Journal of The Chinese Institute of Chemical Engineers最新文献

The present study is aimed at developing an enzymatic/acid-catalyzed hybrid process for biodiesel production using soybean oil as feedstock. In the enzymatic hydrolysis, 88% of the oil taken initially was hydrolyzed by binary immobilized lipase after 5 h under optimal conditions. The hydrolysate was further used in acid-catalyzed esterification for biodiesel production and the effects of temperature, catalyst concentration, feedstock to methanol molar ratio, and reaction time on biodiesel conversion were investigated. By using a feedstock to methanol molar ratio of 1:15 and a sulfuric acid concentration of 2.5%, a biodiesel conversion of 99% was obtained after 12 h of reaction at 50 °C. The biodiesel produced by this process met the American Society for Testing and Materials (ASTM) standard. This hybrid process may open a way for biodiesel production using unrefined and used oil as feedstock.

Crystallization process has been widely used for separation in many chemical industries due to its capability to provide high purity product. To obtain the desired quality of crystal product, an optimal cooling control strategy is studied in the present work. Within the proposed control strategy, a dynamic optimization is first preformed with the objective to obtain the optimal cooling temperature policy of a batch crystallizer, maximizing the total volume of seeded crystals. Two different optimization problems are formulated and solved by using a sequential optimization approach. Owing to the complex and nonlinear behavior of the batch crystallizer, the nonlinear control strategy which is based on a generic model control (GMC) algorithm is implemented to track the resulting optimal temperature profile. The optimization integrated with nonlinear control strategy is demonstrated on a seeded batch crystallizer for the production of potassium sulfate.

Photocatalytic activity of titania with poly(ethylene glycol) (PEG) in the sample films made under different operating conditions was investigated by kinetic analysis of photodegradation tests. The sample films, composed of PEG and nano-TiO₂ particles, were prepared by sol–gel processing and then treated thermally under an atmosphere of wet and dry air at different temperatures. After the thermal treatment, photocatalytic activities of the films were evaluated by a UV-exposure test. Results showed that the photoactivity was enhanced by processing in an atmosphere of wet air at 100 °C. Moreover, the presence of poly(ethylene glycol), and the change in surface morphology in the sample films were verified to be the most influential and significant factors to affect the photoactivitic activity.

This study tended to construct new l-ascorbic acid (LAA) composites in low toxicity and high stability for feasible application. LAA is chemically very unstable, since it is easily oxidized into biologically inactive compounds naturally. Our finding showed that introduction of montmorillonite (MMT) could significantly attenuate its toxicity and to sustain the stability of LAA with economic feasibility for practical uses. In addition, as phosphoric acid was biologically compatible, it was used for the pretreatment of MMT to obtain a promising stabilization of LAA. Toxicity assessment also showed that MMT treated with low-concentration acids should be considered as biologically safe according to our assessment. Thus, using acid treated MMT to stabilize LAA in a long-term might be technically feasible for further uses.

A mathematical model is presented to simulate the performance of a non-isothermal inert membrane reactor with catalytic pellets in the feed-side chamber (IMRCF). The simulation takes into account the various heat exchanges that take place inside the reactor. The model consists of the full set of partial difference equations that describe the conservation of mass, momentum, energy and chemical species, coupled with chemical kinetics and appropriate boundary conditions for the physical problem. The set of equations is solved by finite difference method. The model is applied to investigate the endothermic dehydrogenation of cyclohexane in the IMRCF, where a permselective Vycor glass membrane is used. The simulation results show that the conversion of cyclohexane for non-isothermal IMRCF at the temperature of 550 K and below is higher than the equilibrium conversion. On the contrary, when the temperature is 570 K and above, the conversion will be lower than the equilibrium conversion. The heat effects have a greater influence on the IMRCF.

