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Nickel-supported CHA-type zeolites with different framework compositions including borosilicate, gallosilicate and aluminosilicate were synthesized. The effect of heteroatoms in the framework on th...

Fe-containing MWW zeolite catalysts in the absence (Fe-MWW) or presence of Al atoms (Fe,Al-MWW) were directly prepared by the hydrothermal synthesis approach. The nature of Fe species was systematically analyzed by UV–vis, in-situ NO adsorption FTIR spectroscopy, and H2-TPR technology. The presence of Al atoms in the synthesis gel seriously affected the chemical composition, textural properties, and the states of Fe species, hence made the catalytic activity in hydroxylation of benzene with H2O2 worse than the one without Al. Moreover, we found that the states of Fe species could be adjusted by changing the calcination temperature. The catalytic activity of Fe-MWW was improved by increasing the calcination temperature, while that of Fe,Al-MWW was weakened due to the degeneration of texture properties and the transformation of Fe species. Fe-MWW zeolite calcined at 750 °C exhibited the highest 8.3% yield and 94% selectivity to phenol in direct hydroxylation of benzene with H2O2.

H4SiW12O40 (HSiW) was supported on mesoporous silica (SBA-15), non-structured amorphous silica (AEROSIL) and γ-alumina (Al2O3) by impregnation. The supported HSiW samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms, infrared (IR) spectroscopy and ethanol dehydration reaction as a model reaction. HSiW was not highly dispersed even at 29 wt% loading, but the hexahydrate (HSiW·6H2O) was stable under evacuation below 150 °C on silica supports, while destruction of Keggin units occurred on Al2O3. IR spectra of HSiW·6H2O loaded SBA-15 and AEROSIL were analyzed in detail in combination with changes in surface area and XRD patterns. The loaded HSiW·6H2O crystals possessed weak secondary interaction with adjacent silanol groups. The crystal size was increased in three dimensions on AEROSIL by increasing loading amount, while the extension of the size to the pore direction was found on SBA-15. The number of protons in supported HSiW·6H2O was quantified by the integrated intensity of the key band of pyridinium cation (C5H5N+H) at 1538 cm−1 in IR spectra. At high loading (>29 wt%) four hydrogen atoms per Keggin unit in HSiW·6H2O were detected as proton on AEROSIL and SBA-15 with negligible amount of Lewis acid sites, while less than a half on Al2O3 with a majority of Lewis acid sites. Thus, IR method using pyridine as a probe can quantify Bronsted and Lewis acid sites in the absence of thermal decomposition of loaded HSiW·6H2O. It was also found that all the protons detected by pyridine adsorption could not catalyze the reaction over HSiW/Al2O3, suggesting the necessity of a caution to relate the acid amount measured by probe molecules to catalysis.

The synthesis of ladder polymers is still a big challenge in polymer chemistry, and in particular, there are few examples of conformationally flexible well-defined ladder polymers. Here we report an efficient and convenient route to conformationally flexible ladder polymers, which is based on a postpolymerization reaction of a rigid ladder polymer containing Tröger’s base in its main chain. The postpolymerization reaction involves sequential N-methylation and hydrolysis for the Tröger’s base unit, resulting in a diazacyclooctane skeleton that can exhibit a ring-flipping motion. Molecular dynamics simulations predicted that this motion provides conformational flexibility with the resultant ladder polymer, which was demonstrated by 1H NMR spectroscopy in solution. The presence of the diazacyclooctane units in the flexible ladder polymer allowed further functionalization through reactions involving its secondary amine moiety. The present synthetic method may lead to the development of a new class of ladder polymers that exhibit both conformational and design flexibility.

A nanoporous and large surface area (∼800 m2/g) graphene-based material was produced by plasma treatment of natural flake graphite and was subsequently surface decorated with platinum (Pt) nano-sized particles via thermal reduction of a Pt precursor (chloroplatinic acid). The carbon-metal nanocomposite showed a ∼2 wt% loading of well-dispersed Pt nanoparticles (

Graphene mesosponge (GMS) is a new class of mesoporous carbon consisting mainly of single-layer graphene walls. GMS has traditionally been synthesized via chemical vapour deposition (CVD) of methane onto a template of alumina (Al2O3) nanoparticles, which catalyses methane conversion. However, the Al2O3 template needs to be removed using costly and environmentally concerning processes such as hydrofluoric acid or concentrated base. In this work, we examine methane conversion catalysed by magnesium oxide (MgO) and utilized MgO as an alternative catalytic template. In contrast to Al2O3, a solid acid catalyst, MgO is a solid base catalyst that is also active for methane conversion into graphene sheets but dissolves easily in hydrochloric acid. We have investigated the reaction mechanism using in situ weight measurements and gas-emission analysis during CVD complemented by density functional theory calculations. We found that the pure MgO surface is activated via O-elimination with methane above 778 °C. On the activated MgO surface, methane is converted into a graphene sheet with a relatively low activation energy of 134 kJ mol−1. Once the first graphene layer is formed, the methane-to-graphene conversion rate decreases and the activation energy increases to 234 kJ mol−1, which is comparable to that reported in thermal methane-CVD on carbon. As a result of the faster growth rate of the first layer with respect to additional layers, it is easier to obtain single-graphene layers using MgO. The MgO-derived GMS has a unique combination of properties including a high surface area, developed mesopores, high oxidation resistance, significant softness and elasticity, very low bulk modulus (0.05 GPa), and force-driven reversible liquid–gas phase transition. Thus, we expect the MgO-derived GMS can be employed in a variety of applications including high-voltage supercapacitors and as a new type of heat pump based on the force-driven phase transition.

