Study On Anti-iron Contamination Catalytic Cracking Catalyst

As the world's crude oil becomes increasingly heavy and inferior,the problem of heavy metal pollution in crude oil is becoming more and more serious,which places higher requirements on the anti-heavy metal pollution performance of FCC catalysts.In recent years,iron poisoning has occurred in some refineries,which seriously affects the stable operation of the catalytic cracking unit and the economic benefits of the refinery.Therefore,it is urgent to develop FCC anti-iron pollution catalysts.According to the mechanism of catalytic cracking iron pollution,we consider to improve the anti-iron pollution performance of FCC catalysts from three aspects:?1?Increasing the specific surface and pore volume of present FCC catalysts;?2?Increasing the content of aluminum oxide in present FCC catalysts,especially in matrix components;?3?Directly adding an element to improve the anti-iron pollution performance of the catalyst.Based on the above analysis and discussion,we conducted the following three researches in the thesis.Chapter 1:The mesoporous alumina was prepared by a sol-gel method using cheap and readily available cellulose as a template agent and pseudo-boehmite as an aluminum source.The effects of aging temperature,aging time,and calcination temperature on the pore structure and surface acidity of synthesized mesoporous alumina,were first screened and the optimal conditions were determined as aging at 80°C for 1.5 h,then calcinating at 550°C.The prepared alumina showed large specific surface area,large porous volume,rich mesoporous structure and high surface acid density.Anovel FCC catalyst was prepared by using the above-prepared alumina as a matrix component.The anti-iron pollution performance of the catalyst was investigated by ACE evaluation.The results show that compared with the respective freshener samples,the yields of oil slurry and coke by using iron-polluted conventional FCC catalyst increased by 1.77 and1.61 percentage points,respectively;the gasoline,total liquid yields and the conversion decreased by 2.60,3.53,and 1.89 percentage points,respectively;whereas the yields of the slurry and coke by using the new anti-iron pollution FCC catalyst increased by 1.06and 0.85 percentage points,respectively;the yield of gasoline and total liquid and the conversion decreased by 1.55,1.95,and 1.39 percentage points,respectively.Chapter 2:Pseudo-boehmite@Kaolinite composite material was prepared by using dual aluminum method with acid-extracted Kaolinite as the source of acidic aluminum and sodium metaaluminate as the source of alkaline aluminum to construct pseudo-boehmite structural unit.This composite was then used as a matrix material to prepare a new anti-iron pollution FCC catalyst.The structure,properties and reaction performance of quasi-boehmite@kaolin composite materials and FCC catalysts,was analyzed and characterized by XRD,NH₃-TPD,N₂ adsorption-desorption,FT-IR,MAT and ACE.The results show that,in comparison with conventional kaolinite,the prepared pseudo-boehmite@kaolinite had significantly higher specific surface?112m²/g?,pore volume?0.39 cm³/g?,surface acid density and the content of Al₂O₃?57.13w%?.Under the same iron pollution level,in comparison with the catalyst prepared from traditional kaolin clay,heavy oil yield in new FCC reactiondecreased by 1.22percentage points,and the conversion rate increased by 1.96 Percentage points,and gasoline yield and total liquid yield increased by 2.08 and 2.23 percentage points,respectively.It showed stronger conversion capacity of heavy oil with better cracked product distribution.Chapter 3:A zinc-modified FCC catalyst was prepared by using zinc sulfate as a zinc source.The mechanism and performance of zinc-modified FCC catalyst against iron pollution were analyzed by XRD,N₂ adsorption-desorption,SEM and ACE.The results show that a stable zinc-iron spinel species?ZnFe₂O₄?with high melting point was formed at high calcinating temperature.Before iron pollution,there was no significant differences in specific surface area,pore volume,and micro-reactivity between zinc-modified and conventional FCC catalysts.After iron pollution,the specific surface area,pore volume,and micro-reactivity of zinc-modified FCC catalysts were significantly improved in comparison with conventional FCC catalysts.ACE evaluation results show that,compared with conventional FCC catalysts,the yield of heavy oil by using zinc-modified FCC catalyst decreased by 0.89 percentage points;moreover the yields of gasoline and total liquids increased by 0.61 and 0.75 percentage points,respectively under the same iron pollution level.These manifest the new catalyst show good resistance to iron pollution.