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Reverse water gas shift (RWGS) reaction is an attractive approach to convert CO2 with renewable H2 to produce CO. However, this reaction is always accompanied by undesirable methanation reaction lowering the CO selectivity, particularly, at low reaction temperature and on Ni catalysts. Herein, a strategy of deposition of inert Ag on the surface of Ni to block methanation reaction during RWGS for selective conversion of CO2 toward CO was reported. Characterizations showed that in contrast to formation of bulk Ni−Ag alloy, both Ag particle and highly dispersed Ag are direct contacting with Ni particle. Surface Ag modifies the property of Ni geometrically and electronically, resulting in reduced accessible surface Ni sites and Ni ensemble size, as well as electron transfer from Ni to Ag. Consequently, both the amount and strength of CO adsorption are reduced, which facilitates CO desorption and reduces CO methanation activity. The Ag modification tunes Ni/SiO2 from selective methanation to selective RWGS, with 100 % CO selectivity on Ni‐0.3 Ag/SiO2 (Ag/Ni=0.3) at 400 °C with gas hourly space velocity (GHSV) >300 L g−1 h−1 and CO selectivity is >80.7 % even at a low GHSV of 15 L g−1 h−1. Moreover, the Ni‐0.3 Ag/SiO2 appears to be very stable for RWGS reaction. [ABSTRACT FROM AUTHOR]

A series of rutile TiO2-supported Ni catalysts with varying Ni sizes were prepared and reduced at 650 °C to explore the effect of Ni size on the strong metal–support interactions (SMSI) and its consequences on the hydrodeoxygenation (HDO) of m-cresol at 350 °C and atmospheric pressure. When the Ni size increases from 4 to 29.1 nm, the SMSI becomes stronger, e.g., the thickness of the TiOx overlayer and the coverage extent of TiOx on the Ni particle surface increase. Direct deoxygenation to toluene is the dominant pathway on Ni/TiO2 catalysts with varying Ni loadings, with almost no CH4 being formed. These results indicate that the TiOx overlayer significantly alters the property of Ni. That is, the C-C hydrogenolysis activity on bare Ni is completely inhibited due to SMSI, while the deoxygenation activity is improved at the Ni-TiOx interfacial perimeter sites. Meanwhile, the turnover frequency of HDO on small Ni particles of 4 nm is > 2 times higher than that on large Ni particles of 29.1 nm, indicating that the small Ni particle with moderate SMSI appears to be optimal for the direct deoxygenation of m-cresol to toluene. The results suggest HDO activity may be enhanced by tuning the metal particle size and SMSI degree. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of carbon dioxide to fuels has been recognized as a perspective way to address the environmental and energy issues. Herein, the novel Au decorated Cu2O electrocatalysts were synthesized via the galvanic replacement reaction and the successive pre‐reduction by linear voltammetry (LSV) method. In contrast to Cu2O, CO formation became dominant over HCOOH and H2 on AuxCu2O, and a remarkably enhanced selectivity of C2H4 was obtained beyond −1.1 V vs. RHE. Among them, Au0.02Cu2O exhibited the highest Faraday efficiency (FE) of C2H4 of 24.4 % at −1.3 V vs. RHE, which was as high as 2∼2.5 and 5 times of those on other two AuxCu2O and bare Cu2O, respectively. Meanwhile, it is demonstrated that the optimal ratio of Au/Cu was essential for effective sequential catalysis between Au and Cu2O to enhance C−C coupling. Furthermore, the effect of copper states resulting from different pre‐reduction methods on the selectivity of C2H4 was explored. A half decrease of C2H4 FE was observed on HPR‐Au0.02Cu2O (high potential reduced) relative to the LSV reduced Au0.02Cu2O, which was ascribed to the different content of Cu0 and residual Cu+ in two catalysts. Our results demonstrate an effective approach to construct Cu2O based bimetallic catalysts for ethylene formation from CO2. [ABSTRACT FROM AUTHOR]