Production of high-content fructooligosaccharides (FOSs) from sucrose using calcium alginate-immobilized mycelia of Aspergillus japonicus and Aspergillus niger in an internal-loop airlift bioreactor was investigated. The optimal entrapment of mycelia in A. japonicus and A. niger in calcium alginate were 1% and 7% (w/w), respectively. When 60 g of the immobilized mycelia of A. japonicus was supplied into the reactor filling with 3-L 300 g/L sucrose solution and gas velocity 7.32 cm/s, the total FOS production was about 55% (w/w) of total sugars in the mixture after a batch reaction for 9 h. To remove the generated glucose, an inhibitor of β-d-fructofuranosidase, the optimal input of the second immobilized A. niger mycelia particles was 315 g. With this input, the total FOSs mass fraction reached up to 90% (w/w) and the initial rate of transfructosylation was increased almost twice as without supplying glucose oxidase. In addition, 5.49 cm/s was suggested as the operating gas velocity for considering sufficient oxygen supply for glucose oxidase without generating excessive shear stress to damage the immobilized particles.

The enhancement of hybridization efficiency of deoxyribonucleic acid (DNA) targets using oligonucleotide pre-hybridization is studied on two sequence-inversed micro-arrayed probes. The sequences for pre-hybridizing both oligo and target DNA are designed to be fully complementary with their shared DNA probe in a coaxial stacking configuration; i.e. they hybridize immediately alongside each other along the continuous complement probe strand. The pre-hybridizing oligo and target DNA are differentiated by being labeled with two distinct fluorescent dyes, and the cooperative effect on hybridization efficiency is investigated through the comparison of the stacking and individual hybridization configurations based on the detection signals of the labeling dyes. The results show that the pre-hybridization of a DNA oligo enhances the subsequent hybridization efficiency of the target-DNA coupling onto the same probe. The efficiency is enhanced if the hybridization position occurs at a site close to the substrate surface.

Hydrodynamic methods are used for mitigating particle fouling and for enhancing the filtrate flux in submerged membrane filtration. In the comparison membrane blocking-cake formation filtration system, the effects of filtration pressure, aeration intensity, backwash duration and stepwise increasing pressure on the filtration resistances and filtration flux are measured and discussed. Aeration is helpful for reducing particle deposition on the membrane surface, while stepwise increasing pressure can mainly mitigate internal fouling of the membrane. Periodic backwash can significantly reduce both the resistance caused by the membrane internal fouling and by cake formation; consequently, it can effectively recover the filtrate flux. In contrast, increasing the pressure in constant pressure filtration leads the flux to be decreased due to more severe membrane blockage. According to the comparison of the long-term flux and the received filtrate volume, among these hydrodynamic methods, the periodic backwash with longer duration is the optimal strategy for the filtration.

A series of dilute phase pneumatic conveying experiments using two different types of plastic pellets has led to the determination and development of distinguishing flow characteristics. Separate experiments on polystyrene and polyolefin pellets captured pressure-drop fluctuations and values at two different measuring points—one at the lower horizontal section of the transporting pipe and another at the upper section and at two different solid-loading ratios for each material.

Also, comparison and analysis of the pressure-drop fluctuations and values obtained from the experiments were carried out under the same solid-loading ratio and blower rotational speed for both materials. Basic pressure drop calculations were made to find pressure drop due to pure gas, and that due to the presence of solids using a solid friction factor. In addition, the power spectral density analysis, and the wavelet analysis were conducted for both materials to evaluate the flow characteristics.

A user-friendly simulator based on a comprehensive computer model for slurry bubble column reactors (SBCRs) for Fischer–Tropsch (F–T) synthesis, taking into account the hydrodynamics, kinetics, heat transfer, and mass transfer was developed. The hydrodynamic and mass transfer data obtained in our laboratories under typical F–T conditions along with those available in the literature were correlated using Back Propagation Neural Network and empirical correlations with high confidence levels. The data used covered wide ranges of reactor geometry, gas distributor, and operating conditions. All reactor partial differential equations, equation parameters and boundary conditions were simultaneously solved numerically.

The simulator was systematically used to predict the effects of reactor geometry (inside diameter and height) as well as superficial gas velocity and catalyst concentration on the performance of a large-scale SBCR provided with cooling pipes and operating under F–T conditions with cobalt-supported catalyst and H₂/CO = 2. The performance of the SBCR was expressed in terms of CO conversion, liquid hydrocarbon yield, catalyst productivity, and space time yield. The simulator was also used to optimize the reactor geometry and operating conditions in order to produce 10,000 barrels/day (bbl/day) of liquid hydrocarbons.