Search Results (42)

The production of water-in-water emulsion droplets, the coalescence of which is prevented by adding oil-in-water micrometric droplets, is reported. Hexadecane (O) and cetyl trimethyl ammonium bromide (CTAB) were added to a W/W emulsion made of dextran (Dex)-enriched droplets in a Polyethyleglycol (PEG)-enriched continuous phase, and the mixture was further sonicated. Using Nile red to label the oil droplets enabled the observation of their presence at the surface of Dex droplets (5 µm), allowing for stabilizing them, preventing coalescence of the W/W emulsion, and mimicking W/O/W double emulsions. The addition of sulfate derivative of Dextran (DexSulf) allowed for stable droplets of a slightly larger diameter. By contrast, the addition of carboxymethyl Dextran (CMDex) destabilized the initial aqueous double-like emulsion, yielding sequestration of the oil droplets within the Dex-rich phase. Interestingly, addition of DexSulf to that unstable emulsion re-yielded stable droplets. Similar findings (destabilization) were obtained when adding sodium dodecyl sulfate (SDS) to the initial double-like emulsion, which reformed stable droplets when adding positively charged Dextran (DEAEDex) derivatives. The use of fluorescently (FITC) labeled derivatives of Dextran (Dex, CMDex, DEAEDex, and DexSulf) allowed us to follow their position within, out of, or at the interface of droplets in the above-mentioned mixtures. These findings are expected to be of interest in the field of materials chemistry. Full article

This work explores the effect of the incorporation of CeO₂ into Co/SBA-15 catalysts in hydrogen production through acetic acid oxidative steam reforming as a bio-oil aqueous phase model compound. CeO₂ was incorporated (5–30 wt.%) to improve the physicochemical properties of the catalyst. XRD analysis confirmed that the addition of CeO₂ resulted in smaller Co⁰ mean crystallite sizes, while H₂-TPR showed enhanced reducibility properties. The catalytic performance was evaluated in the 400–700 °C range, S/C molar ratio = 2, O₂/C molar ratio = 0.0375, WHSV = 30.2 h⁻¹, and P = 1 atm. Catalysts containing 10 and 20 wt.% of CeO₂ exhibited the best catalytic performance, achieving nearly complete conversions and H₂ yield values, approaching thermodynamic equilibrium at 550 °C. Both samples maintained an acetic acid conversion above 90% after 30 h of time-on-stream, with H₂ yields above 55% along the steam reforming tests. This agrees with their lower coke formation rates (7.2 and 12.0 mg_coke·g_cat⁻¹·h⁻¹ for Co/10CeO₂-SBA15 and Co/20CeO₂-SBA15, respectively). Full article

With the intensification of the global energy crisis, hydrogen has attracted significant attention as a high-energy-density and zero-emission clean energy source. Traditional hydrogen production methods are dependent on fossil fuels and simultaneously contribute to environmental pollution. The aqueous phase reforming (APR) of renewable biomass and its derivatives has emerged as a research hotspot in recent years due to its ability to produce green hydrogen in an environmentally friendly manner. This review provides an overview of the advancements in APR of lignocellulosic biomass as a sustainable and environmentally friendly method for hydrogen production. It focuses on the reaction pathways of various biomass feedstocks (such as glucose, cellulose, and lignin), as well as the types and performance of catalysts used in the APR process. Finally, the current challenges and future prospects in this field are briefly discussed. Full article

Cleavage of C-C bonds is crucial for hydrogen production via aqueous phase reforming of biomass-derived oxygenates. In this study, the hydrogen production performance and C-C bond cleavage capacity of Ni-W/AC catalysts with varying W/Ni ratios are evaluated using ethylene glycol as a model compound. A series of APR experiments conducted suggests that Ni-0.2W/AC catalyst exhibits the highest C₁/C₂₊ ratio of 15.87 and achieves a hydrogen yield of 47.76%. The enhanced Ni-W bimetallic interactions, which significantly improve the efficiency of C-C bond cleavage and increase catalyst activity by promoting active site dispersion, are confirmed by detailed characterization techniques. Further analysis of product distribution provides insights into the reaction pathways of ethylene glycol and the reaction mechanism for ethanol during aqueous phase reforming. All the results indicate that this catalytic reforming method effectively facilitates C-C bond cleavage and hydrogen production, contributing to a better understanding of APR mechanisms for biomass-derived oxygenates. Full article