Catalytic reduction of CO 2 with renewable H 2 to CO via the reverse water gas shift (RWGS) reaction is an attractive approach to recycle CO 2 and control net emission of CO 2 to atmosphere. However, low activity and high CH 4 selectivity at low temperatures limited the practical implementation of the reaction. Herein, Pt-Re/SiO 2 catalysts with varying amount of Re were prepared with co-impregnation and tested for the RWGS reaction. Characterization results indicated that the oxophilic ReO x (0 ≤ x ≤ 3.5) located in close proximity to Pt particle, modified the surface of Pt by both partial coverage and electronic interaction, resulting in the reduced number of sites for and weakened strength of CO adsorption. At 400 °C, the turnover frequency (2.30 s−1) on the optimal Pt-Re/SiO 2 catalyst (Pt/Re = 1.91) is 3.9 times higher than that on Pt/SiO 2 under differential conditions, and the apparent activation energy is lowered. In contrast to Re/SiO 2 which produces significant amount of CH 4 , the CO selectivity on Pt-Re/SiO 2 maintained > 96.2 % under integral conditions. Reaction order analysis revealed that Pt facilitates H 2 activation whereas the oxophilic ReO x enhances CO 2 adsorption and activation. The perimeter sites at the Pt/ReO x interface with a balanced hydrogenation and C-O cleavage properties synergistically improve the RWGS activity while inhibiting CH 4 production. [Display omitted] • ReO x (0 ≤ x ≤ 3.5) modified the surface of Pt by both partial coverage and electronic interaction. • ReO x modification weakened CO adsorption on Pt and enhanced CO selectivity (> 96.2 %). • TOF of RWGS on optimal Pt-Re/SiO 2 (2.30 s−1) is 3.9 times higher than that on Pt/SiO 2. • Reaction kinetic analysis revealed Pt and ReO x activate H 2 and CO 2 , respectively. • The synergy of Pt and ReO x enhanced RWGS activity and inhibited CH 4 formation. [ABSTRACT FROM AUTHOR]

Conversion of m-cresol was studied on a Pt/HBeta catalyst at 225-350 °C and ambient hydrogen pressure. At 250 °C, the reaction proceeds through two major reaction pathways: (1) direct deoxygenation to toluene (DDO path); (2) hydrogenation of m-cresol to methylcyclohexanone and methylcyclohexanol on Pt, followed by fast dehydration on Brønsted acid sites (BAS) to methylcyclohexene, which is either hydrogenated to methylcyclohexane on Pt or ring-contracted to dimethylcyclopentanes and ethylcyclopentane on BAS (HYD path). The initial hydrogenation is the rate-determining step of the HYD path as its rate is significantly lower than those of subsequent steps. The apparent activation energy of the DDO path is 49.7 kJ mol−1 but the activation energy is negative for the HYD path. Therefore, higher temperatures lead to the DDO path becoming the dominant path to toluene, whereas the HYD path, followed by fast equilibration to toluene, is less dominant, owing to the inhibition of the initial hydrogenation of m-cresol. [ABSTRACT FROM AUTHOR]

Na promoted Pt/TiO2 catalysts have been studied under high severity, near equilibrium, conditions for use as a single stage WGS catalyst. Addition of 3 wt% Na to a 1 wt% Pt/TiO2 catalyst has been found to improve water gas shift activity significantly compared to Pt/TiO2, Pt/CeO2, and Pt–Re/TiO2 catalysts. This catalyst is stable when the reaction temperature is higher than 250 °C. Deactivation occurred when the reaction temperature was lower than 250 °C, however, returning the temperature to higher than 250 °C fully recovered activity. TEM observations revealed that addition of Na inhibited Pt particle sintering. These results suggest that Na promoted Pt/TiO2 is a promising single stage water gas shift catalyst for small scale hydrogen production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni is unselective for RWGS due to competition from methanation during CO 2 reduction. • CO 2 reduction follows RWGS to CO and then methanation to CH 4. • MoO x modifies the surface of Ni by both geometric and electronic effects. • Bimetallic NiMo catalyst with Mo/Ni of 0.1 is selective for methanation. • Bimetallic NiMo catalyst with Mo/Ni of 1 is selective for RWGS. Catalytic reduction of CO 2 to CO via reverse water gas shift (RWGS) reaction provides a feasible approach to utilize CO 2 , since CO can be further converted to various versatile products through the syngas routes. Ni-based catalysts are low cost and have a high activity for CO 2 reduction but are nonselective for RWGS due to competition from methanation. In this work, we demonstrated that surface modification of Ni by MoO x can be tailored to tune the reactions of RWGS and methanation. The addition of MoO x improves Ni dispersion through strong interactions whereas partially reduced MoO x modifies the surface of Ni particles through both geometric coverage and electronic modification. No CO adsorption was observed at room temperature on the NiMo catalyst with a Mo/Ni ratio of 1, confirmed by density functional theory calculation. Tracking product evolution showed that CO 2 is first reduced to CO through RWGS on the Ni catalysts and methane is a product of CO hydrogenation. Apparent activation energy analysis indicates that the overall reaction is controlled by CO desorption. Addition of a small amount of Mo (Mo/Ni ratio of 0.1) shifts the reaction further to methanation selective with ∼100% CH 4 selectivity as MoO x aids in the activation of both CO 2 and CO. In contrast, the addition of a large amount of Mo (Mo/Ni ratio of 1) shifts the reaction to RWGS selective with a CO selectivity > 94%. This is attributed to the enhanced CO desorption from the surface as a result of MoO x modification. [ABSTRACT FROM AUTHOR]

