bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of the allylation of phenoxide by polyethylene glycol in a two‐phase reaction
Authors: Wang Maw‐Ling , Chang Kong‐Rong 
Published: March 2009

AbstractPolyethylene glycol (PEG) was used as the phase transfer catalyst in the two‐phase allylation of phenoxide with allyl chloride. The kinetics of the reaction both in the organic phase and in the aqueous phase was studied in detail based on the ion‐extraction mechanism. The reaction rates both in the organic and aqueous phases were increased by PEG. The concentration of phenoxide in the organic phase results from adding PEG followed by a reaction second order in the concentration of phenoxide in the aqueous phase. This is due to the ability of PEGs to form complexes with sodium cations. In the aqueous phase, the PEG will enhance the solubility of allyl chloride.
Effect of solid particles on gas hold‐up in bubble columns
Authors: Jamialahmadi M. , Müller‐Steinhagen H. 
Published: March 2009

AbstractThe gas hold‐up in bubble columns containing fluidised plastic particles as solid phase was measured as a function of superficial gas velocity and solids concentration. The effects of particle size, density, wettability and concentration on gas hold‐up and bubble coalescence were studied. It was found that the addition of non‐wettable solids to the air/water mixture promotes bubble coalescence and, therefore, reduces the gas hold‐up, while the addition of wettable solids suppresses bubble coalescence and increases the gas hold‐up.
Hydrodynamics in rectangular air‐lift reactors: Scale‐up and the scale‐up and the influence of gas‐liquid separator design
Authors: Siegel Marc , Merchuk Jose C. 
Published: March 2009

AbstractExperiments were conducted on air‐lift reactors with different liquid volumes, aspect ratios, and gas‐liquid separator configurations, with constant downcomer to riser cross‐sectional area ratio and riser/downcomer height. Reactor performance was highly dependent on the gas‐liquid separator design. By changing the latter, the mode of operation could be changed from that of a concentric tube reactor (with gas recirculation) to an external loop reactor (without gas recirculation). Liquid velocity and overall gas hold‐up data were correlated to the power per liquid volume and “Disengagement Ratio”, a geometric parameter describing the separator's configuration. During scale‐up, similar gas hold‐ups and liquid velocities were found in laboratory and pilot reactors. A modified air‐lift reactor with an enlarged channel for a gas‐liquid separator also was studied.
Carrier influence in anaerobic biofilm fluidized beds for treating vapour condensate from the sulphite cellulose process
Authors: Petrozzi S. , Dunn I. J. , Heinzle E. , Kut O. M. 
Published: March 2009

AbstractThe continuous anaerobic degradation of an acidic waste water from a cellulose process was investigated in six fluidized bed reactors. Various materials including limestone, porous glass, quartz sand, activated carbon and treated coal were used as support particles. The reactors were operated for several months with vapour condensate from a sulphite cellulose process as feed. The performance and stability of the reactors with respect to degradation rate were tested for a range of loading conditions. Unbuffered, buffered and pH‐controlled conditions were compared. The results showed that the high‐density, small‐sized sand was the best carrier. Carrier porosity was not important, although surface roughness appeared to be important. No clear evidence of diffusional influence on the kinetics was observed. The highest rates and best stability was obtained with the sand carrier which had the thinnest biofilm; these rates were 21 kg COD/m3. d(unbuffered feed), or 25 kg COD/m3. d (buffered feed and pH‐controlled system). The sand system was relatively stable with respect to pH changes. With pH control, loading could be increased until a maximum reaction rate, as determined by the saturation kinetics, was achieved.
Electrochemical kinetic parameters for the cathodic deposition of copper from dilute aqueous acid sulfate solutions
Authors: Hinatsu J. T. , Foulkes F. R. 
Published: March 2009

AbstractThe use of linear‐sweep voltammetry and chronopotentiometry for the determination of kinetic parameters for the electrolytic recovery of copper from a simulated acid‐copper electroplating waste solution was demonstrated. For the electrodeposition of copper from solutions of 0.007˜0.008 mol/L CuSO4 + 0.5 mol/L H2SO4 at 25°, the recommended values of the transfer coefficient (α) and exchange current density (i0) are α = 0.46±0.06 (95% confidence interval) and i0 = 11±4 A/m2. The close agreement between these values and the available literature values indicates the reliabilaity of the voltammetric and chronopotentiometric methods.
Morphological influences in the gas phase polymerization of ethylene by silica supported chromium oxide catalysts
Authors: Webb Steven W. , Weist E. L. , Chiovetta M. G. , Laurence R. L. , Conner W. C. 
Published: March 2009

