Search

Aiming at enhancing the coke resistance of Ni-based catalysts, the Nd-doped Ni@A 2 O 3 core-shell catalysts were prepared and their catalytic performance was evaluated in the steam reforming of acetic acid (SRAA). The catalysts were characterized by BET, XRD, XRF, HRTEM, H 2 -TPR, NH 3 -TPD, and DTG. The catalytic performance was greatly enhanced by the incorporation of Nd, with decreased yields of CO, CH 4 , and acetone, increased yield of CO 2 , and remarkable carbon resistance. The decoking behavior of the spent catalyst was elucidated by H 2 O18-TSD. A low reaction temperature facilitates the formation of amorphous carbon, leading to catalyst deactivation. The decoking ability of the catalyst is greatly improved by the Nd incorporation but is also catalyzed by the exposed Ni surface. The Ni0.01Nd@Al catalyst greatly balanced the exposed Ni surface and the mobile lattice oxygen, showing the highest catalytic activity, lowest coke deposition, and superb decoking ability. • OSC was introduced to Ni@Al 2 O 3 core-shell catalyst by doping Nd. • Hydrogen yield was enhanced by Nd incorporation with remarkable coke resistance. • Low temperatures induced the formation of amorphous carbon. • Lattice-oxygen-involved surface reactions promoted coke removal and water dissociation. • Both the Ni and lattice oxygen affected the water decoking behavior. [ABSTRACT FROM AUTHOR]

The catalytic transesterification of vegetable oil over heterogeneous catalysts is an effective approach for biodiesel production. To elucidate the role of MgO in catalyzing this reaction, several CaO-MgO catalysts with various Mg/Ca ratios were synthesized by co-precipitation. The catalysts were characterized by BET, XRD, SEM, HRTEM, FTIR, TGA, CO2-TPD, O2-TPO, and in situ DRIFTS. The catalytic performance in the transesterification of soybean oil with methanol was evaluated in a stirred batch reactor. The results indicated that the synthesized pure MgO had weak basic sites and poor pore structure, showing the lowest activity. The added Mg in the CaO-MgO composites was present in both doped and supported forms. The doped Mg reduced the lattice spacing of CaO, improved the intensity and number of basic sites, and enhanced the activity of catalysts, while the supported Mg hindered the diffusion of reactants to the basic sites. The amount of the doped Mg showed a maximum value due to the solubility nature of CaCO3 and MgCO3. 1Mg3Ca (Mg/Ca=1/3) exhibited the highest activity with a biodiesel yield of 92.28% at 60 °C for 2 h. CaO is sensitive to water and CO2, forming hydroxides and carbonates. The supported MgO with a low porous structure well protected the basic sites from contamination. High-temperature treatment is an effective method to remove the contaminates and the removal temperature increases in the order of H2O < Mg(OH)2 < Ca(OH)2 < CaCO3. [ABSTRACT FROM AUTHOR]

Ti-inserted ordered mesoporous silica SBA-15 (Ti-SBA-15) synthesized by original microwave-assisted method as a support was used to prepare CoMo catalysts to develop a new catalyst with high hydrodesulfurization (HDS) and controlled hydrodearomatization (HDA) activities. The activity tests of catalysts were carried out by using a pressurized fixed-bed flow reactor. 4,6-Dimethyldibenzothiophene (4,6-DMDBT), 1-methylnaphthalene, and phenanthrene were used as model reactants in HDS and HDA, respectively. CoMo/Ti-SBA-15 catalyst showed about 1.35 times of HDS activity and half of HDA activity of CoMo/SBA-15 catalyst. The results of XRD, FT-IR and 29 Si-NMR reveal that titanium was successfully inserted into silica framework of SBA-15, and the SBA-15 mesoporous structure was maintained after insertion of titanium. The reduction of molybdenum from Mo 6+ to Mo 4+ readily occurred with incorporation of titanium, resulting in an increase in Mo 4+ species and CoMoS phase on sulfided catalysts. This enhanced the HDS activity of CoMoTiSBA15 catalyst. Moreover, the presence of Ti 3+ on CoMo/Ti-SBA-15 was observed, suggesting that TiMoS was formed and played a role as new active sites. CoMoS active slabs with shorter length and higher stacking layer were formed on CoMo/Ti-SBA-15 comparing with CoMo/SBA-15, resulting in the low HDA activity of the former. [ABSTRACT FROM AUTHOR]

Highlights: [•] NiMo/SAPO-11 is active in simultaneous hydrodeoxygenation and hydroisomerization. [•] NiMo/AlSBA-15 exhibit strong cracking activity. [•] Hydroisomerization on NiMo/SAPO-11 and NiMo/AlSBA-15 occurs via different routes. [•] Acidity as well as structure affects isomerization of long chain molecule. [Copyright &y& Elsevier]

A series of solid base catalysts were prepared with several alkali and alkaline earth metal species. The catalysts were used in one-stage synthesis processes of polysulfides using diisobutylene (DIB), sulfur, and hydrogen sulfide (H2S). The possibility of using solid base catalyst as an alternative for a liquid amine catalyst and the effects of preparation conditions on the catalytic activity were discussed. Alumina-supported potassium catalysts showed a catalytic activity comparable to that of dicyclohexylamine. The alkali metal catalysts proved to be more effective than alkaline earth metal catalysts. Further, a three-stage mechanism for polysulfide synthesis using the system of diisobutylene, sulfur, and hydrogen sulfide in the presence of solid base catalysts was suggested. Moreover, a novel [14C]CO2 radioisotope pulse tracer method was developed to determine the amount of CO2 adsorption on solid base catalysts at the temperatures between 100–400 °C and under 0.6–3.1 MPa. The relationship between the uptake amount of CO2 on the alkali metal catalysts and the catalytic activity in syntheses of polysulfides was discussed. [Copyright &y& Elsevier]

