Search

Synthesizing fine chemicals and valuable pharmaceutical intermediates through selective catalytic oxidation of alcohols is indispensable and crucial. However, the conventional methods of alcohol oxidation have inevitable drawbacks, including harsh reaction conditions and environmental pollution. Thus, it is imperative to develop efficient catalytic oxidation systems for alcohols. Herein, we successfully synthesized a 15 wt %PI‐TiO2 composite by a one‐step solid‐state heating polymerization technique. This catalyst exhibits excellent responsiveness to visible light and demonstrates remarkable catalytic activity. Furthermore, TEMPO was introduced as a cocatalyst to construct a PI‐TiO2/TEMPO/O2 system for the catalytic oxidation of alcohols. In comparison to the individual effects of PI or TiO2, this system showcases improved catalytic activity and broader substrate applicability. As a result, the conversion efficiency of benzyl alcohol increases by 3.44 times and 2.26 times, respectively. This research not only introduces a novel approach for preparing visible light‐active PI‐TiO2 catalysts but also indicates the significance of establishing an efficient electron transfer process in alcohol catalytic oxidation. [ABSTRACT FROM AUTHOR]

Converting cellulose to ethylene glycol has been widely reported, while glucose is seldomly used to produce ethylene glycol. This is challenging due to side reactions such as glucose hydrogenation and isomerization, which have lower activation barriers than retro-aldol condensation. Moreover, cellobiose, rather than glucose, is main intermediates in obtaining ethylene glycol from cellulose. In this study, we found that the in situ synthesized RuxWy/biochar catalyst exhibited high activity for converting glucose to EG. The Ru3.5W35/biochar catalyst achieved the highest EG yield of 61.61% under optimized conditions of 200 °C, 3 MPa H2, and 3 h. Characterization techniques were employed, revealing the crucial roles of W5+ and Ru metal states, which were affected by the calcination temperature. The Ru3.5W35/biochar catalyst calcinated at 400 °C exhibited the best performance and was subsequently applied for the conversion of starch, xylose, and sucrose with appreciable yields of ethylene glycol and 1,2-propanediol. [ABSTRACT FROM AUTHOR]

Photoelectrochemistry (PEC) transfers photoexcited electrons from a photocatalyst to a cathode through a wire, to avoid, to a considerable extent, the recombination of charge carriers in solitary photocatalysis. The moderate bias also consumes less energy than electrocatalysis, rendering PEC a green and promising transformation approach. PEC biomass conversion can be performed at a lower bias than PEC water splitting, and biomass holds great potential for valorization as the world's largest renewable resource. In recent years, there has been escalating interest in the study of PEC valorization from the sacrifice of biomass, but only a few reviews have systematically and specifically addressed it. This review discusses the conversion mechanism of organics, the catalyst and system configuration, and the effect of other variables in detail based on different structures and types of biomass substrates. A brief outlook on the development of the field is outlined in the end as well, and PEC is expected to be an alternative low-carbon, energy-saving, multi-objective route to biomass valorization. [ABSTRACT FROM AUTHOR]

Various kinds of functional amines have been well synthesized by the reductive amination of carbonyl compounds for high-value pharmaceuticals, but they often suffer from complicated processes and low efficiency. In this study, we developed a facile strategy to achieve product diversity using iron-based nanoparticles, whose catalytic selectivity can be particularly controlled via specific combinations of active metals and carbonaceous matrixes in a simple way; over these catalysts, the main products completely switched from primary amines (>91.2%) to secondary imines (>92.3%) in a one-pot process, in accordance with the observed changes in chemical states (Fe0 to FexOy), particle size (9.3 to 63.2 nm), surface acidity (42.4 to 195.7 μmol g−1), and porosity (388.5 to 14.4 m2 g−1). By further analyzing the differences in reaction routes, the dehydration of nucleophilic amines with excess aldehydes was found to be the crucial step, accelerating the chemical equilibrium turned towards secondary imines. In addition, a wide range of substrates (>15 examples) were well tolerated by the prepared catalysts resulting in good to excellent yields (67.7–96.3%), and the catalytic stability was proven to be standard satisfactorily even after reusing up to five times, which was superior to commercial catalysts with noble or transition metals. More surprisingly, the magnetic properties exhibited by the iron cores allowed easy separation from aqueous systems. Overall, this strategy provides an applicable approach for the preparation of simple but highly efficient catalysts for switchable amination, which fills the knowledge gap on catalytic selectivity and exerts a positive impact on the industrial application. [ABSTRACT FROM AUTHOR]

