摘要:

AbstractThe role of acetyl chloride as the active catalyst in the chlorination of acetic acid to mono‐ and dichloroacetic acids was examined by chlorinating acetic acid and monochloroacetic acid in the presence of acetyl chloride in semibatch and batch reactors. The reaction kinetics was autocatalytic when the acetyl chloride concentration was maintained constant by addition. If the acetyl chloride was added only at the beginning of the experiment the reaction rate decreased owing to the volatilization of acetyl chloride. The volatilization increased at high acetic acid conversions, since the solubility of acetyl chloride is lower in monochloroacetic acid than in acetic acid. The chlorination kinetics was described by a reaction mechanism consisting of acid‐catalysed acetyl chloride enolization followed by enol chlorination and chlorine exchange steps. According to the mechanism the enol chlorination proceeds in parallel to the formation of mono‐ and dichloroacetyl chlorides. This was verified in separate experiments, in which acetyl chloride was chlorinated in the presence and in the absence of an acidic enolizing agent, chlorosulphonic acid. The chlorine exchange reactions were verified by studying the acetyl chloride–monochloroacetic acid and the acetyl chloride–dichloroacetic acid equilibria. Chlorination of monochloroacetic acid in the presence of acetyl chloride revealed that dichloroacetic acid is formed mainly via the chlorination of acetyl chloride to dichloroacetyl chloride, which undergoes chlorine exchange with monochloroac

ISSN:0268-2575    

DOI:10.1002/jctb.280610102

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractTween 80 (polyoxyethylene sorbitan monooleate), Triton X‐100 (nonaethylene glycol octylphenol ether), and SDS (sodium dodecyl sulfate) solubilized several components of Mississippi Wilcox lignite and Illinois No. 6 bituminous coal. Tween 80 extraction of alkali‐soluble Ugljevik lignite resulted in an increase in hydrogen content and decreases in the nitrogen and sulfur contents of undissolved coal solids. Biosurfactant‐containing cell‐free extracts ofBacillus licheniformissolubilized a 53 000 Da coal component of Mississippi Wilcox lignite. The results suggest that solubilization of coal organic components by chemically‐ and biologically‐synthesized surfactants has potential in terms of upgr

ISSN:0268-2575    

DOI:10.1002/jctb.280610103

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractCombined biosynthesis and product separation has been successfully performed for the first time using a zonal centrifugal bioreactor–separator. The biosynthesis of dextran polymer from sucrose using the dextransucrase enzyme was investigated in order to evaluate bioreactor performance. The bioreactor consisted of a bowl, fitted with a Reorienting gradient rotor which facilitated substrate and enzyme loading and the reproducible unloading of solutions from the system. This allowed the distribution of substrate, enzyme and product materials in the bowl at the end of each trial to be accurately determined. Studies have indicated that combined bioreaction–separation is possible using this system. However, viscosity build‐up in the bioreactor must be minimised in order to increase the yield of polymer product per unit time and improve product separ

ISSN:0268-2575    

DOI:10.1002/jctb.280610104

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractTrimethoprimium‐phosphomolybdata, (TM)3PM, was used as an ion‐exchanger in the construction of a TM‐responsive plastic membrane electrode. The calibration graph slope of the electrode is 56·5 mV per TM concentration decade when preconditioned by soaking in water, over a concentration range of 2·3 × 10−6–10−2M with instantaneous response. The electrode has a life span of 24 h when soaked in 10−3M TM solution and 5 days when soaked in distilled water. The working pH and temperature ranges of the electrode are 1·6–6·2 and 30–65·C, respectively. The isothermal coefficient of the electrode is 0·00091 V·C−1. The electrode is highly selective for TM towards inorganic cations, sugars and amino acids. It can be employed as a potentiometric sensor for determination of TM in

