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Metal leaching is an important obstacle for the development of CO-containing heterogeneous catalysis systems. The modulation of the metal surface could substantially influence the structural stability under a CO atmosphere. In this work, the inductively coupled plasma (ICP) results indicate that the leaching amount of cobalt in the CoGa intermetallic compound (CoGa IMC/SiO2) catalyst is notably less than that of the Co/SiO2 catalyst in hydroformylation reaction. The in situ Fourier Transform Infrared Spectroscopy (FTIR) results prove that aldehydes can be generated on CoGa IMC/SiO 2 by heterogeneous hydroformylation reaction without the formation of Co carbonyl species. Moreover, the analysis of metal bond interaction proves that although the Co-Ga bond has a weaker metal interaction strength in the bulk phase, it has higher structural stability than the Co-Co bond with the adsorption of CO molecules. Above all, this work provides a strategy to suppress metal leaching for heterogeneous catalysis.

CeO2 nanoshapes, cubes with dominant (1 0 0) facets and octahedra with dominant (1 1 1) facets, were synthesized to investigate the influence of surface structure on acid-base properties. An optimization of calcination temperatures, coupled with Raman and TEM, was employed to minimize the intrinsic (Frenkel-type) defect sites and their potential complications on the facet studies involved in this work. The acid-base properties of these CeO2 nanoshapes were characterized with in situ pyridine and CO2 adsorption using infrared spectroscopy and quantified using pyridine, ammonia, and CO2 temperature-programmed desorption (TPD). The (1 0 0) facet displayed weaker acid sites with lower site density than the (1 1 1) facet which had a similar density of base sites but those on the (1 0 0) facet were stronger. A strong correlation was observed between 2-propanol conversion and each facet’s acid-base properties. CeO2 cubes exhibited greater base-site catalyzed dehydrogenation to acetone while the more acidic CeO2 octahedra were more active in dehydration to propene.

N2O decomposition is investigated on Cu, Co and Fe-exchanged SSZ-13 zeolite catalysts at relatively low metal loadings. The catalysts are synthesized by solution ion exchange, and subjected to X-ray diffraction (XRD), temperature-programed-reduction by H2 (H2-TPR), temperature-programed-reaction of N2O (N2O-TPR) coupled with in-situ transmission FTIR, and finally steady-state flow reaction tests. At low N2O pressures (

For the catalytic reductive amination of carbonyl compounds, the kind of active metal used is the most important factor determining the catalytic selectivity in heterogeneous catalysis systems. However, a detailed understanding of the intrinsic mechanism is still lacking. In this work, by evaluating the reductive amination of butyraldehyde and the hydrogenation reaction of secondary imine on various metal catalysts, the competitive hydrogenation reactions of primary imine and secondary imine are proven to be the key factors determining primary amine selectivity. DFT calculations verify that Co, Ni, and Ru, rather than Fe, Rh, Pd, and Pt, tend to show high primary amine selectivity in terms of adsorption energy and activation energy. It should be noted that the different stable adsorption modes of secondary imine on metal surfaces (C&N adsorption mode on Fe, Co, Ni, Ru, and Rh, and N adsorption mode on Pd and Pt) are key factors affecting these reaction characteristics. Moreover, microkinetic simulation proves that the coadsorption of NH3 improves primary amine selectivity on Co, Ni, and Ru surfaces. Combining the theoretical and experimental results, it is clearly verified that the active metal determines the catalytic selectivity of the primary amine by affecting the competitive hydrogenation reactions of the primary imine and secondary imine.

θ-Fe3C formation is usually considered as a deactivation factor in Fischer-Tropsch synthesis (FTS). Herein, θ-Fe3C dominated Fe@C core–shell catalysts were fabricated by pyrolysis of MIL-101(Fe) in ethyne for studying the roles of θ-Fe3C and carbon shell in FTS. In the evolution of MIL-101(Fe) into Fe@C catalysts, ethyne decomposition promotes the formation of θ-Fe3C and carbon shells around nanoparticles. By modulating the pyrolysis temperature, θ-Fe3C and/or α-Fe nanoparticles coated with different carbon shells (amorphous carbon, graphene or graphite shells) are acquired. By exploring the relationship between phase composition, structure of catalysts and FTS performance, it is found that θ-Fe3C is confirmed to be FTS active, which exhibits superior C C chain growth ability, i.e., higher C5+ selectivity and lower CH4 selectivity. Meanwhile, graphene shell inhibits iron nanoparticles aggregation and stabilizes the catalysts.

