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Plastics, fibers and rubber are three mainstream synthetic materials that are essential to our daily lives and contribute significantly to the quality of our lives. The production of the monomers of these synthetic polymers usually involves oxidation or ammoximation reactions of olefins and analogues. However, the utilization of C, O and N atoms in current industrial processes is <80%, which represents the most environmentally polluting processes for the production of basic chemicals. Through innovation and integration of catalytic materials, new reaction pathways, and reaction engineering, the Research Institute of Petroleum Processing, Sinopec Co. Ltd. (RIPP) and its collaborators have developed unique H2O2-centered oxidation/ammoximation technologies for olefins and analogues, which has resulted in a ¥500 billion emerging industry and driven trillions of ¥s' worth of downstream industries. The chemical and engineering bases of the production technologies mainly involve the integration of slurry-bed reactors and microsphere catalysts to enhance H2O2 production, H2O2 propylene/chloropropylene epoxidation for the production of propylene oxide/epichlorohydrin, and integration of H2O2 cyclohexanone ammoximation and membrane separation to innovate the caprolactam production process. This review briefly summarizes the whole process from the acquisition of scientific knowledge to the formation of an industrial production technology by RIPP. Moreover, the scientific frontiers of H2O2 production and related oxidation/ammoximation processes of olefins and analogues are reviewed, and new technological growth points are envisaged, with the aim of maintaining China's standing as a leader in the development of the science and technologies of H2O2 production and utilization. [ABSTRACT FROM AUTHOR]

The textural and structural properties of a skeletal Ni catalyst prepared by alkali leaching of aluminum from the rapidly quenched Ni50Al50 alloy have been investigated by elemental analysis (ICP-AES), nitrogen physisorption, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and H2 thermal desorption techniques. As compared to Raney Ni, such a skeletal catalyst has a residual Ni2Al3 phase, lower surface area, higher average pore diameter and porosity, larger mean crystallite size, and unit-cell parameter. These differences are attributable to the metastable character of the pristine rapidly quenched alloy and their relationship with the catalytic behavior is discussed and correlated. [Copyright &y& Elsevier]

The caustic leaching kinetics of the rapidly quenched Ni–Al alloys has been studied by measuring the evolution of H2 during the leaching process. The effects of various parameters, such as the composition and the particle size of the Ni–Al alloys, the concentration of the NaOH aqueous solution, and the temperature have been systematically investigated. It is found that the leaching process of the rapidly quenched Ni–Al alloys can be well fitted by a reaction-controlled shrinking core model, which is attributed to the uniform microstructure of the alloys prepared by the rapid quenching technique. [Copyright &y& Elsevier]

By utilizing greenhouse gas CO2 and renewable energy-sourced H2 to produce methanol, the "methanol economy" can replace fossil fuels and H2 as the energy storage medium, which not only reduces CO2 emissions, but also mitigates the energy shortage issue. However, the traditional Cu-based catalysts for CO2-to-methanol conversion suffer from low activity at low temperature and high vulnerability to sintering and deactivation. In this contribution, rapidly quenched skeletal Cu catalysts (RQ Cu) are prepared by leaching the RQ Cu–Al alloy with NaOH aqueous solutions of different concentrations. It is found that high NaOH concentration of 10 wt% favors the preparation of the RQ Cu-10 catalyst with higher porosity, lower residual Al content, and larger active Cu surface area (SCu) than the RQ Cu-3 catalyst leached with 3 wt% of NaOH solution. However, in aqueous-phase CO2 hydrogenation at 473 K and 4.0 MPa, the CO2 conversion over the RQ Cu-3 catalyst is more than two times greater than that over the RQ Cu-10 catalyst, and the selectivity and productivity of methanol are 1.20 and 2.69 times of the corresponding values over the RQ Cu-10 catalyst. At 5.0 MPa, the selectivity and productivity of methanol are further boosted to 97.9% and 1.329 mmol gCu–1 h–1 on the RQ Cu-3 catalyst. It is identified that the SCu of the RQ Cu-3 catalyst is well preserved after reaction, while dramatic growth of the Cu crystallites occurs for the RQ Cu-10 catalyst. The better catalytic performance and stability of the RQ Cu-3 catalyst are tentatively attributed to the presence of more residual Al species by using NaOH solution with lower concentration for Al leaching, which acts as the dispersant for the Cu crystallites during the reaction. [ABSTRACT FROM AUTHOR]

The exfoliation of bulk C3N4 (BCN) into ultrathin layered structure is an effective strategy to boost photocatalytic efficiency by exposing interior active sites and accelerating charge separation and transportation. Herein, we report a novel nitrate anion intercalation‐decomposition (NID) strategy that is effective in peeling off BCN into few‐layer C3N4 (fl‐CN) with tailored thickness down to bi‐layer. This strategy only involves hydrothermal treatment of BCN in diluted HNO3 aqueous solution, followed by pyrolysis at various temperatures. The decomposition of the nitrate anions not only exfoliates BCN and changes the band structure, but also incorporates oxygen species onto fl‐CN, which is conducive to O2 adsorption and hence relevant chemical processes. In photocatalytic O2 reduction under visible light irradiation, the H2O2 production rate over the optimal fl‐CN‐530 catalyst is 952 μmol g−1 h−1, which is 8.8 times that over BCN. More importantly, under full arc irradiation and in the absence of hole scavenger, CH4 can be photocatalytically oxidized by on‐site formed H2O2 and active oxygen species to generate value‐added C1 oxygenates with high selectivity of 99.2 % and record‐high production rate of 1893 μmol g−1 h−1 among the metal‐free C3N4‐based photocatalysts. [ABSTRACT FROM AUTHOR]

The exfoliation of bulk C3N4 (BCN) into ultrathin layered structure is an effective strategy to boost photocatalytic efficiency by exposing interior active sites and accelerating charge separation and transportation. Herein, we report a novel nitrate anion intercalation‐decomposition (NID) strategy that is effective in peeling off BCN into few‐layer C3N4 (fl‐CN) with tailored thickness down to bi‐layer. This strategy only involves hydrothermal treatment of BCN in diluted HNO3 aqueous solution, followed by pyrolysis at various temperatures. The decomposition of the nitrate anions not only exfoliates BCN and changes the band structure, but also incorporates oxygen species onto fl‐CN, which is conducive to O2 adsorption and hence relevant chemical processes. In photocatalytic O2 reduction under visible light irradiation, the H2O2 production rate over the optimal fl‐CN‐530 catalyst is 952 μmol g−1 h−1, which is 8.8 times that over BCN. More importantly, under full arc irradiation and in the absence of hole scavenger, CH4 can be photocatalytically oxidized by on‐site formed H2O2 and active oxygen species to generate value‐added C1 oxygenates with high selectivity of 99.2 % and record‐high production rate of 1893 μmol g−1 h−1 among the metal‐free C3N4‐based photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Polymeric carbon nitride (PCN) is an important metal-free photocatalyst for visible light-driven hydrogen peroxide (H 2 O 2) production from O 2 reduction. Herein, we synthesized the DPCN catalysts possessing nitrogen defects by one-step thermal polymerization of urea in N 2 stream. As compared to the PCN conventionally synthesized in static air, X-ray photoelectrons spectroscopy (XPS) characterization disclosed that there are more pyridinic N defects in the DPCN catalysts, which is attributed to the removal of a proportion of NH 3 released from urea pyrolysis by flowing N 2. UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Mott–Schottky, steady-state and time-resolved photoluminescence (PL), and electrochemical impedance spectroscopy (EIS) characterizations revealed that the introduction of the nitrogen defects narrows down the band gap, improves the density of the photoexcited charge carriers, prolongs the lifetime of the charge carriers, and enhances the charge transfer efficiency. In visible light-driven photocatalytic O 2 reduction to H 2 O 2 , the optimal DPCN catalyst afforded an activity of 4.35 times that of the PCN catalyst and a H 2 O 2 concentration of 2.83 mmol L–1 after 10 h of visible light irradiation. This one-step thermal polymerization approach is valid when replacing N 2 stream with Ar and He streams. [ABSTRACT FROM AUTHOR]

