Totally found 1325 items.

  • [期刊] Continuous reactor for renewable methanol
    For society and corporations to decisively shift to fossil fuel alternatives and avoid the likely devastating consequences of climate change and ecosystem destruction of 'business-as-usual', a renewable pathway to carbon net-neutral or net-negative feedstocks is of utmost importance. Methanol (MeOH) is a promising candidate but is still produced with conventional natural gas to syngas technology. The need for fossil-free and less costly syngas routes to MeOH has been the focus of immense academic effort. Towards this end, this study details a version 1.0 tool for investigating prospective photochemical and thermal heterogeneous MeOH synthesis catalysts and present thermal benchmarking data with a commercial copper-zinc oxide-alumina (CZA) catalyst. The testing conditions use a 3 : 1 H-2 : CO2 syngas ratio, temperatures from <448-533 K (<175-260 degrees C), and pressure up to 0.78 MPa. These conditions allow for more efficient CO2 utilization by improving low-temperature MeOH yield and reducing capital and operating costs of process equipment. The reactor performance is validated with respect to the literature and also a rate model based on a Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism with good agreement. This verifies that the system behaves isothermally and predictably. This unique system can be configured to screen catalysts both thermally and with light, and expanded to commercial test conditions and scales. At aspirational low-temperature and low-pressure conditions, 398 K (125 degrees C) and 1.0 MPa (comparable P to this study), the MeOH equilibrium per-pass yield is a respectable 8.8 mol% with comparable high-P equipment costs to current commercial operations.
  • [期刊] Decoupling the role of carbon counterparts in Pickering emulsifier for an enhanced selective oxidation of benzyl alcohol
    Pickering emulsion, a novel medium and reaction platform, has great potential for applications in interfacial catalysis. Although various efforts have been made to modulate suitable catalysts for such reactions, unveiling the intrinsic role of a catalyst in enhanced catalytic activity is highly desired. In this aspect, biomass-derived carbon was combined with hydrophilic zeolite particles to decouple the role of catalysts under Pickering interfacial catalysis (PIC) conditions for enhanced performance. The surface properties of the as-made nanocomposites were engineered and optimized in detail. This also modulated the emulsion capabilities and showed the volcano distribution of catalytic efficiency towards the selective oxidation of benzyl alcohol, indicative of the optimal activity with a conversion of up to >95% and good reusability under base-free conditions with molecular oxygen. It was found that the catalytic efficiency was strongly dependent on the interfacial area provided by the Pickering emulsion and followed the pseudo-first-order rate kinetics. The large biphasic interfacial area was in favor of mass transfer in the reaction process and reduced the external diffusion resistance. The quantitative measurements by electrochemical quartz crystal microbalance (EQCM) and temperature-programmed desorption of oxygen (O-2-TPD) revealed that the combined carbon was able to enhance the adsorption capability towards benzyl alcohol five-fold and oxygen as compared to pristine S-1 during the reaction process. These integrated superiorities are responsible for enhanced catalytic efficiency.
  • [期刊] Sustainable at both ends: electrochemical CO(2)utilization paired with electrochemical treatment of nitrogenous waste
    We discuss the environmental and energetic benefits of coupling nitrogenous waste treatment with the electrochemical conversion of CO(2)to value-added productsviadirect reduction or electrocarboxylation. In particular, we demonstrate that co-electrolysis of urea or ammonia with CO(2)requires significantly lower cell voltages than CO(2)electrolyzers relying on the oxygen evolution reaction as an anodic process.
