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Bioproducts are chemicals derived from renewable biological resources and have the potential to replace petrochemicals in the future to tackle the arising environmental problems. Among them, lactic acid (LaA) is attracting significant focus from both academia and industry due to its wide application in our daily life. In this study, lactic acid is produced from the chemo-catalytic converting the glucose over the homogeneous ErCl 3 catalyst in an aqueous solution. The highest LaA yield of 97% was obtained at a full glucose conversion on this homogeneous catalyst at 260 °C through process optimization. Furthermore, the techno-economic analysis (TEA) was leveraged for the concept design of LaA biorefineries. Three parameters, namely the selling price of LaA, the price of glucose, and the catalyst recyclability were identified for the overall profit. Therefore, this work highlights the notable ability of TEA for the concept design or simulation to screen the promising biorefinery industrial process, and intuitively provide us with the internal rate of return of a certain chemical process. Thus, this work is supposed to provide the feasibility of LaA acid production from a chemo-catalytic process from both the technical and scientific points of view. [Display omitted] • A high lactic acid yield was obtained on the ErCl 3 homogeneous catalyst. • The potential of using converting glucose to lactic acid was analyzed. • Concept design and tech-economic analysis were performed. [ABSTRACT FROM AUTHOR]

Catalytic converting the lignin-derived bio-oil to liquid fuel is one promising methodology to reduce the dependence on petroleum-based fuel while easing the atmospheric carbon dioxide burden. Hydrodeoxygenation (HDO) is one commonly used method to convert and upgrade bio-oil from biomass. In the present work, a Ru-promoted MoFeP/Al 2 O 3 catalyst was prepared and evaluated the HDO performance by converting two model compounds, guaiacol and anisole with a batch reactor at 250 °C. This catalyst shows a quite good HDO performance over the two model compounds, in which, oxygen was removed from the phenolic and hydrocarbons were produced as the product. Kinetic studies were also performed to build the reaction network and elucidate the reaction pathway of guaiacol and anisole HDO reactions. The primary, secondary, and tertiary products can be identified for the HDO reactions. A better understanding of HDO chemistry from the fundamental study can lead to more efficient catalysts for the target products. [Display omitted] • A highly active Ru-MoFeP/Al 2 O 3 was proposed in HDO reaction. • Reaction network of guaiacol and anisole HDO reaction were proposed. • Primary product, secondary or tertiary products can be identified. [ABSTRACT FROM AUTHOR]

Abstract: The influence of adsorbed sulfide (S2− ads) on CO monolayer electro-oxidation reaction (CMOR with M for monolayer to emphasize that oxidation always starts with a saturated CO coverage) on carbon-supported Pt nanoparticles (Pt/C NPs) was investigated using electrochemical and in situ ATR-SEIRAS (attenuated total reflection-surface enhanced IR absorption spectroscopy) techniques. An enhanced kinetics of CMOR on the S2− ads-Pt/C was observed by potentiodynamic CO stripping and potentiostatic CO oxidation analyses. Electrochemical impedance measurements revealed a weakened bonding of oxygen-containing species with the S2− ads-Pt/C surface as compared with the clean Pt/C surface, which we believe was the main reason for the observed enhanced CMOR by the S2− ads. The in situ SEIRAS data showed the existence of both linear- and bridge-bonded CO (COL and COB respectively) in all samples and that the sulfide adsorption increased substantially the fraction of the former on the available Pt sites and facilitated the conversion between them. Our results also indicate that the frequently observed pre-CMOR current arises most likely from oxidation of weakly-bonded CO rather than from reactions taking place at defect sites. [Copyright &y& Elsevier]

Abstract: CO hydrogenation is carried out on Co/CNT and CoRe/CNT catalysts at 483K, 1.85bar, H2/CO=10. The study addresses a fundamental understanding of the effects of reaction conditions (syngas pressure, temperature and GHSV) and Re promotion on the Co activity and selectivity by SSITKA. A systematic SSITKA study was performed to gain a better understanding of the surface reactions at different conditions by measuring the surface concentrations of CO and CH x intermediates on Co. The TOFs of CO conversion and methane formation are found to be sensitive to H site coverage, which is affected by the competitive adsorption between H2 and CO. Higher temperature mainly increases the reaction rate constant, which changes more significantly as compared with the site coverage of the H and CO. CO pressure and temperature have more significant effect on the methane selectivity than H2 pressure. Re has little effect on the TOF and selectivity of the Co/CNT catalyst. SSITKA experiment reveals that both NCO and increase slightly with Re promotion. The surface coverage of CO is about ten percent higher on the Re promoted sample, suggesting that Re might be able to enhance CO adsorption a little bit. However, Re promotion does not change the intrinsic site activity and apparent activation energy. The apparent activation energy for methane formation is found to be about 118kJ/mol for both promoted and unpromoted catalysts. [Copyright &y& Elsevier]

Abstract: We report an investigation of the formation mechanism of a gold (Au) thin-film electrode made by electroless deposition for in situ electrochemical (EC) attenuated-total-reflection surface enhanced infrared adsorption spectroscopy (ATR-SEIRAS). The Au thin film was generated via galvanic electroless deposition from [Au(S2O3)2]3− precursor and consisted of ∼46nm Au nanoparticles (NPs) deposited on Si infrared window. The observation of v(Au–S) (263cm−1) and v(S–S) (454cm−1) on the freshly deposited Au film using surface enhanced Raman spectroscopy (SERS) confirmed that the initial adsorbed sulfur species was S2O3 2−. Subsequent acid-treatment broke the S–S bond and yielded Au surface-bound atomic sulfur species. EC stripping of them led to the formation of (bi)sulfate identifiable by in situ EC ATR-SEIRAS. A sulfur coverage of 0.5 was estimated. We also discovered that square-wave treatment of the Au film led to significant surface reconstruction and much enhanced oxygen reduction reaction (ORR) activity. We attribute the latter to the reconstruction-caused new sites that could stabilize better the adsorbed ORR intermediates for facilitating the subsequent reaction step(s). [Copyright &y& Elsevier]

