A Comparison of Steam Reforming of Two Model Bio‐Oil Fractions

Two model bio‐oil fractions were chosen as two different major classes of components present in bio‐oil. Steam reforming of the two fractions was carried out to investigate the gas product distributions and carbon deposition behavior. Higher H₂ yield and carbon conversion to the gaseous phase can be obtained at relatively low temperature (650 °C) for steam reforming of the light fraction. For steam reforming of the heavy fraction, a higher temperature (800 °C) is necessary to obtain higher H₂ yield and carbon conversion to the gaseous phase. At 800 °C, the heavy fraction requires a higher steam to carbon ratio (10) than that for the light fraction (7) to achieve efficient steam reforming. Based on the same carbon space velocity, for 10 h stream time, the drop of H₂ yield and carbon conversion to the gaseous phase in the steam reforming of the heavy fraction is more rapid than that of the light fraction. Carbon deposition in the steam reforming of the heavy fraction is much more severe than that of the light fraction, as determined by carbon content analysis and SEM detection.     

Glycerol‐Reforming Kinetics Using a Pt/C Catalyst

Catalytic steam reforming of glycerol, a by‐product in biodiesel production, represents an attractive route to hydrogen. For the first time, the kinetics of the glycerol steam reforming reaction over a Pt/C catalyst was considered. Kinetic data, i.e., glycerol conversion vs. space time, were obtained experimentally by using a fixed‐bed reactor and were analyzed by the integral method of analysis. It was found that in the studied ranges of temperature from 623 to 673 K and space time from 0.39 to 1.56 g h/mol the investigated reaction is of the first‐order with respect to glycerol. The specific reaction rate constant at 673 K was determined to be 1.1·10⁵ cm³/g_cat h. The values of glycerol conversion predicted by the first‐order kinetic model were in good agreement with those obtained experimentally. The increase in temperature, space time, and initial water/glycerol ratio caused the expected increase in hydrogen yield.     

Hydrogen Production by Steam Reforming of Fusel Oil Using a CeCoOx Mixed-Oxide Catalyst

Various CeCoO_x mixed-oxide catalysts with different Ce/Co ratios were prepared by surfactant-assisted template precipitation of CeO₂ and Ce₃O₄. The obtained catalysts were characterized by X-ray diffraction, X-ray photoelectron spectra, hydrogen temperature-programmed reduction, nitrogen physisorption, and transmission electron microscopy. In general, the mixed-oxide CeCoO_x catalysts showed well-dispersed CeO₂ and Co₃O₄ and good catalytic characteristics including a high specific surface area and porous structure. The effectiveness of the prepared catalysts on the hydrogen (H₂) production from steam reforming of fusel oil was studied in a packed-bed reactor. Co played an important role in C–C scission to break down the large C_2–5 molecules into smaller species resulting in H₂ formation. Ce could provide supplementary active oxygen to prevent coke formation on Co, resulting in a more stable activity of the mixed-oxide catalyst throughout the reaction course.     

Catalytic Steam Reforming of Fast Pyrolysis Bio‐Oil in Fixed Bed and Fluidized Bed Reactors

Catalytic steam reforming of bio‐oil is an economically‐feasible route which produces renewable hydrogen. The Ni/MgO‐La₂O₃‐Al₂O₃ catalyst was prepared with Ni as active agent, Al₂O₃ as support, and MgO and La₂O₃ as promoters. The experiments were conducted in fixed bed and fluidized bed reactors, respectively. Temperature, steam‐to‐carbon mole ratio (S/C), and liquid hourly space velocity (LHSV) were investigated with hydrogen yield as index. For the fluidized bed reactor, maximum hydrogen yield was obtained under temperatures 700–800 °C, S/C 15–20, LHSV 0.5–1.0 h^–1, and the maximum H₂ yield was 75.88 %. The carbon deposition content obtained from the fluidized bed was lower than that from the fixed bed. The maximum H₂ yield obtained in the fluidized bed was 7 % higher than that of the fixed bed. The carbon deposition contents obtained from the fluidized bed was lower than that of the fixed bed at the same reaction temperature.     