Hydrogen evolution reaction (HER) under alkaline media plays a pivotal role in industrial electrocatalytic hydrogen production but even the platinum-based electrocatalysts suffer from high overpotential and low kinetics due to the high energy barrier of water dissociation. Here, by employing in-situ produced graphitic carbon nitride (g-C3N4) as template to induce the formation of a lamellar structure, we reported evenly dispersed Ru-doped Mo2C nanoparticles on ultrathin nitrogen-doped carbon nanosheets (Ru-Mo2C/CN) as a highly efficient alkaline HER electrocatalyst. The optimal Ru-Mo2C/CN displays a remarkable activity with a low overpotential of only 34 mV to afford 10 mA cm−2 and good stability of more than 30 h, which is much better than that of commercial Pt/C and recently reported electrocatalysts in the landmark literatures. Density functional theory (DFT) calculations show that the introduced Ru dopant on Mo2C significantly reduce the water dissociation energy barrier of HER and inhibit the competitive adsorption between H* and OH* on the surrounding Mo sites. This work highlights a simple yet effective strategy for designing electrocatalysts with excellent performance of hydrogen evolution reaction in alkaline media.

Atomistic scale models were developed and coupled with experimental investigation to deliver a functional understanding of catalytic activity and selectivity in the conversion of ethanol to 1,3-butadiene over Ag/ZrO2/SiO2. A detailed evaluation of the structural and electronic properties of the resultant catalyst models led to the identification of critical active sites of the catalyst. More importantly, the extent of Ag dispersion on the SiO2 support and relative proximity to ZrO2 were found to vary with the oxidation state of Ag and local coordination environment (Ag-OSiO2), allowing for critical control of ethanol conversion towards butadiene or ethylene. Simulations revealed that less dispersed or clustered Ag contain predominantly Ag0 charge state and promote conversion of ethanol to ethylene. The well-dispersed Ag/ZrO2/SiO2 catalyst instead contain a larger fraction of cationic Agδ+ and predominantly promote ethanol dehydrogenation and subsequent production of butadiene. The theoretical insights drawn were validated and confirmed experimentally using TEM, XRD and reactivity measurements demonstrating the effect of Ag dispersion on the selectivity of ethanol conversion.

As a promising alternative to the Haber–Bosch process for producing NH3, the electrocatalytic nitrogen reduction reaction (NRR) in the aqueous electrolyte has attracted much attention. However, the presence of sluggish reaction kinetics and competitive hydrogen evolution could result in poor activity and unsatisfactory selectivity. Herein, self-supported NbSe2 nanosheet arrays have been prepared and tested as electrocatalysts for NH3 electrosynthesis with a Faradaic efficiency of 13.9 ± 1.0% at −0.4 V versus the reversible hydrogen electrode (vs RHE) and a yield rate of 89.5 ± 6.0 μg h−1 mgcat.−1 at −0.45 V vs RHE in 0.1 M Na2SO4 under ambient conditions. Moreover, this electrocatalyst showed excellent durability during the 60-h electrolysis (no stable decay of Faradaic efficiencies and NH3 yield rates). Furthermore, density functional theory calculations disclosed that NbSe2 can effectively catalyze the dissociation of the adsorbed N2 molecule and thus promote the NRR process.

We report the structure of weak Lewis acid sites from silanol nests in high-silica zeolite Beta obtained by dealumination. Hydrogen bond interactions in silanol nests resulted in more electropositive hydrogens as Lewis acid sites compared with isolated silanols. The structure of the Lewis acid sites was confirmed using various characterization methods, such as NMR and IR, and DFT calculations. The amount of silanol nests, and the content and strength of the Lewis acid sites, gradually changed with the calcination temperature of high-silica zeolite Si-Beta. Double-bond migration of n-butene can be catalyzed by weak Lewis acid sites through σ species as intermediates, which was completely different from the Bronsted acid sites, as measured using in situ DRIFTS. The strengths and positions of Lewis acid sites on zeolite Si-Beta afforded reactant conversion and product selectivity in the isomerization of n-butene.