The effect of K on the distribution and productivity of the olefins in CO2 hydrogenation over the single‐walled carbon nanotubes (SWNTs) supported Fe catalysts was systematically investigated. The promotion of K not only effectively suppressed the formation of the undesired light paraffins (CH4 and C20−C40), but also significantly affected the distribution and the productivity of the olefins. The highest selectivity and productivity of light olefins (C2=−C4=) of 27 % and 16 μmolCO2 gFe−1 s−1, respectively, were obtained at 7 wt% of K, while the highest selectivity and productivity of heavy olefins (C5+=) of 40 % and 27 μmolCO2 gFe−1 s−1, respectively, were obtained at 3 wt% of K under the same reaction conditions. At 3 wt% of K and above, the overall selectivity to the olefins (inclusive of light olefins and heavy olefins) remained at as high as ca. 60 % at high CO2 conversion of ca. 50 %. Comprehensive characterizations revealed that the K promoter enhanced the basicity of the catalyst, which facilitates the formation of χ‐Fe5C2, the key active phase for CO2 hydrogenation. A good linear relationship is established between the surface basicity and the content of χ‐Fe5C2. Moreover, the K promoter weakened the adsorption of the olefins, which inhibited the secondary hydrogenation of the olefins, thus improving the selectivity to the olefins. This work demonstrates that K is a highly promising promoter for the tailoring of the types of the olefinic products in CO2 hydrogenation. [ABSTRACT FROM AUTHOR]

Abstract: Attempts have been made to prepare alumina nanofibers by hydrolyzing aluminum nitrate in the presence of hexamethylenetetramine (HMTA) followed by the supercritical fluid drying (SCFD) process. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen physisorption. The results show that δ-Al2O3 nanofibers with diameter of 2 nm, length of 50 nm and with BET surface areas of 412.6 m2 g−1 were successfully synthesized. The thermal evolution of the fibers and the role of hexamethylenetetramine were also briefly discussed. [Copyright &y& Elsevier]

Abstract: A series of Sn-containing mesoporous SBA-15 molecular sieves were synthesized and used as supports for RuB catalysts. Effects of Sn doping on the structure of the SBA-15 and on properties and catalytic performance of the RuB/Sn-SBA-15 catalyst in ethyl lactate hydrogenation were studied. The samples were characterized by inductively coupled plasma–atomic emission spectroscopy (ICP–AES), N2 physisorption, powder X-ray diffraction (XRD), diffuse reflectance UV–vis spectroscopy (DRUVS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and catalytic tests. The results showed that Sn-containing SBA-15 supports prepared by direct hydrothermal synthesis method maintained the characteristic structure of SBA-15 with Sn species highly dispersed in the support when Si/Sn nominal ratio was above 30. The RuB catalysts supported on the Sn-containing SBA-15 prepared by the direct hydrothermal synthesis method showed higher dispersion and better catalytic performance than corresponding one prepared by the impregnation method. The best catalytic performance was achieved over catalyst with Si/Sn nominal ratio of 30. [Copyright &y& Elsevier]

Abstract: Binary CoB and ternary CoFeB amorphous alloy catalysts with different Fe contents were prepared by the chemical reduction method. In liquid-phase hydrogenation of crotonaldehyde, incorporation of Fe into the CoB catalyst reduced the overall activity while effectively improving the selectivity and yield to crotyl alcohol. On the optimum CoFeB-3 catalyst with a nominal Fe/(Co+Fe) molar ratio of 0.6, the initial selectivity amounted to 71%, and the yield of crotyl alcohol reached 63%. It is found that the selectivity enhancement was due to the lower decrement in the intrinsic formation rate of crotyl alcohol compared with that of butanal, not to the increment in the activation of the Cased on the characterizations, including X-ray photoelectron spectroscopy and X-ray absorption spectroscopy, and previous findings, the enhanced selectivity from Fe modification was tentatively attributed to an ensemble size effect. [Copyright &y& Elsevier]

Abstract: Effect of promoters (Co, Fe, Sn, Zn) on structures, properties and catalytic performance of RuB/γ-Al2O3 catalyst was studied using in situ XRD, TEM, H2-TPD, XPS and liquid-phase hydrogenation of ethyl lactate to 1,2-propanediol (PDO). It was found that incorporation of Sn or Fe improved the dispersion and thermal stability of RuB. The electron density of Ru and the strength and capacity of H2 adsorption on the RuB catalyst were also enhanced by the incorporation of Sn or Fe. The incorporation of Co or Zn led to a significant decrease in H2 adsorption capacity of the RuB catalyst. Both ethyl lactate conversion and selectivity to 1,2-PDO increased with the incorporation of Sn or Fe. The ethyl lactate conversion decreased sharply with the incorporation of Zn or Co accompanied by an increase in selectivity to 1,2-PDO and lactic acid. The effect of promoters on reaction behavior was discussed on the basis of the characterizations. [Copyright &y& Elsevier]

Amorphous Ru-B supported on γ-Al2O3 was prepared by a novel reductant impregnation method for the hydrogenation of ethyl lactate to 1,2-propanediol (PDO). The effects of tin on composition, physicochemical properties, thermal stability and reaction behavior of Ru-B/γ-Al2O3 catalyst were studied by using in situ XRD, TEM, H2-TPD, XPS and liquid phase hydrogenation of ethyl lactate. The Ru-B/γ-Al2O3 catalyst prepared by reductant impregnation showed good activity for hydrogenation of ethyl lactate. Addition of suitable amounts of tin (Sn/Ru atomic ratio of 7%) significantly increased the ethyl lactate conversion and the selectivity to 1,2-PDO; a selectivity to 1,2-PDO of 91.5% was obtained at ethyl lactate conversion of 90.7% under mild reaction conditions. The characterizations showed that addition of tin improved the dispersion and thermal stability of Ru-B significantly. The B/Ru ratio of the catalyst, the electron density of Ru, and the strength of hydrogen adsorption of the catalyst increased with increase of tin content over the range studied. [Copyright &y& Elsevier]

