Knowledge Management System Of Institute of process engineering,CAS
费托合成油品以长直链烷烃为主，且具有无硫、无氮、低芳烃等优点，可作为高档柴油和润滑油基础油的原料。然而，长链烷烃凝点较高、低温流动性较差，需经异构降凝改善其油品性质。基于此，本课题以工业开发为导向，结合费托合成油品无硫的清洁优势，通过筛选工业生产的分子筛酸性材料，及与金属组分的匹配性，开发一种对长链正构烷烃异构化活性高、选择性好、适于费托重柴油异构降凝的非硫化态催化剂；并且进一步阐释催化剂各性质对长链烷烃异构反应性能的影响及作用机理。本课题首先以金属Pt和Ni为加氢组分，通过考察工业常用的酸性分子筛（如ZSM-5、SAPO-11、Beta和ZSM-22分子筛等）的加氢异构性能，筛选出具有适宜酸性、孔道结构的分子筛用于异构降凝催化剂的开发。研究结果表明，与其它分子筛载体相比，以贵金属Pt为活性组分时，硅铝比为300的ZSM-22分子筛因其合适的酸量和酸强度，以及适宜的一维十元环孔道结构，从而表现出最高的加氢异构性能，柴油收率最高，降凝效果最好。进一步基于ZSM-22分子筛为载体考察了金属位对双功能催化剂异构性能的影响。当以金属Ni为活性组分时，因金属Ni的加氢脱氢性能弱于Pt，导致异构中间体无法及时加氢，使异构选择性降低、裂解反应增加。为降低催化剂成本，以Ni金属为金属位，详细考察硅铝比对ZSM-22分子筛晶粒形貌、晶粒大小、酸强度和酸量的影响，并通过费托合成重柴油为原料考察了不同催化剂的异构反应性能。研究结果表明硅铝比对分子筛晶体形貌和酸性有显著影响。其中小晶粒、低硅铝比的ZSM-22-70分子筛更适合用于费托重柴油的异构降凝反应，以其为酸性组分开发的Ni基催化剂HI-1表现出较好的异构化性能，产物柴油收率为80%时，其冷滤点为-8 ?C。随后通过对催化剂活性金属负载方式的考察发现，与浸渍法相比，采用共沉淀法或均匀沉淀法制备催化剂时，可以显著提高活性金属分散度，缩短金属活性位与酸性位的间距，从而提高催化剂上活性金属加氢-脱氢功能与酸功能的匹配性，异构化性能显著增加。同时，均匀沉淀法制备催化剂的异构化性能略高于共沉淀法制备催化剂，其柴油收率为90%时冷凝点为-8 oC。在以上工作的基础上，通过离子交换的方式对ZSM-22-70分子筛进行金属Zn改性并进行表征，并考察了Zn负载量对催化剂异构性能的影响。研究结果表明，Zn改性后分子筛的比表面积、孔容和孔径略有减小，但总酸量明显降低；并且随Zn负载量的增加而呈现先降低后略有增加的趋势，催化剂活性金属加氢功能与酸功能的匹配性显著增加，异构化选择性增加，在保持高的柴油收率时，可以有效提高柴油馏分的低温流动性能。;Fischer-Tropsch synthetic oils are mainly long-chain paraffins and have the advantages of no sulfur, no nitrogen and low aromatics. They can be used as raw materials for high-grade diesel and lubricating base oils. However, long-chain alkanes have higher freezing points and poor low-temperature fluidity, which requires heterogeneous pour point depressing to improve their oil properties. Based on this, this project is oriented towards industrial development, combined with the sulfur-free cleaning advantages of Fischer-Tropsch synthetic oils. By screening industrially produced zeolites acid materials and matching with metal components, a long-chain normal paraffin is developed. It has high isomerization activity and good selectivity, and is suitable for the non-sulfurized catalyst of Fischer-Tropsch heavy oil isothermal pour point depressing; and further explains the influence of various properties of the catalyst on the isomerization reaction performance of long-chain alkanes and its mechanism.This project firstly uses metal Pt and Ni as hydrogenation components, and investigates the hydrogenation isomerization properties of acid zeolites (such as ZSM-5, SAPO-11, Beta and ZSM-22 zeolites) commonly used in industry. Molecular sieves of acidity and pore structure are used for the development of heterogeneous pour point depressing catalysts. The results show that compared with other zeolite carriers, the ZSM-22 molecular sieve with a silicon-aluminum ratio of 300 is suitable for one-dimensional ten-membered ring channel structure when the precious metal Pt is used as the active component. Thus, it exhibits the highest hydroisomerization performance, the highest diesel yield and the best pour point depressing effect. Effect of metal sites on the heterogeneous properties of the bifunctional catalyst was investigated based on ZSM-22 zeolites. When metal Ni is used as the active component, the hydroisomerization performance of the metal Ni is weaker than Pt, which results in the inability of the iso-intermediate to be hydrogenated in time, which reduces the isomer selectivity and increases the cracking reaction.In order to reduce the cost of the catalyst, the influence of the ratio of silicon to aluminum on the grain morphology, size, acid strength and content of ZSM-22 zeolite was investigated in detail. The F-T heavy diesel oil was used as raw material. The heterogeneous reaction performance of different catalysts. The results show that the silica-alumina ratio has a significant effect on the morphology and acidity of the zeolite crystal. Among them, ZSM-22-70 zeolite with small crystal sizes and low silicon to aluminum ratio is more suitable for the heterogeneous pour point depressing reaction of F-T heavy diesel oil. The Ni-based catalyst (HI-1) developed for its acidic component shows better performance. When the diesel yield of the product is 80%, the cold filter point is -8 oC. Subsequently, by investigating the active metal loading mode of the catalyst, it was found that when the catalyst was prepared by coprecipitation or homogeneous precipitation compared with the impregnation method, the dispersion of the active metal was significantly increased, and the distance between the active site and the acid site of the metal was shortened. In order to improve the compatibility of the hydrogenation-dehydrogenation function of the active metal on the catalyst with the acid function, the isomerization performance of the catalyst is significantly increased. At the same time, the isomerization performance of the catalyst prepared by the homogeneous precipitation method is slightly higher than that of the coprecipitation method, and the condensation point is -8 oC when the diesel yield is 90%.On the basis of the above work, ZSM-22-70 molecular sieve was modified and characterized by ion exchange. Effect of Zn contents on the heterogeneity of the catalyst was investigated. The results show that the specific surface area, pore volume and pore size of the molecular sieve after Zn modification are slightly reduced, but the total acid amount is obviously reduced; and with the increase of ZnO contents, it tends to decrease slightly and then the catalyst active metal The matching of hydrogenation function and acid function is significantly increased, the selectivity of isomerization is increased, and the low temperature flow performance of the diesel fraction can be effectively improved while maintaining high diesel yield.
|白宜灵. Ni/ZSM-22分子筛在费托油品加氢异构化反应中的研究[D]. 中国科学院大学,2019.|
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