高分散固体碱高效催化制备无甘油生物柴油High efficient preparation of no-glycerol biodiesel catalyzed by high dispersion supported solid base

为实现无甘油生物柴油的高效制备，以共沉淀法制备的镁铝水滑石为载体，K2CO3溶液为浸渍液，通过等体积浸渍法制备高分散负载型固体碱催化剂，考察水滑石制备过程中金属盐种类以及物质的量比对其催化三组分（菜籽油、乙酸甲酯和甲醇）制备无甘油生物柴油性能的影响，并利用FTIR、XRD、TG、CO2-TPD、BET、SEM技术对催化剂进行表征。结果表明：以MgCl2和AlCl3为金属盐、镁铝物质的量比3∶ 1、K2CO3浓度2.0 mol/L、焙烧温度500 ℃条件下制备得到的固体碱为催化剂，在油酯醇物质的量比1∶ 1∶ 10、催化剂用量10%、反应温度60 ℃、反应时间15 min条件下，生物柴油的产率可达98%，产品性能指标均符合欧盟标准。催化剂表征发现以氯盐为金属盐制备的水滑石比表面积大，孔道结构丰富，暴露的碱性中心位点数目多。综上，金属盐种类对水滑石结构会造成影响，以MgCl2和AlCl3为金属盐制备的高分散负载型固体碱催化剂可高效催化油脂酯交换反应制备无甘油生物柴油。In order to produce no-glycerol biodiesel efficiently, a high dispersion supported solid base catalyst was prepared by equal volume impregnation method using MgAl hydrotalcite prepared by co-precipitation method as the carrier and K2CO3 solution as impregnating solution. The effects of type and molar ratio of metal salt on the catalytic performance of solid base in the preparation of no-glycerol biodiesel produced from tri-component (rapeseed oil, methyl acetate and methanol) were investigated. The catalysts were characterized by FTIR, XRD, TG, CO2-TPD, BET and SEM. The results showed that the solid base catalyst was prepared under the conditions of MgCl2 and AlCl3 as metal salts, Mg/Al molar ratio 3∶ 1, K2CO3 concentration 2.0 mol/L, and calcining temperature 500 ℃， and the yield of biodiesel was up to 98% and the biodiesel performance indexes met with EU standard under the conditions of oil/ester/alcohol molar ratio 1∶ 1∶ 10, catalyst dosage 10%, reaction temperature 60 ℃, and reaction time 15 min. It was found that the hydrotalcite prepared with chloride salt had large specific surface area and rich pore structure which provided more exposed basic center sites. In conclusion, the type of metal salt has greatly effect to the structure of hydrotalcite and the high dispersion supported solid base prepared with MgCl2 and AlCl3 can efficiently catalyze oil transesterification to prepare no-glycerol biodiesel.