Study On The Preparation Of Porous Ni Catalyst And The Performance Of Oil Hydrodeoxygenation

The annual production of waste cooking oil?WCO?with significant waste and resource is very huge.If WCOcan'tbe effectively controlled and handled,it will pose a great threat to the environmental and to the food safety problems,mainly reflecting in the destructive pollution of the atmosphere,water,soil,as well as the return of WCO to the human body.WCO has rich C,H,and O elements,mainly composed of long chain(C₁₂-C₂₄)saturated or unsaturated esters.Making use of it in a right way can greatly alleviate the energy crisis and maintain the balance of ecological carbon.Producing biodiesel from WCO by hydrodeoxygenation technology is not only in line with the concept of contemporary green energy,but also contributes to the resourceutilization of waste,and realizes the transformation of waste into treasure.This paper is mainly fouce on preparing porous Ni based catalysts using the impregnation method,hard template method,soft template method,precipitation method,and complex method.Ethyl acetate and methyl laurate are used as model compounds to study the hydrodeoxygenation properties of porous Ni based catalysts.The physicochemical properties of the prepared Ni based catalysts were studied by H₂-TPR,H₂-TPD,XRD,BET,TEM,FT-IR,and in-situ XPS.Some conclusions can be drawn as follows:1.The influence of the metallic Ni loading amount on the hydrodeoxygenation performance of Ni/KIT-6 catalyst was investigated.It is found that changing the Ni loading amount can effectively improve the hydrodeoxygenation performance of the studied catalysts.The superior structure of KIT-6support promotes metallic Ni species to highly disperse,and the Ni/KIT-6 catalysts still maintain large specific surface area and developed pore structure of KIT-6.With the increase of the Ni loading amount,the specific surface area gradually decreases,and that the specific surface areaof the studied catalystsis above 375m²/g.The prepared catalysts can be effectively reduced in the high purity H₂ atmosphere at 450oC/2h,and the amount of the desorption of hydrogen species on the prepared catalysts can reach to 20.6?mol/g.Ni/KIT-6 catalyst has excellent activity hydrodeoxygenation at low temperature.Ethyl acetate can be completely transformed below 360oC,which is mainly related to the superior structure and rich chemical composition of the studied catalyst,and this reaction is a structure sensitive reaction.The NK25 catalyst with loading amount of 25 wt.%exhibited the best catalytic activity.Ethyl acetate can be almost completely converted at 300oC,at the same time,the selectivity of ethane reached to 96.8%.2.The Ni based catalysts prepared by different methods,the structure-directing agent is an important factor for the formation of pore,which has a significant effect on the pore structure and specific surface area of the prepared catalyst.The specific surface area of Ni-HT prepared by hard template and Ni-ST prepared using soft templateis 90.2and 45.4m²/g,respectively.The average pore size is 10.6 and 17.5nm,respectively.The Ni-PC prepared using precipitation methodand Ni-CA prepared using complexing method are mainly composed of dense structure,and the specific surface area is only11.2 and 2.4 m²/g,respectively.The prepared catalyst can be effectively reduced in the high purity H₂ atmosphere at 450oC/2h.The prepared catalysts are all metal Ni phases,which is beneficial for effective activation of H₂ and oxygen-containing functional groups.The specific surface area and the developed pore structure of the catalyst are also beneficial to the migration and diffusion of H₂ molecules in the pore structure.The amount of hydrogen species desorption respectively are:228,183,81 and 79?mol/g on Ni-HT,Ni-ST,Ni-PC,and Ni-CA.The catalyst has a large specific surface area,developed pore structure and rich surface chemical composition,which is an important factor for the superior hydrodeoxygenation performance of the studied catalyst.Ethyl acetate can be completely converted below 380oC,and the selectivity of ethane is over95%.Following arethe activity sequence of the studied catalysts:Ni-HT>Ni-ST>Ni-PC>Ni-CA.The activation energy of ethyl acetate hydrodeoxygenation on Ni-HT,Ni-ST,Ni-PC and Ni-CA catalysts is 68.52,82.84,94.11 and 101.76 kJ/mol,respectively.3.The Ni/?-Al₂O₃ catalysts were used to study the hydrodeoxygenation performance of methyl laurate,and the effects of metallic Ni loading amount,reaction pressure and H₂/Oil ratio on the reaction were also investigated.It is found that the amount of metallic Ni has a significant effect on the hydrodeoxygenation performance of the studied catalysts,owing to the number of active centers plays a decisive role in the catalytic reaction.Lower Ni loading may lead to fewer active centers,and higher Ni loading tends to cause the aggregation of Ni on the support surface,which will weak the catalytic hydrodeoxygenation performance.The amount of hydrogen species desorption is only 4.39mmol/g on 6NA catalyst.Higher loading is easy to cause the aggregation of Ni on the support surface,the pore structure is blocked,the specific surface area decreases,and the specific surface area of 14NA catalyst is only 131.3m²/g.The 10NA catalyst with loading amount of 10 wt.%has the best catalytic performance,mainly including hydrodecarbonylation,hydrodecarboxylation,hydrodeoxidation and cracking reaction.The products are mainly alkyl chain,alkane,hydrolysate and condensation product.At 400oC,the conversion of methyl laurate can reach to 91.9%,and the highest selectivity of C₁₁1 alkane can reach to 68.6%.