The transformation of biomass into renewable fuels and chemicals has gained remarkable attention as a sustainable alternative to fossil-based resources. Metal-based catalysts, encompassing transition and noble metals, are crucial in these transformations as they drive critical reactions, such as hydrodeoxygenation, hydrogenation, and reforming. Transition metals, including nickel, cobalt, and iron, provide cost-effective solutions for large-scale processes, while noble metals, such as platinum and palladium, exhibit superior activity and selectivity for specific reactions. Catalytic advancements, including the development of hybrid and bimetallic systems, have further improved the efficiency, stability, and scalability of biomass transformation processes. This review highlights the catalytic upgrading of lignocellulosic, algal, and waste biomass into high-value platform chemicals, biofuels, and biopolymers, with a focus on processes, such as Fischer–Tropsch synthesis, aqueous-phase reforming, and catalytic cracking. Key challenges, including catalyst deactivation, economic feasibility, and environmental sustainability, are examined alongside emerging solutions, like AI-driven catalyst design and lifecycle analysis. By addressing these challenges and leveraging innovative technologies, metal-based catalysis can accelerate the transition to a circular bioeconomy, supporting global efforts to combat climate change and reduce fossil fuel dependence. Full article

Methanol, which can be derived from sustainable energy sources such as biomass, solar power, and wind power, is widely considered an ideal hydrogen carrier for distributed and mobile hydrogen production. In this study, a comprehensive comparison of the thermodynamic and techno-economic performance of the aqueous phase reforming (APR) and steam reforming (SR) of methanol was conducted using Aspen Plus and CAPCOST software to evaluate the commercial feasibility of the APR process. Thermodynamic analysis, based on the Gibbs free energy minimization method, reveals that while APR and SR have similar energy demands, APR achieves higher energy efficiency by avoiding losses from evaporation and compression. APR typically operates at higher pressures and lower temperatures compared to SR, suppressing CO formation and increasing hydrogen fraction but reducing methanol single-pass conversion. A techno-economic comparison of APR and SR for a distributed hydrogen production system with a 50 kg/h hydrogen output shows that although APR requires higher fixed operating costs and annual capital charges, it benefits from lower variable operating costs. The minimum hydrogen selling price for APR was calculated to be 7.07 USD/kg, compared to 7.20 USD/kg for SR. These results suggest that APR is a more economically viable alternative to SR for hydrogen production. Full article

Aqueous-phase reforming (APR) is an alternative method for treating and utilizing biogas slurry (BS) to produce renewable hydrogen from organic oxygen-containing wastewater. Considering the fluctuating characteristics of BS with changes in the degree of fermentation, developing an efficient catalyst is a major concern for the APR of BS. The novel catalyst based on molybdenum-based metal–organic-framework-derived oxides (Mo-MOF-derived α-MoO₃) was reported in this study. The results indicated that the variables (e.g., pH, organic load, and salinity) of BS corresponded to the fermentation times and exhibited decreasing trends after APR under the reaction conditions of 225 °C and 30 min. Decarboxylation was identified as the main side reaction in the APR of BS over the catalyst. An optimal yield of 2.17 mL_hydrogen/mL_BS was achieved when BS was obtained from 6 days of fermentation. Finally, the Mo-MOF-derived α-MoO₃ catalyst was obtained from the greater specific surface area of MOFs. The catalyst had a weaker acidity than the initial α-MoO₃, making it more preferred for facilitating the APR of BS. Full article

Aqueous phase reforming (APR) is a promising method for producing hydrogen from biomass-derived feedstocks. In this study, carbon-supported Pt catalysts containing particles of different sizes (below 3 nm) were deposited on different commercially available carbons (i.e., Vulcan XC72 and Ketjenblack EC-600JD) using the metal vapor synthesis approach, and their catalytic efficiency and stability were evaluated in the aqueous phase reforming of ethylene glycol, the simplest polyol containing both C–C and C–O bonds. High-surface-area carbon supports were found to stabilize Pt nanoparticles with a mean diameter of 1.5 nm, preventing metal sintering. In contrast, Pt single atoms and clusters (below 0.5 nm) were not stable under the reaction conditions, contributing minimally to catalytic activity and promoting particle growth. The most effective catalyst Pt_A/C^K, containing a mean Pt NP size of 1.5 nm and highly dispersed on Ketjenblack carbon, demonstrated high hydrogen site time yield (8.92 min⁻¹ at 220 °C) and high stability under both high-temperature treatment conditions and over several recycling runs. The catalyst was also successfully applied to the APR of polyethylene terephthalate (PET), showing potential for hydrogen production from plastic waste. Full article

