Novel hydrothermal carbonization of cellulose catalyzed by montmorillonite to produce kerogen-like hydrochar

The conversion of cellulose to petroleum-like fuel is a very challenging yet attractive route to developing biomass-to-fuel technology. Many attempts have been made in liquefaction, pyrolysis and gasification of cellulose to produce fuels or intermediate chemicals. Previous studies indicate that these processes are tough. Hence, the present work is concerned with the development of new technologies for the conversion of cellulose into materials which are analogies to the precursor of petroleum. Montmorillonite-catalyzed hydrothermal carbonization of microcrystalline cellulose for the production of kerogen-like hydrochar under mild conditions was investigated. It was revealed that the hydrothermal carbonization of microcrystalline cellulose alone resulted in hydrochar with type III kerogen-like structure, whereas in the presence of montmorillonite, the hydrothermal carbonization of microcrystalline cellulose yielded a hydrochar-mineral complex, of which the isolated organic fraction was oil-prone type II kerogen-like structure. Results suggested that further improved montmorillonite-aided biomass conversion to more oil-prone kerogen-like solid products could be an alternative efficient route to obtain biofuel and chemicals.     

Carbon dioxide-assisted fabrication of highly uniform submicron-sized colloidal carbon spheres via hydrothermal carbonization using soft drink

An eco-friendly and economical method for the formation of highly uniform-sized carbon spheres by hydrothermal dehydration/condensation of a commercial carbonated beverage at 200?°C is reported. Until now, the effect of an extra pressure which is built up by dissolved CO₂ on the generation of carbon spheres under hydrothermal condition less than 250?°C hasn’t been demonstrated yet. In general, a complicated reactor is required to put overpressure on the autoclave vessel by adding inert gases, whereas the manipulation of a carbonated beverage including fructose and glucose molecules as precursors is favorable to design a simple experimental set-up and to investigate the effect of extra pressure on the growth of carbon spheres under mild hydrothermal condition. Herein, CO₂ dissolved in the beverage accelerates the dehydration kinetics of the dissolved sugar molecules leading to production of homogeneous carbon spheres having a diameter less than 850?nm. In addition, the rough surface of these carbon spheres likely results from continuous Ostwald ripening of constituent microscopic carbon-containing spheres that are formed by subsequent polymerization of intermediate hydroxymethylfurfural molecules.     

One-step synthesis of novel biacidic carbon via hydrothermal carbonization

The novel biacidic carbon has been synthesized via one-step hydrothermal carbonization of glucose, citric acid, and hydroxyethylsulfonic acid at 180 °C for only 4 h. The novel carbon had an acidity of 1.7 mmol/g with the carbonyl to sulfonic acid groups molar ratio of 1:3, which was confirmed by IR, XPS, TPD, SEM, and BET analyses. The catalytic activities of the carbon were investigated through esterification and oxathioketalization. The results showed that the carbon owned the comparable activities to sulfuric acid, which indicated that the carbon holds great potential for the green processes.     

One-step synthesis of a novel carbon-based strong acid catalyst through hydrothermal carbonization

Abstract  

A novel carbon-based strong acid catalyst was synthesized through the one-step hydrothermal carbonization of furaldehyde and p-toluenesulfonic acid (PTSA) in aqueous solution at 180 °C for only 4 h. The novel carbon-based solid acid possessed high acidity, and the catalytic activities were investigated by esterification and oxathioketalization. The results showed that the novel catalyst demonstrated much greater activity than the traditional solid acids and was comparable to sulfuric acid. The one-step method provides an efficient procedure for the synthesis of various functionalized carbons by one-step hydrothermal carbonization.     

Hierarchical ZSM-5 catalyst synthesized by a Triton X-100 assisted hydrothermal method

ZSM-5 zeolite with a hexagonal cubic morphology was synthesized by a hydrothermal method using Triton X-100, a nonionic surfactant. The samples prepared with and without the surfactant were characteriz...     

Cellulose hydrolysis using zinc chloride as a solvent and catalyst

Cellulose gel with < 10% of crystallinity was prepared by treatment of microcrystalline cellulose, Avicel, with zinc chloride solution at a ratio of zinc chloride to cellulose from 1.5 to 18 (w/w). The presence of zinc ions in the cellulose gels enhanced the rate of hydrolysis and glucose yield. The evidence obtained from X-ray diffraction, iodine absorption experiments; and Nuclear Magnetic Resonance spectra analysis suggested the presence of zinc-cellulose complex after Avicel was treated with zinc chloride. Zinc-cellulose complex was more susceptible to hydrolysis than amorphous cellulose. Under the experimental condition, cellulose gels with zinc ions were hyrolyzed to glucose with 95% theoretical yield and a concentration of 14% (w/v) by cellulases within 20 h. The same gel was hydrolyzed by acid to glucose with 91.5% yield and a concentration of 13.4% (w/v).     

