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

Abstract

Hydrogen as the most promising alternative energy vector to fossil stands out due to its highly energy density and zero pollution. Extending the hydrogen feedstock from hydrocarbons (e. g., methane) to biomass derived oxygen‐containing compounds (CH3OH, C2H5OH etc.) provides the opportunity for low environmental pollution as well as a promising sustainable energy economy. Recently, ethanol with less toxic and high calorific value than traditional fossil energy (coal, oil and natural gas) has garnered significant attention for ethanol steam reforming (ESR) to produce hydrogen, a key component in fuel cell cogeneration system. This paper reviews recent advances on the catalyst developing strategies including structural constitution control, oxide supports modification, surface topography control and bimetallic interactions, and further discusses the catalytic mechanisms, anti‐carbon deposition and sintering resistance strategies on the ethanol steam reforming (ESR) processes. Finally, the challenges and possible strategies for the development of high‐performance catalysts in terms of fundamental research have been discussed.

Global Vision of the Reaction and Deactivation Routes in the Ethanol Steam Reforming on a Catalyst Derived from a Ni–Al Spinel

“…8 It is remarkable the bioethanol availability, whose production is predicted to expand up to 80 billion gallons by 2050 due to the increasing valorization of lignocellulosic, agricultural, and forestry wastes into ethanol. 9 This article is licensed under CC-BY 4 The H 2 production from bioethanol avoids the costly separation and purification steps to remove H 2 O that are traditionally required for the use of ethanol as a fuel, and it can be carried out by means of different technologies: 10 steam reforming (SR), partial oxidation (PO), autothermal reforming (ATR), and dry reforming (DR). The know-how of the industrially extended SR of methane/natural gas provides the fundamentals (catalysts, reaction mechanisms, and reactor design) for the prospective scale-up of the ethanol steam reforming (ESR) process in the short term.…”

“…Likewise, the development of H 2 purification operations has also reached a high technological level in the SR of methane/natural gas, comprising membrane separation and reactors to convert the residual CO by water gas shift (WGS) or selective oxidation reactions. 9,11 The reactions involved in the ESR are summarized in Table 1, including reactions well established in the literature 12−15 for the formation of the desired products (H 2 or syngas), byproducts (CO, CO 2 , and CH 4 ), and also the formation of solid carbon materials. The latter may have a key role in catalyst deactivation depending on its origin and nature.…”

“…The most common catalysts for the ESR are based on Ni or Co supported on various oxides and less commonly based on noble metals, such as Pt or Rh. [8][9][10]19,20 Those based on Ni are preferred due to their high activity in the steps of the reforming reaction mechanism, including C−C and C−H bond cleavage, H 2 O adsorption and dissociation, and their comparatively low cost. 21,22 The problem of rapid deactivation of the Ni catalysts by sintering and coke deposition has been a topic of interest to study different preparation strategies and formulations.…”

“…Acidic supports (e.g., acidic Al 2 O 3 ) promote ethanol dehydration, producing C 2 H 4 as an intermediate, 26−28 13,17,29−31 On the other hand, hydrophilic supports (e.g., ZrO 2 ), and those with high oxygen mobility capacity (due to their oxygen vacancies, e.g., CeO 2 ), facilitate the H 2 Oconsuming reactions by contributing to the formation of OH species and to oxidative reactions. 9,22,25 Reaction conditions (such as temperature, steam/ethanol (S/E) ratio, and contact time) also strongly affect the extent of the reactions in Table 1, some of them being limited by the thermodynamic equilibrium. 32−34 Increasing the reaction temperature would favor the SR, decomposition, and gasification reactions and would disfavor the extent of the WGS (moderately exothermic) and Boudouard reactions.…”

“…The know-how of the industrially extended SR of methane/natural gas provides the fundamentals (catalysts, reaction mechanisms, and reactor design) for the prospective scale-up of the ethanol steam reforming (ESR) process in the short term. Likewise, the development of H 2 purification operations has also reached a high technological level in the SR of methane/natural gas, comprising membrane separation and reactors to convert the residual CO by water gas shift (WGS) or selective oxidation reactions. , …”