H2 Yield Research Articles

Preparation of Ni-B/MgAl2O4 catalysts for hydrogen production via steam reforming of methane

In this paper, a series of B doped Ni/MgAl2O4 catalysts for hydrogen production via steam reforming of methane (SRM) were prepared, and their catalytic activities and stability were evaluated. The characterization of XRD, XPS, TPR, BET, TPO, and TEM revealed that the addition of B could promote Ni dispersion, which lead to the reduce of Ni particle size. 0.5 wt% B was incorporated into Ni/MgAl2O4 would increase Ni particle dispersion rate from 11.2% to 14.8%, which caused Ni particle average size was decreased from 8.78 to 6.96 nm. At the same time, 0.5% B doped would increase the chemisorbed oxygen content of the catalyst, and more oxygen vacancies were formed. Thus, Ni particles sintering and carbon deposition during SRM was suppressed, and the catalytic activity and stability were promoted. Ni-B0.5/MgAl2O4 could achieve 90.2% methane conversion rate and 85% H2 yield under 700 °C with a WHSV of 36,000 mL·(gh)−1 during SRM process, and only a marginal reduction (2%) of methane conversion rate was observed after 48 h reaction. The total carbon content on the used Ni-B0.5/MgAl2O4 catalyst was approximately 0.031 gc∙gcat−1, which was three times lower than that of Ni/MgAl2O4. However, the excess B doping into Ni/MgAl2O4 had a negative effect on the catalytic activity and stability.

MWCNT/Al–Bi–NaCl nanocomposites for enhanced H2 generation

H2 generation through hydrolysis of Al-composites has received eclectic attention for on-demand H2 applications such as low-power proton exchange membrane fuel cells. In this line, we prepared Multi-Walled Carbon Nanotubes (MWCNT)/Al–Bi–NaCl nanocomposites and tested them for enhanced H2 generation. These nanocomposites are prepared using high-energy ball milling followed by uni-axial cold compaction. H2 generation by these nanocomposites was tested using tap water at room temperature. An excellent maximum H2 generation rate of 13.33 mLg−1s−1 with an H2 yield of 98% and an induction time of less than 10 s is achieved. Analysis of different observations shows that adding an optimum percentage of MWCNT to the Al–Bi–NaCl composite results in flaky morphology, which facilitates easily accessible water pathways, enhancing the H2 generation rate of the nanocomposites. Also, an enhanced number of MWCNT/Al–Bi microgalvanic cells, optimum utilization of electrical conductivity of MWCNT, and dissolution of NaCl favored the H2 generation.

Enhanced production of hydrogen-rich gas from municipal sewage sludge gasification using a CaO-RM composite catalyst

Hydrogen-rich gas, characterized by high yield and purity, can be effectively generated through the steam gasification of sewage sludge (SS), offering substantial benefits for organic solid waste treatment and resource conservation. This study evaluated the gasification performance in a horizontal moving-bed reactor employing a wet-mixed CaO-red mud (CaO-RM) composite catalyst. The effects of CaO loading rate (CaO/RM), catalyst-to-SS ratio (CaO-RM/SS), and reaction temperature on the syngas yield, lower heating value (LHV), carbon conversion ratio, H2 to CO (H2/CO) ratio, and H2 yield were investigated. Results indicated that red mud loaded with a calcium-based catalyst significantly enhanced syngas production, particularly for hydrogen generation, during SS gasification. A maximum hydrogen molar fraction of 50.84% and a yield of 7.07 mol/kg were achieved with a CaO/RM of 40% and a CaO-RM/SS of 30% at 750 °C. With the reaction temperature increase from 700 to 900 °C, the catalytic performance for secondary tar cracking and steam reforming was further enhanced. The total syngas yield, H2 yield, hydrogen molar fraction, LHV of syngas, and carbon conversion rate peaked at 0.79 m³/kg, 19.30 mol/kg, 54.41%, 10,249.48 kJ/kg, and 65.67%, respectively, at 900 °C.