Cu,M/SSZ-13 (M = Na+, K+ and Ca2+) selective catalytic reduction (SCR) catalysts with Si/Al = 6 and M/Cu ratios varying from 0.1 to 1.0 are prepared by solution ion exchange, followed by slurry drying and hydrothermal aging at 800 °C. The catalysts are characterized with X-ray diffraction and N2 adsorption isotherms to probe their textural properties; 27Al and 29Si nuclear magnetic resonance and NH3 temperature-programmed desorption to probe their acidity properties and levels of dealumination; and electron paramagnetic resonance and H2 temperature-programmed reduction to quantitatively explore the nature of Cu moieties in the catalysts. These studies are followed by density functional theory calculations to elucidate Cu and co-cation interactions at an atomic level and SCR reaction tests to reveal correlations between the chemical and physical properties of the catalysts and their SCR performance. Through these comprehensive investigations, it is discovered that alkali metal co-cation addition can be used for the synthesis of highly stable, and highly active and selective Cu/SSZ-13 catalysts with relatively high Al content. In catalysts with optimal alkali incorporation, dealumination of the SSZ-13 substrate is largely inhibited, allowing high concentrations of SCR-active isolated Cu ions. At the same time, repulsive interactions between Cu ions and alkali metal co-cations preclude excessively high isolated Cu-ion loadings. Interplay between and optimization of these two factors is considered the underlying origin for this successful catalyst synthesis strategy. On the other hand, the alkaline earth co-cation Ca2+ fails to demonstrate any beneficial effects, since it destabilizes isolated Cu ions via site competition.

Graphene is an ideal model support to investigate the influence of carbon surface chemistry on catalytic reactions. Here a mild hydrothermal method was developed to synthesize graphene-supported iridium nanocatalysts from graphene oxide. By simply varying the hydrothermal conditions, the physicochemical properties of catalysts can be tuned, which can further affect their catalytic performances. Catalysts obtained at higher H2 pressure during hydrothermal process performed higher catalytic activities for hydrogenation of both p-chloronitrobenzene and cinnamaldehyde, benefiting from their higher reduction degrees of iridium nanoparticles. Interestingly, catalysts obtained at lower hydrothermal temperature performed higher activities for p-chloronitrobenzene hydrogenation but lower activities for cinnamaldehyde hydrogenation, due to their distinct surface chemistry of graphene. Through systematic characterizations on 11 catalysts prepared under various conditions, we found that lower hydrothermal temperature endows graphene with larger lateral dimension and more in-plane oxygenated surface groups, which facilitates the accessibility of nitro groups to catalyst surface via H-bond interaction as confirmed by density functional theory calculations. This is not true for cinnamaldehyde, of which adsorption on graphene via π-π stacking interaction is favorable for its hydrogenation.

Nitrogen doped carbon supported metal catalysts (Me/CNs) have been widely developed in the last decade in view of the promotional effects derived from N doping. However, the nature of the interaction between N and metal nanoparticles (NPs) is still not well illustrated. In this work, we suggest that graphitic N (Ng) may help nucleate and disperse, while pyridinic N (Np) serves as both anchors and dispersants. However, the interaction between NPs and CNs may not be localized just between NPs and N since the electron donated by NPs are not reserved by N. In fact, it is the energy gap of the Fermi levels between NPs and supports that could be the vital factor to determine the electron transfer. And this delocalization of electron transfer reduces the polarization between NPs and supports, which in turn suppresses the deep oxidation of NPs and keeps the higher metallic ratio for Me/CNs.

Production of synthetic natural gas (SNG) from coal is typically water intensive due to the need of increasing H2/CO ratio from 1 to 3 via water gas shift reaction. Here we report a water-saving dry methanation reaction that allows direct conversion of low H2 content syngas (H2/CO = 1) to methane without consumption of water for adjusting H2/CO to ≥ 3 and without production of waste water. Conventional Ni/Al2O3 catalyst is active for the dry methanation reaction but deactivates very rapidly due to carbon deposition and metal sintering. A Ni0.1Mg0.9Al2O4 catalyst exhibits much higher activity and better stability during steady state catalytic reaction and cyclic reaction-regeneration operations. Using a suite of characterization tools including BET, XRD, STEM, TEM, H2-TPR, Raman, TG-DSC, CO2 and NH3 TPD, and temperature-programmed hydrogenation, we reveal that carbon deposition did not occur on the surface of Ni particles in Ni0.1Mg0.9Al2O4 catalyst. Moreover, the population of small Ni nanoparticles (ca. 2 nm) increased after multiple reaction-regeneration operations possibly due to Ni redispersing via reversible diffusing among the framework of spinel. The exposure of active Ni surface and the formation of small-sized Ni nanoparticles together contributed to the stable and improved activity for dry methanation during the reaction-regeneration operations.

