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BACKGROUND: Syngas conversion to olefins via Fischer‐Tropsch Synthesis (FTs) route and then subsequently into aromatics (syngas−olefins−aromatics (SOA)) was considered a promising industrialization route due to its ability to match reaction temperatures between syngas to olefins (300–400 °C) and olefins to aromatics (300–500 °C). In this reaction route, the syngas to olefin process can be efficiently and easily realized by Fe‐based FTs catalysts. However, the aromatization process occurring over the zeolite catalyst was still considered a big challenge due to zeolites' complex topology, variable morphology, and elusive acidic properties. RESULTS: A series of ZSM‐5 zeolites with different morphologies, including nano ellipsoid, nano cube, nano aggregate, nano bead, and nano pile were successfully synthesized. The effects of the ZSM‐5 zeolite's morphology and reaction temperature on the aromatics synthesis from syngas based on a modified FTs route were systematically studied. CONCLUSION: In all the studied ZSM‐5 zeolites, the nano cube ZSM‐5 zeolite (Z5‐NC) zeolite had the best aromatization ability. The hybrid catalyst combination of FeMnK&Z5‐NC obtained the highest xylene selectivity of 12% (2.8% + 9.2%), and its total aromatics selectivity was also the highest (42.5%). The study on reaction temperature suggested that a higher reaction temperature (320–360 °C) could efficiently impede the formation of CO2. However, the selectivity of aromatics was restrained to around 44% at higher temperatures because a high temperature facilitated the hydrocracking of higher hydrocarbons, leading to the increase of the selectivity of lighter CH4 and paraffin. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Reduction process is a key step to fabricate metal-zeolite catalysts in catalytic synthesis. However, because of the strong interaction force, metal oxides in zeolites are very difficult to be reduced. Existing reduction technologies are always energy-intensive, and inevitably cause the agglomeration of metallic particles in metal-zeolite catalysts or destroy zeolite structure in severe cases. Herein, we disclose that zeolites after ion exchange of ammonium have an interesting and unexpected self-reducing feature. It can accurately control the reduction of metal-zeolite catalysts, via in situ ammonia production from 'ammonia pools', meanwhile, restrains the growth of the size of metals. Such new and reliable ammonia pool effect is not influenced by topological structures of zeolites, and works well on reducible metals. The ammonia pool effect is ultimately attributed to an atmosphere-confined self-regulation mechanism. This methodology will significantly promote the fabrication for metal-zeolite catalysts, and further facilitate design and development of low-cost and high-activity catalysts. Reduction process is a key step to fabricate metal zeolite catalysts, but existing reduction technologies are always energy intensive and inevitably cause the agglomeration of metallic particles or destroy zeolite structure. Here the authors find that zeolites after ion exchange of ammonium display an interesting and unexpected self-reducing feature. [ABSTRACT FROM AUTHOR]

Herein, a simple and green quasi‐solid‐phase (QSP) method for facile synthesis of proton‐type ZSM‐5 avoiding use of excessive water, dry gel, Na+ cation and fluoride is reported. Crystallization by using the stoichiometric amount of TPAOH (tetrapropylammonium hydroxide) at 180 °C for only 12 h gave well‐structured HZSM‐5 crystals with high specific surface area of 429 m2 g−1 and high thermal stability. 5MRs was observed to closely relate the formation of MFI structure and QSP method exhibits shorter induction period (t0), higher nucleation rate (Vn), and faster growth rate (Vg). Moreover, HZ‐12–180 showed extremely better and rather stable catalytic activity for methanol‐to‐propylene reaction by comparison with commercial HZSM‐5. [ABSTRACT FROM AUTHOR]