Selenium nanotube synthesized via a facile template-free hydrothermal method

Trigonal Se nanotube was successfully synthesized by a facile and green one-step hydrothermal method, using Na₂SeO₃ as selenium source and glucose as reducing agent. The samples were characterized by XRD, TEM, HRTEM, SAED, UV–Vis and so on. The investigation found the glucose played the key role in the formation of t-Se nanotube. The possible growth mechanism was also discussed.     

Synthesis of glycolipid analogs via highly regioselective macrolactonization catalyzed by lipase

Highly regioselective lipase catalyzed macrolactonization has been used in synthesizing first feedstock based glycolipid analogs. These macrolides containing common disaccharides maltose (4-O-α-d-glucopyranosyl-β-d-glucose) and melibiose (6-O-α-d-galactopyranosyl-β-d-glucose) were synthesized by employing chemoenzymatic methodologies. Maltose and Melibiose were coupled with methyl 15-hydroxy pentadecanoate and then subjected to a highly regioselective macrolactonization at the C-6″ position using Candida antarctica lipase-B to yield the desired products.     

Removal of uranium(VI) from aqueous solutions by new phosphorus-containing carbon spheres synthesized via one-step hydrothermal carbonization of glucose in the presence of phosphoric acid

The novel phosphorus-rich hydrothermal carbon spheres (HCSs–PO₄) have been synthesized via one-step hydrothermal carbonization of glucose in the presence of phosphoric acid. The textural and surface chemistry properties were characterized using Boehm titrations, scanning electron microscopy and Fourier transform infrared spectrometer. The content of oxygen-containing functional groups on the surface of HCSs increased from 0.053 to 1.009 mmol g^?1 by phosphate group modification. The adsorption ability of HCSs–PO₄ has been explored for the removal of uranium from aqueous solutions. The adsorption kinetic data were best described by the pseudo-second-order equation. Adsorption process could be well defined by the Langmuir isotherm, the adsorption capacity of HCSs increased from 80.00 to 285.70 mg g^?1 after phosphate group modification. And thermodynamic parameters indicated the adsorption process was feasible,endothermic and spontaneous. Selective adsorption studies showed that the HCSs–PO₄ could selectively remove U(VI), and the selectivity coefficients had been improved in the presence of co-existing ions, Na(I), Ni(II), Sr(II), Mn(II), Mg(II) and Zn(II). Complete removal (99.9 %) of U(VI) from 1.0 L industry wastewater containing 15.0 mg U(VI) ions was possible with 12.0 g HCSs–PO₄.     

Charcoal produced from cellulosic raw materials by microwave-assisted hydrothermal carbonization

In this work, cellulose-based renewable raw materials were hydrothermally carbonized in a microwave oven at 200 °C during 60, 120, and 240 min. The charcoals obtained were characterized by proximate analysis, gross calorific value, and thermogravimetric analysis on inert and oxidizing atmosphere. The values of fixed carbon were between 38 and 52 %. The mass loss between 300 and 470 °C was assigned to the thermal decomposition of cellulose, followed by the second stage between 470 and 740 °C, attributed to the thermal decomposition of lignin. The gross calorific values were between 22.60 and 27.12 MJ kg^?1, which are comparable to those of charcoals and coals.     

