The dehydration of 2-methyl 1-butanol (2M1BOH) in the liquid phase was studied by using an ion-exchange resin, Amberlyst 15 in the H+ form. Experiments were carried out in a batch reactor with the dry resin as a catalyst. Considering the inhibition effect of water, the rate expressions based on the Langmuir-Hinshelwood model were formulated. The sorption equilibrium model between liquid and resin phases during resin swelling was included in kinetic modelling. The cross-linked ion-exchange resin was highly selective to water at the beginning of the reaction. The experimental results agreed well with the calculated ones.
Reactive distillation was used as a method to accelerate the reaction rate of 2-methyl-1-butanol (2M1BOH) dehydration. Since it is strongly inhibited by water, the trade-off between reaction rate and liquid-vapour mass transfer was investigated under experimental input variables, such as reboiler heat duty, the mass of the catalyst and reflux ratio. The reaction rate variations inside the column were simulated by using the equilibrium model of the ASPEN PLUS simulator. The effectiveness of reactive distillation was justified by the comparison of its performance with corresponding conventional reactors. A saving of 80% in reboiler heat duty was found when a decanter was added to the column. An industrial scale simulation was done to optimise the proposed process.
Electrochemical oxidation of carbon monoxide between 0.3 and 0.5 V vs. RHE (reversible hydrogen electrode) was investigated in hot 0.005 M H2SO4–0.2 M Na2SO4 solution at 423 and 473 K under CO pressures ranging from 0.08 to 1.25 MPa. The reaction could be well explained by both the Langmuir–Hinshelwood mechanism for the reaction between carbon monoxide and water and the Langmuir isotherm for adsorption of carbon monoxide on a Pt electrode. Activation energy around 60 kJ·mol–1 was observed. This value almost agrees with the apparent activation energy for electrochemical oxidation of methanol on a Pt electrode obtained between 393 and 463 K by Watanabe et al. (1997). We confirmed that CO adsorption decreases with the increase of temperature.
A highly stable catalyst for hydrogen production by steam reforming of 2-propanol is searched by reaction tests at 773 K and 673 K. At 773 K, Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3 result in the stable hydrogen production. Co/Al2O3 initially results in the highest hydrogen production, however, the production decreases gradually as the time on stream increases. Rh/Al2O3 exhibits the highest stability for the hydrogen production also at 673 K, and is practical for the steam reforming.
Zirconia membranes were prepared on porous α-alumina tubes using a sol-gel technique, and platinum was then impregnated in the pores of the membranes by dipping in 0.1 mol L–1 H2PtCl6 solution, followed by calcination in air. This procedure was repeated four times maximum. The membranes were then exposed in hydrogen prior to permeation tests. Permeation rates through the membranes were determined for single-component gases (H2, CO2 and i-C4H10) at temperatures of 308–573 K. The permeation rates of the unmodified zirconia membrane obeyed the Knudsen diffusion mechanism. However, hydrogen permeation changed from the Knudsen diffusion to surface diffusion after the third Pt modification, and to the activated diffusion after the fourth Pt modification. The ideal H2/CO2 and H2/i-C4H10 selectivities for the membrane, which was Pt-modified four times with calcination at 573 K, were approximately 30 and 1000, respectively, at a permeation temperature of 523 K. When a mixture of H2 (80 mol%) and CO2 (20 mol%) was fed, the membrane showed an H2/CO2 selectivity higher than 400 and an H2 permeance of 4.21 × 10–8 mol m–2s–1Pa–1 at 523 K.
A desulfurization process for light oils, based on photocatalytic oxidation of sulfur-containing compounds using TiO2 and an oil/acetonitrile two-phase extraction, has been investigated. Dibenzothiophenes (DBTs), when dissolved in acetonitrile, are oxidized by photoirradiation at wavelengths λ > 320 nm in the presence of TiO2, to form the corresponding sulfoxides and sulfones, which do not distribute into the non-polar light oil owing to their high polarity. When light oil and acetonitrile are mixed and photoirradiated in the presence of TiO2, the sulfur compounds are extracted successively and photooxidized in acetonitrile. By this means, deep desulfurization is achieved: the sulfur content of light oil being reduced from 0.18 to less than 0.05 wt%. The present process, however, has a difficulty in the desulfurization of high-aromatic-content light oils.