The oriented conversion of CO2 into target high‐value chemicals is an effective way to reduce carbon emissions, but still presents a challenge. In this communication, we report the oriented conversion of CO2 into value‐added aromatics, especially para‐xylene, in a single pass by combining core–shell structured Zn‐doped H‐ZSM‐5 (Zn‐ZSM‐5@SiO2) and a Cr2O3 component. Through precise regulation of the acidity of Zn‐ZSM‐5@SiO2, high para‐xylene selectivity (38.7 % in the total products) at a CO2 conversion of 22.1 % was achieved. Furthermore, a CO2‐assisted effect in the synthesis of aromatics during the tandem process has been clarified through a control experiment. The CO2 reactant can act as a hydrogen acceptor to accelerate the dehydrogenation of alkenes, intermediates in the synthesis of aromatics, thereby increasing the driving force towards aromatics in the tandem reaction process. Tandem CO2 conversion: A capsule catalyst with Zn‐doped H‐ZSM‐5 (Zn‐ZSM‐5) as core and amorphous SiO2 as shell (Zn‐ZSM‐5@SiO2) has been prepared and combined with Cr2O3 as a methanol synthesis catalyst to realize the direct conversion of CO2 into value‐added aromatics, especially para‐xylene, in a tandem process (see figure). [ABSTRACT FROM AUTHOR]

A ZnCrOx-ZnZSM-5 composite catalyst was used for CO2 hydrogenation into hydrocarbons especially aromatics (Aro). 81.1% Aro selectivity in C5+ hydrocarbons (mainly C5–11) was obtained at 320 °C, corresponding to 19.9% CO2 conversion, 29.8% total hydrocarbons (HCt) selectivity and 69.7% C5+ selectivity in HCt. Our optimized STY of Aro is the highest ever reported. [ABSTRACT FROM AUTHOR]

A facile synthesis route, named dual-layer crystal growth method, was developed for preparing Pd-based zeolite capsule catalyst. The millimeter-sized zeolite capsule catalyst (Pd/SiO 2 -SZ) with a core-shell structure was prepared by a developed dual-layer crystal growth method: coating Silicalite-1 and H-ZSM-5 zeolite orderly as double shells encapsulating the Pd/SiO 2 core catalyst. We employed the prepared Pd/SiO 2 -SZ zeolite capsule catalyst for the direct synthesis of liquefied petroleum gas (LPG) from syngas (CO + H 2 ). In the reaction, the zeolite capsule catalyst showed excellent LPG selectivity than the single core catalyst of Pd/SiO 2 and the physical mixture catalyst prepared by a simply mixing core and shell catalysts. The Pd/SiO 2 -SZ realized the highest LPG selectivity of 34.4% with CO conversion of 14.1%. Moreover, the optimal reaction temperature and pressure in the reaction for LPG direct synthesis from syngas over Pd/SiO 2 -SZ catalyst were 623 K and 5.0 MPa, respectively. The high performance of zeolite capsule catalyst Pd/SiO 2 -SZ was attributed to the enforced mass transfer diffusion from inside to outside of the catalyst. [ABSTRACT FROM AUTHOR]

A kind of core–shell catalyst with Fe–Zn–Zr as the core and a zeolite (HZSM-5, Hbeta, and HY) as the shell was synthesized by a simple cladding method. The catalyst has an obvious confinement effect on the synthesis of isoalkanes by CO2 hydrogenation. Especially, the Fe–Zn–Zr@HZSM-5–Hbeta catalyst with a double-zeolite shell exhibits an extraordinary high i-HC/t-HC ratio. [ABSTRACT FROM AUTHOR]

A hierarchical meso/macroporous zeolite-supported Co catalyst (Co/ASB) was designed and employed for the direct synthesis of isoparaffins. The hierarchical porous zeolite (ASB) was developed by a steam-assisted crystallization method using alumina-modified meso/macroporous silica as the precursor. Structural characterization indicated that the as-synthesized ASB exhibited nanosized β-zeolite crystallites and a hierarchical meso/macroporous structure. The activity of the Co/ASB catalyst was much higher than that of conventional Co catalysts supported on SiO2 (Co/SiO2) and H-β-zeolite (Co/B). A high isoparaffins selectivity of 30.5 % was obtained from Co/ASB because of the hydrocracking/isomerization of long-chain hydrocarbons at the strong acidic sites of the β-zeolite. Furthermore, as a result of the fast diffusion of syngas in the unique hierarchical pores, the methane selectivity of Co/ASB was lower than that of Co/B. [ABSTRACT FROM AUTHOR]

