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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]

Selective hydrodeoxygenation (HDO) of biomass lignin‐derived phenolic compounds to aromatics is a demanding reaction. Oxophilic Ru based catalysts can catalyze direct deoxygenation but suffer from competing C−C hydrogenolysis to CH4 at 350 °C and hydrogenation of phenyl ring at 250 °C under atmospheric pressure. In this work, a solid solution Ru0.05Ce0.95O2 catalyst was hydrothermally synthesized, characterized and tested for HDO of m‐cresol. The Ru species is highly dispersed in the solid solution as isolated atoms and/or subnanometer clusters as a result of strong Ru−O−Ce interaction, and the catalyst shows high concentration of oxygen vacancies. In contrast to nonselective Ru/SiO2, Ru0.05Ce0.95O2 selectively catalyzes deoxygenation to toluene while significantly inhibits C−C hydrogenolysis and hydrogenation. Moreover, the overall intrinsic HDO rate on Ru0.05Ce0.95O2 is 2.2 and 8.8 times higher than those on Ru/CeO2 and Ru/SiO2, respectively. The Ru−OV−Ce sites were proposed to be the active sites for deoxygenation. Inhibition of C−C hydrogenolysis and phenyl hydrogenation can be ascribed to the reduced size of the Ru ensembles due to the strong interaction in the solid solution. [ABSTRACT FROM AUTHOR]

Hydrodeoxygenation of m‐cresol was investigated at 350 °C and atmospheric pressure over Pt/TiO2 reduced at different temperatures. Increasing reduction temperature results in an increased degree of strong metal‐support interactions (SMSI). Consequently, both the number of the perimeter sites at the Pt‐TiO2 interface and the oxygen vacancy sites in close proximity to Pt are increased. Increasing reduction temperature from 350 to 550 °C leads to the turnover frequency of toluene formation to increase by more than 3 times. These results indicate that the perimeter sites at the Pt‐TiO2 interface with oxygen vacancy are the more active sites for deoxygenation than the bare Pt sites. The results also suggest that balancing the SMSI effect and the number of exposed Pt sites is essential for an efficient catalyst for deoxygenation of phenolics to aromatics. Insert text for Table of Contents here. ((The Table of Contents text should give readers a short preview of the main theme of the research and results included in the paper to attract their attention into reading the paper in full. The Table of Contents text should be different from the abstract and should be no more than 450 characters including spaces.)). Increasing reduction temperature of Pt/TiO2 from 350 to 550 °C results in an increased degree of strong metal‐support interaction, which leads to the turnover frequency of toluene formation from hydrodeoxygenation of m‐cresol to increase by more than 3 times. These results indicate that the perimeter sites at the Pt‐TiO2 interface with oxygen vacancy are the more active sites for deoxygenation than the bare Pt sites. [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]

Selective hydrodeoxygenation (HDO) of biomass lignin derived phenolics to aromatics is an attractive approach for utilization of biomass lignin, since minimal H 2 is consumed. Herein, bimetallic Ni-Cu/SiO 2 catalysts with varying Cu/Ni molar ratios were synthesized by a modified homogeneous precipitation-deposition method and tested for HDO of m-cresol at 350 °C and atmospheric pressure. Characterizations indicate the formation of Ni-Cu alloys with an enrichment of Cu on the surface, which breaks the contiguous surface Ni atoms and reduces the Ni ensemble size. Despite bare Ni/SiO 2 favors both C-C hydrogenolysis to CH 4 and direct deoxygenation (DDO) to toluene, Ni-Cu/SiO 2 makes DDO the dominant pathway (yield of 7.6% at conversion of 9.6% and yield of 90.4% at conversion of 95.2%) while suppresses the C-C hydrogenolysis to a very minor one. Ni-Cu/SiO 2 with an optimal Cu/Ni molar ratio of 0.5 produced a turnover frequency (TOF) of 3.09 min−1 for m-cresol conversion. The TOF for toluene formation on Ni-Cu/SiO 2 increases by ∼3 times to 2.24 min−1 from that on bare Ni/SiO 2 whereas the TOF of CH 4 formation is reduced by ∼10 times to 0.16 min−1. This study demonstrates that dilution of Ni by an inert metal such as Cu can effectively enhance DDO through inhibiting C-C hydrogenolysis during HDO of phenolics at atmospheric pressure. [Display omitted] • Hydrodeoxygenation of m-cresol was investigated at 350 °C and atmospheric pressure. • The formation Ni-Cu alloy reduces the ensemble size of Ni. • The optimal Cu/Ni molar ratio is 0.5. • C-C hydrogenolysis is inhibited on Ni-Cu/SiO 2 catalyst. • Direct deoxygenation is the dominant pathway on Ni-Cu/SiO 2. [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] • Ni properties can be modified by tuning the SMSI with anatase and rutile TiO 2. • The overall HDO activity is significantly reduced due to excess SMSI on Ni/a-TiO 2. • Moderate SMSI occurs on Ni/r-TiO 2 only after reduction at 650 °C. • Ni/r-TiO 2 becomes selective for DDO toward toluene with inhibited C-C hydrogenolysis. • TOF of DDO on Ni/r-TiO 2 is improved by >10 times due to moderate SMSI. The relatively cheap and abundant Ni as a catalyst for hydrodeoxygenation (HDO) of biomass lignin-derived phenolics at 350 °C and atmospheric pressure suffers from unfavorable C-C hydrogenolysis toward CH 4 with a lower direct deoxygenation (DDO) activity. Herein, we demonstrate that the activity and selectively of Ni for HDO of m-cresol can be modified through the differences of strong metal-support interaction (SMSI) on anatase and rutile TiO 2. Characterizations showed that the presence of SMSI depended strongly on the crystal phase of TiO 2. The SMSI dominates on Ni/a-TiO 2 after reduction at 350 °C, resulting in Ni particles partially covered by a TiO x overlayer, and this overlayer became sufficiently thick at 650 °C, causing a significant reduction of CO chemisorption. Although the catalyst became selective for DDO to toluene, the overall HDO activity was significantly reduced because of excessive SMSI. In contrast, the Ni/r-TiO 2 catalyst reduced at 350 °C exhibited little SMSI and was active for C-C hydrogenolysis like a bare Ni catalyst. Increasing reduction temperature to 650 °C, the Ni/r-TiO 2 catalyst showed moderate SMSI and became selective to toluene through DDO while completely inhibited CH 4 formation. The toluene and total aromatics yields were 84.8 and 92.2%, respectively, at full conversion. More importantly, the turnover frequency for DDO (2.43 min−1) on the Ni/r-TiO 2 catalyst reduced at 650 °C was ∼40 and ∼14 times higher than that of Ni on rutile and anatase, respectively, reduced at 350 °C. This study provides an example of "Goldilocks principle" in catalysis, i.e., the best performing catalyst offers a balanced SMSI! [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]

