Iranian Journal of Chemical Engineering (IJChE)

Abstract The research on the Research Octane Number (RON) of the Light Naphtha Isomerization (LNI) process has significant implications for the quality of gasoline and RON, which are crucial issues in the refinery. In this study, the isomerization unit in an existing 420,000-barrel-per-day gas condensate refinery was investigated to increase RON and decrease total costs. The research involved selecting equipment (means column) to replace the existing ones in an isomerization unit to improve RON and decrease total costs for specific feedstocks. The Deisopentanizer-Deisohexanizer DIP-DIH isomerization unit was chosen as the base case. Three scenarios were simulated and studied to predict product specifications: Deisopentanizer-Depentanizer DIP-DP, Deisopentanizer-Dehexanizer DIP-DH, and Deisopentanizer-Depentanizer-Deisohexanizer DIP-DP-DH isomerization units. To increase RON and study energy consumption, we designed and simulated these scenarios using Aspen HYSYS V9. The energy consumption of the Heat Exchanger Network (HEN) was analyzed using the Aspen Energy Analyzer. The results show that by replacing the equipment and adding new ones, the RON and total cost were significantly altered. The DIP-DP isomerization unit exhibited a higher multiply flow rate by RON, compared to the base case (DIP-DIH) and other scenarios. The results indicate that the DIP-DP isomerization unit improves RON by 6.6% and the total cost by 7.9%.

Abstract Most of the reactions that occur in microreactors take place on the surface, so it is important to keep the reactants close to the reactive wall. One effective technique in this field is the single-phase hydrodynamic focusing. However, this method has a drawback: a high percentage of reactants penetrate into the sheath fluid. To address this issue, the concept of the two-phase hydrodynamic focusing is introduced in this study. The main idea is to use a highly viscous sheath fluid to create a barrier against reactant penetration into the sheath flow. To demonstrate the effectiveness of this method, a 3D numerical simulation was performed with an irreversible second-order reaction. The results show that the two-phase hydrodynamic focusing increases reaction rates, particularly in downstream regions where the Sherwood number can increase by several orders of magnitude with the use of a highly viscous sheath of liquids. Additionally, it was observed that the use of the two-phase hydrodynamic focusing improves the efficiency, which is defined as the ratio of the solute in the sample flow to the total solute in each cross-section..

Abstract In the present work, the effect of synthesis method (simultaneous impregnation and coprecipitation) and copper to nickel active phases loading were investigated in Ni-Cu-Al catalysts. The water/ethanol molar ratio of 6 and gas hourly space velocity (GHSV) of 20000 hr^-1 were used in all the experiments. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. The catalytic activity results revealed that 13Ni-6Cu/γ-Al₂O₃ impregnated catalyst was more active than co-precipitated one (13NiO-6CuO-81Al₂O₃) in the same amount of compositions of active metals and Al₂O₃, but by increasing the active phases (Cu and Ni) loading in co-precipitated catalysts (24NiO-31CuO-45Al₂O₃, 31NiO-24CuO-45Al₂O₃, 40NiO-15CuO-45 Al₂O₃ and 47NiO-8CuO-45Al₂O₃), they achieved a better performance than 13NiO-6CuO-81Al₂O₃ catalyst. The 40NiO-15CuO-45Al₂O₃ catalyst showed 99% ethanol conversion, as well as 303 hydrogen yield and 4% CO selectivity at 470^oC. SEM images revealed agglomerated particles for the samples with high Al₂O₃ content and with increasing the active phase content in the catalyst the particle sizes decreased. The 40NiO-15CuO-45Al₂O₃ showed smallest particle size among the catalysts.

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 One of the effective catalysts for hydrogen purification and production via medium temperature shift reaction, is Cu-Ce solid solution. Cu0.1Ce0,9O1.9 was produced using co-precipitation method and then was utilized as support for 5Cu/Ce0.9Cu0.1O1.9 catalyst which was synthesized employing wet impregnation method. X-ray diffraction (XRD) analysis showed that crystalline sizes of Ce0.9Cu0.1O1.9 and 5Cu/Cu0.1Ce0,9O1.9 were 9.22 and 18.33 nm, respectively. The Catalysts were evaluated in medium temperature shift reaction at 300-390 °C and at gas hourly space velocities (GHSV) of 12000 and 30000 h-1, in a fixed bed reactor. Due to higher concentration of Cu and synergic positive effects of both active metal and support, 5Cu/Cu0.1Ce0,9O1.9 catalyst showed better performance. It was also concluded that, because of low residence time at high levels of GHSV, increasing GHSV leads to decrease CO conversion. Then 5Cu/Cu0.1Ce0,9O1.9 was evaluated in microchennel reactor in 2 GHSVs of 12000 and 30000 h-1 and results were compared with the fixed-bed reactor. It can be concluded that microchannel reactor is better in higher GHSVs (lower residence time of gas flow). A microchannel reactor provides a high surface-to-volume ratio and gases pass over the thin layer of catalyst on the coated plates. Hence, due to the better access to the catalytic bed, the reactants react even in a short time, which improves the microchannel performance compared to the fixed bed reactor