Compared to steam reforming, methanol aqueous-phase reforming (APR) converts methanol to hydrogen and carbon dioxide at lower temperatures, but also displays lower conversion rates. Herein, methanol APR is studied over the active Pt/Al₂O₃ catalyst under different operating conditions. Studies were conducted at different temperatures, pressures, methanol mass fractions, and residence times. APR performance was evaluated in terms of methanol conversion, hydrogen production rate, hydrogen selectivity, and by-product formation. The results revealed that an increase in operating pressure and methanol mass fraction had an adverse effect on the APR performance. Conversely, it was found that hydrogen selectivity was unaffected by the operating pressure and residence time for the methanol feed mass fraction of 5%. For the methanol feed mass fraction of 55%, hydrogen selectivity was improved by operating pressure and residence time. The alumina support phase change to boehmite as well as sintering and leaching of the catalytic particles were observed during catalyst stability experiments. Additionally, a comparison between methanol steam reforming (MSR) and APR was also performed. Full article

Hydrogen is a clean-burning fuel with water as its only by-product, yet its widespread adoption is hampered by logistical challenges. Liquid organic hydrogen carriers, such as alcohols from sustainable sources, can be converted to hydrogen through aqueous-phase reforming (APR), a promising technology that bypasses the energy-intensive vaporization of feedstocks. However, the hydrothermal conditions of APR pose significant challenges to catalyst stability, which is crucial for its industrial deployment. This review focuses on the stability of catalysts in APR, particularly in sustaining hydrogen production over extended durations or multiple reaction cycles. Additionally, we explore the potential of ultrasound-assisted APR, where sonolysis enables hydrogen production without external heating. Although the technological readiness of ultrasound-assisted or -induced APR currently trails behind thermal APR, the development of catalysts optimized for ultrasound use may unlock new possibilities in the efficient hydrogen production from alcohols. Full article

The catalytic reforming of bioethanol can produce green hydrogen (H₂) and acetic acid (AcOH). In the present study, the conversion of aqueous ethanol (EtOH) over 4 wt%Ru-4 wt%Sn/TiO₂ in a flow reactor was investigated at different temperatures at 0.1 MPa or at various pressures at 260 °C. The ethanol conversion was rather slow in liquid water, while the reactivity increased significantly when water was evaporated. Under gas-phase conditions at 0.1 MPa, the conversion rate increased with increasing reaction temperature, but the AcOH yield and H₂ purity decreased due to by-production of CH₄, CO, and CO₂. The CH₄ and CO generated by fragmentation of acetaldehyde (AA), an intermediate, were suppressed by increasing reaction pressure, although the formation of CH₄ and CO₂ generated from AcOH was pressure independent. Thus, the highest-pressure conditions in steam at a given reaction temperature are preferred for the production of pure H₂. The initial step, EtOH → AA, was the rate-determining reaction, and the model experiments using AA as a substrate showed that the Cannizzaro reaction of two AA molecules to form EtOH and AcOH occurred preferentially. This oxidation system was confirmed to be effective at EtOH concentrations of up to 500 g/L in water. Full article

The treatment of dairy industry effluents poses a significant challenge from the environmental point of view because of its high organic load. In this work, the aqueous phase reforming of lactose was investigated as a representative model compound for the production of renewable hydrogen. The tests were conducted using two different scenarios: the first one is referred to as direct aqueous phase reforming (APR); the second one proposed a pre-hydrogenation step, followed by APR. The implementation of this reactive pretreatment allowed for minimizing the solid by-product formation with respect to the direct APR, where most of the initial carbon ended up as solid residue. The pre-hydrogenation was investigated in the range of 180–220 °C, using Ru-based catalysts. In the best scenario (using 5% Ru/C), the carbon to solid was reduced by 95%, and up to 70% of the initial carbon was converted into gaseous compounds, hence contributing to the removal of the organic content of the wastewater while producing an energy carrier. Moreover, the hydrogen selectivity increased up to 70% (with respect to 2.5% for direct APR), thanks to hindering homogeneous reaction pathways that do not lead to hydrogen production. Finally, an energetic analysis was conducted to assess the possibility of coupling the APR with the dairy industry and quantifying the percentage of energy which may be produced in situ to satisfy industrial duties. Full article