Abstract: The CO2 capture properties of a new nanocrystalline CaO-based mixed oxide (CaCeZrO x ) were studied in both TGA and a fixed bed reactor. The kinetics of CO2 capture at dry conditions was compared between these two reactors. The application of the new CO2 acceptor in sorption enhanced steam methane reforming was studied by a fixed-bed reactor in the presence of 40wt% nickel hydrotalcite catalysts. Experimental results show that the new CO2 acceptor, CaCeZrO x has a significantly improved CO2 capture capacity and cyclic reaction stability compared to natural dolomites, because of the large pores and stable backbone structure. It has also been observed that the sorption enhanced steam methane reforming in the fixed bed reactor produces more than 95% H2 in a single-step process. Increase in production of hydrogen and higher CO2 capture capacity are also observed with an increase in the residence time of methane. Steam has a significant effect on the stability of the acceptors, but not very much on the kinetics and capacity of CO2 capture. The capacity of CO2 capture on the acceptors in the SESMR process cannot be predicted by the independent CO2 capture kinetic study on acceptor alone. A synergy effect between the sorption enhanced reactions and CO2 capture on the CO2 capture capacity was observed on the all solid CaO based CO2 acceptors. [Copyright &y& Elsevier]

Abstract: First-principles calculations based on density functional theory (DFT) have been used to investigate the reaction mechanism of dry methane reforming on Ni(111). The most energetically favorable adsorption configurations of the species involved in this process are identified and the transition states for all the possible elementary steps are explored by the dimer method. Then, the related thermodynamic properties at 973.15K are calculated by including the zero-point energy correction, thermal energy correction and entropic effect. It is found that CO2 dissociates via a direct pathway to produce CO and O dominantly, and atomic O is revealed to be the primary oxidant of CH x intermediates. Based on this information, two dominant reaction pathways are constructed as both the CH and C oxidation are found to be likely. The reaction network begins with the dissociation of CO2 and CH4, and then the generated CH and C are oxidized by atomic O to produce CHO and CO, followed by the CHO decomposition to finally generate CO and H2. As for these two reaction pathways, the oxidation step is predicted to determine the overall reaction rate under the current investigated conditions, while the CH4 dissociation is found to be the rate-limiting step at lower temperatures. [Copyright &y& Elsevier]

Abstract: The objective of this work was to gain a better understanding of the influence of Sn on the dispersion of Pt in platinum supported SBA-15 catalysts and thereby on the dehydrogenation of propane (DHP) activity, selectivity to propylene, coking and catalyst stability. To this end, DHP over Pt-SBA-15 and Pt-Sn-SBA-15, prepared by incipient wetness impregnation (IW), was studied at 793K by means of tapered element oscillating microbalance (TEOM) coupled with on-line gas-chromatography. This allowed us to determine simultaneously the comprehensive information from a single catalysis experiment. The catalysts were characterised by N2-physisorption, transmission electron microscopy (TEM-EDXS), X-ray diffraction (XRD) and H2-chemisorption, which revealed that the presence of Sn results in higher Pt dispersion by the formation of Pt–Sn alloy. It is evident from TEOM studies that after 220min on stream the amount of coke formed is almost three times higher over Pt-Sn-SBA-15-IW than on its counterpart Pt-SBA-15-IW, albeit the former exhibits considerably higher propane conversion, superior selectivity to propylene and stability than the latter. It is demonstrated that propane conversion and coke formation on the catalysts can be correlated with Pt particle size. A modified drain-off effect is proposed to explain the superior selectivity and stability of the bimetallic than the monometallic catalyst. [Copyright &y& Elsevier]

Abstract: Carbon nanofibers (CNFs) have been used as templates for manipulating the properties of Ni catalyst particles. Both incipient wetness impregnation and deposition–precipitation have been used to prepare the catalysts. Relatively well-dispersed Ni nanoparticles have been prepared on oxidised CNFs by incipient wetness impregnation. The diameter of the CNFs has been shown to have a significant effect in determining the Ni crystal size. In addition, CNFs are suitable templates to induce microstrain to metal particles. Such microstrain has significant effects on the activity of Ni crystals during ethane hydrogenolysis. This provides new opportunities to manipulate the crystal size and activity of the metal by selecting proper carbon nanofibers as support. TPO has been demonstrated as a powerful tool to study the CNF supported catalyst and to provide information on Ni loading and relative activity of NiO for CNF oxidation. [Copyright &y& Elsevier]

Abstract: Cu/CNF and Cu/CeO2/CNF catalysts have been synthesized and characterized on different nanostructured carbon nanofibers (CNF). The samples have been tested in isopropanol dehydrogenation. Cu/CNF show similar activity to Cu catalysts supported on activated carbon. Cu/CeO2 nanotubes have been synthesized on the CNF surfaces. The Cu/CeO2 nanotubes exhibit much higher activity and lower activation energy than Cu/CNF. The selectivity towards acetone depends on the fraction of CeO2 in the composites. High activity and selectivity has been achieved with a Cu12Ce5/CNF catalyst. [Copyright &y& Elsevier]

Abstract: A series of silica supported Fe catalysts were prepared by different methods in order to obtain varying Fe particle sizes. The catalysts were characterized by XRD, TPR, BET, and TEM. The CNT growth from CO disproportionation was studied in order to establish a relationship between the CNT growth rate and the particle size. We found that there is an optimum catalyst particle size at around 13–15nm which will lead to the maximum growth rate. The influence of the metal loading on the growth rate was also investigated. A CNT growth model has been formulated to explain the experimental results. [Copyright &y& Elsevier]