The 2Re/CuZnZr catalyst was prepared by loading Re on top of the CuZnZr catalyst. The addition of Re improved active metal dispersion, allowing ZnO to perform its spacer function fully and reducing the size and number of Cu species aggregations. In the meantime, Re enhanced the conversion of the maleic anhydride hydrogenation intermediate γ-butyrolactone to 1,4-butanediol. Re significantly improved the catalyst performance, achieving an 85 % yield of 1,4-butanediol at 190 °C and 6 MPa. [Display omitted] • 1,4-Butanediol was prepared from maleic anhydride by one-step gas-phase hydrogenation in a continuous fixed-bed reactor. • The introduction of Re additives not only reducesd the grain size of copper but also promoted the better functioning of ZnO as a spacer. • Re acted as a promoter to facilitate the further conversion of the maleic anhydride hydrogenation intermediate γ-butyrolactone to 1,4-butanediol. • The 2Re/CuZnZr catalyst achieved 85% yield of 1,4-butanediol at 190 °C and 6 MPa and maintained stable catalytic performance for 200 h. Producing 1,4-butanediol with selective hydrogenation of maleic anhydride has significant financial benefits. This work reported a "green" one-step method for preparing 1,4-butanediol from maleic anhydride in a gas-phase fixed bed continuous flow reactor over an efficient 2Re/CuZnZr catalyst for the first time. In this paper, CuZnZr composite metal oxides were synthesized using the co-precipitation technique, followed by impregnation of Re to produce xRe/CuZnZr catalysts. The study aimed to investigate the effects of including Re on the catalyst's structure and performance. The results obtained from the characterization indicate that the presence of Re in the system restricts the growth of Cu0 grains. In addition, the inclusion of Re facilitated the utilization of ZnO as an effective spacer, reducing the size and quantity of Cu species agglomerates and enhancing active metal dispersion. This phenomenon may be attributed to being the primary factor responsible for the observed enhancement in the activity of the maleic anhydride hydrogenation reaction. Meanwhile, Re facilitated the transformation of γ -butyrolactone, an intermediate resulting from the hydrogenation of maleic anhydride into 1,4-butanediol. The 2Re/CuZnZr catalyst exhibited favorable catalytic activity under the conditions of 190 °C and 6 MPa, resulting in the complete conversion of maleic anhydride and a selectivity of 85 % towards 1,4-butanediol. The catalyst showed consistent catalytic performance throughout the 200 h. The finding about the impact of Re promoter on Cu-based catalysts has the potential to yield a highly efficient catalytic system for alcohol generation. [ABSTRACT FROM AUTHOR]

A novel process based on cyclohexene esterification–hydrogenation for the production of cyclohexanol, the key intermediate in the production of ε-caprolactam, was devised and validated for the first time. In this process, cyclohexene obtained from the partial hydrogenation of benzene is esterified with acetic acid to cyclohexyl acetate, followed by hydrogenation to cyclohexanol. The experimentally determined equilibrium conversion of cyclohexene for cyclohexene esterification at the stoichiometric ratio is always ≥68% in the temperature range of 333–373 K over the commercial Amberlyst 15 catalyst, which is substantially higher than that of cyclohexene hydration. The apparent activation energy (Ea) for the esterification of cyclohexene with acetic acid is 60.0 kJ mol−1, which is lower than that of cyclohexene hydration. In the hydrogenation of cyclohexyl acetate to cyclohexanol, high conversion of 99.5% and high selectivity of 99.7% are obtained on the La-promoted Cu/ZnO/SiO2 catalyst prepared by the co-precipitation method. This process shows both a high overall atom economy of 99.4% comparable to that of the cyclohexene hydration process and a much higher catalytic efficiency than the phenol hydrogenation process. On the basis of the above fundamental works, a pilot-scale demonstration unit with a capacity of 8000 tonnes per annum was developed and operated smoothly for more than 1000 h with no indication of deactivation. [ABSTRACT FROM AUTHOR]

Highly effective photocatalysts for the hydrogen‐evolution reaction were developed by conferring the linkers of NH2‐MIL‐125(Ti), a metal–organic framework (MOF) constructed from TiOx clusters and 2‐aminoterephthalic acid (linkers), with active copper centers. This design enables effective transfer of electrons from the linkers to the transient Cu2+/Cu+ centers, leading to 7000‐fold and 27‐fold increase of carrier density and lifetime of photogenerated charges, respectively, as well as high‐rate production of H2 under visible‐light irradiation. This work provides a novel design of a photocatalyst for hydrogen evolution using non‐noble Cu2+/Cu+ as co‐catalysts. [ABSTRACT FROM AUTHOR]

Highly effective photocatalysts for the hydrogen‐evolution reaction were developed by conferring the linkers of NH2‐MIL‐125(Ti), a metal–organic framework (MOF) constructed from TiOx clusters and 2‐aminoterephthalic acid (linkers), with active copper centers. This design enables effective transfer of electrons from the linkers to the transient Cu2+/Cu+ centers, leading to 7000‐fold and 27‐fold increase of carrier density and lifetime of photogenerated charges, respectively, as well as high‐rate production of H2 under visible‐light irradiation. This work provides a novel design of a photocatalyst for hydrogen evolution using non‐noble Cu2+/Cu+ as co‐catalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • K and/or P-doped carbon nitrides were synthesized from urea and different salts. • They were evaluated in visible light photocatalytic production of H 2 O 2 from O 2. • The K 2 HPO 4 /GCN (CNKP-10) catalyst produced the highest concentration of H 2 O 2. • K and P were identified to be incorporated into the framework of CNKP-10. • They narrowed down the band gap and enhanced the utility of the charge carriers. Abstract Photocatalytic production of hydrogen peroxide (H 2 O 2) from two-electron reduction of molecular oxygen over semiconductor catalysts under visible light irradiation represents a clean and sustainable strategy to transform solar energy to chemicals. Here we synthesized a series of potassium and/or phosphorus-doped carbon nitride photocatalysts by one-pot thermal polymerization of urea and different sylvites and phosphates. Among them, the K 2 HPO 4 /GCN (CNKP-10) catalyst exhibited the best visible light photocatalytic activity for H 2 O 2 production from molecular oxygen. After 10 h visible light (λ ≥ 420 nm) irradiation, the concentration of H 2 O 2 exceeded 5 mmol l–1 on this catalyst, which is more than five folds of that on the catalyst synthesized by thermal polymerization of urea only (GCN). A combination of bulk and surface characterization techniques confirmed the incorporation of potassium and phosphorus into the framework of GCN, which narrowed down the band gap, raised the conduction band, and enhanced the generation, transmission, and lifetime of the photogenerated charge carriers, thus promoting the visible light photocatalytic production of H 2 O 2 from molecular oxygen. [ABSTRACT FROM AUTHOR]