In order to investigate the behavior of sulfur on sulfided Ni-Co-Mo/Al2O3 catalyst in the ultra deep hydrodesulfurization (HDS), a novel radioactive 35S tracer method was developed. Both radioactive 35S-labeled elemental sulfur and dibenzothiophene (DBT) were used to label the catalyst under the practical HDS, and then HDS reactions of DBT of 0.001–1.0 wt.% (content of sulfur: ca. 2–200 ppm) were carried out over the 35S-labeled catalyst at 260 °C and under 5.00 MPa. By tracing the changes in the radioactivity of formed [35S]H2S, the behavior of sulfur on the catalyst was determined. Either [35S]S or [35S]DBT can be used to label the catalyst well and the behavior of sulfur on the catalyst did not change with the type of 35S agent. The release rate of [35S]H2S from 35S-labeled catalyst in the HDS of DBT became remarkably slow when the concentration of DBT decreased to less than 0.01 wt.%. The amount of labile sulfur participating in the HDS of DBT also decreased with decreasing the concentration of DBT. This indicates that the labile sulfur on the catalyst is not uniform and only some part but not all of labile sulfur participates in the ultra deep HDS. [Copyright &y& Elsevier]

Graphene oxide, which exhibits extraordinary acidic properties and a high theoretical surface area, is a good candidate for the catalytic transformation of biomass resources to valuable chemicals and biofuels. In this study, graphene oxide was prepared through various graphite oxide exfoliation methods, including sonication, microwave irradiation, and freeze-thaw cycling, and the activity of the prepared catalysts was evaluated in the saccharification of cellulose. The results indicated that graphene oxide prepared via these methods exhibited superior catalytic performances compared to graphite oxide; however, no significant difference in the catalytic activity of the graphene oxide catalysts was observed based on the exfoliation method used. Therefore, we proposed that thinning of graphite oxide improves its catalytic activity by increasing the contact efficiency between the substrate and the catalyst; however, this is not dependent on the exfoliation method used to prepare the graphene oxide. [ABSTRACT FROM AUTHOR]

Graphene oxide, which exhibits extraordinary acidic properties and a high theoretical surface area, is a good candidate for the catalytic transformation of biomass resources to valuable chemicals and biofuels. In this study, graphene oxide was prepared through various graphite oxide exfoliation methods, including sonication, microwave irradiation, and freeze-thaw cycling, and the activity of the prepared catalysts was evaluated in the saccharification of cellulose. The results indicated that graphene oxide prepared via these methods exhibited superior catalytic performances compared to graphite oxide; however, no significant difference in the catalytic activity of the graphene oxide catalysts was observed based on the exfoliation method used. Therefore, we proposed that thinning of graphite oxide improves its catalytic activity by increasing the contact efficiency between the substrate and the catalyst; however, this is not dependent on the exfoliation method used to prepare the graphene oxide. [ABSTRACT FROM AUTHOR]

5-Hydroxymethylfurfural (HMF) is one of the most important intermediate platforms for production of both chemicals and liquid fuel derived from biomass. The one-pot production of HMF from cellulose was conducted in a batch reactor in the presence of various solid acid catalysts. The prepared catalysts were characterized by means of Brunauer–Emmett–Teller measurement and pyridine adsorption FT-IR to investigate their pore structure and acidic properties. The presence of gaseous hydrogen enhanced the formation of HMF by suppressing the formation of byproducts. Increasing the acid amount of the catalyst caused an increase in the conversion and selectivity for organic acid and a decrease in the HMF selectivity. A Brønsted-type catalyst (Al-SBA-15) favored the formation of HMF. The reaction conditions of 220 °C, 5 min, and a hydrogen pressure of 1 MPa resulted in the highest yield of HMF, and selectivity of 26.9% was achieved when the Al-SBA-15 catalyst was used. Moreover, under the same conditions, cellulose extracted from eucalyptus, a practical biomass, was converted to HMF in a one-pot synthesis with a yield of 13.0 C-mol.%. [ABSTRACT FROM AUTHOR]

