Kenta Iyoki

Improving the stability of porous materials for practical applications is highly challenging. Aluminosilicate zeolites are utilized for adsorptive and catalytic applications, wherein they are sometimes exposed to high-temperature steaming conditions (∼1000 °C). As the degradation of high-silica zeolites originates from the defect sites in their frameworks, feasible defect-healing methods are highly demanded. Herein, we propose a method for healing defects to create extremely stable high-silica z

The crystallization of zeolites, a disorder-to-order transformation of aluminosilicates, has not been thoroughly understood because the nucleation events in the amorphous matrix are difficult to recognize from the diverse structural changes, especially for the dense hydrogel systems. Therefore, relationships between the synthesis conditions, the generated amorphous species, and the crystallization behavior of zeolites remain unclear. Herein, by comparatively investigating the structural evolutio

Abstract The synthesis of MTW-type aluminosilicate zeolites in the absence of organic structure-directing agents (OSDAs) was successfully attained by the addition of calcined ZSM-12 seeds to (Li, Na)-aluminosilicate gels. In this system, Li cation plays a crucial role in the growth of the MTW crystals.

Hollow aluminosilicate zeolite beta was successfully synthesized by adding CIT-6, that is, zincosilicate zeolite, which has the same topology as beta, as seeds to the Na-aluminosilicate gel without the need for organic structure-directing agents. One important factor in the successful organic structure-directing agent (OSDA)-free synthesis of hollow beta crystals is the solubility of the seed crystals in alkaline media. CIT-6 was less stable than aluminosilicate zeolite beta in alkaline media an

Small-pore zeolites are gaining increasing attention owing to their superior catalytic performance. Despite being critical for the catalytic activity and lifetime, postsynthetic tuning of bulk Si/Al ratios of small-pore zeolites has not been achieved with well-preserved crystallinity because of the limited mass transfer of aluminum species through narrow micropores. Here, we demonstrate a postsynthetic approach to tune the composition of small-pore zeolites using a previously unexplored strategy

Seed-directed synthesis of zeolite without using organic structure-directing agents (OSDAs) has been considered to be a low-cost, environmentally friendly technique, potentially for application in the commercial manufacture of zeolites. The synthesis of zincosilicate zeolites by this method is thought to be more difficult than the aluminosilicate and borosilicate analogues, mainly because of the highly dissolution of zincosilicates in alkali solutions and the lack of comprehensive, structural in

For the preparation of zeolites, ultrasonication is an efficient pretreatment that homogenizes the reactant mixture prior to hydrothermal synthesis. However, very few studies directly employ ultrasonication during hydrothermal synthesis, and the effect of ultrasonication on zeolite crystallization has not been fully understood yet. Herein, we report the crystallization behavior of ZSM-5 zeolite in the presence of ultrasonication. We demonstrated that the crystallization time decreases with the i

The crystallization of zeolites from dense hydrogel usually requires a long synthesis period, which results in products in the form of polycrystalline aggregates with a broad particle size distribution. In the present study, we demonstrated that the crystallization of mordenite in an organic-free dense-hydrogel system (0.275 Na2O:0.025 Al2O3:1 SiO2:25 H2O) can be triggered using an intermediate stirring method—quenching and opening the reactor during synthesis and using a spatula to stir the sub

The STW-type zeolite is attractive for developing novel enantioselective syntheses/separation of chiral compounds because it is the only chiral zeolitic microporous material whose enantioenriched synthesis has been achieved. In addition to the conventional industries in which zeolites are used, STW should have diverse industrial applications in the pharmaceutical and food industries. However, the toxic and caustic fluoride required for synthesizing STW severely hinders its commercialization by m

Abstract To open up the possibility of synthesizing useful substances from CO2, we have developed new catalysts that hydrogenate CO2 to methanol with high yield at 300 °C and higher. In this study, methanol synthesis via CO2 hydrogenation at 250–350 °C and 10 bar was investigated using Zr-based metal oxide catalysts, MZrOx (M = Al, Mn, Cu, Zn, Ga, and In). The different metals (M) determined the suitable reaction temperature wherein the maximum yield of methanol was obtained. CuZrOx was a suitab

Hierarchical micro–mesoporous silica has been synthesized by solid-phase conversion of molecular crystals of an alkoxy derivative of a cubic siloxane unit (Si8O12) as a molecular building unit. Seven methoxy groups and one adamantoxy group are introduced in a cage by the reaction of octa(hydridosilsesquioxane) (H8Si8O12) with the corresponding alcohols, which are then eliminated in a step-by-step manner. First, the methoxy groups are hydrolyzed by simply dispersing the precursor powder in an aci