• Honeycomb-structured graphene (HSG) was used to support the K-MgFe catalysts. • Unprecedentedly high activity and productivity of lower olefins were obtained in FTO. • The synergetic effect of Mg and K enhanced the adsorption and dissociation of CO. • The catalyst also showed better durability than typical FTO catalysts. • HSG enabled fast heat dissipation and confined the sintering of the active phase. Three-dimensional (3D) honeycomb-like structured graphene (HSG)-supported ternary K-promoted magnesium ferrite catalysts (K-MgFe/HSG) are prepared and evaluated in Fischer–Tropsch synthesis to the lower olefins (FTO). The catalysts bear interconnected mesoporous-macroporous framework of graphene nanosheets decorated with homogeneously sized magnesium ferrite nanoparticles (NPs). Under typical FTO reaction conditions, the composition-optimized 1K-MgFe/HSG catalyst affords a reduced CO 2 selectivity of 40.4%, an excellent weight specific activity to hydrocarbons of 1825 μmol CO g Fe −1 s−1, and an appreciable selectivity to the lower olefins (C 2 C 4 olefins) of 57.8%, thus giving rise to a record high productivity of the lower olefins of 1055 μmol CO g Fe −1 s−1. The excellent catalytic efficiency is tentatively attributed to the synergetic effect of Mg and K on adsorption and dissociation of CO. The catalyst also exhibits better durability than previously reported iron-based FTO catalysts, without significant changes in the catalytic performance and the size of the iron carbide NPs after 120 h on stream, highlighting the crucial role of the 3D porous HSG support in restricting the agglomeration of the active phase during the challenging high-temperature and exothermic FTO reaction. [ABSTRACT FROM AUTHOR]

To photocatalytically reduce O 2 to H 2 O 2 over polymeric carbon nitride (PCN) in high efficiency is essential for practical application but remains a considerable challenge. Herein, we synthesized a K, S, and O co-doped PCN (akut -CN) via one-pot polymerization of urea and thiourea in the presence of KCl and NaOH, which afforded an unprecedentedly high H 2 O 2 production rate of 4.46 mM h–1 under visible light irradiation, about 210 times that over the un-doped PCN. The heteroatom doping and the incorporation of the cyano and hydroxyl groups into akut -CN are identified to enhance light absorption, accelerate the separation and transfer of the photogenerated charges, and improve the surface electronegativity and the O 2 adsorption capacity and strength, which collaboratively boosted the reaction kinetics. This work highlights the great potential of the elaborately decorated PCN in photocatalytic O 2 reduction to H 2 O 2 and paves the way to the decentralized production and application of H 2 O 2. [Display omitted] ● One-pot polymerization of urea and thiourea to akut -CN with KCl and NaOH co-existing. ● Its H 2 O 2 production rate under visible light is 210 times that on the un-doped PCN. ● Heteroatoms are incorporated and cyano and hydroxyl groups are grafted on akut -CN. ● These modifications accelerate the separation and transfer of the charge carriers. ● Surface electronegativity and O 2 adsorption capacity and strength are also enhanced. [ABSTRACT FROM AUTHOR]

Ceria‐zirconia solid solutions with tunable surface oxygen vacancy have been used in the direct conversion of syngas into aromatics after coupling with ZSM‐5 zeolite. A high selectivity of 83.1 % to aromatics has been achieved from syngas with low H2/CO ratio over Ce0.2Zr0.8O2/ZSM‐5 bifunctional catalyst. The surface oxygen vacancy of Ce0.2Zr0.8O2 is supposed to facilitate the formation of oxygenates which act as intermediates for C−C coupling and aromatization on ZSM‐5, and thus contribute to the well kinetic matching between C−O activation and C−C coupling over these two components of catalyst. The ceria‐zirconia with abundant surface oxygen vacancies and enhanced lattice oxygen mobility intimately mixed with ZSM‐5 zeolite with moderate acidity and crystal size play an important role in the catalytic performance. O‐pen vacancy: By tuning the surface oxygen vacancy of ceria‐zirconia solid solutions, a well kinetic matching between C−O activation and C−C coupling can be achieved, and syngas with low H2/CO ratio is directly converted into aromatics with a high selectivity over a ceria‐zirconia/HZSM‐5 bifunctional catalyst. [ABSTRACT FROM AUTHOR]

Abstract: A strategy based on galvanic replacement between metallic Zn and Ru salt followed by acid treatment was developed to fabricate supported Ru–Zn/ZrO2 nanocomposite catalysts with controlled contents of Zn for the benzene partial hydrogenation to cyclohexene. The catalysts were systematically characterized by techniques such as extended X‐ray absorption fine structure, X‐ray photoelectron spectroscopy, and transmission electron microscopy. In benzene partial hydrogenation, with the decrease in the content of Zn, the turnover frequency (TOF) of benzene increased monotonically, whereas the selectivity to cyclohexene evolved in a volcanic trend, passing through a maximum of 72 %. Kinetic analysis indicated that with the depletion of Zn, the rate constant for benzene hydrogenation to cyclohexene and that for cyclohexene hydrogenation to cyclohexane increased simultaneously, but the extents of the increments were at variance. It was identified that the ratios of the rate constants were in parallel with the change in the selectivity to cyclohexene, which is attributed to the electronic effect of metallic Zn that modifies the interactions of Ru with benzene and cyclohexene. [ABSTRACT FROM AUTHOR]

The effects of the crystal phases of ZrO 2 in the Pt–WO x /ZrO 2 catalysts on glycerol hydrogenolysis to 1,3-propanediol (1,3-PDO) were comparatively studied. Pt and WO x were sequentially deposited on monoclinic ( m -ZrO 2 ) and tetragonal ( t -ZrO 2 ) ZrO 2 supports with similar surface areas by the wetness impregnation method. On both catalysts, sub-nanosized Pt particles were well dispersed on the supports, and the WO x species were mainly in the monomeric state and partly covered the Pt particles. The Pt–WO x / m -ZrO 2 catalyst had larger Pt particle size and less Brønsted acid sites than the Pt–WO x / t -ZrO 2 catalyst. In glycerol hydrogenolysis, the glycerol conversion and 1,3-PDO selectivity on the Pt–WO x / m -ZrO 2 catalyst were less than one half of those on the Pt–WO x / t -ZrO 2 catalyst. The Pt–WO x / t -ZrO 2 catalyst exhibited a high 1,3-PDO yield of 49.4%, an excellent 1,3-PDO productivity of 5.10 g g Pt −1 h −1 , and good recyclability. The superiority of the Pt–WO x / t -ZrO 2 catalyst in glycerol hydrogenolysis to 1,3-PDO is attributed to the better synergy between smaller Pt particles in affording hydrogen atoms and more Brønsted acid sites in converting glycerol to the intermediate suitable for the formation of 1,3-PDO. [ABSTRACT FROM AUTHOR]