SAPO-11 zeolite-supported PtSn bimetallic catalysts (PtSn/SAPO-11) were prepared using a co-impregnation method for simultaneous selective hydrodeoxygenation of methyl palmitate and isomerization of deoxygenated hydrocarbons. The PtSn catalyst exhibited high isomerization activity and hydrodeoxygenation selectivity, and was superior to the monometallic Pt/SAPO-11 catalyst. The Pt/SAPO-11 catalyst was more active for C C bond cleavage, resulting in a considerable formation of C 15 hydrocarbons. The PtSn/SAPO-11 catalyst was more efficient for C O bond hydrogenation, affording higher selectivity to C 16 hydrocarbons. In the studied PtSn catalyst, the platinum content was constant at 0.3 wt% and the atomic ratio of Sn/Pt was varied from 1 to 3. The result of the catalytic test suggests that it is necessary to control tin surface density in order to obtain a well-balanced Pt–SnO 2− x function and a Pt–Sn alloy as well. The highest performance in the tandem hydrodeoxygenation–isomerization of methyl palmitate was observed at the Sn/Pt ratio of 2; for this catalyst, the isomerization yield obtained at 375 °C was 4 times higher than the monometallic Pt catalyst. After tin addition, Pt nanoparticles were highly dispersed on the support with an average size of ∼4 nm. HRTEM observations and FT-IR studies of CO adsorption indicate that a portion of Sn interacted with Pt, forming Pt–Sn alloys; other Sn species were formed in the form of tin oxides, likely SnO 2− x (0 < x < 2), and were mainly present on the periphery of Pt nanoparticles. The occurrence of SnO 2− x species is crucial for the hydrodeoxygenation pathway; however, excessive addition of tin would block the Pt and PtSn active sites, resulting in a decrease in the catalytic activity. The presence of Pt–Sn alloys is the most remarkable reason for its high isomerization activity. [ABSTRACT FROM AUTHOR]

To develop a non-sulfide and non-noble metal catalyst for the one step deoxygenation and isomerization of methyl laurate to hydrocarbons that are identical to diesel fuel, a SAPO-11 supported reduced nickel and molybdenum catalyst was prepared, and its performance was investigated after reduction pretreatment at various temperatures (400–550 °C). For comparison, sulfided NiMo/SAPO-11, reduced NiO/SAPO-11 and MoO 3 /SAPO-11 were also studied. The reduction temperature exerted a significant influence on the deoxygenation activity, isomerization selectivity and deoxygenation pathway. The NiMo 3- x /SAPO-11 catalyst that was reduced at a lower temperature (400 °C) exhibited low deoxygenation activity but the highest isomerization selectivity. However, the activity subsequently increased over the catalyst reduced at 450 °C, and was higher than that of the sulfided catalyst. In addition, the isomerization selectivity decreased with increasing reduction temperature. The high activity and isomerization selectivity are ascribed to the increase in the density of surface species of Mo 4+ and Mo 5+ , respectively. With regard to the deoxygenation pathway, the catalyst reduced at 400 °C exhibited a high decarbonylation selectivity that was similar to the nickel-catalyzed reaction. In contrast, the synergetic effect of the nickel metal and Mo 4+ species can be responsible for the high selectivity toward hydrodeoxygenation over the catalyst reduced at higher temperatures (450–550 °C). [ABSTRACT FROM AUTHOR]

Eukaryotic sialyltransferases play key roles in many physiological and pathological events. The expression of active human recombinant sialyltransferases in bacteria is still challenging. In the current study, the genes encoding human N -acetylgalactosaminide α2,6-sialyltransferase V (hST6GalNAc V) and N -acetylgalactosaminide α2,6-sialyltransferase VI (hST6GalNAc VI) lacking the N -terminal transmembrane domains were cloned into the expression vectors, pET-32a and pET-22b, respectively. Soluble and active forms of recombinant hST6GalNAc V and hST6GalNAc VI when coexpressed with the chaperone plasmid pGro7 were successfully achieved in Escherichia coli. Further, lactose (Lac), Lacto- N -triose II (LNT II), lacto- N -tetraose (LNT), and sialyllacto- N -tetraose a (LSTa) were used as acceptor substrates to investigate their activities and substrate specificities. Unexpectedly, both can transfer sialic acid onto all those substrates. Compared with hST6GalNAc V expressed in the mammalian cells, the recombinant two α2,6-sialyltransferases in bacteria displayed flexible substrate specificities and lower enzymatic efficiency. In addition, an important human milk oligosaccharide disialyllacto- N -tetraose (DSLNT) can be synthesized by both human α2,6-sialyltransferases expressed in E. coli using LSTa as an acceptor substrate. To the best of our knowledge, these two active human α2,6-sialyltransferases enzymes were expressed in bacteria for the first time. They showed a high potential to be applied in biotechnology and investigating the molecular mechanisms of biological and pathological interactions related to sialylated glycoconjugates. • Functional human 2,6-sialyltransferase hST6GalNAc V/VI were successfully expressed in Escherichia coli. • The recombinant hST6GalNAc V/VI displayed flexible substrate specificity and lower enzymatic efficiency. • Human milk oligosaccharide disialyllacto-N-tetraose (DSLNT) can be synthesized by both hST6GalNAc V/VI. [ABSTRACT FROM AUTHOR]

Abstract: Ceria-supported chromium, molybdenum, and tungsten catalysts were prepared by impregnation. The prepared catalysts were characterized using N2 adsorption, X-ray diffraction (XRD), the temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS) measurements. The catalytic activity in CO hydrogenation was evaluated using a fixed-bed pressurized flow reaction system under the following conditions: 260–300°C, 5.0MPa, GHSV of 5000h−1, and a H2/CO ratio of 1.0–2.0. The effects of ceria support, group VI metals, and catalyst activation methods on C2+ alcohol synthesis were investigated. The use of ceria supports resulted in a decrease in the selectivity for CO2, and in increases in the selectivity for C2+ alcohols and CO conversion. The selectivity for alcohols on the Mo-based catalysts was higher than those on the corresponding Cr or W-based catalysts. A comparison of the methods of activation for the K005Co0620MoCe catalyst demonstrated that sulfidation produced the highest CO conversion and selectivity for C2+ alcohols, as well as the lowest, hydrocarbon selectivity. XPS and H2-TPR measurements show that the mixed metal sulfide phases, e.g., the Co–Mo–S phase, and the thiol group on the catalysts enhanced the formation of C2+ alcohols. [Copyright &y& Elsevier]

