Search

Catalytic hydrogenation of nitroarenes is an industrially very important and environmentally friendly process for the production of anilines; however, highly chemoselective reduction of nitroarenes decorated with one or more reducible groups in a nitroarene molecule remains a challenge. Herein, a novel hybrid non‐noble iron‐based nanocatalyst (named as FeS2/NSC) was developed, which was prepared from biomass as C and N source together with inexpensive Fe(NO3)3 as Fe source through high‐temperature pyrolysis in a straightforward and cost‐effective procedure. Comprehensive characterization revealed that single‐phase pyrite FeS2 nanoparticles with precisely defined composition and uniform size were homogeneously dispersed on N,S‐codoped porous carbon with large specific surface area, hierarchical porous channels, and high pore volume. The resultant catalyst FeS2/NSC demonstrated good catalytic activity for hydrogenation of functionalized nitroarenes with good tolerance of various functional groups in water as a sustainable and green solvent. Compared with bulk pyrite FeS2 and other non‐noble metal‐based heterogeneous catalysts reported in the literature, a remarkably enhanced activity was observed under mild reaction conditions. More importantly, FeS2/NSC displayed exclusive chemoselectivity for the reduction of nitro groups for nitroarenes bearing varying readily reducible groups. [ABSTRACT FROM AUTHOR]

Copper nanoparticles exsoluted in situ under a reducing atmosphere at elevated temperatures are socketed into the parent copper phyllosilicate nanotubes and exhibit excellent catalytic performance and superior stability for the selective hydrogenation of various esters to alcohols. [ABSTRACT FROM AUTHOR]

Surfactant-free bimetallic Ni@Ag nanoparticles in mesoporous silica, SBA-15 prepared by simple wet co-impregnation catalyse hydrogenation of dimethyl oxalate to methyl glycolate or ethylene glycol in high yield. [ABSTRACT FROM AUTHOR]

Selective hydrogenation and hydrogenolysis of 5-hydroxymethylfurfural were performed with carbon nanotube-supported bimetallic NiFe (NiFe/CNT) catalysts. The combination of Ni and Fe in an appropriate atomic ratio of Ni/Fe (2.0) significantly increased the selectivity to 2,5-furandimethanol or 2,5-dimethylfuran depending on the reaction temperature. The selectivities to 2,5-furandimethanol and 2,5-dimethylfuran were as high as 96.1 % at 383 K and 91.3 % at 473 K, respectively. The characterization results confirmed that bimetallic particles with sizes less than 7 nm were formed on the catalyst. Several key molecules related to 5-hydroxymethylfurfural transformation were used to investigate the product distribution and reaction pathway. The results indicated that the formation of NiFe alloy species is beneficial to the selective cleavage of the CO bond. Recycling experiments showed that the catalyst can be easily separated with a magnet and reused several times without significant loss of activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • LaO x -modified CuSi-NT catalyst is prepared for CO 2 hydrogenation to MeOH. • LaO x -dopant stabilizes the surface Cu+/Cu0 ratio of CuSi-NT. • La/CuSi-NT benefits the formation of the HCOO* intermediate by CO 2 hydrogenation. • The catalyst can sustain 12% CO 2 conversion and 80% MeOH selectivity for at least 200 h. The use of Cu-based catalysts in CO 2 hydrogenation to methanol (MeOH) has attracted considerable attention due to their low reaction temperature, low cost, and high activity. However, Cu nanoparticles are usually sintered under high-H 2 atmosphere. The difficulty in keeping the Cu+/Cu0 ratio stable during the reaction leads to the instability of Cu-based catalysts. In this work, La oxide-doped Cu nanoparticles socketed into parent Cu phyllosilicate nanotubes (La/CuSi-NT) are synthesized by exsolution in situ under a reducing atmosphere at elevated temperatures. They are used to catalyze CO 2 hydrogenation to MeOH. Catalytic results show that the La/CuSi-NT catalyst is more stable than intact CuSi-NT and Cu-based catalysts prepared via traditional methods. Among the prepared catalysts, the 0.2La/CuSi-NT catalyst with the La/Cu molar ratio of 0.2 exhibits the highest MeOH yield of up to 428 mg g cat −1 h−1 and performance that remains stable for at least 200 h. Characteristic studies indicate that introducing a La promoter helps increase Cu+/Cu0 ratios and confirm that LaO x species favor generating the formate species of CO 2 hydrogenation. Therefore, MeOH synthesis through CO 2 hydrogenation is intensified over the La/CuSi-NT catalyst. [ABSTRACT FROM AUTHOR]

