Lei Yang,Shiyi Yu,Chong Peng,Xiangchen Fang,Zhenmin Cheng,Zhiming Zhou
A series of nonprecious monometallic Ni/AlSBA-15 and bimetallic Ni M (M = Zn, Ga, Cu, or Fe)/AlSBA-15 catalysts were prepared using a urea precipitation method and applied to the semihydrogenation of phenylacetylene. The catalysts were characterized by various techniques, showing that the Ni particle size of catalyst can be tuned by adjusting the Al content, and NiZn and NiGa supported catalysts exhibited geometric and electronic effects that originated from the bimetallic alloy. Among all the catalysts studied, NiZn 3 /AlSBA-15, with a turnover frequency of 10.89 s −1 comparable to that of precious Pd-based catalysts, presented the highest selectivity to styrene (90.3%) at nearly 100% conversion of phenylacetylene in semibatch operation. This catalyst was further evaluated in a continuous fixed-bed reactor for semihydrogenation of a model C 8 aromatic fraction of pyrolysis gasoline (a mixture of phenylacetylene, styrene, ethylbenzene and xylene), which aimed at assessing its practical application of recovering styrene from pyrolysis gasoline. The results showed that at complete conversion of phenylacetylene, the styrene concentration in the product was always kept at a stable level and higher than its initial concentration over 100 h of time on stream, demonstrating high selectivity and good stability of NiZn 3 /AlSBA-15. Finally, the application of NiZn 3 /AlSBA-15 was extended to other phenylacetylene derivatives.
Chemoselective hydrogenation of aromatic nitro compounds to the corresponding anilines is an environmentally benign technology for the production of key intermediates in manufacturing of pharmaceuticals, agrochemicals, dyes and fine chemicals. Non-noble metal Cu-based catalysts have been reported as a low-cost alternative but suffer from poor activity. Herein, by fabricating nickel oxide promoted Cu catalysts, a promoted activity was obtained in supported Cu-Ni bimetal catalyst system. Characterizations such as H 2 -TPR and XPS indicate a strong interaction between Cu and Ni, which contributes to its high activity and selectivity in hydrogenation of p -chloronitrobenzene ( p -CNB) to p -chloroaniline ( p -CAN). Control experiments suggest that either monometallic copper or pure nickel oxide is less active for the reaction but the interaction of NiO x with Cu generates much more active species, resulting in significantly improved catalytic reactivity and selectivity. The activity was found to be highly dependent on the contents of Cu 0 & Cu + in Cu-Ni bimetal catalyst, as the specific reaction rates for hydrogenation of p -CNB grew linearly with the increment of Cu 0 & Cu + loadings. Kinetic studies and in-situ DRIFTS of p -CNB imply the 10Cu-5Ni/AlSBA-R catalyst possesses good capacity for the activation of hydrogen and nitro group, leading to high p -CNB conversion and p -CAN production. The present work provides a good example for understanding the interaction between Cu and nickel oxides, and helps to develop highly efficient non-noble metal catalysts for selective hydrogenation of aromatic nitro compounds to corresponding anilines.
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