Journal of The Chinese Institute of Chemical Engineers最新文献

Single- and double-stage catalytic preferential CO oxidation (CO-PrOx) over-Fe₂O₃-promoted CuO–CeO₂ in a H₂-rich stream has been investigated in this work. The catalyst was prepared by the urea-nitrate combustion method and was characterized by X-ray diffractometer (XRD), X-ray fluorescence (XRF), Brunauer–Emmet–Teller (BET), transmission electron microscope (TEM), and scanning electron microscope (SEM). The catalytic activity tests were carried out in the temperature range of 50–225 °C under atmospheric pressure. The results of the single-stage reaction indicated that complete CO oxidation was obtained when operating at a O₂/CO ratio of 1.5, W/F ratio of 0.36 g s/cm³, and at a reaction temperature of 175 °C. At these conditions, H₂ consumption in the oxidation was estimated at 58.4%. Applying the same conditions to the double-stage reaction, complete CO oxidation was found and H₂ consumption in the oxidation was reduced about 4.9%. When decreasing the double-stage reaction temperature to 150 °C, the results elucidated that CO could be converted to CO₂ completely while H₂ consumption in the oxidation was further reduced to 33.5%. A temperature blocking 2² factorial design has been used to describe the importance of the factors influencing the catalytic activity. The factorial design was according to the experimental results. When adding CO₂ and H₂O in feed, reduction of CO conversion for single- and double-stage reaction is obtained due to a blocking of CO₂ and H₂O at a catalytic active site. Comparing CO conversion obtained when operating with/without CO₂ and H₂O in feed for single- and double-stage reaction, less reduction is achieved when operating in double-stage reaction.

In this study, the behavior of gas dispersion in a bubbling fluidized bed was investigated. Carbon dioxide was used as the tracer gas. Most of the gas jets from tuyeres are towards the same direction, parallel with the longitudinal axis. The movement of particles in the lateral direction was enhanced by the momentum of horizontal gas jets within the bed.

The experimental results show that the effect of superficial gas velocity on the gas mixing depends on the distributor type. Comparing with perforated distributor, a better performance of gas mixing was observed while the bed was equipped with horizontal nozzle distributor.

The concept of carbon credit arose out of increasing awareness of the need to reduce emissions of greenhouse gases to combat global warming which was formalized in the Kyoto Protocol. In addition to contribution to sustainable development with energy recovery in the form of methane, carbon credits can be claimed by application of advanced anaerobic processes in wastewater treatment for reducing emissions of greenhouse gases. As anaerobic granular systems are capable of handling high organic loadings concomitant with high strength wastewater and short hydraulic retention time, they could render much more carbon credits than other conventional anaerobic systems. Granular anaerobic processes have become an attractive choice of treatment technology especially for high strength wastewaters, considering the fact that in addition to efficient waste degradation, the carbon credits can be used to generate revenue and to finance the project. This paper presents a scenario on emission reduction based on a methane recovery and utilisation project. An example analysis on emission reduction and the future trend is also outlined.

In this work we develop a simple method to synthesize nanosized Ag colloids with the addition of urea which produce intermediates AgOCN and Ag₂CO₃ before the formation of silver. These intermediates are beneficial to obtaining high conversions of narrow size distributions of silver colloids from this synthesis process. At the molar ratio of [Urea]/[Ag⁺] = 4, [NaOH]/[Ag⁺] = 0.8, the weight ratio of PVP/AgNO₃ = 1 g/g, using dextrose as a reducing agent and a reaction temperature of 70 °C, we obtain silver colloids of average size 22 nm with a standard deviation of 4.7 nm after separation and washing procedures. The conversion under these conditions was nearly complete at about 98%. After a thorough washing procedure, the purity of silver colloids is up to 94.4% and its dried film is electrically conductive at room temperature. The electrical resistivity reached 4.5 × 10⁻⁶ Ω cm after 250 °C heating for 30 min.