AbstractDramatic changes occur during the initial stages of olefin polymerization over heterogenous catalysts. As polymer accumulates, the catalyst fragments and the void space within the growing particle becomes filled with polymer. The changing monomer transport rate to the active sites, dissipation of heat and stress with the particle, and eventually, dispersion of catalyst fragments within the growing particle can control the polymerization. We focus on the changes in, and influence of, polymer, catalyst and void morphology during the nascent polymerization for silica supported chromium oxide catalysts. We find that the course of the polymerization depends on the initial stages yet is seldom considered in polymerization models. We review several years of morphological characterization that identify the important physical phenomena which occur during nascent heterogeneous olefin polymerization.
Modéalisation de la copolyméarisation éathylégne α‐oléafine par catalyse ziegler—natta
Authors: Lorenzini Pascal , Bertrand Pascale , Villermaux Jacques 
Published: March 2009

AbstractOn présente un modèle de copolymérisation de l'éthylène et d'une α‐oléfine qui décrit la consommation des monomères et la qualité du polymère produit, á savoir Mn, Mw, Mz, la distribution des masses moléculaires, les indices de branchement court et de doubles liaisons. Le modèle suppose qu'il existe plusieurs types de sites actifs (2 ou 3) et ne fait pas intervenir de limitation diffusionnelle. On l'applique á la copolymérisation en masse de l'éthylène et du butène‐1 sous haute pression et haute température. Les paramètres sont identifiés grǎce á des essais en réacteur agité continu.
A numerical solution of the wavy motion on a falling liquid film
Authors: Yang Ru , Wood Byard D. 
Published: March 2009

AbstractWavy motion in falling liquid films enhances heat and mass transfer significantly; therefore, it is important to successfully model this motion for the purpose of heat and mass transfer calculations. In this study, a simple and promising numerical spectral method is developed to solve the periodic wavy film flow equations. With the wave number and the wave celerity specified to be those of the most unstable waves from existing linear stability analysis, the results are found to be good when compared with the existing experimental data for small (Re < 50) and moderate (50 < Re < 150) Reynolds numbers. It is worth noting that many important absorption problems fall in the low and moderate Reynolds number regimes. For higher Reynolds number flows (Re > 150), the solutions are still obtainable but may not be realistic owing to the invalidity of the linear stability analysis and the asymptotic wavy‐state assumption in the high Reynolds number flow.
Isobaric vapor liquid equilibrium in binary mixtures of α‐pinene, limonene and 1, 8‐cineole
Authors: Farelo Fátima , And Filomena Santos , Serrano Lurdes 
Published: March 2009

AbstractIsobaric vapor liquid equilibrium at atmospheric pressure has been determined for binary mixtures of (–) α‐pinene, (+)‐limonene and 1, 8‐cineole. The Margules and Var Laar equations as well as the models proposed by Wilson, by Renon and Prausnitz (NRTL) and by Abrams and Prausnitz (UNIQUAC) were used to correlate the experimental data. The corresponding parameters for two binaries are reported here.
Oxidative coupling of methane in a bubbling fluidized bed reactor
Authors: Andorf R. , Mleczko L. , Schweer D. , Baerns M. 
Published: March 2009

AbstractThe oxidative coupling of methane to higher hydrocarbons (C2+) was studied in a bubbling fluidized bed reactor between 700°C and 820°C, and with partial pressures of methane from 40 to 70 kPa and of oxygen from 2 to 20 kPa; the total pressure was ca 100 kPa. CaO, Na2CO3/CaO and PbO/γ‐Al2O3were used as catalytic materials. C2+selectivity depends markedly on temperature and oxygen partial pressure. The optimum temperature for maximizing C2+selectivity varies between 720 and 800°C depending on the catalyst. Maximum C2+selectivities were achieved at low oxygen and high methane partial pressures and amounted to 46% for CaO (T = 780°C; PCH4= 70 kPa; PO2= 5 kPa), 53% for Na2CO3/CaO (T = 760°C; PCH4= 60 kPa; PO2= 6 kPa) and 70% for PbO/γ‐Al2O3(T = 720°C; PCH4= 60 kPa; PO2= 5 kPa). Maximum yields were obtained at low methane‐to‐oxygen ratios; they amounted to 4.5% for CaO (T = 800°C; PCH4= 70 kPa; PO2= 12 kPa), 8.8% for Na2CO3/CaO (T = 820°C; PCH4= 60 kPa; PO2= 20 kPa) and 11.3% for PbO/γ‐Al2O3(T 2= 800°C; PCH4= 60 kPa; PO2= 20 kPa).
On‐line multivariable adaptive control of a binary distillation column
Authors: Tham M. T. , Vagi F. , Morris A. J. , Wood R. K. 
Published: March 2009

