Study On The Heterogeneous Catalyst Used In Preparing Biodiese And Economic Assessment

At present, the whole world is facing the enormous challenge of lacking ofpetroleum energy sources and environment pollution, the world had paid attention tobiodiesel as a environmental friendly alternative fuel. Biodiesel produced bytransesterification of natural oil with alcohols is an environmental friendlyalternative fuel. With a traditional homogeneous acid/base catalyst, separatingtransesterification product with used catalyst is difficulty. Discharge of wastecatalyst induces environmental problems. Using heterogeneous base catalyst mayimprove the purity of products and avoid the problems of catalyst deposition.Researches of heterogeneous catalysts and relative catalytictransesterification reactions are meaningful for both the production and applicationof biodiesel.This paper researched the preparation of biodiesel by transesterification fromoils and methanol with solid catalysis. As an intermittent reaction, the preparedprocess was studied in a normal-pressure and high-pressure reactor, with thematerial of oils, methanol and catalysts such as metal oxides, complex oxides, CaOloaded by different potash. Then, different processes were simulated by chemicalindustry process simulation software, one of processes was carried out with theactivest heterogeneous solid catalyst prepared by us. And the results were used in economic assessment and feasibility analysis for each process.The experimental results indicated that CaO which were prepared bycalcination CaCO₃ at 950℃had higher activity than CaO which were prepared bycalcination CaCO₃ at 900℃and ZnO had no catalytic activity.Among Calcium mixed oxides, the Calcium and Silicon mixed oxide preparedin impregned processing had excellent catalytic activity in suitable conditions. Theyield of glycerin was up to 87.15% in the suitable reaction conditions. The suitablereaction conditions was: the reaction temperature was 60℃, the reaction time was 3h, the molar ratio of methanol to oil was 10, weight fraction of catalyst was 2%.Calcium mixed oxide prepared by different methods had an order of catalyticactivity: CaO/SiO₂＞CaO/Al₂O₃＞CaO/MgO＞CaO/La₂O₃, and impregnedprocessing＞mechanical processing.CaO loaded by different potash had an order of solid base-catalytic activity:KNO₃/CaO(mechanical processing)＞KNO₃/CaO(impregned processing)＞K₂CO₃/CaO(impregned processing)＞KF/CaO (impregned processing)＞K₂CO₃/CaO (mechanical processing)＞KF/CaO(mechanical processing). Amongthose, KNO₃/CaO had the most excellent catalytic activity on producing biodiesel,which prepared in mechanical processing, the yield of glycerin was up to 75.56% inthe suitable reaction conditions. The suitable reaction conditions was (with thecatalyst KNO₃/CaO): the reaction temperature was 60℃, the reaction time was 1.5 h,the molar ratio of methanol to oil was 12, weight fraction of catalyst was 3%.On the basis of the economic assessment of each processes, the followingconclusions were made. The solid base-catalyzed process using rapeseed oil (processâ… ) had the lowest total capital investment. Glycerine was a valuable by-product,which could add an appreciable credit to reduce the total manufacturing cost byapproximately 8%. Raw oil costs account for a major portion of the totalmanufacturing cost. Thus, reduction of the raw oil cost should be the first step inoptimizing the total manufacturing cost. As a result, although processâ… had thelowest cost requirement for building a biodiesel plant, it had a high manufacturingcost offsetting any economic advantage in terms of return on investment or biodiesel break-even price. The alkali-catalyzed processâ…¡required a treatment unit to wipeoff the alkali. The cost associated with this treatment unit led to a reduced economicfeasibility for processâ…¡. The alkali -catalyzed processes to produce biodiesel fromrapeseed dreg oil (processâ…¢) had lowest total manufacturing costs, but required apretreatment unit for rapeseed dreg. Based on after-tax rate of return and break-evenprice of biodiesel, the processesâ…¢were economically competitive alternatives tothe other processes for biodiesel production. Sensitivity analyses of differentprocesses for biodiesel production showed that plant capacity, the price of raw oiland the price of biodiesel were the major factors affecting the economic feasibilityof the biodiesel production.