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Catalytic cracking of naphtha is now a process of huge development potential to produce light olefins, which are important basic raw materials used in various industries, but current industrial catalysts like ZSM-5 zeolites suffer from low selectivity and high energy consumption. Here, Ti/Al-containing nanosize MFI-structure zeolites in-situly synthesized through one-pot method were applied to the catalytic cracking using n-hexane as the model reactant. The maximum mass yield of combined light olefins reaches 49.2% with 99% conversion at 600°C and 1 atm. Multiple characterizations are used to identify the Ti-related active species and their effect on the performance. It was found that a higher proportion of LAS caused by Ti was beneficial to the activation of reactant, and the slightly increased amount of BAS leaded to more alkanes converting into light olefins. This understanding may open new opportunities for design and modification of catalytic cracking catalysts.

High pressure reforming of methane is critical for process economics, but imposes increased risk of catalyst coke deposition. Herein, a coke- and sintering-resistant Ir-Ni alloy catalyst is presented, which is durable in methane bi-reforming at 850 °C and 20 bars for up to 434 h.

Generation of surface active sites with tailor-made structure is a promising way to enhance catalytic properties of inexpensive metal oxides, as a replacement to noble metals. In the abatement of N...

Generation of hierarchical zeolites is an effective way to enhance their diffusion-dependent catalytic properties. The fabrication of hierarchical zeolites with enhanced diffusion property, high hydrothermal stability, strong acidity in an inexpensive, facile and efficient way is particularly daunting. Here, a simple synthesis of hierarchical SSZ-13 zeolite in a biphasic water/toluene media under tumbling assisted by organosilane, i.e., trimethoxy[3-(phenylamino)propyl]silane, is proposed. The obtained material with tunable Si/Al from 10 to 30 consists of assembled crystallites of 20–30 nm that construct a hierarchical architecture with mesopores of ca. 7 nm opening to the external facets, and has low defect concentration and preserved strong acidity. Crystallization mechanism is disclosed to obey a non-classic attachment growth of nano building blocks mediated by Pickering emulsion, as organosilane modification changes their surface to be hydrophobic. Such a crystallization pathway has accelerated nucleation process and suppressed the growth of SSZ-13 crystals to micron size. Cu exchanged hierarchical SSZ-13 outperforms the standard sample in typical NH3-SCR process in both low and high temperature regimes as a result of enhanced diffusion property, as well as low defect concentrations. The synthesis is a cost-effective method for the generation of hierarchical zeolites mediated by the presence of a liquid/liquid interface, and could inspire more such explorations.

Unidimensional zeolites often form rod-shaped crystals that suffer from low catalytic selectivity or catalyst lifetime owing to their poor diffusion properties. Combined postsynthetic ball-milling and recrystallization methods were investigated to produce unidimensional ZSM-23 crystals with reduced aspect ratio. The influences of ball-milling in the presence/absence of structure directing agent (SDA) and diverse recrystallization media, including H2O, Na2Si3O7 solution, synthetic mixture and mother liquor, over crystallinity, crystal size, textural properties as well as acidity, were intensively explored using characterization techniques such as XRD, SEM, N2 physisorption, 27Al MAS NMR, NH3-TPD, pyridine IR spectroscopy and diffusion measurement. The results showed that crystal size of ZSM-23 was considerably reduced after ball-milling treatment, however, at the expense of crystallinity, acidity and porosity. Recrystallization in the presence of mother liquor was identified as the most effective and economic way to restore crystallinity. The optimized ZSM-23-M-m sample derived from ball-milling in the presence of SDA and a subsequent recrystallization in separated synthesis mother liquor exhibited higher isomer yield (ca. 53%) than the parent sample (ca. 34%) in n-heptane hydroisomerization reaction owing to the enhanced diffusion property and regained acidity after recrystallization.

We present a phase-transfer crystallization approach to the synthesis of ultrasmall (

Controlling crystal size and shape of zeolitic materials is an effective way to promote their mass transport and catalytic properties. Herein, we report a single step, Na+ - and porogen- free crystallization of MFI hierarchical architecture made up of aligned nanocrystals with reduced b-axis thickness (5-23 nm) and adjustable Si/Al ratios between 35 to 120, employing the commonly used tetrapropylammonium hydroxide (TPAOH) and tetrabutylammonium hydroxide (TBAOH) as structure-directing agents (SDAs). Homogeneous nucleation driven by both SDAs and subsequent SDA-exchange induced dissolution-recrystallization are responsible for the formation of such structure. The enhanced textural and diffusion properties account for a notable exaggeration of propene selectivity and catalyst lifetime in dimethyl ether-to-olefins (DTO) conversion. This protocol is extendable to the rational synthesis of other hierarchical zeolites through crystallization process control.

