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

► Application of surface-modified AB5 for H2 separation. ► Upscale of the surface modification procedure (up to 1.5kg of AB5 substrate). ► Integration of the surface-modified AB5-type materials in H2 separation systems. ► Stable performances throughout 250 absorption/desorption cycles. ► The total process productivity is limited by slow selective H2 absorption. Application of surface-modified MH material for H2 separation using temperature/pressure swing absorption–desorption was studied. The substrate alloy had the following composition LaNi3.55Co0.75Al0.4Mn0.3, 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 (∼1.5kg) batches. Feasibility of its application for H2 separation from gas mixtures (up to 30% CO2 and 100ppm CO) was demonstrated by testing of a prototype H2 separation system (∼280g of MH in two reactors), and H2 separation reactor (0.75kg 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 ⩽2.5bar, 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 5000h−1.