稀土改性多金属氧酸盐的合成、表征及催化燃油深度脱硫研究

Synthesis and Characterization of Rare Earth Modified Polyoxometalates and Their Application in Deep Desulfurization of Fuel Oil

采用分步反应,分步酸化法制得硅钼钒前驱体,并通过调合原料配比制得不同钒含量的前驱体H4+xSiMo12-xVxO40·nH2O(x为1~4)。以6种稀土La、Ce、Pr、Nd、Sm、Gd对制备的前驱体进行改性,制得24种稀土改性多金属氧酸盐催化剂。通过FT-IR与ICP-OES等表征手段对所制备的多金属氧酸盐催化剂进行系统表征,并考察了24种催化剂的催化活性,确定最优催化剂为CeH3SiMo10V2O40。研究了以CeH3SiMo10V2O40为催化剂,H2O_(2)为氧化剂,乙腈为萃取剂的催化氧化超深度脱硫体系。考察了催化剂用量,氧硫物质的量比,催化剂与氧化剂预接触时间,反应温度及初始硫含量对氧化脱硫效率的影响。实验结果表明,在催化剂用量占模拟油品质量的0.25%、氧硫比为10、催化剂与H2O_(2)预接触时间为8min、反应温度60℃、初始硫含量500ppmw的条件下,当反应达到平衡时,模拟油品中的二苯并噻吩已完全脱除。此外,将催化剂用于稳定汽油及催化柴油的催化氧化脱硫也得到了较好的脱硫效果,且催化剂重复使用5次后,仍具有极佳的催化活性。

The precursor H4+xSiMo12-xVxO40·nH2O(x=1~4) with different vanadium contents is prepared by the stepwise reaction, stepwise acidiza-tion method and adjusting the ratio of raw materials. 24 kinds of rare earth modified polyoxometalate catalysts are prepared by modifying the precur-sors with 6 kinds of rare earth elements which are La, Ce, Pr, Nd, Sm and Gd. The polyoxometalate catalysts are characterized with FT-IR and ICPOES. The catalytic activities of 24 kinds of catalysts are investigated, and the optimal catalyst is CeH3SiMo10V2O40. The ultra-deep desulfurization system with CeH3SiMo10V2O40 as catalyst, H2O_(2) as oxidant and acetonitrile as extractant is studied. The effects of the amount of catalyst, the molar ratio of oxygen to sulfur, the pre-contact time between the catalyst and the oxidant, the reaction temperature and the initial sulfur content on the oxidative desulfurization efficiency are investigated. The experimental results show that the dibenzothiophene in the simulated oil has been completely removed when the amount of catalyst accounts for 0.25% of the mass of the simulated oil, the ratio of oxygen to sulfur is 10, the pre-contact time between the catalyst and H2O_(2) is 8 min, the reaction temperature is 60℃ and the initial sulfur content is 500 ppmw. In addition, the catalytic oxidation desulfuriza-tion of stable gasoline and catalytic diesel oil with the catalyst also obtains good desulfurization effect, and the catalyst still has excellent catalytic ac-tivity after repeated use for 5 times.