The Silica-pillared Clay(SPC)Supported Metal Catalyst:Synthesis Characterization And The Catalytic Performance

Catalytic hydrogenation,such as unsaturated organic substances,environmental pollutants and new energy sources,is one of the key technologies in the petrochemical industry,which has been paid much attention by all people in earth.Supported metal catalysts have become an important part of catalytic hydrogenation industry for its high stability,catalytic activity,selectivity and reusability.Nickel-based catalyst,as a member of the catalytic family,is very cheap and possess excellent hydrogenation activity.Therefore,in terms of precious metals,supported nickel catalysts are more widely used in industrial applications.Natural montmorillonite,possessing a typical 2:1 configuration layered structure,inter-layer ion exchange,expansibility,hydrophilicity and the domestic reserves rich and productive,is a kind of inexpensive industrial raw materials.However,the natural montmorillonite spacing is too low,not enough to meet the needs of the industry,and its modification has become an effective way to solve the problem.In this paper,natural montmorillonite was used as experimental material.Under the suitable experimental influence elements,such as alkalinity,reduction time,metal content,reducing dose and PVP addition amount,The supported nickel montmorillonite supported nickel catalyst and nickel molybdenum catalyst were successfully synthesized by liquid phase reduction method.Furthermore,the hydrogenation performance of materials for chlorobenzene and phenol was investigated.1.The silicon pillared montmorillonite supported nickel catalyst Ni/SPC was prepared by liquid phase reduction method with hydrazine hydrate as reducing agent and polyvinylpyrrolidone(PVP)as nano-particle protective agent.The effects of the addition of PVP on the catalyst surface nanoparticles were investigated by XRD,HRTEM,BET,XPS,NH3-TPD and other analytical methods.The results show that the introduction of protective agent PVP makes the nano-particles in catalyst surface have good dispersion,uniform size and controllable size.Ni particle size is inversely proportional to the amount of PVP introduced.On the other hand,NH3-TPD indicates that Ni/SPC contains more active sites in the strong acid,which is beneficial to enhance the hydrogenation activity of the catalyst.2.Based on the research results of silicon pillared montmorillonite supported nickel catalyst(SPC),we continued to investigate the effects of different impregnation order,different metal additives and different Mo introduction conditions on the Ni-Mo/SPC structure and catalytic activity by XRD,HRTEM,XPS,and other characterization methods.The results show that Mo exists mainly in tetravalent and hexavalent form in the catalyst,while Ni is present at zero and bivalent.The introduction of Mo makes the catalyst Ni-Mo/SPC metal particles continue to decrease by about 1 nm on the basis of Ni/SPC,which further enhances the dispersibility of the acidic active sites.3.The optimum conditions for the chlorobenzene hydrodechlorination performance of catalyst Ni/SPC were obtained by the catalytic evaluation process.When environmental conditions are:603 K,3 MPa,and the PVP/Ni mass ratio is 1.33,the conversion can be up to 92%,at the same time,the selectivity for C6H6 of the catalyst is more than 96%.Compared with Ni/SPC without PVP,the introduction of PVP increases the dispersion of the active center of the catalyst,which makes it more difficult to agglomerate in high temperature and high pressure environment.4.The catalyst Ni-Mo/SPC has achieved excellent catalytic effect in the hydrodeoxygenation of phenol.At 623 K and 4 MPa,when the molar ratio of Ni/Mo is 2,the conversion rate of phenol to catalyst is up to 98%,and the product deoxidation rate is even 100%.In order to investigate the recycling efficiency of the catalyst,HRTEM analysis was carried out to analyze the microstructures of catalytic samples after different cycles.It was found that the size of the nanoparticles in the catalyst was 6.14 nm after four cycles,which was about 2.5 nm higher than that of the catalyst after one cycle.It indicates that the continuous high temperature and high pressure conditions lead to agglomeration of the catalyst metal particles,and thus the catalytic activity decreases with the increase of the number of recycling times.