The Study On The Dehydrogenation Of Cyclohexanol Performance Over Complex Oxides Of Copper-Based Catalysts

Cyclohexanone is a kind of important organic chemical intermediates for the production of caprolactam(CPL)、adipic acid(AA)etc, It has good emulsifying ability as the solvent of paint, varnish and shellac; Cyclohexanone is also an important intermediate of pharmaceutical and fine chemicals synthesis. Among them, caprolactam and adipic acid which made of Cyclohexanone are also used to making fiber nylon-6and nylon-66’s monomer. Therefore, the development of cyclohexanol and cyclohexanone industry relies on the development of caprolactam and adipic acid industry and its development of prospects is more promising.The reaction of cyclohexanol dehydrogenation to cyclohexanone is an important industrial reaction, except the main dehydrogenation reaction, there are some dehydration and aromatization side reaction. The copper-base catalyst showed better catalytic performance in the reactin of cyclohexanol dehydrogenation to cyclohexanone. Compared with the traditional catalyst, the copper-based catalyst has some characteristic such as low reaction temperature、 less by-products、low energy consumption and so on, thus it becomes the focus of research in recent years.In this paper, on the basis of the synthesis of copper-based complex oxide catalysts, some different copper-based catalysts was prepared, And they were applied to cyclohexanol dehydrogenation reaction, the study mainly include the carrier of catalysts、the main active component of catalysts、different ratio between components、add some surfactant in the process of catalyst preparation、 the effect of reduction conditions with surface structure and catalytic properties, In combination with the catalytic activity in the reaction of cyclohexanol dehydrogenation to cyclohexanone.Zn-Al2O3catalyst、Cu-Al2O3catalysts、Cu-Zn-Al2O3catalyst were synthesized by constant pH value coprecipitation method, and research their catalytic activity on cyclohexanol dehydrogenation to cyclohexanone, the catalytic activity sequence:Cu-Zn-Al2O3>Cu-Al2O3>Zn-Al2O3, the experimental data show that metal Cu-Zn-Al2O3catalyst and Cu-Al2O3catalyst’s catalytic activity are better than Zn-Al2O3catalyst, the three catalysts’s main active component is metal Cu and Zn, but metal Zn shows activity only at low high temperature, which range is360℃～450℃. Therefore, cyclohexanol dehydrogenation to cyclohexanone mainly used copper as the main active component.This paper mainly sutdy the active component of metal Cu with the different carrier copper-based catalyst, Cu-y-Al2O3catalysts、Cu-SiO2catalyst、 Cu-Zn-Al2O3catalysts were synthesized by constant pH value coprecipitation method and impregnation method catalytic, the cyclohexanol dehydrogenation to cyclohexanone catalyst sequence:Cu-Zn-Al2O3>Cu-γ-Al2O3>Cu-SiO2, the experimental data indicate that Cu-γ-Al2O3catalysts、Cu-SiO2catalysts may has poor dispersion of the Cu component during the preparation of catalyst, It cause the part of the Cu components sintering during the reduction process and generate carbon deposition in the process of reaction, finally resulting in inactivation of the Cu component. And Cu-Zn-Al2O3catalysts exhibit good catalytic activity in the catalytic process, because the metal Cu has high dispersion and thermal stability, Finally cyclohexanol dehydrogenation to cyclohexanone should add some metal Zn as dispersion and Cu as the carrier.Regular structure, high crystallinity of different ratio of CuZnAl-HTLcs were synthesized by constant pH value coprecipitation method, its derivative complex oxide were created by the precursor CuZnAl-HTLcs calcined, then the derivative complex oxide as a catalyst for the cyclohexanol dehydrogenation reaction, the catalytic activity sequence:Cu1.00Zn1.00Al1.00>Cu1.25Zn1.00Al1.00> Cu1.75Zn1.00Al1.00(approach tomaterialCu1.50Zn1.00Al1.00)>Cu0.75Zn1.00Al1.00> Cu0.50Zn1.00Al1.00, and when the component ratio of Cu-Zn-Al2O3catalyst is n(Cu)/n(Zn)/n(Al)=1:1:1, the reaction temperature is260℃, the cyclohexanol conversion rate is65.76%, the cyclohexanone selectivity is nearly99.48%. the catalyst has the synergism effect between Cu and Zn, Al2O3as the carrier, with the Cu content change, the synergism effect between Cu and Zn and dispersion are different. Therefore, when the component ratio of Cu-Zn-Al2O3catalyst n(Cu)/n<Zn)/n(Al)=1:1:1,it has better catalytic activity.The component ratio of Cu-Zn-Al2O3catalyst n(Cu)/n(Zn)/n(Al)=1:1:1were synthesized by constant pH value coprecipitation method, The effects of reduction conditions on catalytic performance were investigated in detail. The catalysts have been characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD), BET-surface area measurements(BET). For Cu-Zn-Al2O3catalyst, the conversions of cyclohexanol is nearly67.59%, the selectivity of cyclohexanone is almostly100%under the conditions:reaction temperature of250℃, the liquid flow rate was0.5mL·min-1, reduction temperature of260℃, reduction time of2hours.In the process of preparation of CuZnAl-HTLcs which were synthesized by constant pH value coprecipitation method, add a certain amount of surfactant lauric acid, according to the critical micelle concentration of surfactant lauric acid, firstly, the catalyst with the different molar ratio of lauric acid and metal ions in solution were synthesized, and investigated their catalytic activity, secondly, the catalyst of different n(Cu+Zn)/(Cu+Zn+Al) ratio were synthesized, and investigated their catalytic activity, finally, the experimental data show when n (lauric acid)/n(Cu+Zn+Al)=7:100, n(Cu+Zn)/n(Cu+Zn+Al)=3:10, the conversion rate is up to71.15%of cyclohexanol and cyclohexanone selectivity is nearly99.26%. It mainly largely improve the surface area of the Cu-Zn-Al2O3catalyst, promote the dispersion of active metal component in the catalyst surface, increases the contact area between the catalyst and the reactants cyclohexanol, makes the full reaction.