Terms Of Hydrogen Yield Research Articles

A thermodynamic comparison of membrane-assisted processes for hydrogen production with integrated CO2 capture

The energy efficiency of two novel process designs for the production of ultra-pure hydrogen with simultaneous capture of CO2 using CH4 as the feedstock, namely membrane-assisted chemical looping reforming (MA-CLR) and membrane-assisted sorption-enhanced reforming (MA-SER) has been compared. The modelling of the integrated network for mass and heat balances has been carried out using the ASPEN® Plus V10 process simulation tool to quantify the benefits and disadvantages of integrating hydrogen perm-selective membranes with either chemical looping or sorption-enhanced reforming. The evaluation of the MA-CLR process is carried out for a range of the following operating conditions: 10 < pR < 60 bar, 500 < TR < 900°C, and 1.5 < H2O/CH4 < 3.0. On the other hand, for the MA-SER process the operation ranges of 1.0 < pR < 10 bar, 400 < TR < 900°C, and 2.5 < H2O/CH4 < 4.0 were considered. Within the operation window of the MA-SER process, no carbon formation is observed, as any carbon present in the system reacts with CaO in the form of CO2. However, in the case of the MA-CLR process, carbon formation can occur during the pre-reforming stage, particularly at low H2O/CH4 ratios. In terms of hydrogen yield, energy utilization and carbon capture, the MA-CLR outperforms the MA-SER plant. However, the MA-SER plant offers certain advantages over the MA-CLR system, such as a pure CO2 product stream and lower reactor design temperatures. In the MA-CLR system, a carbon capture rate of 99.8% and a hydrogen product yield of 74.4% are achieved, whereas the MA-SER plant achieves a carbon capture rate of 98.5% and a hydrogen product yield of 69.7%.

Biomass to H2: Evaluation of the Impact of PV and TES Power Supply on the Performance of an Integrated Bio-Thermo-Chemical Upgrading Process for Wet Residual Biomass

The last Intergovernmental Panel on Climate Change (IPPC) assessment report highlighted how actions to reduce CO2 emissions have not been effective so far to achieve the 1.5 C limit and that radical measures are required. Solutions such as the upgrading of waste biomass, the power-to-X paradigm, and an innovative energy carrier such as hydrogen can make an effective contribution to the transition toward a low-carbon energy system. In this context, the aim of this study is to improve the hydrogen production process from wet residual biomass by examining the advantages of an innovative integration of anaerobic digestion with thermochemical transformation processes. Furthermore, this solution is integrated into a hybrid power supply composed of an electric grid and a photovoltaic plant (PV), supported by a thermal energy storage (TES) system. Both the performance of the plant and its input energy demand—splitting the power request between the photovoltaic system and the national grid—are carefully assessed by a Simulink/Simscape model. The preliminary evaluation shows that the plant has good performance in terms of hydrogen yields, reaching 5.37% kgH2/kgbiomass, which is significantly higher than the typical value of a single process (approximately 3%). This finding demonstrates a good synergy between the biological and thermochemical biomass valorization routes. Moreover, thermal energy storage significantly improves the conversion plant’s independence, almost halving the energy demand from the grid.

Utilization of PET (waste) via hydrothermal co–gasification with sorghum for hydrogen rich gas production

In this study, the applicability of hydrothermal biomass co–gasification for utilizing polyethylene terephthalate (PET) based waste was investigated. For this purpose, hydrogen rich gas production was realised by hydrothermal co–gasification of sorghum biomass with virgin and waste PET mixtures at 500 °C, and the gasification performances were compared. The feedstock/water ratio (%, w/v) was significantly effective on the gasification process in terms of gas yields, gas, and liquid product distributions. Synergistic effects were observed in hydrogen formation in co–gasification of PET and sorghum. The amount of hydrogen obtained from the co–gasification of PET and sorghum was 4.0 mol H2/kg feed higher than the sum of total amount of hydrogen obtained from the individual gasification of PET and sorghum. GC/MS analysis showed that liquid contents were also affected from experimental conditions. The use of catalysts increased the gasification and carbon conversion yields regardless of the type. Although KOH was the most effective single catalyst on hydrogen yield, the catalyst combinations were more effective with promoted activities in terms of hydrogen yields and CO2 capture. Hydrogen yield, which was 12.9 mol H2/kg feed without catalyst, increased to 31.0 (±0.9) mol H2/kg in the presence of K2CO3/CaO catalyst combination for virgin PET/sorghum mixtures and 28.1 (±0.3) mol for PET waste plastics/sorghum mixtures. For the PET waste plastics/sorghum mixtures with the binary catalyst combinations (K2CO3/CaO and KOH/CaO), the CO2 mole fractions of the product gas mixtures were below 1% and the hydrogen contents of the obtained gas mixtures were above 90%. The results of the study show that pet–based plastic wastes can be effectively utilized to produce hydrogen rich gas, by co–gasification with biomass.