It has been documented that W-modified Pt catalysts with relatively high tungsten contents are effective for the catalytic transformation of biodiesel-derived glycerol to 1,3-propanediol (1,3-PDO). Herein, we report a new finding that Pt/W–SBA-15 catalysts with extremely low W/Si atomic ratios (≤1/80) exhibit excellent catalytic performance in the hydrogenolysis of glycerol to 1,3-PDO. In particular, a Pt/W–SBA-15 catalyst with the W/Si ratio of as low as 1/640 (Pt/W–SBA-15(1/640)) gave rise to the highest 1,3-PDO selectivity of 70.8% at a high glycerol conversion of 86.8% and thus afforded the highest yield of 1,3-PDO of 61.5%. A combination of characterization techniques evidenced that tungsten was homogeneously incorporated into SBA-15 in the form of isolated tetragonal WO4 and only displayed Lewis acidity. The particle size of Pt evolved in a reverse volcanic curve with the W/Si ratio, with the smallest size being observed for Pt/W–SBA-15(1/640). Control experiments indicated strong synergy between Pt nanoparticles (NPs) and WO4 in the hydrogenolysis of glycerol. A probe reaction suggested that Brønsted acid sites were generated in situ on the Pt/W–SBA-15 catalysts in a H2 atmosphere by the reaction between WO4 and spillover H atoms from the Pt NPs. It is plausible that the hydrided WO4 functioned as a highly selective active centre in the hydrogenolysis of glycerol to 1,3-PDO, whereas the Pt NPs played the role of a reservoir of spillover H atoms. Thus, a good match between the isolated WO4 and the small Pt NPs was responsible for the superior catalytic performance of Pt/W–SBA-15(1/640). [ABSTRACT FROM AUTHOR]

One-step conversion of syngas (a mixture of CO and H 2 ) to C 2 –C 4 light olefins (FTO) has attracted enormous attention in recent years because of the great improvement in process simplicity. However, on the documented FTO catalysts, the carbon efficiency is quite low (CO 2 selectivity as high as ∼50%) and hence the green-house gas emission is high. Herein, we report about the design of novel Mg and K dual-decorated iron catalysts supported on reduced graphene oxide (rGO) to address this issue. We identified that on a dual-decorated FeMgK2/rGO catalyst with the optimized amounts of Mg and K, not only the selectivity to light olefins amounted to 65.0%, but also the selectivity to CO 2 was appreciably cut down to 40.8%. On the basis of systematic characterizations, we propose that the suppression of the formation of magnetite during FTO because of Mg decoration effectively inhibited the water–gas shift (WGS) reaction, one of the main reaction pathways for CO 2 generation. Furthermore, successive decoration with only 0.50–2.0 wt% of K drastically boosted the iron time yield to hydrocarbons (FTY) to 1060–1706 μmol g Fe −1 s −1 and the iron time yield to light olefins (FTY ole ) to 521–1003 μmol g Fe −1 s −1 . The new strategy of alkaline-earth metal-alkali metal dual decoration for the design of the iron-based catalysts may propel the development of a practical FTO process featuring high productivity and low CO 2 emission. [ABSTRACT FROM AUTHOR]

It has long been known that inorganic additives enhance the product selectivity in organic catalytic transformations. However, the potential of this facile approach in the industrially significant Fischer-Tropsch synthesis (FTS) has not been well explored. Herein, after examining the promotion effects of a diversified range of metal sulfates on product distribution over an active and recyclable Ru/P25 catalyst in the aqueous-phase, low-temperature FTS, we show that whereas enhancing the selectivity to diesel is a general feature for most metal sulfates, nickel sulfate is unique in enhancing the selectivity to gasoline. Moreover, this strategy enables the reversible boosting of the selectivity to gasoline or diesel with ease and thus provides access to a FTS process with unprecedented versatility. Probe reactions and theoretical studies point to the scenario that metal sulfates modify the reaction pathway by affecting the stability of the endogenous α-olefins, which hence alters the probability of chain growth and product distribution. [ABSTRACT FROM AUTHOR]

Low-temperature Fischer–Tropsch synthesis (LTFTS) is one of the green routes for liquid fuel production. We prepared nanocrystalline Fe–B catalysts with different particle sizes and microstructures by adjusting the addition sequence of the precursors. In situ carburization of the Fe–B catalysts at 423 K revealed that the addition sequence influenced the rate and degree of carburization pronouncedly. In LTFTS at 423 K, the Fe–B catalysts displayed similar, markedly high selectivity to liquid fuels, with ∼48% for C 5 –C 11 (gasoline fraction) and ∼31% for C 12 –C 20 (diesel fraction) hydrocarbons, and low selectivities to CO 2 and CH 4 , manifesting excellent carbon atom economy over the non-noble Fe–B catalysts. While the carburization degree did not affect the product distribution, the activities of the Fe–B catalysts evolved positively with the ε-Fe 2 C content. Moreover, a good linear relationship was established between the Fe–Fe coordination number and the ε-Fe 2 C content. [ABSTRACT FROM AUTHOR]

The ever-increasing industrial demands for nylon-6 and nylon-66 and the more and more stringent regulations on particulate emission in exhaust gases necessitate the development of an energy-efficient and environment-friendly method for saturation hydrogenation of benzene and its derivatives. However, the hydrogenation of benzene is usually conducted at a high temperature and/or under high H2 pressure, which is energy-consuming and of low environmental safety. Here, we prepared amorphous Ru–B/MIL-53(Al, Cr, and AlCr) catalysts via the wetness impregnation–chemical reduction method, which were comprehensively characterized by a combination of techniques. We found that the Ru–B/MIL-53 catalysts could catalyse the hydrogenation of benzene to cyclohexane under mild reaction conditions of 30 °C and 1.0 MPa of H2 with high efficiency, among which the Ru–B/MIL-53(AlCr) catalyst exhibited the highest turnover frequency (TOF) in terms of benzene of 6.4 s−1. Moreover, this catalyst showed good recyclability and high activities in the hydrogenation of toluene, o-xylene, m-xylene, p-xylene, and mesitylene as well, which shows promise for the application of the Ru–B/MIL-53 catalysts in the industrially important and environmentally desirable hydrogenation reaction of benzene and its derivatives. [ABSTRACT FROM AUTHOR]

Site-specific deposition of metal nanoparticles (NPs) on metal oxide surfaces is challenging but of particular importance for the development of catalytic materials with improved or new performance. We report here that Ru NPs can be directed to the rutile/anatase junction of P25 TiO 2 via a facile wetness impregnation–chemical reduction method at room temperature. In the partial hydrogenation of benzene to cyclohexene, the Ru/P25 catalyst outperformed the Ru NPs supported on phase-pure rutile and anatase as well as physically mixed Ru/rutile and Ru/anatase, both in activity and in selectivity. We identified a unique electron-deficient Ru species (Ru δ+ ) on the Ru/P25 catalyst originated from the Ru O linkages connecting the Ru NPs with the rutile/anatase junction. This interfacial Ru δ+ species gave rise to an especially tightly bonding benzene species while lowering the adsorption strength of cyclohexene, thus granting the Ru/P25 catalyst superior activity and unprecedented selectivity toward cyclohexene (initial selectivity 90%). [ABSTRACT FROM AUTHOR]

