摘要:

AbstractDispersed‐phase holdup and extraction efficiency were measured in a pilot‐plant scale rotating disc contactor (RDC) with perforated skirts (RDCS) with kerosene‐o‐cresol‐water system. The data for the RDCS were examined using the data in this work and the available correlations proposed for the plain RDC. A comparison between the data measured in the RDCS and those in the RDC indicated that the RDCS has rather better extraction efficiency compared wit

ISSN:0268-2575    

DOI:10.1002/jctb.280480302

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractA decrease in the crystallite size increases the activity as well as the selectivity and reduces the deactivation of ZSM‐5 zeolites in the dewaxing of petroleum fractions. Isomorphous replacement of Al3+by Fe3+reduces the dewaxing activity but enhances the yield of dewaxed oil and gasoline at the expense of C1‐C4gases. Within limits, the Si/Al ratio does not affect the performance of ZSM‐5 zeolite in the hydrodewaxing pr

ISSN:0268-2575    

DOI:10.1002/jctb.280480303

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this study the film‐pore diffusion model was applied to describe system transport kinetics of three basic dye‐carbon systems, namely Basic Blue 69, Basic Red 22 and Basic Yellow 21. The mass transfer parameters evaluated were the external mass transfer coefficient kf(cm s−1) and the effective diffusivity Deff(cm2s−1).A single kfvalue was sufficient to describe each dye system: these were 0.15 × 10−2, 0.20 × 10−2and 0.50 × 10−2cm s−1for BB69, BR22 and BY21, respectively. The effective diffusivity was found to have values much larger than those of pore diffusivities calculated from liquid diffusivities and its value decreased with increasing initial dye concentration. This was attributed to the effect of surface diffusion, hence pore diffusivity was exchanged by the effective pore diffusivity in the model.The present model was solved by the exponential curve fit technique; results were expressed in the form of experimental and theoretical Sherwood Numbers compared in ter

ISSN:0268-2575    

DOI:10.1002/jctb.280480304

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThree types of organic polymers and bead‐shape silica gels were activated by graft polymerization of 2,3‐epoxypropyl methacrylate; in some cases, epoxide groups on the support surface were modified to NH2groups. Eight active matrices so obtained were assessed as supports for immobilized enzymes using peroxidase, glucoamylase and urease. The immobilization yield of protein and specific activities of enzymes were better with supports containing NH2groups than with those containing epoxide spacer arms. Maximum enzyme immobilization and storage stabilities were obtained with silica‐gel beads activated by graft polymerization of 2,3‐epoxypropyl methacrylate. With all eight matrices tested, the immobilized enzymes showed good stability with not less than 82% of the original activity persisting after 28 days. The developed matrices have potential for use in process‐scale biotechnological o

ISSN:0268-2575    

DOI:10.1002/jctb.280480305

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractLightfastness for a number of azo dyes bearing heteroaromatic substituents was modelled by the partial least squares method (PLS) in terms of structural descriptors, involving the principal properties of usual substituents, and the chemical shifts of the heteroaromatic moieties. The model permits the prediction of possible structures, with higher values of the technological property, worthy of synthesis.

ISSN:0268-2575    

DOI:10.1002/jctb.280480306

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractSelected specific α‐amylase and glucoamylase enzymes were immobilized and combined with immobilized cyclodextrin glycosyltransferase to continuously produce cyclodextrin (CD). The liquefied starch was cyclized to CD by ICGTase and then treated by immobilized α‐amylase and glucoamylase to contain CD and glucose only. β‐CD and soluble CD (α‐ and γ‐CD) in the final CD solution could be easily separated. The pH‐activity curve, temperature‐activity curve, batch re‐usability and continuous operation stability of immobilized enzymes were discussed. The continuous production of CD by an immobilized enzyme system was also reported. The optimal conditions for using immobilized α‐amylase and glucoamylase simultaneously were 40°C and pH 4.5 adjusted by 1 mol dm−3HCl/NaOH. A 70% yield of CD could be obtained from 1% (w/v) of liquefied starch under continuous operation at 0.055 h−1space velocity, and almost all the oligosaccharides (β 98%) were converted to glucose. In this study, the separation of α‐CD, γ‐CD and glucose, using organic solvent from the final product after precip