Impact of Cr doping on the performance of Ni/Al2O3 catalyst through methane decomposition into COx-free hydrogen and carbon nanomaterials

The co-production of clean hydrogen and nanostructured carbon materials via methane decomposition is a desirable alternative route for energy savings and environmental considerations. In the current study, Al2O3 supported monometallic 50%Ni and bimetallic 40%Ni-10%Cr catalysts were prepared and evaluated for this reaction. The as-prepared catalysts were characterized by X-ray diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), and N2 physisorption, and Raman spectroscopy. Meanwhile, the spent catalysts were characterized by XDR, SEM, and Raman spectroscopy. According to XRD, TPR, and SEM results, the incorporation of Cr2O3 into the Ni/Al2O3 catalyst improved metal dispersion and reduction behavior compared to the un-promoted catalyst. As a result, the Ni-Cr/Al2O3 catalyst exhibited exceptional activity in terms of hydrogen yield throughout the whole reaction periods. Furthermore, the Cr2O3 inclusion enhanced catalyst stability by preventing the aggregation of active metal sites during the decomposition process. In contrast, the presence of agglomerated NiO particles on the surface of the Al2O3 support was the primary cause of deteriorating the activity of Ni/Al2O3 catalyst over a long reaction period. Both catalysts produced 79 % hydrogen at the start of the reaction (10 min), but by the end of the reaction (180 min), the hydrogen yield was 57 % and 76 % for Ni/Al2O3 and Ni-Cr/Al2O3 catalysts, respectively. In addition, the addition of Cr2O3 raised the accumulated carbon yield from 9.2 to 13.5 gC/gNi for both catalysts, respectively. SEM images showed that thin carbon nanotubes were deposited on the Ni-Cr/Al2O3 catalyst, whereas large-diameter carbon nanotubes were grown on the Ni/Al2O3 catalyst.

Variation of the Number of Heat Sources in Methane Dry Reforming: A Computational Fluid Dynamics Study

To overcome the weak point of the gas type heating (failure in heating uniformly and persistently), liquid type molten salt as a concentration of solar energy was considered as a heat source for dry reforming. This high-temperature molten salt flowing through the center of the tubular reactor supplies necessary heat. The dependence on the number of heat source of the hydrogen production was investigated under the assumption of the fixed volume of the catalyst bed. By changing these numbers, we numerically investigated the methane conversion and hydrogen flow rate to find the best performance. The results showed that the methane conversion performance and hydrogen flow rate improved in proportion to the number of heating tubes. For the one heat source, the reactor surrounded by a heat source rather than that located in the center is the best in terms of hydrogen yield. In addition, this study considered the case in which the system is divided into several smaller reactors of equal sizes and a constant amount of catalyst. In these reactors, we saw that the methane conversion and hydrogen flow rate were reduced. The results indicate that the installation of as many heating tubes as possible is preferable.

Improving sustainable hydrogen production from green waste: [FeFe]-hydrogenases quantitative gene expression RT-qPCR analysis in presence of autochthonous consortia

BackgroundBio-hydrogen production via dark fermentation of low-value waste is a potent and simple mean of recovering energy, maximising the harvesting of reducing equivalents to produce the cleanest fuel amongst renewables. Following several position papers from companies and public bodies, the hydrogen economy is regaining interest, especially in combination with circular economy and the environmental benefits of short local supply chains, aiming at zero net emission of greenhouse gases (GHG). The biomasses attracting the largest interest are agricultural and urban green wastes (pruning of trees, collected leaves, grass clippings from public parks and boulevards), which are usually employed in compost production, with some concerns over the GHG emission during the process. Here, an alternative application of green wastes, low-value compost and intermediate products (partially composted but unsuitable for completing the process) is studied, pointing at the autochthonous microbial consortium as an already selected source of implementation for biomass degradation and hydrogen production. The biocatalysts investigated as mainly relevant for hydrogen production were the [FeFe]-hydrogenases expressed in Clostridia, given their very high turnover rates.ResultsBio-hydrogen accumulation was related to the modulation of gene expression of multiple [FeFe]-hydrogenases from two strains (Clostridium beijerinckii AM2 and Clostridium tyrobutyricum AM6) isolated from the same waste. Reverse Transcriptase quantitative PCR (RT-qPCR) was applied over a period of 288 h and the RT-qPCR results showed that C. beijerinckii AM2 prevailed over C. tyrobutyricum AM6 and a high expression modulation of the 6 different [FeFe]-hydrogenase genes of C. beijerinckii in the first 23 h was observed, sustaining cumulative hydrogen production of 0.6 to 1.2 ml H2/g VS (volatile solids). These results are promising in terms of hydrogen yields, given that no pre-treatment was applied, and suggested a complex cellular regulation, linking the performance of dark fermentation with key functional genes involved in bio-H2 production in presence of the autochthonous consortium, with different roles, time, and mode of expression of the involved hydrogenases.ConclusionsAn applicative outcome of the hydrogenases genes quantitative expression analysis can be foreseen in optimising (on the basis of the acquired functional data) hydrogen production from a nutrient-poor green waste and/or low added value compost, in a perspective of circular bioeconomy.