AEI-type aluminosilicate zeolites with sheet-like morphology were successfully synthesized by the crystal growth inhibitor (CGI)-assisted method, where cetyltrimethylammonium bromide (CTAB) worked as a CGI. The obtained sheet-like AEI-type aluminosilicates showed a higher yield of butenes and longer catalytic lifetime in the direct conversion of propene to butenes than the conventional sample. The improvement of catalytic performance originated from tuning the molecular diffusion in the zeolite particles. The sheet-like morphology gave a higher molecular diffusivity, and consecutive reactions were suppressed. Moreover, there was a significant difference in the product distribution of butene isomers; linear butenes and iso-butene were the dominant product over the typical AEI-type aluminosilicate with cubic particles induced by the shape selectivity into zeolitic micropores, while the sheet-like one yielded a higher selectivity for iso-butene. It was revealed that the distribution of Bronsted acid sites between internal and external surfaces could be controlled by increasing the external surface area coming from the sheet-like particles.

Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM-5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn-ZSM-5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity.

The development of the mesoporosity of zeolite frameworks is an effective method to enhance the catalytic performance in the methanol-to-olefin reaction. Mesopore-containing CON-type boroaluminosilicate zeolite was prepared by the alkaline treatment based on the post-synthetic hydrothermal treatment in NH4OH solution containing cetyltrimethylammonium bromide. The change in the concentration of NH4OH solution led to CON zeolites with different mesopore volumes. The effects of the NH4OH concentration on the structural properties of the treated samples were investigated by XRD, N2 adsorption, SEM, TEM, and 11B, 27Al, and 29Si MAS NMR analyses. In addition, in situ FTIR with pyridine and 2,4,6-trimethylpyridine as probe molecules was applied to investigate the acidic properties. In the methanol-to-olefin (MTO) reaction, the mesopore-containing CON-type zeolite showed a longer catalytic life than the parent zeolite. The enhanced catalytic properties could be attributed to the dual effects of the alkaline treatment on the porosity and acidity modification.

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 zeolites. High-silica (SiO

A method for estimating the location of Ti atoms in zeolite framework has been developed based on the difference in catalytic activity for epoxidation of 1-hexene and 2-methyl-2-pentene. We have fo...

Nanometer-sized clay, allophane, was used as the matrix for matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) and applied to the ionization of small molecules. First, the laser desorption ionization mass spectrum of cation-exchanged allophane was measured, and it was found that the cation exchange proceeded smoothly with increasing atomic number of alkali metals in the periodic table. This phenomenon was explained by considering the size of the counter anion on the allophane surface. Then, fructose was measured as the analyte using each alkali-cation-exchanged allophane as the matrix. Contrary to the measurements using allophane itself, the peak intensity of fructose decreased with increasing atomic number of alkali metals in the periodic table. This phenomenon was clarified by considering the stability of alkali cation in the presence of a surface anion, the desorption energy, and the solvation enthalpy of each alkali cation. The applicability of allophane to high molecular weight compounds was also confirmed by measuring cyclodextrin, angiotensin II, and insulin. Finally, a combination of allophane and zeolite was examined by assuming proton relay among allophane, zeolite, and analyte. As a result of proton supply from zeolite to allophane, the peak intensity of the proton sponge (1,8-bis(dimethylamino)naphthalene) was enhanced by almost 2.2 times.

A small-pore zeolite, Rho having 8-membered ring opening and 3-dimensional (3-D) channels is synthesized via a greener process, without the use of a structure-directing agent. The zeolite Rho is crystallized by a conventional hydrothermal reaction under static conditions. XRD pattern showed phase purity of RHO-type crystalline topology, and SEM images depicted polyhedral particles with bimodal size distribution. The average size of small and large sized particles are 200 nm and 1000 nm, respectively. The amount of total solid-acid sites on Rho zeolite is 2.534 mmol g−1 and BET specific surface area reached to 812 m2 g−1. The zeolite is tested for a gas-phase conversion of ethanol-to-ethylene in the temperature range of 200–400 °C. The catalytic efficiency and stability of Rho zeolite are compared with the materials extensively used in the dehydration of alcohols; a control zeolite (ZSM-5) and three different samples of γ-Al2O3. For ethanol dehydration under mild reaction conditions, the overall catalytic efficiency of Rho is superior to that of the ZSM-5 zeolite and the γ-Al2O3 materials. The strength and concentration of solid-acid sites are the main driving factors in the low-temperature dehydration of ethanol-to-ethylene.

Fe-containing MFI zeolite catalysts were prepared by different methods to obtain different Fe speciation and applied in the direct hydroxylation of benzene to phenol reaction with H2O2. The Fe speciation were characterized by UV–vis and NO adsorbed FT-IR techniques in details. The effects of various reaction parameters on the catalytic performance and the reusability of the catalyst have been studied. Under optimized reaction conditions, directly synthesized Fe-silicalite-1 showed the highest phenol yield of 5.7%, which was higher than post-synthesized Fe-silicalite-1 and Fe-ZSM-5. Furthermore, the phenol yield can be improved to 7.6% by alkaline treatment. Finally, the active Fe species for the BTP reaction were clarified.

