核壳结构催化剂Cr-Zn@SiO_2@SAPO-34催化合成气直接转化制低碳烃的性能（英文）

合成气直接转化高选择性制烃类产物仍是巨大的挑战.本文合成了以Cr-Zn氧化物为核,Si O2为中间过渡层,再通过原位水热合成覆盖一层SAPO-34分子筛为壳的核壳结构催化剂.合成气转化反应结果显示,与纯Cr-Zn金属氧化物相比,核壳结构催化剂将产物分布由甲醇和甲烷移动至C2–C4烃(所有烃类产物中占66.9%).这表明核壳结构催化剂用于合成气一步法直接转化制液化石油气的反应具有可行性,但是催化剂结构和组成有待于进一步优化,以提高其催化反应性能.     

壳层厚度对骨架Fe@HZSM-5核壳催化剂费托合成催化性能的影响

在不同的水热合成时间下, 以铁铝合金为铁源和铝源, 四丙基氢氧化铵为分子筛的模板剂和抽提合金中的铝的碱, 一步制得了以骨架铁为核、不同厚度的HZSM-5分子筛为壳的Raney Fe@HZSM-5催化剂. 采用元素分析、氮物理吸附、X射线粉末衍射、氨脱附、扫描电子显微镜等手段, 考察了水热时间对催化剂基本物化性质的影响. 随着水热时间的延长, HZSM-5分子筛壳层不断增厚, 结晶度不断增大, 但分子筛组成基本不变, 酸量与分子筛壳层厚度正相关. 在费托合成反应中, Raney Fe@HZSM-5核壳催化剂上的CO转化率和汽油段产物选择性随分子筛壳层厚度呈火山型变化趋势, 说明反应需要适宜的酸量, 酸量过低或过高均不利于得到高的催化活性及汽油段产物选择性. 在水热合成时间为4 d制得的Raney Fe@HZSM-5核壳催化剂上, 当CO转化率为92%时, C₅~C₁₁汽油段产物选择性可达71%, 异正比为1.9. 当合成气中的n(H₂)/n(CO)比从2降为1时, 汽油段产物选择性和异正比进一步提高至73%和2.1, 显示了将该催化剂用于煤基或生物质基合成气转化为高辛烷值汽油的良好潜力.     

合成气一步法制备二甲醚核壳结构催化剂的制备及其反应性能

以生物质(葡萄糖、蔗糖、淀粉)为模板剂,通过水热合成法制备具有核壳结构的CuO-ZnO-Al₂O₃@Al₂O₃复合催化剂,该催化剂以甲醇合成催化剂CuO-ZnO-Al₂O₃为核,甲醇脱水催化剂Al₂O₃为壳.SEM-EDS对催化剂核壳结构的表征发现,通过改变水热合成温度和合成时间可以调变催化剂中Al₂O₃壳层的厚度.将该复合催化剂用于合成气直接制备二甲醚的反应,在空速1 500 mL/(h·g_cat)、温度260 ℃、压力5.0 MPa的条件下,CO转化率和二甲醚选择性分别达到35.2%和61.1%.     

孔口催化促进双功能催化剂上合成气制异构烷烃

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ZnAlOx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C5–C11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ZnAlOx/SAPO-11催化剂上异构烷烃与正构烷烃的比例(C0iso/C0n)达到13.相较于ZnAlOx/SAPO-11,ZnA-lOx/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ZnAlOx/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C5–C11选择性可达70％,但C0iso/C0n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ZnAlOx/SAPO-11催化剂在反应100 h后,C5–C11选择性依然保持在75％左右,而Co/H-meso-ZSM-5上C5–C11选择性降至64％.通过对ZnAlOx/SAPO-11催化剂上产物的细致分析,发现异构烷烃以单支链的异构体为主.结合正丁烷和异丁烷的等温吸附实验以及的动力学尺寸,推断异构烷烃的形成遵循孔口催化机理,即线性烃类的异构化只能在SAPO-11分子筛的孔口附近发生.生成单支链碳氢化合物是孔口催化的一个特征.由于单支链烷烃相对于双支链烷烃不易裂解,因而生成的单支链C5–C11异构烷烃在ZnAlOx/SAPO-11催化剂上稳定存在,抑制了裂解副反应的发生.综上所述,本文发展了一类氧化物/分子筛双功能催化剂用于转化合成气直接制C5–C11异构烷烃,证实了异构烷烃的生成遵循孔口催化机理,是孔口催化在合成气转化中的应用案例.同时本文系统比较了其与传统的分子筛负载费托合成催化剂之间的性能差异,为设计双功能催化剂实现特定目标产物的选择性合成提供了研究思路.     