Hydrotreatment of jatropha oil over a series of sulfidedNiMo/SiO2–Al2O3and NiMo/ZSM-5–Al2O3catalysts in a fixed-bed reactor was carriedout. Effect of support on various reactions occurring in hydrotreatmentwas investigated. For NiMo/SiO2–Al2O3series catalysts, the rates of decarboxylation and/or decarbonylationincreased with increasing Si/(Si+Al) ratio, while the ratio of hydrodeoxygenationdecreased with increasing Si/(Si+Al) ratio. For NiMo/ZSM-5–Al2O3series catalysts, with increasing amounts ofZSM-5, the rate of decarboxylation and/or decarbonylation versus hydrodeoxygenationdid not change. These results could be attributed to the total acidicsites of catalyst having a positive effect on the decarboxylationand/or decarbonylation pathways. NiMo/SiO2–Al2O3catalysts showed a much higher isomerization/crackingratio than NiMo/ZSM-5–Al2O3catalysts.It was suggested that isomerization reaction was favorable for weakand middle acidic sites but cracking reaction was favorable for strongacidic sites. [ABSTRACT FROM AUTHOR]

The first part of this paper deals with the morphology of the MoS2 phase and its oxide precursor, the MoO3 phase, mainly from a geometrical point of view. After giving a brief review of the literature describing the structure of these compounds, Mo densities in both phases were calculated along various crystallographic planes. Further, using structural models recently proposed by others, Mo densities in MoS2 were also calculated in the case of an epitactic growth on γ-Al2O3 and TiO2 model surfaces. Then, the calculated Mo densities were compared with experimental results (Mo density when HDS activity is maximal) previously obtained for catalysts constituted of MoS2 supported on a low SSA TiO2, a high SSA TiO2 and a conventional γ-alumina. It was suggested that either on alumina or titania the MoS2 phase is growing as (100) MoS2 planes. However, while on the alumina the optimal MoS2 phase might be constituted of dispersed MoS2 slabs covering only a part of the alumina surface (2.9–3.9 Mo atoms/nm2), on titania the optimal MoS2 phase might be constituted of a uniform MoS2 monolayer (5.2 atoms/nm2 for the high SSA titania, which is equal to the Mo density of a perfect MoS2 (100) plane). This difference may originate in the creation of a 'TiMoS' phase enhancing the S atoms mobility over Mo/TiO2-sulfided catalysts. Indeed, while in the case of a γ-alumina carrier the active sites (labile S atoms) are located on the edge of MoS2 slabs making the ratio Moedge/Mototal a crucial parameter for the catalytic performances, in the case of a titania carrier the labile sulfur atoms might be statistically distributed all over the TiMoS active phase. Further, the higher Mo density observed over the high SSA titania (5.2 atoms/nm2) when compared to that over the low SSA titania (4.2 atoms/nm2) was supposedly due to the pH-swing method advantageously used to prepare the former carrier. Indeed, this method allows giving a solid with enhanced mechanical properties providing a good stability to the derived catalysts under experimental conditions. In addition, this TiO2 carrier exhibits a great homogeneity, with a surface structure substantially uniform, which might be adequate for a long-range growth of (100) MoS2 slabs. [ABSTRACT FROM AUTHOR]