A comparative study of membrane reactor and cylindrical reactor using multi-objective optimization for methane reforming process

Multi-objective optimization (MOO) of methane reforming process has been performed for hydrogen and oxygen perm-selective membrane reactor (MR) considering three objectives, namely H2 yield maximization, CO2 minimization and reactor length minimization. The performance of the MR has been compared with that of the cylindrical reactor (CR) using the same objective functions. Four MOO problems have been formulated and solved in this work. Among these, three problems consist of 2-objectives, while one has 3-objectives. Comparative results and discussions of the two reactors are presented based on the multi-objective pareto curve analysis and the trends of decision variables. The results in this work indicate that MR performs better than CR in all the four multi-objective scenarios. We further optimize the reactor with the above mentioned all the three objectives to produce syngas with different (H2/CO) ratios in the product stream. This is especially useful for producing the syngas targeting a specific end application.

Development of nickel-based bimetallic catalysts for production of hydrogen-rich syngas via supercritical water gasification of liquid residue from hydrothermal pretreatment of food waste

Hydrothermal carbonization has become increasingly prevalent in the pretreatment of food waste, leading to the generation of substantial volumes of liquid effluent. This hydrothermal liquid effluent from food waste (HLF) contains high content of organic compounds, making it challenging to treat using conventional methods. In this regard, the HLF was considered a potential source for energy production via supercritical water gasification (SCWG). This study aimed to develop effective bimetallic catalysts based on Ni/Al2O3 with four different promoters (Cu, Co, La, and Ce), and investigated their performance in the catalytic SCWG for the treatment of HLF and hydrogen production. Among the tested promoters, the Ce-Ni catalyst was considered the most suitable in terms of its highest H2 yield and H2 selectivity. The optimal Ce content was found to be 5 wt%, with a catalyst dosage of 5 % by weight of HLF. These conditions resulted in the highest H2 selectivity of 1.61 and a relatively high H2 yield of 749.60 mmol/L under SCWG operating conditions of 480 °C and 30 min. Excessive catalyst dosages increased total syngas yield but reduced H2 selectivity. The stability test demonstrated that the Ce promoter contributed to enhancing the catalyst resistance to deactivation by coke deposition. The hydrogen production of 5Ce-Ni decreased by 13.8 % after three reuses, whereas a larger decrease of 26.0 % was observed with Ni/Al2O3. These findings indicate that Ce-Ni catalyst show promise for enhancing H2-rich syngas production in the SCWG of hydrothermal liquid effluent from food waste.

Microwave-assisted catalytic gasification of mixed plastics and corn stover for low tar, hydrogen-rich syngas production

The challenge for efficient management of post-consumer plastic and biomass waste has grown over the past few decades due to their dramatic increases. In comparison to conventional gasification, microwave-assisted co-gasification of plastics and corn stover offers many benefits, including increased H2 yield and gas components compared to unfavorable char/tar. Nonetheless, for future commercialization of the process and ease of product separation, further reduction of the undesirable tar is necessary, which can be achieved over the catalytic route. In this work, we studied the catalytic effect of magnetite for microwave-assisted co-gasification of corn stover and plastic to make syngas with higher H2 and lower tar selectivity over non-catalytic conditions. A 1:1:1 ratio of plastic-corn stover-magnetite was used to evaluate the reaction parameters such as temperature, space velocity, heating media, and catalytic cycles under gasification conditions. In comparison with the microwave non-catalytic route, a 100% increase in the total H2 yield with 76% higher H2 production efficiency (mmol/kWh) was achieved in the presence of the magnetite catalyst, while reducing the overall tar formation from 9% to 2%. When magnetite was reduced in situ during the reaction, it coupled with microwave and delivered oxygen radicals that cracked down plastic and corn stover intermediates generated from the synergistic effect under microwave heating. Soon after the oxygen transfer process initiated, magnetite reached its final oxidation state consisting of microwave-active Fe and Fe3C phases that continued coupling with microwaves along with the generated graphitic carbon to maintain the heat necessary to further reduce the generated tar and make additional gaseous products, as confirmed by XRD, Raman, and TGA analyses.