Steam Reforming of Bio‐Oil for Hydrogen Production: Effect of Ni‐Co Bimetallic Catalysts

Various Ni‐Co bimetallic catalysts were prepared by incorporating sol‐gel and wet impregnation methods. A laboratory‐scale fixed‐bed reactor was employed to investigate their effects on hydrogen production from steam reforming of bio‐oil. The catalyst causes the condensation reaction of bio‐oil, which generates coke and inhibits the formation of gas at temperatures of 250 °C and 350 °C. At 450 °C and above the transformation of bio‐oil is initiated and gaseous products are generated. The catalyst also can promote the generation of H₂ as well as the transformation of CO and CH₄ and plays an active role in steam reforming of bio‐oil or gaseous products from bio‐oil pyrolysis. The developed 3Ni9Co/Ce‐Zr‐O catalyst achieved maximum hydrogen yield and lowest coke formation rate and provided a better stability than a commercial Ni‐based catalyst.     

Steam reforming of the aqueous fraction of bio-oil over structured Ru/MgO/Al2O3 catalysts

A catalyst consisting of Ru (5%) dispersed on 15% MgO/Al₂O₃ carrier exhibits high activity and selectivity, as well as satisfactory stability with time on stream, under conditions of steam reforming of acetic acid, a model compound for pyrolysis oil. The presence of MgO in the catalyst formulation is shown to be related to oxygen and/or hydroxyl radical spillover from the carrier to the metal particles. A series of Ru/MgO/Al₂O₃ catalysts supported on cordierite monoliths, ceramic foams and γ-Al₂O₃ pellets were prepared and tested for the production of hydrogen by catalytic steam reforming of the aqueous fraction of bio-oil. All different structural forms of the catalyst exhibited satisfactory activity, converting completely the bio-oil, good selectivity toward hydrogen and satisfactory stability with time on stream. However, the catalyst supported on pellets exhibited the best catalytic performance, among all catalysts investigated. Reforming reactions, and thus hydrogen production, are favoured at high temperatures and low space velocities. Coking is one of the most significant problems encountered in these processes. It was found that only a small part of the incoming carbon is deposited on the catalyst surface, which is mainly present as CH_x. However, coke deposition is more intense on the reactor wall above the catalytic bed, due to homogeneous polymerization of unstable ingredients of bio-oil.     

Kinetics and Reactor Modeling of Hydrogen Production from Glycerol via Steam Reforming Process over Ni/CeO2 Catalysts

As a result of skyrocketing prices, environmental concerns and depletion associated with fossil fuels, renewable fuels are becoming attractive alternatives. In this respect, the demand for biodiesel has increased tremendously in recent years. Increased production of biodiesel has resulted in a glut of glycerol that has reduced the demand for this once valuable commodity. Consequently, finding alternative uses for glycerol is a timely proposition. One alternative is producing renewable hydrogen from this cheap commodity. Only a handful of studies have been conducted on producing hydrogen from glycerol. Previous studies have mainly focused on finding effective catalysts for glycerol steam reforming. This paper extends previous knowledge by presenting kinetic parameters in relation to glycerol steam reforming over Ni/CeO₂ and a reactor modeling. The study found that the activation energy and the reaction order for the glycerol steam reforming reaction over Ni/CeO₂ catalyst were 103.4 kJ/mol and 0.233, respectively.     

Steam reforming of ethanol over Pt–Ni Catalysts

A parametric study was conducted over Pt–Ni/δ-Al₂O₃ to explore the effect of Pt and Ni contents on the ethanol steam reforming characteristics of the bimetallic catalyst. Experiments with catalysts having 0.2–0.3 wt%Pt and 10–15 wt%Ni contents indicated that the best ethanol steam reforming performance is achieved over 0.3 wt%Pt–15 wt%Ni/δ-Al₂O₃. Kinetics of ethanol steam reforming was studied over this catalyst in the 673–823 K interval using differential and integral methods of data analysis. A power-function rate expression was obtained with reaction orders of 1.01 and −0.09 in ethanol and steam, respectively, and the apparent activation energy of ethanol steam reforming over 0.3 wt%Pt–15 wt%Ni/δ-Al₂O₃ was calculated as 59.3 ± 2.3 kJ mol⁻¹.     