The ammonia (NH3) synthesis industry is significant for many aspects of human progress and the global economy, especially in the fields of fertilizers, hydrocarbon-free energy carriers, and the production of emerging clean fuels. The world's energy for ammonia synthesis accounts for roughly 1–2% of social energy consumption. As an environmentally friendly and cheap raw material, N2 is abundant in nature. Therefore, the search for efficient catalysts that can convert N2 to NH3 under mild conditions with low energy consumption has always been a hot research topic in the field of catalysis. The conversion and utilization of renewable energy sources such as light and electricity, especially chemical energy, is of great importance to human society in terms of energy saving and environmental protection. One of the ways to reduce N2 to NH3 is the electrochemical nitrogen reduction reaction (e-NRR); however, the improvement of e-NRR activity is severely limited by the ultra-high chemical stability of N≡N bonds and the competition from the hydrogen evolution reaction (HER). The three main types of catalysts, metallic (metal complex) and non-metallic catalysts, together with natural biocatalysts, have been the target of development and improvement by researchers as suitable catalysts. In terms of photocatalytic N2 synthesis of ammonia, due to the relatively stable chemical properties of N2 molecules, it is difficult for traditional photocatalytic materials to generate the activity of reducing N2 molecules. Through continuous innovation and improvement of photocatalysts, researchers are able to increase the catalytic sites of catalysts and find suitable supporting materials to activate N2 molecules, which greatly improves the efficiency of photocatalytic N2 synthesis of ammonia. This review highlights the recent progress and development of photocatalysts and electrocatalysts for the synthesis of NH3 from N2, and briefly introduces the advantages of various catalysts and the comparison of synthesis efficiency. It is expected to provide a reference for the development of new processes that can produce high value-added chemicals. [ABSTRACT FROM AUTHOR]

Efficient utilization of renewable biomass plays a vital role in CO2 mitigation. Direct conversion of cellulose, the most abundant fraction in lignocellulosic biomass, into ethylene glycol is a promising route. In this work, by using the biowaste pomelo peel as the carbon precursor, the Ru–WOX/biochar (BC) bifunctional catalyst was prepared via pyrolysis in a nitrogen atmosphere without further reduction. Cellulose could be efficiently converted into ethylene glycol with a yield of 68.8% after 10 h using Ru–WOX/BC at the temperature of 220 °C and 3 MPa H2. The effects of reaction temperature, reaction time, H2 pressure and catalysts obtained from different pyrolysis temperatures on the yield of ethylene glycol were investigated. The characterization and reaction results showed that the gas generated from pyrolysis of pomelo peel could partially reduce ruthenium precursor to metallic form. Metallic Ru can not only promote the reduction of W6+ to W5+, but also work on hydrogenation reaction. The catalyst and preparation method have a promising application in cellulose conversion. [ABSTRACT FROM AUTHOR]

Renal cell carcinoma (RCC) is the third most frequent malignancy within urological oncology. Sunitinib has been used as the standard of treatment for first-line RCC therapy. Understanding mechanisms of sunitinib resistance in RCC cell is important for clinical therapy and drug development. We established sunitinib resistant RCC cells by treating cells with increasing concentrations of sunitinib and named resistant cells as RCC/SR. Lefty A, an important embryonic morphogen, was increased in RCC/SR cells. Targeted inhibition of Lefty via its siRNAs restored the sensitivity of renal resistant cells to sunitinib treatment. It was due to that si-Lefty can decrease the expression of interleukin-8 (IL-8) in RCC/SR cells. Knockdown of IL-8 abolished Lefty-regulated sunitinib sensitivity of RCC cells. Mechanistically, Lefty can regulate IL-8 transcription via activation of p65, one major transcription factor of IL-8. Collectively, our present revealed that Lefty A can regulate sunitinib sensitivity of RCC cells of via NF-κB/IL-8 signals. It indicated that targeted inhibition of Lefty might be a potent approach to overcome sunitinib resistance of RCC. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) as additives were used in the selective conversion of bio-based carbohydrates to 5-hydroxymethylfurfural (HMF) in this work. The effect of adding various imidazole-based ionic liquids with different anion structures on the production of HMF from fructose was firstly investigated in aqueous media. The presence of 15 wt% 1-butyl-3-methylimidazole chloride ([Bmim]Cl) ionic liquids in water with Fe2(SO4)3 as the homogeneous catalyst provided a more effective HMF synthesis compared to that without [Bmim]Cl addition. The enhanced HMF yield was mainly attributed to the fact that [Bmim]Cl might play a vital role in stabilizing the HMF molecule, which could thereby suppress side reactions involving HMF (e.g., its rehydration to levulinic acid or/and polymerization to humins). NMR and FTIR analyses suggested that such a stabilization effect stemmed from the interaction of [Bmim]Cl with the hydroxyl and aldehyde groups of HMF through hydrogen bonding. By performing the operation in a biphasic system (i.e., with the biomass-derived THF solvent as the organic phase and the addition of NaCl salt into water for improving HMF partition), the HMF yield over the Fe2(SO4)3 catalyst in the presence of the [Bmim]Cl additive could be further improved. The catalyst and ionic liquids were quite stable, and could be reused for more than five cycles with a consistent activity. A similar enhancement effect of [Bmim]Cl was also demonstrated in HMF synthesis with better yields from other biomass feedstocks or derivatives (including glucose, sucrose, cellobiose, inulin and starch) in aqueous media. [ABSTRACT FROM AUTHOR]