The structure–activity relationship is crucial in catalytic performance and material design but still largely obscure due to the complexity of heterogeneous catalytic systems. CO activation occurs widely in Fischer–Tropsch reactions and pyrometallurgy, and it is a key to understanding carburization. Here, we investigate the structure–activity relationship in Fe nanoparticles by reactive molecular dynamics simulations. We focus on two activities, the adsorption and dissociation of CO, and four structural characteristics, morphologies, sizes, defects, and heteroatoms. The results show that CO adsorption and dissociation varies with the change of nanoparticles. Line dislocation and vacancies can strikingly boost CO dissociation, suggesting an effective way to tune the CO dissociation rate. Further analysis shows that the Eley–Rideal mechanism possibly works in the early periods, followed by the Langmuir–Hinshelwood mechanism in the later periods for CO2 formation. Our results shed light on the mechanism and possible optimization of the carburization of iron.

CO2 activation and conversion are of significant interest. Here we report a mono-alkyl pyrocarbonate-bipyridinium salt intermediate to activate CO2 for synthesizing ethyl formate as a value-added product via tandem esterification and hydrogenation. The required basic bipyridine sites for CO2 activation and metallic Pd nanoparticles for hydrogenation were assembled in the same nano-cavity of a designer metal–organic framework (MOF). This MOF hybrid exhibits a high catalytic activity to generate ethyl formate (HCO2Et) (1333 μmol/gcat/h) with 93.5% selectivity at 412 K. The turnover frequency of HCO2Et based on the number of exposed Pd atoms is up to 22.2 h−1, higher than those of other catalysts previously reported for generating alkyl formates from CO2 under similar conditions.

To tune CH4 selectivity of Fe-based Fischer-Tropsch synthesis (FTS) in the initial stage is of prime scientific and industrial importance to further improve the catalyst performance. Herein, distribution of CH4 selectivity on the metallic Fe nanoparticle is predicted by DFT calculations and micro-kinetics analysis about the competition between C1 hydrogenations and C1 + C1 couplings on abundant Fe surfaces including Fe(1 0 0), Fe(1 1 0), Fe(1 1 1), Fe(2 1 1), and Fe(3 1 0). The results show that HCO mechanism (HCO → CH + O) is an available source of C1 species apart from CO direct dissociation. These Fe surfaces exhibit high effective barriers for CH4 formation, which is linearly correlated to the thermal stability of CH2 species. However, carbon chain prolongation on the more stable surfaces greatly depends on the coupling of C and CH species. On the less stable Fe(1 1 1) surface, the CO + C coupling is the main route for chain prolongation. Utilizing the effective barrier difference between the CH4 formation and the most feasible C1 + C1 coupling as a descriptor of CH4 selectivity, it is quantified that CH4 selectivity decreases in sequence of Fe(1 0 0) > Fe(2 1 1) > Fe(1 1 0) > Fe(3 1 0) > Fe(1 1 1). It is revealed that thermal stability of the CH2 species and exposition of the Fe facets could play essential roles in tuning CH4 selectivity. Trying to expand the area of Fe(2 1 1), Fe(3 1 0) and especially Fe(1 1 1) surfaces would greatly suppress CH4 selectivity without a decrease of activity. This work provides new insights and design principles for the Fe-based FTS catalysts.

Iron carbide phase formation during carburization of α-Fe catalysts were studied using in situ XRD, where the effect of varying carbon chemical potentials of CO/syngas/C 2 H 4 /C 2 H 2 gases and potassium promoter on the carburization behaviors was studied. The actual carburization capability of these gases follows an order of 2% CO/He 2 H 4 /He 2 /He 2 H 2 /He, which does not correlate well with the theoretical carbon chemical potential. In addition, the carburization rate and the formation of carbon-rich iron carbides are favored by potassium under CO or syngas, while inhibited by potassium under C 2 H 4 or C 2 H 2 . Temperature programmed carburization together with pulse experiments and DFT calculations indicate that the potassium promoter could weaken the adsorption ability of the C 2 H 4 and C 2 H 2 and thus reduce their carburization capabilities.

