Cold NaOH/urea aqueous dissolved cellulose for benzylation: Synthesis and characterization

Cold NaOH/urea aqueous dissolved cellulose was studied for the synthesis of benzyl cellulose by etherification with benzyl chloride. By varying the molar ratios of benzyl chloride to OH groups in cellulose (1.5–4.0) and reaction temperatures (65–70 °C), benzyl cellulose with a degree of substitutions (DS) in the range of 0.29–0.54 was successfully prepared under such mild conditions. The incorporation of benzyl groups into cellulose was evidenced by multiple spectroscopies, including FT IR, ¹H NMR, ¹³C NMR, CP/MAS ¹³C NMR and XRD. In addition, the thermal stability and surface morphology of the benzyl cellulose was also investigated with regard to the degree of substitution. The results indicated that the benzyl cellulose product with a low DS (0.51) in the present study reached the same solubility in many organic solvents as compared to those prepared in heterogeneous media. After benzylation, the sample decomposed at a lower temperature with a wider temperature range, which indicated that the thermal stability of benzyl cellulose was lower than that of the native cellulose. In addition, benzylation resulted in a pronounced reduction in crystallinity as well as a fundamental alteration of morphology of the native cellulose.     

Low temperature synthesis of layered NaxCoO2 and KxCoO2 from NaOH/KOH fluxes and their ion exchange properties

We report a low temperature synthesis of layered Na_0.20Co0₂ and K_0.44CoO₂ phases from NaOH and KOH fluxes at 400°C. These layered oxides are employed to prepare hexagonal HCoO₂, Li_xCoO₂and Delafossite AgCoO₂ phases by ion exchange method. The resulting oxides were characterised by powder X-ray diffraction, X-ray photoelectron spectroscopy, SEM and EDX analysis. Final compositions of all these oxides are obtained from chemical analysis of elements present. Na_0.20Co0₂ oxide exhibits insulating to metal like behaviour, whereas AgCoO₂ is semiconducting. Dedicated to Professor C N R Rao on his 70th birthday     

[Pt]—Ni（Ⅱ）电极的研究

我们首次发现Pt浸于镍、钴或铁盐溶液中,只有镍可形成[Pt]-Ni(Ⅱ)电极。在NaOH电解液中,此电极有明显的氧化还原峰,表现出Ni电极的特征。本文研究[Pt]-Ni(Ⅱ)电极的电化学性能、电极制备的影响因素。 1 实验部分 研究电极:Pt为基底,用5~#金相砂纸磨光,在王水中浸渍,二次蒸馏水冲洗(也可再进     

FLOW PROPERTIES OF WEATHERED CRUDE OILS AND THEIR EMULSIONS

The present paper proposes the emulsification of weathered crude oils in water as a competitive and cost effective method for reducing their viscosities. Weathered crude oil samples were collected from major Kuwaiti oil lakes. Emulsion preparation involved using, either a nonionic surfactant or alkali, as well as both alkali and fatty acid. The obtained emulsions were characterized by measuring the droplet size distribution of the dispersed phase using optical microscopy. Emulsion stability was also examined in terms of the system breakdown. The rheological properties were measured using a concentric cylinder rotary rheometer. The emulsion rheological behavior has been studied as a function of composition, temperature, and shear rate. A constitutive model was developed to characterize the pseudoplastic behavior of the crude oil and the emulsion systems. The model fitted well the experimental results with a correlation coefficient higher than 95%. Associated with the pseudoplastic behavior, viscoelastic behavior has been observed with emulsions and some oils at high shear rates.

The results of this investigation indicated that the examined weathered crude oils can be transported through pipelines as emulsions of up to 80 vol.% oil concentrations. The proposed method of treatment with NaOH and oleic acid offers several advantages over the surfactant treatment. It exhibited comparable rheological behavior at lower cost and less mixing energy. It also provided higher emulsion stability, which favors oil transportation for longer distances.     

Eco-efficient ultrasonic responsive synthesis of pyrimidines/pyridines

Using ultrasound irradiation, two simple one-pot multicomponent methods are described for syntheses of highly functionalized pyrimidine/pyridine derivatives in excellent yields in the presence of NaOH at room temperature. While one route involved aromatic aldehyde, thiourea and acetoacetanilide, the other employed aromatic aldehyde, malononitrile and benzyl mercaptane or EtOH. These approaches afford several advantages over former and contemporary reaction methodologies in terms of operational simplicity, simple work-up procedure, higher yield, short reaction time and environment friendly protocols.     

Influence of processing parameters on regeneration kinetics and morphology of porous cellulose from cellulose–NaOH–water solutions

The kinetics of cellulose regeneration in acetic acid bath from cellulose–8% NaOH–water solutions and gels is studied as a function of gelation conditions, acid concentration and bath temperature. The diffusion coefficient of NaOH from cellulose solution or gel into regenerating bath was calculated. It does not depend either on gelation mode or on acid concentration. On the contrary, cellulose regeneration from non-gelled solutions is slower than from a gel. The increase in bath temperature induces diffusion coefficient increase obeying Arrhenius law. Scanning electron microscopy images of regenerated swollen-in-water freeze-dried cellulose and of the same samples dried in supercritical CO₂ show highly porous morphology. CEMEF is a Member of the European Polysaccharide Network of Excellence (EPNOE), .     