Pd/HZSM-5 catalyst prepared via glow discharge plasma reduction followed by calcination thermally showed enhanced stability for methane combustion. In order to investigate the plasma catalyst preparation mechanism, oxygen glow discharge, initiated at room temperature, has been employed for reduction of Pd/HZSM-5 catalyst. The catalyst characterization using XRD and XPS analyses demonstrates that oxygen glow discharge plasma is also able to reduce Pd/HZSM-5 catalyst. This suggests that the electronic effect plays an important role in the treatment of catalyst using glow discharge. This also confirms that the thermal effect of the glow discharge reduction can be ignored. A highly durable catalyst for methane combustion has been obtained from calcination of the glow discharge reduced sample. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent advances in vapor phase hydrodeoxygenation (HDO) of phenolics are reviewed. • Reaction network of HDO on group 10 metals (Ni, Pd and Pt) are discussed. • Reaction mechanism of HDO on group 10 metals are compared. • Novel strategies on selective deoxygenation to aromatics are reviewed. Catalytic hydrodeoxygenation (HDO) of phenolics is a crucial step to convert lignin-biomass to chemicals and fuels. Catalysts based on group 10 metals (Ni, Pd and Pt) are widely used in HDO of phenolics. However, achieving a high yield toward the desirable product remains a challenge since a number of competing reactions take place at the same time, resulting in a complex product distribution. Herein, we review the recent advances in understanding the reaction mechanism on group 10 metal based catalysts and the novel strategies for selective deoxygenation of phenolics to aromatics on these catalysts under mild conditions (intermediate temperature and atmospheric pressure). Typically, HDO on Ni, Pd and Pt involves three main reaction pathways: a) hydrogenation to cyclohexanones/cyclohexanols; b) deoxygenation to aromatics, and c) C − C hydrogenolysis to CH 4. Among the possible mechanisms proposed for deoxygenation to aromatics, the partial hydrogenation mechanism shows the lowest barrier for C − O cleavage, and is therefore most likely to happen. Strategies such as increasing affinity to the O atom of phenols on the surface of Ni, Pd and Pt based catalysts by either reducing the particle sizes, alloying with an oxophilic metal, modifying the metal catalyst with a reducible oxide, or combining with an acidic zeolite have been reviewed. These strategies have been shown to improve the selectivity of HDO to aromatics over the hydrogenation and C − C hydrogenolysis products and are expected to provide useful guidance for rational design of the selective HDO catalysts. [ABSTRACT FROM AUTHOR]

The Cover shows the major reaction pathways of hydrodeoxygenation of m‐cresol to hydrocarbons on a bifunctional Pt/HBeta catalyst, consisting of both metal site (Pt) and Brønsted acid site (BAS). In their Full Paper, Sun et al. demonstrate that the reaction proceeds through both a direct deoxygenation path (DDO) to toluene and a hydrogenation‐deoxygenation path (HYD) to methylcyclohexane and ring contraction products. The selectivity between the two paths depends on competition between the initial rates of deoxygenation and hydrogenation of cresol. The apparent activation energy is positive for the DDO path, whereas it becomes negative for the HYD path. More information can be found in the Full Paper by Sun et al. on page 551 in Issue 3, 2016 (DOI: 10.1002/cctc.201501232). [ABSTRACT FROM AUTHOR]

