Preparation Of SbSn Intermetallic Compound And Its Desulfurization Application

The quality of crude oil becomes poor with each passing day, the content of sulfur and heavy metal being increased. Meanwhile, aggravation of the environmental pollution impels all the countries in the world to put forward stricter and stricter criterion of sulfur content for all oil products. The conflicts of the two aspects promote the development of environmentally friendly technology. In recent years, it was reported that SbSn intermetallic compound could remove sulfur and heavy metal from oil and regulate the group composition of the petroleum to a certain extent under room temperature and ambient pressure because of its special surface micro-structure and function. The desulfurization and demetalization performance of the SbSn indicates a new research field.This study focused on the preparation and modification of SbSn intermetallic compound. The analysis and characterization of SbSn were carried out with the aid of modern analytical techniques, including XRD, SEM, TEM, DSC and AES etc. The desulfurization performance of the functional material was researched in detail by using thiophene—one of the most difficult removal sulfur compound in petroleum cut fractoion as model compound in this dissertation. The following results have been obtained.Primarily, the SbSn was prepared by smelting with Sb, Sn as raw materials. The effects of mass ratio and preparation conditions on the desulfurization performance of SbSn were investigated. The results of XRD showed that the SbSn could be prepared by smelting at high temperature for a period of time with raw material mass ratio of 49:51 (Sb:Sn). As indicated by XRD and TEM analysis, the average grain size of SbSn decreased with the temperature increased; the defects of SbSn intermetallic compound prepared by fast cooling were much more than that prepared by cooling slowly and the active spot on the surface of SbSn increased accordingly. Under cooling slowly condition, the crystallinity and density of SbSn would be improved with the increase of the reaction temperature; the longer the reaction time was, the better the crystallinity and density was, but the influence of reaction time was less than that of reaction temperature. The surface of SbSn intermetallic compound consisted of element Sb mainly by AES. Orthogonal experiments and mono-factorial analysis were used to find out the optimal preparationconditions of SbSn prepared by smelting. The influence of mass ratio, reaction temperature, reaction time, the particle size of Sb and cooling method on the desulfurization performance of SbSn were studied. The desulfurization experimental results showed that the preferable material preparation conditions were: m(Sb):m(Sn)=49:51, the reaction temperature 950 ℃, the reaction time 60min, the particle size of Sb less than 200 meshes and fast cooling. The optimum conditions for desulfurization were: the ratio of SbSn and oil was 0.6, desulfurization time was 30h and the w/o emulsion was used. Under single pass, the sulfur removal ratio for simulated oil was 15.0% and for gasoline was 11.8%. Adding a third metal element, especially, by an amount of Zn could enhance the desulfurization performance of SbSn obviously. The sulfur removal ratio for simulated oil was increased to 18.6% from 15% by mixing 2wt% of Zn in SbSn.Secondly, the possibility of preparation of SbSn intermetallic compound by mechanical alloying (MA) was investigated. The influence of the ball milling technology and the proportion of raw materials (Sb and Sn) on the MA was studied. The MA mechanism was discussed too. The results showed that, in a certain range of the raw material mass ratio (Sb:Sn), the SbSn intermetallic compound could be prepared by mechanical alloying. It does not accord with the phase diagram. The composition of the SbSn intermetallic prepared by MA could be far apart from its equilibrium value implied that the solid solubility could be greatly enhanced by the mechanical alloying. The results of characterization showed that both the grain size and the particle size of SbSn decreased with the milling time, the large lattice distortion occurred inside the grains and the fast diffusion increased due to the high density of lattice defects. The desulfurization experimental results showed that the optimum preparation conditions of mechanical alloying were: m(Sb):m(Sn)=49:51, bprs10:1 and rotation speed 270r/min.Thirdly, the annealing experiments of SbSn were carried out. The results of desulfurization experiments indicated that the desulfurization performance of SbSn treated by annealing at temperature from 60 ℃ to 120℃ decreased notably. The results of XRD showed that the average grain size of the SbSn increased with the annealing temperature. While the SbSn annealed at low temperature, the desulfurization performance of the SbSn decreased remarkably showed that the vacancy defect and"defect density" decreased.Finally, it is necessary to carry out regeneration for SbSn because it lost activity after single pass for desulfurization. Several cleaning methods for restoring its desulfurization activity were investigated. It was found that regeneration by methylbenzene washing was an appropriate method. The activity of the SbSn would be renewed to a certain extent by methylbenzene immerging. The circulation tests for desulfurization were also done. A total sulfur removal ratio of 32% for simulated oil was obtained after continuous treatments of the simulated oil three times with the fresh smelting SbSn (first treatment) and the used smelting SbSn immerged by methylbenzene (second and third treatment). Similarly, a total sulfur removal ratio of 23% was obtained by using the MA SbSn.