Fused iron (FI), is a general Fischer-Tropsch synthesis (FTS) catalyst and can be used to convert syngas (CO+H2) into normal hydrocarbons. The syntheses of HZSM-5 or H-β zeolite-shell encapsulated catalysts for FTS have been reported previously, however, conventional zeolite-shell synthesis generally employs an organic template, which is neither economic nor environmentally benign. Here we report the synthesis, without using an organic template, of a millimeter-sized defect-free capsule catalyst covered by a MOR zeolite shell (thickness of 23 μm) on FI pellets. The capsule catalyst (HMOR/FI) exhibited excellent performance for FTS, greatly increasing the selectivity of middle isoparaffins. Compared with the pure FI catalyst, the CO conversion of the HMOR/FI capsule catalyst increased remarkably and the iso/ n ratio was almost 8 times that of the pure FI catalyst. This report provides an effective route to synthesize a capsule catalyst, which can reduce costs effectively and is also more environmentally benign than the current conventional zeolite-shell synthesis. [ABSTRACT FROM AUTHOR]

Highlights: [•] The core–shell-like capsule catalyst was prepared by physical coating method. [•] The new physical coating method was simple to prepare capsule catalyst. [•] The core–shell-like structure has the confinement effect on STD reaction. [Copyright &y& Elsevier]

Abstract: A well-designed zeolite capsule catalyst with a Core (Fe/SiO2)-Shell (Silicalite-1) structure was successfully prepared by zeolite seeding and then zeolite shell growing via secondary hydrothermal method. The characterization on this zeolite capsule catalyst indicated that it had a compact, defect-free zeolite shell enwrapping core catalyst tightly. The application of this zeolite capsule catalyst was the direct synthesis of light alkenes from syngas via Fischer–Tropsch synthesis (FTS) reaction. This zeolite capsule catalyst exhibited excellent abilities compared with the traditional FTS catalyst, both on the controlled synthesis of the desirable light alkenes and the suppressing formation of the undesired long-chain hydrocarbons. [Copyright &y& Elsevier]

Abstract: A compact, integral zeolite shell of H-ZSM-5 was directly crystallized on the surface of fused-iron catalyst pellet by a hydrothermal synthesis method. The synthesized catalyst has a core–shell structure without pinholes and cracks. For the reaction of direct synthesis of isoparaffin from syngas, the formation of C10+ hydrocarbons is suppressed completely on this core–shell catalyst, and the middle isoparaffins become the main products. Especially, desirable low methane selectivity is achieved. The core–shell structure of the catalyst provides a tailor-made confined reaction environment with spatially confined effect and shape selectivity, where isoparaffins escaping from outer surface of one core–shell catalyst hardly enter another core–shell catalyst via surface zeolite shell, due to its large steric obstacle, ensuring the elevated isoparaffin selectivity. Furthermore, this type of core–shell catalyst has very high membrane area per unit reactor volume and easy to be prepared, in contrast to the conventional membrane reactor. [Copyright &y& Elsevier]

Three kinds of H-ZSM-5 zeolite capsule catalysts were prepared on Co/SiO2 catalyst pellets of different sizes. Characterization of the catalysts indicated that a defect-free H-ZSM-5 membrane had been constructed successfully on the Co/SiO2 surface. The smaller Co/SiO2 pellets were favorable for zeolite capsule growth under the same synthesis conditions. Zeolite capsule catalysts, especially the catalysts with smaller pellet sizes, had a higher isoparaffin selectivity compared with conventional FTS Co/SiO2 catalyst and mixed catalyst of Co/SiO2 with H-ZSM-5 zeolite. [ABSTRACT FROM AUTHOR]