Aqueous phase reforming (APR) of ethylene glycol was performed at 225 °C and 30 bar in batch and continuous reaction conditions. The effect on the APR performance by functionalizing carbon supports with nitrogen and adding Mn to Pt-based catalysts was investigated. The presence of nitrogen species on the carbon surface and Mn-addition (PtMn) improved the catalytic activity and promoted H 2 production. XPS results suggest that the enhancement of the catalytic activity may be attributed to charge transfer from platinum to the nitrogen groups and Mn. Pt-based catalysts were stable under the studied reaction conditions, while up to 97 % of the manganese leached into the liquid solution during APR. However, the catalytic activity was maintained even with such significant decrease in Mn content, indicating that only a small amount of Mn is necessary to maintain the promotional effect on Pt during APR. [Display omitted] • Electronic interactions between Pt-N and Pt-Mn led to enhanced catalytic activity. • N-doped carbon nanofibers effectively improved H 2 yield in aqueous phase reforming. • Pt-based catalyst promoted with Mn presented higher H 2 yield and selectivity. • Metal-support interactions are key factors in promoting catalytic activity. [ABSTRACT FROM AUTHOR]

Catalytic conversion of cellulose to diols is an attractive approach in the valorization of biomass, because of the high atom efficiency of the reaction process. The work here highlights the potential of cellulose as a renewable feedstock to produce value-added chemicals, especially vicinal diols. The catalytic conversion of cellulose in water on Ni-Cu/4ZnO-CNT catalyst is discussed, with a focus on four main reaction pathways leading to the formation of C 2 , C 3 , C 4, and C 6 vicinal diols, involving hydrolysis, retro-aldol condensation, hydrogenation, isomerization, dehydrogenation, and thermal side reactions. By modifying the Ni-Cu bimetallic active sites, the pathways can be manipulated, resulting in selective retro-aldol condensation C-C cleavage, leading to a shift towards the selective production of either ethylene glycol (EG) or 1,2-propylene glycol (1,2-PG). Finally, we explore the optimization of reaction conditions to tune product selectivity. This study provides important insight into the catalytic conversion of cellulose and offers promising avenues to produce value-added chemicals from renewable feedstocks. [Display omitted] • Bimetallic NiCu/ZnO-CNT catalyst was proposed in direct cellulose conversion to diols. • Reaction pathway was built based on the kinetic studies. • Product selectivity can be tuned via varying the Ni-to-Cu ratio. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using UV–vis-NIR to analyze the kinetics of ethylene oxychlorination. • Co-promoter effect of alkali and alkali earth metals on ethylene oxychlorination. • Methods to design and predict the reaction rate and Cu2+ concentration for the steady-state. The comprehensive kinetic study for CuCl 2 /γ-Al 2 O 3 -based catalysts was performed to elucidate the co-promoter effect in the ethylene oxychlorination, one of the most significant industrial processes to produce vinyl chloride monomer. Kinetic analysis was performed separately by transient kinetic studies, taking account of the reduction and oxidation steps in the catalytic cycle. The promoter effects on ethylene oxychlorination were ascribed to their influence on the Cu2+ reduction or Cu+ oxidation in the catalytic cycle. The reaction rate-diagram was gained and used to predict the steady-state reaction rate and Cu oxidation state by an operando setup combing MS and UV–vis-NIR spectroscopy. The results indicated that the K-doped catalyst could greatly increase the reaction rate of the oxidation step, which gave rise to higher Cu2+ concentration on the catalyst. Mg-doped catalyst had a great effect on enhancing the reaction rate for the reduction step. K and Mg co-doped catalyst had the dual effect, both the reaction rate and Cu oxidation state were located between K and Mg mono-doped catalyst. The results of steady-state reactions indicated that the reaction rates were quite close with that predicated by the rate-diagram. Byproduct analysis during the steady-state was also performed, the results demonstrated that the co-promoted catalysts can also reduce the byproduct formation. The current study is expected to provide one way for exploring the potential benefits of co-promotion on CuCl 2 /γ-Al 2 O 3 -based industrial oxychlorination catalysts to improve the catalytic performance and understand the reaction further. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyethylenimine over mesoporous carbon spheres solid sorbent for CO 2 capture. • CO 2 capture capacity (3.22 mmol/g) was achieved on 62.5PEI/MCS-1.1. • PEI /MCS will be one of the ideal candidates for CO 2 capture in the future. A novel low-concentration CO 2 capture material (PEI/MCS) was developed by loading polyethylenimine (PEI) over mesoporous carbon spheres (MCS) with high porosity. The effects of pore structure, PEI loading, capture temperature, and promoters on CO 2 capture of PEI/MCS were studied. The MCS with perfect spherical morphology was successfully synthesized by a hard-template assisted reverse emulsion method. The pore structure of MCS was adjusted by tuning the ratio of silica to carbon (Si/C) in the precursors. With increasing the Si/C from 0.8 to 1.1, the pore volume of MCS increased from 1.25 to 2.68 cm3/g. The optimal PEI loadings depending on the pore volume of MCS were 45, 62.5, and 65 wt.% for MCS-0.8, MCS-1.1, and MCS-1.5, respectively. The highest CO 2 capture capacity (3.22 mmol/g) was achieved on 62.5PEI/MCS-1.1 at CO 2 partial pressure of 0.05 bar (5 vol.%, a typical concentration of the tail gas from natural gas power plant and natural gas processing plant) and temperature of 75 °C, outperforming most of the solid amine sorbents reported at similar condition. However, the cycling stability of PEI/MCS is poor at the capture-regeneration temperature of 75 °C. The promoters Span 80 and 1,2-epoxybutane did not show remarkable effect on the cycling stability of PEI/MCS at 75 °C. Decreasing the capture-regeneration temperature can significantly improve the stability of PEI/MCS and there is almost no CO 2 capacity loss (regeneration >99.5 %) when the temperature decreased to 50 °C. As a result of high CO 2 capacity and excellent regenerability and stability, PEI /MCS will be one of the ideal candidates for CO 2 capture in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Initiation and progress of carbon formation on alloy 601 surfaces captured. • Less carbon under infinite (I- a c) than under finite low carbon (FL- a c) activity. • Raman spectroscopy: different degree of ordering of the carbon formed. • CO only (I- a c): Thin Cr 2 O 3 surface scale stabilized; grain boundaries beneficial. • In synthesis gas (FL- a c): (Ni, Fe, Cr) 3 O 4 spinel redox process promotes carbon. Ni and Fe are excellent catalysts for carbon formation, and industrial alloys are therefore susceptible to metal dusting corrosion; a costly issue in e.g. synthesis gas manufacture. The objective of this work is to better understand the initial reaction phenomena leading to metal dusting, and thereby minimize the corrosion through optimum alloy selection and pretreatment. Pre-oxidized alloy 601 samples were subjected to carburizing gaseous environments at 750 °C, and carbon formation and surface oxide layer development were investigated by SEM, optical microscopy, AES and Raman spectroscopy. Thin (S)TEM/EDS cross-section lamellae were prepared by Focussed Ion Beam milling. Beyond the initial incubation period, less carbon is formed under 10% CO/Ar than under synthesis gas with finite low carbon activity. Cr 2 O 3 evolves as a thin surface oxide layer with only CO reacting and more ordered carbon develops with increasing exposure time. In contrast, oxidation yields (Ni, Fe, Cr) 3 O 4 spinel formation while the materializing carbon remains its disorder during prolonged exposure to synthesis gas. The metal dusting corrosion rate is hence lowered due to Cr 2 O 3 stabilization, while the spinel represents an unstable redox state that continuously yields new carbon. A fine-grained alloy surface structure is also found beneficial to the Cr 2 O 3 formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electronic structure of V 2 O 3 upon single-atom doping is examined. • A weak Lewis acid-base interaction is found to occur on the pristine surface. • The first dehydrogenation step is identified as the rate-limiting step for PDH. • Mn 1 -V 2 O 3 is suggested to be a good catalyst candidate for PDH. Vanadium-oxide-based catalysts have recently been found very promising for the catalytic dehydrogenation of propane. In this work, self-consistent density functional theory calculations have been performed to examine how the electronic structure of the V 2 O 3 (0001) surface is modified by single-atom doping and how the catalytic properties can be tailored to propane dehydrogenation. The structural stability of single-atom-doped V 2 O 3 (0001) surfaces is assessed by comparing the adsorption energies of single atoms with the cohesive energies of bulk metals. A weak Lewis acid-base interaction is found to occur on the pristine surface, which can be strengthened and weakened by substitution of single atoms for V and O, respectively. On these two types of oxide surfaces, single atoms act as promoters and active sites. The first dehydrogenation step is identified as the rate-limiting step by microkinetic analysis. On all the single-atom-doped surfaces, the activation energy for water formation is higher than that for hydrogen recombination, implying that reduction of the oxide surfaces is difficult to take place during the course of the reaction. If a compromise between the catalytic activity and catalyst selectivity is made, Mn 1 -V 2 O 3 is suggested to be a good candidate as the catalyst for propane dehydrogenation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Support effects exist on Cs/Al 2 O 3 catalyzed aldol condensation of MeOAc with HCHO. • The strong interaction promotes the dispersion of Cs on Al 2 O 3. • The composition of Cs species varies with the identity of Al 2 O 3. • A balance between acidic and basic sites contributes to the production of MA. In this work, the support effects on vapor-phase aldol condensation of methyl acetate (MeOAc) with formaldehyde (HCHO) over cesium catalysts are understood by the employment of Al 2 O 3 with different morphologies and crystal phases. The structural and electronic properties of these supported Cs catalysts are characterized by multiple techniques, such as XRD, HAADF-STEM, EDS-mapping, XPS, NH 3 -TPD and CO 2 -TPD. The Cs species are found to be highly dispersed on the Al 2 O 3 surfaces, and their compositions vary with the identity of Al 2 O 3. A combined catalyst characterization and testing results indicates a balance between acidic and basic sites, i.e., an acid-base synergy, for the production of MA: the excess acidic sites lead to the lower MA selectivity due to the promoted further condensation, while the excess basic sites with the lower MeOAc conversion due to the insufficient activated HCHO species. These insights could be valuable for the design and optimization of catalysts for this reaction. [ABSTRACT FROM AUTHOR]