The catalytic performance of silicoaluminophosphates is dependent on their acidity and diffusion properties, which can be altered by an organic structure-directing agent (OSDA) as a result of its dominant effect on crystallization. Generally, the solubility of an amine in aqueous media is an important factor for judging whether it is suitable to serve as an OSDA in hydrothermal synthesis of zeolites. This work demonstrates that a hydrophobic molecule, tri-n-heptylamine, could be used as an OSDA for synthesis of hierarchically porous SAPO-31 in biphasic toluene/water media. It provides not only a new method for synthesis of zeolites but also a simple, inexpensive, and porogen-free pathway to generate hierarchical SAPOs. The synthesis allows manipulation of the nSi/(nAl + nP + nSi) ratio from 0.02 to 0.13 without noticeable change of morphological features. The self-assembled, nanocrystalline structure was revealed by combined XRD, SEM/TEM, N2 physisorption, and 27Al, 31P and 29Si MAS NMR spectroscopy, and the acidity was measured with NH3-IR. Catalytic evaluation in n-dodecane hydroisomerization shows that the isomer yield depends on the acid site density of the catalysts, and weak acid strength and high acid site density should be avoided to achieve high selectivity. On the optimized catalyst, the isomer yield has been significantly improved up to 79.7% in contrast to 58.1% for the sample derived from usual hydrothermal synthesis with di-n-hexylamine as an OSDA.

The SUZ-4 zeolite membrane was prepared on the hollow fiber ceramic membrane via the secondary growth method modified by the dynamic hydrothermal process. The surface morphology and pervaporation (PV) performance of zeolite membranes fabricated by dynamic and static hydrothermal processes were studied. The surface of the zeolite membrane prepared by the dynamic hydrothermal process was covered with rod-shaped crystals, while the static one was full of crystal clusters fabricated by small-sized crystals. Besides, the separation factor of the SUZ-4 zeolite membrane made via dynamic hydrothermal method for separating 10 wt% methanol (MeOH)/methyl methacrylate (MMA) mixture at 50 °C exceed 10000 with a flux of 3.83 kg·m−2·h−1, which was better than the static one and showed excellent long-term stability. This work provided the important assistance for the preparation of SUZ-4 zeolite membranes in the separation of MeOH/MMA and MeOH/dimethyl carbonate (DMC) organic mixtures and demonstrated the great potential of dynamic process in promoting the membrane properties.

This paper investigates the influence of reactor structure and operating conditions on dry reforming of methane (DRM), using a two-dimensional reactor model. Two tubular reactors commonly used in the industry are included: one is a mono-tube reactor, the other contains a concentric heating tube. The reactor structure and operating conditions significantly affect temperature distribution and methane conversion in the two reactors. Catalyst dilution in catalyst beds is efficient to control temperature but also largely decreases methane conversion, indicating a balanced packing density of catalyst is required. Reducing the tube radius is useful to control temperature and can save a lot of (in some cases >90%) catalyst, which demonstrates the great potential of using tubular reactors with a small radius. The inlet temperature only slightly changes temperature distribution and methane conversion. The elevated total pressure reduces temperature gradient and also methane conversion, while the feed CH4/CO2 ratio only importantly affects the equilibrium conversion of methane. Comparing temperature distributions and methane conversions in the two reactors, the tubular reactor with a concentric heating tube performs better and uses 11–67% less catalyst. These results should serve to guide the design of tubular reactors for DRM and other highly endothermic reactions.

A single precursor RuxNiyMg1-x-y(OH)(OCH3) derived from solvothermal synthesis was used to generate Ru-Ni-MgO catalysts for methane reforming with CO2. Calcination-reduction pretreatment of precursors could easily cause segregation of Ru and formation of both large and small metallic particles as RuO2 has limited solubility in NiO-MgO solid solution. Uniform small Ru-Ni alloy particles could only be produced within their limited alloying composition range through direct reduction pretreatment of the precursor. Catalysts derived from calcination-reduction exhibited low initial activity that increased with time-on-stream, whereas catalysts derived from direct reduction demonstrated high and steady activity. Over spent catalysts, Ru was found to have changed the type of deposited carbon from a recalcitrant graphitic one that could only be gasified by O2 to a soft type that can be facilely gasified by CO2. Kinetic studies showed that Ru increased the activation barrier for the rate determining CH4 dissociation step and thereby slows down the carbon deposition rate. A first order reaction dependence for CH4 pressure variation and zeroth for CO2 pressure change for pristine Ni- and Ru-catalysts was identified, while a first order and a deviation from zeroth order for CH4 and CO2 pressure variation were observed on bimetallic Ru-Ni catalyst. Such a deviation is associated with the oxyphilic nature of Ru that is enriched in the alloy surface under reforming conditions. The effects of Ru on carbon gasification over spent catalysts were investigated using a modified CO2-TPO measurement based on an extrapolated Wigner–Polanyi equation for carbon gasification. Ru was found to accelerate carbon gasification by increasing the pre-exponential factor for CO2 oxidation of carbon, albeit a disfavored elevated activation barrier was obtained, thus showing a strong compensation effect. Carbon gasification is favored in high concentration of CO2 and at high temperatures for Ru-Ni catalyst.

Changing size and shape of zeolitic crystals brings about enhanced diffusion properties and related promotion of catalytic performances. This work puts forward a phase-transfer synthetic strategy to generate ATO nanocrystalline silicoaluminophosphates spheroids under tumbling crystallization using aluminum isopropoxide dissolved in toluene and other ingredients (fumed silica/phosphoric acid/Di-n-hexylamine) dissolved in water as precursors. Toluene and aqueous phase formed a Pickering emulsion like structure during hydrothermal crystallization. Highly uniform crystalline spheroids of weighted 55 nm with strong acidity and high surface area were obtained, which exhibited a high isomer yield up to 79% in n-heptane hydroisomerization. Comparisons of product distribution and kinetic studies suggest that monomethylbranched isomer selectivity is controlled by product shape selectivity, whereas dimethylbranched isomer selectivity is affected by combined transition state and product shape selectivity. The increase in selectivity for ATO spheroids is attributed to an expansion of intrinsic reaction controlled temperature regime and an improved diffusion property.