Small-pored ( O stretching band appeared at lower frequency side on MCM-41 at a small amount of adsorption in addition to that observed on SBA-15. This result indicates the presence of the stronger interaction of cyclohexanone with MCM-41 than that with SBA-15. When the time course of the reaction was observed by in-situ IR observation, the consumption of activated carbonyl groups and the generation of 1,1-dimethoxycyclohexane, the reaction product, were confirmed. The presence of the activated cyclohexanone was most probably due to the adsorption on two (or more) OH groups in vicinity, while a non-activated species occupied a single OH group. The reaction probe IR method is thus, a direct and effective approach to extract the small differences in catalysis.

Ion-exchange of an Al-rich zeolite beta, synthesized by organic structure-directing agent-free method (Beta-OF), was studied for application as a base catalyst. While the as-synthesized Beta-OF in Na-form itself had base sites and showed moderate catalytic activity for Knoevenagel condensation, the ion-exchange with Cs+ improved the catalytic activity. For Knoevenagel condensation of benzaldehyde with ethyl acetoacetate, the catalytic activity of Beta-OF ion-exchanged with Cs+ largely surpassed that of the conventional zeolite beta with less Al content. CO2-TPD and IR observation with chloroform as a probe molecule revealed that the Cs-exchanged Beta-OF had strong base sites comparable to Cs-exchanged Y zeolite. Base strength of Beta-OF was stronger than that expected by Sanderson’s theory. A local high density of Al atoms in the framework of Beta-OF resulted in the unexpected base property and high catalytic activity.

The effect of reaction conditions for direct oxidation of methane to methanol over Fe-MFI zeolite with H2O2 has been investigated. Sulfolane has been proved to be an efficient solvent for liquid-phase methane oxidation. A sulfolane/water mixture with an appropriate proportion led to an extremely high methanol production with a high selectivity.

The basicity of lattice oxygen in H-form zeolite was characterized by the CO2-probe IR method at room temperature and in the low-pressure region. The adsorbed CO2 species on basic oxygens (>2350 cm−1) were distinguished from hydrogen-bonded (2349 cm−1) and physisorbed (2339 cm−1) species. The pairing of a basic oxygen and an acidic OH group was evidenced by quantitative ammonia adsorption, where the amount of basic oxygen was decreased linearly with the amount of acidic OH consumed by ammonia adsorption. This clearly indicates the presence of basicity on H-form acidic zeolites. The number of lattice oxygens of H-form zeolites located around Al in (AlO4)− units was affected by the environment of the central Al atoms in the framework of the zeolites. Consequently, the number of base sites was dependent on zeolite topology. Zeolites diverse in the location of T sites represented by MFI showed plural IR absorption bands of adsorbed molecular CO2 (2370–2350 cm−1) due to the presence of various types of base sites, in contrast to zeolites with fewer types of T sites, such as CHA. While CO2 adsorption onto basic metal oxides results in forming carbonate species through chemical reactions, IR observation of molecularly adsorbed CO2 could be an appropriate method to detect weakly basic sites on acid catalysts.

To fabricate a novel metallosilicate zeolite with a tridirectional pore system of 8- and 10-ring channels, direct incorporation of B, Al and Ga into small and medium pore ITQ-52 zeolite with the IFW-type topology was carried out using a phosphorus-containing organic structure-directing agent (P-OSDA, 1,4-butanediylbis[tris(dimethylamino)]phosphonium hydroxide). The solids were characterized by XRD, FT-IR, B, Al, P and Ga MAS NMR spectroscopy before and after post-synthesis treatments and steaming. It was found that the P-species derived from OSDA were decomposed by heat treatments, forming extra-framework phosphates that remain in the cavities of the zeolite. The presence of P-species not only stabilized the Al or Ga located in framework positions which adopted a reversible octahedral configuration but also decreased the acid strength of the zeolites. The catalytic performance of the Al- and Ga-containing ITQ-52 zeolites in the MTO reaction was investigated. We have found that the presence of P in ITQ-52 enhanced the catalytic life time, and that the optimum P content for the samples with Si/Al = 120 and Si/Ga = 135 were found to be P/Al = 0.17 and P/Ga = 0.14, respectively, showing a propene selectivity higher than 35%., This work was supported by Tokyo Tech World Research Hub Initiative (WRHI) Program of Institute of Innovative Research, Tokyo Institute of Technology; MINECO of Spain through the Severo Ochoa (SEV-2016-0683) and RTI2018-101784-B-I00 projects.

NaNbO3 with a cubic phase was synthesized under extremely mild conditions. Sodium niobates represented by Na7(H3O)Nb6O19·14H2O and Na2Nb2O6·H2O were formed as precursors by alkaline treatment of amorphous Nb2O5 under ambient conditions, which were converted to crystalline NaNbO3 by simple calcination at 500 ​°C. In addition, the morphology of the obtained NaNbO3 was affected by alkaline treatment time.