Molybdenum-zeolite catalysts always suffer from severe carbon deposition and rapid deactivation in the methane dehydroaromatization (MDA) process. Herein, we present a strategy that controls spatial distance between Mo species and HMCM-22 zeolite over Mo/HMCM-22 catalysts, to inhibit the severe carbon deposition. Our characterization analyses demonstrate that the Mo/HMCM-22 catalysts possess the same active components, but the spatial distance plays a key role in determining product selectivity in the MDA process. The MDA performance reveals that Mo/HMCM-22-MM (mechanical milling) catalyst, with a medium spatial distance between Mo species and HMCM-22 zeolite, significantly inhibits carbon deposition and produces high selectivity to benzene. This work shows that spatial distance between molybdenum and zeolite is an important property for suppressing carbon deposition and improving benzene selectivity in MDA process. [ABSTRACT FROM AUTHOR]

Even though tremendous progress has been made on modified Fischer-Tropsch synthesis (FTS) multifunctional catalyst that composed of Fe-based component and acidic zeolite H-ZSM-5 for CO 2 hydrogenation into value-added chemicals, the structure-function relationship between the acidic zeolite H-ZSM-5 and product distribution is still under debate. Herein, a series of H-ZSM-5 zeolites with different Al locations and acidic properties are fabricated by varying the synthesis raw agents and conditions. After combining with the carbon-encapsulated Fe-based catalyst for alkenes synthesis from CO 2 hydrogenation, aromatics are directionally produced from the ellipsoidal H-ZSM-5 with Al species mainly located at the intersection of straight and sinusoidal channels, while the main products shift to iso-paraffins for the H-ZSM-5 with pillared nanosheet morphology owing to its Brønsted acid site-rich property. The Al location in H-ZSM-5 and the corresponding acidic property are systematically investigated, and the theoretical simulations illustrate that the Al species at the intersection channels could lower the energy barrier of key aromatization step. The Al richly located at straight/sinusoidal would boost the isomerization reaction. Our work not only clarifies the structure-function relationship of acidic zeolite H-ZSM-5 in valuable chemicals synthesis from CO 2 hydrogenation but also provides a novel protocol for controlled synthesis. [Display omitted] • H-ZSM-5 with different Al location and acidic property were prepared by various method. • Al location and acid property were investigated by experimental and theoretical calculation. • The structure-function relationship between H-ZSM-5 and product distribution was built. • Al at the channel intersection can boost aromatics synthesis, otherwise promote isomerization. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new way to direct conversion of isobutyl alcohol to jet-range hydrocarbons. • We used dealuminization method to effectively adjust the pore structure and acidity of Beta zeolite. • The increased ratio of Lewis/Bronsted acidic sites was promoted the oligomerization reaction to form jet fuels. Various dealuminum methods of zeolite Beta to generate the jet fuels by converting isobutyl alcohol has been investigated in detail. And related factors of the zeolite catalyst such as acid site, pore structure, and pore size which can influence reactive activity, were also studied utilizing XRD, SEM, XRF, Nitrogen adsorption-desorption, NH 3 -TPD, Py-FTIR, and 27Al solid-state NMR. Removal of extra-framework aluminum or part of framework aluminum by hydrochloric acid dealumination, is able to improve the diffusion property of the products in the channel of zeolite Beta via increasing the ratio of Lewis/Brønsted. Consequently, isobutyl alcohol can be quantitatively oligomerized over dealuminated zeolite Beta with the selectivity of C 8−16 exceeding 50 % at a conversion of 98 %. Moreover, the deactivated catalyst can be easily regenerated by calcining it in flowing air. High conversion, high jet fuels selectivity, and facile regeneration make it an attractive potential catalyst for isobutyl alcohol oligomerization reaction. [ABSTRACT FROM AUTHOR]

Direct synthesis of aromatics from syngas provides a promising approach for the production of fine chemicals from non-petroleum carbon resources. In this study, direct conversion of syngas into aromatics was investigated over a serial of bifunctional catalysts coupling ZnCrO x oxides and H-ZSM-5 zeolites with different morphologies. Detailed investigation showed that the CO conversion was positively correlated with the Brønsted acid sites, and the differences in aromatics selectivity and aromatics distribution on different bifunctional catalysts with different morphologies of H-ZSM-5 zeolites were attributed to the synergistic effects of acidity and particle size. For nano-type zeolites, changes in acidity might not have a significant effect on aromatics selectivity, while the transfer of intermediate species on coffin-type zeolites was mainly influenced by acidity. Moreover, for different morphology zeolites of nano-type n-Z5-125 and coffin-type c-Z5-100 with similar acidity, the side reactions in syngas aromatization on the former were 1.7 times higher than those on the latter. The reactants diffused more readily on TPAOH treated c-Z5-150-0.1 M, which promoted olefins cyclization and further increased the aromatics selectivity from 69.8% to 74.8%. [Display omitted] • The CO conversion in STA is positively correlated with the Brønsted acid sites. • H-ZSM-5 with external framework Al and short b-axis easily forms C 8 + aromatics. • TPAOH-treated c-Z5-150 zeolite is effective in enhancing the aromatics selectivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Z0.8C/Z5 is effective for the one-step aromatization process from syngas. • The non-stoichiometric spinel brings more amorphous ZnO and oxygen vacancies. • The presence of ZnO and oxygen vacancies together pull the CO conversion. Bifunctional catalysts composed of ZnCrO x oxide and ZSM-5 were widely used in syngas-to-aromatics (STA). The CO conversion on bifunctional catalysts was generally higher than that on oxide catalysts attributed to the pulling effect of zeolite, but the key factor for the improvement of CO conversion was still short of systematical explanation. In this work, the degree of nonstoichiometric spinel of ZnCrO x (ZxC) oxides was finely tuned through modulating the ratio of Zn/Cr, which could significantly influence the catalytic behaviors of ZnCrO x /ZSM-5 catalysts for the CO hydrogenation to aromatics. The increase of nonstoichiometric spinel corresponded to the increase of oxygen vacancies and the enhancement of Zn-Cr synergistic effect, which promoted the activation of H 2 and CO, leading to a dramatic increase of CO conversion. The work revealed that the action of ZnO and oxygen vacancies was the key factor for CO pulling in ZnCrO x oxide and ZSM-5 catalyzed STA reaction. [ABSTRACT FROM AUTHOR]

Abstract: A tailor-made silicalite-1 membrane encapsulated catalyst with a size in millimeters has been directly synthesized over the activated-carbon supported Rh catalyst pellet to form a core–shell structure (S1/Rh/A.C.) by a hydrothermal synthesis method. For the reaction of hydroformylation of 1-hexene, the encapsulated catalysts present perfect catalytic performance for both the conversion and the normal to iso ratio of the aldehyde products. Increasing in the thickness of the silicalite-1 membrane can improve the selectivity of the normal products, but the reaction conversion decreases significantly. However, the modification of the encapsulated catalyst by tetraethyl orthosilicate (TEOS) can reduce the zeolite crystalline gaps to improve the normal aldehyde selectivity and to keep the similar 1-hexene conversion compared with that of the S1/Rh/A.C. catalyst. This encapsulated catalyst is efficient to produce and separate the aimed product from the multiple products in one-step with the spatial confined structure of the catalytic-inert silicalite-1 membrane. [Copyright &y& Elsevier]

The catalytic performance of CO 2 hydrogenation to liquid fuels over a bifunctional catalyst can be efficiently enhanced via simply tuning the microenvironment properties of ZSM-5 zeolite. [Display omitted] • K-Fe/C and tailor-made ZSM-5 are coupled together for CO 2 hydrogenation. • Surface acid properties of ZSM-5 can be regulated through different ion-exchange strategies. • Alkali K+ ions are effective in reducing strong acids, boosting up C 5+ hydrocarbon selectivity. Catalytic conversion of greenhouse CO 2 into valuable chemicals or fuels is highly attractive in terms of sustainable development. The chemical inertness of CO 2 molecules and high kinetic barriers for C–C propagation hinder its efficient utilization. Here we report a bifunctional catalyst composed of K-Fe/C and zeolite that efficiently produced liquid fuels via simply tuning the microenvironment properties of ZSM-5 zeolite. The catalysts are characterized by Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), X-ray diffractometer (XRD), temperature programmed desorption (NH 3 -TPD), X-ray photoelectron spectroscopy (XPS). K-Fe/C catalyst is mainly responsible for the formation of olefins, while ZSM-5 catalyst is mainly responsible for olefin secondary reaction, such as aromatization, isomerization, and cracking reaction. Surface acid properties of ZSM-5 can be well regulated through different ion-exchange strategies (NH 4 +, K+, Na+, Mg2+, Cu2+, Cs2+, La3+, Ce2+, Mn2+), in which the strong surface acid properties of ZSM-5 are eliminated with the utilization of K+-ion exchange strategy and then it presents a high C 5+ selectivity by suppressing the light saturated hydrocarbons formation. This work provides new insights or facile catalyst treatment for the efficient production of liquid fuels from CO 2 hydrogenation via tuning surface microenvironment properties of ZSM-5 zeolite. [ABSTRACT FROM AUTHOR]

