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

Abstract

Lototskyy, M. et al. (2013). Application of surface-modified metal hydrides for hydrogen separation from gas mixtures containing carbon dioxide and monoxide. AbstractApplication 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 h 1. Introduction Selectivity of reversible hydrogen interaction with hydride-forming materials allows for the development of simple and efficient pressure/temperature swing absorptiondesorption systems for hydrogen separation from complex gas mixtures and its fine purification [1,2]. However, so far, this approach was successfully implemented only for hydrogen-rich feed gases (vent streams in the ammonia synthesis loop, H 2 > 50%) which contain relatively innocuous admixtures, mainly nitrogen and argon [3,4]. At the same time, the gases associated with processing of coal, petrol, natural gas and other carbonaceous/fossil fuels feedstock, in addition to hydrogen, may contain significant amounts of other components, mainly carbon dioxide and monoxide, which in most cases cause the deterioration of hydrogen sorption performances of metal hydrides (MHs) [5,6].

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

“…6(b)) results in the increase of the total H 2 amount up to 7.3 L (49 cm 3 /g STP), or 40% of the reversible hydrogen capacity of the material. The observed reduction of the H 2 capacity is mainly caused by mass transfer limitations [32]. Further capacity drop at the presence of CO 2 and CO has its origin in the deterioration of H 2 absorption kinetics, very strong for the unmodified material (Fig.…”

“…The corresponding surface modification procedures for the preparation of the advanced materials were developed [29,30], and feasibility of their application for hydrogen purification from (CO 2 þ CO)-containing gases was demonstrated [31,32]. The novel features of the developed surface modification procedures include (i) enhancement of PGM deposition by surface functionalisation of the metallic hydride-forming material [25,28,29], and (ii) combination of fluorination and enhanced PGM deposition procedures [24,28,30].…”

“…The fluorination and autocatalytic deposition of Pd were applied to w300 g batch of the La(Ni,Co,Al,Mn) 5 substrate. Further details on the surface modification procedure and characterisation (including activation performances) of the surface-modified materials can be found elsewhere [21,24,28,30,32].…”

“…Further details on the prototype H 2 separation system, its operation and testing can be found elsewhere [31,32].…”

“…3(b). Good coating morphology and activation performances of the surfacemodified material remained after the application of the surface modification procedure in the upscaled amounts, up to 1.5 kg of the substrate per a load [32]. Depending on the batch size, the surface-modified materials contained 0.7 to 7.9 wt% F and 1.3 to 5.2 wt.…”