Two-dimensional hydrogen boride (HB) sheets were recently demonstrated to act as a solid acid catalyst in their hydrogen-deficient state. However, both the active sites and the mechanism of the catalytic process require further elucidation. In this study, we analyzed the conversion of ethanol adsorbed on HB sheets under vacuum during heating using in situ Fourier transform infrared (FT-IR) absorption spectroscopy with isotope labelling. Up to 450 K, the FT-IR peak associated with the OH group of the adsorbed ethanol molecule disappeared from the spectrum, which was attributed to a dehydration reaction with a hydrogen atom from the HB sheet, resulting in the formation of an ethyl species. At temperatures above 440 K, the number of BD bonds markedly increased in CD3CH2OH, compared to CH3CD2OH; the temperature dependence of the formation rate of BD bonds was similar to that of the dehydration reaction rate of ethanol on HB sheets under steady-state conditions. The rate-determining step of the dehydration of ethanol on HB was thus ascribed to the dehydrogenation of the methyl group of the ethyl species on the HB sheets, followed by the immediate desorption of ethylene. These results show that the catalytic ethanol dehydration process on HB involves the hydrogen atoms of the HB sheets. The obtained mechanistic insights are expected to promote the practical application of HB sheets as catalysts.

Ga-containing CON-type materials were synthesized and its catalytic performance in methanol-to-olefins (MTO) reaction were evaluated. The state of Ga atoms in the CON framework was investigated by 71Ga MAS NMR and UV–vis measurements. The effect of incorporation of Ga on the acidic properties of CON-type materials was investigated by NH3-TPD and FT-IR measurements with pyridine and CO as molecular probes. When Ga-containing CON-type zeolite was employed in MTO reaction, the yield to propylene were 60 C-atom %, as high as Al-CON, but with the lower ethylene selectivity, leading to the higher propylene-to-ethylene (P/E) ratio.

Polyoxometalate based solids are promising candidates of proton-conducting solid electrolytes. In this work, a Preyssler-type polyoxometalate is crystallized with potassium ions and poly(allylamine), which is also a good proton conductor, from aqueous solutions. Here we show that the hygroscopicity induced low durability of polyoxometalate and poly(allylamine) can be circumvented by the electrostatic interaction between the polyoxometalate and protonated amine moieties in the solid state. Crystalline compounds are synthesized with poly(allylamine) of different average molecular weights, and all compounds achieve proton conductivities of 10−2 S cm−1 under mild-humidity and low-temperature conditions. Spectroscopic studies reveal that the side-chain mobility of poly(allylamine) and hydrogen-bonding network rearrangement contribute to the proton conduction of compounds with poly(allylamine) of low and high average molecular weights, respectively. While numbers of proton-conducting amorphous polyoxometalate-polymer composites are reported previously, these results show both structure-property relationship and high functionality in crystalline composites. Polyoxometalate based solids are promising candidates for proton-conducting electrolytes but their low durability and low proton conductivities remains an on-going challenge. Here the authors describe the preparation of polyoxometalate-based solids with much improved stability and proton conductivities.

5-Hydroxymethylfurfural (HMF) is an important platform molecule, derived from biomass-based carbohydrates, for the production of renewable fuel additives, liquid hydrocarbon fuels, biopolymers, and specialty chemicals. In this study, a mesoporous carbon/silica (MCS) nanocomposite, as catalyst support, was prepared using a nanocomposite of natural rubber (NR) and hexagonal mesoporous silica (HMS) as a precursor. To obtain a series of acidic, basic, and bifunctional acid-base catalysts, the MCS surface was modified using post-synthesis methods in which the carbon moieties were decorated with sulfonic acid groups, whereas the silica matrix surface was grafted with 3-aminopropyl groups. The resulting materials exhibited high surface area, large pore volume, and contain some oxygen-containing functional groups. Their acid-base properties were tunable by varying the content of sulfonic acid and aminopropyl groups. The HMF was synthesized by catalytic conversion of fructose and glucose in a biphasic medium. Fructose dehydration catalyzed by sulfonated MCS catalyst (MCS-SO3H) at 150 °C for 2 h yields 56% HMF at 81% conversion. For the glucose system, the Bronsted basic sites facilitated the glucose–fructose isomerization, however, it promoted the formation of undesired humins. The acid/base ratio of bifunctional MCS catalysts (MCS-SO3H-NH2) contributes to the HMF yield and selectivity. The HMF yield of 39.4% was obtained over the MCS-SO3H-NH2 catalyst with an acid/base ratio of 0.10 at 190 °C for 1 h. In both systems, the formation of levulinic acid, a byproduct of HMF hydrolysis, was suppressed due to the hydrophobicity of the MCS catalyst. These developed catalysts are promising for the synthesis of HMF from glucose, at high substrate concentration than those reported in the literature.