The first part of this paper is a short review of the [sup 35]S radioactive tracer methods developed in recent years. Then, the experimental results obtained so far on Mo/Al[sub 2]O[sub 3] catalysts are compared with computer simulation results recently claimed in order to elucidate the coordinatively unsaturated site (CUS) creation/replenishment/ regeneration mechanism over MoS[sub 2] crystallites. The computer simulations allowed us to pre-select thermodynamically acceptable mechanisms among a set of suggested ones. Then, by comparison of the calculated activation energies with the [sup 35]S experiments results we could further validate the most probable mechanism. This mechanism involved the dissociative adsorption of an H[sub 2] molecule on the metallic edge of a MoS[sub 2] crystallite surface with further creation of a CUS by release of one H[sub 2]S molecule in the gas phase. Both laboratory and computer simulated experiments permitted to calculate the activation energy for the H2S liberation reaction. In both cases, this energy was about 10- 12 kcal/mol, confirming the accuracy of the proposed mechanism. Moreover, the calculated activation energy of the rate-limiting step for the creation of one CUS by the proposed mechanism was about 23 kcal/mol, which was also in good agreement with the experimental activation energy of the dibenzothiophene (DBT) hydrodesulphurisation (HDS) reaction (typically about 20- 22 kcal/mol). This correlation indicated that the DBT HDS reaction rate might be intrinsically governed by the CUS formation/replenishment process, i.e. that the vacancy formation process is a crucial parameter in the global HDS reaction mechanism. Nevertheless, in the case of the 4,6-dimethyl DBT (4,6-DMDBT) HDS reaction, the experimental activation energy is higher (approx. 30 kcal/mol), confirming that external parameters induced by the 4,6-DMDBT-specific properties themselves are likely to play an important role in the reaction process, in addition to the ones intrinsic to the catalytic phase. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-solvent changed the Hansen solubility parameter (HSP) and enhanced lignin solvation. • Co-solvent systems efficiently inhibited the repolymerization of lignin fragments. • The liquid product yield increased from 12.3 % in an aqueous solution to 19.8 % in an H 2 O-THF (v/v: 1/1) system. Efficient low-boiling-point co-solvent systems were developed for the oxidative depolymerization of lignin to high-value platform chemicals, mainly vanillin and lactic acid, using molybdenum (Mo)-based solid oxide catalysts and hydrogen peroxide (H 2 O 2) oxidant. The co-solvent, designed with the matching Hansen solubility parameter (HSP) values to lignin, facilitated efficient solvation of lignin. Various factors, including co-solvents, catalyst supports, H 2 O 2 concentrations, and active metals, were detailly investigated. Optimal yields of total liquid products (EA oils: 19.8 %) were obtained in water-tetrahydrofuran (H 2 O-THF) co-solvent systems, increased by 61.0 % compared to that of the sole aqueous solution, employing a MoO 3 /Al 2 O 3 catalyst. Additionally, the oxidized lignin (O-lignin) or EA oils was analyzed using UV–vis, CHN, GPC, and FT-IR techniques. Results indicated that the co-solvent system remarkably inhibited the repolymerization of lignin fragments, and enhanced the oxidative cleavage of lignin side chains. Lastly, a hypothetical mechanism explained the reaction pathway of lignin depolymerization in co-solvent systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • A continuously catalytic system was developed for lignin oxidative depolymerization in a near-neutral aqueous solution. • Heterogeneous Mo-based catalysts combined with H 2 O 2 increased the selectivity and yield of main platform products. • The acid properties of solid catalysts influenced vanillin and lactic acid yields. • A hypothetical mechanism was proposed to elucidate the formation pathways of vanillin and lactic acid based on the results of lignin model compounds. A heterogeneous molybdenum (Mo)-based oxide catalyst system in combination with hydrogen peroxide as an oxidant was developed for oxidative depolymerization of lignin to yield high-value platform chemicals in a nearly neutral aqueous solution. The impact of various reaction conditions, including the ratios of H 2 O 2 and/or MoO 3 /Al 2 O 3 catalyst to lignin, reaction temperature and duration, and lignin concentration, were investigated in a batch system or a continuous flow fixed-bed system. The structural changes between dealkaline lignin and the recovered lignin (O-lignin and M−lignin) were analyzed using UV–vis, FT-IR, and GPC techniques. The combination of MoO 3 and H 2 O 2 resulted in a superior peroxo complex, promoting the formation of vanillin and lactic acid. The medium and weak acid feature of MoO 3 /Al 2 O 3 catalyst induced the highest vanillin yield (5.6%) and the selectivity (86.9%) of main platform products. However, the highest yield of lactic acid (3.4%) was observed on MoO 3 /SiO 2 with more weak acid sites. Hypothetical formation mechanisms for vanillin and lactic acid were proposed based on the depolymerization of lignin model compounds. [ABSTRACT FROM AUTHOR]

To obtain a novel catalyst with high resistances to metal sintering and coke formation in the steam reforming of acetic acid, a series of nickel core-shell catalysts were prepared. The effects of the shell thickness, shell species and core particle size on the catalytic activity in the steam reforming of acetic acid were investigated. The prepared Ni@SiO 2 , Ni@Al 2 O 3 , Ni@CeO 2 and Ni@TiO 2 catalysts were characterized by BET, XRD, H 2 -TPR, DTG and HRTEM. The prepared core-shell catalysts showed high resistances to nickel sintering, owing to the protection of the shells, in comparison with bare nickel particles. Ni@SiO 2 with a thin shell showed a higher activity than the corresponding catalyst with a thick shell due to the thin silica shell allowing the facile diffusion of reactants and products. Because of the important role of the support in steam reforming reactions, the shell species greatly affected the catalytic activity in the steam reforming of acetic acid. It was demonstrated that an alumina shell was best suited for the steam reforming of acetic acid among the studied shells owing to its excellent water dissociation ability. The Ni@Al 2 O 3 - i catalyst showed excellent activity with an almost complete conversion and a hydrogen yield up to 91.2% at 750 °C due to its much smaller nickel particle size. The coke formed on the spent core-shell catalysts after the activity tests was mainly graphic carbon, and the Ni@Al 2 O 3 - i catalyst exhibited a superior coke resistance with the smallest amount of formed coke. HRTEM results of Ni@Al 2 O 3 - i indicated the alumina shell had a high hydrothermal stability and further confirmed the high sintering resistance in the steam reforming of acetic acid. [ABSTRACT FROM AUTHOR]

A series of Ni@Al 2 O 3 core-shell catalysts with ceria added to the surface of Ni nanoparticles or inside the alumina shell were prepared, and the effect of ceria addition on the performance of the catalyst in the steam reforming of acetic acid was investigated. The prepared catalysts were characterized by BET, XRD, HRTEM, H 2 -TPR and DTG. The addition of ceria to the surface of nickel nanoparticles greatly enhanced the activity of catalyst owing to the presence of the mobile oxygen, which migrated from the ceria lattice. Among the prepared catalysts, the Ni@Al10Ce catalyst showed the highest activity with a conversion of acetic acid up to 97.0% even at a low temperature (650 °C). The molar ratio of CO 2 /CO was also improved due to the oxidation of CO by the mobile oxygen into CO 2 . The coke formation on the core-shell catalysts was significantly inhibited by the addition of ceria to the surface of nickel nanoparticles due to the oxidation of carbon species by the mobile oxygen in the ceria lattice. However, the Ni@Al10Ce-a catalyst with ceria added to the alumina shell showed a low activity and the formation of a large amount of coke. It is suggested that only the ceria in close to the Ni surface has the promoting effect on the catalytic performance of the Ni@Al 2 O 3 catalyst in the steam reforming of acetic acid. [ABSTRACT FROM AUTHOR]

