A series of ZnO-ZrO2 solid solutions with different Zn contents were synthesized by the urea co-precipitation method, which were coupled with H-ZSM-5 zeolite to form bifunctional catalysts. As a new benzene alkylation reagent, syngas was used instead of methanol to realize the efficient conversion of syngas and benzene into toluene and xylene. A suitable ratio of ZnO-ZrO2 led to the significant improvement in the catalytic performance, and a suitable amount of acid helped to increase the selectivity of toluene/xylene and reduce the selectivity of the by-products ethylbenzene and C9+ aromatics. The highest benzene conversion of 89.2% and toluene/xylene selectivity of 88.7% were achieved over 10% ZnO-ZrO2&H-ZSM-5 (Si/Al = 23) at a pressure of 3 MPa and a temperature of 450 °C. In addition, the effect of the zeolite framework structure on product distribution was examined. Similar to the molecular dynamics of aromatic hydrocarbons, H-ZSM-5 zeolites comprise 10-membered-ring pores, which are beneficial to the activation of benzene; hence, the conversion of benzene is higher. H-ZSM-35 and H-MOR zeolites exhibited small eight-membered-ring channels, which were not conducive to the passage of benzene; hence, the by-product ethylbenzene exhibits a higher selectivity. The distance between the active centers of the bifunctional catalysts was the main factor affecting the catalytic performance, and the powder mixing method was more conducive to the conversion of syngas and benzene. © 2021

A series of ZnO-ZrO2 solid solutions with different Zn contents were synthesized by the urea co-precipitation method, which were coupled with H-ZSM-5 zeolite to form bifunctional catalysts. As a new benzene alkylation reagent, syngas was used instead of methanol to realize the efficient conversion of syngas and benzene into toluene and xylene. A suitable ratio of ZnO-ZrO2 led to the significant improvement in the catalytic performance, and a suitable amount of acid helped to increase the selectiv-ity of toluene/xylene and reduce the selectivity of the by-products ethylbenzene and C-9(+) aromatics. The highest benzene conversion of 89.2% and toluene/xylene selectivity of 88.7% were achieved over 10% ZnO-ZrO2&H-ZSM-5 (Si/Al = 23) at a pressure of 3 MPa and a temperature of 450 degrees C. In addition, the effect of the zeolite framework structure on product distribution was examined. Similar to the molecular dynamics of aromatic hydrocarbons, H-ZSM-5 zeolites comprise 10-membered-ring pores, which are beneficial to the activation of benzene; hence, the conversion of benzene is higher. H-ZSM-35 and H-MOR zeolites exhibited small eight-membered-ring channels, which were not conducive to the passage of benzene; hence, the by-product ethylbenzene exhibits a higher selectivity. The distance between the active centers of the bifunctional catalysts was the main factor affecting the catalytic performance, and the powder mixing method was more conducive to the conversion of syngas and benzene. ?? 2021 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd.

费托合成（FTS）对天然气、煤炭和生物质向清洁运输燃料和增值化学品的转化至关重要。传统上，用于FTS的负载型铁催化剂主要是以氧化铝和二氧化硅为载体。然而，金属与载体的相互作用阻碍了活性相碳化铁的形成，使得催化剂活性较低。本文通过乙二胺四乙酸（EDTA）络合浸渍制备了Fe/Al2O3催化剂，通过带正电荷的羟基（OH2+）与[Fe（EDTA）]-配合物阴离子之间的库仑相互作用来提高氧化铝载体上铁物种的分散度。采用X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线光电子能谱（XPS）、比表面积（BET）、原位红外（In-situ IR）等手段进行表征分析。结果表明，添加EDTA有助于增强Fe的抗烧结性。在煅烧络合浸渍制备样品的过程中，EDTA可以分解为具有还原性质的有机小分子，将催化剂中的铁物种还原为Fe2+，有利于催化剂的还原；更多活性中心增强了催化剂对CO的吸附量。原位红外实验表明，EDTA辅助制备的催化剂更容易富集活性物种，从而提高CO的转化率。调节体系中碱金属钠的含量改善了烃内产物分布。在较低的氢碳比（H2/CO=1/1）下，EDTA络合制备的Fe-Na/Al2O3催化剂显示出高的CO转化率（88.5%）以及最大的C2～C4=和C5～C11选择性，总选择性达71.2%。

