Search Results (9)

This study investigates the oxidative steam reforming (OSR) of simulated bio-oil aqueous fractions using Co/CeO₂-SBA-15 catalysts. Five representative compounds—methanol, acetic acid, hydroxyacetone, phenol, and furfural—were evaluated to assess their reactivity for hydrogen production. Aliphatic compounds achieved nearly complete conversion and stable hydrogen yields, while aromatic structures led to lower conversion and higher coke formation. Furfural exhibited higher reactivity than phenol due to its furan ring and aldehyde group. Catalysts with 10 and 20 wt.% Ce showed similar activity, but Co/20CeO₂-SBA-15 presented lower hydrogen yield. For this reason, next experiments of OSR of model compound mixtures were carried out only with Co/10CeO₂-SBA-15. To approach real bio-oil complexity, ternary and quinary mixtures were tested. High conversion and hydrogen yield were maintained over 50 h when the ternary mixture (methanol, hydroxyacetone, and acetic acid) was fed. When the quinary mixture was used as feedstock, which includes furfural and phenol, lower conversions were obtained for these compounds compared to aliphatic ones, although conversions remained above 80% after 50 h (88.9% for furfural and 82.6% for phenol). These results highlight Co/10CeO₂-SBA-15 as a viable catalyst for bio-oil aqueous fraction valorization under OSR conditions. Full article

Among biomass gasification syngas cleaning methods, non-catalytic reforming emerges as a sustainable and high-efficiency alternative. This study employed integrated experimental analysis and kinetic modeling to examine non-catalytic reforming processes of biomass-derived producer gas utilizing a synthetic tar mixture containing representative model compounds: naphthalene (C₁₀H₈), toluene (C₇H₈), benzene (C₆H₆), and phenol (C₆H₅OH). The experiments were conducted using a high-temperature fixed-bed reactor under varying temperatures (1100–1500 °C) and equivalence ratios (ERs, 0.10–0.30). The results obtained from the experiment, namely the measured mole concentration of H₂, CO, CH₄, CO₂, H₂O, soot, and tar suggested that both reactor temperature and O₂ content had an important effect. Increasing the temperature significantly promotes the formation of H₂ and CO. At 1500 °C and a residence time of 0.01 s, the product gas achieved CO and H₂ concentrations of 28.02% and 34.35%, respectively, while CH₄, tar, and soot were almost entirely converted. Conversely, the addition of O₂ reduces the concentrations of H₂ and CO. Increasing ER from 0.10 to 0.20 could reduce CO from 22.25% to 16.11%, and H₂ from 13.81% to 10.54%, respectively. Experimental results were used to derive a kinetic model to accurately describe the non-catalytic reforming of producer gas. Furthermore, the maximum of the Root Mean Square Error (RMSE) and the Relative Root Mean Square Error (RRMSE) between the model predictions and experimental data are 2.42% and 11.01%, respectively. In particular, according to the kinetic model, the temperature increases predominantly accelerated endothermic reactions, including the Boudouard reaction, water gas reaction, and CH₄ steam reforming, thereby significantly enhancing CO and H₂ production. Simultaneously, O₂ content primarily influenced carbon monoxide oxidation, hydrogen oxidation, and partial carbon oxidation. Full article

Steam reforming is an important industrial process for hydrogen production. Acetone, the by-product of phenol production from cumene peroxidation, is a useful source of hydrogen due to its availability and low value compared to hydrogen fuel. This study aimed to utilize the Gibbs free energy minimization method using the Soave–Redlich–Kwong (SRK) equation of state (EOS) to conduct a thermodynamic analysis of the steam reforming process for pure component acetone. The steam reforming process is temperature dependent, with increasing temperatures leading to higher hydrogen production. Competing reactions, particularly the exothermic reverse water–gas shift, impact hydrogen yields beyond 650 °C. The study identified 600 °C as the optimum temperature to strike a balance between maximizing hydrogen production and minimizing the reverse water–gas shift’s impact. The optimal hydrogen yield (70 mol%) was achieved at a steam-to-oil ratio (STOR) of 12. High STOR values shift the equilibrium of the water–gas shift reaction towards hydrogen production due to increased steam, effectively consuming acetone and favoring the desired product. Atmospheric pressure is optimum for hydrogen production because the equilibrium of gas phase reactions shifts in favor of the lighter components at lower pressures. Full article