Highly stable dendrimer-encapsulated Pd nanoparticles in ionic liquids were prepared for the first time by using charged PAMAM dendrimers as templates, which could maintain hydrogenation efficiency for up to at least 12 recycles. [ABSTRACT FROM AUTHOR]

The selective transformation of biomass-derived 5-hydroxymethylfurfural (5-HMF) into value-added chemicals is of significant interest to both academia and industry. In this study, we report on the direct hydrogenation of 5-HMF to 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) instead of 2,5-dimethylfuran, achieving an impressive yield of 90.4% in 7 runs using a nickel phyllosilicate catalyst (Ni-PSL) under optimized conditions. The choice of solvent is crucial for minimizing side reactions, with tetrahydrofuran identified as an optimal solvent for reducing the formation of acetal by-products, which are typically promoted by protic organic solvents such as methanol or n -butanol. Pyridine–FTIR results reveal that the surface of Ni-PSL is enriched with Lewis acid sites, originating from coordinatively unsaturated Ni species, which are effectively generated through proper thermal treatment. Moreover, the total amount of acid sites in Ni-PSL can be modulated by adjusting the calcination temperature, without affecting the size of the Ni nanoparticles. These Lewis acid sites play pivotal roles in promoting the adsorption of the furan ring, thereby favoring the formation of BHMTHF under mild reaction conditions. However, an excess of Lewis acid sites promotes the cleavage of the C−OH bond, reducing the selectivity towards DMTHF. [Display omitted] • Ni-PSL is selected as ideal catalyst in 5-HMF hydrogenation yielding DHMTHF up to 90.4% in 7 runs. • The aprotic solvent like THF is beneficial to minimize by-products. • The surface acid of Ni-PSL can be regulated by thermal treatment. • Lewis acid sites enhance the adsorption of furan ring to produce DHMTHF as major product. [ABSTRACT FROM AUTHOR]

[Display omitted] • NaCl nanocrystals were used as a template for the synthesis of few layer MoS 2. • Sodium is able to promote the formation of in-plane sulfur defects. • The catalyst evolution throughout the induction period was studied in detail. • Sodium-assisted sulfur vacancies lower the energy barrier of the carboxylate route. The effective conversion of CO 2 to methanol utilizing green hydrogen under moderate conditions represents a promising approach for achieving carbon neutrality. MoS 2 demonstrates exceptional catalytic performance at temperatures below 200 °C, however, generating in-plane sulfur defects is challenging due to the intact planar structure. Introducing heteroatoms to induce sulfur vacancy formation and modulate their chemical environment remains a significant obstacle. In this study, we developed a NaCl-assisted method for synthesizing MoS 2 and discovered that a small quantity of sodium not only promotes the formation of sulfur vacancies during the induction period, but also encourages CO 2 hydrogenation via the carboxylate route, as opposed to the CO 2 dissociation to CO* route over non-modified sulfur vacancies. Furthermore, catalysts at various stages throughout the 60 h induction period were characterized, revealing that the increase in sulfur vacancies and enhanced H 2 dissociation capability are primary factors contributing to improved methanol yield. The sodium-modified MoS 2 achieves a methanol space–time yield of up to 571 mg MeOH g cat. −1 h−1 at 200 °C and 5 MPa with a 4.8% CO 2 conversion and 96% methanol selectivity. The turnover frequency based on total sulfur vacancies reaches 170 h−1. This research is anticipated to offer a new strategy for enhancing the catalytic performance of CO 2 hydrogenation to methanol using heteroatom-assisted defect engineering. [ABSTRACT FROM AUTHOR]