A series of core‐shell catalysts with different shell thickness were synthesized and the effect of microporous silica shell on product distribution of Fischer‐Tropsch synthesis was analyzed. Fe3O4 core was prepared by hydrothermal method and the amorphous SiO2 shell was coated on the Fe3O4 core by sol‐gel method. N2 adsorption‐desorption analysis indicated an irregular and microporous silica shell and the pore size distribution moved to smaller diameter with the shell thickness increased. In Fischer‐Tropsch synthesis, inactive silica shell increased catalytic activity (FTY) and stability by restricting catalyst cracking and sintering. Product distribution shifted to C1‐C4 gaseous hydrocarbons with the increasing shell thickness probably due to the diffusion limitations on reactants/products and structure confinement and separation effect of microporous silica shell on restricting the growth of catalytic active particles. Selectivities of C5+ were restricted within 10% for core‐shell catalysts. WGS reaction activity is reduced as well, which constrains side reaction and amplifies FTS catalytic productivity to hydrocarbons. Fe3O4 nanospheres coated with microporous silica shell catalyst inhibits carbon chain growth and shifts FTS product distribution to gaseous hydrocarbons (C1‐C4). The inactive silica shell separates neighboring actives sites of iron core and inhibits the growth of iron carbides also confined carbon chain growth. Catalytic activity and stability are enhanced and water‐gas shift reaction activity is reduced and hydrocarbon productivity is improved over core‐shell catalysts. [ABSTRACT FROM AUTHOR]

5‐hydroxymethylfurfural (HMF), an important platform compound produced from lignocellulosic biomass, is widely applied in petrochemical industry for downstream synthesis of medical supplies or intermediate of the other important chemicals by the typical catalytic processes. A continuous production route was developed to yield HMF from monosaccharides by using zirconium phosphate (ZrP) with different Zr/P ratios as catalysts. Its physicochemical properties were then characterized by Brunauer‐Emmett‐Teller (BET), X‐ray powder diffraction (XRD), X‐ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT‐IR), pyridine adsorbed Fourier transform infrared spectroscopy (Py‐FT‐IR), X‐ray fluorescence (XRF) and temperature programmed desorption of ammonia (NH3‐TPD) techniques. A mixed phase containing monosaccharide in aqueous and dimethyl sulfoxide (DMSO) phase was applied in the fixed bed to keep the continuous production. The optimized reaction conditions were applied to maximized HMF yield by varying the processing parameters. The highest HMF yield of 56.3% was obtained when using fructose as the feedstock under the reaction condition of 120 °C, 180 min, N2 pressure 2 MPa and DMSO: fructose solution of 9:1 over ZrP with the P/Zr with molar ratio of 2. Comparatively, the glucose conversion of 72% with the HMF yield of 32% were gained under the same conditions using glucose as the feedstock. It is deduced that the ZrP catalysts simultaneously possessing Brönsted/Lewis acid showed synergy in glucose dehydration to HMF. The ZrP catalyst showed good stability and no obvious deactivation was observed after 30 h of time‐on‐stream, due to the primary structure and acidic properties of catalyst can be kept during the reaction. Finally, it is generally efficient for some C6 sugars dehydration to HMF with the Brönsted/Lewis acid synergy of ZrP. ZrP solid acids synthesized with dfferent Zr/P ration are tested in the dehydration of typical C6 monosaccharides to HMF (5‐hydroxymethylfurfural). ZrP (P/Zr = 2) showed the best catalytic activity for obtaining the highest HMF yield of 56.3%. The ZrP catalyst is generally efficient for C6 sugars dehydration to HMF, where B and L acidic sites showed synergism effect on glucose dehydration to HMF. [ABSTRACT FROM AUTHOR]

