Recent advances in hydrogen production through catalytic steam reforming of ethanol: Advances in catalytic design

Abstract

Catalytic reforming is a promising technology for producing renewable fuels; however, developing highly stable, efficient, green, and economical metallic catalysts that reduce metal sintering and carbon formation while improving catalyst activity, selectivity, and stability remains a major issue. In this regard, numerous studies have been documented in the past couple of decades evaluating the effects of various supports and promoters using ethanol as a co‐reactant in the catalytic steam reforming to produce energy‐efficient gaseous fuel, that is, hydrogen. This review article compiles research work focused on the catalytic reforming of ethanol reported in the last decade. Also, the outcomes of experimental studies have been presented and discussed for parametric analysis as case studies. The review shows that ethanol conversion, hydrogen selectivity, and catalyst stability are strongly influenced by the physicochemical properties of the catalyst, synthesis method, support choice, promoters, temperature, pressure, steam‐to‐ethanol ratio, and hourly space velocity. Noble metals (e.g., Pt, Rh, Ru, Pd, and Au), transition metals (e.g., Ni, Co, and Cu), and bimetallic composites were the most used catalysts in ethanol‐steam reforming reactions. Also, proper selection of support and promoter plays a significant role in modifying catalyst morphology, surface area, and particle size, enhancing selectivity, and reducing catalyst carbon deposition.

Recent Status in Catalyst Modification Strategies for Hydrogen Production from Ethanol Steam Reforming

“…The higher hydrogen yield is closely related to the functional characteristics of catalysts as follow: (I) excellent ability for CÀ C and CÀ H bonds capture to produce CO and CO 2 , and instead of the CÀ O bond activation to promote the formation of CH 4 ; (II) promoting the activation and dissociation of H 2 O to produce mobile oxygen species; (III) with the WGSR promoting effect rather than the trend of CO or CO 2 methanation. [48,52,58] Understanding the catalytic mechanism and identifying catalytic active sites in ESR reaction is of great significance to the structure design and optimization of effective catalysts. When metal and reducible oxide components co-exist, this excellent catalytic performance is always connected closely with the metal-support interfacial active sites due to the strong electronic perturbation and metal-support interaction.…”

“…In recent years, many new catalytic materials have been studied to realize these key steps of catalytic reforming reaction. Concretely, the C−C bond cleavage in ethanol molecule makes the reaction products and reforming routes quite complex, and numerous side reactions could occur during whole catalysis process [57,58] . Some of the undesirable products have been deemed the precursors of carbon laydown, the formation of them not only consumed lots of hydrogen atoms but also caused catalysts deactivation [49,59,60] …”

“…Nevertheless, selective H 2 production is an arduous task due to the methanation of CO and CO 2 with H 2 , causing unwanted hydrogen consumption (Eqs. 9, 10) [58,61] . In addition, the ethanol and acetaldehyde decomposition as the targeted inhibitory reactions is the main paths for the produce of inactive methane [61,68] .…”

“…Focusing on a complex reaction network in ESR, the reactivity of ESR is strongly dependent on the catalysts structure. The higher hydrogen yield is closely related to the functional characteristics of catalysts as follow: (I) excellent ability for C−C and C−H bonds capture to produce CO and CO 2 , and instead of the C−O bond activation to promote the formation of CH 4 ; (II) promoting the activation and dissociation of H 2 O to produce mobile oxygen species; (III) with the WGSR promoting effect rather than the trend of CO or CO 2 methanation [48,52,58] . Understanding the catalytic mechanism and identifying catalytic active sites in ESR reaction is of great significance to the structure design and optimization of effective catalysts.…”

Issue Highlights

“…Additionally, the article highlights significant progress in catalytic design, shedding light on the ongoing scientific efforts to advance reforming technology towards a more sustainable and efficient future. [3]…”