ISSN:0268-2575    

DOI:10.1002/jctb.280480307

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractA laboratory‐scale cyclone column reactor was tested to determine how its oxygen transfer characteristics were affected by surfactants in the liquid medium. The volumetric oxygen transfer coefficient was greatly decreased by small quantities of the synthetic surfactants dodecyltrimethylammonium bromide and sodium dodecylsulfate, and the biosurfactant surfactin produced by Bacillus subtilis (ATCC 21332). Since the gas holdup fraction was generally increased due to foaming, the effectiveness of the surfactants was probably due to an increase in the interfacial film resistance. B. subtilis was grown in the cyclone column to 0.6 g dm−3with a significant level of surfactin produced while maintaining at least 75% oxygen saturation in the broth. Process optimization and scale‐up of surfactin production will have to consider oxygen transfer as a key para

ISSN:0268-2575    

DOI:10.1002/jctb.280480308

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractUrease was covalently immobilized on glutaraldehyde‐pretreated chitosan membranes. The optimum immobilization conditions were determined with respect to glutaraldehyde pretreatment of membranes and to reaction of glutaraldehyde‐pretreated membranes with urease. The immobilized enzyme retained 94% of its original activity. The properties of free and immobilized urease were compared. The Michaelis constant was about five times higher for immobilized urease than for the free enzyme, while the maximum reaction rate was lower for the immobilized enzyme. The stability of urease at low pH values was improved by immobilization; temperature stability was also improved. The optimum temperature was determined to be 65°C for the free urease and 75°C for the immobilized form. The immobilized enzyme had good storage and operational stability and good reusability, properties that offer potential for practical applic

ISSN:0268-2575    

DOI:10.1002/jctb.280480309

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe intermetallic pseudo‐binary alloys of the general type ZrRh3‐xPdxand ZrRh3‐xRux(0<×<3) have been prepared by argon arc melting and melt quenching of the constituent elements.The alloys were powdered and employed as catalysts for (i) hydrogenation of oct‐1‐yne in the liquid phase at 101.32 kPa total pressure and 70°C, (ii) hydrogenation of buta‐1,3‐diene in the gas phase at 101.32 kPa total pressure in the temperature range 45–225°C, and (iii) hydrogenolysis of n‐pentane in the gas phase at 101.32 kPa total pressure and in the temperature range 200–400°C.Activity and selectivity measurements were made with respect to (i) alkene formation for the hydrogenation reactions, and (ii) C2+ C3‐alkane formation for the hydrogenolysis reaction. The activity of the alloy series appears to correlate to some degree with the electronic properties and hydrogen sorption capacity of the intermetallic alloys. Auger electron spectroscopy measurements revealed that for ZrRh3‐xPdxalloys both the surface and bulk compositions were in good agreement; this behaviour is contrasted briefly with that of CeRh3‐xPdxalloys which, unlike ZrRh3‐xalloys, suffered significant oxygen interaction in the surface and sub‐surface layers, although this did not affect Rh:Pd ratios.Catalysts that were active for hydrogenation were inactive for hydrogenolysis and vice versa. However, selectivity values for the hydrogenation reactions generally reflected the behaviour of the predominant noble transition metal. Again, the behaviour of ZrRh3‐xPdxand CeRh3‐xalloys is contrasted, since the latter were more selective for butene formation from buta‐1,3‐diene, and attributed to the oxygen Contamination of the surface. Further more, the selectivity of both ZrPd and CePd, for 1‐octyne and butu‐l j‐dene hydrogenation was significantly greater than that of palladium by virtue of the fact that the intermetallics were found

ISSN:0268-2575    

DOI:10.1002/jctb.280480310

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe poisoning of a commercial Pd/Al2O3catalyst by pyridine and thiophene during the selective hydrogenation of styrene to ethylbenzene was studied. It was found that the Pd electronic state is the main factor controlling the interaction between the metal and the poisons. Pyridine added to the non‐poisoned feed in a pulse produces a modification in the Pd electronic state and a decrease in conversion, but, within certain limits, inhibits the adsorption of more pyridine or thiophene molecule

ISSN:0268-2575    

DOI:10.1002/jctb.280480311

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY