Effects of Catalysts and Membranes on the Performance of Membrane Reactors in Steam Reforming of Ethanol at Moderate Temperature

Steam reforming of ethanol in the membrane reactor using the Pd77Ag23 membrane was evaluated in Ni/CeO2 and Co/CeO2 at atmospheric pressure. At 673 K, the H2 yield in the Pd77Ag23 membrane reactor over Co/CeO2 was found to be higher than that over Ni/CeO2, although the H2 yield over Ni/CeO2 exceeded that over Co/CeO2 at 773 K. This difference was owing to their reaction mechanism. At 773 K, the effect of H2 removal could be understood as the equilibrium shift. In contrast, the H2 removal kinetically inhibited the reverse methane steam reforming at low temperature. Thus, the low methane-forming reaction rate of Co/CeO2 was favorable at 673 K. The addition of a trace amount of Ru increased the H2 yield effectively in the membrane reactor, indicating that a reverse H2 spill over mechanism of Ru would enhance the kinetical effect of H2 separation. Finally, the effect of membrane performance on the reactor performance by using amorphous alloy membranes with different compositions was evaluated. The H2 yield was set in the order of H2 permeation flux regardless of the membrane composition

Effect of arginine-based deep eutectic solvents on supported porous sorbent for CO2 capture analysis

Carbon dioxide (CO2) as one of the heat-trapping gases, has caused global warming. Being a greener and more economical material, amino acid-based deep eutectic solvents (AADES) have attracted interest in CO2 capture applications. In this paper, the effect of L-arginine (Arg) in binary AADES of arginine-ethylene glycol (Arg-EG) and ternary AADES of choline chloride-ethylene glycol-arginine (ChCl-EG-Arg) on adsorption of CO2 was studied. The solubility, basicity, and physicochemical characteristics were compared with the binary DES (ChCl-EG) before and after being impregnated into a silica gel (SG) via the wet impregnation method. The AADES/SG adsorbents were evaluated for CO2 sorption performance using an automated gas sorption analyzer at 100% CO2 loading and thermogravimetric analysis (TGA) at flue gas conditions (15% CO2/85% N2). Findings show the basicity and the nitrogen content (N%) of AADES/SG were increased as Arg was added and DES/AADES functional group peaks (amino, hydroxyl, alkyl groups) were observed after the impregnation. The CO2 sorption of 16.0 mg/g at 25 °C and 1 atm was achieved by 30% Arg-EG(1:8)/SG followed by 30% ChCl-EG-Arg (1:2:0.1)/SG (14.8 mg/g) and 30% ChCl-EG/SG(1:2) (14.5 mg/g) using an Autosorb iQ2 instruments with 100% CO2 loading. The CO2 uptake was increased almost linearly with increasing pressure and decreased with increasing temperature. The Arg-EG(1:8)/SG shows the highest selectivity toward CO2 than other sorbents with 8.10 mg/g adsorption for 1 h at 15% CO2 loading at 25 °C with higher thermal stability and surface area. Considering environmental, technological, and economic viewpoints, the Arg-EG(1:8)/SG can be explored more as a potential solid sorbent for CO2 capture

Effect of Co-existing gases on hydrogen permeation through a Pd82–Ag18/α-Al2O3 membrane during transient start-up

The work aimed to study the influence of co-existing gaseous mixture (H2–N2–CO–CO2) on hydrogen permeation through the counter-current flow of a Pd82–Ag18/α-Al2O3 membrane during transient start-up at 350 °C and atmospheric pressure. The membrane was operated for an 8-h. Its performance was measured in terms of hydrogen flux and recovery. The results were mapped on Sieverts-Fick's line and showed a slight membrane deactivation because of the presence of N2 and CO2 in the feed gas. The membrane deactivation became more profound when CO was a constituent. The effect of the co-existing gases on the hydrogen flux, in increasing order, was CO > CO2>N2. The co-existing gases, if present as a significant fraction, induces dilution, concentration polarization, and inhibition over the membrane surface, decreases the membrane performance in term of hydrogen recovery, time lag during transient start-up, and deactivation. It is recommended that the start-up might be run using equimolar H2–N2 mixture

Promoting dry reforming of methaneviabifunctional NiO/dolomite catalysts for production of hydrogen-rich syngas

Extensive effort has been focused on the advancement of an efficient catalyst for CO2 reforming of CH4 to achieve optimum catalytic activity together with cost-effectiveness and high resistance to catalyst deactivation. In this study, for the first time, a new catalytic support/catalyst system of bifunctional NiO/dolomite has been synthesized by a wet impregnation method using low-cost materials, and it shows unique performance in terms of amphoteric sites and self-reduction properties. The catalysts were loaded into a continuous micro-reactor equipped with an online GC-TCD system. The reaction was carried out with a gas mixture consisting of CH4 and CO2 in the ratio of 1 : 1 flowing 30 ml min-1 at 800 °C for 10 h. The physicochemical properties of the synthesized catalysts were determined by various methods including X-ray diffraction (XRD), N2 adsorption–desorption, H2 temperature-programmed reduction (H2-TPR), temperature-programmed desorption of CO2 (TPD-CO2), and temperature-programmed desorption of NH3 (TPD-NH3). The highest catalytic performance of the DRM reaction was shown by the 10% NiO/dolomite catalyst (CH4 & CO2 conversion, χCH4; χCO2 ~ 98% and H2 selectivity, SH2 ¼ 75%; H2/CO ~ 1 : 1 respectively). Bifunctional properties of amphoteric sites on the catalyst and self-reduction behaviour of the NiO/dolomite catalyst improved dry reforming of the CH4 process by enhancing CH4 and CO2 conversion without involving a catalyst reduction step, and the catalyst was constantly active for more than 10 h