生物柴油副产物粗甘油催化氧化脱水制备丙烯酸

用生物柴油副产物粗甘油催化氧化脱水制丙烯酸，该过程耦合了甘油脱水制丙烯醛和丙烯醛选择性氧化制备丙烯酸两步反应。结果表明，在甘油脱水反应中，使用Cs3PW12O40, P-ZSM-5和Co0.5H2PO4/SiO2等固体酸催化剂，可得到较高的丙烯醛收率(最高86.9%)。利用上述催化剂和MoVW基氧化催化剂，在脱水/氧化双催化剂床层构型反应器中，以甘油为原料合成丙烯酸的收率达50%~80%，直接加入粗甘油可获得相似的丙烯酸收率。

Value-added utilization of crude glycerol from biodiesel production: catalytic oxydehydration to acrylic acid

Since the biodiesel boom in the past ten years, glycerol became considerable oversupply in the market, as the main byproduct in biodiesel production through transesterification process. As a result, in recent years there have been intensive efforts devoted to convert glycerol to other value-added chemicals. The selective catalytic oxydehydration of glycerol to acrylic acid is an efficient way for value-added utilization of crude glycerol from biodiesel production. It couples glycerol dehydration to acrolein and acrolein oxidation to acrylic acid. Acrylic acid is a key feedstock for commodity acrylate esters and various functional polymers. This process allows producing acrylic acid from low-cost and renewable biomass resources instead of traditional crude oil feedstock. For developing this novel process, both catalyst (dehydration and oxidation) and technology are crucial in improving acrylic acid. In this study, some solid acid catalysts, such as Cs3PW12O40, P-ZSM-5 and Co0.5H2PO4/SiO2 were found to show high acrolein yield in glycerol dehydration at 300℃. The acrolein yield increased from 60.4% to 77.7% with respect to carrier gas (N2) flow rate on the Cs3PW12O40 catalyst. The acrolein yield went down from 75.0% to 65.8% when increasing P concentration from 2wt% to 20wt% over the phosphorous modified ZSM-5 catalysts. The 30wt% Co0.5H2PO4/SiO2 catalyst also showed excellent activity in dehydration of glycerol to acrolein. Nearly 80% of acrolein yield was obtained under 20 mL/min N2 flow rate. Interestingly, the acrolein yield increased to 86.9% when changing carrier gas to 20vol% O2/N2 with 25 mL/min flow rate. Using these catalysts and MoVW-based oxidation catalyst, the acrylic acid could be produced from glycerol with yield of 50%~80% with a dehydration/oxidation double catalyst bed configuration in one reactor at the same reaction temperature. Similar acrylic acid yield was obtained when feeding crude glycerol directly. The acetic acid and CO/CO2 were the main by-products for both reactions. The addition of methanol, NaCl, or NaOH to the glycerol feeding solution would reduce the acrolein yield for glycerol dehydration reaction. These additives are the general impurities in crude glycerol sample.