Study On The Micromorphological Structure And Gasoline Desulfurizarion Performance Of Membranes Based On Cellulose

The modifying of membrane material based on cellulose for gasoline desulfurization was rely on copolymerization blending and hybrid blending methods in this paper. The changed behaviors of microstructure and the mass transfer mechanism of gasoline components in the modified membranes with different treatment conditions based on cellulose were studied. The correlations between microstructure and desulfurization performance of pervaporation membranes based on cellulose were also investigated, which provides a set of methods to design the microstructure of desulfurization membranes based on cellulose with high separation performance.The novel copolymerization blending membrane was prepared from poly(acrylonitrile-co-glycidyl methacrylate)(PANGMA) and ethyl cellulose (EC) for sulfur removing from model gasoline by pervaporation. When the temperature of preparing membrane increased, permeation flux increased and sulfur enrichment factor remained almost invariable due to the evident decrease of the EC island clusters size. The result of the pervaporation performance using the PANGMA-EC membranes with different temperatures of preparing membrane showed that the increasing collision frequency among EC island clusters was effective to increase permeation flux with little change of sulfur enrichment factor. By comparing the micro-phase structure of PANGMA-EC membranes with17%,16%and15%solid contents, the distribution density of the EC clusters decreased in the15%solid content membrane, leading to the comparatively larger size of EC stripy clusters in the micro-phase structure of PANGMA-EC membrane. Large size of the EC stripy clusters in the PANGMA-EC membrane could facilitate the formation of increasing diffusion pathways of gasoline components, resulting in the increase of total flux. The grafting copolymerization between PANGMA and EC was also a crosslinking reaction. With the increase of the catalyst amount, the EC island clusters size increased and stripy clusters size decreased, which led to the decline in permeate flux and the increase in sulfur enrichment factor. So the better desulfurization performance of PANGMA-EC membranes were obtained by regulating the above influence factors of micro-phase separation structure.EC/C60hybrid blending membranes were prepared for sulfur removal from gasoline by pervaporation. The charge-transfer complex interaction between different gasoline components and fullerene C6o was studied, and the change regularity of permeation flux and sulfur enrichment factor corresponded to the desulfurization mechanism that concluded on dynamic sorption curves. These were verified by pervaporation experimental results of EC and EC/C60membranes, which further proved that the addition of C6o could be helpful for the removal of sulfur from gasoline effectively. The different heat treatments and solvents annealing treatments for EC/C60hybrid blending membranes were made to increase the desulfurization performance of membranes. It was found that the EC/C60membrane microstructure with the steady-state C60clusters evenly distributing in EC main phase could result in the better solution selectivity of membranes for thiophene, according to the microstructure study of EC/C60hybrid blending membranes with different heat treatments (40℃,60℃, and80℃). The change regularity of the microstructure of EC/C60hybrid blending membranes with different solvents annealing treatments was as follows, the morphological development of C60clusters was from irregular shape, ball shape, flower shape to square shape with solvents annealing treatments from n-heptane to thiophene for membranes, the C60clusters size changed from several namometer to hundreds of namometer at the meantime. The electron affinity of C60clusters increased with the increase of clusters size, so sorption and diffusion coefficients for model gasoline components in the EC/C60hybrid blending membrane with cyclohexene annealing treatment were higher than those of membranes with n-heptane and cyclohexane annealing treatments. When the C60clusters size was higher than100nm, the electron affinity of C60clusters in EC/C60hybrid blending membranes was unchanged, so sorption and diffusion coefficients for model gasoline components in EC/C60hybrid blending membranes with toluene and thiophene annealing treatments were lower than that of the membrane with cyclohexene annealing treatment. In the condition of75℃(operating temperature), for the EC/C60hybrid blending membrane with cyclohexene annealing treatment, less decreasing of sulfur enrichment factor (4.55) and increased permeation flux (5.93kg·m-2·h-1) were obtained compared to the EC/C60hybrid blending membrane without any treatment (4.72,2.32kg·m-2·h-1).Acid treatment on multi-walled carbon nano-tubes (MWCNTs) and preparation of EC/MWCNTs hybrid blending membranes were performed via in hybrid blending. X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetic analysis were utilized to evaluate the effects of acid-treated MWCNTs on the desulfurization performance of the EC/MWCNTs membranes. Results indicated that carboxyl and hydroxyl groups could be successfully introduced onto the surface of MWCNTs by acid treatment. The electron affinity improvement of MWCNTs by acid treatment performed better compared with raw MWCNTs, so sorption and diffusion coefficients for unsaturated gasoline components in EC/MWCNTs(sample2) membranes composed of mixed-acid-treated MWCNTs were higher than those of EC/MWCNTs(sample1) membranes. The correlations between microstructure and pervaporation performance of EC/MWCNTs hybrid blending membranes were studied. Carboxyl and hydroxyl groups on MWCNTs by acid treatment improved the dispersity of MWCNTs in the EC/MWCNTs hybrid blending membrane greatly, and carboxyl and hydroxyl groups on MWCNTs were electrophilic groups, so the desulfurization performance of EC/MWCNTs hybrid blending membranes increased due to the existence of acid-treated MWCNTs. The desulfurization performance improvement of EC/MWCNTs membranes by acid-treated MWCNTs(sample2) performed better compared with acid-treated MWCNTs(sample1). The obtained permeation flux and sulfur enrichment factor (7.14kg·m-2·h-1,4.80) of the EC/MWCNTs hybrid blending membrane by acid-treated MWCNTs(sample2) were larger than those of the EC/C60hybrid blending membrane with cyclohexene annealing treatment (5.93kg·m-2·h-1,4.55).