Ni Ru bimetallic catalysts with different amount of CeO 2 loaded on the γ-Al 2 O 3 support were prepared. The properties of catalysts were characterized by means of N 2 adsorption-desorption, XRD, H 2 -TPR and XPS techniques. Catalytic activities for the steam reforming of acetic acid over these catalysts were investigated at the temperature range from 650 °C to 750 °C. The addition of CeO 2 dramatically improved the activity and stability of the catalyst. Among these catalysts, the NiRu/10CeAl catalyst showed the highest catalytic activity as well as a good stability owing to the abundant Ce 3+ on the surface of catalyst. The existence of Ce 3+ promoted the formation of CO 2 from CO because of the mobilizable oxygen, which was favorable for the formation of hydrogen. The coke amount and species deposited on the catalysts after the activity tests were analyzed by DTG. As expected, the NiRu/10CeAl catalyst showed the best resistance to carbon formation. The temperature stepwise steam decoking experiment of the spent catalysts was conducted to elucidate the relationship between the existence of Ce 3+ and the decoking abilities of various catalysts. It was verified that the existence of Ce 3+ significantly promoted the decoking abilities of the catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Base catalyzed depolymerization of lignin was studied in a continuous reactor system at low temperature (≤180 ℃). • Low concentration (<5 %) of alkaline ionic liquid N -allylpyridinium hydroxide ([APy]OH) as a co-solvent in ethylene glycol solution decreased feedstock viscosity and reduced the cost. • [APy]OH as a catalyst also presented a synergistic effect with alkali metal salt (NaCl) and exhibited high aromatics yield. • A hypothetical mechanism was proposed to explain the depolymerization pathway of lignin. A novel alkaline ionic liquids N -allylpyridinium hydroxide ([APy]OH) was successfully designed and developed as a catalyst and co-solvent with ethylene glycol in the continuous depolymerization of lignin. Various reaction conditions, like lignin concentration, water content, and reaction temperature, were investigated under atmospheric pressure. Ethylene glycol was used as main solvent and repolymerization inhibitor of the aldehydes produced. The combination of [APy]OH and alkali metal salts exhibited a good synergistic effect for lignin depolymerization. Then, the depolymerization of three different lignins, including dealkaline lignin (DA-lignin), alkaline lignin (A-lignin), and sodium lignosulfonate (S-lignin), were also studied. S-lignin exhibited the highest yields of total liquid products (21.3 %) and aromatics (10.7 %). The change in lignin structure after depolymerization was observed by means of FT-IR and DTG-DTA techniques. Lastly, a hypothetical pathway for lignin depolymerization was proposed based on the catalytic results of lignin model compounds (LMCs) with different linkages. [ABSTRACT FROM AUTHOR]

To obtain diesel fuels with high combustion properties from hydrotreatment of vegetable oils, inhibiting the formation of multibranched isomers (MuBI) is highly desirable. A core@shell structural ZSM-22@SiO 2 zeolite was designed to passivate external acid sites and promote the formation of monobranched isomers (MoBI), which have much higher cetane numbers than MuBI (>85 vs. <60). A series of ZSM-22@SiO 2 zeolites with different amounts of shell silica were synthesized through a facile crystal growth method. External acid sites could be successfully inactivated using the proposed method. Synthesized zeolites were used as supports for bifunctional catalysts in hydrodeoxygenation of methyl palmitate. The effects of the shell silica amount and SiO 2 /Al 2 O 3 ratio of the core zeolite were investigated. The MoBI percentage in total isomers increased from 71% to 95% at a reaction temperature of 300 °C. However, deoxygenation activity and isomerization selectivity decreased gradually with increasing amount of shell silica. Fourier transform infrared spectroscopy of CO adsorption combined with transmission electron microscopy demonstrated that Pt particles exposed more Pt(1 0 0) facets than Pt(1 1 1) facets in silica-coated catalysts. This could be the most likely reason for the decreased deoxygenation activity. The decrease in the number of Brønsted acid sites could be responsible for the lowered isomerization selectivity. Catalytic performance could be enhanced by reducing the SiO 2 /Al 2 O 3 ratio of core ZSM-22. Catalysts with lower SiO 2 /Al 2 O 3 ratios favored smaller Pt particles and exposed more active Pt(1 1 1) corner sites. Additionally, acid sites played an important role in the adsorption of oxygenates. [ABSTRACT FROM AUTHOR]

Highlight: [•] Hydroconversion of Jatropha oil into iso-paraffin was achieved in one catalytic step. [•] The medium acid sites in SAPO-11 increased with the increase of Si/Al ratio. [•] Hydrotreatment of Jatropha oil was performed at various LHSV and Si/Al. [•] The mechanism of hydroconversion of methyl oleate was investigated. [•] A reaction network for hydroconversion of Jatropha oil was suggested. [ABSTRACT FROM AUTHOR]

