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Copper-ion-exchanged SSZ-13 has been demonstrated to be an effective catalyst for the ammonia selective catalytic reduction of NOx. However, the Cu-SSZ-13 is still susceptible to hydrothermal degra...

Carbon molecular sieve (CMS) membranes were prepared on the outer surface of porous ceramic tubes using a lignin-based material, organosolve-lignin, and a phenol resin, Bellpeal-S899, as precursors. Higher pyrolysis temperature resulted in higher hydrogen selectivity over oxygen or other larger gases, but hydrogen permeance decreased significantly. On the contrary, addition of a small amount of iron(III) acetate basic to the precursors improved the hydrogen selectivity but maintained the hydrogen permeance. Addition of iron compound to the precursor strongly reduced the permeances of nitrogen and methane through the resulting CMS membranes. Distribution of iron in the carbon matrix was evaluated by transmission electron microscopy energy dispersive X-ray spectroscopy (TEM-EDS) and electron probe microanalyzer (EPMA). The influence of aging on the membrane permeance was also studied. The results suggest the possibility to tune the size of ultra-micro-pores in CMS membranes using additives.

Zeolites possessing novel structures and compositions have been produced using guest organic species, which are called organic structure-directing agents (OSDAs). However, the specific roles of OSDAs have not been clarified yet. In this work, *BEA- and CHA-type zeolites are synthesized from the same starting inorganic materials but with different OSDAs, and the crystallization pathways are observed using various analytical techniques. During the synthesis of *BEA-type zeolite, the gradual evolution of the aluminosilicate structure leads to the transformation from an amorphous structure to a crystalline one. On the other hand, during the synthesis of CHA-type zeolite, a few CHA nuclei are formed in “partially-ordered amorphous species” and grow through the consumption of “buffer amorphous species” on the surfaces of CHA-type zeolite crystals. This clear difference in crystallization behaviors of the two zeolites under the same synthetic conditions is attributed to the differences in the structure-directing...

Structures of platinum and chromium supported on zeolite beta were investigated by XAFS, XPS, UV–vis, NH3-TPD, XRD, CO chemisorption, and molecular dynamics simulation. Both platinum and chromium were uniformly dispersed in the micropore of zeolite beta. Loading of chromium helped platinum to disperse highly and stabilized in the micropore of beta. Major species of platinum on PtCr/beta after calcination at 773 K was Pt2+ forming a Pt–O bond. The Pt–O bond disappeared, and a Pt–Pt bond did not appear by reducing PtCr/beta in hydrogen, accompanying formation of Pt0. Chromium was loaded as chromate anion in the micropore of zeolite. Results of molecular dynamics simulation showed that Pt2+ associated with CrO42– in the micropore of zeolite beta was more stable than those in the absence of chromium species. We concluded that CrO42– electrostatically stabilizes Pt2+ and inhibits migration and aggregation of platinum.

Organic template-free synthesis of nano-zeolite has been an important subject of both scientific and industrial applications. Most research has focused on the fabrication of nano-zeolite by a bottom up approach, that is, control of zeolite nucleation and crystal growth during the hydrothermal synthesis. This communication reports a new method for the production of nano-zeolite powder by a top-down approach. In this study, the zeolite was first milled to produce a nanopowder. This technique can cause destruction of the outer portion of the zeolite framework and hence cause pore blocking, which deactivates various properties of the zeolite. To remedy this, the damaged part was recrystallized using a dilute aluminosilicate solution after bead milling. As a result of the combination of bead milling and postmilling recrystallization, nano-zeolite A (LTA type zeolite) about 50 nm in size with high crystallinity was successfully obtained.

Single-crystalline platinum nanocubes with porous morphology were synthesized for the first time by using ethylene glycol, HCl, and polyvinylpyrrolidone as the reducing agents of H2PtCl6. The morphology and size distribution of the Pt particles formed were studied with a high-resolution transmission electron microscope and selected-area electron diffraction pattern. By controlling the material concentrations and reaction temperature and period, Pt single crystals about 5 nm in size were formed in the first stage of the reduction process that had {100} facets, which were stacked one on top of the other, forming porous nanocubes 20-80 nm in length. The synthesized Pt nanocubes exhibited enhanced catalytic activity for methanol oxidation.

In this study, a simple anodic oxidation process resulted in the successful synthesis of novel N-ion-doped TiO(2) with one-dimensionally aligned and large-sized mesopores. TiO(2) obtained by this anodic oxidation process possessed the high values of specific surface area and a large amount of one-dimensional mesopores with 30-50 nm diameter. Furthermore, X-ray photoelectron spectroscopy and UV-vis results suggested the possibility that these TiO(2) products were composed of a N-ion-doped powder. Thus, novel structured TiO(2) with large-sized mesopores was simply synthesized by an anodic oxidation of Ti metal in a nitric acid solution. These uniquely nanostructured mesoporous TiO(2) products will expand possibilities for applying mesoporous TiO(2) in new fields.

A comprehensive study on a series of highly stable calcium containing mesoporous aluminosilicate molecular sieves (CaAlMMSH) having different acidic properties has been made by varying the Si/Ca ratio in synthesis gels. The structural, physical, and porous properties of these microporous/mesoporous composite materials were characterized by X-ray diffraction, N2 adsorption/desorption isotherm measurements, solid-state 27Al and 29Si magic angle spinning NMR, and variable-temperature hyperpolarized 129Xe NMR, Fourier transform infrared (FTIR) and diffuse reflectance FTIR spectroscopies. As compared to the parent AlMMSH materials, the incorporation of excessive amount of calcium tends to result in an overall increase in acid amount while at the expense of strong acid sites. The CaAlMMSH materials were found to have superior catalytic activities than AlMMSH in the amidation of palmitic acid with N-hexadecylamine. However, no significant enhancement in catalytic activity for the esterification of palmitic acid ...

This article reports the structural variation of SBA-type mesostructured silica formed from a mixture of tetraethyl orthosilicate (TEOS), alkyltrimethylammonium bromides, and 1,3,5-trialkylbenzenes under acidic conditions. Swollen 2D hexagonal mesophases were formed from the silica source and hexadecyltrimethylammonium bromide (C16TAB) with varying amounts of trimethylbenzene (TMB) and triethylbenzene (TEB), whereas drastic structural changes were observed with triisopropylbenzene (TIPB). Characterization by X-ray diffraction and transmission electron microscopy observation revealed that the mesophase was changed from hexagonal p6mm to cubic Pm3n to cubic Fm3m with increasing amounts of TIPB. Thus, the addition of TIPB leads to the preferential formation of spherical micelles rather than the swelling of rodlike micelles. When tetradecyltrimethylammonium bomide (C14TAB) was used, similar structural changes were triggered by smaller amounts of TIPB; however, almost no structural change was observed when octadecyltrimethylammonium bromide (C18TAB) was used. These findings provide a better understanding of the roles of 1,3,5-trialkylbenzenes in the structural control of silica-alkyltrimethylammonium mesophases.

We have succeeded in the fabrication of distorted cubic R-3m mesoporous silica film with 3D open mesostructure providing high pore accessibility from the surface-air interface of the film. The film fabrication involves a unique approach of adding 1,3,5- triisopropylbenzene (TIPB) to the silica/cetyltrimethylammoniumbromide (CTAB) coating sol during its preparation. The addition of TIPB induces the formation of spheroid micelles, promoting R-3m mesostructure in the film. This phase does not exist in the corresponding binary phase diagram of CTAB surfactant.