Nanosized SAPO-34 has been successfully synthesized by a facile and low-cost method involving an azeotrope evaporation and steam-assisted crystallization route without either expensive poregens or homemade starting materials. The as-synthesized nanosized SAPO-34 shows ultrasmall grain sizes and an impressively high total pore volume, as confirmed by X-ray diffraction, nitrogen physisorption, scanning electron microscopy, and transmission electron microscopy techniques. The formation process and the pivotal role of supersaturation in the synthesis of nanosized SAPO-34 have been revealed by a series of control experiments, on the basis of which a nonclassic oriented attachment mechanism under high supersaturation ratio conditions is proposed. When used as the catalyst for the conversion of chloromethane to olefins, the nanosized SAPO-34 exhibits acidity comparable to that of the conventional SAPO-34 but double the catalytic lifetime and a slightly lower selectivity for light olefins.

Transforming natural kaolin into pure-phase hierarchical aggregates of nano ZSM-11 has been achieved by using a novel tetrabutylphosphonium hydroxide as a structure-directing agent via steam-assisted crystallization. The hierarchical ZSM-11 possesses a small particle size (about 240 nm), large surface area (428 m2 g−1), and abundant mesopores (0.30 cm3 g−1). Moreover, the hierarchical ZSM-11 exhibits prolonged catalytic lifetime and promoted aromatic selectivity in the methanol-to-aromatics reaction. The superior catalyst stability is attributed to the better capacity of accommodating the coke and a lowered coking rate.

1,3-Propanediol, a vital monomer for the manufacture of commodity polytrimethylene-terephthalate, is commercially produced nowadays through either hydration of acrolein or hydroformylation of ethylene oxide. Herein, for the first time, we present the investigation of an alternative route for 1,3-propanediol production from vapor-phase catalytic hydrogenation of syngas-derived dimethyl malonate on a Cu/SiO2 catalyst. The catalytic reaction network has been disclosed for the Cu/SiO2 catalyst, and the reaction proceeds through sequential hydrogenation with methyl 3-hydroxypropionate as the primary product, which can be further converted into 1,3-propanediol or methyl propionate. Excessive hydrogenation of 1,3-propanediol or methyl propionate leads to the formation of n-propanol. Meanwhile, a small amount of dimethyl malonate cracks into methyl acetate. The structural and textural properties of Cu/SiO2 catalysts with varied copper loadings were extensively characterized by X-ray diffraction, Fourier transform infrared spectroscopy, H2-temperature programmed reduction, X-ray photoelectron spectroscopy, N2 physisorption, CO chemisorption, N2O titration, and transmission electron microscopy. A correlation of the areal activity to copper components suggests that metallic copper modified by the co-present Cu+ species may be the active site for the hydrogenation. The highest 1,3-propanediol selectivity was achieved on a catalyst with a maximum Cu+/(Cu0 + Cu+) ratio of 0.41. The revelation of catalytic networks and insights into the active species can provide guidance for future rational design of catalysts for regioselective hydrogenation of CO bonds in dimethyl malonate.

Surface modification is an efficient post-treatment method to optimize the properties of nanofiltration (NF) membranes. Here, we report a facile surface modification strategy coupling with heat curing for grafting monoethanolamine (MEA), a monomer containing both a primary amine and a primary alcohol group, onto a nascent polyamide NF membrane. With grafting 0.5 wt% MEA at 50 °C, the pure water permeability of the polyamide NF membranes was improved from 7.9 to 19.5 L m−2 h−1 bar−1 due to their enhanced physicochemical property, such as superior hydrophilicity, rough surface morphology, and enlarged membrane pores. Meanwhile, the rejection of Na2SO4 remained above 97.5%. More importantly, the optimal membrane modified with 0.5 wt% MEA exhibited a high Na2SO4 rejection of 99.1% and a negative NaCl rejection of −20.1% when treating a mixed salt solution containing 2 g/L Na2SO4 and 2 g/L NaCl. Our study provides a novel insight for the fabrication of high permselectivity NF membranes via surface modification.

Understanding silicoaluminophosphate formation mechanism lays the foundation for their structure manipulation via crystallization process control. Crystallization of SAPO-34 from a dry gel using tetraethyl ammonium hydroxide as structure-directing agent was monitored to unravel the formation mechanism. The initial gel was found to form a lamellar precursor first, which subsequently underwent phase transformation to discrete SAPO-34 nanocrystallites. The nanocrystallites thereafter mutually aligned with neighboring ones via a non-classic oriented attachment growth mechanism, affording large crystals as a result of grain boundary elimination. A new protocol to prepare hierarchical SAPO-34 was designed by hindering the aggregation of primary nanocrystallites with a growth inhibitor 1,2,3-hexanetriol. The structure of hierarchical SAPO-34 was characterized by XRD, N 2 physisorption, mercury intrusion, SEM, TEM, as well as 27 Al, 29 Si, 31 P MAS NMR spectra and compared with a conventional SAPO-34. More Si islands were formed via combined SM3 (Al+P pairs substitution by 2Si) and SM2 (P substitution by Si) mechanism for hierarchical SAPO-34 as Si was not fully incorporated into the precursor lamellar phase. NH 3 -TPD showed that hierarchical SAPO-34 has comparable acidic strength to conventional SAPO-34. The obtained hierarchical SAPO-34 is comprised of

Methane is an important product in methanol to hydrocarbon (MTH) process and its formation mechanism over HZSM-5 was investigated by applying periodic density functional theory. The results show that the carbocations of C 7 H 9 + –C 12 H 19 + are important intermediates in MTH process and methane is formed via one intramolecular hydrogen transfer reaction of these intermediates from ring carbon to the carbon of methyl group. The activation energies for methane formation increase from 101 to 174 kJ/mol with increasing methyl groups in protonated methylbenzenes. The data indicate that methane has similar formation mechanism as ethene and propene, i.e. via hydrocarbon pool mechanism.