Nanocrystalline ZnO/CNT with enhanced electrochemical reduction of CO 2 to syngas [Display omitted] • Faradaic efficiency of synthesis gas of more than 75% was achieved on small ZnO particles. • The H 2 /CO ratio can be tailored by the ZnO particle size. • DFT study revealed the ZnO surface stabilizes CO 2 * and COOH* intermediates, therefore more active for CO 2 activation. • ZnO is promising for electrochemical syngas production. Electrochemical reduction of CO 2 and H 2 O can provide a promising pathway to synthesis gas generation for renewable electric energy storage and fuel production with the closed anthropogenic carbon cycle. However, the lack of affordable highly active catalysts to activate the stable CO 2 and H 2 O molecules presents a substantial challenge. Here we report ZnO supported on nanocarbon as a cost-effective and active catalyst for selective conversion of CO 2 and H 2 O to predominately synthesis gas, with higher selectivity and activity compared to polycrystalline metal catalysts such as Ag and Cu. The H 2 /CO ratio can be tailored for different industrial processes by tuning the applied potential and the particle size of ZnO. Density functional theory calculations showed that the higher activity of ZnO is related to more significantly stabilized intermediates, CO 2 *, COOH, and CO* compared to Cu and Ag. Our results highlight a promising class of low-cost, abundant oxide as active electrocatalysts for synthetic fuel production from CO 2. [ABSTRACT FROM AUTHOR]

Abstract: Cobalt based Fischer–Tropsch synthesis catalysts were studied by adsorption microcalorimetry. A series of catalysts consisting of 20wt% cobalt supported on γ-Al2O3 were examined. Cobalt particle size as evaluated by H2 chemisorption varied from 4.8 to 16.7nm in diameter. H2 and CO were examined as probe molecules and their adsorption on reduced cobalt catalyst was investigated. The results show only minor differences in the initial heat of adsorption for the studied catalysts, while at intermediate coverages (20–60%) the heat of adsorption appears to be nearly identical. [Copyright &y& Elsevier]