Upcycling heteroatoms-containing plastics via bimetallic synergistic catalysis: Unveiling the role of O and Cl in C-H bond cleavage

Given the complicated compositions and hazards of heteroatoms-containing plastics, the efficient upcycling remains a huge challenge. Herein this work proposed an innovative route via dual-stage pyrolysis-catalysis platform to upcycle heteroatoms-containing plastics for high-purity H2 and carbon nanotubes (CNTs) production. Among HY-supported metallic catalysts, bimetallic Fe-Co/HY achieved the maximum H2 yield (41.25 mmol/gplastic) and selectivity (71.76 vol%), alongside the carbon production of 520 mg/gplastic, revealing a catalytically synergistic effect between Fe and Co. Of the plastic individuals/combinations, the plastic combination (PW2) revealed the highest hydrogen efficiency (87.03 %) and H2 efficiency (49.71 %). Regarding the interactions among polyolefins, polyesters, Cl-containing plastics, ternary plastics (PE-PET-PVC) exhibited the higher H2 yield (35.33 mmol/gplastic), hydrogen efficiency (91.40 %), and H2 efficiency (49.14 %) than individual counterparts. The CNTs yield and purity gained from ternary PE-PET-PVC even outperformed these results obtained from individual PE (yield: 326.7 mg/gplasticvs 323.9 mg/gplastic; purity: 93.5 % vs 90.3 %). That was because the chlorinated aryloxy radicals generated from PVC and PET facilitated the cleavage of C (sp3)-H bonds, thereby enhancing the hydrogen extraction and carbon formation. Besides, NiO and NiAl2O4 on the catalyst were converted into NiCl2 by PVC-derived Cl· or HCl, subsequently being reduced into reactive Ni0. Additionally, bimetallic Ni-Fe/HY during CO2-mediated pyrolysis-catalysis displayed the highest H2 yield (55.67 mmol/gplastic), syngas purity (82.39 %), H2 efficiency (62.34 %), and CNTs yield of 367 mg/gplastic, reflecting an apparent synergistically catalytic effect between Ni and Fe. Overall, this study provides a superb solution in heteroatoms-containing plastics upcycling and greenhouse gas emission management.

Sustainable bio-hydrogen production: Assessing economic and environmental implications of a scaled-up industrial bioethanol prototype

This study comprehensively evaluates a bioethanol steam reforming plant in Colombia for green hydrogen (H2) production, sourced from the country's sugar industry. By integrating experimental data and Aspen Plus simulations, the research examines the techno-economic and environmental aspects of utilizing bioethanol as a renewable feedstock for H2 production. Rigorous process modeling, capital investment appraisal, operational cost estimation, economic performance metrics, and environmental assessment are considered. Key findings indicate an H2 yield of 0.155 kg/kg of bioethanol and 34 % energy efficiency, eliminating reliance on fossil fuels. The Levelized Cost of Hydrogen (LCOH) at a Colombian sugar mill is calculated at 10.27 USD/kg under specific assessment conditions. The process exhibits a carbon footprint of 2.16 kgCO2-eq/kgH2 from an environmental perspective. These results emphasize the potential of bioethanol steam reforming as a sustainable and economically viable pathway for green-H2 production, advancing energy transition efforts away from fossil fuels.

Antibiotic fermentation residue for biohydrogen production: Inhibitory mechanisms of the inherent antibiotic

Antibiotic fermentation residue, which is generated from the microbial antibiotic production process, has been a troublesome waste faced by the pharmaceutical industry. Dark fermentation is a potential technology to treat antibiotic fermentation residue in terms of renewable H2 generation and waste management. However, the inherent antibiotic in antibiotic fermentation residue may inhibit its dark fermentation performance, and current understanding on this topic is limited. This investigation examined the impact of the inherent antibiotic on the dark H2 fermentation of Cephalosporin C (CEPC) fermentation residue, and explored the mechanisms from the perspectives of bacterial communities and functional genes. It was found that CEP-C in the antibiotic fermentation residue significantly inhibited the H2 production, with the H2 yield decreasing from 17.2 mL/g-VSadded to 12.5 and 9.6 mL/g-VSadded at CEP-C concentrations of 100 and 200 mg/L, respectively. CEP-C also prolonged the H2-producing lag period. Microbiological analysis indicated that CEP-C remarkably decreased the abundances of high-yielding H2-producing bacteria, as well as downregulated the genes involved in hydrogen generation from the“pyruvate pathway” and“NADH pathway”, essentially leading to the decline of H2 productivity. The present work gains insights into how cephalosporin antibiotics influence the dark H2 fermentation, and provide guidance for mitigating the inhibitory effects.