The aluminosilicate MCM-68 has an MSE topology, a unique pore system, and solid acid characteristics. For these reasons, it has potential applications as a highly efficient catalyst for paraffin cracking, methanol-to-olefin/dimethyl ether-to-olefin reactions, and the alkylation of aromatic compounds. In this work, the acidic properties of both the parent MCM-68 and dealuminated versions were evaluated using infrared spectroscopy in conjunction with the adsorption of CO and/or 2,4,6-trimethylpyridine (collidine). Notably, the relatively bulky collidine molecules could not enter the 12-ring pore-mouths of the MCM-68 at room temperature but were able to do so at 403 K, due to the excitation of pore-mouth breathing vibrations that allowed increased diffusion at higher temperatures. During CO adsorption study, two types of Lewis acid sites and one type of Bronsted acid sites were identified on the parent MCM-68. After dealumination by acid treatment, the Bronsted and stronger Lewis acid sites, especially those on the external surfaces of the MCM-68 particles, were preferentially removed.

Incorporation of B atoms into the AEI-type framework was successfully achieved by addition of boric acid into the starting gel. The gel compositions, the Si/Al and Si/B ratio, and the calcination conditions were extensively investigated to tune acidic properties of the AEI-type zeolite. The incorporation of B into the framework was confirmed by solid state NMR and FT-IR techniques. In-situ FT-IR spectroscopy using CO as a probe molecule was applied to the evaluation of the acidic property. As the result of in-situ FT-IR measurement, thus obtained AEI-type boroaluminosilicate zeolites showed weak acidic properties derived from framework B species compared to the aluminosilicate one. Finally, the catalytic properties of the synthesized AEI-type zeolites in the ethene conversion reaction were investigated. We found that the AEI-type boroaluminosilicate catalyst showed a long catalytic life and a high selectivity to butenes.

A new zeolite-based catalyst for direct conversion of benzene to phenol (BTP reaction) is reported. Both Fe- and Cu-exchanged Beta catalysts, Fe-Cu/Beta, were prepared by the aqueous ion-exchange m...

The impact of the organic species in the synthetic gel of ZSM-5 on the distribution of Al atoms in the MFI framework and catalytic performance was investigated; ZSM-5 zeolites were synthesized by exclusively using TPAOH, and Na cations with PET to elucidate how the distribution of Al atoms is governed by the types of organic species in the synthetic gel. The distribution of Al atoms was investigated by 27 Al MAS NMR technique and constrain index (CI). Catalytic cracking of 1-octene over the ZSM-5 catalysts was carried out to estimate “hydrogen transfer coefficient (HTC) and cracking mechanism ratio (CMR) values”. We found that HTC and CMR values are dependent on the distribution of Al atoms. The fine-control of Al distribution in the MFI structure could improve the tolerance for coke deposition in 1-octene cracking.

Titanosilicate zeolites are well-known catalysts for selective oxidation using hydrogen peroxide, an environmentally friendly oxidant. To effectively synthesize these materials with high Ti contents, we have focused on using a Ti–Si mixed oxide composite as the ingredient along with intentional addition of an aluminum source to promote crystallization. Ti-beta, a *BEA-type zeolite containing titanium at the framework sites, was chosen as a model zeolite. First, (Ti, Al)-beta, a *BEA-type zeolite containing both Ti and Al, was prepared; the occluded aluminum inside the product was subsequently removed by an acid treatment. This treatment not only lead to the reduction of the aluminum content to trace levels but also improved the states of the titanium species to the desired tetrahedral coordination state. Thus, Ti-beta zeolites with little extra-framework Ti were successfully obtained with molar compositions up to Ti/(Ti + Si) = 4.0 mol %. As a titanosilicate zeolite catalyst, high functionality was demons...

The CHA-type aluminosilicate zeolites were synthesized in the presence of the N,N,N-trimethyl-1-adamantammonium cation from different starting materials, including fumed silica, aluminum hydroxide, and the FAU-type zeolite, with their proportions varied. In this work, the proportion of “Q4(nAl)”, Si(OSi)4-n(OAl)n and “Q3(nAl)”, Si(OSi)3-n(OH)(OAl)n, in the total framework Si atoms, which can be estimated by the solid-state 29Si MAS NMR technique, has been applied to an index for Al distribution. When the proportion of the Al source derived from the FAU-type zeolite was increased, the proportion of Q4(2Al) was increased. Thus, we found a facile method for controlling the Al distribution in the CHA-type zeolite by varying the starting materials. Finally, the impacts of the Al distribution on the hydrothermal stability and catalytic properties in the methanol to olefins (MTO) reaction were investigated.

Carbon dioxide was shown to identify surface basic properties of nitrogen-substituted microporous and mesoporous silicas, in addition to conventional basic oxides, by a detailed study using isotherm and heat of adsorption measurements as well as by infrared spectroscopy. A hydrogen-bonded weak interaction was primarily observed between CO2 and silanol (Si-OH) and silamine (Si-NH-Si) groups. The heat of adsorption of CO2 demonstrated that the latter adspecies were formed preferentially over the former, although a much higher amount of linear CO2 adspecies were found on SBA-15 mesoporous silica because of the presence of a large quantity of silanol groups on its surface. Carbamate-type chemisorbed adspecies were not detected on silamino sites, whereas carbonate-type adspecies were formed on alkali ion-exchanged zeolites and also residual sodium ions on the surface of silicalite-1. CO2 was shown to be a successful probe molecule for identifying weakly interactive hydrogen-bonding sites, and it has potential as a surface probe for strongly interactive nucleophilic sites derived from alkaline ions or a methylated silamino group, Si-N(CH3)-Si.