Sorbitol, as a C6 sugar related compound derived from cellulose, is regarded as a promising biomass‐derived substrate and has characteristically higher oxygen content than in fossil‐based resources. In this work, ruthenium–molybdenum carbon catalysts prepared by different impregnation processes were employed and extensively studied in a trickle‐bed reactor for sorbitol hydrodeoxygenation (HDO). Interestingly, these catalysts afforded remarkably different HDO performance. Ruthenium–molybdenum catalysts prepared by ultrasonic treatment and calcination obtained high HDO performance in sorbitol conversion with 79.8 % carbon yield of C5/C6 alkanes (pentane and hexane), almost twice that of ruthenium–molybdenum catalysts prepared without using a calcination processes. Therefore, a series of characterization studies (N2‐adsorption, XRD, HRTEM, XPS, H2‐TPR, CO‐TPD, NH3‐TPD, Py‐IR spectra, etc.) were performed over relevant catalysts to study the catalytic mechanism. The results suggest that prior calcination offers a better chance for the proximity between Ru and Mo precursors to produce the bimetallic catalytic structure Ru–MoOx, which produces high HDO performance. Sweet catalysis: Ru–MoOx/C catalysts from different impregnation processes were carefully studied and extensively employed for sorbitol conversion to C5/C6 alkanes in trickle‐bed reactor. The results suggest that prior calcination offers a better chance for the proximity between Ru and Mo precursors to produce the bimetallic catalytic structure Ru–MoOx, which produces high HDO performance towards biofuels synthesis. [ABSTRACT FROM AUTHOR]

Recently, we demonstrated the catalytic conversion of biomass hydrolysate and real biomass into renewable alkanes over a Ru/C catalyst with aqueous phosphoric acid (Ru/C+H3PO4) and we obtained a high yield of C5/C6 alkanes. In this study, the mechanism of sorbitol hydrodeoxygenation (HDO) into alkanes over the Ru/C+H3PO4 catalytic system was investigated by using a trickle-bed reactor. A high HDO performance was detected with a large amount of long-chain alkanes in the products. Subsequently, pre- and postcharacterization studies (N2 adsorption, XRD, X-ray photoelectron spectroscopy, TEM, NH3 temperature-programmed desorption, H2 temperature-programmed reduction, FTIR spectroscopy) were performed on the relevant catalysts to study the change of the catalytic active sites. Moreover, mineral acid experiments were performed to study the influence of phosphoric acid on the HDO performance. [ABSTRACT FROM AUTHOR]

The aqueous-phase hydrogenation of propanoic acid was performed over the Ru/ZrO and Ru/AlO catalysts with different Ru loading. Combined with multiple characterization techniques, such as H-TPR, XRD, CO-FTIR, and DRIFTS of propanoic acid, the effect of Ru loading on the decarbonylation/hydrogenation of propanoic acid was investigated. Although hydrogenation/decarbonylation of carboxylic acids were strongly affected by the nature of supports, the increase of metal loading can cause the larger Ru particles and more bare Ru metal sites, which can facilitate the C-C bond cleavage reaction derived from the decarbonylation of propanoyl species over Ru metal sites. Graphical Abstract: [ABSTRACT FROM AUTHOR]

