生物质副产物粗甘油制备丙烯酸

Conversion of biodiesel-derived crude glycerol into acrylic acid

以粗甘油为原料,采用新型负载型杂多酸催化剂和氧化物催化剂,通过两段反应制备丙烯酸。利用BET、NH_3-TPD、FTIR和原子吸收光谱分析等方法分析了粗甘油中不同杂质的影响。实验结果表明,粗甘油中的无机盐离子是造成粗甘油脱水产物丙烯酸收率降低、乙酸收率增加的主要原因。Na^+和K^+等碱金属杂质沉积在HPW/Cs-SBA催化剂表面,导致催化剂的比表面积和孔体积显著降低,平均孔径增大,催化剂上大量的中强酸性位点转化成弱酸性位点,酸性位点的总量也有所下降。只需对粗甘油进行脱盐处理,而不需要脱除其他有机物杂质即可用于脱水制备丙烯酸,反应70 h内丙烯酸收率稳定在86%左右,与使用精制甘油时的效果相当。

Acrylic acid was prepared by dehydration-oxidation of crude glycerol on heteropoly salt and mixed oxides.The influence of the crude glycerol impurities on reaction result,catalyst property and acidity,and acrylic acid yield were studied by BET,NH3-TPD,FTIR and atomic absorption spectrophotometry.Among all the impurities,only the alkaline metal ions in crude glycerol significantly decreased the yield of acrylic acid and increased the yield of acetic acid.The alkaline metal ions such as Na~＋ and K~＋ deposited on the catalyst,decreased the surface area and the pore volume,increased the pore size,converted the medium acid sites on the dehydration catalyst to weak acid sites,and significantly decreased acid site amount and strength.After desalination of the plant crude glycerol with ion-exchange resin to remove the critical impurities,the sequential dehydration and oxidation system gave 86% acrylic acid yield,which was as high as that with pure glycerol.Both the HPW/Cs-SBA and VMo-Si C catalysts were stable for at least 70 h.