Fatty alcohols are widely used as detergents, but the large-scale synthesis still involves serious environmental pollution due to the use of toxic Cr-containing catalysts. Herein, a series of eco-friendly NixFey catalysts were successfully developed by utilizing a facile in-situ carbonization and reduction method, which exhibited excellent selectivity in the hydrogenation of stearic acid. The best performance was achieved on the Ni1.8Fe1.5 catalyst with 98% selectivity at 100% stearic acid conversion towards stearic alcohol. Further investigation revealed that Ni 3 Fe intermetallic compound was the effective active component. Besides, this catalyst can be easily separated and reused for several times without significant loss of activity.

New evidences have been collected to demonstrate that Pt localization plays a crucial role in modulating the catalytic performance of Pt/KL catalyst for n-heptane aromatization. Here, an improved atomic layer deposition (ALD) technique was applied to deliberately tune the locations of Pt nanoparticles (NPs) in the Pt/KL catalysts. Both scanning transmission electron microscopy (STEM) and CO diffuse reflectance infrared Fourier transform (CO-DRIFT) spectra suggest that Pt NPs can be gradually introduced into the depths of KL zeolite channels by the increment of exposure time of Pt precursor from 1/12 to 20 min in one ALD cycle. Moreover, once KL channels are blocked by some encapsulated species (AlOx as example), Pt NPs can only be localized on the orifices or external surface and grow larger. As a result, surprisingly high aromatics selectivity (84.3%) in n-heptane aromatization is performed for a Pt/KL catalyst with Pt dominantly localized in the depth of zeolite channels even at a low temperature of 420 °C. Comparatively, the aromatics selectivity decreases to 31.5% and heptene (mainly 1-C7=) selectivity is up to 51.3% for a Pt/KL catalyst with some of Pt deposited on the orifices or external surface of KL. A suggested mechanism of n-heptane cyclization based on density-functional theory (DFT) calculations was provided to delineate the optional reaction pathways on different Pt localizations. Pt sites inside the KL zeolite channels are more preferable for heptene cyclization than those near the zeolite orifices both from thermodynamically and kinetically. A heptene molecule absorbed on Pt inside zeolite cage was found to curve itself, reducing the reaction barrier for the breakage of C H bond to be only 1.37 eV, therefore activating the 6th carbon atom (the rate-determining step). The barrier comparison for that on Pt near the orifices is 1.84 eV. The calculated mechanism broadens the fundamental understanding of the role of zeolite channels for alkane reforming reactions.

The distinctive morphological and surface characteristics of platelet-like γ-Al2O3 were compared to a regular γ-Al2O3. γ-Al2O3 platelets display dominant (1 1 0) surface facets and higher densities of coordinative unsaturated penta-coordinate Al3+ (Al3+penta) sites than regular γ-Al2O3, as measured by solid-state magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). Such Al3+penta sites are also the preferred surface anchoring sites for tungsten oxide (WOx) species consistent with NMR analysis indicating that these sites are consumed upon WOx adsorption. The higher Al3+penta density on γ-Al2O3 platelets leads to greater WOx dispersion (or smaller WOx clusters), as demonstrated by scanning transmission electron microscopy and ultraviolet–visible spectroscopy, and WOx species at intermediate WOx surface concentration are the most active for the probe reaction of 2-butanol dehydration. WOx on γ-Al2O3 platelets approaches the highest turnover rates at higher surface densities than WOx on regular γ-Al2O3, yet with similar highest rate values for both series of catalysts. This indicates that different Al2O3 supports mainly affect the dispersion of supported WOx rather than the intrinsic reactivity of individual WOx clusters with similar size.

