Fe取代的Pt/H-ZSM-12催化剂的合成及其正十二烷加氢异构化性能研究  

Synthesis of Fe-substituted Pt/H-ZSM-12 catalysts and their performances in n-dodecane hydroisomerization

作　　者：韩沅龙 侯瑞峰 范立闯 董思洋 卢银花 陶智超 相宏伟[1,3] 杨勇 HAN Yuanong;HOU Ruifeng;FAN Lichuang;DONG Siyang;LU Yinhua;TAO Zhichao;XIANG Hongwei;YANG Yong(State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences,Taiyuan 030001,Shanxi,China;University of Chinese Academy of Sciences,Beijing 100049,China;Synfuels China Co.,Ltd.,Beijing 101407,China)

机构地区：[1]中国科学院山西煤炭化学研究所煤转化国家重点实验室,山西太原030001 [2]中国科学院大学,北京100049 [3]中科合成油技术股份有限公司,北京101407

出　　处：《低碳化学与化工》2024年第3期42-52,共11页Low-Carbon Chemistry and Chemical Engineering

基　　金：国家杰出青年科学基金(20225804);内蒙古自治区准格尔旗工信和科技局科技项目(2023CG-01)。

摘　　要：在长链烷烃的加氢异构反应中,H-ZSM-12分子筛独特的孔道结构有利于多支链异构体的生成,但其较强的酸性加剧了裂解副反应的发生。以Fe同晶取代分子筛骨架中的Al,可以有效降低分子筛的酸强度。为了提高异构产物的选择性,采用水热法合成了Fe取代度(以n(Fe):n(Al+Fe)计)分别为0%、50%和100%的Z12-Al、Z12-Al-Fe和Z12-Fe分子筛。紫外可见吸收光谱(UV-Vis)表征结果表明,Z12-Al-Fe和Z12-Fe中引入的Fe绝大多数以[FeO_(4)]的结构存在于分子筛骨架中。红外吸收光谱(FT-IR)和X-射线光电子能谱(XPS)表征结果表明,H-Z12-Al-Fe和H-Z12-Fe骨架中的Fe与Si—OH结合形成了Si—OH—Fe键。氨气程序升温脱附(NH_(3)-TPD)和吡啶红外(Py-IR)表征结果表明,随着分子筛中Fe含量的增加,其强酸位的酸强度逐渐降低,总Bronsted酸的数量明显减少。在分子筛载体上负载足量的金属Pt后,以正十二烷(n-C_(12))为模型化合物评价了双功能催化剂的加氢异构性能(反应压力为2.0 MPa,n(H_(2)):n(n-C_(12))为6.0)。结果表明,Pt/H-Z12-Fe上Bronsted酸强度的降低和酸性位数量的减少使其催化活性低于Pt/H-Z12-Al,但弱Bronsted酸性对裂解反应的抑制使其在90%左右的n-C_(12)转化率下获得了最高的总异构选择性(85.7%)和多支链异构体选择性(53.8%),比Pt/H-Z12-Al分别高出18.6%和9.7%。此外,Pt/H-Z12-Fe在120 h的连续反应中表现出了优异的稳定性。The unique pore structure of H-ZSM-12 zeolite is conducive to the formation of multi-branched isomers in long chain alkane hydroisomerization,but its strong acidity exacerbates the occurrence of cracking reactions.Substitution of Fe for Al in the framework of zeolites could effectively reduce the acid strength.In order to improve the selectivity of i-alkanes,Z12-Al,Z12-Al-Fe and Z12-Fe zeolites with Fe-substitution degrees(calculated as n(Fe):n(Al+Fe))of 0%,50%and 100%,synthesized by hydrothermal method.The characterization results of ultraviolet-visible absorption spectroscopy(UV-Vis)indicate that the majority of Fe introduced in Z12-Al-Fe and Z12-Fe exist in the molecular sieve framework in the form of[FeO_(4)].The characterization results of infrared absorption spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS)indicate that Fe in the H-Z12-Al-Fe and H-Z12-Fe frameworks combines with Si—OH to form Si—OH—Fe bonds.The temperature programmed desorption of ammonia(NH_(3)-TPD)and pyridine infrared(Py-IR)characterization results indicate that with the increase of Fe content in the zeolite,the acid strength of its strong acid site gradually decreases,and the total amount of Brønsted acid significantly decreases.After loading sufficient metal Pt on the zeolite support,the hydroisomerization performance of the bifunctional catalyst was evaluated using n-dodecane(n-C_(12))as a model compound(reaction pressure is 2.0 MPa,n(H_(2)):n(n-C_(12))is 6.0).The reaction results show that the decrease in Brønsted acid strength and acid sites quantity of Pt/H-ZSM-12-Fe results in lower catalytic activity than Pt/H-ZSM-12-Al.However,the inhibition of weak Brønsted acids on cracking reaction results in the highest total isomers selectivity(85.7%)and multi-branched isomers selectivity(53.8%)at a n-C_(12) conversion rate of about 90%,which are 18.6%and 9.7%higher than Pt/H-Z12-Al,respectively.In addition,Pt/H-Z12-Fe exhibited excellent stability in a continuous reaction of 120 h.

关 键 词：ZSM-12分子筛 Bronsted酸调变 Fe同晶取代 正十二烷 加氢异构 

分 类 号：TQ517.4[化学工程] O622.1[理学—有机化学]