In this study, the Taguchi experimental design method using an L16 orthogonal array was attempted in order to investigate the optimal operating conditions for the CO₂ methanation process in Ni-based catalysts. The relative influence of the main factors affecting CO₂ conversion and CH₄ yield was ranked as follows: reactor pressure > space velocity > reaction temperature. The optimal combination of operating conditions was a reactor temperature of 315 °C, a pressure of 19 bar, and a space velocity of 6000 h⁻¹. The effect of the H₂/CO₂ ratio on CO₂ conversion and CH₄ yield was further considered under these optimal operating conditions. Moreover, the catalyst was characterized in order to investigate the production of coke through Brunauer–Emmett–Teller analysis, thermogravimetric analysis, and scanning electron microscopy. The amount of coke produced after the reaction for approximately 24 h was ~2 wt.%. Therefore, the desired CH₄ yield and long-term operational stability were successfully obtained using the Taguchi design method and catalyst characterization.

Bifunctional Al₂O₃/Cu/ZnO catalysts with Al composition of between 30 mol% and 80 mol% were prepared by sequential precipitation (SP) for the conversion of CO₂ into dimethyl ether (DME). In the SP synthesis, the concentration of a precipitation agent managed to be high enough to induce the complete precipitation of Al³⁺. The prepared precipitates were composed of zincian malachite and amorphous AlO(OH). Furthermore, the calcined mixed metal oxide materials of 60% and 80% Al exhibited a higher acidity than commercial Al₂O₃ and the H₂-reduced catalysts showed the similar Cu dispersion of 6%–7% at all Cu loadings. In the activity test at 573 K and 50 bar, the SP-derived catalyst of 80% Al (SP-80) displayed the best performance corresponding to CO₂ conversion of 25% and DME selectivity of 75% that are close to equilibrium values. In order to overcome the thermodynamic limitation, a dual-bed catalyst system was made up of SP-80 in the first layer and zeolite ferrierite in the next. This approach enabled DME selectivity to be enhanced to 90% while CO₂ conversion increased a little. Consequently, the studied catalyst system based on the SP-derived catalysts can contribute greatly to selective DME production from CO₂.

We have developed a facile and sustainable method to produce a novel θ-Al₂O₃-supported CuCl adsorbent through impregnation methods using CuCl₂ as the precursor. In an easy two-step process, θ-Al₂O₃ was impregnated with a known concentration of CuCl₂ solutions, and the precursor was calcined to prepare CuCl oversupport. The developed novel θ-Al₂O₃-supported CuCl adsorbent was compared with an adsorbent prepared through the conventional method using CuCl salt. The adsorbents were characterized via X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and temperature-programmed reduction (H₂-TPR). Overall, the adsorbent indicates a high CO adsorption capacity, high CO/CO₂ and CO/N₂ selectivity, and remarkable reusability performance. This process is operated at ambient temperature, which minimizes operation costs in CO separation processes. In addition, these results indicate that the systematic evaluation of alumina-supported CuCl adsorbent can provide significant insight for designing a realistic PSA process for selective CO separation processes.

In this study, hydrogen was recovered and purified by using a membrane contactor unit from CO₂-rich gas without the use of any basic chemicals such as amines. The membrane operational parameters were adjusted to achieve high CO₂ removal and H₂ recovery. The effects of gas flow rate, pressure, gas composition (CO₂/H₂ ratio), pressure difference between liquid and gas, and gas/liquid ratio on CO₂ removal and H₂ recovery were investigated. Depending on the gas flow rate, the contact time between gas and liquid could be controlled, changing the absorption amounts of CO₂ and H₂. Regarding gas composition, an increase in the CO₂/H₂ ratio from 0.25 to 1 boosted H₂ recovery. Furthermore, increasing the CO₂/H₂ ratio above 1 (from 1 to 3) generally reduced H₂ recovery from 98.7% to 83%. Additionally, supplementation with the optimal amount of additive enhanced CO₂ removal and H₂ recovery. Thus, using a membrane contactor system results in high CO₂ removal (82.7–93.5%) and H₂ recovery (91.5–98.7%). Moreover, H₂ production and separation can be performed in one system, implying that CO₂ removal can be performed more efficiently by the membrane contactor. This study offers a new and promising route for producing high-purity H₂ while removing CO₂.

This research investigates the simultaneous reduction of nitric oxide (NOx) and toluene using Pt-based catalysts, aiming at applications in small-scale industrial environmental processes. Catalysts with varying Pt loadings from 0.01 to 3 % were synthesized through wet impregnation, and their dispersion was assessed across several characterizations, revealing effective Pt dispersion even at loadings above 1 %. Under conditions of high toluene feed, the 3 % Pt-loaded catalyst emerged as the most efficient, achieving significant NOx and toluene conversion rates. The performance of this catalyst was thoroughly examined under various operational parameters including NO, toluene, O₂ concentrations, gas hourly space velocity (GHSV) and reaction temperature. A short-stress test further underscored its effectiveness, with NOx and toluene conversions reaching 89.7 % and 97.6 %, respectively. Additionally, a preliminary process simulation of the NOx reduction by toluene indicated an energy efficiency improvement of over 8 % compared to conventional RCO and de-NOx processes. The findings suggest the catalyst's potential for NOx reduction in industrial settings, utilizing toluene present in flue gas without the need for additional commercial reducing agents.