Abstract: We present a novel approach to tune acidity/basicity in non-aqueous and low-water media by using a class of ionic liquids (ILs) with buffering characteristics, which was readily synthesized by the reaction of 1-alkyl-3-methylimidazolium hydroxide ([RMIM]OH) base moieties with a serials of binary or polybasic acids and defined as ionic liquid-buffers (IL-buffers). We have performed controlled experiments of hydrogenation of olefins and trans-cinnamaldehyde, catalyzed by [RuCl2(PPh3)3] in non-aqueous media such as DMF and ILs in the presence of IL-buffers. Remarkable buffer dependence of the formation and catalytic behavior of ruthenium hydrides were evidenced by the kinetic studies and NMR measurements. The hydride [RuHCl(PPh3)3], being favorably formed in the presence of the IL-buffer with lower log10([Base]/[Acid]), exhibited higher activity in the reduction of the Cainst the carbonyl functionality of trans-cinnamaldehyde. While the hydride [RuH4(PPh3)3], being preponderantly formed in the presence of the IL-buffer with higher log10([Base]/[Acid]) showed activity and higher selectivity towards the Con. Consequently, the hydrogenation performance of olefins and trans-cinnamaldehyde in non-aqueous system could be adjusted by adding the different IL-buffers. It is envisioned that the ability of IL-buffers to alter and precisely control the catalytic active species in non-aqueous or low-water systems might find appreciable applications for both fundamental studies and syntheses where the reactions are acid/base-sensitive. [Copyright &y& Elsevier]

• A stable Cu-based catalyst is fabricated by forming Cu–LaO x interfaces. • LaO x not only improves CO 2 adsorptionbut also enhances the dispersion of Cu NPs. • A CO 2 conversion of 6% with a selectivity of 81.2% to methanol without deterioration for 100 h is achieved. • Intermediates of methoxy and formate species are detected by in situ FTIR. • The formate route is preferable in methanol formation at Cu–LaO x interfaces. The direct hydrogenation of CO 2 to methanol has become a very active research field because CO 2 can be prospectively recycled to mitigate greenhouse effect and store clean synthetic fuels. This reaction can be catalyzed by supported Cu catalysts and the catalysts display strong support or promoter effects. Sintering of Cu species accelerates the separation of Cu–oxide interfaces, reduces the active component, and diminishes the methanol selectivity. In this work, we report a Cu catalyst supported on La-modified SBA-15, where the Cu–LaO x interface is generated through the interaction of highly dispersed Cu nanoparticles with LaO x species bedded into the SBA-15 pore wall. The optimized Cu 1 La 0.2 /SBA-15 catalyst can achieve methanol selectivity up to 81.2% with no deterioration in activity over 100 h on stream compared with the La-free catalyst. A thorough study reveals that La species not only significantly improve the CO 2 adsorption but also enhance Cu dispersion to produce well-dispersed active sites. The H/D exchange experiments show that the methanol synthesis displays a strong thermodynamic isotope effect and the Cu–LaO x interface plays a crucial role for the methanol synthesis rate in CO 2 /D 2 feed. In situ DRIFTS studies reveal that *HCOO and *OCH 3 species are the key intermediates formed during the activation of CO 2 and methanol synthesis over the Cu 1 La 0.2 /SBA-15 catalyst. [ABSTRACT FROM AUTHOR]

