Co/CeO2 and Ni/CeO2 catalysts for ethanol steam reforming: Effect of the cobalt/nickel dispersion on catalysts properties

A mini review on recent progress of steam reforming of ethanol

H2 is one of the promising renewable energy sources, but its production and transportation remain challenging. Distributed H2 production using liquid H2 carriers is one of the ideal ways of H2 utilization. Among common H2 carriers, ethanol is promising as it has high H2 content and can be derived from renewable bio-energy sources such as sucrose, starch compounds, and cellulosic biomass. To generate H2 from ethanol, steam reforming of ethanol (SRE) is the most common way, while appropriate catalysts, usually supported metal catalysts, are indispensable. However, the SRE process is quite complicated and always accompanied by various undesirable by-products, causing low H2 yield. Moreover, the catalysts for SRE are easy to deactivate due to sintering and carbon deposition under high reaction temperatures. In recent years, lots of efforts have been made to reveal SRE mechanisms and synthesize catalysts with high H2 yield and excellent stability. Both active metals and supports play an important role in the reaction. This mini-review summarizes the recent progress of SRE catalysts from the view of the impacts of active metals and supports and draws an outlook for future research directions.

Novel nano spinel-type high-entropy oxide (HEO) catalyst for hydrogen production using ethanol steam reforming

Catalyst sintering caused by high temperature operating conditions during ethanol steam reforming (ESR) is a common issue for traditional catalysts with low Tammann temperature metals. In recent years, high entropy oxides have been popular in thermal catalysis due to their special thermodynamics and kinetics characteristics, which is expected to be a suitable approach for enhancing catalyst stability. This paper first reports the application of HEO in ESR and the characterization. The results exhibited a nano structure (CoCrFeNiAl)₃O₄ HEO with a spinel-phase and was successfully synthesized by a polyol hydrothermal precipitation-calcination method. An abundance of oxygen vacancies were formed, and were further enriched in a hydrogen atmosphere as the M-O bond opened. Interestingly, its self-reorganization featured the rendered the metals spilling out of the HEO bulk phase as active species for hydrogen production during ESR, whereas the isolated metal cation randomly dissolved into the parent metal oxide cell again after the reaction instead of agglomerating over the catalyst surface. This gave the (CoCrFeNiAl)₃O₄ a large number of dispersed active sites, as well as a high thermal stability. In addition, 81% of the hydrogen yield as well as 85% of H₂ selectivity were achieved at 600 °C. This research might offer possibilities for the development of thermal catalytic hydrogen production under high temperature conditions such as steam reforming.

Steam Reforming of Bioethanol Using Metallic Catalysts on Zeolitic Supports: An Overview

Hydrogen is considered one of the energy carriers of the future due to its high mass-based calorific value. Hydrogen combustion generates only water, and it can be used directly as a fuel for electricity/heat generation. Nowadays, about 95% of the hydrogen is produced via conversion of fossil fuels. One of the future challenges is to find processes based on a renewable source to produce hydrogen in a sustainable way. Bioethanol is a promising candidate, since it can be obtained from the fermentation of biomasses, and easily converted into hydrogen via steam catalytic reforming. The correct design of catalysts and catalytic supports plays a crucial role in the optimization of this reaction. The best results have to date been achieved by noble metals, but their high costs make them unsuitable for industrial application. Very satisfactory results have also been achieved by using nickel and cobalt as active metals. Furthermore, it has been found that the support physical and chemical properties strongly affect the catalytic performance. In this review, zeolitic materials used for the ethanol steam reforming reaction are overviewed. We discuss thermodynamics, reaction mechanisms and the role of active metal, as well as the main noble and non-noble active compounds involved in ethanol steam reforming reaction. Finally, an overview of the zeolitic supports reported in the literature that can be profitably used to produce hydrogen through ethanol steam reforming is presented.

Effect of Potassium Promoter on the Performance of Nickel-Based Catalysts Supported on MnOx in Steam Reforming of Ethanol

The effect of a potassium promoter on the stability of and resistance to a carbon deposit formation on the Ni/MnOx catalyst under SRE conditions was studied at 420 °C for different H2O/EtOH molar ratios in the range from 4/1 to 12/1. The catalysts were prepared by the impregnation method and characterized using several techniques to study their textural, structural, and redox properties before being tested in a SRE reaction. The catalytic tests indicated that the addition of a low amount of potassium (1.6 wt.%) allows a catalyst with high stability to be obtained, which was ascribed to high resistance to carbon formation. The restriction of the amount of carbon deposits originates from the potassium presence on the Ni surface, which leads to (i) a decrease in the number of active sites available for methane decomposition and (ii) an increase in the rate of the steam gasification of carbon formed during SRE reactions.