Capturing and utilization of carbon dioxide (CO2) not only leads to effective use of carbon resources, but also alleviates environmental pollution caused by increasing concentration of CO2, thus making it a hot research topic in recent years. In this study, a series of highly dispersed iron-cobalt (Fe-Co) catalysts was prepared by ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) modification, which could efficiently convert CO2 into high value-added chemicals (C2-C4= and C5-C11). X-ray diffraction (XRD) analysis showed that the addition of a small amount of Co and EDTA-2Na contributed to enhance the sintering resistance of Fe species. During the calcination process, EDTA4- can be decomposed into small organic molecules with reducibility, thus promoting the reduction of iron species. The CO temperature-programmed desorption (CO-TPD) results showed that cobalt enhanced the adsorption and activation of intermediate CO on NaxFe-Co catalyst, thereby promoting the catalytic conversion of CO2. The complexation of EDTA promotes the synergistic effect of Fe-Co bimetals, enhances the chemical adsorption of CO2. Sodium in EDTA-2Na promotes the surface basicity of the catalysts, which is favored for improving the product distribution of hydrocarbons. At lower H2/CO2 (1/1) ratio, the EDTA-2Na modified Fe-Co/Al2O3 catalyst exhibited high conversion of CO2 (32.8 %) and excellent selectivity toward high value-added chemicals. The selectivity of by-product CO was only 8.1 %; and C2-C4= (32.5 %) and C5-C11 (46.3 %) accounted for ∼79 % selectivity among the hydrocarbons generated. © 2020 Elsevier Ltd.

Capturing and utilization of carbon dioxide (CO2) not only leads to effective use of carbon resources, but also alleviates environmental pollution caused by increasing concentration of CO2, thus making it a hot research topic in recent years. In this study, a series of highly dispersed iron-cobalt (Fe-Co) catalysts was prepared by ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) modification, which could efficiently convert CO2 into high value-added chemicals (C-2-C-4(=) and C-5-C-11). X-ray diffraction (XRD) analysis showed that the addition of a small amount of Co and EDTA-2Na contributed to enhance the sintering resistance of Fe species. During the calcination process, EDTA4 can be decomposed into small organic molecules with reducibility, thus promoting the reduction of iron species. The CO temperature-programmed desorption (CO-TPD) results showed that cobalt enhanced the adsorption and activation of intermediate CO on NaxFe-Co catalyst, thereby promoting the catalytic conversion of CO2. The complexation of EDTA promotes the synergistic effect of Fe-Co bimetals, enhances the chemical adsorption of CO2. Sodium in EDTA-2Na promotes the surface basicity of the catalysts, which is favored for improving the product distribution of hydrocarbons. At lower H-2/CO2 (1/1) ratio, the EDTA-2Na modified Fe-Co/Al2O3 catalyst exhibited high conversion of CO2 (32.8 %) and excellent selectivity toward high value-added chemicals. The selectivity of by-product CO was only 8.1 %; and C-2-C-4(=) (32.5 %) and C-5-C-11 (46.3 %) accounted for similar to 79 % selectivity among the hydrocarbons generated.