A new semi-dry process to produce very fine calcium carbonate powder is developed. Ca(OH)2 slurry droplets are continuously fed into a spouted bed of coarse medium particles, and react with CO2 in fluidizing gas to produce fine CaCO3 powder. The CaCO3 powder is dried with fluidizing gas, and fine CaCO3 powder is entrained from the bed to be collected with a bag filter. The effect of operating conditions, such as the concentration of the Ca(OH)2 slurry, CO2 concentration in the fluidizing gas, approach to saturation temperature, superficial gas velocity and static bed height, on the conversion of Ca(OH)2 to CaCO3 and the particle size of product CaCO3 powder are investigated. Very fine CaCO3 powder and high Ca(OH)2 conversion are obtained in the case of low concentration of Ca(OH)2 in the feed slurry and high concentration of CO2 in the fluidizing gas. This method can produce very fine calcium carbonate powders with the mean particle size around 1 μm and the Ca(OH)2 conversion around 90%.
A new device for continuous measurements of a solid mass flow in circulating fluidized beds has been proposed. The solid mass flow meter consists of a cone and a moving scoop. Since it does not have any valves or throttles it does not disturb the gas flow through the CFB loop, which may interfere the solid circulation rate. A mathematical model of scoop motion was solved numerically to make clear its characteristics. A simple analytical solution was provided in order to determine the limiting conditions of the scoop motion. The performance of the device was tested with a 0.2-m-i.d. circulating fluidized bed for various powders (ZnO, FCC, CaCO3, and SiO2) belonging to the Geldart groups A, B and C. The device performed well for all the solids tested over the range of solid mass flow rates of 0–0.942 kg/s, i.e. corresponding to 0 < Gs < 30 kg/(m2·s) for the CFB apparatus used in the present study.
Bovine cathepsin C production from recombinant methylotrophic yeast, Candida boidinii, was conducted in a jar-fermentor culture of fed-batch mode. Changing the carbon source from glucose to methanol induced cathepsin C expression. After changing the carbon source, intermittent addition of methanol was effective for the production of cathepsin C. During the growth phase, the level of dissolved oxygen was kept between 40 and 80% of the saturated DO level. With this control, the lack of oxygen could be avoided and cells were grown up to ca. 50 g dry cell weight/l, approximately two fold higher than that without the DO control. However, the expression of cathepsin C in the induction phase was reduced. Half volume of the medium was replaced with the same volume of the fresh medium just before the induction. The production was improved by the medium exchange and the activity of cathepsin C in the supernatant reached over 370 U/l after 16 days of induction, corresponding to a two-fold higher value than that obtained without medium exchange.
A simple and rapid calculation method, which is based on the Beer-Lambert law and Rose and Lloyd’s hypothesis, was proposed for the determination of light attenuation profiles in suspensions of photosynthetic microorganisms. In this method, extinction coefficients measured spectrophotometrically at a single concentration of suspended cells over the whole range of wavelengths emitted from different light sources were used for reflecting the physical and biological characteristics of cells, which may change during a course of cultivation. The validity of this approach was confirmed by use of suspensions of two kinds of photosynthetic cells, the purple bacterium Rhodobacter capsulatus and the green alga Chlamydomonas reinhardtii, illuminated by three light sources with different irradiation spectra. This approach can estimate well the profiles of the light attenuation in these systems, irrespective of the spectra of the light sources, until the transmitted light intensity falls to one tenth of the incident intensity.