[Display omitted] • The strong metal-support interaction (SMSI) of Pt/TiO 2 is dependent on TiO 2 facet. • The order of encapsulation degree is Pt/TiO 2 -100 > Pt/TiO 2 -001 > Pt/TiO 2 -101. • Encapsulation correlates well with reduction degree of TiO 2 and location of oxygen vacancy. • The highest reaction rate and turnover frequency were achieved on Pt/TiO 2 -001. Metal/reducible metal oxide catalysts are widely used in hydrodeoxygenation (HDO) reactions for upgrading bio-oil to produce chemicals and fuel components. Under such strong reducing condition, the strong metal-support interaction (SMSI) should take place, however, few work has been devoted to understand the effect of facet of metal oxide on the SMSI and its consequence on HDO performance. Herein, Pt supported on anatase TiO 2 with varying dominative exposed facets of (1 0 1), (1 0 0) and (0 0 1) were prepared and tested in HDO of m-cresol at 350 °C and atmosphere H 2 pressure. The degree of SMSI of Pt/TiO 2 is strongly dependent on the facet of TiO 2 when reduced at 350 °C, and the degree of encapsulation decreases following the order of Pt/TiO 2 -100 > Pt/TiO 2 -001 > Pt/TiO 2 -101. The encapsulation correlates well with the reduction degree of TiO 2 and the location of oxygen vacancy, which are resulted from varied oxygen vacancy formation and anisotropic diffusion rates in different facets. The intermediate SMSI is achieved on TiO 2 -001, which creates the maximal density of Pt-O v -Ti3+ sites at the interfacial perimeter of TiO x /Pt for deoxygenation of m-cresol, resulting in the highest reaction rate and turnover frequency (TOF) while the lowest activation energy (E a). In contrast, the maximum SMSI on TiO 2 -100 leads to the lowest deoxygenation rate while the highest E a. This work provides insight into facet dependent SMSI of Pt/TiO 2 and indicates the HDO activity can be finely tailored by tuning the facet of TiO 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • C-H activation on Cr/TiO 2 is mediated by surface-stabilized hydroperoxyl. • The production of OH radicals via Fenton mechanism is energetically unfavorable. • The C-H activation proceeds through a homolytic mechanism with a barrier of 0.44 eV. • The relative strength between the acidic and basic site determines the reactivity. • The presence of water does not alter the reaction pathways. Direct conversion of methane to methanol is an attractive alternative to the indirect, energy-intensive syngas production and conversion route. Herein, we present a comprehensive density functional theory (DFT) study of converting methane directly into methanol over the Cr single atom catalyst (SAC) on anatase TiO 2 (1 0 1) surface. Cr species stabilize in the form of CrO with H 2 O 2 as oxidant, on which methane reacts with the deprotonated H 2 O 2 via an Eley–Rideal mechanism. The formation of a three-centered transition-state structure is observed in the rate-determining C H bond activation step with an activation barrier of 0.44 eV. The H 2 O 2 not only serves as the oxidant for the formation of the most stable and reactive CrO species, but also enters the coordination sphere of the Cr center and acts as a highly effective H acceptor, which significantly lowers the activation barrier for C H bond cleavage. Over different Cr-O pairs, methane C H bond activation energy is found to linearly correlate with the energy difference between the d-bond center (ε d) of Cr and p-band center of O (ε p). The presence of water changes the relative stability of the reaction intermediates but does not alter the reaction pathways. This study demonstrated the ability of Cr SACs for catalyzing direct conversion of methane to methanol under mild conditions and would stimulate further interests in designing active Cr catalysts for methane conversion. [ABSTRACT FROM AUTHOR]

A series of CeO 2 catalysts with varying Na content were tested for vapor-phase ketonization of propionic acid at 350 °C. Na+ diffuses into the CeO 2 lattice and excess NaO x accumulates on the surface, which dilutes surface contiguous and partially covers Ce-O acid-base pairs. The intrinsic reaction rate in terms of surface area always decreased with increasing Na, likely originated from the altered acid-base property and the increased distance and steric hindrance between enolate and carboxylate for C-C coupling. On the other hand, the stability was significantly improved, with almost no deactivation being observed for Na 0.1 Ce 0.9 O x. This improvement is resulted from the dilution and/or coverage effects of NaO x , which significantly reduces accumulation of inactive bidentate propionate. This work demonstrates a strategy of dilution and/or coverage of surface acid-base pairs by alkaline metal oxides to reduce bidentate carboxylate and therefore to enhance the stability of metal oxide catalysts toward ketonization of carboxylic acids. [Display omitted] • Na dilutes surface contiguous and partially covers Ce-O acid-base pairs. • Doping Na significantly enhanced the stability of CeO 2 for ketonization reaction. • Na dilution and coverage effects reduced coverage of bidentate propionate. • Reduced coverage of bidentate propionate led to improved stability. [ABSTRACT FROM AUTHOR]