Very fine Ni nanoparticles including subnanoclusters are dispersed in zeolite-templated carbon (ZTC), by thermal decomposition (573 K) of nickelocene pre-loaded on ZTC which functions as a high-surface area support. X-ray absorption fine structure reveals that the Ni species formed by the thermal decomposition is in a unique oxidized state. It is different from nickelocene, Ni metal, or any other inorganic Ni species. The unique Ni species can dissociatively adsorb H2, and enhance the following spillover even under ambient conditions. The spillover activity of the non-metallic Ni subnanoclusters is superior to that of Ni-metal nanoparticles and even comparable to that of Pt nanoparticles.

Co-reaction of methanol and ethylene (CME) have been performed on a number of proton type MFI zeolites and CHA zeotype materials to investigate the influence of zeolite topology and acidities upon the transformation of reactants and the formation of desired product of propylene. Two other reactions of methanol-to-olefins (MTO) and ethylene transformation (ET, with only ethylene as the reactant) were carried out in order to compare the promotion effect for the propylene productivity. The reactions were carried out at 773 K. The addition of methanol remarkably promoted the ethylene transformation over Al-poor HMFI zeolite and, more importantly, the by-products due to hydrogen-transfer reactions were efficiently inhibited, leading to higher propylene selectivity. Such promotion effect was, however, not significantly observed upon the Al-rich HMFI zeolite. Moreover, such promotion effect of methanol upon ethylene transformation was un-pronounced or non-existed upon the CHA zeotype materials including aluminosilicate, gallosilicate and silicoaluminophosphate, possibly owing to the CHA topology.

High-molecular-weight (number average molecular weight Mn = 11–81 kDa) polymers with intrinsic microporosity (PIM) were prepared by the solution polycondensation of 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane, decafluorobiphenyl, and bisphenols in an aprotic polar solvent at an initial monomer concentration of 0.1 mol/L at 100°C-140 °C for 10–144 h. Transparent (minimum cutoff wavelength of 310 nm), highly thermostable (glass transition temperature of 161°C-376 °C by dynamic mechanical analysis, and 5% weight loss temperature in N2 of 410°C-514 °C) polymer films were fabricated using a solvent-cast method. The copolymer films showed good mechanical properties (tensile strengths of 45–67 MPa, breaking elongation of 2.2%–23.1%, and tensile elastic moduli of 1.5–3.3 GPa) and insulating properties (relative permittivity of 2.27–2.59, and dissipation factor of 0.00191–0.00466 at 20 GHz frequency). The prepared new PIM copolymers are candidates for next-generation low k dielectric materials.

The novel TUN-type aluminoborosilicate zeolite (denoted as [Al, B]-TUN), which consists of a three-dimensional pore system with 10-ring, has been hydrothermally synthesized for the first time and implied in cracking reaction. The mother gel composition including aluminum, boron, organic structure-directing agent and sodium were intensively studied and optimized. We found for the first time that the incorporation of B together with Al T-sites into the TUN framework led to the control of acidic properties including the number, strength and distribution of acid sites. The n-hexane cracking over different catalysts show that the [Al, B]-TUN zeolites have a longer catalyst duration and a higher P/E ratio (propylene/ethylene selectivity) than [Al]-TUN. Moreover, the comparison between TUN, MFI and *BEA-type zeolites indicates that TUN-type zeolite has a preference for propylene production. The relationship between acidic properties and carking behaviors were discussed and supported by the constraint index (CI) value measurement.

Eight-membered ring small-pore zeolites Rho and KFI have been synthesized, characterized and tested for dehydration of methanol to dimethyl ether at low-temperature, and compared with other zeolites and three different samples of γ-Al2O3. Both the zeolites were mainly crystallized from the synthesis gels with the Si/Al ratio of 5.0 by a conventional hydrothermal method without any agitation. The amount of total solid-acid sites was 1.65 mmol g−1 and 2.53 mmol g−1 for zeolite KFI and Rho, respectively. In addition, zeolites SSZ-13, RUB-13, and ZSM-5 were also employed for the reaction. Reaction conditions were optimized for a low-temperature catalytic dehydration of methanol selectively to dimethyl ether. Methanol dehydration efficiency of various zeolitic frameworks is discussed against the strength of solid-acidity, type of channel structure, specific surface area, and particle size. At temperatures ≤ 200 °C, the overall catalytic efficiency of the small-pore zeolites with appropriate medium-strong acidity and 3-D channels was superior to that of the reference γ-Al2O3 materials.

Infrared probe (IR) methods to estimate the acid strength of OH groups on H-form zeolites were compared on mordenites (HM90, Si/Al = 45 and HM20, Si/Al = 10), ZSM-5 (Z5-90H, Si/Al = 45) and Y (HY5.6, Si/Al = 2.8). Heat of adsorption as well as the internal frequency of adsorbed CO was not sensitive enough to evaluate the acid strength of different zeolites. Thus, H/D isotope exchange reaction of acidic OD groups with a small hydrocarbon, C2H6, was employed. For the estimation of intrinsic activation energy, heat of adsorption of C2H6 was first measured. However, C2H6 molecules could not enter the 8 membered ring (MR) of HM20, and the secondary interaction of C2H6 with pore walls of Z5-90H increased the heat of adsorption, both due to the observation at low temperatures. This prohibited the comparison of heat of adsorption on a single Bronsted acid site in different spaces of zeolite with different topologies. Considering that the structural restrictions of such small molecules as C2H6 become negligible at high temperatures as a result of the vibrational excitation of pore mouth-breathing modes of zeolites, and that the topology difference of a single Bronsted acid site in heat of adsorption is relatively small, we proposed that the apparent activation energy for H/D isotope exchange reaction would reflect the acid strength of single sites. The present results are compared and discussed with conclusions led by other methods.