孔口催化促进双功能催化剂上合成气制异构烷烃

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ZnAlOx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C5–C11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ZnAlOx/SAPO-11催化剂上异构烷烃与正构烷烃的比例(C0iso/C0n)达到13.相较于ZnAlOx/SAPO-11,ZnA-lOx/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ZnAlOx/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C5–C11选择性可达70％,但C0iso/C0n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ZnAlOx/SAPO-11催化剂在反应100 h后,C5–C11选择性依然保持在75％左右,而Co/H-meso-ZSM-5上C5–C11选择性降至64％.通过对ZnAlOx/SAPO-11催化剂上产物的细致分析,发现异构烷烃以单支链的异构体为主.结合正丁烷和异丁烷的等温吸附实验以及的动力学尺寸,推断异构烷烃的形成遵循孔口催化机理,即线性烃类的异构化只能在SAPO-11分子筛的孔口附近发生.生成单支链碳氢化合物是孔口催化的一个特征.由于单支链烷烃相对于双支链烷烃不易裂解,因而生成的单支链C5–C11异构烷烃在ZnAlOx/SAPO-11催化剂上稳定存在,抑制了裂解副反应的发生.综上所述,本文发展了一类氧化物/分子筛双功能催化剂用于转化合成气直接制C5–C11异构烷烃,证实了异构烷烃的生成遵循孔口催化机理,是孔口催化在合成气转化中的应用案例.同时本文系统比较了其与传统的分子筛负载费托合成催化剂之间的性能差异,为设计双功能催化剂实现特定目标产物的选择性合成提供了研究思路.     

Cu改性的FeMg@SiO2纳米级核壳催化剂实现合成气一步法制备液化石油气(英文)

本实验系统研究了纳米级核壳催化剂由合成气经费托合成路线一步法直接制备液化石油气。通过采用共沉淀法、改性溶胶-凝胶法和浸渍法相结合的方法将Cu纳米颗粒浸渍在介孔二氧化硅壳包覆的FeMg催化剂上,所制备的Cu/FeMg@SiO₂纳米核壳催化剂的物理化学性质通过一系列的表征技术进行分析,如XRD、TEM、N₂吸附-脱附、H₂-TPR,XPS和CO₂-TPD等。Cu/FeMg@SiO₂纳米核壳催化剂在液化石油气合成反应中表现出较高的CO转化率(96.6%)和较低CO₂选择性(21.9%),其中,液化石油气的选择性到达37.9%。反应结果表明,SiO₂壳层抑制了CH₄的形成,有助于增加长链产物。同时,高的CO转化率归因于Cu/FeMg@SiO₂上活性金属Cu元素在SiO₂壳上的高分散,进一步促进了烯烃加氢和C₅₊烃类产物的裂解。本实验中所提出的催化剂制备方法...     

分子筛结构设计及酸性调控在合成气催化转化中的应用研究进展

合成气催化转化是生物质或煤炭资源化清洁利用的重要路径,由此可获得烯烃和芳烃等多种高附加值碳氢化合物。分子筛由于具有独特的亚纳米孔道、可控活性位及分子择形性等优点,常被作为载体或直接作为活性组分用于催化合成气转化中C-C的形成和断裂等关键步骤。本综述总结了以分子筛负载金属、氧化物-分子筛(OX-ZEO)双功能以及核壳结构催化剂等直接催化转化合成气制备碳氢化合物的研究进展。重点介绍分子筛结构和酸性对反应路径和机理以及产物分布的影响,并展望分子筛催化合成气转化的未来发展方向。     

含有多级孔复合分子筛的复合催化剂上合成气一步制二甲醚

以Beta分子筛为核、Y型分子筛为壳层的多级孔复合分子筛(BFZ)作为甲醇脱水催化剂用于固定床中合成气一步法制备二甲醚,并与纯Y型分子筛进行了比较,研究了二甲醚合成催化反应活性与甲醇脱水催化剂孔道结构和酸性之间的关系.结果表明,复合分子筛HBFZ具有中等强度的酸性和中孔孔道结构,有利于提高合成气制备二甲醚的催化反应活性.二甲醚直接合成催化剂由工业CuO/ZnO/Al₂O₃催化剂(CZA)与分子筛(HBFZ、HY)采用机械混合方法制备;催化评价结果显示,CZA/HBFZ比CZA/HY具有更优的催化活性和稳定性.在250 ℃, 5.0 MPa 和 1 500 h^-1的反应条件下,CZA/HBFZ催化剂上CO的转化率和DME的选择性分别达到94.2%和67.9%.     