Catalysis/sorption enhanced pyrolysis-gasification of biomass for H2-rich gas production: Effects of various nickel-based catalysts addition and the combination with calcined dolomite

The effects of addition of various Ni-based catalysts and their combination with calcined dolomite on H2-rich gas production were investigated during catalysis/sorption enhanced pyrolysis-gasification of sawdust. It was found that catalyst support greatly affected the catalytic performance of Ni-based catalysts, the highest H2 concentration and yield was obtained by NiO/SiO2, followed by NiO/γ-Al2O3 and NiO/ZSM-5. Additional active sites on Ni-based catalyst would be formed by introduction of secondary metals onto NiO/γ-Al2O3. Positive synergistic effect between secondary metals and Ni was observed, especially for Mg and Co, resulting in further improved H2 production. Calcined dolomite was further introduced into the process to enhance H2 production, simultaneous catalysis and sorption was found to be better for H2 production than sequential catalysis and sorption. The addition of calcined dolomite could offset the catalytic performance difference for varied Ni-based catalysts due to its catalysis/sorption enhancing effect. Comparatively, bimetallic catalysts were more effective than monometallic catalysts when combined use with calcined dolomite, the H2 concentration was significantly improved despite of the slight changes in H2 yield. Ni-Cu/γ-Al2O3 and Ni-Zn/γ-Al2O3 with good performance on WGS reaction showed better synergistic effect with calcined dolomite, a highest H2 concentration of 87.06 vol.% was achieved by Ni-Cu/γ-Al2O3 catalyst.

Preparation and chemical-looping-gasification performance of waste-sawdust briquette particles

Compared with loose biomass (LB), biomass briquettes (BBs) with high energy density and convenient transportation characteristics are more suitable as solid feedstock for preparing low-tar-content syngas through chemical looping gasification (CLG). Herein, the effects of key briquetting parameters, such as temperature, pressure, moisture content, and particle size, on the briquetting density (ρ), relaxation ratio, and crash resistance of waste sawdust are investigated, and the CLG performance of the briquetted sawdust is examined. Results show that pressure is the most critical factor affecting ρ. Briquetting of waste sawdust promotes the resultant syngas yield in CLG. Compared to LB, BBs exhibit increases in H2 yield, syngas yield, H2/CO molar ratio, and maximum gasification rate. When ρ was 0.8–0.9 g/cm3, the briquetting feature and CLG performance were good, with the briquetting pressure being optimized to 10–15 MPa. Moreover, granular-shaped BBs exhibits the highest CO release strength and good CLG performance. This discovery provides favorable briquetting conditions for the effective application of BBs in the field of CLG.

Synergistic engineering of doped Ni2P-Ni12P5 heterostructure electrocatalysts for urea oxidation reaction

Urea oxidation reaction (UOR) is regarded as a potential approach for industrial hydrogen production to address energy scarcity and water pollution challenges. Fabrication of efficient and stable electrocatalysts is a crucial factor in H2 yield and energy conversion efficiency. Herein, we propose a synergistic engineering route to develop the heteroatom-doped Ni2P-Ni12P5 heterojunction on the porous carbon as the electrocatalyst via the simple solution combustion method. The shift of the diffraction peaks, the change of the lattice spacing, and the difference in the electronic distribution indicate that Cu or Mn heteroatoms are successfully doped into the heterojunction Ni2P-Ni12P5 structure, not only promoting the formation of the Ni3+ but also accelerating the electron transfer. As a result, the doping of Cu and Mn into the Ni2P-Ni12P5 heterojunction obtains high-performance electrocatalysts for the UOR. The Mn doping enhances the catalytic performance of the parent Ni2P-Ni12P5 heterostructure, achieving the potential of 1.319 V at 100 mA∙cm−2 in UOR. Moreover, the Cu-doped Ni2P-Ni12P5 heterojunction catalyst shows a low potential of 1.318 V at 100 mA∙cm−2 and demonstrates exceptional long-term stability under different current densities. Notably, when this catalyst is employed in the two-electrode cell for urea-assisted water electrolysis, the hydrogen production readily occurs at the voltage of 1.47 V for reaching 100 mA∙cm−2, manifesting the electrocatalyst with high activity and stability to be a promising candidate for energy-saving electrolytic hydrogen production on the industrial scale.

