Journal of The Chinese Institute of Chemical Engineers最新文献

Caffeic acid phenethyl ester was successfully synthesized from caffeic acid and phenethyl alcohol catalyzed by Novozym 435. Caffeic acid was found to yield much higher conversion in non-polar solvents than in polar ones, albeit its low solubility in non-polar solvents. Among all solvents tested, isooctane gave the highest conversion and was chosen as the solvent in this study. A reaction temperature of 70 °C was chosen to give high solubility of caffeic acid and hence high conversion. The optimum molar ratio of acid to alcohol was found to be 1:92. More alcohol resulted in the inactivation of enzyme. An acid to enzyme ratio of 1:15 (w/w) gave nearly a 100% conversion in 48 h. The conversion was found to be independent of stirring speed. Low stirrer speed of 50 rpm was enough and necessary to provide good mixing. Results from batch reuse stability study show that Novozym 435 could maintain more than 90% of its original activity up to the third batch. The enzyme lost its activity faster under higher stirring speed. Reactions carried out without stirring gave better enzyme batch stability, however, the conversions were always less than 90%.

In this investigation, we studied the oxidative steam reforming reaction of ethanol in a Pd–Ag/PSS membrane reactor for the production of high purity hydrogen. Palladium and silver were deposited on porous stainless steel (PSS) tube via the sequential electroless plating procedure with an overall film thickness of 20 μm and Pd/Ag weight ratio of 78/22. An ethanol–water mixture (n_water/n_ethanol = 1 or 3) and oxygen (n_oxygen/n_ethanol = 0.2, 0.7 or 1.0) were fed concurrently into the membrane reactor packed with Zn–Cu commercial catalyst (MDC-3). The reaction temperatures were set at 593–723 K and the pressures at 3–10 atm. The hydrogen flux in the permeation side increased proportionately with increasing pressure; however, it reduced slightly when increasing oxygen input. This is probably due to the fast oxidation reaction that consumes hydrogen before the onset of the steam reforming reaction. The effect of oxygen plays a vital role on the ethanol oxidation steam reforming reaction, especially for a Pd–Ag membrane reactor in which a higher flux of hydrogen is required. The selectivity of CO₂ increased with increasing flow rate of oxygen, while the selectivity of CO remained almost the same.

Learning is a complicated process composed of vision, interpretation, comprehension and memory. This study for the first time compared activities in the brain for equation reading and writing by selected professionals using functional magnetic resonance imaging (fMRI). Finger writing did not change the message pathway in brain, but on the other hand intensified stimuli on the information integration and language processing centers by hand movement. Writing practice can assist students to integrate and comprehend the lectures delivered in the chemical engineering classrooms. However, this practice cannot help a student to extract abstract meaning in the equation.

The kinetics of the H₂ oxidation reaction at Nafion film covered Pt-black rotating disk electrodes (RDEs) in 0.5 M H₂SO₄ at 298 K was investigated by varying the Pt loading, Nafion film thickness, and rotating rate. The equation describing the H₂ oxidation kinetics at an RDE with a Nafion film covered porous Pt layer was derived, assuming a Tafel–Volmer mechanism and taking into account the mass transfer resistances in the aqueous electrolyte, Nafion film, and Pt layer. The H₂ oxidation reaction at the Pt layer was proved to be reversible and the measurable current density was determined entirely by the mass transfer of H₂ in the aqueous electrolyte and the Nafion film; the apparent kinetic current density measured was due to the experimental error. More accurate results of kinetic analysis were obtained in this work than our results reported previously.

This study simulated in situ bioremediation for diesel-contaminated soil by a column operation. Several bioremediation approaches were conducted to examine the feasibility. Four lab-scale soil columns were operated specific to the following approaches: nutrient enhancement (NE), bioaugmentation (BA), biostimulation (BS), and sterilized soil (SS). Within 330 days of operation, the residual total petroleum hydrocarbon-diesel (TPH_d) was degraded from 10,290 mg TPH_d/dry soil to 3026, 1851, 4105, and 6506 mg TPH_d/kg dry soil by Columns NE, BA, BS, and SS, respectively. The diesel-degradation efficiency was 67%, 80%, 45%, and 24%, accordingly. Microbial diversity was monitored with molecular biotechnology DGGE. It was found that introduced bacteria CC-CF3 and CC-JG39 become undetectable after 90 days of operation, but another introduced bacteria, CC-RS1, evidently remained with small signals during the last time stage of operation.

The carbothermic reduction of zinc sulfide in the presence of sodium carbonate has been studied using X-ray diffractometry (XRD), thermogravimetric analysis system (TGA), atomic absorption spectrometry (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), elemental analyzer (EA) and scanning electron microscopy (SEM). Experimental results of AAS indicated that the reduction in the presence of sodium carbonate proceeded significantly faster than in the presence of calcium carbonate and its sulfur fixation efficiency was acceptable. The results of XRD revealed that zinc sulfide was first transformed from β-type to α-type, then reduced to zinc vapor. The sequence of the variation of sodium containing material was found to be

The catalytic mechanisms or pathways of water-gas shift (WGS) reaction have been the focus of intense research interest because of its immense importance in hydrogen production. At the outset, 116 stoichiometrically feasible independent pathways (IP_i's) have been exhaustively generated within 2 s on a PC through a novel graph-theoretic method based on P-graphs (process graphs) from a set of 17 plausible elementary reactions. This is followed by the determination of IP₁₈ among these 116 stoichiometrically feasible IP_i's as the plausibly dominant pathway via energetic analysis.

In this study, we have formulated a general geometric based shortcut method that can be used for multi-feed multi-component columns. Simulated annealing algorithm is used to obtain the solution. This method can be used to find the minimum reflux ratio, minimum number of stages at total reflux, and number of stages at given reflux ratio, as well as the reflux ratio with given number of stages. Reliable solutions were obtained for different types of splits in both single-feed columns and double-feed columns. This method serves as the basis for developing a general method for estimating minimum reflux for other more complex columns.

The polymerization kinetics for the preparation of poly(p-divinylbenzene (p-DVB)) via a miniemulsion polymerization process was studied by the gravimetric analysis and the transmission electron microscopy (TEM) analysis. The influence of the variation of both initiator concentration and polymerization temperature on the polymerization rate was investigated and also the activation energy of p-divinylbenzene was estimated. The evolution of polymer particles was observed by the electronmicrographs and the relatively large size of polymer particles without the formation of coagulum was obtained in the miniemulsion polymerization process.

In this study, several trialkylamines were immobilized on chloromethylated polystyrene (CMPS), silica gel, and alumina to prepare triphase catalysts for catalyzing the etherification reaction of allyl bromide (the organic reactant) and sodium phenolate (the aqueous reactant). The reactor was agitated mechanically or with the aid of ultrasonic vibration. Performances of the prepared catalysts were compared, and the effect of imposing ultrasound was investigated based on the activity, selectivity, and stability of the catalyst. Experimental results show that tri-n-propylamine is the best active species when CMPS is used as the support, while tri-n-butylamine is the best when SiO₂ and Al₂O₃ are employed as the supports. The CMPS-supported catalyst is far better than the SiO₂- and Al₂O₃-supported catalysts in activity and selectivity but not in stability. Imposing the ultrasound can effectively increase the reaction rate. Mechanical agitation at a low speed with the imposition of ultrasonic vibration not only results in a conversion slightly higher than the case with a high mechanical agitation speed without ultrasonic vibration, but also gives a constant stability for the CMPS-supported catalyst.