The elimination of tar impurities from biomass gasification by catalytic steam reforming can provide clean syngas for downstream biofuel synthesis (Fischer–Tropsch). The effects of key operating parameters in CH₄/tar steam reforming were investigated. Ni-Co/Mg(Al)O catalyst performance was tested at model conditions (10/35/25/25/5 wt% CH₄/H₂/CO/CO₂/N₂), changing the temperature (650–800 °C), steam-to-carbon ratio (2–5), tar loading (10–30 g/Nm³), and tar composition (toluene, 1-methylenaphthalene, and phenol). Complete tar elimination was achieved under all conditions, at the expense of catalyst deactivation by coke formation. Post-operation coke characterization was obtained with TPO-MS, Raman spectroscopy, and STEM analysis, providing vital insight into coke morphology and location. Critical low-temperature and high-tar loading limits were identified, where rapid deactivation was accompanied by increasing amounts of hard coke species. A coke classification scheme is proposed, including strongly adsorbed surface carbon species (soft coke A), initial scattered carbon filaments (hard coke B1.1), filament clusters and fused filaments (B2), and strongly deactivating bulk encapsulating coke (B3), formed through progressive filament cluster graphitization. High-molecular-weight tar was found to enhance the formation of strongly deactivating metal-particle-encapsulating coke (B1.2). The results contribute to the understanding of coke formation in the presence of biomass gasification tar impurities. Full article

Over the three-day gasification test of a large coal block with oxygen in atmospheric pressure conditions, the yield and composition of the tar collected was investigated. The tar was sampled approximately every 7 h into sorption tubes directly from the reactor outlet. Sand, with a moisture content of 11%, was used as an insulating material to simulate the environment of the gasified coal seam. Light aromatic hydrocarbons (BTEX), phenols, and polycyclic aromatic hydrocarbons (PAHs) were determined in the tar. The results that were obtained were recalculated into the concentrations of the individual components of the tar and its mass stream in the process gas. The residence time of the tar in the reactor, its molar mass, and the H/C ratio were also calculated. As the reaction progressed, the water that was contained in the wet sand started to react with the gasified coal, which significantly affected the composition and amount of the obtained process gas and the produced tar. Due to an increase in the amount of generated gases and steam, the residence time of the tar vapours in the reactor decreased as the gasification progressed, ranging from approximately 1 s at the beginning of the process to 0.35 s at the end. The obtained tar was characterised by a high average content of BTEX fractions at approximately 82.6%, PAHs at 14.7%, and phenols at 2.7%. Benzene was the dominant BTEX compound, with a concentration of 83.7%. The high content of the BTEX compounds, especially benzene, was a result of secondary processes taking place in the tar (hydrocracking and steam reforming), and as a result of which, in the presence of hydrogen and steam, the heavier components of the tar were transformed into lighter ones. The total yield of the tar from this UCG (underground coal gasification) process—calculated per 1 ton of gasified coal—was 1.8% (counted on the basis of the analysed tar composition). Comparing this result to the efficiency of the classic coking process, the tar yield was about three times lower. Full article

H₂ production can be used as a clean and renewable energy source for various applications, including fuel cells, internal combustion engines, and chemical production. Using nickel-based catalysts for steam reforming biomass tar presents challenges related to catalyst deactivation, poisoning, heterogeneous composition, high process temperatures, and gas impurities. To overcome these challenges, adopting a nickel-based catalyst with selected oxide support and MgO and CaO promoter is a promising approach for improving the efficiency and sustainability of steam reforming for hydrogen production. The majority of studies conducted to date have focused on the steam reforming of particular tar compounds, most commonly benzene, phenol, toluene, or naphthalene, over a range of support catalysts. However, the actual biomass tar composition is complex, and each component impacts how well steam reforming works. In this research, a multi-compound biomass tar model including phenol, toluene, naphthalene, and pyrene underwent a steam reforming process. Various types with 10 wt.% of nickel-based catalysts were generated by the co-impregnation technique, which included 90 wt.% different oxide supports (Al₂O₃, La₂O₃, and ZrO₂) and 10 wt.% of combination alkaline oxide earth promoters (MgO and CaO). Thermogravimetric analysis, Brunauer–Emmett–Teller (BET) method, N₂ physisorption, temperature-programmed reduction (H₂-TPR), temperature-programmed desorption (CO₂-TPD), and X-ray diffraction (XRD) of ni-based catalyst characterized physiochemical properties of the prepared catalyst. The reaction temperature used for steam reforming was 800 °C, an S/C ratio of 1, and a GHSV of 13,500 h⁻¹. Ni/La₂O₃/MgO/CaO (NiLaMgCa) produced the most carbon to-gas conversion (86.27 mol%) and H₂ yield (51.58 mol%) after 5 h of reaction compared to other catalysts tested in this study. Additionally, the filamentous carbon coke deposited on the spent catalyst of NiLaMgCa does not impact the catalyst activity. NiLaMgCa was the best catalyst compared to other catalysts investigated, exhibiting a stable and high catalytic performance in the steam reforming of gasified biomass tar. In conclusion, this study presents a novel approach by adding a combination of MgO and CaO promoters to a ni-based catalyst with various oxide supports, strengthening the metal-support interaction and improving the acid-base balance of the catalyst surface. The mesoporous structure and active phase (metallic Ni) were successfully developed. This can lead to an increase in the conversion of tar to H₂ yield gas and a decrease in the production of undesired byproducts, such as CH₄ and CO. Full article

