固体碱KF/MgFeLa的制备及其催化合成生物柴油

Preparation of the Solid Base KF/MgFeLa and Its Application in the Production of Biodiesel

采用均匀共沉淀法和水热法合成MgFeLa复合氢氧化物,然后焙烧得到MgFeLa复合氧化物,再通过浸渍法将KF负载在MgFeLa复合氧化物上,制得KF/MgFeLa固体碱催化剂,并将其应用于催化大豆油和甲醇合成生物柴油.利用XRD、FI-IR、氮气吸附脱附、SEM、TG-DTG、CO2-TPD等手段对催化剂结构进行表征,并考察不同反应条件对催化合成生物柴油的影响.研究结果表明:KF/MgFeLa固体碱催化剂存在弱、中、强碱性位点,KF/MgFeLa固体碱的平均孔径为3~10nm,孔体积为0.06~0.2cm3/g,比表面积为39~70 m2/g,且KF/MgFeLa固体碱形成了新的晶相LaOF和KMgF3,同时,由于碱性氟化物的存在,KF改性的MgFeLa复合氧化物的碱性强度得到了显著提高.在KF的负载量为10%,甲醇与大豆油的物质的量之比为20∶1,催化剂量为5%,反应温度为85℃,反应时间为4h的条件下,生物柴油的收率可达98.5%.并且,KF/MgFeLa固体碱催化剂具有良好的重复使用性,重复使用5次以后,生物柴油收率仍有79.1%.

MgFeLa composite hydroxide was synthesized by homogeneous co-precipitation and hydrothermal method,and then calcined to obtain MgFeLa composite oxide.The potassium fluoride supported on MgFeLa composite oxide was prepared by impregnation method.The prepared KF/MgFeLa solid base was used as catalyst for the synthesis of biodiesel.The XRD,FI-IR,nitrogen adsorption and desorption,SEM,TG-DTG and CO2-TPD were used to characterize the prepared catalyst.The effects of reaction conditions on the catalytic synthesis of biodiesel were investigated.The results showed that KF/MgFeLa solid base catalysts possessed weak,medium and strong basic sites.The average pore size of KF/MgFeLa solid base was 3~10 nm.The pore volume was 0.06~0.2 cm3/g.The specific surface area was 39~70 m2/g.Some new phases（LaOF and KMgF3）were formed on KF/MgFeLa solid base.The basicity of KF modified MgFeLa could be greatly improved due to the presence of alkaline fluoride.The maximum biodiesel yield of98.5% could be obtained under optimal conditions：10% KF loading amount,molar ratio of methanol/oil20∶1,5% catalyst account,reaction time 4 hat 85 ℃.Furthermore,the KF/MgFeLa solid base catalyst had good reusability.The biodiesel yield of 79.1% could be obtained in the fifth cycles.