Preparation Of Biodiesel By Catalytic Esterification Of Carbon-based Solid Acid

Oil is a non-renewable energy source,with the acceleration of the world industrialization process and the reduction of oil reserves,Our demand for oil and imports are increasing.The development of biodiesel is conducive to economic development and national energy security.Compared with traditional petroleum,biodiesel has excellent properties,excellent starting feature,safety,good combustion performance,renewability,economy,adjustability and degradability.Among the various catalysts for the synthesis of biodiesel,carb on-based solid acid is a new type of highly usable solid acid mater ial.The raw materials for the preparation of carbon-based solid aci d include polycyclic aromatic hydrocarbons,carbohydrates,mesoporo us carbon materials.And biomass catalysts are simple to manufactu re,low in cost,large in specific surface area,high in catalytic perf ormance,good in stability,easy to recycle,less corrosive and easy to treat industrially produced wastewater,which has attracted wide a ttention of researchers.Biomass carbon-based solid acid is a new kind of solid acid m aterial,which is prepared by loading acid groups on the surface of carbon materials.Carbon materials used usually include glucose,st arch,cellulose,waste biomass,biomass wood flour and other macro molecular hydrocarbons,which are widely available,cheap,and can be planted according to local conditions.In this experiment,a biomass carbon-based solid acid catalyst was prepared by incomplete carbonization-sulfonation method using inexpensive and easily available potato powder and glutinous rice flour as raw materials,and it was applied to the esterification reaction of oleic acid with methanol to investigate carbonization.The effects of preparation conditions such as temperature,carbonization time,carbonization temperature,sulfonation temperature and sulfonation time on the conversion of oleic acid.The molar ratio of alcohol to oil,the amount of catalyst,the reaction time of esterification and the temperature of esterification were investigated by orthogonal experiment.The effect on the conversion of oleic acid and the kinetic parameters of the esterification reaction catalyzed by two catalysts were calculated.The results of research on potato powder carbon-based solid acid catalyst showed that the optimum carbonization temperature was 250°C,the carbonization time was 2 h,the optimum sulfonation temperature was150°C,and the sulfonation time was 2 h.Orthogonal experiments showed that the carbon-based solid acid catalyst prepared by carbonization-sulfonation method was characterized by XRD,SEM,FI-IR,BET,TG.The results showed that the catalyst was aromatic carbon.The amorphous carbon structure consisting of sheets has a lumpy,loose,and rough edge morphology.The catalyst has a polycyclic aromatic hydrocarbon structure and the sulfonic acid group has been successfully loaded.The pore structure of the catalyst is mainly mesoporous,which can provide a channel for the contact between the reactant and the active site,which is beneficial to the reaction.Between200-300°C,the carbonization facilitates is easy to Combine with polycyclic aromatic structure.The results of orthogonal experiment showed that the oleic acid conversion rate was the best at the esterification temperature of 65°C,the esterification time was 2.5 h,the ratio of alcohol to oil was 8:1,and the catalyst content was 7%.The catalyst after regeneration was repeated.After uses of 5 times,the oleic acid conversion rate can still reach89.56%.The kinetics of the reaction was calculated according to the differential method.The average reaction order of the reaction was 1.15,the activation energy was 3.99 kJ/mol,the frequency factor was 3.94,and the unit was mol^-0.15·L ^0.15·s^-1.The results of research on the carbon-based solid acid catalyst of glutinous rice powder showed that the optimum carbonization conditions were:temperature 300?,time 3 h;optimal sulfonation conditions:temperature 150?,time 3 h.Characterization by means of XRD,SEM,NH₃-TPD and other characterization methods showed that the degree of ordering of the carbon layer after sulfonation was reduced,and the degree of unoriented was increased.Under the action of H₂SO₄,the structural reorganization between carbon skeletons was caused.The-SO₃H functional group has been loaded onto the carbon support;the glutinous rice powder carbon-based solid acid has a random block shape and a certain pore size,which facilitates the diffusion of the reactant molecules in the catalyst.The results of orthogonal experiment showed that the oleic acid conversion rate was the best at the esterification temperature of 65°C,the esterification time was 5 h,the ratio of alcohol to oil was 10:1,and the catalyst content was 5%.The catalyst after regeneration was repeated.After uses of 5 times,the oleic acid conversion rate can still reach76.09%.The kinetics of the reaction was calculated according to the differential method.The average reaction order of the reaction was 1.17,the activation energy was 2.4 kJ/mol,the frequency factor was 2.26,and the unit was mol^-0.17·L ^0.17·s^-1.The triblock copolymer P123 was used as the template and the tetraethyl orthosilicate was used as the silicon source.SBA-15 and Cr-SBA-15 were synthesized by hydrothermal crystallization.The loading amount,calcination temperature and calcination time were investigated.The effect of acid conversion rate showed that the conversion of oleic acid reached 88.76%at 8%loading amount,calcination temperature 550°C and calcination time 3 h.The catalysts were characterized by XRD,SEM and NH₃-TPD.The results showed that the introduction of Cr ions reduced the order of the mesopores of SBA-15and caused the skeleton to shrink.After the modification of Cr,Irregular rice granules did not change the original morphology of SBA-15;after the introduction of chromium,the peak area increased,indicating a significant increase in acidity,indicating that chromium is the active center of the esterification reaction.The catalytic performances of the three catalysts in terms of catalytic effect,preparation conditions and reusability were compared.The results showed that using potato powder carbon-based solid acid as a catalyst,it can achieve higher conversion rate at the same time,cheap and easy to obtain and widely used,the cost is lower After 5 times of repeated experiments,the carbon-based solid acid catalyst is slightly better than the molecular sieve catalyst.