Development of a water-gas shift (WGS) catalyst durable in dynamic shutdown/startup operation is essential to enable residential applications of H2-powered fuel-cell systems but remains a conundrum for heterogeneous catalysis. We demonstrate herein that by isomorphic substitution of Zr in the lattice of CeO2 to increase the acid density of the catalyst, complemented by dosing a small amount of O2 to realistic reformate to improve the oxidizing potential, the formation of the notorious site-blocking carbonate species on the Au catalyst can be efficiently retarded. This allows the formation of a highly robust Au/Ce0.4Zr0.6O2 WGS catalyst suitable for the challenging shutdown/startup operation in realistic reformate. [ABSTRACT FROM AUTHOR]

Highlights: [•] B-doped ZrO2 (B-ZrO2) with various acid amounts (n NH3) from NH3-TPD were prepared. [•] The Ru/B-ZrO2 catalysts were evaluated in benzene hydrogenation to cyclohexene. [•] The turnover frequency of benzene was linearly proportional to n NH3. [•] B doping enabled a maximum initial selectivity (S 0) of 88% toward cyclohexene. [•] A volcanic evolution trend between S 0 and n NH3 was unveiled. [ABSTRACT FROM AUTHOR]

The new Ce-promoted skeletal Fe catalysts with different Ce contents were prepared through alkali leaching of rapidly quenched ternary FeCeAl alloys and evaluated in the gas-phase Fischer-Tropsch synthesis reaction. N2 physisorption and XRD analysis confirmed the function of Ce as a structural promoter. In the Fischer-Tropsch synthesis reaction, the incorporation of Ce markedly improved the activity and selectivity to C5+ hydrocarbons. Characterizations of the catalysts after Fischer-Tropsch synthesis confirmed the function of Ce as a chemical promoter. We also confirmed that the catalytic activity is associated with the concentrations of the surface polymeric and, to a lesser extent, atomic carbonaceous species and the C5+ selectivity correlated well with the surface concentration of Hägg carbide. We identified a linear relationship between the concentrations of the CeIII cations and Hägg carbide, which clearly substantiated the hypothesis that the chemical effect of Ce is mediated by the Fe0CeIII ensembles facilitating the formation of Hägg carbide. [ABSTRACT FROM AUTHOR]

Electrochemical production of H 2 O 2 from O 2 via the two-electron reaction pathway (2e-ORR) is a promising alternative to the energy- and organic pollutant-intensive industrial anthraquinone process. However, irrespective of numerous research efforts on catalyst design and remarkable advances made in this area, the catalysts displaying high H 2 O 2 production rate so far unexceptionally required expensive/hazardous catalyst precursors and involved tedious steps and/or harsh treating conditions. Herein, we report a slightly nitrogen-doped carbon 2e-ORR catalyst that was synthesized simply by pyrolyzing a polydopamine (PDA) coating on Vulcan XC72 carbon black (p -PDA/XC). In H 2 O 2 production via ORR in an acidic electrolyte, the catalyst showed 185 mV less overpotential than XC and remarkably high selectivity up to 96%. Highly efficient and durable H 2 O 2 production was demonstrated by the stable accumulation of H 2 O 2 to 1368 mmol g cat −1 within 8 h, translating to a H 2 O 2 production rate of 171 mmol g cat −1 h−1. A good linear relationship was identified between the H 2 O 2 partial current and the surface content of the C–O/C–N and C O species for the XC and p -PDA/XC catalysts, inferring that the C atoms in or adjacent to these species serve as the active sites for 2e-ORR to H 2 O 2. The inexpensive starting materials, facile synthetic strategy, and excellent catalytic performance of the p -PDA/XC catalyst may accelerate the establishment of an affordable, safe, and direct O 2 -to-H 2 O 2 electrochemical process. [Display omitted] • N-doped carbon catalysts were fabricated by pyrolyzing polydopamine on carbon black. • The as-synthesized p -PDA/XC catalysts were effective in electrocatalyzing O 2 to H 2 O 2. • p -PDA modification markedly reduced the overpotential and enhanced H 2 O 2 selectivity. • H 2 O 2 was stably produced within 8 h at a high rate of 171 mmol g cat −1 h−1. • H 2 O 2 partial current correlated linearly with the surface content of C–O/C–N and C=O. [ABSTRACT FROM AUTHOR]

Partial hydrogenation of benzene to cyclohexene is attractive in terms of feedstock accessibility, atomic economy, and operational simplicity. Herein, a series of Ru/ZrO2 catalysts were prepared by post-treatment of a binary Ru-Zn/ZrO2 catalyst using 5-30 wt % NaOH aqueous solutions. Alloying between Ru and Zn was evidenced for the catalyst post-treated only by water (Ru/ZrO2-0). Alkaline post-treatment removed metallic Zn, forming smaller Ru nanoparticles. Concomitantly, the hydrophilicity of the catalysts was increased and maximized on the 10 wt % NaOH-treated catalyst (Ru/ZrO2-10). In partial hydrogenation of benzene, the Ru/ZrO2-0 catalyst displayed the highest turnover frequency but the lowest initial selectivity to cyclohexene, whereas the Ru/ZrO2-10 catalyst exhibited the highest initial selectivity (86 %) and yield of cyclohexene (51 %) among the catalysts investigated. A quantitative relationship between the initial selectivity to cyclohexene and the hydrophilicity of these catalysts was identified, which rationalizes the significant impact of alkaline post-treatment on selectivity enhancement in partial hydrogenation of benzene to cyclohexene over Ru/ZrO2 catalysts. [ABSTRACT FROM AUTHOR]

Abstract: The deactivation mechanisms of the Au/CeO2 catalyst in steady-state and shutdown/start-up WGS reactions were investigated in realistic reformate at 250°C. Catalyst deactivation due to sintering was excluded. After steady-state operation, the original activity was not recovered by removing the deposited carbonate species. The influences of the component gases of realistic reformate on the activity suggest that loss of the Au–CeO2 interaction caused by the reducing H2 and CO is the main reason for catalyst deactivation. Under the shutdown/start-up condition, the catalyst suffered more drastic deactivation, although it underwent a lesser degree of reduction. A good correlation between the extent of deactivation and the amount of the carbonate species indicates that catalyst deactivation is mainly caused by enhanced formation of the carbonate species, especially through a combined effect of CO2 and H2O, during the low-temperature shutdown and start-up steps. The implications of these findings for improved applications of the Au/CeO2 catalyst in WGS are indicated. [Copyright &y& Elsevier]

Small and stable: Fe2O3 nanoparticles are homogeneously anchored onto reduced graphene oxide through the simultaneous hydrolysis of Fe(acac)3 and reduction of graphene oxide. This nanohybrid is highly resistant to sintering and retains its small particle size upon reduction at 723 K and long‐term Fischer–Tropsch synthesis at 543 K (see figure). This work validates the prospect of graphene‐related nanomaterials in challenging high‐temperature applications. [ABSTRACT FROM AUTHOR]

