ni3Sn2合金晶相。H2-TPR结果表明,Ni-Sn合金的形成削弱了Sn和Ni与氧的结合能,使得Sn和Ni的还原峰向低温移动。催化分解DMF实验结果表明,当n(Sn)/n(Ni)为0.1、还原温度为723K时,Sn修饰RaneyNi催化剂能够将高浓度DMF(5%(wt))完全分解(分解率达100%),氢气的选择性达到86.8%。

Catalytic Decomposition of N,N-dimethylformamide over Raney Ni Catalysts Modified with Sn

In order to investigate the effects of Sn content and reduction temperature on the physicochemical structure of Raney Ni catalysts modified with Sn and their catalytic decomposition performance for DMF, the Raney Ni catalysts with different Sn contents were prepared by precipitation method. N_2 physical adsorption, X-ray diffraction (XRD) and hydrogen temperature programmed reduction (H_2-TPR) were employed to characterize the BET surface areas, phase compositions and reduction behavior of the catalysts containing various Sn contents and reduced under different temperatures. Using DMF as model compound, the catalytic activities of the Sn modified Raney Ni catalysts were examined by the probe reaction of DMF decomposition. The XRD results show that the metallic alloy phases of Ni_3Sn_4 and Ni_3Sn are present in the catalysts with n(Sn)/n(Ni)= 0.1 and reduced at 723 K and 823 K, respectively; while metallic alloy phase of Ni_3Sn_2 is present in the catalyst with n(Sn)/n(Ni)= 0.15 and reduced at 723 K. H2-TPR results indicate that the reduction peak of Sn and Ni shift to lower temperature with the formation of Ni-Sn metallic alloy, which could be attributed to the decrease of the binding energies of Sn and Ni with oxygen. The DMF with high concentration (5%(wt)) in wastewater could be completely decomposed into inorganic molecules over the Sn modified Raney Ni catalyst with n(Sn)/n(Ni)=0.1 and reduced at 723 K, and the H_2 selectivity could reach 86.8%.