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. 相似文献
The renewable hydrogen generation through ethanol steam reforming is one of the anticipated areas for sustainable hydrogen generation. To elucidate the role of Ni and Co with ZSM-5 support, catalysts were prepared by wet impregnation method and ethanol steam reforming(ESR) was performed. The catalysts were characterized by HR-XRD, ATR–FTIR, HR-SEM, TEM with SAED, EDAX, surface area analyzer and TPR. It had shown complete ethanol conversion at 773 K, but the selectivity in hydrogen generation was found higher for 10% Ni/ZSM-5 catalyst as compared to 10% Co/ZSM-5. The 10% Ni/ZSM-5 catalyst has about 72% hydrogen selectivity at temperature 873 K. It indicates that Ni is a more sustainable catalyst as compared to Co with ZSM-5 support for ESR. The C_2H_4 was found major undesirable products up to 823 K temperature. Nevertheless, the 10% Ni/ZSM-5 catalyst had shown its stability for high temperature(873 K) ESR performance. 相似文献
Honeycomb structures loaded with hydrotalcite-derived cobalt catalysts doped with various amounts of Pt and Rh have been tested in the steam reforming of ethanol at 523–823 K under different operational conditions. Catalysts promoted with noble metals are significantly more active than non-promoted hydrotalcite-derived cobalt but, at the same time, they build up carbon very efficiently. Electron microscopy, magnetic measurements and X-ray photoelectron spectroscopy reveal the occurrence of metal cobalt nanoparticles in the samples promoted with noble metals after reaction. According to the TPR profiles recorded over the hydrotalcite-derived cobalt catalysts doped with Pt and Rh, it is concluded that noble metals strongly promote cobalt reduction under ethanol steam reforming (ESR) conditions. Cobalt nanoparticles thus formed are very active for ethanol reforming but, at the same time, they originate severe carbon deposition. In contrast, non-promoted hydrotalcite-derived cobalt catalysts are less active for ESR but do not form carbon due to the absence of metallic cobalt. 相似文献
The paper presents a short review of strategies used to develop coke resistant, nickel-based, catalysts for autothermal reforming of ethanol to hydrogen. Autothermal reforming of ethanol can be used in conjunction with pronton-exchange membrane fuel cells (PEMFCs) in the transportation sector, stationary and portable applications to replace the use of fossil fuels. Nickel-based catalysts are used in commercial processes for their high carbon–carbon bond cleavage and low cost compared to noble metals. However, the use of nickel-based catalysts is challenged by rapid deactivation caused by coke formation. A considerable effort is expended on innovating strategies to develop coke resistant nickel-based catalysts. The strategies reviewed in this paper are (i) the use of catalysts’ preparation methods targeting high dispersion of nickel nanoparticles smaller than the critical size of 10 nm (nm); (ii) modifying commonly used acidic supports (alumina, silica et cetera) to passivate the acidity to inhibit the production of coke precursor-ethylene; (iii) the addition of promoters and second active metals to promote supports and the active phase; (iv) controlling operating conditions to inhibit coke formation and the use of precursors with well-defined structures to stabilize highly dispersed nickel nanoparticles.
The propensity of carbon support for methanation in a hydrogen-containing medium is a problem for active ruthenium ammonia synthesis catalysts, since this leads to the degradation of the support and the sintering of the active component. This review analyses some key works on approaches to methanation inhibition and their results to show that, on the whole, an algorithm for solving the methanation problem has been found, i.e., the graphitization of carbon supports at high temperatures (up to 2000°C) and the introduction of ruthenium promoters, specifically alkali (Cs, K) and alkali-earth (Ba) oxides, whose role is to modify the electron state of ruthenium and block the surface of a carbon support to prevent it from interacting with active hydrogen. The most efficient catalyst not liable to methanation up to 700°C and a hydrogen pressure of 100 atm has been found. The resulting analysis can be useful in selecting and preparing Me/C catalysts in which Me represents metals of the VIII Group and others. 相似文献
The paper reports experimental results concerning the influence of the support nature (TiO2, ZnO, Al2O3 and Al2O3–Fe2O3) of nickel catalysts on their activity, selectivity and coking phenomenon in the steam reforming of ethanol in the range of 570–870 K. The chemical transformations of ethanol occurring on the catalyst support make its chemical nature an important factor affecting the productivity and selectivity of the process. It was found that the most suitable supports in nickel catalysts designed for hydrogen generation in the steam reforming of ethanol are ZnO and TiO2. Taking into consideration both the efficiency of hydrogen generation and the intensity of carbon deposition, the optimum temperature of the process of the steam reforming of ethanol is below 750 K. An improvement in the selectivity of hydrogen generation and diminishing of the formation of undesirable products may be obtained by promoting nickel catalysts with sodium. 相似文献
A high level of hydrodenitrogenation (HDN) is required to achieve a desirable conversion of other hydroprocessing reactions. This results from a strong adsorption of nitrogen‐containing compounds on catalytic sites that slows down the hydrogen activation process and hinders the adsorption of other reactants. Studies on model compounds and real feeds indicate that less than 50 ppm of nitrogen in the feed can poison catalytic sites. Kinetic studies determined adsorption constants of various nitrogen‐containing compounds and concluded that at least four different catalytic sites are required to interpret experimental observations in contrast with a dual site site?concept, which only considered two sites. The advancements in experimental techniques allowed identification of products formed during very early stages of hydrodenitrogenation. These results confirmed that the removal of the amino group from saturated amines, as the last step in hydrodenitrogenation, is governed by the type of carbon to which the amino group is attached rather than the number of hydrogen atoms attached to carbon in α and β position to nitrogen Performance of conventional Co(Ni)Mo(W)/Al2O3 catalysts during hydrodenitrogenation was enhanced by combination with various additives and by replacing the traditionally used γ‐Al2O3 support with novel supports. Catalytic functionalities could be modified by using different precursors of active metals and varying conditions during preparation. Progress has been made in the development of catalysts possessing a high selectivity for hydrodenitrogenation. In this case, the nonconventional catalysts based on the carbides and nitrides of transition metals exhibited high activity and selectivity. Noble metal sulfides alone or supported on different supports were active for HDN as well. Feedstocks used for catalyst evaluation included model compounds and mixtures of model compounds as well as real feeds. The challenges in the development of catalysts for hydrodenitrogenation of heavy feeds containing asphaltenes and metals have been identified. 相似文献