Sorption-enhanced chemical looping steam reforming coupled with water splitting for syngas and H2 coproduction using waste plastic as fuel

Chemical looping is a promising technology for hydrogen production. Achieving both high purity and yield is an ongoing challenge, due to low fuel conversion and carbon deposition. In this study, a sorption-enhanced chemical looping reforming coupled with water splitting (SE-CLSR-WS) process was proposed to co-produce syngas and H2 by using waste plastic as the fuel. The Ni-doped Ca2Fe2O5 brownmillerites were designed and employed as oxygen carriers (OCs) and CO2 sorbent. The introduction of Ni leaded to lattice distortion of brownmillerite, thereby enhancing the redox activity of lattice oxygen. In fuel reactor (FR), CaO in-situ captured CO2 and shifted reaction equilibrium towards PET pyrolysis gas reforming, enhancing both syngas yield and PET conversion rates. Adhere to the surface of OCs, CaO improved cyclic performance by inhibiting agglomeration of active metals. Calcination reactor (CR) was set between FR and steam rector (SR) to in-situ desorb CO2 and remove carbon deposition, enhancing hydrogen purity in SR. When Ca2Ni0.75Fe1.25O5-0.25CaO was applied to SE-CLSR-WS process, it exhibited synergistically strengthened performance in reaction activity, sorption capacity and cyclic stability, with a syngas purity of 82.71 % and H2 yield of 8.01 mmol/g OC with 93.26 % purity.

Co-production of porous N-doped biochar and hydrogen-rich gas production from simultaneous pyrolysis-activation-nitrogen doping of biomass: Synergistic mechanism of KOH and NH3

In this study, a method of simultaneous activation and nitrogen doping during biomass fast pyrolysis for co-production of porous N-doped biochar and H2-rich gas production was proposed. The effect of temperature on chemical interaction mechanism of KOH and NH3 was investigated at 500–800 °C. Results showed that KOH and NH3 had a synergistic effect on pore development and nitrogen doping, and the specific surface area and nitrogen content reached maximum values of 2008.37 m2/g and 5.05 wt%, respectively. It may be due to that NH3 entered pores generating by KOH activation for further activation, and at the same time, excessive NH3 could convert new O-containing groups to N-containing groups for more effective nitrogen doping. What's more, the H2 concentration and yield were up to 56.67 vol% and 517.95 mL/g, respectively. It indicates that the synchronization method of fast pyrolysis-activation-nitrogen doping is a promising approach, which is of great significance for the high-value utilization of biomass.

High-Rate and Selective C2H6-to-C2H4 Photodehydrogenation Enabled by Partially Oxidized Pdδ+ Species Anchored on ZnO Nanosheets under Mild Conditions.

