镍铬类水滑石的制备及其催化性能

PREPARATION AND CATALYTIC APPLICATION OF Ni-Cr HYDROTALCITE-LIKE COMPOUNDS

采用低过饱和共沉淀法,以Ni(NO_3)_2·6H_2O和Cr(NO_3)_3·9H_2O为原料,NaOH为沉淀剂制备了晶相单一、结晶度高的镍铬类水滑石化合物,并利用XRD,IR及TG-DTA对其结构进行了表征。测定了加入沉淀剂NaOH后,不同n(Ni):n(Cr)混合盐溶液中混合盐体系pH值的变化情况,探讨了不同因素对镍铬类水滑石制备的影响。将制备的催化剂应用于尿素与丙二醇反应生成碳酸丙烯酯反应中,在反应温度170℃,n (尿素):n(1,2-丙二醇)=1:1,反应时间180 min,催化剂用量0.2 g条件下,尿素转化率可达100%,碳酸丙烯酯产率达90%。

NiCr hydrotalcite-like compounds with different Ni/Cr molar ratios were synthesized by a co-precipitation method. The effects of pH, Ni/Cr molar ratio, temperature and time of hydrothermal treatment on the structffre of the samples were investigated. The synthesized compounds were characterized by XRD, FT-IR and TG-DTG and studied in the catalytic synthesis of propylene carbonate with 1,2-propanediol and urea. The optimal reaction conditions have been determined by using orthogonally arranged experiments, reaction temperature 170℃, 0.2 g, molar ratio of PG to urea 1 ： 1, reaction time 3 h. Under these conditions, urea conversion was nearly 100% and PC yield reached 90%.