Ca-γ-Al_(2)O_(3)耦合酸溶液催化葡萄糖制5-HMF

Catalytic Dehydration of Glucose to 5-HMF by Ca-γ-Al_(2)O_(3) and Acid Solution

针对以葡萄糖为原料制备5-羟甲基糠醛(5-HMF)的问题,开发了CaO杂化的γ-Al_(2)O_(3)球形颗粒[Ca-γ-Al_(2)O_(3),粒径1.8(±0.1)mm]耦合酸溶液制备过程,采用XRD与BET对Ca-γ-Al_(2)O_(3)球形颗粒进行了表征,研究了CaO杂化量、溶剂酸浓度、溶剂中二甲基亚砜(DMSO)与水的比例、催化剂用量、反应温度与时间对反应效果的影响,并评价了Ca-γ-Al_(2)O_(3)的操作稳定性,探讨了催化机理。实验结果表明:CaO的杂化(杂化量≤10%)对颗粒的孔结构影响相对较小,且在Ca-γ-Al_(2)O_(3)上分布较为均匀。在0.05 mol·L^(-1)酸浓度、V(DMSO)/V(H_(2)O)=3∶1、葡萄糖与催化剂比例为2∶1(125 mg∶63 mg)、反应温度140℃与反应时间3 h下,以Ca(5%)-γ-Al_(2)O_(3)为催化剂,葡萄糖转化率为100%,5-HMF收率最高为58.6%。此外,Ca-γ-Al_(2)O_(3)循环操作(未煅烧)5次后,5-HMF收率略有降低至55%左右,同时杂化负载方式使得CaO在酸性溶液中的泄露较低,表明Ca-γ-Al_(2)O_(3)具有良好的操作稳定性。催化剂机理分析表明,Ca-γ-Al_(2)O_(3)具有良好的葡萄糖异构化能力,CaO的杂化可提高催化剂与葡萄糖的相互作用,果糖脱水过程主要依赖于酸溶液的催化。

The method ofγ-Al_(2)O_(3)spherical beads doped CaO(Ca-γ-Al_(2)O_(3),beads size 1.8±0.1 mm)coupling with an acid solution was developed for preparing 5-hydroxymethylfurfural(5-HMF)from glucose.The Ca-γ-Al_(2)O_(3)spherical beads were characterized by XRD and BET.Also,the effects of the doping amount of CaO,the concentration of solvent acid,the ratio of dimethyl sulfoxide(DMSO)to water in the solvent,the amount of catalyst,the reaction temperature and time on the catalytic performance were analyzed.Besides,the operational stability of Ca-γ-Al_(2)O_(3)and the catalytic mechanism were evaluated and discussed respectively.The experimental results show that the doping amount of CaO(doping amount≤10%)has little effect on the pore structure of the particles.Furthermore,100%glucose conversion and the highest yield of 5-HMF with 58.6%is obtained under the following conditions:0.05 mol·L^(-1)acid concentration,V(DMSO)∶V(H_(2)O)=3∶1,the ratio of glucose to catalyst=2∶1(125 mg∶63 mg),the reaction temperature of 140℃and the reaction time of 3 h.Moreover,after 5 cycles of Ca-γ-Al_(2)O_(3)operation(not calcined),the 5-HMF yield reduces slightly to about 55%,and the leakage of CaO in acidic solution is lower due to the doping approach,which indicate that Ca-γ-Al_(2)O_(3)had good operational stability.Hence,the catalysis mechanism shows that Ca-γ-Al_(2)O_(3)has excellent glucose isomerization ability.The doping of CaO can improve the interaction between the catalyst and glucose and the dehydration process of fructose mainly depends on the catalysis of acid solution.