高校化学工程学报

采用溶胶-凝胶法制得了非晶态Fe-Al-P-O催化剂,用IR、XRD、TEM、BET及微反等技术表征和评价了其化学组成、结构特性、化学吸附和催化反应性能。实验结果表明:Fe-Al-P-O催化剂是由粒径约14nm的FePO4和AlPO4均匀混合形成的非晶态混合物,比表面积为94m2g-1,Lewis酸位Fe3+和Lewis碱位P=O的O2-是固体表面的主要活性位,H2O可以在其上进行解离吸附形成Fe-O-和P-OH键,1,2-二氯丙烷(DCP)通过Cl-与P-OH键中的H+作用形成桥式吸附态, DCP和H2O在Fe-Al-P-O催化剂表面反应具有良好的反应性能,反应产物主要是环氧丙烷(PO)、丙烯和少量的聚合物。在常压、250℃、空速540h-1和nH2O/nDCP=1.5:1的条件下,DCP转化率达到81.9%,生成PO选择性达85.1%。

Fe-Al-P-O catalyst was prepared by sol-gel method to synthesize propylene oxide (PO) from 1,2-dichloropropane (DCP) and H2O, and was characterized by techeniques of IR, XRD, TEM, BET and the reaction in a microreactor. The results show that Fe-Al-P-O catalyst is a non-crystal mixture of FePO4 and AlPO4 with the particle size 14nm and specific surface area 94m2g-1. Lewis acid site Fe3+ and Lewis base site O2- in P=O bond are the main active centers on the surface of the catalyst, on which H2O can be chemisorbed dissociatively to form P-OH and Fe-O- species. DCP can be chemisorbed on POH to form HCl and intermediate product of propylene, then the propylene is adsorbed on O- of Fe-O- bond to produce PO. By-products of this process, obtained from the microreactor experiments, include propylene and a few polymers. The conversion of DCP increases and the selectivity to PO decrease when the reaction temperature is increased, and both of them will benefit from lower space velocity. The ratio of H2O to DCP is not important in this reaction within the experimental range. Under the proper reaction conditions of 1×105 Pa, 250℃, space velocity 540h-1 and nH2O/nDCP=1.5:1, the conversion of DCP is 81.9% with the selectivity to PO of 85.1%.