ZSM-22 zeolites with needle-shaped, bundle-shaped, as well as bulk-shaped morphologies are prepared by tuning hydrothermal synthesis conditions. These as-synthesized zeolites have similar crystallinity, Si/Al ratios and micropores revealed by XRD, XRF and BET. However, the oriented fusion of nanorods in the bundle-shaped ZSM-22 zeolite leads to the formation of more framework aluminum atoms over T1 + T2 + T3 sites on the 10-membered rings than that of needle-shaped ZSM-22 zeolite as detected by the 27Al 2D 3Q MAS NMR. The acidity properties determined by Py-FTIR and DMPy-FTIR show that the interfacial effect between the adjacent nanorods can effectively suppress Bronsted acid strength at the pore mouths and external surface. Interestingly, more Lewis acid sites are generated due to the interfacial defects. As a result, the Pt/Z-BUN catalyst with the weaker acidity and high dispersion of Pt exhibits the highest isomerization selectivity due to the more balanced bifunctionality between acid sites and metal sites among the as-prepared catalysts.

Fe/zeolites are important N2O abatement catalysts, efficient in direct N2O decomposition and (selective) catalytic N2O reduction. In this study, Fe/Beta and Fe/SSZ-13 materials were synthesized via solution ion-exchange and used to catalyze these two reactions. The nature of the Fe species was probed with UV–vis, Mossbauer and EPR spectroscopies and H2-TPR. These characterizations collectively indicate that primarily isolated and dinuclear Fe sites are present in Fe/SSZ-13, whereas Fe/Beta contains higher concentrations of oligomeric FexOy species. H2-TPR results suggest that Fe-O interactions are weaker in Fe/SSZ-13, as evidenced by the lower reduction temperatures by H2 and higher extents of autoreduction during high-temperature pretreatments in inert gas. Kinetic measurements show that Fe/SSZ-13 has higher normalized reaction rates in catalytic N2O decomposition, thus demonstrating a positive correlation between reaction rate and Fe-O binding, consistent with O2 desorption being rate-limiting for this reaction. However, Fe/Beta was found to display higher reaction rates in catalyzing N2O reduction by NH3. This latter result indicates that larger active ensembles (i.e., oligomers) are responsible for this reaction, consistent with the fact that both N2O and NH3 need to be activated in this case.

Polyol conversion to value-added products is of great interest for the bio-diesel industry. Photocatalytic oxidation processes may offer a green approach for polyol conversion; however the lack of comprehensive mechanistic understanding from an interdisciplinary perspective limits or even misleads the design of highly selective and efficient photocatalysts for such process. Here we have studied the photocatalytic polyol conversion on pristine TiO 2 and metal (Au, Pd, and Pt) nanoparticles (NPs) decorated TiO 2 using ethylene glycol (EG) as the model compound. We have developed a mechanistic picture at molecular level by coupling in-situ surface science study on rutile (110) surface with in-situ vibrational-mass spectrometry study on TiO 2 nanopowders. The C C bond cleavage was found to be the only pathway in EG photo-conversion under deaerated conditions, leading to the formation of formaldehyde and hydrogen. We rationalized that the desorption of the surface adsorbed H (H ads ) to be the rate determining step (RDS), making pristine TiO 2 a poor photocatalyst that only catalyze the EG conversion at very low surface coverages. The addition of metal NPs on TiO 2 surface promotes the desorption of H ads significantly, thus leading to an enhanced C C bond cleavage performance at higher surface coverages that is more applicable.

Being a suitable way for achieving the maximum efficiency of atoms, the atomically dispersed metals are playing an ever-increasingly important role in bridging heterogeneous and homogeneous catalysis. It is extremely challenging for dispersing metals in atomic-scales as the applicable high-loading catalysts for industry. The reducible and defective supports or metal surfaces are commonly chosen for anchoring the metals. We here report that atomically-dispersed but high-loading (15 wt%) metals were achieved by covalent-bonding to irreducible SiO 2 (though silanol groups) which is realized by a simple urea hydrolysis assistant hydrothermal-deposition method. The Cu O Si bonding tailors the structural and electronic states of catalyst by maximum of atom efficiency and tuning electronic effects. The intrinsic performance of C O hydrogenation was thus boosted by one- to two- orders-of-magnitude in comparison with impregnated and precipitated catalysts. The choices of metals include Cu, Zn, Ni, Co and Mn, showing potentials for a category of applied materials.

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.

