Study On The Preparation Of Unsupported Catalyst For Cyclohexylbenzene Via Selective Hydrogenation Of Biphenyl

Cyclohexylbenzene?CHB?is an important intermediate in chemical industry,which has a good prospect of industrial application.On the basis of previous research in a laboratory,a series of NiMoZr,NiMoCu,NiMoZn catalyst were synthesized.Effects of catalytic properties of unsupported catalysts were studied,and evaluated unsupported catalysts activities towards Biphenyl?BP?selective hydrogenation.Two kinds of NiMo catalysts were synthesized by chemical precipitation method and hydrothermal method,and the chemical precipitation method was selected as the synthesis method for subsequent catalysts.A series of NiMoZr catalyst was synthesized by chemical precipitation method.Results reveal that with the increase of amount of Zr content,nickel ammonium molybdate crystalline phase diffraction peak,presents the approximate amorphous structure and the surface area of NiMoZr precursor has increased.Through the introduction of the XPS characterization result,Mo⁵⁺/Mo⁶⁺relative atomic ratio has increased,so as to improve the degree of reduction of Mo species,consistent with TPR characterization results.NiMoZr catalyst showed high hydrogenation activity at low temperature,Ni:Mo:Zr=1.5:1:0.1catalyst under 70?,the conversion rate of BP was 99%,but the selectivity of CHB is poorer was 61%,by optimizing the process conditions,we can obtain higher BP conversion was94.2%,the selectivity of CHB was 88.8%.By chemical precipitation method,Cu was introduced into the NiMo precursor and obtained a different proportion of NiMoCu catalyst.Ni and Cu with similar ionic radius and lattice parameters,based on the same chip replace effect,Ni can be replaced by Cu in nickel ammonium molybdate,while maintaining the original nickel ammonium molybdate crystalline structure.The introduction of Cu changed the channel structure of the catalyst of NiMo,increasing the surface area of the NiMo catalyst,and the surface area and pore volume of Ni:Mo:Cu=1.5:1:0.1 catalyst reached the maximum up to 232 m²·g^-1 Due to the introduction of Cu,the morphology of the precursor of NiMo has been significantly changed.In the precursor of NiMo,there are clumps of aggregates,and in the precursor of NiMoCu,the particles are in the shape of a rod.The Ni:Mo:Cu=1.5:1:0.15 catalyst showed high biphenyl low temperature hydrogenation activity which the BP conversion was 97%,but the selectivity of CHB was 58%.A series of NiMoZn precursors were synthesized by a chemical precipitation method.Zn can also replace the Ni in ammonium molybdate,and the replacement process is reversible.When Zn content of the NiMoZn precursor is high,the surface area presents the trend of decreasing at first,and then increasing,decreasing in the end.Ni:Mo:Zn=1.5:1:0.4 catalyst are the largest on surface,up to 85 m²·g^-1,and the morphology of the flower structure is observed.XPS characterization results shows that the additions of Zn,promoting Mo species reduction,inhibit the reduction of Ni species at the same time.With results of the BP selective hydrogenation,Ni:Mo:Zn=1.5:1:0.4 catalyst maintaining high conversion rate,up to 96.6%,improving the selectivity of CHB at the same time,up to 90.8%.