• The Ag/Zr–SiO 2 catalyst is highly selective for producing unsaturated alcohol. • Significant support effect and interfacial catalysis are observed. • Enhanced acidity by zirconia doping promotes Ag dispersion and catalytic activity. • Interesting low-temperature O 2 chemisorption occurs on interfacial Ag sites. • Ternary Ag–ZrO 2 –SiO 2 interfaces favor the selective activation of C O bond. In gas-phase chemoselective hydrogenation of crotonaldehyde on Ag-based catalysts, zirconia doping on silica supports was found to improve catalytic performance in terms of unsaturated alcohol selectivity, hydrogenation activity, and stability. The surface modification of silica by zirconia doping favors the fine dispersion of Ag species due to the enhanced quantity and strength of surface acid sites, which enable construction of abundant catalytic sites effective for C O bond hydrogenation. High crotyl alcohol selectivity, exceeding 80%, and significant inhibition of monohydrogenation on the C C bond were observed on the optimal Ag/Zr–SiO 2 catalyst. Dynamic O 2 chemisorption measurement revealed that the pure Ag powders did not chemisorb O 2 irreversibly under 323 K, but SiO 2 or Zr–SiO 2 supported Ag catalysts did. The amounts of Ag active for O 2 chemisorption, which are at least one order of magnitude lower than that of surface Ag derived from TEM and XRD characterizations, match well with the perimeter interface Ag of hemispherical particles. A strong correlation between hydrogenation activity and O 2 uptake on those Ag/SiO 2 and Ag/Zr–SiO 2 catalysts with different Ag dispersions and deactivation degrees was observed, implying that the effective catalytic sites for crotonaldehyde chemoselective hydrogenation may originate from accessible interface sites with unique redox properties. Catalyst induction and deactivation were observed on both Ag/SiO 2 and Ag/Zr–SiO 2 catalysts in real catalytic operation. Changes in metal stable interface structure, rather than metal aggregation and coagulation, are assumed to be the main cause of irreversible catalyst deactivation, because the apparent Ag particle sizes changed slightly, but the oxygen chemisorption ability deteriorated considerably. Electropositive Ag sites interacting with neighboring oxygen from oxide supports at the ternary Ag–ZrO 2 –SiO 2 interface are proposed to account for highly selective C O bond hydrogenation to produce the desired unsaturated alcohol. [ABSTRACT FROM AUTHOR]

Heteroatom doping is an attractive approach for improving the properties of carbon materials for various applications. In this study, a series of nitrogen-doped (N-doped) carbon-nanotube-supported Cu–Fe ( x Cu n –Fe m / y N-CNT) catalysts were prepared for CO hydrogenation to higher alcohols. The structural and textural properties of N-doped catalysts were characterized by X-ray diffraction, transmission electron microscopy, hydrogen temperature-programmed reduction, and CO 2 temperature-programmed desorption. The results revealed that doping N into CNT supports improved the Cu–Fe dispersion, strengthened the interaction of Cu and Fe species with N-CNT, and introduced many surface-basicity sites. Thus, an improved CO conversion and excellent selectivity to higher alcohols [ S (C 2+ –OH)] were obtained. Furthermore, the selectivity to alcohols [ S (ROH)] and S (C 2+ –OH)/ S (MeOH) over the optimized 15Cu 1 –Fe 1 /1.3N-CNT catalyst reached 27.2% and 2.2, while the corresponding values were 20.2% and 0.4, respectively, over the catalyst without N doping under identical reaction conditions. The present results on N-CNT supported Cu–Fe catalyst will provide further understanding on the catalyst design for the transformation of syngas to higher alcohols. [ABSTRACT FROM AUTHOR]