Integrating hierarchical porosity over microporous zeotype materials is an effective way to promote their mass transfer properties and catalytic performances. A combined synthetic strategy using small molecular growth inhibitor 1,2,3-hexanetriol and tumbling crystallization condition to generate hierarchically organized SAPO-11 is herein presented. The addition of 1,2,3-hexanetriol in the synthetic gel of SAPO-11 under agitating conditions significantly altered its crystallization behaviour, resulting in the formation of a hierarchically organized architecture. An underlying nonclassical from-shell-to-core crystallization has been disclosed by time-dependent observation of the formation process. The hierarchically self-organized structure has been characterized by a suite of characterization techniques, such as XRD, N2 physisorption, SEM, TEM, mercury intrusion measurements, 27Al, 29Si, 31P MAS NMR and pyridine adsorption IR (Py-IR). The structure featuring barrel-shaped architecture is comprised of aligned 300–400 nm primary building blocks with voids in between, constructing an auxiliary macro-/meso-pore system open to external surfaces. The catalytic performance of Pt supported on hierarchical SAPO-11 in n-heptane hydroisomerization has been assessed, showing that both catalytic activity and isomer yield have been increased with respect to a conventional sample. As the acidity for the hierarchical SAPO-11 is comparable to the conventional sample, the enhancement in catalytic performance is attributed to the small primary crystal size and macro-/meso-pore-connectivity, that are important for mass transfer.

Silicoaluminophosphates SAPO-41 is a superior unidimensional zeotype catalyst used in hydroisomerization. Generation of hierarchically structured SAPO-41 provides an effective way to promote its hydroisomerization selectivity, which is nonetheless difficult to achieve due to the formation of impurities. Herein, we report crystallization of plate-like crystals of pure phase SAPO-41 in a toluene-aqueous biphasic media in the presence of both Pr2NH and oleylamine. The obtained material has a larger adjustable range of silicon content (nSi/(nAl+nSi+nP) = 0.02−0.15), intermediate acidity and reduced diffusion path length along the micropore channel direction. Catalytic tests for n-heptane hydroisomerization on Pt loaded plate-like SAPO-41 crystals showed that the yield of the isomerized products could reach up to 68 %, with respect to 57 % for a control sample. The selectivities for isomers were found to increase with decreasing Si contents and enhanced diffusion properties, suggesting side β-scission reaction was disfavored at reduced acid site density and shortened diffusion path length.

The effects of alkaline treatment on the physical properties of ZSM-5 catalysts and on their activities for methanol to aromatics conversion have been investigated. A mild alkaline treatment (0.2 and 0.3 mol/L NaOH) created mesopores in the parent zeolite with no obvious effect on acidity. The presence of mesopores gives the catalyst a longer lifetime and higher selectivity for aromatics. Treatment with 0.4 mol/L NaOH decreased the number of Bronsted acid sites due to dealumination and desilication, which resulted in a lower deactivation rate. In addition, more mesopores were produced than with the mild alkaline treatment. As a result, the lifetime of the sample treated with 0.4 mol/L NaOH was almost five times that of the parent ZSM-5. Treatment with a higher alkaline concentration (0.5 mol/L) greatly reduced the number of Bronsted acid sites and the number of micropores resulting in incomplete methanol conversion. When the alkaline-treated catalysts were washed with acid, some of the porosity was restored and a slight increase in selectivity for aromatics was obtained.

Finding controllable, low-cost, and scalable ways to generate Ni-based catalysts is the bottleneck for methane dry reforming catalyst design. A new method for generating trimetallic Co x Ni y Mg 100 − x − y O solid solution platelets enclosed by (1 1 1) facets has been developed from the topotactic pyrolysis of the metastable precursor Co x Ni y Mg 100 − x − y (OH)(OCH 3 ) derived from solvothermal synthesis. The catalyst composition and reaction conditions have been modulated to achieve maximum coke resistance and catalyst stability. Long-term stability for 1000 h time on stream at 800 °C has been achieved for the optimized Co 0.075 Ni 7.425 Mg 92.5 O catalyst. The role of Co in the catalyst has been disclosed through kinetic measurements and detailed characterization of the spent catalysts. Co is enriched on the Co–Ni alloy surface under reforming conditions and accelerates the gasification of coke intermediates. Co also enhances the chemisorption of oxygen and reduces the activation energy for methane fragmentation, which is the rate-determining step for the overall reaction.