Enhanced electrochemical reduction of CO 2 to syngas on CuZnOCNT catalyst. • Copper doping on ZnO shifts the ECR activity towards CO formation closer to the top of the volcano. • The optimal amount of copper is around 20 at% for CO formation from electrochemical reduction of CO 2. • Higher amount of Cu doping leads to metallic Cu segregation, resulting in higher H 2 evolution activity. • The 14Cu86ZnO/CNT catalyst shows best performance in terms of syngas (1:1 ratio) production at -0.9 V, better than Ag foil. Electrochemical CO 2 reduction is a promising method for the production of CO 2 neutral fuels and chemicals from renewable electricity. ZnO supported on CNT is a low-cost electro catalyst that can produce syngas from CO 2 and H 2 O. A rational catalyst design strategy for further improvement of the ZnO/CNT catalyst is to dope with copper to strengthen the binding energy of the CO intermediate, which could improve the activity. In this work, a series of CuZnO/CNT catalysts with intimate Cu and Zn contact and various Cu loadings are prepared. By varying the copper content we show that the synergy of copper and zinc improves the activity for CO formation, and the optimal copper content is 20 at%. On hydrogen evolution, the addition of copper has a two-fold effect. This reaction is enhanced by the reduced ZnO particle size obtained when copper is added, but at similar particle sizes of ZnO, a suppression is observed with increasing copper content as CO evolution is enhanced. Stability tests showed that pure ZnO phase is more stable than metallic copper on ZnO. Compared with polycrystalline silver, the CuZnO/CNT catalysts are more active for syngas formation at a useful CO: H 2 composition. This work demonstrates that the viability of DFT based rational design of electrochemical CO 2 reduction catalyst. By varying CuZnO composition as well as crystallite size, one is able to tune the electrochemical reduction activity towards CO and H 2 , and therefore achieve desired syngas ratio. [ABSTRACT FROM AUTHOR]

• Small Ni particles exhibit higher steam methane reforming activity than large ones. • The size-dependent activity of Ni catalysts is related to the surface-dependent activity. • Ni(2 1 1) is the most active surface for steam methane reforming. • Decreased Ni(2 1 1) surface fraction results in reduced Ni activity as size increases. Fundamental understanding of the size-dependent activity is essential to harness powers of the nanocatalysts. Here we report an experimental and theoretical study of the Ni particle size effect on activity of steam methane reforming (SMR) to achieve a better understanding of the size dependence of kinetic behavior at an atomic level. A kinetic study illustrated the higher forward methane turnover frequency on the smaller sized Ni particles. The size-dependent activity was well reproduced by microkinetic modeling on a truncated octahedron model with the kinetic parameters estimated by the improved unity bond index-quadratic exponential potential (UBI-QEP) and the Brønsted–Evans–Polanyi (BEP) relationship. Microkinetic modeling suggested that the size-dependent activity of Ni catalysts is associated with the surface-dependent activity. Much higher activity of Ni(2 1 1) than Ni(1 1 1) and Ni(1 0 0) accompanied by decreased Ni(2 1 1) surface fraction results in reduced Ni activity as particle size increases. The activity of Ni(1 1 1) is limited by high free energy barriers, while that of Ni(1 0 0) is limited by site blockage by C* and CH*. This work offers a feasible approach to gain insight into size-dependent activity and to aid rational catalyst design for SMR in which preparing extremely small Ni particles (≤6 nm) might be a good strategy. [ABSTRACT FROM AUTHOR]

Abstract: Rh supported on Zr x Ce1−x O2–Al2O3 (x =1, 0.5, 0.25, 0) catalysts are studied for catalytic partial oxidation of methane to synthesis gas. Alumina based nanocomposites are prepared through a citrate mediated route by modifying the alumina support with cerium and zirconyl nitrates via a simple evaporation-drying or a spray drying method. The effect of the commercial alumina types and the preparation method on the structure and thermostability of the nanocomposites has been studied based on the characterization by XRD, Raman spectroscopy, DTA, TEM and nitrogen adsorption–desorption measurements. Evonik Aeroxide AluC based nanocomposites prepared by spray drying give the highest thermostability concerning the sintering and phase transformation of the composites. Rh with a 0.1 or 0.5wt.% loading is deposited on these nanocomposites by incipient wetness impregnation method. After calcination at 1173K for 5h, these nanocomposites supported Rh catalysts are tested in the fixed-bed reactor for methane partial oxidation. It is found that the smaller c-CeO2 crystal size in the nanocomposites, i.e. the higher oxygen vacancy concentration, would be responsible of the lower ignition temperature due to the enhanced reducibility, whereas the higher Rh dispersion would be responsible of the higher methane conversion and selectivity to synthesis gas. Additionally the Rh dispersion is found to be linked to the BET surface area. The stability of the nanocomposites is also studied under reaction conditions. [Copyright &y& Elsevier]

Abstract: Polyaniline/CNT composites have been synthesized by means of in situ polymerization on two different macroscopic structures of CNTs, namely non-ordered CNT powders and aligned CNT films supported on Ti foils. SEM, TEM images illustrated that a rather uniform layer of PANI with a thickness of 5–8nm has been successfully coated on the aligned CNTs. The molecular structure and the degree of protonation of PANI have been studied by means of Raman spectroscopy. The alignment of CNT film on the foils favors the formation of uniformly distributed layer of the protonated PANI on each CNT, which is possibly a result of controlled diffusion in the pseudo 1D channel and a confinement in the space between CNTs in the aligned CNT films. Furthermore, the reaction temperature has a more pronounced effect on the degree of protonation of PANI on the CNT powders than on the aligned CNT films. [Copyright &y& Elsevier]