Silver nanoparticles supported on nitrogen-doped activated carbon (Ag/AC-N) are demonstrated as promising catalysts for the chemoselective hydrogenation of dimethyl oxalate to methyl glycolate. Characteristic studies by TPR, XPS, and Raman indicate that AC-N benefits the dispersion of silver nanoparticles due to the strong electronic interactions between nitrogen and silver species. The optimized Ag/AC-N catalyst shows intensified performance in terms of high activity and excellent stability. It is inferred that the co-existence of Ag 0 and Ag + derived from the strong interactions of nitrogen with Ag species renders the superior catalytic performance of Ag/AC-N. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tentatively, the activity origin of Ag-ZrO 2−x systems originates from the strengthened electronic metal–support interaction. • In situ DRIFTS indicates pivotal adsorption and activation in C O bond. • EMSIs contribute the interfacial synergistic catalysis and the activity originality. • Thermally stable Ag-ZrO 2−x catalyst with high activity was induced by the electron redispersion. Deciphering intrinsic reactive sites of metal–oxide catalysts, where the outer surface and/or interfaces coupled with oxygen species in the vicinity of nanoparticles concurrently work, remains a challenge. Given the extreme complexity of heterogeneous catalysis (e.g. , metal catalysts for preliminary hydrogenation process), catalytically active sites, the activity origin, and reaction mechanism generally present a so-called 'black box'. Herein, Ag/ZrO 2−x achieves a higher intrinsic hydrogenation rate for selective scission of C O bond per mass Ag than the reference Ag/SiO 2 catalyst, as illustrated by the preliminary hydrogenation of dimethyl oxalate to methyl glycolate. The in-depth characterization revealed that the Agδ+–O v –Zr3+ (Agδ+–O–Zr4+, O v refers to as oxygen vacancy) structure could be engineered owing to the higher affinity of Ag for the partially reduced ZrO 2 surface and heteroatom junctions (in preference to the inert support, such as SiO 2 and Al 2 O 3). Furthermore, the local environment of different crystallite phases (tetragonal or monoclinic ZrO 2) induced tunable (electronic) metal–support interactions (EMSIs), resulting in enhanced catalytic activity and ultra-stability for C O bond hydrogenation. XPS, methyl acetate-TPD, and in situ DRIFTS results unveiled the activity origin of silver–oxide systems, where the location of active metal sites for distinct functionalities over superficial and interfacial phases was validated. The mediated O v was verified to stabilize the thermodynamically unstable metallic (Ag0) and charged silver species (Ag+ or Ag n δ+). More importantly, time-resolved DRIFTS confirmed the crucial interfacial sites of Ag–ZrO 2−x for regioselective C O bond adsorption and activation. Further, the distinct active sites over Ag–ZrO 2−x may release the altered reaction mechanisms, i.e. , conventional Langmuir–Hinshelwood (LH) on Ag/SiO 2 versus quasi Mars–Van Krevelen process (Ag–ZrO 2−x), which presents the new pathway for regioselective C O bond hydrogenation. The coordinated EMSIs were proposed as the origin of the catalytic activity caused by the synergistic catalysis of the interfacial/superficial sites. These findings rationalize the underlying understanding of the EMSI and highlight the instructive role for perceiving the structure-performance relationships and the activity origin in heterogeneous catalysts, thus moving away from the 'black-box' cognition. [ABSTRACT FROM AUTHOR]

Bimetallic AuAg/SBA-15 catalysts were disclosed to efficiently catalyze vapor-phase chemoselective hydrogenation of crotonaldehyde (CRAL) with improved hydrogenation rate and selectivity to crotonyl alcohol (CROL). The CRAL hydrogenation rate and product distribution were remarkably influenced by reaction parameters such as the reaction pressure and CRAL/hydrogen ratio. Ag decoration on Au/SBA-15 effectively stabilized bimetallic AuAg nano-alloy particles in small size and promoted the catalytic stability. In situ FT-IR investigation revealed that unusual C 2 M 2 di-σ bonded CRAL surface species with reinforced symmetric δ(CH 3 ) IR band under the “metal-surface selection rule” (MSSR) were formed on bimetallic AuAg/SBA-15. The stronger CRAL chemisorption on bimetallic AuAg/SBA-15 surfaces than on monometallic Au/SBA-15 was possibly due to the relatively strong ligating of C O bond on Ag active sites and the enhancement of the co-adsorption of the conjugated double bonds of CRAL. Synergistic interaction between Au and Ag active sites for the activation of H H, C C and C O bond may be the origin of positive effect of Ag decoration on Au/SBA-15. [ABSTRACT FROM AUTHOR]