AbstractAn experimental evaluation of the simultaneous control of top and bottom product compositions of a binary distillation column utilizing multi‐variable self‐tuning control algorithms is presented. The study was carried out using an 8‐tray, 22.86 cm diameter methanol–water pilot scale column with continuous capacitance analysis of top product composition and bottom composition analyzed on a 3 minute cycle, by a gas chromatograph. Column control is studied for ±25% step disturbances in feed flow rate. Terminal composition regulation using both ‘positional’ and ‘incremental’ forms of a generalized minimum variance self‐tuning control algorithm is compared with that achieved using a conventional digital PI/PID multiloop control strategy.
Catalytic upgrading of biomass‐derived oils to transportation fuels and chemicals
Authors: Sharma R. K. , Bakhshi N. N. 
Published: March 2009

AbstractThis paper provides a review of the catalytic upgrading of biomass‐derived oils such as wood pyrolytic oils, plant/vegetable oils and tall oil to transportation fuels and useful chemicals. Both zeolite and hydrotreating type catalysts have been found suitable for upgrading which was usually done in fixed bed reactors. The hydrotreatment of pyrolytic oils at 250‐450°C and 15‐20 MPa H2 pressures has been reported to yield up to 55 wt. % of liquid product containing 40‐50 wt. % of gasoline range hydrocarbons. In the case of HZSM‐5, the upgrading has been carried out at atmospheric pressure and 350‐500°C and over 85 wt. % conversions of plant oils and tall oil have been achieved under optimum conditions. Liquid product yields from these oils were up to 70 wt. % of feed which contained 40‐50 wt. % aromatic hydrocarbons. With the high pressure pyrolytic oil, pitch conversions of over 75 wt. % have been observed with HZSM‐5 using co‐feeds such as tetralin. However, there is only scant information available on the kinetic and mechanistic aspects of upgrading of these oils.
Catalytic oxidation of carbon monoxide under periodic operation
Authors: Silveston P. L. 
Published: March 2009

AbstractA growing literature demonstrates resonance of the rate of CO oxidation with frequency of composition switching and that a global increase in rate under composition modulation is possible. Differences are found for the various metal catalysts used: CO oxidation is stimulated at frequencies between 0.1 and 1.0 Hz over noble metals, whereas stimulation occurs at frequencies below 0.05 Hz with oxide catalysts. Multiple resonances with an apparent harmonic relationship, “wrong‐way” response, or very slow relaxation to reproducible cycles have been observed. These differences suggest mechanisms through which rate improvements arise are not the same for all catalysts.
Modified shape factors for improved viscosity predictions using corresponding states
Authors: Monnery Wayne D. , Mehrotra Anil K. , Svrcek William Y. 
Published: March 2009

AbstractA new approach for evaluating the shape factors in the Extended Corresponding States Method is presented for improving the viscosity predictions of pure liquid hydrocarbons. Of the two shape factors in the method, the size shape factor ϕ is shown to be unnecessary. The energy shape factor θ is shown to correlate with the reduced temperature. Next, the correlation parameters are generalized for each family of hydrocarbon compounds. A further simplification in the viscosity calculation is accomplished by use of propane as the reference fluid whose density is calculated from the COSTALD method. The predicted viscosities of 46 pure liquid hydrocarbons are well within 6% of the data, and an order of magnitude better than those from available methods.
Computation and optical interferometric determination of concentration profiles near a vertical cathode
Authors: Nagatsugawa I. , Piron D. L. , Bures J. 
Published: March 2009

AbstractConcentration profiles near a copper cathode immersed in a 0.3 mol/L CuSO4 aqueous solution were determined by theoretical computation and by measurement with a Jamin optical interferometer. The semi‐infinite diffusion and convective diffusion equations corrected by an experimental factor corresponded well with the experimental results.
The equilibrium phase properties of the propane‐methanol and n‐Butane‐methanol binary systems
Authors: Lev Ah‐Dong , Robinson Donald B. , Chung Samuels Y.‐K. , Chen C.‐J. 
Published: March 2009