Photocatalytic C2H6-to-C2H4 conversion is very promising, yet it remains a long-lasting challenge due to the high C-H bond dissociation energy of 420 kJ mol-1. Herein, partially oxidized Pdδ+ species anchored on ZnO nanosheets are designed to weaken the C-H bond by the electron interaction between Pdδ+ species and H atoms, with efforts to achieve high-rate and selective C2H6-to-C2H4 conversion. X-ray photoelectron spectra, Bader charge calculations, and electronic localization function demonstrate the presence of partially oxidized Pdδ+ sites, while quasi-in situ X-ray photoelectron spectra disclose the Pdδ+ sites initially adopt and then donate the photoexcited electrons for C2H6 dehydrogenation. In situ electron paramagnetic resonance spectra, in situ Fourier transform infrared spectra, and trapping agent experiments verify C2H6 initially converts to CH3CH2OH via ·OH radicals, then dehydroxylates to CH3CH2· and finally to C2H4, accompanied by H2 production. Density-functional theory calculations elucidate that loading Pd site can lengthen the C-H bond of C2H6 from 1.10 to 1.12 Å, which favors the C-H bond breakage, affirmed by a lowered energy barrier of 0.04 eV. As a result, the optimized 5.87% Pd-ZnO nanosheets achieve a high C2H4 yield of 16.32 mmol g-1 with a 94.83% selectivity as well as a H2 yield of 14.49 mmol g-1 from C2H6 dehydrogenation in 4 h, outperforming all the previously reported photocatalysts under similar conditions.

ANN-RSM based multi-parametric optimisation and modelling of H2 and syngas from co-gasification of residues from oil palm plants

Despite their abundance, lignocellulose biomass co-gasification studies especially that of oil palm biomass are scarcely reported. In this study, the frond and trunk of the oil palm tree are co-gasified under different conditions. Experimental results were validated, modelled, and optimised with the aid of RSM and ANN for the syngas and H2 results. The optimum yield of syngas and H2 were found to be 49.01 %, and 23.26 % respectively when operated at 900°C with particle size of 2.6 mm and blending ratio of 1:1. ANOVA yielded satisfactory P-values in the case of RSM with 95 % confidence level. The Bayesian regularisation-based ANN with a 3–10–2 topology (3 inputs, 10 hidden neurons, and 2 outputs) has shown to be a very successful and resilient model, as indicated by its significant coefficient of determination R2 of more than 0.95. The selected ANN structure demonstrates an efficient framework for capturing complicated interactions among the data. The model's relevance is shown by its ability to provide statistically relevant predictions. Furthermore, its endurance under varying situations demonstrates its reliable effectiveness, implying a capacity to generalize effectively to new, existing data. Based on the findings of the suggested BP-based ANN, the proposed model may be used in co-gasification processing industries to make critical evaluations of process operating conditions.

Resistive Heating Catalytic Micro-Reactor for Process Intensified Fuel Reforming to Hydrogen

Abstract Process intensification of fuel reforming using micro-reactors has become crucial for feed flexibility in H2 production for fuel cells. In the literature on microreactors, energy supply for these endothermic reactions has faced limitations, relying on external heating, or autothermal operation. This paper explores a novel approach using a thin-film catalytic heater to develop micro-reactors. The study focuses on dry methane reforming in a simplified micro-reactor where thermal energy is supplied through electric resistive heating of a thin carbon sheet with a catalyst applied to its surface. The thin catalytic heated layer inside the reactor minimizes energy losses and the reactor footprint. Power input was varied from 90-225 W to understand its impact on the reactor temperature, CH4 conversion, H2 and CO yields. Fast thermal response times were achieved using the carbon paper as thin film for heating. Ni/MgO impregnated onto carbon paper was utilized as the catalytic heating element which resulted in CH4 conversions greater than 60% at temperature above750 K. Influence of operating conditions such as the input molar ratio of CO2/CH4, and gas hourly space velocity (GHSV) were also investigated to understand the scope of the catalyst in this setup. High GHSVs (592,885 and 948,617 mL/(hr.gcatalyst)) were tested to understand the throughput achievable using this setup. This approach demonstrates improved scope and feasibility for further intensification compared to conventionally heated microreactors. The research paves the way for efficient and compact micro-reactors for fuel reforming processes.