A novel hierarchical tungsten-substituted Silicalite-1 zeolite with the highly interconnected hollow structure (HWS-1) was synthesized for the first time by post-treating the purely microporous tungsten-substituted Silicalite-1 (WS-1) through simultaneous desilication and tungstation, in which a combination of sodium hydroxide and tetrapropyl ammonium hydroxide (TPAOH) was used to achieve a systematic balance between dissolution and recrystallization and further promote the synchronous tungstation with using sodium tungstate dihydrate as a tungsten source. Under an optimum addition ratio of NaOH/TPAOH, the resulted HWS-1 exhibited not only well retained microporosity and crystallinity but also obviously enlarged external surface area and mesopore volume in contrast to the parent WS-1. Furthermore, the effective tungstation also facilitated the substitution and increased the amount of coordinated W species in zeolite frameworks. The catalytic performance of HWS-1 was evaluated by the epoxidation of cyclohexene with using H2O2 as oxidant. Benefited by the highly interconnected hollow structure and more accessible active sites on the enlarged external surface, the HWS-1 catalyst revealed a higher catalytic activity with improved cyclohexene conversion than WS-1. Moreover, it was found that a significant positive effect on promoting epoxidation was achieved by tungsten-substituted Silicalite-1 (WS-1 and HWS-1) catalysts reflecting at a much higher selectivity of epoxide (>79%) in comparison with titanium-substituted Silicalite-1 (TS-1) (similar to 50% selectivity of epoxide), due to their superior hydrophobicity and suitably weaker acidity, which further demonstrated the potential application of the developed hierarchical tungsten-substituted Silicalite-1 as a candidate catalyst for epoxidation and other selective oxidation reactions.

In this study, a series of H-BZSM-5 catalysts, rich in porous structures, were prepared by a template-free method followed by an alkali treatment, each of which was combined with a Zn-ZSM-S catalyst to produce aromatic hydrocarbons from methanol via low-carbon olefins. By separately designing suitable catalysts that satisfy the needs of these two stages, and appropriately matching these two catalysts, the stability of the catalyst and single-pass aromatic production is expected to improve. For two-step coupling to produce aromatic hydrocarbons, the HBZS-x-AT catalyst (H-BZSM-5 treated with NaOH + Al(NO3)(3)) was selected for the conversion of methanol to low-carbon olefins. Adding an appropriate amount of aluminum during the alkali treatment can suppress the over-etching of the silicon-rich region inside the crystal and, at the same time, aluminum atoms and boron atoms undergo isomorphous substitution. While introducing continuous mesopores, some strong acid sites are introduced, significantly improving the stability of B-ZSM-S in the methanol-to-olefin (Step 1) reaction. The HBZS-27-AT catalyst has a suitable catalyst lifetime, high C-2(=)-C-4(=) intermediate product selectivity, with a total selectivity of 73%, which is beneficial to subsequent olefin aromatization. The Zn-ZSM-S catalyst was selected for the preparation of aromatics from low-carbon olefins (Step 2). Considering the effect of the composite method and ratio of the two kinds of catalysts on the performance of the two-step coupled aromatic production, it is concluded that, when the composite catalyst has upper and lower layer filling and the ratio is 3:7, compared with the traditional Zn-modified ZSM-5, the stability of the catalyst was increased from 3 to 194 h, and the single-pass aromatic production increased from 0.15 to 4.98 g/g catalyst.

A highly efficient tandem catalyst comprising an iron-potassium bimetal-modified alkaline Al2O3 catalyst and a phosphorus-modified ZSM-5 zeolite (denoted as Fe-K/a-Al2O3&P/ZSM-5) for directly hydrogenating CO2 to aromatics reported. The hydrogenation conversion route of CO2 -> olefins -> aromatics on the tandem catalyst is demonstrated. The Fe-K/a-Al2O3 catalyst solely serves as a metal active center to hydrogenate CO2 to lower olefin intermediates with high selectivity, and the P/ZSM-5 zeolite, which provides acid sites, Byproduct can rapidly convert lower olefin intermediates to aromatics by polymerization and dehydrocyclization. Moreover, the addition of alkaline Al2O3 as the support leads to the improved dispersion of the Fe-K bimetal and subsequently promotes CO2 adsorption, thereby inhibiting the adsorption of H-2 and benefitting the formation of lower olefin intermediates. Strong acid sites of HZSM-5 zeolites with low Si/Al ratios are essential for the formation of aromatics. The appropriate proximity of two active components in the tandem catalyst is critical to the highly selective catalytic process for hydrogenating CO2 to aromatics. The granule-mixing catalyst maintains strong acidity and CO2 adsorption capacity, boosting the hydrogenation of CO2 to aromatics. Phosphorus modification changes the acid strength of HZSM-5 zeolites and increases the amount of medium-strength acid sites, further promoting the generation of aromatics, which exhibits a 36.4% CO2 conversion as well as a 35.5% selectivity for aromatics among the carbon products within CO2 and the tandem catalyst is suitable at a low H-2/CO2 ratio with merely a 10.2% byproduct CO selectivity. In addition, HZSM-5 with a low phosphorus loading is conducive to the aromatization of lower olefins, and the phosphorus loading of 0.8 wt % is found to be suitable.

