Synthesis Of ILs-PW Encapsulated By Metal Organic Framework Catalysts On Catalytic Oxidative Desulfurization

With the increasing attention of environmental protection in the world,more and more stringent requirements have been put forward for the sulfur content in fuel oil,and the production of ultra-low sulfur fuel has become an inevitable trend.Oxidative desulfurization is a promising new method for the deep desulfurization of fuel oil.The characteristics of mild reaction conditions,simple technological process and efficient desulfurization of polycyclic thiophene sulphides have attracted much attention.Phosphotungstic acid（HPW）catalyst possesses excellent catalytic activity on ODS performance.However,it has some important influences on its desulfurization and recovery,such low specific surface area,easily agglomerated and is in a semi-homogeneous state,which limited its application.Therefore,it is of great significance to put into the development of HPW with high catalytic activity and excellent reusability by encapsulating a solid material with a high specific surface area.In this work,HPW@MIL-101（Cr）and ILs-PW@MIL-101（Cr）catalysts with high specific surface area were systhesized,and the ODS performance of the catalysts were studied.The conclusions were described as follows.1.Optimization of synthesis conditions and the study on oxidative desulfurization performance of HPW@MIL-101（Cr）（1）The HPW@MIL-101（Cr）catalyst with a HPW loading of 3.5 g,synthesized at220^oC under neutral environment for 12 h,exhibits the highest activity in ODS.At 50^oC with a catalyst dosage of 0.24 g,an model oil of 20 mL,and an O/S molar ratio of 8,the desulfurization rates over the HPW@MIL-101（Cr）catalyst towards benzothiophene after reaction for 120 min reach 99%,which was 3.4 times than HPW catalyst.The results showed that encapsulating HPW into MIL-101（Cr）could significantly improve the catlytic activity of HPW catalyst.（2）HPW into MIL-101（Cr）catalyst had only 58%desulfurization rate for TP.However,100%and 99%desulfurization rate were achieved for DBT and 4,6-DMDBT,respectively,which possesses excellent catalytic activity.2.Effects of ionic liquid on ODS performance of ILs-PW@MIL-101（Cr）catalyst（1）The order of catalytic activity of various ionic liquid modified ILs-PW@MIL-101（Cr）catalysts was followed as BMImPW@MIL-101（Cr）>BPyPW@MIL-101（Cr）>BMPPW@MIL-101（Cr）.As the carbon chain length increased,the catalytic activity of ILs-PW@MIL-101（Cr）catalyst displayed a trend of first increasing and then decreasing.The catalytic activity can be optimized by adjusting the length of alkyl side chain of ionic liquid.（2）The catalyst showed the most excellent catalytic activity with the carbon chain length of 4 and imidazole as ionic liquid.3.characterization and study on ODS performance of BMImPW@MIL-101（Cr）catalyst（1）A total of 99.6%BT removal was achieved using 0.06 g of BMImPW@MIL-101（Cr）and O/S molar ratio of 8 at a reaction temperature of 50oC within 150 min.（2）After the seventh cycle,the BT removal of BMImPW@MIL-101（Cr）remained at 96.0%,corresponding to a 3.6%decrease.However,the BT removal of HPW@MIL-101（Cr）was only 48%after the seventh cycle,corresponding to a 51%decrease.This proved that the modification of ionic liquid is an efficient way to improve the stability of catalyst.（3）The increased catalyst stability by the modification of ionic liquid may be explained in following ways:The introduction of BMIm+ensured the firmly encapsulated active PW^3-inside the cavity of MIL-101（Cr）,and the solubility of PW^3-in the aqueous was lower than before.This prevented PW^3-leaching on ODS process,and the loss of active PW^3-during regeneration by washing with water decreased,which greatly improved the stability of the catalyst BMImPW@MIL-101（Cr）.