Poisoning-tolerant metal hydride materials and their application for hydrogen separation from CO2/CO containing gas mixtures

Metal hydride materials offer attractive solutions in addressing problems associated with hydrogen separation and purification from waste flue gases. However, a challenging problem is the deterioration of hydrogen charging performances resulting from the surface chemical action of electrophilic gases. In this work, the feasibility study of poisoning tolerance of surface modified AB5-type hydride forming materials and their application for hydrogen separation from process gases containing carbon dioxide and monoxide was carried out. Target composition of La(Ni,Co,Mn,Al)5 substrate was chosen to provide maximum reversible hydrogen capacity at the process conditions. The selected substrate alloy has been shown to be effectively surface-modified by fluorination followed by electroless deposition of palladium. The surface-modified material exhibited good coating quality, high cycle stability and minimal deterioration of kinetics of selective hydrogen absorption at room temperature, from gas mixtures containing 10% CO2 and up to 100 ppm CO. The experimental prototype of a hydrogen separation unit, based on the surface-modified metal hydride material, was tested and exhibited stable hydrogen separation and purification performances when exposed to feedstocks containing concentrations of CO2Web of Scienc

Application of surface-modified metal hydrides for hydrogen separation from gas mixtures containing carbon dioxide and monoxide

Application of surface-modified MH material for H2 separation using temperature/pressure swing absorption–desorption was studied. The substrate alloy had the following composition LaNi3.55Co0.75Al0.4-Mn0.3, and the surface modification was carried out through fluorination followed by aminosilane functionalization and electroless deposition of Pd. The material was found to have good poisoning tolerance towards surface adsorbates, even for the large (rv1.5 kg) batches. Feasibility of its application for H2 separation from gas mixtures (up to 30% CO2 and 100 ppm CO) was demonstrated by testing of a prototype H2 separation system (rv280 g of MH in two reactors), and H2 separation reactor (0.75 kg of MH). The H2 separation was characterized by stable performances in the duration of 250 absorption/desorption cycles. However, the total process productivity was found to be limited by the sluggish H2 absorption (partial H2 pressure 62.5 bar, temperature below 100 °C). In the presence of CO2 and CO, additional deceleration of H2 absorption was observed at space velocities of the feed gas below 5000 hWeb of Scienc

Green synthesis of polypyrrole/nanoscale zero valent iron nanocomposite and use as an adsorbent for hexavalent chromium from aqueous solution

Green synthesis of polypyrrole/nanoscale zero valent iron nanocomposite (Ppy/Fe0 NC) fabricated by a simple in-situ oxidative polymerization method was reported. The structure and the properties of Ppy/Fe0 NC were confirmed using various analytical techniques. The as-prepared Ppy/Fe0 NC was used as an adsorbent for the adsorption of hexavalent chromium (Cr(VI)) through batch experiments. The effect of initial pH, adsorbent dose, contact time, equilibrium concentration and co-existing ions were studied. It was deduced that adsorption data followed the pseudo-second-order rate model and Langmuir isotherm model with a maximum adsorption capacity of 202.02 mg/g at 25°C. Furthermore, high selectivity of Ppy/Fe0 nanocomposite for the removal Cr(VI) was observed even in the presence of co-existing ions. These findings suggest that the green synthesized adsorbent can be used for treatment of wastewater containing Cr(VI)