Fabrication and catalytic assessment of Ni/Ce–Zr–O catalyst for enhanced hydrogen production via steam reforming of glycerol

The valorization of glycerol, a plentiful byproduct derived from the biodiesel industry, for green hydrogen production via steam reforming (GSR) has attracted considerable attention. Nevertheless, catalysts developed for GSR encounter critical obstacles related to thermal stability and coke deposition during prolonged operations. In this study, we strategically employed thermally stable ZrO2 as a support along with redox-active Ce as a promoter for Ni to optimize both the preparation method and constituent content of the Ce-promoted Ni/ZrO2 catalyst for GSR. The physicochemical properties of both fresh and GSR-used catalysts were investigated using a range of characterization techniques, including XRD, H2-TPR, SEM-EDS/TEM, N2 adsorption/desorption, and TGA. The results demonstrate that the sol-gel method yields a Ni/Ce–Zr–O catalyst with smaller Ni crystals and a higher surface nickel content compared to the step impregnation and co-precipitation methods, thereby achieving enhanced catalytic activity. Moreover, the catalyst prepared by the sol-gel method exhibited excellent activity stability at elevated feedstock concentrations. Furthermore, it has been determined that there is an optimized amount of Ce doping for the Ni/ZrO2 catalyst, which allows the catalyst to achieve the highest pore parameters and surface nickel content. Among the studied catalysts, the one containing 30/50 wt% of designed CeO2/ZrO2 achieved the highest and most stable H2 yield (4.32 mol⋅mol−1) and carbon gasification efficiency (70.28 %) during a 24-h's GSR with a feedstock concentration of 15 wt% at 500 °C (with a WHSV of 45 h−1). Importantly, this optimized Ni/Ce–Zr–O catalyst effectively eliminates the deposition of filamentous/crystallized coke during long-term GSR operation due to enhanced oxygen vacancies created by the formed CexZr1-xO2 species, making it highly promising for large-scale applications.

New insights on waste mixing for enhanced fermentative hydrogen production

Co-fermentation can differently impact H2 production, with positive or negative interactions observed. Positive interactions were usually attributed to a balanced composition and improved buffer capacity. However, the impact of co-fermentation on microbial communities (H2-producing and H2-consuming bacteria) remains unexplored. This work aimed to deepen the interaction mechanisms observed in co-fermentation targeting microbial communities with an innovative focus on H2-consuming bacteria (homoacetogens). The H2 production of seven mixtures (food waste fractions and rye silage) and individual performances were compared by Biochemical Hydrogen Potential (BHP). Final microbial communities were characterized by sequencing and qPCR. A positive correlation between H2 yield and Soluble and Easily Extractible Sugars (SEES) content was observed for all the substrates (R² = 0.79), confirming this correlation not only for individual substrates but also mixtures. Positive interactions were observed for most of the mixtures, with a H2 yield significantly higher (16–37 %) than expected. The faster H2 production observed in mixtures (2.6 times faster) was correlated to the selection of Clostridiaceae_1 family (final relative abundance of 90–98 %) and decline of homoacetogens. It is therefore essential to further understand the microbial communities’ dynamics in co-fermentation to develop efficient fermentation systems.

Enhancement of selective monoaromatic hydrocarbon and syngas products from fast pyrolysis of cassava stalks over Co, Mo promoted Ni catalysts

Catalytic fast pyrolysis of cassava stalks has been intriguing as a promising, feasible chemical refinery method in terms of waste-to-energy conversion from cassava cultivation. This study aims to determine the synergetic influence of Mo and Co on Ni catalysts (Ni, Ni–Mo, and Ni–Co) prepared via ultrasonic-assisted incipient wetness impregnation method for catalytic pyrolysis vapor upgrading. The results indicated that Co and Mo enhance the reducibility of NiO and promote weak-to-medium acidity, thereby enhancing Ni's performance. Mono-Ni favors cracking deoxygenation, whereas oxophilicity promoters particularly enhance the oxygen absorbability efficiency to selective deoxygenated production. A fine Ni dispersion on CoNi/SiO2 catalyst was observed to positively affect the production of monoaromatic hydrocarbons (46.10 %), in contrast to those without promoters (21.63 %). This is attributed to an optimal Ni-metallic distribution with a small crystal size of 7.01 nm and a high surface area of 342.6 m2 g−1, highlighting the effectiveness of the promoter-assisted Ni catalyst. Additionally, a high yield of H2 (66.9 %) in non-condensable gas was recorded at 550 °C. The study suggests that a simplified approach to developing Ni-based catalysts could enhance the eco-friendliness of commercial catalysts, thereby facilitating the scale-up of biomass pyrolysis applications.