水热法制备的LuFeO3晶粒的超声催化活性

超声波在水中传播时会产生大量空化气泡,空化气泡经历成核、生长和瞬间崩塌等过程,并在崩塌瞬间产生局部高温和高压,过程中会发出瞬间闪光,即声致发光.局部高温高压及声致发光可将半导体价带上的电子激发至导带,形成电子/空穴对,电子和空穴迁移至半导体颗粒表面,参与一系列氧化还原反应致使有机污染物发生分解.由于超声波在各种液体中都具有很强的穿透能力,因此与半导体光催化技术相比,半导体超声催化技术在降解高浓度和不透明染料废水时具有明显优势. LuFeO3是稀土正铁氧体中的一员,具有独特磁结构、巨介电常数及多铁性,近年来引起了人们极大的研究兴趣.同时, LuFeO3也是一种窄带隙半导体材料,使其可以作为一种潜在的超声催化剂,但相关报道很少.半导体材料的晶粒尺寸及形貌对其超声催化活性的影响非常大,因此制备出不同晶粒尺寸及形貌的LuFeO3颗粒并研究其超声催化性能具有重要意义.目前LuFeO3的主要制备方法为传统的固相反应法,该法需要反复研磨和高温煅烧使原料彻底反应,而且制备出的颗粒尺寸较大,相互粘连严重,形貌难以控制.在众多纳米材料制备方法中,水热法在调控晶粒尺寸及形貌上具有巨大优势.本课题组曾采用水热法成功制备了单相的LuFeO3颗粒,通过改变NaOH浓度,可以对产物的晶粒尺寸及形貌进行调控.基于此,本文以酸性橙(AO7)、罗丹明B (RhB)、甲基橙(MO)和亚甲基蓝(MB)为目标降解物,考察了水热法所制备的LuFeO3颗粒在超声辐照下的超声催化性能,并系统研究了晶粒尺寸及形貌、无机离子和乙醇对LuFeO3颗粒超声催化活性的影响及LuFeO3颗粒重复利用性能.以对苯二甲酸(TPA)为分子荧光探针,采用光致发光(PL)技术检测在超声辐照下LuFeO3反应液中产生羟基自由基(?OH)的情况,探讨了LuFeO3颗粒的超声催化机理.超声催化反应结果表明,采用水热法制备的LuFeO3颗粒在超声辐照下表现出良好的超声催化活性.在NaOH浓度为0.625 mol/L时制备的LuFeO3颗粒尺寸最小,表现出最好的超声催化活性;经过30 min超声催化反应后,AO7,RhB,MO和MB的超声降解率分别为89%,82%,73%和67%.加入Cl?, NO3?, SO42?, PO43?和HCO3?对LuFeO3颗粒的超声催化活性有抑制作用.向反应液中加入2%(v/v)乙醇后, LuFeO3颗粒在超声辐照下对AO7几乎没有降解,表明?OH在超声催化中起重要作用.重复回收实验结果表明, AO7的降解率随着循环次数增加有所下降,这可能是由于催化剂回收时的损失所致.尽管如此,催化剂仍能保持较高的催化活性,经4次循环后,反应30min时AO7的降解率为65%.PL结果表明, LuFeO3颗粒在超声催化反应中产生了大量的?OH,添加乙醇可以消耗?OH并抑制染料的超声催化降解.由此可见,?OH是超声催化降解RhB的主要活性物种.我们对LuFeO3导带和价带的电位进行了估算,从热力学角度对LuFeO3颗粒超声催化降解染料的机理做出了初步解释.     

ZnO porous structures synthesized by CTAB-assisted hydrothermal process

ZnO porous structures have been fabricated by cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal process. X-ray diffraction (XRD) pattern indicated that the synthesized ZnO porous structures were hexagonal. It is found that CTAB influences the morphology of ZnO structures. On the basis of structural information provided by XRD, SEM, and TEM, a growth mechanism is proposed for the formation of ZnO porous structures.     

Photocatalytic water reduction under visible light on a novel ZnIn2S4 catalyst synthesized by hydrothermal method

A novel ZnIn2S4 catalyst synthesized by hydrothermal method shows high and stable photocatalytic activity for water reduction under visible light illumination.     

Promoted NH3-SCR activity and hydrothermal stability of Cu-SSZ-50 catalyst synthesized by one-pot method

Nitrogen oxide(NO_x) is one of the most critical contaminants in the air, and the control of NO_x emission from diesel vehicles is very important. Cu-based small-pore zeolites have already been applied for NO_x abatement on diesel vehicles. Among the small-pore zeolites, Cu-SSZ-50 catalysts with good NH₃-SCR catalytic activity were believed to have potential for application. In this study, a one-pot synthesis method for Cu-SSZ-50 catalysts was developed f...     

Enantioselective ester hydrolysis catalyzed by imprinted polymers

Highly cross-linked network polymers prepared by molecular imprinting catalyzed enantioselectively the hydrolysis of N-tert-butoxycarbonyl phenylalanine-p-nitrophenyl ester (BOCPheONP). The templates were designed to allow incorporation of the key catalytic elements, found in the proteolytic enzyme chymotrypsin, into the polymer active sites. Three model systems were evaluated. These were constructed from a chiral phosphonate analogue of phenylalanine (series A, C) or L-phenylalanine (series B) attached by a labile ester linkage to an imidazole-containing vinyl monomer. Free radical copolymerization of the template with methacrylic acid (MAA) and ethylene glycol dimethacrylate (EDMA) gave a highly cross-linked network polymer. The templates could be liberated from the polymers by hydrolysis, giving catalytically active sites envisaged to contain an enantioselective binding site, a site complementary to a transition state like structure (series A, C), and a hydroxyl, imidazole, and carboxylic acid group at hydrogen bond distance. As predicted, the enantiomer of BOCPheONP complementary to the configuration of the template was preferentially hydrolyzed with D-selectivity for the series A polymers (kD/kL = 1.9) and L-selectivity for the series B polymers (kL/kD = 1.2). The maximum rate enhancement, when compared with a control polymer, prepared using a benzoyl-substituted imidazole monomer as template, was 2.5, and comparing with the imidazole monomer in solution, a maximum rate enhancement of 10 was observed. The catalytic activity was higher for polymers subjected to the nucleophilic treatment. This was explained by a higher site density and flexibility of the polymer matrix caused by this treatment. In a comparison of template rebinding to polymers imprinted with a template containing either a carboxylate (planar ground state structure) or a phosphonate (tetrahedral transition state like structure) functionality, it was observed that imprinted polymers are able to discriminate between a transition state like and a ground state structure for transesterification. However the influence of transition state stabilization on the observed rate enhancements remains obscure. Only at acidic pH's was catalysis observed, whereas at basic pH's the polymers inhibit the reaction. At a later stage, the catalytic activity of the polymers for nonactivated D- and L-phenylalanine ethyl esters was investigated. A rate enhancement of up to 3 was observed when compared to the blank. Most important, however, the polymers imprinted with a D template preferentially hydrolyzed the D-ethyl ester and exhibited saturation kinetics.     

A green route to 1,2-cyclohexanediol via the hydrolysis of cyclohexene oxide catalyzed by water

Effective hydrolysis of cyclohexene oxide (CHO) was conducted by heating in water between 100 and 140?°C without another catalyst. It provided 100?% purity and 100?% yield of trans-1,2-cyclohexanediol (1,2-CHD) with five times of H₂O to CHO at 120?°C for 6?h. These intermediates of polyether polyols could be totally decomposed to 1,2-CHD (monomer) by hot water under the same condition. The improved process eliminates the purification and markedly reduces the cost of 1,2-CHD in the follow-up industrial production. The main factors, such as reaction temperature, time, and water volume, were investigated. It was proposed that water acted as a modest acid catalyst, reactant, and solvent in the hydrolysis of CHO and polymers.     

One-step synthesis of amino-functionalized fluorescent carbon nanoparticles by hydrothermal carbonization of chitosan

Highly amino-functionalized fluorescent carbon nanoparticles (CNPs) were fabricated by hydrothermal carbonization of chitosan at a mild temperature. They were applied to bioimaging of human lung adenocarcinoma A549 cells, showing low cytotoxicity and excellent biocompatibility.     

Adsorption of uranium from aqueous solution using biochar produced by hydrothermal carbonization

The ability of biochar produced by hydrothermal carbonization (HTC) has been explored for the removal and recovery of uranium from aqueous solutions. The micro-morphology and structure of HTC were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The influences of different experimental parameters such as solution pH, initial concentration, contact time, ionic strength and temperature on adsorption were investigated. The HTC showed the highest uranium sorption capacity at initial pH of 6.0 and contact time of 50 min. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir isotherm. The thermodynamic parameters, △G°(298 K), △H° and △S° were determined to be ?14.4, 36.1 kJ mol^?1 and 169.7 J mol^?1 K^?1, respectively, which demonstrated the sorption process of HTC towards U(VI) was feasible, spontaneous and endothermic in nature. The adsorbed HTC could be effectively regenerated by 0.05 mol/L HCl solution for the removal and recovery of U(VI). Complete removal (99.9 %) of U(VI) from 1.0 L industry wastewater containing 15.0 mg U(VI) ions was possible with 2.0 g HTC.     

Characterization of the visible-light-driven BiVO4 photocatalyst synthesized via a polymer-assisted hydrothermal method

BiVO₄ photocatalyst was synthesized by a polymer-assisted hydrothermal method at different temperatures and reaction times. Sodium carboxymethylcellulose was used in order to assist the formation of BiVO₄ oxide. The resulting samples were characterized by X-ray powder diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, and adsorption–desorption N₂ isotherms (BET). The predominant BiVO₄ phase of the system within the 160–200 °C range was the monoclinic crystalline structure, which was obtained in pure form only under certain experimental conditions. Short reaction times promoted the formation of linear arrays of BiVO₄ formed by particles with irregular form ranging in size between 100 and 200 nm. The photocatalytic activity of BiVO₄ samples was evaluated in the degradation of rhodamine B (rhB) under visible-light irradiation. The samples exhibited a higher activity when they were synthesized at higher temperatures and longer times of hydrothermal reaction. The total organic carbon analysis of a sample irradiated for 100 h revealed that mineralization of rhB by the BiVO₄ photocatalyst is feasible.