Fischer-Tropsch synthesis (FTS) is essential for the transformation of natural gas, coal, and biomass to clean transportation fuels and value-added chemicals. Traditionally, iron catalysts for FTS are predominantly fused iron catalysts and precipitated iron catalysts using silica as the support. Owing to an intense surge in interest in carbon materials during recent years, along with the unique properties of these materials, such as high surface area, high porosity, and ample structures, carbon-supported iron-based FTS catalysts have attracted increasing attention. In this detailed review of the progress of the Fe/C catalysts for FTS in the last three decades, particular emphasis is put on their preparation, characterization, and catalytic performance relevant to the characteristics of carbon materials. This review is intended to be a valuable resource to researchers interested in this exciting field of catalysis, as well as the foundation for those investigating applications of novel carbon materials. A brief discussion is also devoted to the challenges and opportunities regarding the future development of Fe/C FTS catalysts. [ABSTRACT FROM AUTHOR]

Ru–B/ZrO2catalysts using monoclinic,amorphous,and tetragonal ZrO2as supports were prepared and usedfor liquid-phase hydrogenation of benzene to cyclohexene. It is identifiedthat both the Lewis acid sites and the Brønsted acid sites existedon monoclinic ZrO2(ZrO2-M), while there wereonly Lewis acid sites on amorphous (ZrO2-A) and tetragonalZrO2(ZrO2-T). The amount of acid sites on ZrO2-T was the lowest. In liquid-phase hydrogenation of benzeneto cyclohexene, the Ru–B/ZrO2-T catalyst exhibitedthe highest selectivity and yield of cyclohexene, with the maximumyield of cyclohexene being 47%. These results suggest that for ZrO2-supported Ru–B catalysts, the lower was the amountof acid sites on ZrO2, the higher was the selectivity tocyclohexene. Also, the presence of the Brønsted acid sites onZrO2is probably adverse to the selectivity toward cyclohexene. [ABSTRACT FROM AUTHOR]

Abstract: Cu/ZnO catalysts with Cu loadings of 44–5 wt% were prepared by coprecipitation and evaluated in temperature-dependant and shut-down/start-up water–gas shift (WGS) reactions using realistic reformate. These catalysts had similar Cu crystallite sizes, and the metallic Cu surface area and surface Cu content increased with the Cu loading. In temperature-dependent reactions, the CO conversion on the 25wt%Cu/ZnO catalyst slightly exceeded that on 44wt%Cu/ZnO. In shut-down/start-up operation, which is imperative for mobile and residential fuel cell applications, the catalysts with Cu loadings higher than 5 wt% suffered slight activity loss. Among them, the 15wt%Cu/ZnO catalyst deactivated the most reluctantly. As a result, after three shut-down/start-up cycles the CO conversion on 15wt%Cu/ZnO, 25wt%Cu/ZnO, and 44wt%Cu/ZnO became comparable. These results demonstrate the feasibility to lower the Cu loading without degrading the WGS performance of the Cu/ZnO catalyst in shut-down/start-up operation, which will guarantee the operation safety when the catalyst will be operated unattended for domestic small-scale fuel cell applications. Unexpectedly, the CO conversion was doubled on 5wt%Cu/ZnO after one shut-down/start-up cycle, which is interpreted as the redispersion of Cu nanoparticles based on transmission electron microscopy (TEM) and temperature-programmed reduction (TPR). [Copyright &y& Elsevier]

Abstract: Au/Fe3O4 catalysts with flowerlike and particulate morphologies have been prepared by homogeneous deposition–precipitation of gold on hematite materials synthesized in different ways, followed by integrative reduction. HRTEM revealed the heteroepitaxial growth of gold crystallites on flowerlike magnetite materials along the {111} planes, which may account for their smaller and more uniform gold nanoparticles. The stronger metal-support interaction on flowerlike Au/Fe3O4 catalysts was also manifested by the higher reduction temperature of gold than that on particulate magnetite-supported catalysts. In liquid phase hydrogenation of crotonaldehyde, the flowerlike Au/Fe3O4 catalysts show high selectivity (⩾76%) in the entire reaction course and high yield (⩾75%) to crotyl alcohol. They also display excellent separation and recycling characteristics. A perimeter interface mechanism involving the hydroxyl groups on magnetite and the positively charged gold atoms linked to the lattice oxygen of magnetite is established to address the remarkably high selectivity over the flowerlike Au/Fe3O4 catalysts. [Copyright &y& Elsevier]

Abstract: Co/ZnO catalysts with different Co/Zn ratios have been prepared by the coprecipitation method. It is revealed that below the nominal Co/Zn molar ratio of 2, the calcined Co/ZnO samples were constituted by ZnO and ZnCo2O4 spinel. At the nominal Co/Zn ratio of 2, a small amount of Co3O4 spinel emerged. After reduction, the catalysts were composed of fcc Co and ZnO. In aqueous-phase reforming (APR) of ethylene glycol, it is found that the intrinsic activity and selectivity to H2 increase with the increment of the ZnO content. H2 selectivities over the Co/ZnO catalysts ranged from 52% to 89%, which are substantially higher than that of the Raney Ni catalyst at similar conversion. Moreover, the Co/ZnO catalysts produced much less CO in the product gas. With the aid of literature works as well as additional experiments on APR of acetic acid, methanol, and ethanol, the reaction pathways of ethylene glycol in the presence of water on the Co/ZnO catalysts were discussed. [ABSTRACT FROM AUTHOR]

Abstract: A high-performance Pd/Fe3O4 catalyst for aqueous-phase reforming (APR) of ethylene glycol (EG) to H2 was prepared facilely by the co-precipitation method. After proper activation, the Pd was present as highly dispersed metallic nanoparticles with dimension of <3nm, and the Fe was present as magnetite. When compared to Pd catalyst supported on Fe2O3, NiO, Cr2O3, Al2O3, or ZrO2 prepared by incipient wetness impregnation, the Pd/Fe3O4 catalyst displayed superior catalytic performance in terms of activity, selectivity, and stability. The intrinsic activity of the Pd/Fe3O4 catalyst was about three times of that of the second most active Pd/Fe2O3 catalyst under the same reaction conditions. In addition, the Pd/Fe3O4 catalyst retained ∼80% of its initial activity after reaching the steady-state. Notably, the Pd/Fe3O4 catalyst possessed the highest turnover frequency of H2 (109min−1) reported so far, showing its promise as a new practical catalyst for APR of biomass-derived oxygenates to H2. The excellent catalytic performance of the Pd/Fe3O4 catalyst was attributed to the enhanced synergistic effect between small Pd nanoparticles and magnetite in promoting the water–gas shift reaction, the rate-determining step in APR of EG over Pd-based catalysts. [Copyright &y& Elsevier]

Abstract: A rapidly quenched skeletal Ni (RQ Ni) prepared by the melt-spinning method followed by alkali leaching was used as a new category of Ni precursor to fabricate effective chiral Ni catalyst. A series of tartaric acid (TA)–NaBr–modified RQ Ni catalysts (MRQNi) were derived, and the textural and structural properties of the MRQNi catalysts were systematically investigated. It is found that the modification conditions influence profoundly the composition, texture, and Ni crystallite size of the MRQNi catalysts. In liquid phase hydrogenation of butanone to R-(−)-2-butanol, the optimized MRQNi catalyst exhibits much better activity and enantioselectivity than the similarly chirally modified Raney Ni catalyst. Based on the characterizations, the superior catalytic performance of the MRQNi catalyst is mainly attributed to the higher surface content of the sodium–nickel(II) tartrate complex than that on the chirally modified Raney Ni catalyst. [Copyright &y& Elsevier]

