磷钨钒杂多酸相转移催化剂的制备及其深度氧化脱硫性能

以钒原子取代的Keggin型磷钨杂多酸与不同的季铵类阳离子表面活性剂反应合成了一系列磷钨钒杂多酸相转移催化剂,采用红外和X射线衍射对催化剂进行了表征。以H_2O_2为氧化剂,对模型柴油的氧化脱硫反应进行了研究,考察了季胺类表面活性剂种类、不同季胺盐含量、催化剂用量、氧硫比、反应温度等参数对反应的影响。结果表明,所制备的杂多酸相转移催化剂保留有杂多酸阴离子和季铵盐阳离子的结构特征。(C_(16)H_(33)(CH_3)_3) N]_3HPW_(11)VO_(40)]催化剂具有最佳的氧化脱硫性能和重复使用性能,在n(催化剂)/n(模型柴油)=1∶80,n(H_2O_2)/n(模型柴油)=8∶1,反应温度50℃,反应时间3 h的反应条件下,二苯并噻吩的转化率可达到100%;催化剂重复使用五次后,转化率为99.7%。反应过程中,该催化剂与反应物形成微乳体系,如同一个均相混合物,而反应结束体系静置一段时间后,催化剂和产物又形成两相,通过离心法就可以快速分离和回收催化剂。

Synthesis and deep oxidative desulfurization of vanadium-substituted polyoxotungstate phase transfer catalyst

A series of phase transfer catalysts, composed of vanadium-substituted phosphotungstic acid(H₄PW₁₁VO₄₀]) and different quaternary cationics were synthesized through ion exchange method. The characterization of FT-IR spectroscopy and X-ray diffraction confirmed that the integrity of polyoxometalate anions and quaternary ammonium cations immobilized in the phase transfer catalyst. The as-prepared catalysts were applied to the catalytic oxidative desulfurization of model diesel oil using H₂O₂ as oxidant. The influencing factors such as quaternary cationics species, catalyst composition,catalyst amount, oxygen-sulfur ratio and reaction temperature were investigated.(C₁₆H₃₃(CH₃)₃)N]₃HPW₁₁VO₄₀] is found to be efficient and reusable catalyst for oxidative desulfurization reaction. Under the optimized reaction conditions of n(catalyst)/n(model diesel)=1:80, n(H₂O₂)/n(model diesel)=8:1, 50℃, 3 h, the catalyst exhibits the dibenzothiophene conversion of 100% and excellent reusability with 99.7% conversion after five times reaction. The catalyst and reactants form a microemulsion system and behave like homogeneous mixture during reaction, but precipitates with biphase separation when the reaction ends. The catalyst could be quickly separated and recycled by centrifugation.