Mesoporous silica SBA-15-supported bimetallic silver–nickel catalysts (Ag–Ni/SBA-15) were prepared by a co-impregnation method for the chemoselective hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG). The structure and physicochemical properties of the catalysts were characterized using N 2 adsorption–desorption, X-ray fluorescence spectroscopy, transmission electron microscopy, H 2 -temperature-programmed reduction, UV–vis light diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, fourier-transform infrared spectroscopy and ester temperature-programed desorption. Compared with monometallic Ag or Ni catalyst, the bimetallic Ag–Ni/SBA-15 catalysts exhibited enhanced catalytic performance for the chemoselective hydrogenation of DMO to MG. The optimized Ag–Ni/SBA-15 catalyst with a Ni/Ag atomic ratio of 0.2 presented the highest MG yield and excellent catalytic stability during the hydrogenation of DMO to MG for longer than 140 h. The characterization results suggested that the Ag and Ni bimetallic nanoparticles on the catalyst surfaces likely formed a segregation structure with more Ni species in the core and more Ag in the shell, and electron transfer from Ni to Ag possibly occurred. The interactions between the Ag and Ni species generated more active/adsorption sites and prevented the transmigration of bimetallic nanoparticles during hydrogenation. [ABSTRACT FROM AUTHOR]

Highlights: [•] A SiO2-supported Cu Ag catalyst is prepared by a urea-assisted gelation method. [•] Ag nanoclusters are involved in Cu nanoparticles on SiO2 surface. [•] Ag modifies the copper dispersion and surface Cu+ site concentration. [•] Hydrogenation of dimethyl oxalate to ethylene glycol over Cu Ag/SiO2 is enhanced. [•] Cu Ag/SiO2 can retain the excellent activity for longer than 150h. [Copyright &y& Elsevier]

Highlights: [•] Pt–Sn/CNT catalyst with highly dispersed PtSn alloy nanoparticles is prepared. [•] Pt–Sn/CNT is an efficient catalyst for the hydrogenation of acetic acid to ethanol. [•] The catalytic performance of Pt–Sn/CNT depends on the contents of Sn and Pt. [•] Addition of Sn to Pt enhances the activity and selectivity of the catalyst obviously. [•] Negligible deactivation of the catalyst occurs for over 300h on stream. [ABSTRACT FROM AUTHOR]

Abstract: Ag/SBA-15 catalyst is found to exhibit excellent catalytic activity and long-term stability for the chemoselective hydrogenation of dimethyl oxalate to methyl glycolate. The size of Ag crystallites, which is markedly affected by the Ag loading levels and catalyst pretreatment conditions, is a key factor determining the reaction rate of the structure-sensitive hydrogenation but hardly influenced the product distribution. The best catalytic hydrogenation activity is obtained over the Ag/SBA-15 catalyst with an average Ag crystallite size of around 3.9nm. [Copyright &y& Elsevier]

Abstract: Gold (Au)–silver (Ag) bimetallic catalyst supported on ordered mesoporous silica SBA-15 exhibits unprecedentedly high activity and superior stability for the selective hydrogenation of dimethyl oxalate to methyl glycolate at a low temperature of 418K. By contrast, monometallic Au/SBA-15 and Ag/SBA-15 catalysts are almost inactive under identical conditions. A combined tuning of particle dispersion and its surface electronic structure is shown as a consequence of the changes in the size and valence band structure of Au and Ag, which leads to significantly enhanced synergy. Considerably reduced apparent activation energies indicate that special active sites with the ability to activate substrate molecules more efficiently are generated in Au–Ag alloy nanoparticles. The Au–Ag bimetallic catalyst also displays excellent activity for the selective hydrogenation of some other unsaturated or saturated esters and acetic acid. [Copyright &y& Elsevier]