核壳型复合分子筛ZSM-5/Nano-β的合成与表征

以ZSM-5小晶粒为核相材料, 用聚二烯丙基二甲基氯化铵(PDDA)进行表面预处理后, 黏附nano-β晶种并焙烧制得核相晶种, 再在壳层晶化生长体系中通过水热合成得到ZSM-5/nano-β有序的核壳分子筛. 产物的物相和结构通过XRD, SEM, TEM以及N₂吸附/脱附分析表征, 通过对比发现, β壳层的合成以白炭黑为硅源比用正硅酸乙酯(TEOS)更好. 通过NH₃-TPD表征, 以及1,3,5-三甲苯裂化转化反应对分子筛的性能进行了考察, 结果表明, 核壳分子筛通过调变组成分子筛的酸性, 从而大大提高了材料的催化裂化性能, 同时延缓了失活速率.     

纳米HZSM-5催化剂催化烃类转化反应

制备了纳米(20~50 nm)HZSM-5催化剂, 用XRF, TEM和NH3-TPD等手段对催化剂进行了表征. 以正辛烷及苯和正辛烷混合物的转化为模型反应, 研究了单烃和混合烃在纳米HZSM-5催化剂上的转化行为, 考察了反应条件对产物分布的影响. 结果表明, 纳米HZSM-5沸石催化剂具有很强的烃类转化能力, 烃类通过芳构化、 异构化和烷基化等反应转化为高辛烷值的异构烷烃和芳烃, 产物中异构烷烃(C4~C6)和芳烃的质量分数超过90%. 直链烷烃转化为芳烃以生成苯环为主, 混合烃转化为芳烃以苯和小分子烃的烷基化为主. 控制反应条件可抑制苯和C+9芳烃的生成. 产物分析结果表明, 烃类在纳米HZSM-5催化剂上的裂解、芳构化和异构化等遵循正碳离子机理.     

Na-W-Mn/SiO2催化剂表面甲烷脉冲反应Ⅱ. 多组分Na、 W、 Mn/SiO2催化剂

制备了多组分Na,W,Mn/SiO2催化剂，在ITD（Ion Trap Detector)装置上进行了催化剂表面晶格氧脱附前后的甲烷恒温脉冲反应（CH4－CTPR）。研究结果表明，Na-W/SiO2催化剂表面晶格氧，具有较高的CH4转化率和C2烃选择性，并对C2H6的生成起着重要的作用，Na-Mn/SiO2催化剂表面晶格氧，也具有较高的CH4转化率和C2烃选择性，但对C2H6的形成有一定的诱导期；W－Mn/SiO2催化剂表面晶格氧，对CH4的转化和CO2的生成具有很高初活性，但对C2烃的选择性较低；Na-W-Mn/SiO2催化剂表面晶格氧，具有很高的CH4转化率和C2烃定向选择性，这是由于Na,W,Mn各组分协同作用的结果。     

Multiple-functional capsule catalysts: a tailor-made confined reaction environment for the direct synthesis of middle isoparaffins from syngas

A capsule catalyst for isoparaffin synthesis based on Fischer-Tropsch reaction was designed by coating a H-ZSM-5 membrane onto the surface of the pre-shaped Co/SiO(2) pellet. Morphological and chemical analysis showed that the capsule catalyst had a core-shell structure. A compact, integral shell of H-ZSM-5 crystallized firmly on the Co/SiO(2) substrate without crack. Syngas passed through the zeolite membrane to reach the Co/SiO(2) catalyst to be converted, and all hydrocarbons formed with straight chain structure must enter the zeolite channels to undergo hydrocracking as well as isomerization in this tailor-made confined reaction environment. A narrow, anti-Anderson-Schultz-Flory law product distribution was observed on these capsule catalysts. Contrary to a mechanical mixture of H-ZSM-5 and Co/SiO(2), C(10+) hydrocarbons were suppressed completely on this novel capsule catalyst, and the selectivity of middle isoparaffins was considerably improved. The carbon number distribution of the products depended on the thickness of the zeolite membrane, and it was possible to selectively synthesize specified distillates, such as gasoline-range, or heavier hydrocarbons from syngas directly, by simply adjusting the thickness of the zeolite membrane of the capsule catalyst. This kind of capsule catalysts can be extended to various consecutive reaction systems as the shell and core components are independent catalysts for different reactions. At the same time, shape selectivity and space-confined effects can be expected for the reactant, intermediates and product of the sequential reactions.     