• Silylated Ga/Z5 catalysts were used in propane dehydroaromatization. • An appropriate SiO 2 content on external surface was beneficial to cover strong BAS. • Sufficient weak acid was vital to propane dehydroaromatization. • The undesired cracking reaction was successfully depressed on the external surface. • Extended duration of CLD process narrowed the micropore mouth size of Ga/Z5. Dehydroaromatization of propane to high value-added aromatics, especially benzene, toluene and xylene (BTX), has attracted widespread attention. Many works have been done to improve the catalytic performance of gallium loaded HZSM-5 catalysts. However, there were few reports focused on reducing the cracked by-products, such as methane and ethylene, derived from propane cracking reaction on external Brønsted acidic sites of zeolite. Herein, chemical liquid deposition (CLD) method was adopted to passivate the external strong Brønsted acid of Ga/HZSM-5, aiming to increase the most value-added BTX production by suppressing the undesired propane cracking reaction. The content of deposited SiO 2 on the external surface of zeolite was tunable by varying the amount of liquid deposition reagent and duration time of CLD process. The results showed that an appropriate content of SiO 2 on external surface of catalyst was beneficial to disable the external strong Brønsted acid sites. Due to depressing the undesired propane cracking reaction, BTX selectivity of 55% with propane conversion of 49% was achieved on Ga/Z5-4Si catalyst, higher than those of Ga/HZSM-5. Otherwise, prolonging the duration time of CLD process narrowed the micropore mouth size of zeolite, which could enhance the shape selective effect of Ga/ZSM-5 to increase the proportion of para-xylene in total xylene products. [ABSTRACT FROM AUTHOR]

Effects of different mordenite (MOR) zeolite synthesis conditions, such as salt additive, hydrothermal time, hydrothermal temperature, and ultrasonic assistance, on dimethyl ether (DME) carbonylation were studied systematically in this work. Salt as additives being introduced into hydrothermal system obviously promoted the crystallinity and morphology of MOR. With the increase of hydrothermal time and temperature, a better crystallinity was obtained on the sample. However, a higher hydrothermal temperature of 180 °C led to a slightly decreased crystallinity. The MOR catalyst with NaCl as the additive and hydrothermal treatment at 130 °C for 48 h realized a better DME carbonylation activity with 50% DME conversion and almost 100% methyl acetate (MA) selectivity. In addition, H-MOR-UT, a MOR zeolite prepared with the assistance of ultrasonic treatment, showed a special morphology consisting of lots of MOR nanosheets with a width of around 70 nm. Here, this H-MOR-UT realized an enhanced catalytic stability and the highest DME conversion of 70%, about 5 times higher than the reference MOR zeolite prepared by traditional method. The strikingly excellent catalytic performance was attributed to its more acid content, stronger acid strength and smaller grain size. Image 1 • Effects of MOR synthesis conditions on DME carbonylation were studied systematically. • Addition of salt obviously promoted the crystallinity and morphology of MOR. • Different hydrothermal temperature affected the location of Al in MOR. • Nano-MOR derived from ultrasonic treatment realized better catalytic performance. [ABSTRACT FROM AUTHOR]