BACKGROUND: The catalytic degradation of aqueous Fischer-Tropsch (FT) effluents to fuel gas over Ru/AC has been investigated. In order to understand the catalytic performance and stability of oxide-supported Ru catalysts, several oxide supports (titania, zirconia, γ-alumina and silica) were selected for study, with a focus on the hydrothermal stability of catalysts. RESULTS: The catalytic efficiency for transforming the oxygenates in aqueous FT effluents to C1-C6 alkanes decreased in the order: Ru/ZrO2∼ Ru/TiO2 > Ru/SiO2 > Ru/Al2O3. The conversion of alcohols was greatly suppressed over Ru/γ-Al2O3. The former two catalysts (Ru/ZrO2 and Ru/TiO2) exhibited enhanced efficiency and long-term stability (400 h) relative to Ru/SiO2 and Ru/Al2O3. N2-physisorption, XRD and SEM showed that titania and zirconia exhibited high structural stability in an aqueous environment. However, the structures of γ-alumina and silica were unstable due to significant drop in surface area and adverse changes in surface morphology. Especially for the case of the Ru/γ-Al2O3 catalyst, the γ-alumina was transformed into boehmite structure after reaction, and metal leaching and carbon deposition were extensive. CONCLUSION: Ru/ZrO2 or Ru/TiO2 may be a promising alternative for degrading aqueous FT effluents due to their long-term stability. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Hydrogenolysis of glycerol to 1,3-propanediol in aqueous-phase was investigated over Pt-HSiWO/SiO bi-functional catalysts with different HSiWO (HSiW) loading. Among them, Pt-15HSiW/SiO showed superior performance due to the good dispersion of Pt and appropriate acidity. It is found that Brønsted acid sites facilitate to produce 1,3-PDO selectively confirmed by Py-IR. The effects of weight hourly space velocity, reaction temperature and hydrogen pressure were also examined. The optimized Pt-HSiW/SiO catalyst showed a 31.4% yield of 1,3-propanediol with glycerol conversion of 81.2% at 200 °C and 6 MPa. Graphical Abstract: [Figure not available: see fulltext.]. [ABSTRACT FROM AUTHOR]

The selective hydrogenolysis of 5-hydroxymethylfurfural (HMF) platform molecule to 2,5-dimethylfuran (DMF) has attracted increasing attention due to its broad range of applications. However, HMF, with multiple functional groups, produces various byproducts, hindering its use on an industrial scale. Herein, a bimetallic Pt-FeOx/AC catalyst with low Pt and FeOx loadings for selective HMF hydrogenolysis to DMF was prepared by incipient wetness impregnation. The structures and properties of different catalysts were characterized by XRD, XPS, TEM, ICP-OES and Py-FTIR techniques. The addition of FeOx enhanced Pt dispersion and the Lewis acidic site density of the catalysts, and was found to be able to inhibit C=C hydrogenation, thereby im-proving DMF yield. Moreover, the presence of Pt promoted the reduction of iron oxide, creating a strong interaction between Pt and FeOx. This synergistic effect originated from the activation of the C–O bond over FeOx species followed by hydrogenolysis over the adjacent Pt, and played a critical role in hydrogenolysis of HMF to DMF, achieving a yield of 91% under optimal reaction conditions. However, the leaching of Fe species caused a metal–acid imbalance, which led to an increase in ring hydrogenation products. [ABSTRACT FROM AUTHOR]

Ammonium iron citrate was used as an iron precursor in order to prepare N-doped catalysts supported on KMnO4 pretreated activated carbon (10MnK-AC). Iron nitride was synthesized in company with the formation of α-Fe2O3 on 10MnK-AC. The characterizations of the catalysts show that nitrogen atoms were doped into iron lattice rather than the networks of the carbon support. The performance of Fischer-Tropsch synthesis to light olefins (FTO) suggest an improvement in O/P ratio (olefins to paraffins molar ratio of C2–C4) over the iron catalysts supported on 10MnK-AC. The further promotion of light olefins selectivity (up to 44.7%) was obtained over FeN-10MnK-AC catalyst owing to the collaborative contribution of the electron donor effect of nitrogen and the suppression effect on the second hydrogenation over 10MnK-AC support. [ABSTRACT FROM AUTHOR]

The Cover shows the catalytic conversion of biomass hydrolysate into renewable alkanes over a Ru/C catalyst with aqueous phosphoric acid (Ru/C+H3PO4), in which a high yield of C5/C6 alkanes was obtained.In their Full Paper, Y. Weng et al. investigated the mechanism of the sorbitol hydrodeoxygenation (HDO) reaction into alkanes over a Ru/C+H3PO4 catalyst by using a trickle‐bed reactor. Higher HDO performance might be a result of the bifunctional role of the catalytic system. These findings suggest that the downstream process of biomass hydrolysis could be directly conducted in acid aqueous phase at low reaction temperature, reducing the amount of acid waste. [ABSTRACT FROM AUTHOR]