Fabrication Of Supported NiCu Nano Alloy Catalysts For Semi-hydrogenation Of Alkynes

Alkene industry is the heart of the petrochemical industry, which occupies the crucial position in national economy. Typically, more than 70% of the total petrochemical products are using ethene as raw material.Generally, ethene is obtained from cracking of napltha, in which the generation of 0.5%-2% acetylene is inevitable. Trace amount of acetylene could poison the catalyst employed in polymerization process as well as decrease the quality of the product, and therefore it must be reduced to at least 5 ppm. Semi-hydrogenation of acetylene by Pd-based catalysts has been largely applied in industry. However, since the severe shortage of the precious metals resources, Ni has been frequently explored to replace Pd in this process owing to the preferable activity. However, compared with Pd, the most crucial issue of Ni-based catalysts is their poor selectivity and stability. Carbon related species could block the active sites on the surface of pure Ni and consequently lead to the deactivation.Therefore, the enhancement of selectivity and anti-coking ability in Ni-based catalyst with simple and green strategy is significant.Active component by alloying with second metal is one of the most efficient approaches to improve the catalytic properties. In this paper, two strategies were proposed to build high-dispersed NiCu nanoalloy catalysts,and then the catalysts were applied to discuss the impact of structure of active components on the performances of catalyst. We hope the catalytic properties could be effectively improved by utilizing the synergistic interaction in nanoalloy compounds.The preparation methods of catalysts were discussed. Based on the cation-tunability and lattice orientation effect of layered double hydroxide?LDH?, Ni and Cu were simultaneously introduced in to the layer of LDH to synthesize quaternary NiCuMgAl-LDH which was then used as precursor to obtain high-dispersed NiCu nanoalloy catalyst. For comparison, NiCu bimetallic catalyst was also prepared by co-impregnated method. The focus of this study was on revealing the influence of the different preparation methods on the degree of alloying in bimetallic catalysts, and therefore catalytic performance in semi-hydrogenation of alkynes was investigated. Experimental results showed that the catalyst synthesized by LDH precursor method?L-NiCu/MMO? possessed nanoalloys structure, while I-NiCu/MMO prepared by co-impregnation method possessed the mixture structure of monometallic Ni and Cu. In semi-hydrogenation of acetylene, higher catalytic activity, selectivity and stability in L-NiCu/MMO catalyst were exhibited. Preferable catalytic properties were contributed by the high dispersion and the intimate interaction of NiCu nanoalloy as well as the net trapped effect of support.The crystal plane effect of supports was discussed. In 'this section,CeO₂ nanocrystals with different morphologies and crystal planes were fabricated and used as supports to prepare series NiCu/CeO₂ catalysts.The focus of this study was on revealing the influence of support crystal plane effect on the structure of NiCu bimetallic, and therefore catalytic performance in semi-hydrogenation of alkynes was investigated.Experimental results showed that when the CeO₂ supported possessed nanopolyhedrons morphology, NiCu catalyst exhibited homogenous nanoalloy structure. Meanwhile, the existence of SMSI effect in NiCu nanoalloy catalyst could be beneficial for the nanoparticles anchor and encapsulation on the surface of support. In semi-hydrogenation of alkynes,higher catalytic activity and selectivity in NiCu nanoalloy catalyst were exhibited. The high dispersion was contributed to the improvement of activity, while the enhancement of selectivity was due to the electronic effect among Ni, Cu and CeO₂.