AbstractVapor and liquid equilibrium phase compositions were determined at 310.7, 352.2, 393.0 and 474.3 K for the propane‐methanol system and at 469.9 K for the n‐butane–methanol system. Measurements were made at pressures from the vapor pressure of the less volatile component to the maximum pressure where two phases coexisted either as an azeo‐trope or at the critical condition, depending on the system. Azeotropic behavior was observed at 310.7 and 352.2 K for the propane‐methanol system. Equilibrium ratios were calculated at each temperature from the phase composition data. The temperature dependence of the azeotrope pressure and of the corresponding azeotrope composition was expressed analytically.
Hydrodynamic behaviour of a horizontal pulsed solvent extraction column. part 1: Flow characterization, throughput capacity and holdup
Authors: Melnyk A. J. , Vijayan S. , Woods D. R. 
Published: March 2009

AbstractA horizontal pulsed solvent extraction column (HPC) has great potential in replacing vertical pulsed columns (VPC) in the separation of heavy elements in the nuclear industry. Published work examining the performance of the HPC suggests that the mass transfer efficiency for this column is comparable to the VPC, but information on the hydrodynamic characteristics of the HPC is sparse. This paper describes the flow characteristics of the HPC and presents experimental results and correlations for flooding conditions and holdup of the dispersed phase. Correlations obtained for the HPC for these hydrodynamic parameters are compared to published results for the VPC.
Hydrodynamics of spouted and spout‐fluidized beds at high temperature
Authors: Ye B. , Lim C. J. , Grace J. R. 
Published: March 2009

AbstractHydrodynamic parameters were investigated in a 0.15 m diameter half‐column spout‐fluidized bed at temperatures up to 880°C for ratios of auxiliary air flow to total air flow from 0 to 0.62 and four narrow size ranges of silica sand. Equations in the literature gave poor agreement with the minimum spouting velocity over the entire temperature range. For large particles Um generally increased with temperature, while for small particles it decreased. Auxiliary air had more influence at elevated temperatures than at room temperature. Pulsations leading to choking appeared to cause spout termination at elevated temperatures. The McNab and Bridgwater (1977) equation correctly predicted the observed trends for maximum spoutable bed depth at high temperatures.
Kinetics of the gas‐phase reaction between nitric oxide, ammonia and oxygen
Authors: Duo W. , Dam‐Johansen K. , Østergaard K. 
Published: March 2009

AbstractFor the purpose of developing a simple and quantitative description of the rate of reactions occurring in the Thermal DeNOx process, the kinetics of the homogeneous reaction between NO and NH3 with excess of O2 has been studied in an isothermal plug flow reactor.Temperature windows of NO reduction were observed with the optimum temperature decreasing with increasing residence time. The degree of reduction of NO increases with residence time at lower temperatures but is sensitive to residence time only at very short residence times at higher temperatures. The degree of conversion of NH3 increases with both temperature and residence time.A simple model has been proposed to describe the reaction rates:rNO = kax [NH3] ‐ kr [NH3] [NO]r =‐kax [NH3]‐ kr [NH3] [NO]The two rate constants in the model were estimated based on the experimental data obtained in the present plug flow reactor at about 4% (vol.) oxygen:kax = (2.21 ± 0.33) × 1014 exp [‐(38160 ± 170)/T], I/skr = (2.45 ± 0.49) × 1014 exp [‐(29400 ± 250)/T], m3mol. sIt is verified that the kinetic model can give a satisfactory prediction of the experimental results under different conditions.
Collection efficiencies and particle size distributions from sampling cyclones — comparison of recent theories with experimental data
Authors: Salcedo R. L. 
Published: March 2009

AbstractThe grade collection efficiencies and particle size distributions from Stairmand‐type cyclones are compared with predictions from four theories, viz. the models of Leith and Licht (1972), Dietz (1981) Mothes and Loffler (1988) and Li and Wang (1989). It is shown that the theory of Mothes and Loffler, which recogizes different flow regions within a cyclone, coupled with a realistic estimate of the particles turbulent diffusivity, is capable of providing good estimates of both the grade‐efficiency curves and particle size distributions of the cyclone catch and/or outlet dusts. The lack of adequate theories or empirical formulae to estimate the effective turbulent diffusivity under cyclone flow seems the major factor hindering the use of the Mothes and Loffler theory for predictive purposes. High loadings and agglomeration of fines, if present, are responsible for strong departures from theoretical predictions.
Kinetics of methane hydrate formation in aqueous electrolyte solutions
Authors: Dholabhai P.D. , Kalogerakis N. , Bishnoi P.R. 
Published: March 2009