The catalytic performance of Ag promoted Ni/CeO2 catalyst has been investigated in methane and carbon dioxide dry reforming reaction. The temperature-dependent catalytic activity and time-on-stream catalytic performance at 760 °C under different feeding conditions have been explored. Pristine Ni/CeO2 is not stable as a result of coke deposition and surface reconstruction. In addition, co-feeding of H2 can adversely influence the long-term stability of Ni/CeO2. Ag severely reduces the intrinsic catalytic activity of Ni/CeO2 catalyst, while enhances the long-term stability by diminishing coke deposition. Ag is applicable as a promoter under various reaction conditions, from N2 diluted feedstock to H2 co-fed and carrier-gas free feedstock. Kinetic studies show that Ag elevates the activation energy from 91 to ca. 140 kJ/mol by a loading of 0.3 mol.%, excessive Ag loading does not affect activation energy. The role of Ag is to block step sites on Ni surface that is associated with carbon nucleation and growth, and to promote gasification of coke formed. Besides, Ag alters the type of coke formed over Ni surface from recalcitrant whisker/encapsulating carbon to easily gasifiable amorphous carbonaceous species.

Oxygen evolution from water poses a significant challenge in solar fuel production because it requires an efficient catalyst to bridge the one-electron photon capture process with the four-electron oxygen evolution reaction (OER). Here, a new strategy was developed to synthesize nonsupported ultrasmall cobalt oxide nanocubanes through an in situ phase transformation mechanism using a layered Co(OH)(OCH3) precursor. Under sonication, the precursor was exfoliated and transformed into cobalt oxide nanocubanes in the presence of NaHCO3-Na2SiF6 buffer solution. The resulting cobalt catalyst with an average particle size less than 2 nm exhibited a turnover frequency of 0.023 per second per cobalt in photocatalytic water oxidation. X-ray absorption results suggested a unique nanocubane structure, where 13 cobalt atoms fully coordinated with oxygen in an octahedral arrangement to form 8 Co4O4 cubanes, which may be responsible for the exceptionally high OER activity.

A dry gel derived from a conventional hydrogel (or an ultrasonically treated hydrogel) containing a low amount of tetraethylammonium hydroxide (TEAOH) was subjected to a vapor-phase transport procedure using morpholine and produced SAPO-34 around 300–500 nm (or below 100 nm). The formation of small crystals has mainly benefited from the increase in tetra-coordinated Al atoms in the dry gel promoted by heating and/or ultrasonic treatment.

Glycerol-mediated crystallization transforms a steam-treated dry gel used as the mesoporous precursor into a hierarchical ZSM-5 zeolite. The hierarchical ZSM-5 zeolite with auxiliary mesoporosity and acidity exhibits higher activity in the aldol condensation reaction of benzaldehyde with n-butyl alcohol.

Methylation of benzene is an alternative low-cost route to produce xylenes, but selectivity to xylene remains low over conventional zeolitic catalysts. In this work, a combined dry-gel-conversion and steam-assisted-crystallization method is used to synthesize hierarchically porous zeolite ZSM-5 with varied Si/Al malar ratios. X-ray diffraction (XRD), N2 physisorption, NH3-temperature programmed desorption (TPD), scanning electronic microscopic (SEM) measurement and Fourier transform infrared (FT-IR) are employed to characterize the structure and acidity of both hierarchically porous zeolites and their conventional counterparts. The method is found to be applicable to ZSM-5 with molar ratios of Si/Al from 20 to 180. The ZSM-5 zeolites are used as catalysts for benzene methylation at 460 °C to investigate the effect of additional porosity and Si/Al ratios. At low Si/Al ratios, the benzene conversions over conventional and hierarchical ZSM-5 are close, and selectivity to toluene is high over hierarchical ZSM-5. It is found that hierarchical porosity markedly enhances the utility of zeolite and the selectivity towards xylenes via improved mass transport at higher Si/Al ratios. Under an optimized hierarchical ZSM-5 catalyst, xylene selectivity reaches 34.9% at a Si/Al ratio of 180.

A bottom-up approach is developed to synthesize Sn, Ce, Mn, or Co promoted NixMg1−xO catalysts enclosed by Tasker III type polar (1 1 1) facets. Sn and Co are evenly distributed on NixMg1−xO, whereas Ce and Mn segregate as separate oxides. X-ray diffraction (XRD), N2 physisorption, X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopic (TEM) measurements are carried out to understand the structure/composition of both fresh and spent catalysts. H2-Temperature Programmed Hydrogenation (TPH), XPS and Thermogravimetric analysis (TG) are employed to elucidate the types of coke formed on the spent catalysts. Mn does not show obvious enhancement to catalytic stability towards Cβ formation, and a lower activity is observed as it separates from catalyst surface and causes agglomeration of NixMg1−xO(1 1 1) platelets. Cβ and whisker carbons are found for Ce-promoted NixMg1−xO(1 1 1) catalyst, for Ce segregates as CeO2. Both Sn and Co are distinguished to enhance the coke-resistant properties of NixMg1−xO catalyst in CH4-CO2 dry reforming, as they inhibit the formation of Cβ. Activation energy (Ea) measurements show that Sn lowers the activity of Ni surfaces, while Co does not passivate the intrinsic activity of Ni surfaces. Under more critical reaction conditions with CH4/CO2 ratio of 3 and diluent gas free, Co is found to enhance the lifespan of NixMg1−xO (1 1 1) catalyst.

Synthesis of hierarchically porous zeolites has drawn intensive interest because of their improved catalytic performance. It is highly desirable to find ways to generate these materials in a low-cost and scalable way for their commercial applications. A solvent evaporation route has been established to synthesize hierarchically porous titanosilicalite-1 (TS-1). In the protocol, hexadecyltrimethoxysilane was added to an ethanolic solution of titanium isopropoxide, tetraethyl orthosilicate and tetrapropylammonium hydroxide, i.e. the embryo solution of TS-1. The solution was subjected to solvent evaporation-induced self-assembly to afford an ordered dry gel. Subsequent steam-assisted crystallization converted the dry gel into a hierarchically porous TS-1. X-ray powder diffraction (XRD), UV–visible diffusive reflectance spectroscopy, N2 physisorption and electron microscopic characterizations have been employed to elucidate the structure. Ti is incorporated into the tetrahedral sites of the MFI structure and mesopores around 20 nm penetrating the crystalline framework are formed. Hexadecyltrimethoxysilane plays a key role in creating mesopores as well as increasing the crystal size. The hierarchically porous TS-1 exhibits improved activity in styrene oxidation and phenol hydroxylation. Copyright © 2014 John Wiley & Sons, Ltd.

The epichlorohydrin-N,N-dimethyl-1,3-diaminopropane copolymer (PCA) has been introduced for the first time as a meso-template to successfully synthesize a hierarchical ZSM-5 zeolite (PCA-ZSM-5) with mesopores of 7–50 nm in diameter by using small-sized nanoblocks. However, when its structural analogue epichlorohydrin–dimethylamine polyamine (PCS) is used, the obtained ZSM-5 zeolite (PCS-ZSM-5) has lower mesoporosity than ZSM-5 nanocrystallite aggregates (NCA-ZSM-5) synthesized without the meso-template. The templating effect of the two employed cationic polymers (PCS and PCA) on the synthesis of hierarchical ZSM-5 is valuable and interesting to be evaluated, because they are easily available and have common structural characteristics that their macromolecular structure will be largely endangered by the decomposition of quaternary ammonium groups in the long polymer chain. PCA entrapped in the zeolite partially retains its cationic charges and macromolecular structure under hydrothermal conditions and thus has a significant templating effect on the synthesis of hierarchical ZSM-5, which is benefited from the cationic centers widely separated by more than 3 carbons in PCA. However, PCS decomposes severely into small amine molecules, due to the short separation of cationic centers. Further investigation into the templating effect of PCA shows that the small-sized and negatively charged nanoblocks can easily wrap and assemble with PCA and transform into hierarchical ZSM-5 templated by PCA. However, when using large-sized zeolite seeds to synthesize ZSM-5, PCA shows a negligible templating effect because PCA with limited charge density and low accessibility of cationic charges has insufficient interactions with zeolite seeds. The catalytic activities of PCA-ZSM-5 and NCA-ZSM-5 for acetalization of cyclohexanone with methanol are inferior to that of PCS-ZSM-5 with the highest number of acid sites, but the catalytic activities for aldol condensation of benzaldehyde with n-butyl alcohol follow the order of PCA-ZSM-5 > NCA-ZSM-5 > PCS-ZSM-5, consistent with the order of mesoporosity.

A facile solvothermal route is established to generate Ni x Mg 1 − x (OH)(OCH 3 ) platelet covered by (001) facets. Thermolytic decomposition of Ni x Mg 1 − x (OH)(OCH 3 ) is topotactic and leads to the formation of Ni x Mg 1 − x O solid solution enclosed by reactive Tasker III type (111) facets. Both Mg and Ni are found to be distributed evenly in the solid solution. The reduced Ni x Mg 1 − x O platelet is a stable catalyst in CH 4 -CO 2 dry reforming for a 100 h test.

Mesoporous silica with covalently bound salicylic acid molecules incorporated in the structure was synthesized with a one-pot, co-condensation reaction at room temperature. The as-synthesized material has a large surface area, uniform particle size, and an ordered pore structure as determined by characterization with transmission electron microscopy, thermal gravimetric analysis, and infrared spectra, etc. Using the strong fluorescence and metal coordination capability of salicylic acid, functionalized mesoporous silica (FMS) was developed to track and extract radionuclide contaminants, such as uranyl [U(VI)] ions encountered in subsurface environments. Adsorption measurements showed a strong affinity of the FMS toward U(VI) with a Kd value of 105 mL/g, which is four orders of magnitude higher than the adsorption of U(VI) onto most of the sediments in natural environments. The new materials have a potential for synergistic environmental monitoring and remediation of the radionuclide U(VI) from contaminate...

Metastable magnesium hydroxymethoxide [Mg(OH)(OCH3)] powder with nanosheet morphology was derived from a direct bottom-up synthesis using magnesium acetate tetrahydrate as precursor under solvothermal conditions, with benzyl alcohol as structure-directing agent. The synthesis is driven by esterification of magnesium acetate to the corresponding methyl acetate, namely, ligand exchange and esterification of CH3COO– with CH3O–. A MgO powder featuring a Tasker III type (111) surface as its main exposed surface was produced after decomposition of the as-prepared Mg(OH)(OCH3) intermediate. X-ray diffraction (XRD) shows that the as-formed intermediate is Mg(OH)(OCH3), and methyl acetate is identified in the mother liquor by GC–MS measurements. XRD, SEM, and TEM images also show that the surface of the MgO nanosheets is covered by a Tasker III (111) surface. The vanadia supported on this MgO (111) nanosheet surface is more active than the conventional MgO-supported system for the oxidative dehydrogenation of ethylbenzene with carbon dioxide, which is attributed to the oxygen-rich nature and intermediate basicity of the MgO (111) surface.

One-dimensional V2O5 nanowires have been synthesized inside the channels of mesoporous silica SBA-15 through chemical approach, which involves aminosilylation of silanol groups on the silica surface, anchoring of isopoly acid, H6V10O28. by neutralization of basic amine groups, and thermal decomposition. The formation and physicochemical properties of the nanowires were monitored and studied by TG-DTA, variable temperature in situ XRD, TEM, N2 sorption measurements and UV-Vis DRS. The results indicate that V2O5 nanowires formed within SBA-15 channels belong to orthorhombic polycrystal domains. The oxygen-to-metal charge transfer band of V2O5 nanowires shows a blue shift in comparison with bulk V2O5, which clearly exhibits the quantum size effect of nanowires.

MgO(111) nanosheets can be prepared via a facile wet chemical process. The MgO(111) nanosheets possessing the exposed (111) plane as a main surface have a thickness typically between 3 and 5 nm. Study of MgO(111) nanosheets by in situ diffuse reflectance Fourier transform (DRIFT) spectroscopy suggests that hydroxyl groups, oxygen vacancies, and surface oxygen anions exist on the surface and the (111) surface may be stabilized by hydroxyl groups. DRIFTS and temperature-programmed desorption (TPD) studies of CO2 adsorption reveal that there are large amounts of medium basic sites which can be attributed to the high concentration of surface O2- Lewis basic sites. DRIFTS and temperature-programmed reaction studies (TPRS) of methanol have demonstrated that, in contrast to commercial MgO, MgO(111) nanosheets are highly reactive toward the decomposition of methanol. Methanol can be decomposed and the surface C = O species formed can be oxidized readily at low temperature by the high concentration of oxygen anions on the surface of MgO(111) nanosheets, which demonstrates that these nanosheets have potential application in fuel cells and methanol-based alternative energy technologies.

Gold nano-particles confined in the walls of mesoporous silica (GMS) catalysts were successfully prepared by a novel and simple technique utilizing thioether functional groups in the walls of mesoporous silica to anchor HAuCl4. Calcination of the materials removed organic moieties and reduced thegold salt to gold nano-particles. In this procedure, the thioethergroups were introduced into the silicawall via a co-condensation of tetraethyl orthosilicate (TEOS) with 1,4-bis(triethoxysily)propane tetrasulfide. These gold containing mesoporous catalysts have unusually high surface area and porevolume. The catalysts were evaluated for the solventfree liquid phase oxidation of benzyl alcohol bymolecular oxygen. High selectivity to benzaldehyde was obtained under the reaction conditions of 403 K, 15 atm and 5 h in an autoclave. The 1.5% GMS catalyst was also evaluated for oxidation of alcohols using toluene as solvent under flowing oxygen at atmospheric pressure at 353 K in a two-necked flask. Under these conditions the conversion of benzyl alcohol reached 100% after 2 h and it was demonstrated that the catalyst can be recycled three times without significant loss of activity. # 2007 Elsevier B.V. All rights reserved.

We report the synthesis and characterization of a series of new mesoporous zeolite and zeotype materials made available by combining new and improved procedures for directly introducing carbon into reaction mixtures with the fluoride route for conventional zeolite synthesis. The mesoporous materials were all prepared by hydrothermal crystallization of gels adsorbed on carbon matrices which were subsequently removed by combustion. The procedures presented here resulted in mesoporous zeolite and zeotypes materials with MFI, MEL, BEA, AFI and CHA framework structures. All samples were characterized by XRPD, SEM, TEM and N2 physisorption measurements. For the zeolite materials it was found that mesoporous MFI and MEL structured single crystals could indeed be crystallized from fluoride media using an improved carbon-templating approach. More importantly, it was found that mesoporous BEA-type single crystals could be crystallized from fluoride media by a newly developed procedure presented here. Thus, we here present the only known route to mesoporous BEA-type single crystals, since crystallization of this framework structure from basic media is known to give only nanosized crystals as opposed to mesoporous single crystals. For the zeotype materials it was found that highly crystalline mesoporous materials of AFI and CHA structure types could be synthesized using a newly developed procedure.

Tungsten-substituted mesoporous SBA-15 materials have been synthesized by using a direct co-condensation sol–gel method. These resultant materials have been characterized by X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), 29Si MAS NMR and UV–Visible spectroscopy. Results of these analysis indicated that these materials had high surface area, uniform hexagonal channels and thick framework walls which were similar to that of SBA-15 and the tungsten species were highly dispersed in the silica-based framework structure. The tungsten-substituted mesoporous SBA-15 materials were used as catalysts for 1-butene metathesis for the first time, and they showed excellent catalytic performance. Such outstanding catalytic performance should be attributed to the proper content of tungsten species and its high dispersion.