The rate equations and isotherms for two adsorption models have been formulated and discussed. The rate equations obtained have been compared to those of pseudo-first-order model and pseudo-second-order model, respectively. Calculated results indicated that the rate equations of single site model and dual site model could be approximated by those of pseudo-first-order model and pseudo-second-order model, respectively, in a limited ranges of the values of $C_{\text{A}\cdot \text{Se}}^{\ast }$ $\left(\text{or}{C}_{\text{A}\cdot {\text{S}}_2\text{e}}^{\ast }\right)$, K*and t*. The adsorption isotherm of single site model has been found to be the same as that of Langmuir type.

Gamma aminobutyric acid type A (GABA-A) receptors are an important therapeutic target in insomnia treatment. The GABA-A protein structure is still not available. In this study, a reliable structure of GABA-A receptor was built and validated by several criteria. Zolpidem was predicted to gain the highest binding affinity at the BZ-binding site and be surrounded by α₁-His129, α₁-Tyr187, α₁-Gly228, α₁-Thr234, α₁-Tyr237, γ₂-Met96, γ₂-Phe116, and γ₂-Met169. In addition, GABA formed five hydrogen bonds with α₁-Arg159, β₂-Glu179, and β₂-Tyr181 and was surrounded by the residues α₁-Phe92, α₁-Arg147, β₂-Tyr181, β₂-Thr184, β₂-Thr226, and β₂-Tyr229 at the GABA-binding site. The two simulation results were consistent with the experimental assay, which suggested that the simulated GABA-A receptor was reliable. Jujuboside A, which was considered the effective suanzaoren constituent, had difficulty penetrating the blood–brain barrier. Besides, jujuboside A was unable to bind at both binding sites due to its large structural volume. However, jujubogenin that was hydrolyzed from jujuboside A showed the most compatible binding pose and formed five hydrogen bonds with the key residues, β₂-Thr226 and β₂-Tyr229, at the GABA-binding site. In addition, according to a docking study, jujubogenin gained higher scoring values, which indicated a higher binding affinity. Moreover, the adsorption, distribution, metabolism, excretion, and toxicity (ADMET) descriptors predicted that jujubogenin had high blood–brain barrier penetration. Conclusively, jujubogenin was suggested to be the effective suanzaoren constituent for exerting the sedative function via GABA-A receptor.

Aerobic granulation (AG) and membrane bioreactor (MBR) are two promising, novel environmental biotechnological processes that draw interest of researchers engaging work in the area of biological wastewater treatment. Membrane fouling in the combined, AGMBR process was investigated in this work. The fouling layer formed on hollow-fibre membranes in both reactors were for the first time directly observed with the multiple staining and confocal laser scanning microscope (CLSM) technique. Fouling layers in both reactors presented a rather heterogeneous fouling layer, with that on SMBR much more redundant than that on AGMBR. The EPS in the AGMBR fouling layer was principally consisted of proteins, α-polysaccharides, and lipids, with few β-polysaccharides or cells. In SMBR, large quantity of DNA was probed in the fouling layer. Over-deposition of fouling layer on hollow-fibre membrane may assist preventing occurrence of irreversible fouling, which is beneficial to long-term operation of the AGMBR.

A well-designed CFBC can burn coal with high efficiency and within acceptable levels of gaseous emissions. In this theoretical study effects of operational parameters on combustion efficiency and the pollutants emitted have been estimated using a developed dynamic 2D (two-dimensional) model for CFBCs. Model simulations have been carried out to examine the effect of different operational parameters such as excess air and gas inlet pressure and coal particle size on bed temperature, the overall CO, NO_x and SO₂ emissions and combustion efficiency from a small-scale CFBC. It has been observed that increasing excess air ratio causes fluidized bed temperature decrease and CO emission increase. Coal particle size has more significant effect on CO emissions than the gas inlet pressure at the entrance to fluidized bed. Increasing excess air ratio leads to decreasing SO₂ and NO_x emissions. The gas inlet pressure at the entrance to fluidized bed has a more significant effect on NO_x emission than the coal particle size. Increasing excess air causes decreasing combustion efficiency. The gas inlet pressure has more pronounced effect on combustion efficiency than the coal particle size, particularly at higher excess air ratios. The developed model is also validated in terms of combustion efficiency with experimental literature data obtained from 300 kW laboratory scale test unit. The present theoretical study also confirms that CFB combustion allows clean and efficient combustion of coal.