孔结构与酸性质对多孔硅铝材料催化性能的影响
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摘要
采用成胶、陈化、后处理等过程制备出具有不同孔道结构和不同酸性质的多孔硅铝材料,用XRD,BET,FT-IR,NH_3-TPD等方法对这些多孔材料进行结构和性能表征,并采用重油微反评价装置对这些材料制成的催化剂进行裂化性能考察。结果表明,通过合成条件的微调可以获得平均孔径为7～14nm、总酸量为0.617～1.046mmol/g、同时含有B酸中心和L酸中心的多孔硅铝材料。孔径大小、酸性质及水热稳定性直接影响材料的转化能力及产品分布,其中孔径大小和酸性质的影响不尽相同,当平均孔径(水热老化后)为11～14nm时,二者的作用是相辅相成的,共同促进裂化活性的提升;当平均孔径进一步增大时,孔径大小对裂化性能的影响程度超过酸性质的影响;在酸性质中,总酸量主要影响材料的裂化活性,而酸中心分布则更多地影响产物分布。
A series of porous silica-alumina materials with different pore structures and acidities was prepared through co-gel,aging and post-treatment process,the structural properties was characterized by XRD,BET,FT-IR,NH_3-TPD,and the cracking activites of the catalysts preparated by these materials were evaluated with the heavy oil micro-reactor.The results revealed that the materials with pore diameters of 7—14 nm,total acid contents of 0.617—1.046 mmol/g,and with both Brnsted acid and Lewis acid are obtained by the adjustment of preparation conditions.Pore structure and acidic property as well as hydrothermal stability play important roles on cracking activity and product distribution,but pore size and acidity have different effects.When the pore size is between 11—14 nm after hydrothermal ageing treatment,the functions of pore structure and acidic property are complementary and promote the activity of cracking.As the pore sizes become larger,the effect of pore structure on cracking is much stronger than that of acidity.For acidity,the cracking activity is affected dramatically by the total acid content,but the product distribution mainly depends on the distribution of acid centers.
A series of porous silica-alumina materials with different pore structures and acidities was prepared through co-gel,aging and post-treatment process,the structural properties was characterized by XRD,BET,FT-IR,NH_3-TPD,and the cracking activites of the catalysts preparated by these materials were evaluated with the heavy oil micro-reactor.The results revealed that the materials with pore diameters of 7—14 nm,total acid contents of 0.617—1.046 mmol/g,and with both Brnsted acid and Lewis acid are obtained by the adjustment of preparation conditions.Pore structure and acidic property as well as hydrothermal stability play important roles on cracking activity and product distribution,but pore size and acidity have different effects.When the pore size is between 11—14 nm after hydrothermal ageing treatment,the functions of pore structure and acidic property are complementary and promote the activity of cracking.As the pore sizes become larger,the effect of pore structure on cracking is much stronger than that of acidity.For acidity,the cracking activity is affected dramatically by the total acid content,but the product distribution mainly depends on the distribution of acid centers.
引文
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[2]O’connor P,Gevers W,Hunphries A,et al.Fluid catalytic cracking II:Concepts in catalyst design[M].Washington DC:American Chemical Society,1991:318-342
[3]Abramova A V,Slivinskii E V,Goldfarb Y Y,et al.Development of efficient zeolite-containing catalysts for petroleum refining and petrochemistry[J].Kinetics and Catalysis,2005,46(5):758-769
[4]O’connor P,Humphries A P.Accessibility of functional sites in FCC[J].Am Chem Soc Div Petro Chem Preprints,1993,38(3):598
[5]Kresge C T,Leonowicz M E,Roth W J,et al.Ordered mesoporous molecular sieves synthesis by a liquid crystal template mechanism.Nature,1992,359:710-712
[6]朱华元,何鸣元,宋家庆.催化剂的大分子裂化能力与渣油裂化[J].炼油设计,2000,30(8):47-51
[7]郑金玉,欧阳颖,罗一斌,等.无序介孔硅铝材料的合成表征及性能研究[J].石油炼制与化工,2015,46(9):47-51
[8]郑金玉,罗一斌,喻辉,等.含介孔硅铝材料催化裂化催化剂(CRM-200)的工业应用[J].石油炼制与化工,2015,46(10):40-44
[9]郑金玉,罗一斌,喻辉,等.金属修饰对活性中孔材料(AMC)裂化性能的影响[J].石油学报(石油加工),2018,34(3):455-464
[10]郑金玉,罗一斌,舒兴田.孔结构与酸性质对多孔氧化铝材料催化性能的影响研究[J].石油炼制与化工,2018,49(12):27-33