• Bimetallic Ni-Re promotes deoxygenation while inhibits C C hydrogenolysis to CH 4. • CH 4 is mainly from C C hydrogenolysis of molecules with phenyl ring. • Ni-Re keeps high deoxygenation performance at higher reaction temperatures. • Coke is the major reason of deactivation on both catalysts. The reaction network of hydrodeoxygenation of m-cresol was investigated over Ni/SiO 2 and Ni-Re/SiO 2 catalysts at 300 °C and 1 atm H 2. m-Cresol conversion proceeds through three major primary pathways: phenyl ring hydrogenation to 3-methylcyclohexanone and 3-methylcyclohexanol, C C hydrogenolysis to CH 4 and phenol, and deoxygenation to toluene. Re addition promotes dehydrogenation of the initially formed methylcyclohexanone and methylcyclohexanol to surface intermediates followed by deoxygenation toward formation of toluene. C C hydrogenolysis happens on unsaturated compounds with phenyl ring, instead of saturated compounds, since dehydrogenation is requested prior to C C cleavage. The turnover frequency (TOF) for CH 4 formation follows the order of m-cresol < toluene << benzene, indicating that C C hydrogenolysis is accelerated after deoxygenation and/or demethylation. Increasing reaction temperature promotes both deoxygenation and hydrogenolysis. The toluene selectivity keeps low even at higher temperature of 340 °C on monometallic Ni catalyst due to successive C C hydrogenolysis to CH 4. Re addition not only promotes deoxygenation to toluene by providing active Ni-Re neighboring sites, but also inhibits the aromatics hydrogenolysis to CH 4 , resulting in high toluene selectivity on bimetallic catalyst. Both catalysts show a similar deactivation trend and coke is speculated to be the major reason for deactivation. [ABSTRACT FROM AUTHOR]

Ni–Re/SiO 2 bimetallic catalysts were prepared using a co-impregnation method and tested in vapor phase hydrodeoxygenation of m-cresol at 300 °C and 1 atm H 2 . In contrast to the use of unselective monometallic Ni/SiO 2 for catalyzing deoxygenation, hydrogenation, and C C hydrogenolysis reactions, bimetallic 5%Ni–2.5%Re/SiO 2 improved the intrinsic reaction rate of the hydrodeoxygenation reaction by a factor of 6, with the turnover frequency for selective deoxygenation to toluene increased by four times, while that for C C hydrogenolysis to methane was reduced by one-half. Characterization results from X-ray diffraction, Raman, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy of CO adsorption, H 2 temperature-programmed reduction, and CO chemisorption indicate that adding Re increased Ni dispersion and resulted in Ni–Re surface alloy formation after reduction. The presence of Re in the surface alloy breaks the continuous Ni surface into smaller ensembles (geometric effect) and reduces the d -band electron density of Ni (electronic effect). Results from density functional theory calculations indicate that the Ni–Re neighboring site is the active site for breaking the C O bond by adsorbing the O atom on Re and the phenyl ring on the neighboring Ni atoms, which facilitates deoxygenation to toluene. The reduced Ni ensemble size inhibits the hydrogenolysis of the C C bond by destabilizing the transition state, whereas the reduction of the electronic density in d states of Ni weakens the adsorption of the phenyl ring, and both contribute to the greatly reduced methane production from successive C C hydrogenolysis. [ABSTRACT FROM AUTHOR]