Hydrogen obtained from biomass derivatives is considered a promising alternative to fossil fuels. The aim of this work is to test the viability of Ni-M/SBA-15 (M: Co, Cu, Cr) catalysts for the hydrogen production from bio-oil aqueous fraction reforming. Tests were performed in a fixed-bed reactor at 600 °C and atmospheric pressure. Firstly, the steam reforming (SR) of acetic acid, hydroxyacetone, furfural and phenol, as representative constituents of the bio-oil aqueous fraction, was carried out. Lower reactivity with increasing carbon number and decreasing steam-to-carbon ratio was observed. Coking rate during SR is a consequence of carbon number and aromaticity of the reactant, as well as the steam-to-carbon ratio. However, deactivation also depends on the graphitization degree of carbon filaments, higher in the case of coke formed from phenol. Then, the performance of the Ni-M/SBA-15 catalysts was studied in the reforming of a bio-oil aqueous fraction surrogate containing the four model compounds. Ni-Co/SBA-15 and Ni-Cr/SBA-15 samples were the most active because Co also catalyze the steam reforming reactions and Cr promotes the formation of very small Ni crystallites accounting for high conversion and the low coke deposition (~8 times lower than Ni/SBA-15) in the form of poorly condensed carbon filaments. Full article

Full factorial experimental design with 32 runs was used to investigate the significant and interaction variable of the reaction parameters on phenol steam reforming toward hydrogen production. Effects of selected factors on the phenol conversion (Y₁) and hydrogen yield (Y₂) were evaluated. These factors were as follows: (A) temperature (500 and 800 °C); (B) feed flow rate (0.16–0.46 mL/min); (C) catalyst weight (0.1–0.3 g); (D) Ni-Co ratio (0–1); and (E) phenol concentration in the feed (2–10 wt %). Ni and Co over ZrO₂ support for catalytic performance of phenol steam reforming (SRP) was prepared by the impregnation method. The result indicated that all the main independent variables had significant influence on the dependent variable of Y₁ and Y₂ with a range of 2.7%–96.8% and 21.4%–72.4%, respectively. Additionally, some interaction variables like AE, BE, CE, and DE have also influenced the Y₁ and Y₂ responses. This design showed that the best initial conditions that produced maximum Y₁ and Y₂ responses were at 800 °C, 0.16 mL/min feed flow rate, 0.3 g of catalyst, 0 ratio of Ni-Co (Co/ZrO₂), and 10 wt % of phenol in the feed, where the phenol conversion was predicted to be 94.98% and the hydrogen yield was predicted to be 67.4%. Within the limits the variables were examined, a regression model which well-fitted the experimental data was proposed. The regression model were reduced to simplify and to get the significant regression coefficient with p-value less than 0.05. Full article

A Ni/meso-MgO catalyst with high surface area and small Ni nanoparticles was synthesized and investigated for hydrogen production by steam reforming of phenol for the first time. Compared to conventional Ni/MgO, the Ni/meso-MgO catalyst showed higher catalytic activity and stability. X-ray Diffraction, N₂ adsorption, hydrogen temperature programmed reduction, transmission electron microscopy and thermal gravimetry results indicated that the Ni/meso-MgO catalyst had higher surface area than Ni/MgO and Ni particles of Ni/meso-MgO were narrowly distributed in the range of 5~6 nm with an average size of 5.3 nm, while Ni particles of Ni/MgO were in the range of 6~10 nm with an average size of 7.92 nm. The small and uniform Ni nanoparticles in Ni/meso-MgO were attributed to the high surface area and the confinement effect of the mesoporous structure of meso-MgO, which could effectively limit the growth of the active metal and stabilize Ni particles during the procedure of NiO reduction. The mesoporous structure of Ni/meso-MgO also played an important role in suppressing Ni nanoparticle sintering and carbon deposition during the steam reforming of phenol reaction. Full article