  • [期刊] tert-Butanol intervention enables chemoselective conversion of xylose to furfuryl alcohol over heteropolyacids
    Both the solvent and catalyst play important roles in the chemoselective transformation of biomass-related compounds to fine chemicals and fuels. We report herein an innovative catalytic strategy for the direct valorization of xylose without external H(2)producing high yield of furfuryl alcohol (FA), which is a versatile platform molecule. The solventtert-butanol served not only as a precursor of the hydrogen honor, but also as a shield to facilitate xylose dehydration and inhibit the polymerization and decomposition reactions of FA. Commercial H(4)SiW(12)O(40)was found to work as a multifunctional catalyst during the cascade conversion and had good reusability. The underlying catalytic mechanism revealed that the Bronsted and Lewis acid sites co-existed cooperatively to catalyze the xylose dehydration step and the active metal site of W atom adsorbed the hydrogen proton for the transfer hydrogenation of furfural to FA. After the incorporation of the formic acid as a supplemental hydrogen source, an unprecedented FA yield of 90% could be accomplished in a batch reactor under mild conditions. The kinetic behavior describing the conversion of xylose to FA was investigated to monitor the process. The estimated activation energies for xylose dehydration, furfural hydrogenation, and FA decomposition were 85.1, 78.8, and 101.1 kJ mol(-1), respectively. This study opens a new avenue for the selective production of FA from hemicellulose-derived pentose in a green and straightforward manner.
  • [期刊] Flame-made amorphous solid acids with tunable acidity for the aqueous conversion of glucose to levulinic acid
    Solid acids of amorphous silica-alumina (a-SA) and amorphous silica-alumina-phosphate (a-SAPO) were prepared by flame spray pyrolysis (FSP). Careful tuning of the acidity of the solid acids was enabled by capitalizing on the advantage of FSP in preserving the metal stoichiometry (i.e., Si, Al, P) in the product nanoparticles. Although the amount of acids on these non-porous solid acids is an order of magnitude lower than the well-recognized strong acidic ZSM-5 zeolite, both exhibit comparable acid strengths. The a-SA and a-SAPO were characterized by a mixture of Bronsted (B) and Lewis (L) acids, and the B/L ratios were composition-tunable. The highest B/L ratios were recorded for a-SA (Al/(Al + Si) = 0.4) and a-SAPO (Si/(P + Si) = 0.25), giving the highest yields of levulinic acid (>= 40% carbon yield) from the conversion of glucose in the aqueous phase without requiring the addition of liquid acids or metal halides. Under the same conditions, the almost exclusive Bronsted acid ZSM-5 yielded only 17% levulinic acid. The FSP-made solid acid catalyst exhibited good reusability over at least 4 consecutive runs.
  • [期刊] Bio-based polyesters synthesized by ring-opening copolymerizations of eugenyl glycidyl ether and cyclic anhydrides using a binuclear [OSSO]CrCl complex
    A novel binuclear chromium complex of dianionic [OSSO]-type ligand has been synthesized and employed toward the ring-opening copolymerization of renewable eugenyl glycidyl ether (EGE) and cyclic anhydrides (CAs) (succinic anhydride (SA), phthalic anhydride (PA), maleic anhydride (MA), itaconic anhydride (IA),endo-norbornene anhydride (NA), and tetrahydrophthalic anhydride (THPA)), showing high activity in conjunction with bis(triphenylphosphine)iminium chloride (PPNCl). Most of the resultant polyesters show perfect alternating microstructures except polyesters derived from IA/EGE and MA/EGE copolymerimerization, where 14% and 11% of ether units are observed, respectively. Among the CAs tested, renewable SA shows the highest reactivity as a highly regioselective model, providing a facile route to prepare the fully biomass-based polyester bearing a dominant head-to-tail structure. The results of ESI-MS indicate that the maximum coordination number of PPNCl in the dinuclear [OSSO]CrCl complex is only one. The pendant allyl groups onto the resultant polyesters backbone provide an additional versatility for further functionalizations.
  • [期刊] Tetracoordinate borates as catalysts for reductive formylation of amines with carbon dioxide
    We report sodium trihydroxyaryl borates as the first robust tetracoordinate organoboron catalysts for reductive functionalization of CO2. These catalysts, easily synthesized from condensing boronic acids with metal hydroxides, activate main group element-hydrogen (E-H) bonds efficiently. In contrast to BX(3)type boranes, boronic acids and metal-BAr(4)salts, under transition metal-free conditions, sodium trihydroxyaryl borates exhibit high reactivity of reductiveN-formylation toward a variety of amines (106 examples), including those with functional groups such as ester, olefin, hydroxyl, cyano, nitro, halogen, MeS-, ether groups,etc. The over-performance to catalyze formylation of challenging pyridyl amines affords a promising alternative method to the use of traditional formylation reagents. Mechanistic investigation supports electrostatic interactions as the key for Si/B-H activation, enabling alkali metal borates as versatile catalysts for hydroborylation, hydrosilylation, and reductive formylation/methylation of CO2.
