Study On Solid Alkali Catalysts For Synthesis Of Biodiesel From Transesterification

With the rapid development of the global economy,the energy shortages and environmental pollution are increasingly serious and become a worldwide problem that most countries must be faced.At present,a better solution is to find ideas and the development of renewable,environmentally friendly alternative energy sources.Biodiesel technology has a rapid development in this background.Biodiesel,an alternative diesel fuel,produced by transesterification of lipin with alcohols,and has become more attractive recently because of its environmental benefits and safety in use.Transesterification is one of the most important methods for biodiesel systhesis.In this procedure,solid alkali catalysts has more advantages, such as easy separation,simple process.So it has important theoretical and practical significance to synthesis biodiesel from transesterification over solid alkali.In this cuntribution,as the first step the influnce of precursor,supporter,calcining temperature and loading on the procedure of supported solid alkali catalyst transesterification is investigated,in which soybean oil is selected as raw material and CaO is used as a catalyst active component.The results show that:catalyst performances better activity in the conditions that support precursor Ca(NO₃)₂ onto MgO carrier,active component load 14%, calcining temperature 600℃.In addtion,an optimal operation condition in aspect of methyl yield for the cases of soybean oil and tung oil as individual raw material.For the first case the optimal operation condition is molar ratio of methanol to oil 12:1,the amount of CaO/MgO1.2wt%,reaction time 2.5h,reaction temperature 65℃,yield of methyl reaches 93.7%;for the other case,molar ratio of methanol to oil 15:1,the amount of CaO/MgO1.2wt%,reaction time 3h,reaction temperature 65℃,as a result methyl yields 90.5%.As the second step,to overcome the disadvantage,such as poor cycle stability,of supported catalyst,a complex non-carrier solid alkali and magnesium oxide(CaO-MgO) catalysts are prepared successfully by frothing method,and it is used in the procedure of soybean oil transesterification for further investigation.As a result,96.5%yield of methyl can be achieved under the optimum reaction conditions:molar ratio of Ca:Mg=1:1 in the catalysts, molar ratio of methanol to oil 12:1,the amount of CaO-MgO1.2wt%,refluence time 2.5h, reaction temperature 65℃.Compare to the supported catalyst the non-carrier catalyst is more active and more stabile,moreover it performances anti-poisoning ability.