金属／MgO上的乙醇水蒸气重整制氢

研究了氧化镁负载镍、铁、钴、锰、钼、铜和锡等金属催化剂在乙醇水蒸气重整反应的性能,结果表明在650℃,101．3kpa条件下,所有催化剂的活性都较高,乙醇接近完全转化,而对氢的选择性顺序为：Ni〉Co〉Sn〉Cu〉Fe〉Mo〉Mn。除镍的选择性是随温度上升之外,其他催化剂的选择性都随温度变化有个最佳值。镍催化剂的TPR和XRD表征表明,催化剂中存在3种形态的镍。     

Hydrogen Production by Steam Reforming of Ethanol on Potassium-Doped 12CaO · 7Al2O3 Catalyst

The performance of hydrogen production from steam reforming of ethanol were investigated by using the K-doped 12CaO · 7Al₂ O₃ catalyst (defined as C12A7–O⁻/x%K). The conversion of ethanol and hydrogen yield over C12A7–O⁻/x%K catalyst mainly depended on the temperature, K-doping amount, steam-to-carbon ratios (S/C) and contact time (W/F). In order to identify the catalyst’s characteristic and active species on the catalyst’s surface, Brunauer-Emmett-Teller (BET) surface area, CO₂ temperature programmed desorption (CO₂TPD), X-ray diffraction (XRD), Fourier transform infrared (FT–IR) and X-ray photoelectron spectroscopy (XPS) were carried out. Based on the characterization, it was found that active oxygen species and doped potassium play important roles in steam reforming of ethanol over C12A7–O⁻/27.3%K catalyst.     

Preparation of Catalyst Ni–Cu/CNTs by Chemical Reduction with Formaldehyde for Steam Reforming of Methanol

The novel catalyst Ni–Cu alloys supported on carbon nanotubes (CNTs) was prepared by reduction with formaldehyde and applied in steam reforming of methanol. With nitric acid and sulfuric acid to create defects on the surface of CNTs and using ethanol to improve the hydrophilicity of CNTs, the Ni–Cu alloys were anchored on the surface of CNTs by co-reduction of Ni- and Cu-precursors under the use of tetra-n-methylammonium hydroxide to reduce the aggregation of Ni–Cu particles. In contrast, Ni–Cu catalyst supported on activated carbon (Ni–Cu/C) was prepared as well, and the bimetal of Ni and Cu supported on CNTs (Ni/Cu/CNTs) was attained by successive reduction of first Cu- and then Ni-precursors. The catalysts were characterized with XRD, ED, FESEM, transmission electron microscopy, and Thermogravimetric analysis. The hydrogen yield in steam reforming of methanol was near 100% at 360 °C over 20 wt.% Ni₂₀–Cu₈₀/CNTs. The catalytic activity of Ni₂₀–Cu₈₀/CNTs is much higher than that of Ni₂₀–Cu₈₀/C and Ni₂₀/Cu₈₀/CNTs.     

Investigation of Promoted Cu/ZnO/Al2O3 Methanol Steam Reforming Nanocatalysts by Full Factorial Design

A Cu/ZnO/Al₂O₃ nanocatalyst was applied for hydrogen production via steam reforming of methanol in a fixed‐bed reactor. Modified forms of the catalyst were prepared by adding small amounts of Ba, Zr, and Ce oxides. The catalysts were characterized by means of N₂ adsorption‐desorption, X‐ray diffraction, and scanning electron microscope techniques. Full factorial design was used to optimize the required number of experiments and evaluate the catalytic activity in a fixed‐bed reactor. The oxide additives reduced the production of carbon monoxide and increased the selectivity of carbon dioxide as well as the yield of hydrogen production. Among the studied catalysts, the Cu/ZnO/Al₂O₃/CeO₂/ZrO₂ catalyst presented the best performance.     