Hydrogen from biomass, as a promising alternative fuel, is becoming considerably attractive due to its high energy density and clean emissions. The aqueous phase reforming (APR) of biomass-derived oxygenated hydrocarbons and water is a renewable and efficient pathway for hydrogen production and shows great potential. However, the key to the application of this technique is to develop catalysts with high hydrogen productivity. In this work, we first synthesized polyaniline–platinum (PANI-Pt) organo-metallic hybrid precursors and then obtained a high-loaded (~32 wt.% Pt) and highly dispersed (~3 nm Pt particles) Pt@NC−400 catalyst after pyrolysis at 400 °C, and the nanoparticles were embedded in a nitrogen-doped carbon (NC) support. The Pt@NC−400 catalyst showed an almost three times higher hydrogen production rate (1013.4 μmol_H2/g_cat./s) than the commercial 20% Pt/C catalyst (357.3 μmol_H2/g_cat./s) for catalyzing methanol–water reforming at 210 °C. The hydrogen production rate of 1,2-propanediol APR even reached 1766.5 μmol_H2/g_cat./s over the Pt@NC−400 catalyst at 210 °C. In addition, Pt@NC−400 also exhibited better hydrothermal stability than 20% Pt/C. A series of characterizations, including ICP, XRD, TEM, SEM, XPS, N₂ physisorption, and CO chemisorption, were conducted to explore the physiochemical properties of these catalysts and found that Pt@NC−400, although with higher loading than 20% Pt/C (~23 wt.% Pt, ~4.5 nm Pt particle), possessed a smaller particle size, a more uniform particle distribution, a better pore structure, and more Pt metal active sites. This study provides a strategy for preparing high-loaded and highly dispersed nanoparticle catalysts with high hydrogen productivity and sheds light on the design of stable and efficient APR catalysts. Full article

A visible-light-responsive arylazopyrazole-functionalized phenylalanine (4-MeS-AAP-NF) derived ligand was designed and synthesized, and it was found to form metallogels with reversible photo-responsive properties in mixed methanol/water (MeOH/H₂O) solvents. The gelation behavior of the 4-MeS-AAP-NF ligand in the presence of different divalent metal ions in mixed methanol/water (MeOH/H₂O) solvents at pH~11.60 was studied. It was found that the 4-MeS-AAP-NF ligand alone could not self-assemble to form any gels. However, in the presence of divalent metal ions, it readily formed the assembled metallogels in an alkaline aqueous/methanol solution with various morphologies. The results suggest that the gelation process was triggered by divalent metal ions. The presence of the AAP moiety in the gel matrix rendered the metallogel assemblies photo-responsive, and the reversible gel-to-sol phase transition was studied by UV-vis spectroscopy. The gels showed a slow, reversible visible-light-induced gel-to-sol phase transition under blue (λ = 405 nm) and then sol-to-gel transition by green light (λ = 530 nm) irradiation, resulting in the re-formation of the original gel state. The morphology and viscoelastic properties of the yellow–orange opaque metallogels were characterized by scanning electron microscopy (SEM) and rheological measurement, respectively. Full article

Renewable hydrogen production by aqueous phase reforming (APR) over Ni/Al-Ca catalysts was studied using pure or refined crude glycerol as feedstock. The APR was carried out in a fixed bed reactor at 238 °C, 37 absolute bar for 3 h, using a solution of 5 wt.% of glycerol, obtaining gas and liquid products. The catalysts were prepared by the co-precipitation method, calcined at different temperatures, and characterized before and after their use by several techniques (XRD, ICP-OES, H₂-TPR, NH₃-TPD, CO₂-TPD, FESEM, and N₂-physisorption). Increasing the calcination temperature and adding Ca decreased the surface area from 256 to 188 m²/g, and its value after the APR changed depending on the feedstock used. The properties of the acid and basic sites of the catalysts influenced the H₂ yield also depending on the feed used. The Ni crystallite was between 6 and 20 nm. In general, the incorporation of Ca into Ni-based catalysts and the increase of the calcination temperature improved H₂ production, obtaining 188 mg H₂/mol C fed during the APR of refined crude glycerol over Ni/AlCa-675 catalyst, which was calcined at 675 °C. This is a promising result from the point of view of enhancing the economic viability of biodiesel. Full article