Iranian Journal of Chemical Engineering (IJChE)

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 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.

Abstract The catalytic reduction of barite in the presence of sodium carbonate has been investigated to evaluate the effect of catalyst amount on reaction mechanism. Different amounts of sodium carbonate ranging from 2.5-10.0 wt.% were doped on coke and the test samples containing stoichiometric mixes of barite and coke powders were isothermally heated in air atmosphere. The catalytic effect of sodium carbonate was studied by isothermal experiments performed at different temperatures and reduction times. The conversion–time data were analyzed by using a modified kinetic model and the influence of catalyst content on kinetic parameters was evaluated. The results show that the addition of 7.5 wt.% sodium carbonate significantly decreases activation energy. Finally, the article concludes that catalyst amount has a negligible role on gasification of coke if the reduction process is carried out at high temperature close to 1100°C. The obtained results can be useful in industrial practice.

Abstract This article describes kinetic modeling of the reduction of barium sulfate by methane based on experimental data obtained by thermogravimetric technique. The conversion- time data have been interpreted by using the grain model for gas-solid reactions and the effect of catalyst on the kinetic parameters has been elucidated. It was found that
zinc oxide acted as a fairly strong catalyst for the reaction, especially at higher temperatures. For example, at about 950°C the reaction rate constant was increased more than 8 times by using only 2 percent of zinc oxide. Orthogonal collocation method was used for solving coupled partial differential equations of gas-solid reaction. There is a good agreement between the experimental data and results obtained from simulation. This research offers a clean method for barium carbonate production with methane as a reducing agent, decreasing CO2 emission significantly. Also, a new process for converting sulfur dioxide to elemental sulfur by a cyclic process involving barium sulfide and barium sulfate has been proposed.

Abstract Copper-manganese oxide catalysts are prepared with an atomic ratio of Cu/Mn=2/1 using a coprecipitation procedure under air atmosphere. The time of aging, i.e., the time that precipitate remains in contact with the precipitating medium, has been varied from 0 (for unaged precursor) to 300 minutes and the effect of precipitate aging time in each atmosphere upon the structure and morphology of different catalysts and their precursors is investigated. The precursors and catalysts were characterized by powder X-ray diffraction (XRD), temperature programmed reduction (TPR) and transmission electron microscopy (TEM). X-ray diffraction and electron microscopy showed that aging of the initial precursor altered the structure of the precursor. The TPR reduction profiles of the copper — manganese mixed oxide catalysts showed a dramatic change of shape on aging. In all catalysts, CuO was completely reduced to metal while the MnO did not reduce under the experimental conditions.