Abstract: Several Pt catalysts with various solid acid supports (SAPO-11, Al-SBA-15, and Al2O3) and various SAPO-11 supported active metal (Pd, Ni, Ru, Pt) catalysts were prepared and characterized using BET, XRD, XRF, CO pulse adsorption, and NH3-TPD techniques. Their catalytic performances in isomerization of hydrodeoxygenated jatropha oil were carried out using a fixed bed flow reactor system. All Pt/SAPO-11, Pt/Al-SBA-15, and Pt/Al2O3 catalysts showed high catalytic activity for isomerization of n-alkanes with long carbon chain. Especially over Pt/SAPO-11 catalyst, a high yield of iso-C10–18 up to 79.4% was obtained, which was attributed to the absence of strong acidic sites of Pt/SAPO-11 catalyst. With an increase in reaction temperature, Pt/SAPO-11 catalyst still showed a high ratio of monobranched iso-C10–18 to multibranched iso-C10–18, presumably because of its ordered microporous structure, which suppresses formation of multibranched product. The catalytic activity of SAPO-11 catalysts containing various active metals decreased in the order of Pt/SAPO-11>Pd/SAPO-11>Ni/SAPO-11>Ru/SAPO-11, which might be attributable to the difference of hydrogenation–dehydrogenation activity of these metals. [Copyright &y& Elsevier]

Three series of CoMo catalysts (MoO3: 6, 11, 16 wt.%) with various Co/Mo molar ratios were prepared by successive incipient wetness impregnations of a titania sample previously prepared by the pH swing method, which provides a TiO2 carrier with a high SSA (134 m2 g−1) and excellent mechanical properties. DBT HDS activity of the catalysts increased with addition of cobalt up to Co/Mo=0.4 and then decreased for higher ratios, irrespective of the Mo loading. The results of a [35S]DBT HDS method showed that S0, the amount of labile sulfur atoms, increased in parallel with the activity when adding Co up to a molar ratio of 0.4. In contrast, unlike on CoMo/Al2O3 catalysts, only a slight increase in kRE, the H2S release rate constant, was observed upon Co addition. This was due to formation of the TiMoS phase: while formation of Ti一S*一Mo bonds favorably induces an increase in sulfur mobility on Mo/TiO2 catalysts, electronic density on Mo atoms increases, which limits the promoting effect of Co on mobility of Sa sulfur atoms bridged between Mo and Co. Further, while the increase in HDS activity upon Co addition on a uniform MoS2 monolayer on TiO2 was in rather good agreement with the quantitative and kinetics data of the 35S tracer method, over MoS2 slabs on TiO2 this increase was larger than that expected from the results of the 35S tracer method. This was attributed to the presence of □* and □a CUS, i.e. catalytic sites that are not replenished with sulfur, at the steady state. A larger number of □* CUS was present at low Mo wt.% or for low Co/Mo. As these particular catalytic sites are in the form of CUS at the steady state, they are not accounted by the [35S] radiotracer method. This explains the differences observed between the experimental DBT HDS promotion and the promotion deduced from the increase in kRE and S0. [Copyright &y& Elsevier]

Abstract: We systematically monitored the hydrodesulfurization (HDS) activity of dibenzothiophene (DBT) and groups of substituted DBTs present in a SR-LGO over various noble metal catalysts (Ru, Rh, Ru-Rh, Pt, Pd and Pt-Pd) supported on alumina. The catalytic performances were compared to those obtained over a conventional CoMo catalyst. The Pd-based catalysts exhibited excellent HDS performances, especially for desulfurizing the refractory compounds. In particular, the 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS activity over the Pd or the Pd-Pt catalyst was equivalent to that over the CoMo catalyst. This was attributed to the exceptional hydrogenation (HYD) properties of the Pd-based catalysts, which enable desulfurization of the refractory compounds by considerably minimizing the effect of the steric hindrance due to their substituents. The synergetic effect observed on the bimetallic Pt-Pd system at low temperature for all the sulfur compounds was largely attenuated in the high temperature range, probably due to shifting of the HYD/dehydrogenation equilibrium to dehydrogenation. Despite a much lower metal loading (0.25wt.%), the performances of the Rh catalyst were superior to those of the optimized 16wt.% Ru catalyst. A synergetic effect was observed on the Ru-Rh catalyst, on which the DBT HDS activity was significantly enhanced compared to the activity of each corresponding monometallic catalyst. Further, we recently showed that the use of SiO2 or SiO2-Al2O3 as a support allows higher optimal Rh contents, making the Rh-based HDS catalysts even more promising. In brief, we obtained encouraging results, which showed for instance that the excellent properties of the noble metal catalysts in model HDS reactions are still observed during the HDS treatment of real feeds. [Copyright &y& Elsevier]