Kinetics and Reactor Modeling of the Steam Reforming of Methanol over a Mn‐Promoted Cu/Al Catalyst

The kinetics of the steam reforming of methanol (SRM) was studied in a packed‐bed reactor over a Mn‐promoted Cu/Al₂O₃ catalyst under defined conditions. A Langmuir‐Hinshelwood‐Hogan‐Watson (LHHW)‐type mechanism that assumes the dissociative adsorption of methanol on two distinct active sites as the rate‐controlling step was found to satisfactorily describe the SRM reaction with activation energies of 77.3 and 64.5 kJ mol^?1 at low and high temperature, respectively. No mass or heat transfer limitations were observed under the experimental conditions used in this study. A reactor model was also developed, validated, and employed to predict the conversion, temperature, and concentration profiles. The axial dispersion had no influence on the temperature distribution but the effect was more pronounced on the methanol conversion.     

Steam Reforming of Sunflower Oil over Ni/Al Catalysts Prepared from Hydrotalcite-Like Materials

Using catalytic steam reforming of biofuels to produce hydrogen for energy systems based on fuel cells is an option that may help to reduce the net emissions of CO₂ into the atmosphere. Vegetable oils are some of the most interesting options because of their high potential yield of hydrogen. They are, however, more difficult to reform than the light hydrocarbon feedstocks that are used for producing hydrogen industrially by steam reforming. Catalysts prepared from hydrotalcite-like materials are promising for use in the steam reforming of vegetable oils, since their catalytic activity is significantly higher than that of commercial catalysts for hydrocarbon steam reforming. In this paper, a study is made of how the nickel content of HT-derived catalysts affects their activity for steam reforming of sunflower oil. Three catalysts were prepared with Ni/Al atomic ratios of 1, 2, and 3, respectively. The samples were characterized by various techniques to correlate their activity with the structural characteristics of the catalysts: X-ray diffraction (XRD), BET, thermogravimetric analysis (TGA), and hydrogen chemisorption. The results showed that the catalyst activity increased as the nickel content in the material decreased. The support and its properties seemed to play a key role in the performance of the HT-derived catalysts. This is probably because a decrease in the Ni content produces a better dispersion of the metal and higher BET areas, which leads to a higher capacity for water adsorption. With the most active catalyst (Ni/Al of 1), 2.2 mol H₂/(g_cat h) was produced at 575 °C, 2 bar, and a steam-to-carbon ratio of 3.     

Ni/ZnO-ZrO2催化低温乙醇水蒸气重整制氢

以草酸钠为共沉淀剂,采用共沉淀法制备了以ZnO-ZrO2为载体的镍基乙醇水蒸气重整制氢催化剂(Ni/ZnO-ZrO2)。考察了不同锌锆摩尔比的ZnO-ZrO2负载的镍基催化剂在300～450℃催化乙醇水蒸气重整制氢的反应性能。用TPR、TPO、XRD对催化剂试样进行了表征。结果表明,当n(Zn)∶n(Zr)=1∶1,Ni负载质量分数10%时,催化剂中有镍锌复合氧化物生成,350℃时乙醇转化率达100%,450℃氢气选择性接近90%;TPO结果表明,ZnO-ZrO2复合载体可以降低催化剂上的积炭量。     

Syngas Production via Reverse Water‐Gas Shift Reaction over a Ni‐Al2O3 Catalyst: Catalyst Stability,Reaction Kinetics,and Modeling

The synthesis of liquid fuels from CO₂, e.g., separated from flue gases of power plants, and H₂ from renewables, i.e., water electrolysis, is a concept for substituting fossil fuels in the transport sector. It consists of two steps, syngas production via reverse water‐gas shift (RWGS) and synfuel production by Fischer‐Tropsch synthesis. Research is concentrated on the RWGS using a Ni‐catalyst. The catalyst shows an appropriate performance in catalyzing the RWGS. The catalyst is stable at technically relevant temperatures. The intrinsic and effective kinetics were determined and considerations on a technical application of the process are proposed.     

Ethanol Steam Reforming Followed by Water-Gas Shift Reaction over Ce-Ni/MCM-41 and Fe-Based Catalysts

Current research focuses on hydrogen production from ethanol steam reforming (ESR) followed by water-gas shift (WGS) reaction. Ce-Ni/MCM-41 and Fe/Ce/M (where M = K, La, Ti) catalysts were prepared by the wet-impregnation technique and used for the ESR and WGS reactions, respectively. All experiments were carried out at 600 °C. The effects of the reduction time, the ratio of the two catalysts, and their arrangement were also investigated. The best results were obtained using Fe/Ce/Ti as WGS catalyst and with a separate array because the H₂ production and CO₂ level in the product gas were improved while that of CO was reduced. To generate high-purity hydrogen, the CaO-based adsorbent was used as a third layer to adsorb CO₂ from the gaseous products.     

