Pore-mouth catalysis boosting the formation of iso-paraffins from syngas over bifunctional catalysts  

孔口催化促进双功能催化剂上合成气制异构烷烃

作　　者：Mengheng Wang Yaoyao Han Suhan Liu Zhiming Liu Dongli An Zhiqiang Zhang Kang Cheng Qinghong Zhang Ye Wang 汪孟恒;韩瑶瑶;刘素含;刘志铭;安冬丽;张智强;成康;张庆红;王野(厦门大学化学化工学院,固体表面物理化学国家重点实验室,能源材料化学协同创新中心,醇醚酯化工清洁生产国家工程实验室,福建厦门361005)

机构地区：[1]State Key Laboratory of Physical Chemistry of Solid Surfaces,Collaborative Innovation Center of Chemistry for Energy Materials,National Engineering Laboratory for Green Chemical Productions of Alcohols,Ethers and Esters,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,Fujian,China

出　　处：《Chinese Journal of Catalysis》2021年第12期2197-2205,共9页催化学报（英文）

基　　金：科技部国家重点研究开发项目(2020YFB0606401,2019YFE0104400);国家自然科学基金(91945301,22072120,21972116,22008203).

摘　　要：Recent studies confirm that the emerging bifunctional catalysts consisting of metal oxide and zeolites can directly convert syngas into high-quality gasoline,however,the formation mechanism of iso-paraffins and the difference with the conventional FT/zeolite catalyst have not been investigated.Herein,three one-dimensional SAPO zeolites with diverse micropore sizes were synthesized and assembled with ZnAlO_(x)with spinel structure.It was found that ZnAlO_(x)/SAPO-41 and ZnAlO_(x)/SAPO-11 with medium micropore sizes favored the formation of C_(5)–C_(11)hydrocarbons with a high content of iso-paraffins.The characterizations pointed out that the formation of iso-paraffins over SAPO-11 followed a pore-mouth catalysis mechanism,which means the isomerization of linear hydrocarbons can only take place near the pore mouth region of zeolites.This mechanism only allows the formation of mono-branched iso-paraffins in the C_(5)–C_(11)range,which are less prone to be cracked than their di-branched isomers.A careful comparative analysis between ZnAlO_(x)/SAPO-11 and Co/H-meso-ZSM-5 was also made in terms of product distribution,activity,and stability.随着我国国民经济的快速发展,碳基能源需求量在不断上升,能源供需矛盾日益凸显.在可再生能源替代传统化石能源之前,着手开发合成气催化转化补充石油路线获得油料和大宗化学品成为形势所需,其中的关键点之一是高效催化剂的开发以实现对产物选择性的精准调控.近年来,利用氧化物/分子筛双功能催化剂将甲醇合成和C–C偶联有效集成的催化体系开辟了合成气转化乃至C1转化的新路径.随着合成气直接制低碳烯烃和芳烃等一系列研究取得重大进展,合成气定向转化为高品质汽油作为C1化学领域另一极具挑战性的研究课题也受到了科研工作者们的广泛关注.然而,目前对氧化物/分子筛双功能催化剂体系中异构烷烃的形成机理尚不明确,与传统的分子筛负载费托合成催化剂之间的性能差异还缺乏系统的研究.基于此,本文利用水热合成法制备了三种具有不同微孔尺寸的一维SAPO分子筛(SAPO-41、SAPO-11和SAPO-5),分别与尖晶石结构的ZnAlO_(x)氧化物耦合,并将其应用于合成气制汽油反应中.结果表明,以具有中等微孔尺寸的SAPO-41和SAPO-11分子筛作为C–C偶联功能组分时,合成气直接转化产物中C_(5)–C_(11)选择性分别高达71%和79%,且该馏分以异构烷烃产物为主.其中ZnAlO_(x)/SAPO-11催化剂上异构烷烃与正构烷烃的比例(C_(iso)^(0)/C_(n)^(0))达到13.相较于ZnAlO_(x)/SAPO-11,ZnAlO_(x)/SAPO-41催化剂在反应4 h后迅速失活,反应稳定性较差.在优化ZnAlO_(x)/SAPO-11催化剂性能后,分别从产物分布、活性和稳定性三方面入手,将其与经典的Co/H-meso-ZSM-5催化剂进行对比分析.结果表明,Co/H-meso-ZSM-5在低温下仍具有较强的CO活化能力,产物中C_(5)–C_(11)选择性可达70%,但C_(iso)^(0)/C_(n)^(0)仅为2.3.此外,由于钴基催化剂的加氢能力较强,甲烷选择性较高.在稳定性方面,虽然二者均有不同程度的失活,但ZnAlO_(x)/SAPO-11催化

关 键 词：Pore-mouth catalysis Shape-selective catalysis Bifunction SYNGAS GASOLINE 

分 类 号：TE626.21[石油与天然气工程—油气加工工程]