Abstract: The catalytic activity and stability in the water–gas shift reaction have been tested for Au-based catalysts prepared by deposition of Au from colloid solutions. The supports that have been used are TiO2, TiO2 supported on carbon nanofibres (CNF) and CNF. Thermal treatments of the samples show that the Au particle size depends on the support material and hence the interaction between the Au particles and the support. In situ X-ray absorption spectroscopic (XAS) measurements during the water–gas shift reaction show no changes in the first Au–Au coordination number for the catalysts containing CNF. Furthermore, improved short-time stability is obtained compared to the AuTiO2 catalysts. The improved stability is achieved by the CNF stabilising small TiO2 particles and hence prevent subsequent sintering of the Au particles. [Copyright &y& Elsevier]

• The "dimethylcyclopropane" pathway is dominant for 2-pentene isomerization. • The ring-opening step is the rate-determining step for the isomerization reaction. • Van der Waals interactions would change the scaling relations in zeolite catalysis. Periodic density functional theory (DFT) calculations have been performed to examine the monomolecular reaction mechanism for 2-pentene skeletal isomerization catalyzed by acidic zeolite Beta, Mordenite, and ZSM-5. The use of periodic models allows consideration and analysis of zeolite steric constraints that occur within zeolite microspores. Three different reaction pathways, the "dimethylcyclopropane" (DMCP), methyl shift, and ethyl shift mechanisms, have been considered. The DMCP mechanism which includes rearrangement of protonated cyclopropane is proposed as the dominant reaction pathway, and the ring-opening step determines the overall reaction rate. Comparison of the effective energy barriers for 2-pentene isomerization over the three different zeolites reveals that large 12-ring channels of Beta and MOR have little steric hindrance effect on 2-pentene isomerization while small 10-ring of ZSM-5 significantly increases the reaction activation energy. Calculated results also indicate that the adsorption heat of ammonia is a good descriptor for the reactivity of zeolites without taking into account long-range dispersive forces. In contrast, linear scaling relations cannot be obtained by using the BEEF-vdW functional because van der Waals interactions between zeolites framework and guest molecules affects the energetics of the isomerization reaction and changes the transition state energy scaling relation in zeolite catalysis. [ABSTRACT FROM AUTHOR]

• The reducibility and structural stability of LaMO 3 (M = Sc - Cu) are examined. • The first four LaMO 3 perovskites have very high oxygen vacancy formation energies. • The maximum possible oxygen deficiency in LaMO 3 (M = Mn - Ni) is 0.5. • LaCuO 3 can lose one lattice oxygen atom per formula unit before it is deactivated. Periodic density functional theory calculations have been performed to examine the effect of oxygen deficiency on the structural stability of Lanthanum-based perovskites (LaMO 3), where on-site Coulomb interactions have been addressed by an additional Hubbard-type term. Calculated results indicate that with the exception of LaFeO 3 , the oxygen vacancy formation energy (Δ E f o r m a t i o n , v a c ) of LaMO 3 (M = Sc - Cu) becomes less positive when moving across the first transition metal period. The first four LaMO 3 perovskites have very high oxygen vacancy formation energies and can hardly be reduced under mild conditions, while the other five perovskites exhibit a much greater reducibility. During the formation of the first oxygen vacancy in LaMO 3 (M = Mn - Cu), the nearest neighbor transition-metal cations serve as the primary acceptors of the electrons left behind. As oxygen atoms are further removed, square-based pyramidal and tetrahedral coordination geometries appear successively, and an abrupt increase in Δ E f o r m a t i o n , v a c is observed at a specific oxygen deficiency (δ), which defines the maximum possible δ in the perovskite structures. Under this definition, the M3+ cations (M = Mn - Ni) can be possibly reduced to M2+ while LaCuO 3 may lose at most one lattice oxygen atom per formula unit before it is deactivated. [ABSTRACT FROM AUTHOR]

• Novel small-sized mesoporous TS-1 (STS-1) is synthesized by SAC method. • Cost-efficient TPABr is used as template for STS-1 synthesis. • The effect of TPABr concentration of STS-1 is investigated. • The Au/STS-1 catalyst has good performance for propene epoxidation with H 2 /O 2. Designing cost-effective titanium silicalite-1 (TS-1) with enhanced mass transfer ability is of prime scientific and industrial importance. In this work, a novel small-sized mesoporous TS-1 (STS-1) material is first synthesized in cheap TPABr system using steam-assisted crystallization method. Compared with cheap microporous TS-1 prepared by classical hydrothermal method (HTS-1) with particle size of 950 nm, STS-1 shows mesoporous character of 13 nm and reduced average particle size of 590 nm. Moreover, effect of TPABr concentration is systematically investigated, and both of insufficient and overmuch TPABr concentrations are unfavorable because of low crystallinity and exorbitant price, respectively. Importantly, the catalytic performance of cost-effective Au/STS-1 for direct propene epoxidation with H 2 and O 2 is much better than that of Au/HTS-1, and comparable to the performance of the expensive Au/TS-1. By multi-characterizations and activation energy analysis, the underlying mechanism for the enhanced performance is further discussed. This work sheds new light on the design and synthesis of highly effective and cost-efficient TS-1 catalysts. [ABSTRACT FROM AUTHOR]

Transition metals such as Fe and Ni are the most commonly used catalysts for the growth of carbon nanofibers (CNFs) via CCVD method, and they always remain in the raw products. Much attention has been paid to purify CNFs, i.e., to remove residual metal particles and supports, before their use in most cases. However, some recent studies show that the residual metal particles usually attach at the tips of CNFs, and exhibit a different shape in comparison with the initial metal catalysts and as a result unique catalytic performance. The present review focuses on the state-of-the-art of the developments of synthesis of reshaped Fe and Ni particles at the tips of CNFs and their catalytic applications in cellulose conversion, selective hydrogenation and ammonia decomposition. In particular, effects of catalyst support, carbon source and its concentration, reaction temperature and etching gas are discussed. Moreover, the carbon adsorbates induced effect is highlighted as one of the key factors governing the reshaping of Fe and Ni particles. [ABSTRACT FROM AUTHOR]

