Preparation Of Cross-linked Polymer Adsorbents And Their Application In Desulfurization Of Fuel Oil

In view of the disadvantages of traditional hydrodesulfurization,the key to the deep desulfurization of fuel oils is how to efficiently remove the dibenzothiophene series sulfide.Adsorption desulfurization technology has become one of the most popular researches in desulfurization technology due to its advantages of simple operation,renewal of adsorbent,and so on.The development of novel sorbents with high selectivity,good adsorption capacity and regeneration performance is the core of adsorption desulfurization technology.For this,we prepared two types of cross-linked polymer adsorbents through novel synthesis methods and studied their desulfurization performance for thiophene sulfides(4,6-DBT,DBT and BT)in model oils.First,by using copper nitrate and 1,3,5-benzenetricarboxylic acid(BTC)as raw materials and polyacrylic acid(PAA)as a cross-linker,five types of MOFs(Cu-BTC and PMOFs-1?PMOFs-4)with different amounts of PAA were synthesized via solvent evaporation method.XRD,BET,SEM,TEM,and TG analysis were used to characterize their microstructure,morphology,and thermal stability,and their desulfurization performance were studied.The results show that Cu-BTC and PMOFs are all micro-mesoporous materials with irregular crystal shapes and good thermal stability,their specific surface area is above 1000 m2/g,and the thermal decomposition temperature is above 300 ?.Among them,PMOFs-1 has high specific surface area of 2224.79 m2/g,pore volume of 0.96 cm3/g,and average pore size of 3.67 nm.The adsorption ability of Cu-BTC and PMOFs follows the order of PMOFs-1>PMOFs-2>PMOFs-3>Cu-BTC>PMOFs-4.Under the conditions of mass ratio of sorbent/oil of 1:100,30 ? and 1000 ppmS model oil,the adsorbance of PMOFs-1 for 4,6-DMDBT,DBT and BT can reach 40.8 mgS· g-1,46.4 mgS · g-1 and 22.0 mgS·g-1 respectively,showing excellent adsorptive ability and good regeneration performance.The adsorption isotherms can be well fitted with the Freundlich equation.This indicates that doping of appropriate amount of PAA is beneficial to increase the specific surface area,the particle size,the porosity and the cross-linking degree of the material,and accordingly to improve their desulfurization ability.Second,by using benzoic acid as a template molecule,1-vinylimidazole(VIM)and divinylbenzene(DVB)as raw monomers,some cross-linked copolymers(P(VIM-DVB)and MIPs)were prepared via molecular imprinting.IR,FTIR,SEM,BET,and TG analysis were used to characterize their composition,morphology,microstructure and thermal stability,and their desulfurization performance were studied.The results show that P(VIM-DVB)and MIPs are all mesoporous materials with good thermal stability with their decomposition temperatures all above 300 ?.Among them,MIPs-3 has the largest specific surface area of 68.86 m2/g,pore volume of 0.25 cm3/g,and an average pore diameter of 14.85 nm.The adsorption capacity of MIPs-3 for 4,6-DMDBT,DBT and BT in the 1000 ppmS model oil is 5.0 mgS·g-1,6.3 mgS·g-1 and 2.6 mgS·g-1 at the adsorbent/oil mass ratio of 1:50 and 30 ?.Its adsorption isotherms can be well fitted with the Freundlich equation.The desulfurization ability of the three MIPs is better than that of P(VIM-DVB),indicating that the molecular imprinting method can effectively improve the desulfurization performance of sorbents.The adsorption performance of the MIPs for the thiophene sulfurs follows the order of DBT>4,6-DMDBT>BT.The highest selectivity for DBT indicated that the molecular imprinting of benzoic acid played a role on the selective adsorption of DBT.In addition,several imidazole-based cross-linked polymers have been synthesized,including VIM-DVB crosslinked copolymer MPs by the hard template method,1-vinyl-3-butylimidazolium chloride([VBIM]Cl)-DVB crosslinked copolymer PILs and cross-linked PILCs,being complexs of polymerized[VBIM]C1 and polyacids.Their desulfurization ability was tested.It was found that the adsorption desulfurization performance of these materials did not increase substantially compared with their precursers.This shows that further study is still needed on how to adjust the microstructure of the sorbent to make it has better desulfurization performance.