Reforming of methane and coalbed methane over nanocomposite Ni/ZrO2 catalyst

Nanocomposite Ni/ZrO₂-AN catalyst consisting of comparably sized Ni metal and ZrO₂ nanoparticles is studied in comparison with zirconia- and alumina-supported Ni catalysts (Ni/ZrO₂-CP and commercial Ni/Al₂O₃-C) for steam reforming of methane (SRM) and for combined steam and CO₂ reforming of methane (CSCRM). The reactions are performed under atmospheric pressure with stoichiometric amounts of H₂O and CH₄ or (H₂O + CO₂) and CH₄ at 1073 K. Under a wide range of methane space velocity (gas hourly space velocity of methane GHSV_CH4 = 12,000–96,000 ml/(h g_cat.), the nanocomposite Ni/ZrO₂-AN catalyst always shows higher activity and stability for both SRM and CSCRM reactions. The two supported Ni catalysts (Ni/ZrO₂-CP and Ni/Al₂O₃-C) exhibit fairly stable catalysis under low GHSV_CH4 but they are easily deactivated under high GHSV_CH4 and become completely inactive when they are reacted for ca.100 h at GHSV_CH4 = 48,000 ml/(h g_cat.). The CSCRM reaction is carried out with different H₂O/CO₂ ratios in the reaction feed while keeping the molar ratio (H₂O + CO₂)/CH₄ = 1.0, the results prove that the nanocomposite Ni/ZrO₂-AN catalyst can be highly promising in enabling a catalytic technology for the production of syngas with flexible H₂/CO ratios (ca. H₂/CO = 1.0–3.0) to meet the requirements of various downstream chemical syntheses.     

Production of hydrogen over bimetallic Pt–Ni/δ-Al2O3: I. Indirect partial oxidation of propane

Indirect partial oxidation (IPOX) of propane was studied over bimetallic 0.2 wt.% Pt–15 wt.% Ni/δ-Al₂O₃ catalyst in the 623–743 K temperature range. The unreduced and reduced forms of the catalyst were characterized by ESEM–EDAX and X-ray diffraction (XRD). In the IPOX tests, the effects of steam to carbon ratio (S/C), carbon to oxygen ratio (C/O₂) and residence time (W/F (g_cat h/mol HC)) on the hydrogen production activity, selectivity and product distribution were studied in detail. The effect of temperature program applied (increasing from 623 to 743 K, ITP; decreasing from 743 to 623 K, DTP) during reaction was also tested. The results showed that the Pt–Ni bimetallic system has superior performance characteristics compared to the monometallic catalysts reported in literature. The reason is thought to be the utilization of the catalyst particles as micro heat exchangers during IPOX; the heat generated by Pt sites during exothermic total oxidation (TOX) being readily transferred through the catalyst particles acting as micro heat exchangers to the Ni sites, which promote endothermic steam reforming (SR). The optimal conditions were found as S/C = 3, C/O₂ = 2.70 and W/F = 0.51 g_cat h/mol HC for IPOX of propane on the basis of high hydrogen productivity and selectivity between 623 and 748 K for the experimental conditions tested. The thermo-neutral points obtained showed the sustainability of reaction in terms of energy.     

The Effects of PdZn Crystallite Size on Methanol Steam Reforming

Exceptional activity and selectivity of Pd/ZnO catalysts for methanol steam reforming have been attributed to the formation of PdZn alloy. In this paper, we evaluated the crystallite size effects of PdZn alloy on methanol steam reforming. An organic preparation method was used to avoid the complexity from the alteration of ZnO morphology typically associated with the conventional aqueous preparation method. Both Pd loading and reduction temperature (>350 °C) were used to vary the crystallite size of PdZn alloy. Experimental activity studies and transmission electron microscope (TEM) characterizations indicated that formation of large sized PdZn crystallites exhibit high reactivity and low CO selectivity during methanol steam reforming.