Abstract: The Cu/ZnO/Al2O3 catalysts were prepared by the coprecipitation method, and were evaluated in the water–gas shift (WGS) reaction. The effects of the calcination temperature on the BET surface area and crystallite size were characterized. In WGS reaction, the Cu/ZnO/Al2O3 catalysts suffered from continuous deactivation in shut-down/start-up operation – the daily requirement for mobile and residential fuel cell systems. Among them, the Cu/ZnO/Al2O3 catalyst prepared at the calcination temperature of 450°C showed the best activity and stability, with the decrement of the CO conversion of only 12.8% after three shut-down/start-up cycles. Deactivation of the Cu/ZnO/Al2O3 catalysts is attributed to the blocking or deterioration of the active sites by Zn6Al2(OH)16CO3·4H2O resulting from the degeneration of the oxides under cyclic operations. Removal of the hydroxycarbonate species by calcination in air followed by re-reduction could restore the steady-state WGS activity; however, the regenerated catalyst underwent much severe deactivation in subsequent shut-down/start-up operation. [Copyright &y& Elsevier]

Uniform Co–B nanoparticles were synthesized for the first time by chemical reduction of cobalt ion with borohydride in an oil-in-water microemulsion system comprising cyclohexane, polyethylene glycol, and water. The particle size was controlled by modulating the cyclohexane content. With the characterization of X-ray diffraction, selective area electronic diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy, the resulting Co–B nanoparticles were identified to be amorphous alloys ranging in size from 6 to 20 nm. During liquid-phase cinnamaldehyde hydrogenation, the as-synthesized Co–B catalyst was extremely active and more selective than the regular Co–B prepared in aqueous solution. Furthermore, this catalyst also was found to be more durable during the hydrogenation process. [Copyright &y& Elsevier]

Abstract: Uniform spherical Co-B amorphous alloy nanoparticles were prepared by ultrasound-assisted reduction of Co(NH3)2+ 6 with BH− 4 in aqueous solution, and the particle size was adjusted by changing either the ultrasound power or the ultrasonication time. During liquid-phase cinnamaldehyde (CMA) hydrogenation, the as-prepared Co-B catalyst exhibited much higher activity and better selectivity to cinnamyl alcohol (CMO) than the regular Co-B obtained by direct reduction of Co2+ with BH− 4. The higher activity can be attributed to both the higher dispersion of Co active sites () and the higher intrinsic activity (). The higher selectivity can be attributed to both the uniform Co-B amorphous alloy particles and the strong electronic interaction between Co and B, which enhances the competitive adsorption of Cgainst Cn the CMA molecule. Meanwhile, the stronger adsorption for hydrogen on Co active sites was more favorable for Cnation in comparison with the Cnation. [Copyright &y& Elsevier]

Abstract: Mesoscopically spherical Ni–B amorphous alloy nanoparticles were prepared through self-assembly of an ionic surfactant hexadecyltrimethylammonium bromide. During liquid-phase nitrobenzene hydrogenation, the as-prepared mesoporous Ni–B catalyst exhibited higher activity and selectivity than the regular Ni–B obtained via direct chemical reduction, apparently owing to the higher surface area, which ensured high dispersion of active sites and the mesoporous channels that might facilitate diffusion and adsorption of reactant molecules. [Copyright &y& Elsevier]

Abstract: Skeletal Ni (RQ Ni) catalyst was prepared by alkali leaching of rapidly quenched Ni50Al50 alloy. By impregnating RQ Ni with SnCl4 followed by thermal treatment in inert atmosphere, homogeneous Sn-modified skeletal Ni (RQ Ni–Sn) catalysts were obtained. It was found that thermal treatment induces alloying of the deposited metallic Sn with Ni, forming Ni3Sn alloy segregated on the catalyst surface. In aqueous-phase reforming of ethylene glycol, the RQ Ni catalyst was less selective in producing H2 but more selective in producing alkanes than the Raney Ni catalyst described in the literature. This is attributed to the expansion of the lattice of RQ Ni favoring the dissociation of CO and, consequently, the methanation reaction consuming H2. Moreover, the structural difference influences the reaction pathway, with the undesired Ce pathway obstructed on RQ Ni. Modification of RQ Ni with Sn drastically improves the H2 selectivity. On the RQ Ni80Sn20 catalyst, alkane production was virtually retarded, whereas H2 selectivity as high as 98 mol% was achieved at high conversion. Based on the characterizations and previous findings, it is suggested that Sn may block the active sites for CO adsorption and/or dissociation, thus suppressing the undesired methanation reaction. On the other hand, bifunctional Ni–Sn ensembles may form, in which Sn facilitates H2O dissociation while neighboring Ni adsorbs CO, thus promoting the desired water–gas shift reaction, leading to more H2. [Copyright &y& Elsevier]

Abstract: Skeletal Ni catalysts (RQ Ni) prepared by alkali leaching of rapidly quenched Ni–Al alloys have been systematically characterized, focusing on the effect of the cooling rate during alloy preparation. It is found that the residual Al content, texture, structure, surface hydrogen species, and active sites of the RQ Ni catalysts can be controlled by the cooling rate of the Ni–Al alloys. In liquid-phase hydrogenation of 2-ethylanthraquinone (eAQ), the RQ Ni catalyst with higher cooling rate favors hydrogenation of the carbonyl group and retards the saturation of the aromatic ring and the formation of the degradation products, thus leading to a higher yield of H2O2. Based on the characterizations, the improved selectivity is ascribed to the dominant population of strongly chemisorbed hydrogen, which is inactive for the hydrogenation of the aromatic ring, along with the electronic interaction between residual metallic Al and Ni, favoring a carbonyl group-bonded configuration of eAQ on the catalyst. [Copyright &y& Elsevier]

Abstract: Liquid-phase hydrogenation of 2-ethylanthraquinone to 2-ethylanthrahydroquinone has been investigated over Raney Ni, nanosized amorphous Ni–B, and chromium-modified Ni–B catalysts. It has been found that the amorphous Ni–B and chromium-modified Ni–B catalysts exhibited superior selectivity, whereas the chromium-modified Ni–B catalysts had better activity and selectivity than unmodified Ni–B catalyst. Based on the characterizations, the higher selectivity of the amorphous catalysts is ascribed to the dominant population of the strongly bound hydrogen, which is not reactive for the hydrogenation of the aromatic ring, along with the repulsive interaction between the aromatic ring and the electron-rich Ni due to electron donation from alloying B. The addition of chromium decreased the particle size of the amorphous catalysts, which is beneficial for the improvement of activity. Moreover, surface chromium oxide can function as a Lewis acid, which lowers the orbital of the reactant, favoring a carbonyl group-bonded configuration. The best selectivity was achieved over the Ni–Cr–B2 catalyst, where the hydrogenation of the aromatic ring was thoroughly blocked before the saturation of the carbonyl groups. [Copyright &y& Elsevier]