Cu/ZnO@H-β-P催化剂在合成气制备液化石油气反应中的性能研究

采用共沉淀法制备Cu/ZnO催化剂、水热合成法制备H-β分子筛、通过物理包膜法制备了具有核壳结构的Cu/ZnO@H-β-P催化剂,并用于合成气制备液化石油气(LPG)反应。通过XRD、NH3-TPD、BET和SEM-EDS等手段对催化剂进行了表征,利用固定床连续反应装置对催化剂进行了活性评价。结果表明,Cu/ZnO@H-β-P催化剂是具有中孔的核壳结构材料,其协同作用打破了原有的热力学平衡,促进了甲醇→DME→LPG串联反应的连续进行。与物理混合的Mix-Cu/ZnO-H-β催化剂相比,Cu/ZnO@H-β-P催化剂的CO转化率和LPG选择性更高,空速和反应温度对催化剂活性影响明显,最佳空速和反应温度分别为2 400 h~(-1)和350℃。使用Cu/ZnO@H-β-P催化剂在最佳条件下进行合成气制备LPG反应,CO转化率达到了57.22%,LPG选择性达到了60.52%。     

Designing a capsule catalyst and its application for direct synthesis of middle isoparaffins

A catalyst in the form of a capsule catalyst was prepared by coating HZSM5 membrane on a preshaped Co/SiO2 catalyst pellet. The capsule catalyst with HZSM5 membrane exhibited excellent selectivity for light hydrocarbon synthesis, especially for isoparaffin synthesis from syngas (CO + H2). Long-chain hydrocarbon formation was totally suppressed by the zeolite membrane. The modification of membrane and core catalyst significantly improved the catalytic properties of these new kinds of capsule catalysts.     

Shape‐Selective Zeolites Promote Ethylene Formation from Syngas via a Ketene Intermediate

Syngas conversion by Fischer–Tropsch synthesis (FTS) is characterized by a wide distribution of hydrocarbon products ranging from one to a few carbon atoms. Reported here is that the product selectivity is effectively steered toward ethylene by employing the oxide‐zeolite (OX‐ZEO) catalyst concept with ZnCrO_x‐mordenite (MOR). The selectivity of ethylene alone reaches as high as 73 % among other hydrocarbons at a 26 % CO conversion. This selectivity is significantly higher than those obtained in any other direct syngas conversion or the multistep process methanol‐to‐olefin conversion. This highly selective pathway is realized over the catalytic sites within the 8‐membered ring (8MR) side pockets of MOR via a ketene intermediate rather than methanol in the 8MR or 12MR channels. This study provides substantive evidence for a new type of syngas chemistry with ketene as the key reaction intermediate and enables extraordinary ethylene selectivity within the OX‐ZEO catalyst framework.     

间苯二酚-甲醛树脂凝胶对Co/SiO_2催化剂费-托性能的影响(英文)

采用共沉淀法制备了高Co含量的Co/SiO2费托合成催化剂,并向其中添加一定含量的间苯二酚-甲醛树脂凝胶.结果表明,催化剂在393K干燥时,树脂会发生分解,因而仅有少量的含碳凝胶残留在催化剂中.然而,少量碳凝胶的存在显著增加了催化剂的还原度和金属钴的分散度,致使催化剂表面产生更多的活性金属Co,同时,催化剂的孔径也有所增大,因此Co/SiO2催化剂具有更高的反应活性及高碳烃选择性.其中80%Co/SiO2-C催化剂活性及高碳烃的选择性与我们前期报道的一种高活性的80%Co-8%ZrO/SiO催化剂相近.     

Conversion of Oxygenates to Aromatic Hydrocarbons on a Commercial Zeolite Catalyst: Comparison of Ethanol and Dimethyl Ether

Conversion of oxygenates to aromatic hydrocarbons in the syngas medium in the presence of a commercial zeolite-containing catalyst was studied. The influence of pressure on aromatization of dimethyl ether and ethanol was examined. At 400°C, an increase in the pressure from 0.1 to 3.0–10.0 MPa leads to a sharp increase in the yield of aromatic compounds. Dimethyl ether and ethanol, which are isomers belonging to different classes of compounds, were compared as substrates in conversion to aromatic hydrocarbons. At elevated pressure, dimethyl ether compared to ethanol exhibits higher selectivity in formation of the desired synthesis products, allowing synthesis of liquid hydrocarbons with increased content of arenes.