The distribution of Al atoms in ZSM-5 has been recognized as an important factor in catalytic activity. Here, ZSM-5 zeolites were synthesized from synthetic gels containing various alcohols, including straight- and branched-chains alcohols. The effect of the alcohols in the synthetic gel on the Al distribution in the MFI framework was investigated based on 27 Al MAS NMR, Co(II) ion UV−vis DRS, and constraint index value. Thus synthesized ZSM-5 zeolites were applied to catalysts for the cracking of n -hexane and the methanol-to-olefins (MTO) reactions in order to investigate the impact of the Al distribution on the catalytic properties. A unique Al distribution in the MFI framework was achieved by the use of trimethylolethane (TME) in combination with Na cations, and thus-prepared ZSM-5 catalyst showed a long catalytic life for both the cracking of n -hexane and the MTO reaction.

Acid sites existing on the external surface of zeolites are the main cause of the formation of coke materials, resulting in decreasing the catalytic activity. For the durability of the reaction, silylation of external acid sites was adopted. Among various silylation reagents, cyclic siloxanes were effective silylation compounds for the deactivation of the acid sites on external surface on zeolite without prohibiting the objective reaction, cracking of naphtha. The effect of silylation was confirmed not only by the reaction but also by infra-red analysis.

Temperature-dependent behavior of acidic OH groups on zeolites was observed by infrared (IR) spectroscopy. While the IR band of acidic OH groups appeared the same in frequency and intensity below 300 K, gradual shifts in the peak-top position to lower frequencies and decreases in integrated intensity were recognized when samples were heated at higher temperatures. These changes were completely reversible and only dependent on the temperature. Based on the assumption that there is an equilibrium between undissociated and dissociated states of OH groups, a model is proposed in which the intensity decrease is attributed to the dissociation of OH groups to form IR inactive species at high temperatures. The enthalpy difference between the two states was estimated using the van’t Hoff equation, leading to two different values in two temperature ranges (about 398–548 and 573–773 K) for zeolites with various topologies (MFI, MOR, and CHA). Based on the presence of two different types of enthalpy values, different...

TiO2 is a famous support for selective catalytic reduction of NO with NH3 (NH3-SCR). Engineering the morphology and structure of TiO2 is effective to modulate the interaction with surface dispersed component, providing further opportunity to improve catalytic performance. In this study, we rationally construct thin-layered titania confined in mesoporous silica via a surface grafting strategy. It exhibits high specific surface area with amorphous structure along mesopore channel, and much more Bronsted acid sites are generated than bulk TiO2 due to defect induced oxygen-related species. After iron oxide loading, both the denitration activity and H2O/SO2 tolerance are greatly promoted as compared to conventional Fe/TiO2. Further characterizations reveal the obtained catalyst displays uniform iron oxide dispersion and intense Fe-Ti interaction, resulting in superior redox behavior and increased acidity. Notably, it is found the introduction of H2O exhibits a promotional effect on NO conversion efficiency, which can be ascribed to enhancement of NH3 adsorption capability. Besides, SO2 has negligible disturbance on NO/NH3 adsorption, leading to superior sulfur tolerance. The result of present study demonstrates vital role of surface structure engineering of TiO2 for sustainable denitration, which opens up a new avenue for designing well-performed and stable NH3-SCR catalysts.

Proton conduction in alkali metal ion-exchanged porous ionic crystals A2[Cr3O(OOCH)6(etpy)3]2[α-SiW12O40]·nH2O [I-A+] (A = Li, Na, K, Cs, etpy = 4-ethylpyridine) is investigated. Single crystal and powder X-ray diffraction measurements show that I-A+ possesses analogous one-dimensional channels where alkali metal ions (A+) and water of crystallization exist. Impedance spectroscopy and water diffusion measurements of I-A+ show that proton conductivities are low (10−7–10−6 S cm−1) under low relative humidity (RH), and protons mostly migrate as H3O+ with H2O as vehicles (vehicle mechanism). The proton conductivity of I-A+ increases with the increase in RH and is largely dependent on the types of alkali metal ions. I-Li+ shows a high proton conductivity of 1.9 × 10−3 S cm−1 (323 K) and a low activation energy of 0.23 eV under RH 95%. Under high RH, alkali metal ions with high ionic potentials (e.g., Li+) form a dense and extensive hydrogen-bonding network of water molecules with mobile protons at the periphery, which leads to high proton conductivities and low activation energies via rearrangement of the hydrogen-bonding network (Grotthuss mechanism).