Towards the Efficient Catalytic Valorization of Chitin to N-Acylethanolamine over Ni/CeO2 Catalyst: Exploring the Shape-Selective Reactivity

Global warming and rising waste content collectively accelerate the development of renewable-derived ‘low-carbon’ chemical technologies. Among all abundant renewables, marine-/food-waste-derived chitin, the only nitrogen-containing sustainable biomass, contains the unique N-acetylglucosamine units, which could be synthetically manipulated to a plethora of organonitrogen chemicals. Herein, we report the efficient one-step catalytic valorization of chitin to N-acylethanolamine over cost-effective Ni/CeO2-based materials, which interestingly demonstrate shape-based reactivity based on CeO2 supports. In general, all three catalysts (Ni on cubic-, rod-, and polyhedral-shaped CeO2 supports) were active for this reaction, but they differed in their catalytic efficiency and time-monitored reaction profiles. Herein, Ni on cubic-shaped CeO2 delivered relatively better and stable catalytic performance, along with its rod-shaped counterpart, while the polyhedral CeO2-based material also delivered decent performance. Such interesting catalytic behavior has been corroborated by their physicochemical properties, as revealed by their characterization studies. Herein, to establish an appropriate structure-property-reactivity relationship, multimodal characterization techniques and control mechanistic experiments have been performed. This work demonstrates a concept to reduce the consumption of primary carbon resources and increase the utilization of secondary waste materials to facilitate a smooth transition from a linear economy (cf. cradle-to-grave model) to a circular economy (cf. cradle-to-cradle model).

The Route from Green H2 Production through Bioethanol Reforming to CO2 Catalytic Conversion: A Review

Currently, a progressively different approach to the generation of power and the production of fuels for the automotive sector as well as for domestic applications is being taken. As a result, research on the feasibility of applying renewable energy sources to the present energy scenario has been progressively growing, aiming to reduce greenhouse gas emissions. Following more than one approach, the integration of renewables mainly involves the utilization of biomass-derived raw material and the combination of power generated via clean sources with conventional power generation systems. The aim of this review article is to provide a satisfactory overview of the most recent progress in the catalysis of hydrogen production through sustainable reforming and CO2 utilization. In particular, attention is focused on the route that, starting from bioethanol reforming for H2 production, leads to the use of the produced CO2 for different purposes and by means of different catalytic processes, passing through the water–gas shift stage. The newest approaches reported in the literature are reviewed, showing that it is possible to successfully produce “green” and sustainable hydrogen, which can represent a power storage technology, and its utilization is a strategy for the integration of renewables into the power generation scenario. Moreover, this hydrogen may be used for CO2 catalytic conversion to hydrocarbons, thus giving CO2 added value.

The Effect of Modifiers on the Performance of Ni/CeO2 and Ni/La2O3 Catalysts in the Oxy-Steam Reforming of LNG

This work interrogates for the first time the catalytic properties of various monometallic Ni catalysts in the oxy-steam reforming of LNG. Various research techniques, including X-ray diffraction (XRD), specific surface area and porosity analysis (BET method), scanning electron microscopy with X-ray microanalysis (SEM-EDS), temperature-programmed desorption of ammonia (TPD-NH₃), temperature-programmed reduction (TPR-H₂) and the FTIR method, were used to study their physicochemical properties. The mechanism of the oxy-steam reforming of LNG is also discussed in this paper. The high activity of monometallic catalysts supported on 5% La₂O₃-CeO₂ and 5% ZrO₂-CeO₂ oxides in the studied process have been proven and explained on the basis of their acidity, specific surface area, sorption properties in relation to the reaction products, the crystallite size of the metallic nickel and their phase composition.

Catalytic wet peroxide degradation of acrylonitrile wastewater by ordered mesoporous Ag/CeO2: synthesis, performance and kinetics

Ordered mesoporous Ag/CeO2 catalysts have been successfully synthesized by a microwave assisted soft template method. The morphology, structure and chemical composition of the catalyst were characterized by XRD, N2 adsorption-desorption, SEM, EDS, TEM and XPS. The study of catalytic performance and reaction kinetics of organic matter degradation in acrylonitrile wastewater was performed in a catalytic wet peroxide (CWPO) system. The degradation pathways of organic matter in acrylonitrile wastewater were elucidated by temporal evolution of intermediates and final products detected by GC/MS analysis along with a continuous flow experiment study. The results show that the Ag/CeO2 has an ordered mesoporous structure, the specific surface area is 91.4-118.2 m2 g-1 and the average pore size is 12.63-16.86 nm. 0.4-Ag/CeO2 showed the best catalytic performance, the COD removal rate reached 94.6%, which was 30% higher than that of CeO2. The degradation is in accordance with the second-order reaction kinetics of the Arrhenius empirical model and Langmuir-Hinshelwood kinetic model. However the latter fits better, and the linear correlation coefficient R 2 is more than 0.98, which describes the adsorption catalytic mechanism of Ag/CeO2. According to the analysis by GC/MS, the organic compounds in acrylonitrile wastewater oxidized into intermediate compounds and other small compounds, then are further oxidized into carbon dioxide and water. The catalytic activity of Ag/CeO2 was the result of the combination of Lewis acid-base position of CeO2 and redox cycle of Ce3+/Ce4+.