Catalytic Production of Renewable Hydrogen for Use in Fuel Cells: A Review Study

Abstract

Hydrogen production from renewable sources is gaining increasing importance for application as fuel, in particular with high efficiency and low impact devices such as fuel cells. In addition, the possibility to produce more sustainable hydrogen for industrial application is also of interest for fundamental industrial processes, such as ammonia and methanol synthesis. Catalytic processes are used in most options for the production of hydrogen from renewable sources. Catalysts are directly involved in the main transformation, as in the case of reforming and of electro-/photo-catalytic water splitting, or in the upgrade and refining of the main reaction products, as in the case of tar reforming. In every case, for the main processes that reached a sufficiently mature development stage, attempts of process design, economic and environmental impact assessment are presented, on one hand to finalise the demonstration of the technology, on the other hand to highlight the challenges and bottlenecks. Selected examples are described, highlighting whenever possible the role of catalysis and the open issues, e.g. for the H2 production from reforming, aqueous phase reforming, biomass pyrolysis and gasification, photo- and electro-catalytic processes, enzymatic catalysis. The case history of hydrogen production from bioethanol for use in fuel cells is detailed from the point of view of process design and techno-economic validation. Examples of steady state or dynamic simulation of a centralised or distributed H2 production unit are presented to demonstrate the feasibility of this technology, that appears as one of the nearest to market. The economic feasibility seems demonstrated when producing hydrogen starting from diluted bioethanol.

Experimental Study on the Ethanol-Assisted Catalytic Steam Reforming of Endothermic Hydrocarbon Fuel

“…Zhang et al mentioned that when the temperature was above 240 °C, ethanol dehydration generated the main product of ethylene. Wang proposed that among all of the decomposition reactions of ethanol, dehydration to ethylene is the main reaction pathway at low temperatures because of the lowest reaction energy barrier, which is consistent with the conclusion of Zhang et al Steam reforming of ethanol (SRE) is an important approach for industrial hydrogen production . Also, the SER process absorbs more heat compared with the pyrolysis of ethanol.…”

“…Wang 27 proposed that among all of the decomposition reactions of ethanol, dehydration to ethylene is the main reaction pathway at low temperatures because of the lowest reaction energy barrier, which is consistent with the conclusion of Zhang et al Steam reforming of ethanol (SRE) is an important approach for industrial hydrogen production. 28 Also, the SER process absorbs more heat compared with the pyrolysis of ethanol. Ni-based catalyst is the commonly used active metal because of its wide availability and low cost.…”

Production of hydrogen from alcohols via homogeneous catalytic transformations mediated by molecular transition-metal complexes

“…Among the different renewable alcohols, bioethanol has gained attention as an emerging hydrogen carrier because of its relatively high hydrogen output (13 wt%). 46 Primary investigations on the liberation of hydrogen from ethanol were reported in the 1970s and 1980s, 47 and as compared to methanol, research on ethanol dehydrogenation lags far behind. 48 In the current section, reforming of ethanol to industrially valuable acetic acid has been discussed.…”

Methane steam reforming over Ni/YSZ cermet anode materials synthesized by different methods

“…In spite of efforts to produce hydrogen by different methods, 4–8 steam reforming of hydrocarbons has remained as a topic of intense research interest because this technique is the most cost-effective syngas (H 2 /CO) production method. 9 Methane can be transformed ex situ into synthesis gas, 10 which can be used as a fuel in solid oxide fuel cells (SOFCs) 11 or converted in situ directly on the Ni–YSZ anode within the fuel cell system 12 to produce electrical and heat energy. The following equilibria have been widely reported for the two strongly endothermic methane steam reforming reactions (1) and (3) and for the moderately exothermic water-gas shift (WGS) reaction (2)CH 4 + H 2 O ⇔ CO + 3H 2 Δ H = +206 kJ mol −1 CO + H 2 O ⇔ CO 2 + H 2 Δ H = −41 kJ mol −1 CH 4 + 2H 2 O ⇔ CO 2 + 4H 2 Δ H = +165 kJ mol −1 …”