Abstract Micro-reformers used for producing hydrogen with a high surface-to-volume ratio in small-scale fuel cells were investigated. To this end, scrutinizing and exploiting all areas of micro reformers is very important. Parallel micro-channels have shown good performance in eliminating dead volumes. Inlet/outlet configuration has great effect on the velocity distribution through micro-channels. In this study, four configurations (1 inlet/1 outlet on the same and opposite sides; 1 inlet/2 outlets on the same and opposite sides) were studied through simulation and 1 inlet/2 outlets on opposite sides were found to have the lowest velocity difference, hence having the best configuration. Simulations were carried out at 600 °C, 1 atm, with S/C=3 and feed flow rate of 100 mL/min. Three channel patterns (i.e., parallel, splitting-jointing and pin-hole) were compared in terms of Figure of Merit (FoM) and specific conversion. Parallel channel design revealed a high value of specific conversion to be about 5.36   , while splitting-jointing and pin-hole were 5.33  and 4.91 , respectively. Based on FoM, pin-hole design had a high value of 1.34   , while the values of splitting-jointing and parallel designs were 0.037  and 1.28 , respectively.

Abstract In this research effect of synthesis method of magnesium aluminate as support of Ni catalysts at the reverse water gas shift (RWGS) reaction was evaluated. The RWGS reaction is applied in Carbon Dioxide Hydrogenation to Form Methanol via a Reverse Water-Gas Shift Reaction (CAMERE) process for the transformation of CO2 into methanol. The MgAl2O4 supports were prepared by sol-gel (M1), surfactant-assisted co-precipitation (M2) and ultrasonic-assisted co-precipitation (M3) techniques. 1.5wt.% Ni/M1 showed highest CO2 conversion (42.1%) and lowest CO selectivity, while 1.5wt.% Ni/M2 showed the lowest CO2 conversion and the highest CO selectivity (>92.5 %). The 1.5wt.% Ni/M3 showed similar catalytic activity as 1.5 wt.%Ni/M2, but with lower CO selectivity. The high CO selectivity of 1.5 wt.% Ni/M2 with a BET surface area of 121.7 m2g-1 was accredited to a higher dispersion of Ni particles resulted by higher total pore volume of this catalyst. High specific surface area along with large total pore volume, is effective in increasing the nickel dispersity. The following pore size distribution and total pore volume order was obtained for catalysts: 1.5wt.% Ni/M2> 1.5wt.% Ni/M3> 1.5wt.% Ni/M1. Among the prepared supports, M1 with BET of 174.5 m2.g-1 showed the highest specific surface area. All prepared supports and catalysts possessed mesoporous structure. Well dispersed NiO species with high interaction with the support were detected by TPR analysis. The SEM images detected particles with less than 80 nm for M2 and 1.5wt.%Ni/M2 samples. The long term stability test performed on 1.5wt.%Ni/M2 showed great catalytic activity after 15h on stream.

Abstract Methanol steam reforming plays a pivotal role to produce hydrogen for fuel cell systems in a low temperature range. To accomplish higher methanol conversion and lower CO production, the reaction was catalyzed by CuZnFe mixed oxides. Various ratios of Fe and Cu/Zn were coprecipitated in differential method to optimize the CuZnFe structure. The sample containing 45Cu50Zn5Fe (Wt. %) revealed its maximum methanol conversion of 98.4 % and CO selectivity of 0.78 % with operating conditions of gas hourly space velocity of 18000 h-1 and steam to carbon ratio of 1.3 at 270 °C. The synthesized catalysts were analyzed by powder X-ray diffraction, N2 adsorption/desorption, temperature programmed reduction, scanning electron microscopy techniques. The results revealed that the prepared samples presented mesoporous structure with different pore size depending on the Cu/Zn/Fe ratios. The results showed that increase in Fe loading to 20 Wt. % empowered methanol conversion and decreased CO selectivity. Moreover, the optimized catalyst activity was kept constant during 17 h time on stream. Besides, operating conditions of gas hourly space velocity and steam to carbon ratios were evaluated.