银离子修饰的介孔磷钨酸/二氧化硅催化剂氧化脱硫性能研究(英文)

Oxidative desulfurization of diesel oil over Ag-modified mesoporous HPW/SiO_2 catalyst

采用银修饰介孔磷钨酸/二氧化硅(mesoporous HPW/SiO2)催化剂,并研究了其在模拟柴油和真实柴油氧化脱硫反应中的催化性能。通过银修饰介孔HPW/SiO2,结合银离子对有机硫化物的选择吸附性和HPW对有机硫化物的催化氧化活性,以达到选择氧化脱硫的目的。模拟柴油分别采用石油醚、苯、1 -辛烯和二苯并噻吩配制,当银离子与HPW的摩尔比为2时,催化剂具有最高的选择催化氧化活性。采用N2吸附-脱附、XRD、UV-vis和EDS表征了银修饰的介孔HPW/SiO2催化剂,结果表明,银物种分散均匀且以Ag+形式存在。真实柴油的脱硫研究表明,相比介孔HPW/SiO2催化剂,修饰的催化剂介孔Ag2-HPW/SiO2脱硫率提高了4.6%,初始硫含量为1 800×10-6的直馏柴油能被脱除至228×10-6,脱硫率为87.3%。介孔Ag2-HPW/SiO2催化剂具有良好的再生性能,经再生处理后,Ag的损失量极少,其三次脱硫率达到84.8%。

Mesoporous HPW/SiO2 modified with Ag species was used as the catalyst for the oxidative desulfurization of both model and real diesel oils. Three model diesel oils were prepared by using petroleum ether, benzene, and octene, respectively, as solvent and with dibenzothiophene （DBT） as the objective sulfur compound. The catalyst with a molar ratio of Ag to HPW being 2 （Ag2-HPW/ SiO2） exhibits the highest catalytic activity; however, the catalytic activity decreases with further increase in Ag content. The results of nitrogen adsorption-desorption, X-ray diffraction, UV-vis, and energy dispersive spectroscopy show that isolated Ag^＋ ion is located on the modified catalyst. The modification of HPW/SiO2 with Ag species may combine the selective absorption capacity of Ag^＋ for sulfur compounds with the catalytic activity of HPW, which is helpful to enhance the selective oxidative desulfurization. During the desulfurization process, the sulfur compounds were first selectively adsorbed on the catalyst surface by π eomplexation between Ag^＋ and sulfur compounds, which could increase the probability of collision between sulfur compounds and catalytic active sites and then accelerate the oxidation reaction. The sulfur content in the real diesel oil can be reduced to 228×10^-6 from the original 1800×10^-6 over Ag2-HPW/SiO2 ; the desulfurization amount is 4.6% higher than that over the unmodified HPW/SiO2. In addition, the Ag- modified catalyst shows excellent reusability; after three reaction cycles, the desulfurization ratio of Ag2-HPW/SiO2 is only slightly lower than that of the fresh catalyst.