     

Design and Synthesis of Powerful Capsule Catalysts Aimed at Applications in C1 Chemistry and Biomass Conversion

Tandem catalytic reaction is a promising strategy to improve the utilization efficiency of energy and resources. The conventional hybrid catalysts cannot readily realize the precisely controlled synthesis of target products due to the unrestricted, open reaction environment. Assembling the hybrid catalyst with multiple active sites into core‐shell structured capsule catalyst is one of the most effective ways to enhance the selectivity of desired products during a tandem catalysis process, because the core‐shell structure offers a space‐confined reaction field and synergistic effect. This review describes our recent progresses on the design and synthesis of core‐shell structured zeolite capsule catalysts developed for C1 chemistry and biomass conversion. The various synthesis methods for constructing the well‐defined zeolite capsule catalysts are described in detail. The applications of the capsule catalysts in catalysis, including the middle isoparaffins synthesis from syngas, one‐step synthesis of dimethyl ether, and liquid‐phase tandem reaction of glycerol conversion, are discussed, respectively. Our perspectives regarding the challenges and opportunities for future research in the field are also provided.     

C−C Bond Formation in Syngas Conversion over Zinc Sites Grafted on ZSM-5 Zeolite

Despite significant progress achieved in Fischer–Tropsch synthesis (FTS) technology, control of product selectivity remains a challenge in syngas conversion. Herein, we demonstrate that Zn²⁺-ion exchanged ZSM-5 zeolite steers syngas conversion selectively to ethane with its selectivity reaching as high as 86 % among hydrocarbons (excluding CO₂) at 20 % CO conversion. NMR spectroscopy, X-ray absorption spectroscopy, and X-ray fluorescence indicate that this is likely attributed to the highly dispersed Zn sites grafted on ZSM-5. Quasi-in-situ solid-state NMR, obtained by quenching the reaction in liquid N₂, detects C₂ species such as acetyl (-COCH₃) bonding with an oxygen, ethyl (-CH₂CH₃) bonding with a Zn site, and epoxyethane molecules adsorbing on a Zn site and a Brønsted acid site of the catalyst, respectively. These species could provide insight into C−C bond formation during ethane formation. Interestingly, this selective reaction pathway toward ethane appears to be general because a series of other Zn²⁺-ion exchanged aluminosilicate zeolites with different topologies (for example, SSZ-13, MCM-22, and ZSM-12) all give ethane predominantly. By contrast, a physical mixture of ZnO-ZSM-5 favors formation of hydrocarbons beyond C₃₊. These results provide an important guide for tuning the product selectivity in syngas conversion.     

C−C Bond Formation in Syngas Conversion over Zinc Sites Grafted on ZSM‐5 Zeolite

Despite significant progress achieved in Fischer–Tropsch synthesis (FTS) technology, control of product selectivity remains a challenge in syngas conversion. Herein, we demonstrate that Zn²⁺‐ion exchanged ZSM‐5 zeolite steers syngas conversion selectively to ethane with its selectivity reaching as high as 86 % among hydrocarbons (excluding CO₂) at 20 % CO conversion. NMR spectroscopy, X‐ray absorption spectroscopy, and X‐ray fluorescence indicate that this is likely attributed to the highly dispersed Zn sites grafted on ZSM‐5. Quasi‐in‐situ solid‐state NMR, obtained by quenching the reaction in liquid N₂, detects C₂ species such as acetyl (‐COCH₃) bonding with an oxygen, ethyl (‐CH₂CH₃) bonding with a Zn site, and epoxyethane molecules adsorbing on a Zn site and a Brønsted acid site of the catalyst, respectively. These species could provide insight into C?C bond formation during ethane formation. Interestingly, this selective reaction pathway toward ethane appears to be general because a series of other Zn²⁺‐ion exchanged aluminosilicate zeolites with different topologies (for example, SSZ‐13, MCM‐22, and ZSM‐12) all give ethane predominantly. By contrast, a physical mixture of ZnO‐ZSM‐5 favors formation of hydrocarbons beyond C₃₊. These results provide an important guide for tuning the product selectivity in syngas conversion.