ISSN:0268-2575    

DOI:10.1002/jctb.280610105

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe aim of this work was to determine easily and quickly the operating conditions for the industrial production of lactulose (rate of isomerisation, rate of lactose degradation, reaction time, temperature, pH). The kinetic equations of lactulose formation and lactose degradation in an alkaline medium (NaOH) were determined. Experiments were carried out at different OH−concentrations (0·5 × 10−2–19 × 10−2mol dm−3) and at different temperatures (328–353 K). A kinetic model is presented which can be used to describe the experimental results and hence a procedure for industr

ISSN:0268-2575    

DOI:10.1002/jctb.280610106

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractFactors involved in the activity decay of an ultrafiltration reactor during the hydrolysis of hemoglobin by pepsin were studied. Biochemical and hydrodynamic parameters were assessed. The product of hydrolysis showed no inhibitory effect. Autolysis and mechanical damage of pepsin were limited by the presence of hemoglobin. Activity decay was mainly a result of the leakage of pepsin through the membrane. Electrostatic charges carried by either hemoglobin or pepsin were involved in the permeation process.

ISSN:0268-2575    

DOI:10.1002/jctb.280610107

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractMixing time, circulation time and downcomer linear liquid velocity were measured in two sizes of external‐loop airlift bioreactors with Newtonian and non‐Newtonian fluids.The mixing time increased as a result of an increase of non‐Newtonian characteristics. However, the liquid circulation time was affected only slightly by non‐Newtonian flow behaviour. A semi‐empirical correlation for circulation time in external‐loop airlift bioreactors was proposed. The proposed correlation was compared with the present experimental results and those in the literature. Reasonable agreement was obtained between the predicted and experimental values of circulation times.The downcomer liquid velocity was almost independent of the downcomer‐to‐rise cross‐sectional area ratio. The correlation based on the concept of an eddy diffusivity predicted downcomer liquid velocities in Newtonian and non

ISSN:0268-2575    

DOI:10.1002/jctb.280610108

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe factors affecting the rate processes involved in the removal of phenolic compounds, e.g. initial phenol concentration, particle size, impregnation of fly ash (IFA), pH and temperature have been studied. The removal rate of phenols varied in the orderp‐nitrophenolm‐nitrophenol>o‐nitrophenol>p‐cresol>phenol>m‐cresol>o‐cresol. The process followed first order rate kinetics. The sorption data generally fit the Lagergren equation and the intraparticle diffusion rate equation from which adsorption rate constants, diffusion rate constants and diffusion coefficients were determined. Intraparticle diffusion was found to be the rate‐limiting step. These kinetic parameters were compared for various phenols under different conditions using fly ash (FA) and impregnated

ISSN:0268-2575    

DOI:10.1002/jctb.280610109

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe (1:1) (phosphomolybdate:metformin) ion pair is used as the ion exchanger in preparing conventional plastic membrane electrodes for metformin (Mf) and its performance characteristics were studied. The electrode exhibited a linear response with a good Nernstian slope over a relatively wide concentration range. The calibration graph slope was constant at 57 mV per concentration decade at 25°C for up to 5 days with continuous soaking. Then the slope decreased as the time of soaking increased, reaching 42 mV decade−1after 20 days. The changes in pH did not affect the electrode performance within the range 3.0–10.5. The standard electrode potentials were determined at different temperatures and were used to calculate the isothermal coefficient of the electrode (0.000695 V °C−1). The electrode showed a very good selectivity for Mf with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were used to determine Mf in pure solutions and in pharmaceutical prepa

ISSN:0268-2575    

DOI:10.1002/jctb.280610110

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThree different methods are described for the determination of the initial inert particulate organics, measured in terms of COD. The methods involve experimental procedures using batch reators and are designed to differentiate residual particulate products generated by metabolic activities during the treatment processes. In the first method, the final threshold value of the particulate COD is monitored in an aerated batch reactor fed by the initial total COD. The second method uses the threshold values of the total and soluble COD in two parallel batch reactors, one fed with unfiltered and the other with filtered wastewater. The third method involves running three batch reactors, two with the wastewater to be studied and the thired with glucose. One method has been experimentally tested to assess the inert particulate fractions of domestic and textile wastewaters.

ISSN:0268-2575    

DOI:10.1002/jctb.280610111

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY