| The development of PAO producing process using coal-based F-T synthetic oil is of great significance on improving the current domestic production capacity which is unable to meet the market demand for a long time and enhancing the added value of coal-based oil products and the economic benefits of coal-based oil production plants.In order to eliminate the influence of oxygenates in raw materials on the activity of polymerization catalyst in the process of producing high value-added product PAO from F-T synthetic oil,this paper investigates the influence of oxygenates in F-T synthetic oil on α-olefin polymerization and their adsorption and removal.In this paper,1-heptanol and 1-octanal,which are typical oxygenates in light components of F-T synthetic oil,were used as model oxygenates to systematically investigate the effects of 1-heptanol and 1-octanal on the performance of supported catalysts and PAO products.The results show that the surface acid strength,Al/Ti molar ratio and the binding strength of the active component to the support decrease,and the micro morphology of the catalyst surface is destroyed.The valence of Al/Ti species are not changed,but the increase of the binding energy shows that the binding mode has changed for the active components Al/Ti are combined with more oxygen-containing groups after the treatment of oxygenates.1-octanal and 1-heptanol have significant effects on the structure and activity of the supported catalyst and the polymerization effect of 1-decene.When the content is the same,the effect of 1-heptanol is greater than that of 1-octanal.The results of batch polymerization show that when the concentration of 1-heptanol and 1-octanal rises to 500 mg/L,the polymerization yield decreases by 36.3%and 31.3%,respectively.At the same time,the 40℃ and 100℃ viscosity,viscosity index and pour point of the product also decrease.On this basis,the process of high-efficiency adsorption and removal of oxygenates is further investigated.By means of particle size,pore structure and IR analysis,combined with dynamic adsorption experiment,suitable adsorbents were selected.The results show that TypeC silica gel has better particle size distribution,larger pore volume,more surface active adsorption groups and better dynamic adsorption performance.Under the optimized adsorption conditions of 150℃ and 9h,when the adsorption temperature is 20℃,the loading height of the adsorbent is 50 mm and the volume space velocity is 0.3-0.9 h-1,the adsorption rate constant kTH is kept at 2.66～4.22×10-6 L/(min-mg),the dynamic saturated adsorption capacity Q0 is changed in the range of 66.85～69.71 mg/g,and the removal efficiency of Type-C silica gel for oxygenates reaches 100%.Compared with the fresh adsorbent,the dynamic adsorption rate constant of the regenerated catalyst is reduced by 17.1%,and the dynamic adsorption capacity is reduced by 8.27%.The regenerated adsorbent still has a high adsorption capacity of oxygenates.In the end,the performance of PAO product from F-T synthetic oil after removal of oxygenates was investigated by batch reactor.The results show that the yield of PAO is increased by 25.7 percentage points,the viscosity at 100℃ is increased from 6.82 mm2/s to 10.11 mm2/s,and the viscosity,pour point,viscosity index and density are all increased.Taking the F-T synthetic oil after the removal of oxygenates as the raw material,the main performance of PAO can reach the market PAO-10 index,and it can be further treated by hydrogenation as a high-quality base oil product.The research in this paper lays a foundation for the development of PAO synthesis process based on F-T synthetic oil. |
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