As the main component of lignocelluloses, cellulose is a biopolymer consisting of many glucose units connected through β-1,4-glycosidic bonds. Breakage of the β-1,4-glycosidic bonds by acids leads to ...the hydrolysis of cellulose polymers, resulting in the sugar molecule glucose or oligosaccharides. Mineral acids, such as HCl and H
2
SO
4
, have been used in the hydrolysis of cellulose. However, they suffer from problems of product separation, reactor corrosion, poor catalyst recyclability and the need for treatment of waste effluent. The use of heterogeneous solid acids can solve some of these problems through the ease of product separation and good catalyst recyclability. This review summarizes recent advances in the hydrolysis of cellulose by different types of solid acids, such as sulfonated carbonaceous based acids, polymer based acids and magnetic solid acids. The acid strength, acid site density, adsorption of the substance and micropores of the solid material are all key factors for effective hydrolysis processes. Methods used to promote reaction efficiency such as the pretreatment of cellulose to reduce its crystallinity and the use of ionic liquids or microwave irradiation to improve the reaction rate are also discussed.
This paper reviews the recent advances in cellulose hydrolysis into glucose over solid acids, which plays an important role in the conversion of biomass derived carbohydrates into useful platform molecules.
The continued threat of emerging, highly lethal infectious pathogens such as Middle East respiratory syndrome coronavirus (MERS‐CoV) calls for the development of novel vaccine technology that offers ...safe and effective prophylactic measures. Here, a novel nanoparticle vaccine is developed to deliver subunit viral antigens and STING agonists in a virus‐like fashion. STING agonists are first encapsulated into capsid‐like hollow polymeric nanoparticles, which show multiple favorable attributes, including a pH‐responsive release profile, prominent local immune activation, and reduced systemic reactogenicity. Upon subsequent antigen conjugation, the nanoparticles carry morphological semblance to native virions and facilitate codelivery of antigens and STING agonists to draining lymph nodes and immune cells for immune potentiation. Nanoparticle vaccine effectiveness is supported by the elicitation of potent neutralization antibody and antigen‐specific T cell responses in mice immunized with a MERS‐CoV nanoparticle vaccine candidate. Using a MERS‐CoV‐permissive transgenic mouse model, it is shown that mice immunized with this nanoparticle‐based MERS‐CoV vaccine are protected against a lethal challenge of MERS‐CoV without triggering undesirable eosinophilic immunopathology. Together, the biocompatible hollow nanoparticle described herein provides an excellent strategy for delivering both subunit vaccine candidates and novel adjuvants, enabling accelerated development of effective and safe vaccines against emerging viral pathogens.
To improve vaccination efforts against Middle East respiratory syndrome coronavirus (MERS‐CoV), a virus‐mimicking vaccine is herein prepared with a capsid‐like hollow polymeric nanoparticle loaded with STING agonists and coated in MERS‐CoV antigens. The viromimetic nanoparticle facilitates safe and effective vaccination against the lethal virus and offers a versatile platform for combatting emerging infectious threats.
The catalytic transfer hydrogenation of furfural to the fuel additives 2‐methylfuran (2‐MF) and 2‐methyltetrahydrofuran (2‐MTHF) was investigated over various bimetallic catalysts in the presence of ...the hydrogen donor 2‐propanol. Of all the as‐prepared catalysts, bimetallic Cu‐Pd catalysts showed the highest catalytic activities towards the formation of 2‐MF and 2‐MTHF with a total yield of up to 83.9 % yield at 220 °C in 4 h. By modifying the Pd ratios in the Cu‐Pd catalyst, 2‐MF or 2‐MTHF could be obtained selectively as the prevailing product. The other reaction conditions also had a great influence on the product distribution. Mechanistic studies by reaction monitoring and intermediate conversion revealed that the reaction proceeded mainly through the hydrogenation of furfural to furfuryl alcohol, which was followed by deoxygenation to 2‐MF in parallel to deoxygenation/ring hydrogenation to 2‐MTHF. Finally, the catalyst showed a high reactivity and stability in five catalyst recycling runs, which represents a significant step forward toward the catalytic transfer hydrogenation of furfural.
Identifying the intermediates: The catalytic transfer hydrogenation of biomass‐derived furfural to fuel additives 2‐methylfuran and 2‐methyltetrahydrofuran is performed over a bimetallic Cu‐Pd catalyst in the presence of 2‐propanol. The reaction proceeds via the intermediate furfuryl alcohol, which is then deoxygenated/hydrogenated to the desired products.
The development of new catalytic systems for the conversion of biomass‐derived molecules into liquid fuels has attracted much attention. We propose a non‐noble bimetallic catalyst based on ...nickel–tungsten carbide for the conversion of the platform molecules 5‐(hydroxymethyl)furfural into the liquid‐fuel molecule 2,5‐dimethylfuran (DMF). Different catalysts, metal ratios and reaction conditions have been tested and give rise to a 96% yield of DMF. The catalysts have been characterized and are discussed. The reaction mechanism is also explored through capture of reaction intermediates. The analysis of the reaction mixture over different catalysts is presented and helps to understand the role of nickel and tungsten carbide during the reaction.
W ai Ni: A nickel–tungsten carbide on active carbon (Ni‐W2C/AC) catalyst converts the biomass platform molecule 5‐(hydroxymethyl)furfural (HMF) into the liquid fuel molecule 2,5‐dimethylfuran (DMF) via the intermediate 5‐methylfurfural. Synergy between the Ni and W2C components combines their hydrogenating and deoxygenating abilities and allows to achieve high yields of DMF.
Peroxymonosulfate (PMS) is extensively used as an oxidant to develop the sulfate radical-based advanced oxidation processes in the decontamination of organic pollutants and various PMS activation ...methods have been explored. Visible-light-assisted PMS activation to construct a Fenton-like process has shown a great potential for pollution control. In our work, BiVO4 nanosheets were prepared using a hydrothermal process and used to activate PMS under visible light. A rapid degradation of ciprofloxacin (CIP) was achieved by dosing PMS (0.96 g/L), BiVO4 (0.32 g/L) under visible light with a reaction rate constant of 77.72-fold higher than that in the BiVO4/visible light process. The electron spin resonance and free radical quenching experiments indicate that reactive species of •O2−, h+, •OH and SO4•− all worked, where h+, •OH and SO4•− were found as the dominant contributors to the CIP degradation. The spectroscopic analyses further demonstrate that the photoinduced electrons were directly involved in the PMS activation process. The generated •O2− was partially utilized to activate PMS and more •OH was produced because of the chain reactions between SO4•− and H2O/OH−. In this process, PMS acted as an electron acceptor to transfer the photo-induced charges from the conduction band of BiVO4 and PMS was successfully activated to yield the high-powered oxidative species. From the degradation intermediates of CIP detected by a liquid-chromatography-mass spectrometer, the possible degradation pathways were proposed. The substantially decreased toxicity of CIP after the reaction was also observed. This work might provide new insights into the visible-light-assisted PMS activation mechanisms and is useful to construct environmentally-friendly catalytic processes for the efficient degradation of organic pollutants.
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•PMS was effectively activated by BiVO4 nanosheets for water purification under visible light.•Separation of electron/hole pairs and generation of oxidative species were enhanced.•Visible-light-assisted PMS activation Fenton-like mechanism was elucidated.•High mineralization and low biotoxicity validated the application potential of the system.
A catalytic transfer hydrogenation process was developed for the production of γ-valerolactone (GVL) from ethyl levulinate (EL) and a H-donor at room temperature. Ethyl levulinate was almost ...quantitatively converted to γ-valerolactone. Further, a two step process for producing GVL from biomass derived platform molecules was also reported.
Cellulose is the most abundant, renewable carbohydrate resource in nature, providing human society with a broad spread of materials for production and living. Compared with the mature textile and ...paper industries, technologies for cellulose utilization to produce energy and chemicals are still under development. In particular, the depolymerization of cellulose to glucose and further transformation into various fuel compounds or chemicals has received considerable attention as a sustainable approach to address the energy crisis and environmental issues raised by massive fossil consumption. Among various cellulose derived molecule types, ester is one of the most appealing owing to its unique physicochemical properties, reactivities and functions. This review summarizes recent advances in the chemical synthesis of esters from cellulose and its derivatives. Various esters, including alkyl levulinates, γ-valerolactone, valerates, pentenoates, lactates
etc.
, have been effectively prepared from cellulose feedstock or its downstream platform compounds. The catalytic systems were highlighted with rational integration of the active sites for the tandem reactions involved in the conversions. The kinetics, process integration, selectivity control and catalysis mechanism were also discussed in detail. Finally, an outlook of the future direction, as well as the challenges, for cellulose ester production were also illustrated.
This review highlights recent advances in the conversion of cellulose and its derivatives (monosaccharides and platform molecules) into ester chemicals.
Efficient production of chemicals from cellulose provides sustainable routes for the utilization of natural renewable resources to meet the requirements of human society. Herein, we reported a highly ...efficient and simple metal salt catalyst, Al 2 (SO 4 ) 3 , for cellulose conversion to methyl levulinate (ML) under microwave conditions. A highest ML yield of 70.6% was obtained at 180 °C within a very short time of 40 min. The introduction of water could reduce humin/coke formation and solvent consumption, and could also switch the reaction pathway via the more reactive intermediate glucose. Kinetic and mechanistic studies of the subreactions showed that both cellulose hydrolysis and alcoholysis pathways were involved in the cellulose conversion to ML, with the former as the main route in the presence of water. The Lewis acid species Al(OH) x (H 2 O) y n+ and the Brønsted acid species H + , generated by in situ hydrolysis of Al 2 (SO 4 ) 3 , were responsible for the reaction conversions. The reaction with microwave heating showed accelerated reaction rates of 25 times the reaction with conventional oil heating, and even more times for the rates of glucose and methyl glucoside (MG) dehydration, resulting in higher reaction selectivity toward ML production. The catalyst was also successfully recycled and applied to the conversion of cellulose to other alkyl levulinates, as well as the conversion of raw biomass to ML with high yields. The homogeneous nature of Al 2 (SO 4 ) 3 , together with its high efficiency and excellent recyclability, make it a potential catalyst for the large-scale production of ML in industry.
Direct hydrogenolysis of the aromatic C sub(sp) super(2)-O bonds in both phenols and phenyl ethers to form arenes selectively is a core enabling technology that can expand greatly the scope of ...chemical manufacture from biomass. However, conventional hydrogenolysis of phenols typically led to aromatic ring saturation instead of the cleavage of the C sub(sp) super(2)-O bonds. Herein, we report a recyclable Ru-WOx bifunctional catalyst that showed high catalytic activities for the hydrogenolysis of a wide range of phenols and phenyl ethers, including dimeric lignin model compounds and the primitive phenols separated from pyrolysis lignin, to form arenes selectively in water. Preliminary mechanistic studies supported that the reactions occurred viaa direct cleavage of the C sub(sp) super(2)-O bonds and the concerted effects of the hydrogenating Ru sites and the Lewis acidic W sites are the key to such an unusual reactivity.
Catalytic transfer hydrogenation (CTH) with alcohols has been increasingly employed as effective tool for biomass upgrading, however, relying predominantly on secondary alcohols. Herein, for the ...first time skeletal CuZnAl catalysts were employed for the activation of a primary alcohol, ethanol, for the hydrogenation 5‐hydroxymethylfurfual (HMF) to 2,5‐bis(hydroxymethyl)furan (BHMF) under a mild condition. The catalysts were extensively characterized to reveal the structure characteristics and surface compositions. Over 90 % yield of BHMF were obtained over the optimal CuZnAl‐0.5 catalyst at the reaction temperatures of 100–120 °C. Reaction kinetics indicated a competitive adsorption between HMF and ethanol on the catalyst surface, with the activation of ethanol being the rate‐determining step (apparent activation energy Ea=70.9 kJ mol−1). Preliminary adsorption investigation using combined attenuated total reflectance infrared spectroscopy and density functional theory calculation proposed a η2‐(O,O)‐aldehyde, furoxy perpendicular configuration of HMF on catalyst surface. The catalyst was further applied to the CTH of various aldehydes to the corresponding alcohols with high yields, demonstrating the broad applicability of the current system.
Transfer hydrogenation: A facilely prepared skeletal CuZnAl catalyst is found to be active for primary alcohol activation for catalytic transfer hydrogenation, efficiently converting biobased 5‐hydroxymethylfurfural (HMF) to 2,5‐bis(hydroxymethyl)furan (BHMF) with up to 92 % yield under a mild condition of 100–120 °C.
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