An approach for predicting the drug concentration in the vitreous body has been proposed for intravitreal drug delivery by biodegradable polymer implants. The release rates of a model drug, dexamethasone sodium m-sulfobenzoate (DMSB), from poly lactic acid implants were measured under in vitro and in vivo conditions using Japanese albino rabbits. The pharmacokinetic model assuming the cylindrical vitreous body was then solved together with the in vivo release rate and the other model parameters determined separately. The mathematical model successfully described the drug concentration–time profile in the vitreous body. The in vivo concentration–time profile in the rabbit vitreous body agreed with the one predicted on the basis of the in vivo release profile. The in vivo concentration–time profile in the vitrectomized eye was well predicted from the in vitro release profile. These findings may suggest that if the in vivo release profile is known or predicted, the in vivo concentration in the vitreous body can be evaluated by the help of computer simulation without carrying out the in vivo release experiment which is usually time-consuming for controlled release formulations.
The inclusion of binary liquid flavor such as phenyl ethanol/d-limonene or methyl n-hexanoate/d-limonene into α-, β- and γ-cyclodextrin was investigated. The inclusion of the target guests (phenyl ethanol and methyl n-hexanoate) was inhibited by the presence of the inhibitor, d-limonene. Three types of inhibited inclusion were observed depending on the combination between cyclodextrins and the binary liquid flavors. The inclusion fractions of the target compounds (the molar ratio of the included target guest to cyclodextrin) were correlated by the inhibited enzyme kinetic equation of Michaelis–Menten type, which commonly used to analyze the inhibition of the enzymatic reactions. At the higher concentrations of the target guest, the competitive inclusion model could correlate the inclusion fraction independent of the type of cyclodextrin. However, at a low concentration, the presence of d-limonene inhibited the inclusion of the target guests in a noncompetitive manner for α- and β-cyclodextrin and in an uncompetitive manner for γ-cyclodextrin, respectively.
There are two kinds of mating types in yeast cells, a-type and α-type, and they can make a diploid, which carries both the genes originated from a-type and α-type. We propose a new method to obtain a larger size of combinatorial libraries by mating these yeast cells. By transforming libraries of genes of heavy and light chains to a- and α-types respectively, for example, it should be possible to obtain a larger size of libraries of antibodies by mating them. To confirm our method, the expression vectors containing heavy chain gene (μ) and light chain genes (κ and λ) of human antibodies were transformed into a-type and α-type strains of S. cerevisiae, respectively, and these transformants were mated by mixing the cultured cells of both types. The effects of media, cell concentration and the ratio of a-type cells to α-type cells on the mating efficiency were studied. The direct contact between a- and α-type cells was essential to initiate mating of cells, and the probability of contact among cells determined the mating efficiency, when cells are well nourished. Stable diploids were formed by the combination of plasmids of the 2 μm types, as well as the combination between the 2 μm type and the ARS1 type.
Trace metal compounds, which are emitted from combustion systems such as waste incinerators, coal combustors, and so forth, enrich in fine particulates, usually formed during various stages of combustion. Owing to the difficulties of capturing fine particulates by conventional particulate dust collection systems, these are exhausted in the atmosphere. Fundamentals of the emission and control of trace metal compounds of lead and cadmium were studied at relatively low temperature (1073–1273 K), using a thermobalance. In order to capture these trace metal compounds, seven types of sorbent, namely alumina, silica, kaolin, limestone, scallop, zeolite and apatite, were used. As a result, the natural aluminosilicate materials like kaolin and zeolite were found to be effective in capturing lead and cadmium chemically. Although the presence of HCl decreases capture efficiencies, the products didn’t react with HCl. The types of kaolin had a little influence on the capture efficiency and processes in general. On the other hand, the calcium-based sorbents like limestone, scallop and apatite, could capture both the trace metals and chlorine. On the presence of HCl, the capture efficiencies of these sorbents decreased sharply. Both alumina and silica have low ability to capture trace metal compounds. Moreover, in reducing atmosphere, all sorbents showed low capture abilities since the products were reduced.