This work highlights a novel hybrid catalyst, intermetallic PdZn on CN@ZnO (PdZn/CN@ZnO), which serves as a highly efficient heterogeneous catalyst for semihydrogenation of 2-methyl-3-butyn-2-ol utilizing water as the solvent. Compared with intermetallic PdZn on ZnO (PdZn/ZnO), PdZn/CN@ZnO displays almost sixfold higher TOF while retaining high selectivity. It is assumed that the introduction of biomass-derived hydrophilic nitrogen-doped carbon into the ZnO helped to promote catalyst dispersion in aqueous media, ensuring better mass transfer. Further experiments and theoretical calculations showed that from Pd particles to intermetallic PdZn, the decrease of corner and edge Pd atoms might be a factor leading to the improvement of selectivity. Recycling experiments demonstrated that the PdZn/CN@ZnO catalyst could be reused at least eight times without significant decrease in activity or selectivity. Furthermore, when applied to industrially relevant alkenols that are building molecules for the production of vitamin E, the present catalyst still offered excellent performance. It is expected that the present catalytic system will demonstrate its high potential for practical production of vitamin E.

The catalytic performances in steam reforming (SR) and aqueous phase reforming (APR) of glycerol of a bimetallic Pt-Mn catalyst supported on activated carbon are investigated and correlated with the surface properties of the catalyst. Under SR conditions, Mn showed a significant promoting effect over Pt/C, both in terms of hydrogen production rate and conversion, with a higher selectivity toward the glycerol dehydration products. Upon addition of Mn the amount of strong Lewis acid sites increased, promoting the dehydration of glycerol and favoring the C[sbnd]O over C[sbnd]C cleavage at expenses of hydrogen selectivity. Conversely, under APR conditions, a slightly higher hydrogen selectivity and only minimal enhancement in hydrogen production were found, while the products selectivity was comparable to Pt/C. Most of Mn leached into the aqueous media, but the remaining (

High field quantitative 27Al single pulse (SP) MAS NMR combined with temperature programmed desorption (TPD) of ethanol is used to study the surface of γ-Al2O3 during phase transformation processes induced by calcination in the temperature range of 500–1300 °C. Following ethanol adsorption, ethylene is generated during TPD with a desorption temperature above 200 °C. The amount of ethylene decreases monotonically with increasing calcination temperature prior to TPD. Significantly, 27Al SP MAS NMR reveals that the amount of penta-coordinated Al3+ ions also decreases with increasing calcination temperature. A quantitative (within experimental error) correlation between the amount of penta-coordinated Al3+ ions and the amount of strongly adsorbed ethanol molecules (i.e., the ones that convert to ethylene during TPD) is obtained. These results provide good evidence for a proposal that the penta-coordinated aluminum sites are the catalytic active sites on alumina surfaces during ethanol dehydration reaction across the entire course of γ-to-α Al2O3 phase transformations.

Micro/mesoporous materials with different mesoporosities were prepared through recrystallization of H-ZSM-22 zeolite in alkaline solution with cetyltrimethylammonium bromide template (CTAB). The structure, morphology, pore properties, acidity and isomerization performance of the catalysts by using the resulting materials were characterized and assessed. The dissolution and recrystallization procedure introduced the well-developed mesoporous structure of MCM-41 type with the meso-scale channels of about 3 nm in size on the outer surfaces of the microporous H-ZSM-22 zeolites, forming the micro/mesoporous materials, which possessed increased weak B acid sites at the pore mouths and a reduced amount of total acid sites. It is shown that the presence of well-developed mesopores could remarkably improve the selectivity to multi-branched products and suppress the side cracking reactions in n-dodecane isomerization. The micro/mesoporous Pt/ZSM-22/MCM-41 bifunctional catalyst with suitable recrystallization degree exhibits high isomerization selectivity under high conversion in long-chain n-alkane isomerization compared to the original microporous Pt/H-ZSM-22 catalyst.

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 facile way to prepare graphene-supported Ru catalysts was developed here. For the first time, functionalized graphene obtained from thermal exfoliation of graphite oxide at low temperature (200 °C) under air atmosphere was used to support Ru nanoparticles (2.3 nm) with the simple method of incipient wetness impregnation. Heat treating at 700 °C in N2 flow did not change the mean size but made Ru nanoparticles electron rich. The electronic effect had a great influence on the activities of benzene and p-chloronitrobenzene hydrogenation but little influence on the activity of cinnamaldehyde hydrogenation and its selectivity of C O bond. A geometric effect benefited from the distinctive preparation method was supposed to be another factor accounting for these catalytic phenomena. Comparing with CNTs-supported Ru catalysts obtained from a similar method, we can see clearly that graphene with the two-dimensional flexible graphitic surface could modulate the electronic and geometric structures of Ru catalysts in an unusual way. Additionally, this work provides the possibility of producing graphene-based precious metal catalysts on a large scale.

ZnO nanoparticles with differing dominant facets were prepared and characterized by a complimentary of techniques such as X-ray diffraction, electron microscopy, temperature programmed desorption of H2O, and Fourier transform infrared spectroscopy analysis of adsorbed D2O. For the first time, water interaction/activation is compared on ZnO polar and non-polar facets. We report that non-polar facets exhibit high activity in water activation, which favors reactions such as ketonization and steam reforming in which dissociated water is involved. The distinct water dissociation on ZnO non-polar facets could be related to its facile formation of oxygen vacancies under realistic reaction conditions.

•Fe-substituted ZSM-22 zeolites are prepared via an OSDA-free route.•Characterizations confirm the Fe incorporation in the zeolite framework.•The Fe substitution for Al in ZSM-22 zeolite framework especially reduces the B acidity.•Pt/[Al,Fe]-ZSM-22 catalyst exhibits improved isomerization performance.

For the purpose as stated in title, three Ru catalysts were prepared with the same treated carbon nanotubes. One has most of Ru nanoparticles confined inside the channels, and the other two have most of Ru nanoparticles outside through different preparation methods. Heat treating was performed to obtain another three catalysts. Characterization by X-ray photoelectron spectroscopy indicated that heat treating made Ru nanoparticles electron rich. Hydrogenation of benzene, p-chloronitrobenzene, and cinnamaldehyde was chosen as model reactions to evaluate all these catalysts. Electronic effect plays an important role in catalytic performance. The electron-rich Ru would be favorable for p-chloronitrobenzene hydrogenation, but unfavorable for benzene hydrogenation. For cinnamaldehyde hydrogenation, the electron-rich Ru would be favorable for adsorption of CO bond rather than CC bond and thus promoted the selectivity to cinnamyl alcohol. A confinement effect induced by the electronic effect has different influences on these substrates, and it can be enhanced by heat treating for all the reactions. Finally, we drew a correlation of electronic structures between catalysts and substrates accounting for these phenomena.

The effects of Pt precursors on the performance of Pt/ZSM-22 catalysts for n -hexadecane hydroisomerization were investigated with 0.5 wt.% platinum loading using three platinum precursors: Pt(NO 3 ) 2 , H 2 PtCl 6 , and Pt(NH 3 ) 4 Cl 2 . The catalyst derived from H 2 PtCl 6 exhibits the highest platinum dispersion and n Pt/ n A value and displays better isomerization activity and selectivity. Three effects can be traced back to the precursors: the valence state of Pt, the location of Pt (in cationic or anionic group), and the existence of chloride. The predominant effect is that of valence states of Pt in precursors, which play a crucial role in determining the textural properties (both particle size and crystal structure) of catalysts. Different crystal orientations of Pt 0 are found on the reduced samples, with Pt(IV) precursors oriented along the [0 1 1] crystallographic axis, while those with Pt(II) precursors are oriented along the [0 0 1] axis. The former favors smaller Pt particles and exposes more active Pt{1 1 1} corner sites, while the latter exhibits larger Pt particles and exposes more Pt{1 0 0} facets, as revealed by combining HRTEM with CO-IR studies. Moreover, Pt{1 1 1}/ZSM-22 shows higher isomerization selectivity than Pt{1 0 0}/ZSM-22. The other effect is location of Pt in precursors. Compared with the sample using Pt(NH 3 ) 4 Cl 2 precursor, the catalyst with (NH 4 ) 2 PtCl 4 precursor exhibits smaller particles and higher platinum dispersion and facilitates isomerization reactivity. The existence of chloride is also a nonignorable effect. The samples containing chloride ions without amine groups in precursors favor platinum dispersion due to avoiding autoreduction by NH 3 during the calcination process.