Abstract: A novel type of hybrid catalysts composed of Cu/SiO2 and H-form ZSM-5 (HZSM-5) zeolite, prepared using urea-assisted gelation method, displayed excellent catalytic activity and stability for the selective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). The content and SiO2/Al2O3 ratio of HZSM-5 significantly influenced the performance of hybrid catalysts. An unprecedentedly high EG space time yield of 1.50gg-cat −1 h−1, with DMO conversion of 99.5% and EG selectivity of 94.8%, were obtained on a hybrid catalyst containing 3wt% of HZSM-5 with SiO2/Al2O3 =38. The characterizations of N2 physisorption and N2O chemisorptions revealed that both specific surface area and copper dispersion were promoted by introducing HZSM-5 zeolite into the Cu/SiO2 catalyst. Moreover, X-ray Auger electron spectroscopy and in situ Fourier transform infrared spectroscopy of chemisorbed CO demonstrated that the surface Cu+ site concentration of the catalysts containing HZSM-5 was higher than those without HZSM-5. The results indicated that the introduction of HZSM-5 zeolite changed the crystallization behaviors of cupric phyllosilicate precursor, essentially improving copper dispersion and enhancing copper–silica interaction. Furthermore, the specific zeolitic cages and negatively charged framework of HZSM-5 zeolite incorporated into Cu/SiO2 entities might also be beneficial for accommodation and stabilization of highly dispersed cuprous species, which act as efficient active sites for the activation of ester groups. [Copyright &y& Elsevier]

Abstract: Stable and efficient B–Cu–SiO2 catalysts for the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol were prepared through urea-assisted gelation followed by postimpregnation with boric acid. Auger electron spectroscopy and CO adsorption by in situ Fourier transform infrared spectroscopy revealed that the Cu+ species on the catalyst surface increased together with an increase in the amount of boric oxide dopant. X-ray diffraction and N2O chemisorption indicated that a suitable amount of boric oxide doping tended to improve copper dispersion and retard the growth of copper particles during DMO hydrogenation. Catalytic stability was greatly enhanced in the B–Cu–SiO2 catalyst with an optimized Cu/B atomic ratio of 6.6, because of the formation and preservation of appropriate distributions of Cu+ and Cu0 species on the catalyst surfaces. The effect of boric oxide was attributed to its relatively high affinity for electrons, which tended to lower the reducibility of the Cu+ species. [ABSTRACT FROM AUTHOR]

• LaCo 1- x Mn x O 3 perovskites with different substitutions of Co by Mn are prepared. • Substitution of Mn promotes Co 2 C formation and elevates Co 2 C/Co0 ratio. • TPR-MS and XPS are employed to quantitatively define the Co 2 C content. • The yield of alcohols can be attributed to the dual sites of Co0–Co 2 C. LaCo 1- x Mn x O 3 perovskites with different substitutions of Co by Mn were investigated as precursors of catalysts for the CO hydrogenation to produce higher alcohols. Characterization of LaCo 1- x Mn x O 3 perovskites revealed modifications in their structure with the incorporation of Mn into the perovskite lattice affected the structure of the catalysts by reduction prior the reaction. The presence of Mn facilitated the production of alcohols and suppressed the formation of undesirable products, i.e., methane and methanol. Quantitative analysis showed that the catalysts derived from Mn-containing perovskites favored the formation of Co 2 C under the reaction conditions. Thereby the enhanced alcohol selectivity could be explained by the increment of Co 2 C/Co0 ratio. The results demonstrate that the catalysts originated from LaCo 1- x Mn x O 3 perovskites are stable and effective for the synthesis of alcohols by CO hydrogenation. [ABSTRACT FROM AUTHOR]