High-purity H 2 was produced by the sorption enhanced steam reforming (SESR) of acetic acid, a model compound of bio-oil obtained from the fast pyrolysis of biomass, in a fluidized bed reactor. A Pd/Ni–Co hydrotalcite-like material (HT) and dolomite were used as reforming catalyst and CO 2 sorbent, respectively. The hydrogen yield and purity were optimized by response surface methodology (RSM) and the combined effect of the reaction temperature ( T ), steam-to-carbon molar ratio in the feed (steam/C) and weight hourly space velocity (WHSV) upon the sorption enhanced steam reforming process was analyzed. T was studied between 475 and 675 °C, steam/C ratio between 1.5 and a 4.5 mol/mol and WHSV between 0.893 and 2.679 h −1 . H 2 yield, H 2 selectivity and H 2 purity, as well as the CH 4 , CO and CO 2 concentrations in the effluent gas, were assessed. The operating temperature proved to be the variable that had the greatest effect on the response variables studied, followed by the WHSV and the steam/C ratio. The results show that the H 2 yield, H 2 selectivity and H 2 purity increased, while the CH 4 , CO and CO 2 concentrations decreased, concurrently with the temperature up to around 575–625 °C. Higher values of the steam/C ratio and lower WHSV values favored the H 2 yield, H 2 selectivity and H 2 purity, and reduced the CH 4 concentration. It was found that the SESR of acetic acid at atmospheric pressure and 560 °C, with a steam/C ratio of 4.50 and a WHSV of 0.893 h –1 gave the highest H 2 yield of 92.00%, with H 2 purity of 99.53% and H 2 selectivity of 99.92%, while the CH 4 , CO and CO 2 concentrations remained low throughout (0.04%, 0.06% and 0.4%, respectively). The results also suggested that a slow CO 2 capture rate led to a poor level of hydrogen production when the SESR process was carried out at low temperatures, although this can be improved by increasing the sorbent/catalyst ratio in the fluidized bed. [ABSTRACT FROM AUTHOR]

Highlights: [•] The relationship between the reaction rate and the Pt-Re particle size is found to follow a volcanic curve. [•] Smaller sized Pt-Re/CNTs catalysts lead to increased activity together with enhanced coking behavior. [•] Larger sized Pt-Re/CNTs catalysts favor the cleavage of the secondary C–O bond for both glycerol and 1,2-propanediol. [•] The dependence of reaction pathway on particle size is correlated. [Copyright &y& Elsevier]

Highlights: [•] Fe-CNFs/CMFs catalysts were prepared by using CCVD method. [•] Fe particles located on the tops of carbon nanofibers. [•] Fe crystal phases were changed from Fe3C to α-Fe(C) when from 0.20 to 0.33atm. [•] Fe3C and α-Fe(C) crystal phases were easily nitrided into Fe2N. [•] Structured polyhedral Fe2N catalyst was more active for ammonia decomposition. [ABSTRACT FROM AUTHOR]

Highlights: [•] Monolithic structures, microchannel reactors and carbon nanofibers on carbon felt have been studied. [•] All reactors provide good FT activity, selectivity and stability. [•] All reactors have good mass and heat transfer properties. [•] The reactors can be operated without significant internal diffusion limitation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Efficient Co catalyst on 3-D structured carbon nanofiber (CNF)/carbon felt (CF) as compact F–T synthesis reactor. [•] Improved stability by coated thin layer on CNFs. [•] High thermal conductivity. [•] High activity and selectivity. [ABSTRACT FROM AUTHOR]

Abstract: A cobalt based Fischer–Tropsch synthesis (FTS) catalyst, supported on a carbon nanofibers/carbon felt composite (Co/CNF/CF) was studied in situ at realistic conditions. The catalyst was monitored by X-ray absorption spectroscopy (XAS), high-resolution X-ray powder diffraction (HR-XRPD) and Raman spectroscopy, while changes in the gas phase were observed by mass spectrometry (MS). Transmission electron microscopy (TEM) was also applied to characterise the catalyst. The catalyst has a bimodal particle size distribution and exhibits a high deactivation rate. During the in situ study the catalyst appears to reduce further at the induction period of FTS, while crystallite growth is been detected in the same period. At steady state FTS the amount of metallic Co is constant. A change in the volumetric flow towards higher conversions did not affect the degree of reduction or the crystallite size of the catalyst. Post-treatment at 400°C under H2 atmosphere leads to sintering of the cobalt particles, while a CO treatment followed by H2 treatment creates a catalyst rich in hexagonal close packed cobalt through the formation of a Co2C intermediate. [Copyright &y& Elsevier]

Abstract: First-principles calculations have been performed to examine the effect of doped Ag on the kinetics of Ni-catalyzed methane dissociation and coke formation. The close-packed Ag/Ni(111) and stepped Ag/Ni(211) surfaces as well as the defect facets with step sites blocked by Ag or C atoms are constructed to investigate the role of the coordinatively unsaturated sites in the catalytic performance of Ni nanoparticles. The most stable CH x (x =0–4) adsorption configurations and transition states for methane dissociation have been identified on both Ni and Ag/Ni surfaces. The calculated results indicate that the activation energy for methane dissociation is increased with the Ag coverage on Ni(111), and the C atoms deposited on the catalyst surface can be readily separated into small islands by Ag. On Ni(211) Ag atoms are predicted to bind preferentially to the middle-step sites which act as the nucleation center for the growth of filamentous carbon and therefore have the potential to prevent catalyst particles from being destroyed. Meanwhile, as the energy barrier for methane dissociation on the Ag-blocked Ni(211) surface is even higher than that on pure Ni(111), the active center is transferred from the stepped surface to the close-packed surface. These findings provide a rational interpretation of the experimental observations that Ag/Ni catalyst exhibits lower catalytic activity towards steam methane reforming but high resistance to coke deposition. [Copyright &y& Elsevier]

