Iranian Journal of Chemical Engineering (IJChE)

Abstract Optimization of the homogeneous rhodium-catalyzed methanol carbonylation reactor to reduce CO2 emissions is studied in this line of research. In this paper, the steady-state homogeneous rhodium-catalyzed methanol carbonylation reactor is simulated using Aspen HysysV.9 software, by comparing the simulation results with industrial information, a mean relative error (excluding methanol) of 4.8% was obtained, which indicates the high accuracy of the simulation. The central composite design (CCD) and genetic algorithm (GA) with the aid of a simplified process simulation were used to estimate the effect of individual variables (liquid level, the temperature of the catalyst-rich recycle stream, the mole ratio of CO to methanol (MeOH) in the feed, and flow rate of dilute acid stream) and their mutual interactions to reduce CO2 emissions. It is obtained that the liquid level percentage of 46%, the catalyst-rich recycle stream temperature of 120 °C, CO: MeOH molar ratio equal to 1.13:1, and the dilute acid flow rate of 513.14 kmol/hr lead to CO2 reduction by 34%.

Abstract The optimization of the ammonia synthesis plant to increase the production of ammonia is studied in this line of research. In this paper, the steady-state ammonia synthesis is simulated using the Aspen HysysV.11 software. By comparing the simulation results with the industrial information, a mean relative error of 7.71 % was obtained, which indicated the high accuracy of the simulation. Then, four effective variables were selected from among 11 independent variables by the Plackett-Burman method. The effects of the Hydrogen flow in the feed stream, Recycle stream pressure, Feed stream temperature, and input temperature of the third reactor were investigated, and the response surface design method of the central composite design was performed to plant optimize. It is obtained that the Hydrogen flow in the feed stream is equal to 6255 , the feed stream pressure is equal to 205 bar, the temperature of the excess stream inlet in the first reactor is equal to 663 K, and the temperature of the stream inlet of the second reactor is 677.5 K which increased the ammonia production by 7.5 %.

Abstract Magnetic silica aerogel in hydrophobic and hydrophilic forms were used as support to immobilize Candida rugosa lipase by adsorption method. Response surface methodology (RSM) was employed to study the effects of the three most important immobilization parameters, namely enzyme/support ratio (0.3-0.5, w/w), immobilization time (60-120 min) and alcohol percentage (20-40, %v/v) on the specific activity of immobilized lipase on the hydrophobic supports. For hydrophilic supports, alcohol percentage was removed as there was no need for pre-wetting step in enzyme immobilization process. Second order regression models with high coefficient determination (R2) values of higher than 0.98 were fitted to predict the response as function of immobilization parameters. The results indicated that for hydrophobic supports, optimum values for enzyme/support ratio, immobilization time and alcohol percentage were obtained at 0.45 (w/w), 94.27 min and 38.81 %, respectively, in which specific activity were predicted at 15.32 U/mg-protein. For hydrophilic supports, the optimum enzyme/support ratio and immobilization time were predicted at 0.47 (w/w) and 83.47 min, respectively. Specific activity in these conditions were obtained 11.21 U/mg-protein. As the difference between the experimental and predicted values was showed as non-significant, the response surface models employed could be considered as adequate.

Abstract The aim of the present work was to evaluate the effect of soy protein isolate (SPI)-gum arabic (GA) composite on the stability of beverage emulsion prepared as the orange oil-in-water (O/W) emulsion. Response surface methology (RSM) was used to study the influence of the two independent variables, each at three levels (homogenization speed
as x1 (1500, 15700, and 30000 rpm) and GA:SPI ratio as x2 (1, 0.6, and 0.2) on the two dependent variables namely, size of the emulsion droplet (EPS) as y 1 and emulsifying activity (EA) as y 2 . The results were discussed on the two empirical models obtained. Analysis of variance (ANOVA) showed a high coefficient of determination (R2 ) value of 0.937 and 0.979 for EPS and EA, respectively, ensuring a satisfactory adjustment of the second-order regression model with the experimental data. The negative sign for the regression coefficient of x1, indicated that size of the emulsion droplet increased with the decreased level of factor x1 from 30000 to 1500 rpm, while EA increased with increased levels of factor x1 . Thus, GA: SPI ratio with the lowest amount of GA along with the homogenization speed at high level, gave the smallest size of emulsion droplet (1μm). This size corresponded to the high emulsifying activity and stability. Sodium chloride and freeze-thaw cycling are two environmental factors affecting emulsion stability. Results of freeze-thaw cycling test showed a large decrease in the EA of the sample prepared with a low level of SPI:GA ratio and no dependence of the EA on the NaCl concentrations in the range of the tested levels was observed (50-150 mM). Long-term storage stability test (storing the emulsion samples at 4, 16, and 30ºC each for 8 days) showed the size of the emulsion droplet increased with the storage time. Results of use of SPI as a readily available plant source of protein for preparation of the encapsulant for orange oil-emulsion were encouraging, especially when one considers the dependence of the beverage industry on the unreliable source of supply of GA. RSM was successfully applied for the modeling of the emulsion preparation.