Cation vibrations of several alkaline metals and molecular cations in zeolite pores were observed by the in-situ far-IR with transmission method using a closed gas evacuation and circulation system. The peak-top frequency of a series of alkaline metal cation vibrations on FAU-type zeolites was proportional to the minus one half of the mass of cations, indicating that only cations are regarded as oscillators. In addition, the frequency of the same cation vibration differed depending on the zeolite topology. This implies the presence of other origins responsible for the vibrational energy than mass. The largest energy difference of Na+ cation vibration among different zeolites was found between FAU- and MOR-types to be about 6.0 × 10−3 kJ mol−1, possibly attributed to the “confinement effect”. The molecular (ammonium and pyridinium) cation vibrations were also observed by the dynamic observation of adsorption and desorption of molecules. In the case of NH4+-form FAU-type zeolite, a band at 176 cm−1 was observed at room temperature and disappeared by evacuation at 523 K due to the desorption ammonia. Then, the intensity of the band was gradually recovered by the successive ammonia adsorption at room temperature. This in-situ measurement gave an accurate assignment of the molecular cation vibration. Moreover, the cation vibration of pyridinium cation was also observed by in-situ adsorption of pyridine on H+-form (NH3-desorbed) zeolites. The effect of the zeolite topology on molecular cation vibration was also observed, which confirmed the presence of the confinement effect in zeolites.

Improving the selectivity of zeolite catalysts over a wide variety of reactions without diminution of their catalytic activity requires both shortening the diffusion path of guest molecules within the micropores and selective deactivation of the external acid sites. In this work, the former was achieved by mechanochemical bead-milling treatment of micron-sized ZSM-5 zeolite and subsequent recrystallization, and the latter by the selective removal of framework Al and silica–alumina species on the external surface of ZSM-5 nanoparticles via hydrothermal treatment with a concentrated HNO3 aqueous solution. The modified ZSM-5 nanoparticles showed higher propylene yields as well as high resistance to coke formation during hexane cracking. Significant changes in the Bronsted and Lewis acid sites on the external surface of the treated ZSM-5 were also observed using FT-IR with CO and collidine as probe molecules.

The catalytic cracking of n -hexane to selectively produce propylene on the MCM-22 catalysts dealuminated by nitric acid treatment was carried out as a model reaction of naphtha cracking. The nitric acid treatment of MCM-22 precursors under severe conditions followed by calcination at 823 K has been proven to be an effective dealumination method for MCM-22 zeolite. At a high n -hexane conversion of 90%, the dealuminated MCM-22 (D-MCM-22) catalyst with Si/Al = 34 showed a higher propylene selectivity (41 C-%) than H-ZSM-5 and H-Beta catalysts with similar acid amounts. Moreover, D-MCM-22 showed a stability comparable to H-ZSM-5 and much higher than H-Beta catalyst. This would be due to the selective removal of acid sites within supercages, suppressing coke formation and the resultant deactivation.

A free-standing membrane that consists of a newly synthesized spirobiindane-based microporous polymer carrying trimethylammonium hydroxide groups exhibited a good OH− conductivity of 65 mS cm−1 at 80 °C under 100% relative humidity, which demonstrates its potential for use in solid-state alkaline fuel cells.

The catalytic cracking of n-hexane for producing propylene on MCM-22 catalysts was carried out as a model reaction of naphtha cracking. H-MCM-22 catalysts with different Si/Al ratios were prepared by direct or post-synthesis methods. The propylene selectivity was improved with an increase in the Si/Al ratio. Dealumination of H-MCM-22 with ammonium hexaflurosilicate (AHFS) (Del-Al-MCM-22) resulted in the increase in the catalytic life and propylene selectivity at a very high n-hexane conversion. This may be attributed to the decrease in the amount of Lewis acid sites which accelerate the hydride transfer and resultant coke formation. Del-Al-MCM-22 (Si/Al = 62) catalyst showed a high propylene selectivity (40 C-%) which was higher than H-ZSM-5 and H-Beta catalysts with similar Si/Al ratios at a high n-hexane conversion of 95%. Moreover, it showed a catalytic life comparable with H-ZSM-5 and longer than H-Beta catalyst.

The effect of the preparation conditions of the Ti-MWW catalyst on the hydrophobicity of the catalyst and its catalytic activity was investigated. Our findings demonstrated that the condensation of interlayer hydroxyl groups was greatly affected by the preparation conditions, in particular washing conditions of the as-synthesized lamellar precursor of Ti-MWW, then further controlling the final hydrophobicity and oxidation properties. Using organic solvents, especially EAOH, instead of water to wash the wet lamellar precursor would synchronize the interlayer hydroxyl condensation with the decrease of interlayer distance mainly caused by the leaching of piperidine, which was used as structure-directing agent (SDA). After acid-treatment, less SDA was kept in the EAOH washed sample and 3D-MWW with less defects was formed by calcination. Both drying temperature and acid-treatment would also affect the amount of SDA occluded in the interlayer void space of the acid-treated samples and then further affect the final interlayer hydroxyl condensation upon the following calcination. The lower both drying temperature and acid-treatment temperature were favorite to unequal interlayer dehydroxylation to form MCM-56, while higher drying temperature such as 150 °C not only caused the anatase phase in the calcined samples but also occluded more SDA molecules in the acid-treated samples which greatly affect the further interlayer hydroxyl condensation upon the calcination. Ti-MWW-OH-100 containing smallest amount of silanols and less defect sites showed the best hydrophobicity and the highest catalytic activity in 1-hexene oxidation.