Yoshiharu Yoneyama

Confinement effect and synergistic function of H-ZSM-5/Cu-ZnO-Al2O3 capsule catalyst for one-step controlled synthesis.

Dimethyl ether (DME) is an industrially important intermediate, as well as a promising clean fuel, but the effective production through traditionally consecutive steps from syngas to methanol and then to DME has been hindered by the poorly organized structure of the conventional physical mixture catalyst. Here, a novel zeolite capsule catalyst possessing a core-shell structure (millimeter-sized core catalyst and micrometer-sized acidic zeolite shell) was proposed initially through a well-designed aluminum migration method using the core catalyst as the aluminum resource and for the first time was applied to accomplish the DME direct synthesis from syngas. The selectivity of the expected DME on this zeolite capsule catalyst strikingly exceeded that of the hybrid catalyst prepared by the traditional mixing method, while maintaining the near-zero formation of the unexpected alkanes byproduct. The preliminary methanol synthesis reaction on the core catalyst and the following DME formation from methanol inside the zeolite shell cooperated concertedly and promoted mutually. This zeolite capsule catalyst with a synergetic confinement core-shell structure can be used to efficiently realize the combination of two and more sequential reactions with many synergistic effects.

A new method of bimodal support preparation and its application in Fischer–Tropsch synthesis

A simple preparation method of bimodal silica was developed by introducing SiO2 sol into large pores of SiO2 gel pellet directly. Cobalt supported on this kind of bimodal silica support, exhibited remarkably high activity in liquid-phase Fischer–Tropsch synthesis, which was attributed to its bimodal structure having not only a higher surface area but also a larger pore size. The support with a large surface area allowed highly dispersed cobalt particle and its large pore size improved the diffusion of reactants and products.

Continuous synthesis process of methanol at low temperature from syngas using alcohol promoters

Abstract A continuous process for low-temperature methanol synthesis from CO/CO 2 /H 2 based on the promoting effect of alcohol solvent has been developed. 2-butanol, acting as a promoter, with the aid of Cu/ZnO solid catalyst, realized the high efficient synthesis of methanol with one-pass methanol yield of 47.0% and methanol selectivity of 98.9% at temperature as low as 443 K and 50 bar, which can be a very promising method for methanol production at low temperature.

Filter and buffer-pot confinement effect of hollow sphere catalyst for promoted activity and enhanced selectivity

To efficiently utilize the catalyst active sites and simultaneously enhance target hydrocarbon selectivity in Fischer–Tropsch synthesis (FTS), herein, we demonstrate a promising Co–Al2O3 hollow-sphere catalyst prepared by a two-pot route including hydrothermal carbonization and wet impregnation. Benefiting by plentiful mesopores on the shell, reactants could access the cavity inside and the active sites on the inner surface for further FTS reaction. Compared with conventional solid catalyst, the hollow structure provided a “buffer-pot” effect, where feed gas and preliminary product from the shell could mix completely at a low flow rate. Heavy hydrocarbons were further confined, leading to enhanced formation of lighter C5–C11 components, which more readily escaped out through the mesoporous shell, which thus played a “filter” role. Additionally, increased acidity on the shell generated more iso-paraffins and olefins in the final product. This concept displayed a great superiority in improving active metal activity and selective production from multiple products compared with conventional supported catalysts.

Highly Efficient Alcohol Oxidation on Nanoporous VSB‐5 Nickel Phosphate Catalyst Functionalized by NaOH Treatment