Imidazole type ionic liquid 1-hexadecyl-3-methylimidazolium chloride and 1-hexadecyl-3-methylimidazolium ruthenium hexachloride were used to fabricate the well-ordered hexagonal mesoporous silica (under acidic and basic conditions), and Ru–SiO 2 , respectively. Small angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N 2 adsorption–desorption were employed to characterize the structure. The mesoporosity of the silica matrix is preserved after calcination of organic templates. The pore diameter of silica prepared from acidic media (2.20 nm) was smaller and less ordered than that of silica from basic solution (2.74 nm). Further, the mesoporous structure of Ru–SiO 2 was found to be preserved after calcination, however, RuO 2 nanoparticles formed in the matrix of mesoporous silica upon calcination.

Thermally stable mesoporous tetragonal zirconia with high surface area (153 m2/g at 700 °C) has been prepared by using bifunctional ethylene diamine as both precipitating agent for ZrOCl2 to ZrO(OH)2 and colloidal protecting agent for the ZrO(OH)2 nanoparticles. The zirconia sample was found to possess the tetragonal crystal phase exclusively. This approach avoids traditional bases such as NH3, NaOH and expensive surfactants and copolymers, which are usually employed as templates for the synthesis of high surface area and thermally stable metal oxides. Pt nanoclusters of size ∼20–30 A have been prepared in a single step chemical reduction method in aqueous media. The Pt nanoclusters have been deposited on mesoporous (pore size ≈ 35–45 A) hydrous zirconia by adopting the ‘precursor’ route. The Pt nanoclusters have been found almost evenly dispersed in the hydrous zirconia matrix without aggregation. The ethylene diamine likely serves as a link between the support (ZrO(OH)2) and Pt nanoclusters. The Pt/ZrO2 catalyst has been found to be highly active for 1-hexene hydrogenation reactions with a turnover frequency of about 20,000 h−1. All systems have been characterized by TEM, EDX, SEM, X-ray diffraction, N2 adsorption–desorption isotherms and TGA.

A series of highly efficient hybrid gold nanoparticle/mesoporous-silica catalysts were synthesized and employed for the solvent-free aerobic oxidation of cyclohexane to cyclohexanol and cyclohexanone under moderate reaction conditions. The catalysts were characterized by XRD, N2 adsorption/desorption, TEM and ICP-AES, which shows the active species are monodispersed gold nanoparticles.

N-o-Methylphenylferrocenesulfonamide was synthesized from the reaction of ferrocenesulfonyl chloride with o-toluidine. The structure was determined by single-crystal diffraction. Crystal data: monoclinic, P21/c, with unit cell dimensions of a=10.436(2), b=12.377(3), c=12.6431(3) A, and β=107.42(1)°, V=1558.1(6) A3, Z=4. The most stable structure of the complex in theory was obtained by the Hartree–Fock SCF of gaussian 98W, and the two results have been compared.

We report the design and synthesis of nanosized Zn(x)Zr(y)O(z) mixed oxides for direct and high-yield conversion of bio-ethanol to isobutene (~83%). ZnO is addded to ZrO(2) to selectively passivate zirconia's strong Lewis acidic sites and weaken Brönsted acidic sites, while simultaneously introducing basicity. As a result, the undesired reactions of bio-ethanol dehydration and acetone polymerization/coking are suppressed. Instead, a surface basic site-catalyzed ethanol dehydrogenation to acetaldehyde, acetaldehyde to acetone conversion via a complex pathway including aldol-condensation/dehydrogenation, and a Brönsted acidic site-catalyzed acetone-to-isobutene reaction pathway dominates on the nanosized Zn(x)Zr(y)O(z) mixed oxide catalyst, leading to a highly selective process for direct conversion of bio-ethanol to isobutene.

Dispersion and quantitative characterization of supported catalysts is a grand challenge in catalytic science. In this paper, heteropoly acid H3PW12O40 (HPA) is dispersed on mesoporous zeolite silicalite-1 derived from hydrothermal synthesis using carbon black nanoparticle templates, and the catalytic activity is studied for 1-butene isomerization. The HPAs supported on conventional zeolite and on mesoporous zeolite exhibit very different activities and thus provide good model systems to investigate the structure dependence of the catalytic properties. The HPA on mesoporous silicalite-1 shows enhanced catalytic activity for 1-butene isomerization, while HPA on conventional silicalite-1 exhibits low activity. To elucidate the structural difference, supported HPA catalysts are characterized using a variety of techniques, including 31P magic angle spinning nuclear magnetic resonance, and are shown to contain a range of species on both mesoporous and conventional zeolites. However, contrary to studies reported in the literature, conventional NMR techniques and chemical shifts alone do not provide sufficient information to distinguish the dispersed and aggregated surface species. The dispersed phase and the nondispersed phase can only be unambiguously and quantitatively characterized using spin-lattice relaxation NMR techniques. The HPA supported on mesoporous zeolite contains a fast relaxation component related to the dispersed catalyst, giving a much higher activity,more » while the HPA supported on conventional zeolite has essentially only the slow relaxation component with very low activity. The results obtained from this work demonstrate that the combination of spinning sideband fitting and spin-lattice relaxation techniques can provide detailed structural information on not only the Keggin structure for HPA but also the degree of dispersion on the support.« less

A hierarchical ZSM-5 zeolite with uniform mesopores has been synthesized by self-assembly of zeolite seeds capped with carboxyl-ended organosilane. The carboxylate anion enhances the inorganic–surfactant interaction and enables the formation of mesopores.

α-Fe2O3 nanowires were prepared using mesoporous silica SBA-15 as a template and showed a remarkable catalytic activity for the hydroxylation of phenol with 30% H2O2 in aqueous solution at 343 K.