  • [期刊] One-pot synthesis of 2-hydroxymethylindolesviaphotoredox-catalyzed ketyl-ynamide coupling/1,3-allylic alcohol transposition
    An efficient visible-light-mediated ketyl-ynamide coupling by employing ynamides bearing alkyl sulfonyl substituents to deliver eneindolin-3-ols has been developed. Subsequent 1,3-transposition of allylic alcohols in one pot is capable of synthesizing 2-hydroxymethylindoles in generally moderate to good yields. The synthetic utility of this protocol has also been demonstrated by the facile and practical synthesis of two bioactive molecules. The use of readily available substrates, a simple procedure and benign reaction conditions render this method a viable alternative for the synthesis of 2-hydroxymethylindoles.
  • [期刊] Mobility and adsorption of liquid organic hydrogen carriers (LOHCs) in soils - environmental hazard perspective
    Liquid organic hydrogen carriers (LOHCs) are an energy system that can be used to store and transport hydrogen under standard temperature and pressure chemically bound to a carrier. The LOHC systems show advantages over conventional energy systems (recyclability, higher sustainability and lower emissions) and other hydrogen-based systems (lower loses, ease of handling and higher safety), and are applied in stationary and mobile applications worldwide. The scale and type of use indicate that the release of LOHCs to the environment can be expected. Yet, their behaviour and fate have not been investigated especially with regard to assessment of exposure, mobility and possibility to reach surface water, groundwater or drinking water sources. To investigate that we studied the mobility of thirteen technologically promising LOHC candidates including indole, quinaldine, carbazole derivatives, benzyltoluene and dibenzyltoluene, and their (partially) saturated forms in soil, for the first time. The substances were classified into mobility classes based on their organic carbon-water partition coefficients (K-oc) determinedvia in silicomodels and HPLC screening. The log K(oc)values increased in the order indoles < quinaldines < carbazole derivatives < benzyltoluenes < dibenzyltoluenes covering a full spectrum of mobility scale (from highly mobile to immobile). The behaviour of exemplary LOHC system - quinaldine including H-2-unsaturated, partially and fully saturated forms - was further assessed by investigating the soil-water partition coefficients (K-d)viaadsorption batch equilibrium and column leaching test. The study showed that some LOHCs can be expected to be very mobile in soils and have the potential to reach groundwater.
  • [期刊] Early-stage evaluation of emerging CO(2)utilization technologies at low technology readiness levels
    Most CO(2)utilization technologies are at low technology readiness levels (TRLs). Given the large number of potential technologies, screening to identify the most promising ones should be conducted before allocating large R&D investment. As these technologies exhibit different levels of technical maturity, a systematic, TRL-dependent evaluation procedure is needed which can also account for the quality and availability of data. We propose such a systematic and comprehensive evaluation procedure. The procedure consists of three steps: primary data preparation, secondary data calculation, and performance indicator calculation. The procedure depends on the type of CO(2)utilization technology (thermochemical, electrochemical, or biological conversion) as well as the TRL (2-4). We suggest databases, methods, and computer-aided tools that support the procedure. Through four case studies, we demonstrate the proposed procedure on emerging CO(2)utilization technologies, which are of different types and at various TRLs: electrochemical CO(2)reduction for production of ten chemicals (TRL 2); co-electrolysis of CO(2)and water for ethylene production (TRL 2-4); direct oxidation of CO2-based methanol for oxymethylene dimethyl ether (OME1) production (TRL 4); and microalgal biomass co-firing for power generation (TRL 4).