Abstract: By combining experimental results and computer simulations, we previously showed that the coordinatively unsaturated sites (CUS) formation over MoS2 is most likely to occur on the MoS2 metallic edge through the departure of an H2S molecule. In the present paper, we aimed at examining the H2S departure from MoS2 catalysts promoted with Co and Ni. The [35S]DBT HDS experiments results showed that over CoMoS/Al2O3 and NiMoS/Al2O3 catalysts, the activation energy of the H2S release reaction is essentially the same with respective values of 7.4 and 7.9kcalmol−1. Considering the H2S departure activation energy in the case of the non-promoted MoS2 surface (10–12kcalmol−1), this result illustrates the synergetic effect between Mo and Co or Ni in terms of CUS regeneration easiness. Further, preliminary computer simulations results showed that for S atoms bridged between Co atoms, a mechanism implying H2S departure from the metallic edge cannot be reasonably envisaged. Moreover, on the sulfur edge the H2S release activation energy is too high (∼13.5kcalmol−1) if we consider experimental results on CoMo/Al2O3 catalysts, but not incompatible with the experimental value obtained over Co/Al2O3 catalysts (ca. 10kcalmol−1), which suggests that the mechanism on the promoted catalysts differs from that on the un-promoted ones. [Copyright &y& Elsevier]

The effect of the Cs addition on the H2S inhibition and subsequently on the DBT HDS activity over Ru-based catalysts was investigated. In good agreement with a previous study, the HDS activity over a Ru catalyst containing cesium was much higher than that over the same Ru catalyst without cesium. On the other hand, the HDS activity of the Ru&z.sbnd;Cs catalyst was more inhibited by H2S than that of the Ru catalyst at 260 °C. Thus, kinetic parameters were calculated using a Langmuir–Hinshelwood model to determine the mechanism of the H2S inhibition over Ru and Ru&z.sbnd;Cs catalysts. We found that the heats of adsorption of DBT and H2S on the Ru&z.sbnd;Cs catalyst were higher than on the Ru catalyst, indicating that the sulfur-containing species adsorb more strongly on the catalyst containing cesium. Subsequently, the role of cesium in the Ru&z.sbnd;Cs catalyst on the DBT HDS activity was investigated by using 35S-tracer experiments. The results suggested that while the Ru&z.sbnd;Cs catalyst was more inhibited by H2S, the Ru&z.sbnd;S bonds were more stable on this catalyst than on the Ru catalyst. This Ru&z.sbnd;S bond stabilization was responsible for the stabilization of the active phase, which allowed creation of a greater amount of sulfur atoms potentially labile. Thus, that explained the better HDS activity over the Ru&z.sbnd;Cs catalyst than over the Ru catalyst, despite a greater H2S inhibition on the former. [Copyright &y& Elsevier]

Sulfidation of CrO3–Al2O3 catalysts (11.1, 16.6 and 22.2 wt.% CrO3) synthesized by incipient wetness impregnation method was monitored by a 35S radioisotope ([35S]H2S) pulse tracer in situ method. This original method permitted us a better understanding of these relatively poorly documented catalytic systems. Experiences confirmed that, in a first step, for temperatures inferior to 400 °C, CrSx species are progressively formed. Then, in a second step for a temperature near 400 °C, formation of Cr2S3 entities is achieved, leading to their decomposition into CrS. This showed that the catalytic phase morphology depends drastically on the sulfidation temperature. Moreover, it was found that the increase in DBT activity with the Cr content previously observed was due to a modification of the nature of the active phase and not to an increase in its quantity. Indeed, whilst the sulfur quantity that accumulated on the catalysts containing 11.1 and 22.2 wt.% CrO3 was almost the same, the DBT HDS activity of the latter was ∼50% higher. [Copyright &y& Elsevier]

Alumina-supported ruthenium–cesium catalysts were presulfided using [35S]H2S pulse tracer method to evaluate their sulfidation state. Subsequently, using these previously 35S-labeled catalysts, HDS reactions of dibenzothiophene (DBT) were performed and the mobility of 35S introduced during the presulfidation stage was investigated. The results showed that the amount of labile sulfur (S0) was much smaller than the total amount of sulfur accommodated on the catalyst (Stotal). DBT conversion and Stotal increased linearly with Ru content. In a second part, labile sulfur amount was also determined under the catalyst working conditions and different results were obtained. Indeed, when the catalysts were marked with [35S] and with [35S]DBT under HDS reaction conditions, the obtained labile sulfur quantities (S0A) were significantly higher than the ones measured during the presulfidation stage (S0). These results showed that the labile sulfur is not formed on RuCs catalysts until the HDS reaction proceeds, which is quite different from that reported before for Mo, Pt, or Pd systems. [Copyright &y& Elsevier]

We prepared activated carbon-based solid acid catalysts derived from coconut shells via chemical activation with phosphoric acid under air and subsequent sulfonation. Their catalytic activities were evaluated in the saccharification of cellulose, and the parameters required for the activation and sulfonation processes were investigated. A catalyst activating temperature of 400 °C was found to be optimal, and the catalyst treated with chlorosulfuric acid exhibited a similar monosaccharide yield to that treated with fuming sulfuric acid. The prepared catalysts were characterized by various analytical techniques. The catalysts exhibited high specific surface areas and micropore volumes but low external specific surface areas. The catalysts had high contents of acidic functional groups when low activating temperatures were employed. For these catalysts, the surface chemical structure had a more dominant effect on the catalytic activity than that caused by the porous texture, while high acidic group contents led to high catalytic activities. Unlabelled Image • Activated carbon-based solid acid catalysts were prepared from coconut shells. • Preparation was via chemical activation with phosphoric acid and sulfonation. • Lower activating temperatures yielded higher acid amounts. • A higher acid amounts contributed to a higher catalytic activity. [ABSTRACT FROM AUTHOR]