Selective catalytic oxidation of alcohols to corresponding aldehydes or ketones under mild conditions with molecular oxygen has attracted much attention in recent decades, because the aforementioned reaction is the foundation of many important fine chemical processes, which are currently being subjected to intense economical and environmental scrutiny. From the viewpoint of industry, the heterogeneous catalytic oxidation of alcohols over solid catalysts in liquid phase under mild conditions is in high demand because of several limitations of homogeneous catalysis, such as corrosion of the reactor wall, product purification, catalyst activity loss, extra engineering on recovery, and recycling of catalyst. In general, solid catalysts prepared by conventional loading methods often suffer the leaching of active species 2] due to the corrosion of liquid-phase reactants, products, or solvents, which are frequently excellent chelating agents, resulting in the irreversible deactivation of the catalyst. Therefore, complicated preparation methods are often necessary to protect or immobilize the active phase. Much effort has been devoted to alcohol oxidation, commonly using noble metal catalysts such as Ru, Pd, Pt, or Au, and rarely using transition metal catalysts such as Cu, Co, Ti, Ni, Mn. Although the noble metal-based catalysts, especially Ru, show promising activity, cheaper transition metal catalysts are always desired. The aerobic oxidation of various alcohols was reported over a nickel-containing hydrotalcite-like anionic clay catalyst, and either Ni + in association with aluminum oxide or octahedrally coordinated Ni + was thought to be responsible for the activation of molecular oxygen. 13] Furthermore, high valence Ni + species could act as a catalyst for the oxidation of benzyl alcohol, while simultaneously acting as a stoichiometric oxidant to convert the alcohol into the acid. Nanoporous VSB-5, a nickel phosphate based on octahedral NiO6 units linked by tetrahedral PO4 to build up one-dimensional 24-member ring channel structures, received much attention because of its novel properties, such as a high BET surface area and ion-exchange ability. It was applied for several purposes, such as shape-selective catalysis, hydrogen storage, and hydrogenation reactions. 18] Utilization of this easily-prepared nickel-rich nanoporous material is attractive because the catalytically active nickel centers dispersed in porous channels allow for catalyst shape selectivity and high catalytic selectivity, which are of importance in the development of green chemistry technology. Herein, we report findings about the property and catalytic behavior of VSB-5 molecular sieve that has been functionalized by simple NaOH treatment. It is to our knowledge, the first clear demonstration that an active phase of Ni(OH)2 efficiently catalyzes the oxidation of various alcohols with molecular oxygen to the corresponding aldehydes or ketones under mild reaction conditions. This active phase was prepared in situ in the channels of VSB-5 by NaOH treatment. Despite the fact that coordinatively unsaturated Ni + and octahedral NiO6 are present and accessible in the pore walls of VSB-5, 17] the calcined VSB-5 catalyst sample was inactive in the aerobic oxidation of benzyl alcohol at 353 K (Table 1,

A Catalyst for One-step Isoparaffin Production via Fischer-Tropsch Synthesis: Growth of a H-Mordenite Shell Encapsulating a Fused Iron Core

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.

Combining wet impregnation and dry sputtering to prepare highly-active CoPd/H-ZSM5 ternary catalysts applied for tandem catalytic synthesis of isoparaffins

Tuning hydrocarbon distribution in Fischer–Tropsch synthesis is greatly challenging. By employing three different pathways to deposit trace palladium on Co/H-ZSM5 catalyst, tunable isoparaffin and olefin selectivity was successfully achieved. The impregnated Pd showed poor promotion of Co dispersion and reducibility, producing a slight enhancement of FTS activity and isoparaffin selectivity. The unique mechanical stir during Pd sputtering induced re-dispersion of impregnated Co/H-ZSM5 particles and Pd was deposited with an intimate distance to Co species and with a weak interaction combining zeolite, due to which complete hydrogenation of olefins was achieved. The surface enriched Pd on pre-sputtered Co catalyst was inclined to form Pd–Co nano-alloys, suppressing the chain growth activity by excessive hydrogenation process.

A Capsule Catalyst with a Zeolite Membrane Prepared by Direct Liquid Membrane Crystallization

A sheltered existence: Direct liquid-membrane crystallization is used as a low-cost, low-waste, yet highly effective method to prepare a catalyst encapsulated by a H-β zeolite. Through vapor-liquid exchange, a continuous and sufficient, but not excessive supply of both water and template is the key part of this method.

Design of a Hierarchical Meso/Macroporous Zeolite-Supported Cobalt Catalyst for the Enhanced Direct Synthesis of Isoparaffins from Syngas

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.

Oriented synthesis of target products in liquid-phase tandem reaction over a tripartite zeolite capsule catalyst

Tandem reaction cannot readily realize the precisely controlled synthesis of target products, although it is a promising strategy to improve the utilization efficiency of energy and resources. Changing the assembly style of tandem reaction catalyst from a general hybrid mixture to a well-organized capsule is shown here to be a reasonable way to overcome this problem. In this study, we initially present a novel tripartite zeolite capsule catalyst that consists of a core (Ru/Al2O3)–microporous shell (Silicalite-1)–dopant (Pd) structure. With the liquid-phase tandem reaction of glycerol conversion as a probe reaction, we demonstrate the previously unreported superiority of this tripartite zeolite capsule catalyst on the oriented synthesis of target products. The Pd doped microporous zeolite shell constructs a confined reaction space and provides molecular screening and refining ability to this tripartite zeolite capsule catalyst, which drives it to effectively realize the controlled synthesis of desired chemicals, simultaneously depressing undesired side-reactions very much better than conventional catalyst assemblies. The concept of a catalyst encapsulated by a Pd-doped microporous zeolite shell and its application suggests new opportunities for studying the function of catalyst assembly style in varied tandem reaction systems, the correlations between catalyst assembly style and its catalytic properties, as well as the nature of catalyst active sites and reaction mechanisms.