Study On Synthesis Of Heterogeneous Catalyst Supported Mo And Catalytic Performances In Biodiesel Production From Jatropha Curcas Seed Oil

Biodiesel has become one of the most potential renewable energy sources to replace petrochemical diesel beaucase of its economy,safe and sustainable for the past few years.Jatropha curcas seed oil(JO)is a cheap,resource-rich and non-edible vegetable oil which has great potential and advantage as a raw material for the production of biodiesel via the transesterification process.Considering the high acid value of JO,the acid-catalyzed transesterification was employed to prepare biodiesel.In recent years,supported solid acid catalyst has attracted much attention and become hot research topics for many traditional reactions,attributing to the good properties such as high catalytic activity,strong designability,non-corrosiveness,easy separation and reusability.As we all known,the catalyst performance can be improved by the adjustment of the surface nature and the support structure,a series of high-performance Mo-base solid catalysts have been synthesized and applied in the transesterification of JO.In addition,all the catalyst samples have been systematically characterized through XRD,Raman,N₂ adsorption,FT-IR,NH₃-TPD,Py-IR,SEM,TEM,ICP and XPS,the micro-morphology,chemical composition,crystal structure and surface properties of these catalysts were carefully analyzed.Furthermore,the reaction conditions for the production of biodiesel were optimized by using single-factor test.(1)A series of x SO₄^2-/Ti O₂ catalysts were prepared by impregnated with different H₂SO₄ concentration on the Ti(OH)₄ support,,and their catalytic activity were tested in the transesterification of JO.Furthermore,combined with active data and catalyst structure informations,the mechanism of the SO₄^2-/Ti O₂ catalyzed transesterification was proposed.Finally,the optimal process conditions of this transesterification were:H₂SO₄ concentration was 1.5 mol L^-1,reaction time was 24 h,JO:methanol:petroleum ether was 3:2:1(mass ratio),catalyst content was 4 wt%,reaction temperature was 120?and rotation speed was600 rpm.Unfortunately,the reusability of the catalyst is poor,JO conversion of only 25%after 5 cycles,owing to the partial loss of sulfonic acid groups during the reaction.(2)Mo/SO₄^2-/Ti O₂ catalyst was successfully synthesized through incipient-wetness impregnation method.The characterization of XRD,Raman,ICP,TEM-mapping and XPS show that Mo species are well dispersed on the surface of the SO₄^2-/Ti O₂ support in the form of Mo⁶⁺oxidation state.And this catalytic mechanism was also clarified based on the Mo⁶⁺catalytic active center.However,the acidity was significantly reduced due to the partially shed sulfonic acid group resulted from the competitive coordination with the hydroxyl group between the Mo species and the sulfonic acid group.Nevertheless,the activity of the catalyst in the transesterification was greatly improved after the introduction of Mo species,and the JO conversion increased by 32.4%using the Mo-loading of 10 wt%.Moreover,the reusability of Mo/SO₄^2-/Ti O₂ catalyst was excellent,which the JO conversion decreased only by 14.1%after 5 cycles and the catalytic active could be recovered via high-temperature calcination.Additopnally,the optimal process conditions were as follows:reaction time was24 h,JO:methanol:petroleum ether was 3:1:1(mass ratio),catalyst content was 3 wt%,reaction temperature was 120°C and rotation speed was 600 rpm.(3)A series of x Mo/Na Beta catalysts were prepared by using Na Beta zeolite as a support containing many mesoporous structure and high specific surface area.The JO conversion was highest and reached 84.1%over 7Mo/Na Beta catalyst.The catalyst structure,surface morphology and chemical composition were systematically characterized by various analysis methods,which proved that the highly dispersed Mo species(Mo⁶⁺oxidation state)were the main reason for the improving of activity,and the corresponding probable mechanism was further explored.Furthermore,the JO conversion decreased only by 20%after 5 runs and the catalytic activity was restored partially after calcination at high temperature,which demonstrated the good stability of Mo/Na Beta catalyst due to the stable interaction of Mo species and Na Beta support.Finally,the optimal process conditions for the transesterification catalyzed by Mo/Na Beta were as follows:reaction time was 20 h,JO:methanol was 3:1.5(mass ratio),catalyst content was 4 wt%,reaction temperature was 110?and rotation speed was 600 rpm.(4)In order to study the effect of the support structure on the performance of the catalyst for the transesterification of JO,7Mo/S-1,7Mo/MS-1,7Mo/TS-1,7Mo/MTS-1,7Mo/Na Beta,7Mo/MCM-41 and 7Mo/Al₂O₃ catalysts have been synthesized with different supports.The results show that the 7Mo/S-1 catalyst exhibited the highest catalytic activity,which the JO conversion could reach 95.7%.Furthermore,the 7Mo/S-1 catalyst also showed excellent stability,after 5 runs,the JO conversion decreased by only 18%and the catalytic activity was partially restored after calcination.Various characterization of the catalysts were systematically analyzed,it was found that the support,with large external surface area and a large number of hydroxyl groups,is benefit to prepare the high activity Mo-based catalyst for the transesterification reaction.Finally,the process conditions obtained from the transesterification catalyzed by 7Mo/S-1 were:reaction time was 20 h,JO:methanol was 3:3(mass ratio),catalyst content was 0.12 g,reaction temperature was 110?and rotation speed was 600 rpm.(5)The physicochemical property of as-synthesized biodiesel from JO,such as density,acid value,iodine value,flash point,kinematic viscosity,moisture content,ash content and ester have been measured through GB methods.Comparing with international standards,it is demonstrated that the various indicators of synthetic biodiesel are matched with the standard,indicating that the prepared biodiesel in this study has good application and development prospects in industry.