AbstractExperimental data on the kinetics of methane hydrate formation in aqueous electrolyte solutions are reported. The experiments were carried out in a semi‐batch stirred tank reactor in three NaCl and two KCl solutions as well as in a solution containing a mixture of NaCl and KCl at three different nominal temperatures from 270 to 274 K and at pressures ranging from 3.78 to 7.08 MPa. The kinetic model developed by Englezos et al. (1987a) was adapted to predict the growth of hydrates. The model is based on the crystallisation theory coupled with the two‐film theory for gas absorption in the liquid phase. The kinetic rate constant which appears in the model was that obtained earlier for methane hydrate formation in pure water. The effect of the electrolytes was taken into account through the computation of the three‐phase equilibrium conditions and the corresponding fugacities. Overall, the model predictions match the experimental data very well with the largest prediction error being less than 10%.
Xanthan production in an external‐circulation‐loop airlift fermenter
Authors: Kessler Wolfgang R. , Popović Milan K. , Robinson Campbell W. 
Published: March 2009

AbstractA preliminary study of xanthan production by Xanthomonas campestris was performed in an external‐circulation‐loop airlift (ECL‐AL) fermenter. An average of 25 g/L xanthan of good viscosity characteristics was obtained in a total fermentation time of 49 hours. Oxygen limitation was observed after 36 hours of fermentation time. It is conclusively demonstrated that the ECL‐AL fermenter can be used to economically produce xanthan. The key operating and design features are the liquid height, downcomer‐to‐riser cross‐sectional area ratio (AD/AR) and the orfice diameter of the air sparger.
Etude de l'influence des paramètres de fonctionnement d'un réacteui électrochimique à lit fixe conique
Authors: Benzina M. , Ratel A. , Lacoste G. 
Published: March 2009

AbstractLa récupération des ions métalliques en solution diluée peut être effectuée à l'aide d'un réacteur électrochimique à cathode volumique. Ce travail fait suite à l'étude relative aux réacteurs électrochimiques à tronc conique à lit transporté. Il intéresse plus précisément l'influence des pararnètres de fonctionnement tels que le sens de l'écoulement (ascendantou descendant), et l'angle du cône. Cette étude a permis de dégager les paramètres géométriques conduisant aux meilleures performances du réacteur, travaillant au courant limite de diffusion.
Steady‐state methanation kinetics over a Ni/Al2O3 catalyst
Authors: Yadav Rajiv , Rinker R. G. 
Published: March 2009

AbstractExtensive kinetic data for the methanation reaction over a Ni/Al2O3 catalyst were obtained in a specially designed gradientless reactor operating at steady state. The reactor pressure was 101.3 kPa, and three temperatures were used, namely, 503, 513 and 523 K. The following three‐parameter phenomenological model based on a proposed Langmuir‐Hinshelwood mechanism adequately describes the data: r = L2 K3 K40.5 k5 P0.5H2 Pco/ [1 + K3 (k5 / k6)Pco + K40.5 P0.5H2 ]2With dissociative adsorption of hydrogen and hydrogen‐assisted dissociation of adsorbed carbon monoxide, the postulated mari is the CH surface group, and the rds is the hydrogenation of the surface CH group.
Sulfation of high purity limestones under simulated pfbc conditions
Authors: Krishnan S. V. , Stratis  , Sotirchos V. 
Published: March 2009

AbstractThe direct sulfation of three high purity limestones, all having more than 95% CaCO3 but differing in petrographic texture, was studied in a thermogravimetric analyzer under simulated PFBC (Pressurized Fluidized‐Bed Combustion) conditions, that is, in the presence of enough CO2 to prevent decomposition of CaCO3. Experiments were carried out over a wide range of particle size (53‐350 μm) at two temperatures (750 and 850°C), and two concentrations (1500 and 6000 mL/m3 (ppmv) SO2). The particle size and temperature had a strong influence on the variation of the conversion with time. In contrast, the effect of concentration was rather marginal over the whole duration of the process, and the analysis of the initial reaction rate data gave a reaction order of 0.4, with respect to SO2, for all solids. The measured reaction rates were compared with those obtained in a past study for the sulfation of the calcines of the three solids under similar conditions. The initial rate of the calcine‐SO2 reaction was found to be higher than that of the limestone‐SO2 reaction, but since the former drops sharply as the pores at the external surface of the particles are filled with solid product, higher conversions may be obtained in some cases during direct sulfation for large reaction times.