Optimizing the synergistic effect of sodium hydroxide/ultrasound pre-treatment of sludge

Ultrasound (ULS), sodium hydroxide (NaOH) and combined ultrasound/NaOH pre-treatment were applied to pre-treat waste activated sludge and improve the subsequent anaerobic digestion. Synergistic effect was observed when NaOH treatment was coupled with ultrasound treatment. The highest synergistic Chemical Oxygen Demand (COD) solubilization was observed when 0.02M NaOH was combined with five minutes ultrasonication: an extra 3000 mg/L was achieved on top of the NaOH (1975 mg/L) and ultrasonication (2900 mg/L) treatment alone. Further increase of NaOH dosage increased Soluble Chemical Oxygen Demand (SCOD), but did not increase the synergistic effect. Nine and 18 minutes ultrasonication led to 20% and 24% increase of methane production, respectively; Whereas, 0.05M NaOH pre-treatment did not improve the sludge biodegradability. Combined ultrasound/NaOH (9 min+0.05 M) showed 31% increase of methane production. A stepwise NaOH addition/ultrasound pre-treatment (0.02M+ULS for 5 min+0.02M+ULS for 4 min) was tested and resulted in 40% increase of methane production using 20% less chemicals.     

NaOH浓度对Cu_2O结构及甲醛乙炔化性能的影响

以CuCl_2·2H_2O为铜源,NaOH为沉淀剂,L-抗坏血酸钠为还原剂,采用液相还原法制备了Cu_2O,并将其应用于甲醛乙炔化反应制1,4-丁炔二醇.借助傅里叶变换红外光谱(FT-IR)、拉曼光谱(Raman)、X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)和H_2程序升温还原(H2-TPR)等手段研究了NaOH浓度对Cu_2O结构、性质及催化性能的影响.结果表明,调变NaOH浓度改变了Cu2O的结晶度与粒径,从而使Cu_2O表现出不同的炔化性能.低NaOH浓度时,Cu_2O结晶度低,粒径小,易被还原为非活性的金属Cu;高浓度时,Cu_2O结晶度过高,粒径大,难以转化为活性物种炔化亚铜,两者均造成催化剂活性较低.而中等浓度的NaOH使Cu_2O具有了适宜的结晶度与粒径大小,Cu_2O可高效转化为炔化亚铜活性物种,表现出最优的炔化性能.     

Characterization of lignin using multi-angle laser light scattering and atomic force microscopy

Small differences in the isolation techniques of lignin can result in significant changes in its molecular structure and configuration. Light scattering (evaluated at 18 different angles in a plane), Atomic Force Microscopy (AFM) and Near Infrared Spectroscopy (NIR) proved very effective for evaluating the characteristics of lignin. Zimm plots were generated using Zimm, Debye and Berry formalisms to evaluate the weight average molecular weight (MW), radius of gyration (r_g), hydrodynamic radius (r_h) and second virial coefficient (A₂). Two types of lignin and nine different solvents were used for the study, to analyze the conformation of lignin molecules in different solvents expected to be used in lignin degradation and subsequent analysis. Absolute MW and r_g decreased and the dn/dc increased when the solvent used for lignin was changed from water to sodium hydroxide. The two types of lignin also exhibited different values for all the above estimated parameters. This study also highlighted the differences between the unlyophilized and lyophilized lignin in terms of aggregation, pH dependence and stability over time. This aggregation has never been seen on a ultraviolet (UV) or refractive index (RI) detector that has been used so far for liquid chromatography (LC) reducing the reliability of lignin depolymerization data obtained without light scattering.     

Effect of sodium cation on the electrochemical reduction of CO<Subscript>2</Subscript> at a copper electrode in methanol

The electrochemical reduction of CO₂ with a Cu electrode in methanol was investigated with sodium hydroxide supporting salt. A divided H-type cell was employed; the supporting electrolytes were 80 mmol dm⁻³ sodium hydroxide in methanol (catholyte) and 300 mmol dm⁻³ potassium hydroxide in methanol (anolyte). The main products from CO₂ were methane, ethylene, carbon monoxide, and formic acid. The maximum current efficiency for hydrocarbons (methane and ethylene) was 80.6%, at −4.0 V vs Ag/AgCl, saturated KCl. The ratio of current efficiency for methane/ethylene, r _f(CH₄)/r _f(C₂H₄), was similar to those obtained in LiOH/methanol-based electrolyte and larger relative to those in methanol using KOH, RbOH, and CsOH supporting salts. In NaOH/methanol-based electrolyte, the efficiency of hydrogen formation, a competing reaction of CO₂ reduction, was suppressed to below 4%. The electrochemical CO₂ reduction to methane may be able to proceed efficiently in a hydrophilic environment near the electrode surface provided by sodium cation.