Abstract: A novel approach to synthesize platelet carbon nanofibers (PCNFs) is proposed by taking advantage of the flat interfaces between Fe nanoparticles and flake supports. PCNFs are produced when Fe nanoparticles are supported on flakes of mica, SiO2 and graphite, and only fishbone carbon nanofibers (FCNFs) are obtained when γ-Al2O3 is used as a support. The crystalline perfection of PCNFs is found to depend on the dispersion of the catalyst and the surface roughness of the support. Perfect PCNFs are obtained when mica, which has a high surface tension and a very flat surface, is used as a support. The yield of PCNFs changes little with the nature of the support but is strongly related to the size of Fe nanoparticles and the preparation method of the Fe catalysts. [Copyright &y& Elsevier]

Abstract: A series of Zr x Ce1−x O2–Al2O3 (x =0, 0.25, 0.5, 1) nanocomposites were prepared through a citric acid mediated route. The thermal stability of these materials was investigated by calcination at temperatures between 1173 and 1473K for a certain time. The nanocomposites were characterized by XRD, DTA, nitrogen adsorption–desorption measurements, Raman spectroscopy, TEM and SEM. It was found that coating Zr x Ce1−x O2 on the surface of Al2O3 could substantially enhance the thermal stability of the composites, as evidenced by preventing the formation of α-Al2O3. Rh/Zr x Ce1−x O2–Al2O3 catalysts were prepared by incipient wetness impregnation, followed by calcination at 1173K for 5h. The Rh dispersion was measured by volumetric H2-chemisorption. The effect of the catalyst support, the reaction temperature, the Rh loading and the gas hourly space velocity in the catalytic partial oxidation of methane was studied in a quartz fixed-bed reactor, concerning activity, selectivity and stability. The ignition and extinction behaviors of the reactor on different catalysts were also investigated showing that the ignition temperature depends significantly on the composition of the supports. It was observed that the presence of cerium in the composites would lower the ignition temperature and enhance the activities of methane partial oxidation and water gas shift reaction. [Copyright &y& Elsevier]

Abstract: Combined UV Raman spectroscopy using radiation of 325nm, visible Raman spectroscopy excited by 633nm laser, X-ray diffraction and nitrogen adsorption–desorption surface area measurements were used in the present work to investigate the mechanism of the phase transformation and sintering of ZrO2–Al2O3 and CeO2–Al2O3 nanocomposites synthesized by a nanoparticle-mediated Pechini sol–gel method. These materials were compared to pure alumina, ZrO2 and CeO2 nanoparticles calcined at different temperatures. The modification of the alumina surface with CeO2 and ZrO2 can significantly delay the phase transformation and sintering. UV Raman spectroscopy is found to be more sensitive at the surface region for the ZrO2–Al2O3 and CeO2–Al2O3 nanocomposites, making possible to study the phase changes of the additional oxide. A synergetic stabilization effect between two oxides such as Al2O3 and ZrO2 or CeO2 was found, where the phase transformation and sintering of both oxides were delayed. The results reveal the role of the second oxides in the nanocomposites in suppressing surface-mediated sintering thus gaining a higher stability of the materials at high temperatures. [Copyright &y& Elsevier]

Abstract: Au catalysts have been prepared (i) on TiO2, (ii) on carbon nanofibres (CNF) and (iii) on TiO2 deposited onto CNF. Catalysts prepared from deposition-precipitation (DP) and from colloid solutions have been characterised using XRD, TEM, TGA and XAS and tested in the water–gas shift (WGS) reaction. DP yields large Au particles (>50nm) on CNF-containing supports. High Au dispersion on carbon nanofibres requires preparation via other methods such as colloid formation. Au particle growth is more pronounced during the synthesis steps than during thermal treatments. This increase is not observed for the Au particles on TiO2 but only when CNF is present, indicating that the surface properties of TiO2 are altered by the CNF. TiO2 XANES analyses show that distortions in the lattice symmetry of TiO2 are introduced when the oxide is deposited on CNF. The distortion of the TiO2 structure by the CNF may also introduce changes that promote the turnover frequencies. The WGS activity significantly improves when titania is present. This shows that coexistence of Au and TiO2 is needed to obtain high catalytic activity in the WGS reaction, indicating that the active sites are either on the Au–TiO2 interface or that the reaction follows a bifunctional mechanism. [Copyright &y& Elsevier]

Abstract: The kinetics of CO2 sorption on a solid adsorbent, namely lithium zirconate, have been studied in an oscillating microbalance. The solid sorbent has been prepared by a novel route resulting in a high capacity, good stability and much improved sorption rates, making it suitable for its application in sorption enhanced hydrogen production by steam methane reforming. A kinetic equation for the sorption kinetics as a function of CO2 partial pressure and temperature has been developed. The hydrogen production by sorption enhanced reaction process has been simulated by a dynamic one-dimensional pseudo-homogenous model of a fixed-bed reactor, where a hydrotalcite-derived Ni catalyst has been used as steam reforming catalysts. Simulation results show that hydrogen purer than 95% with a concentration of carbon monoxide lower than 0.2mol% can be produced in a single step. [Copyright &y& Elsevier]

Abstract: In order to investigate the effect of cerium oxide on Cu–Zn-based mixed-oxide catalysts four catalyst samples were characterized by means of XRD, in situ XANES and thermogravimetric analysis. The activity of the catalyst samples was tested for the forward water–gas shift reaction. Cerium oxide was found to increase the crystallinity of the ZnO phase indicating a segregation of the Cu and ZnO phases. The TOF of the water–gas shift reaction based on chemisorption data was found to be independent of composition and preparation conditions of the four catalyst samples. In contrast, the catalyst stability depends on composition and preparation conditions. Cerium oxide impregnated before calcination of the hydrotalcite-based Cu–Zn precursors leads to a more stable water–gas shift catalyst. [Copyright &y& Elsevier]