• HDO of m-cresol was studied at 250 °C and 1 atm on Pt/Beta with varying BAS/Pt. • Increasing BAS density increases diffusion constraints of m-cresol and products. • Increasing BAS/Pt ratio reduces both the reaction rate and TOF of HDO. • Products distribution varies due to the combined effects of BAS/Pt and diffusion. • A low BAS/Pt is beneficial for improving stability by reducing coke deposition. Metal/zeolite bifunctional catalysts have been widely explored for hydrodeoxygenation (HDO) of phenolics. However, the effect of acid-metal balance is not clearly understood because it is difficult to decouple this from other effects. In this work, a series of 1 wt.% Pt/Beta catalysts with different Brønsted acid site (BAS) to surface Pt ratios (BAS/Pt) were prepared by varying only the density of BAS, and tested in HDO of m-cresol at 250 °C and atmospheric pressure. Increasing BAS density increases intra-crystallite diffusion constraints of m-cresol/products due to strong chemisorption on BAS, and therefore slows their transportation through BASs toward the Pt sites inside the micropores of zeolite. As a result, both the reaction rate and turnover frequency of HDO are reduced with increasing BAS/Pt ratio. Increasing BAS/Pt ratio increases the yield of ring contraction products but reduces the yields of methylcyclohexane and methylcyclohexanone, because of the increased acid functionality and diffusion constraints of intermediates. A low BAS/Pt ratio is beneficial for improving catalytic stability by reducing coke deposition. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Nickel phyllosilicate derived Ni/SiO 2 catalysts were successfully synthesized. • Ni particles of 2–3 nm are uniformly dispersed on support. • The small Ni particles promote selective deoxygenation of m-cresol to toluene. • The small Ni particles inhibit C C hydrogenolysis to CH 4. Abstract The nickel phyllosilicate derived Ni/SiO 2 catalysts (PS-Ni) were prepared and tested for vapor phase hydrodeoxygenation of m-cresol at 250–300 °C and 1 atm H 2. Calcination at 400 °C followed by reduction at 500 °C of the nickel phyllosilicate resulted in uniformly dispersed Ni particles with an average size of 2–3 nm on the support. These particles are much smaller than those in a 20 wt.% Ni/SiO 2 catalyst prepared by a conventional impregnation method (IMP-Ni) with the same Ni loadings (25.9 nm). On PS-Ni, the yield of hydrogenation products (methylcyclohexanone and methylcyclohexanol) decreases while that of deoxygenation product (toluene) increases, as compared to those on IMP-Ni at the same m-cresol conversion. At 300 °C, PS-Ni results in increased overall intrinsic reaction rate and turnover frequency for toluene formation by 8 and 10 times, respectively, relative to IMP-Ni. This improved selective deoxygenation of m-cresol to toluene is mainly due to the much smaller Ni particle size in PS-Ni. Furthermore, C C hydrogenolysis to CH 4 is greatly inhibited on PS-20Ni. Stability test showed that PS-20Ni deactivated with time on stream, and the strong adsorption of oxygen-containing compounds on the acid sites in PS-20Ni is speculated to be the major reason of deactivation. [ABSTRACT FROM AUTHOR]

Conversion of propionic acid to gasoline-range molecules was investigated at 350 °C on a series of ZSM-5 catalysts with varying density of Brønsted acid sites (BAS), achieved by ion exchange of proton with Na + . Ketonization of propionic acid to 3-pentanone is the primary reaction, with the sequential aldol condensation to dipentanone alcohol being the secondary. The major reaction pathway for forming the aromatics involves dehydration, cyclization, dehydration and hydride transfer from dipentanone alcohol, leading to the formation of C 10 aromatics before being dealkylated to lighter aromatics. Temperature programmed desorption of propionic acid indicates that the reaction initiates with acylium cation formation on BAS through dehydration. Comparing the turnover frequencies of ketonization and aldol condensation on ZSM-5 with varying density of BAS indicates that BAS is the active site for both reactions. The propionic acid feed deactivates the catalyst faster than the 3-pentantone feed due to a stronger adsorption of propionic acid on the acid sites of ZSM-5. [ABSTRACT FROM AUTHOR]

In this work, a novel glow discharge plasma treatment of Pd/HZSM-5 catalyst, followed by calcination thermally, has been conducted. Such prepared catalyst presents a higher catalytic activity and an enhanced stability over the catalyst prepared without plasma treatment. The methane conversion over the plasma treated catalyst is close to 100% at 450 °C, but it is only ca. 50% at the same temperature over the catalyst without plasma treatment. The XPS, H2 chemisorption and XRD characterizations confirm an enhanced dispersion has been achieved with the plasma reduction (during treatment) followed by oxidation (during calcination). Upon FT-IR analyses, the plasma treatment, followed by calcination thermally, also leads to enhanced Bro¨nsted and Lewis acidities. The amount of Bro¨nsted acid sites of the plasma treated Pd/HZSM-5 catalyst is 1.13 times larger than that of the catalyst without plasma treatment, while the amount of Lewis acid sites of the plasma treated Pd/HZSM-5 catalyst is 1.21 times higher. The enhanced acidities are definitely helpful to increase the dispersion of PdO over the support and improve the interaction between PdO and HZSM-5 support, which leads to a remarkable improvement in the catalyst stability. [Copyright &y& Elsevier]