Surface silicon-rich ZSM-5 zeolites were prepared by surface chemical modification; their pore structure and acid properties were characterized by XRD, nitrogen sorption, TEM, NH3-TPD and Py-FTIR spectroscopy. The catalytic performance of modified ZSM-5 zeolites in the conversion of methanol to p-xylene and lower olefins was investigated. The results show that the introduction of Zn in ZSM-5 can change part of the strong acid sites into the medium ones and increase the Zn-Lewis acid sites with dehydrogenation capacity, which can enhance the selectivity to ethene and propene. The modification with Mg can not only adjust the pore shape selectivity, but also increase the amount of Lewis acid sites, which is beneficial to the formation of p-xylene. Through multiple silicon depositions from different silicon sources, SiO2 is uniformly deposited on the outer surface of modified ZSM-5 catalysts, which can modulate the acid properties and pore structure and thereby further improve the selectivity to p-xylene and ethene and propene. By using these modification approaches, the selectivity to p-xylene and ethene and propene reaches 61%, with 87.1% of p-xylene in the xylenes product, 97.8% of ethene in C2 hydrocarbons, and 90.6% of propene in C3 hydrocarbons. © 2020, Science Press. All right reserved.

A highly efficient tandem catalyst comprising an iron-potassium bimetal-modified alkaline Al2O3 catalyst and a phosphorus-modified ZSM-5 zeolite (denoted as Fe-K/a-Al2O3&P/ZSM-5) for directly hydrogenating CO2 to aromatics is reported. The hydrogenation conversion route of CO2 → olefins → aromatics on the tandem catalyst is demonstrated. The Fe-K/a-Al2O3 catalyst solely serves as a metal active center to hydrogenate CO2 to lower olefin intermediates with high selectivity, and the P/ZSM-5 zeolite, which provides acid sites, can rapidly convert lower olefin intermediates to aromatics by polymerization and dehydrocyclization. Moreover, the addition of alkaline Al2O3 as the support leads to the improved dispersion of the Fe-K bimetal and subsequently promotes CO2 adsorption, thereby inhibiting the adsorption of H2 and benefitting the formation of lower olefin intermediates. Strong acid sites of HZSM-5 zeolites with low Si/Al ratios are essential for the formation of aromatics. The appropriate proximity of two active components in the tandem catalyst is critical to the highly selective catalytic process for hydrogenating CO2 to aromatics. The granule-mixing catalyst maintains strong acidity and CO2 adsorption capacity, boosting the hydrogenation of CO2 to aromatics. Phosphorus modification changes the acid strength of HZSM-5 zeolites and increases the amount of medium-strength acid sites, further promoting the generation of aromatics, which exhibits a 36.4% CO2 conversion as well as a 35.5% selectivity for aromatics among the carbon products within CO, and the tandem catalyst is suitable at a low H2/CO2 ratio with merely a 10.2% byproduct CO selectivity. In addition, HZSM-5 with a low phosphorus loading is conducive to the aromatization of lower olefins, and the phosphorus loading of 0.8 wt % is found to be suitable. © 2020 American Chemical Society.