Biomass pyrolysis coupled with non-thermal plasma/catalysis for hydrogen production: Influence of biomass components and catalyst properties

A novel two-stage pyrolysis-plasma/catalysis process has been developed for hydrogen production from waste biomass. Investigation into; the comparison of the biopolymers, cellulose and lignin; the effect of Mg, Co, Ce, Cu, Fe and Ni as promoter metals added to a Ni-Al2O3 catalyst; and the influence of the catalyst support material in relation to hydrogen production was carried out. The combination of plasma and catalysis produced the highest hydrogen and total gas yield from processing waste biomass in comparison to non-plasma pyrolysis-catalysis. The pyrolysis-plasma/catalysis of cellulose produced 4.07 mmol g−1biomass of hydrogen compared with lignin which produced 4.29 mmol g−1biomass of hydrogen. Metal promoters with the Ni-alumina catalyst did not have a strong influence on hydrogen production. However, some catalysts (Cu-Ni-Al2O3 and Ni-Ni-Al2O3), showed that addition of the metal promoter resulted in a reduced yield of hydrogen. The order of the catalysts in terms of hydrogen yield (H2 mmol g−1biomass) was, Ce-Ni > Co-Ni > Mg-Ni > Fe-Ni > Ni-Ni > Cu-Ni. In addition, different catalyst support materials were investigated. Hydrogen yield was highest with alumina support material compared with titanium oxide and Y-zeolite supports. Hydrogen production was linked to the surface area and porosity, and the dielectric constant of the catalyst material.

Recent Developments in Microbial Electrolysis Cell-Based Biohydrogen Production Utilizing Wastewater as a Feedstock

Carbon constraints, as well as the growing hazard of greenhouse gas emissions, have accelerated research into all possible renewable energy and fuel sources. Microbial electrolysis cells (MECs), a novel technology able to convert soluble organic matter into energy such as hydrogen gas, represent the most recent breakthrough. While research into energy recovery from wastewater using microbial electrolysis cells is fascinating and a carbon-neutral technology that is still mostly limited to lab-scale applications, much more work on improving the function of microbial electrolysis cells would be required to expand their use in many of these applications. The present limiting issues for effective scaling up of the manufacturing process include the high manufacturing costs of microbial electrolysis cells, their high internal resistance and methanogenesis, and membrane/cathode biofouling. This paper examines the evolution of microbial electrolysis cell technology in terms of hydrogen yield, operational aspects that impact total hydrogen output in optimization studies, and important information on the efficiency of the processes. Moreover, life-cycle assessment of MEC technology in comparison to other technologies has been discussed. According to the results, MEC is at technology readiness level (TRL) 5, which means that it is ready for industrial development, and, according to the techno-economics, it may be commercialized soon due to its carbon-neutral qualities.

Simulation of a Natural Gas Steam Reforming Plant for Hydrogen Production Optimization

AbstractA simulation study to predict and optimize a natural gas steam reforming plant in Suez was performed. The developed model was used to generate performance data that would map the relation between atthe operating variables and hydrogen productivity. A single objective optimization problem was then formulated to maximize hydrogen production in the subunits: hydrocarbon prereformer, steam methane reformer, and the medium‐temperature water‐gas‐shift reactor. The process temperature and pressure for the three subunits, total plant flow rate and total superheated steam flow rate were selected as decision variables. A good agreement was found between simulation results and plant data at steady‐state conditions in terms of hydrogen yield and chemical composition. The developed mathematical model for hydrogen productivity correctly predicts the effect of relevant process parameters.

Performance Assessment Study on the Na‐O‐H Thermochemical Water Splitting Cycle for Hydrogen Generation

AbstractThe sodium‐oxygen‐hydrogen (Na‐O‐H) thermochemical cycle is investigated, as one of the potential methods of thermochemical water decomposition and hydrogen generation. The hydrogen production reaction, metal separation reaction, and hydrolysis reaction, forming the Na‐O‐H thermochemical cycle, are examined by RGibbs reactor modeling. The parameters for the three reactions are optimized in terms of hydrogen yield, pressure, temperature, and heat requirement. The metal separation reaction is carried out under vacuum pressure, while other reactions can be conducted under atmospheric pressure.

Continuous dark and photo biohydrogen production in a baffled bioreactor and electrons distribution analysis

This work studied the sequential hydrogen production by dark and photo-fermentation (HPDPF) in continuous baffled bioreactors. Taken enzymatic hydrolysate of corn stover as initial carbon source, the influence of hydraulic retention time (HRT) of dark fermentation (DF) and the dilution ratio (DR) of dark fermentation effluents (DFEs) on the hydrogen production performance of the combined fermentation system and electron distribution were investigated. For DF unit, the highest hydrogen production rate (HPR) of 5.24 L/(L·d) was detected at HRT of 18 h, however, the maximum HPR of 4.60 L/(L·d) was obtained from DFEs with HRT of 12 h and DR of 1:0.5 during photo fermentation unit, meanwhile, the electrons in substrate partitioning to H2 reached the maximum value of 35.69%. In terms of hydrogen yield, the optimum operating conditions of the combined system were HRT of 12 h (DF) and DR of 1:0.5(DFEs), in which the hydrogen yield reached 12.73 L/d.

Effect of La promotion on Ni/Mg-Al hydrotalcite derived catalysts for glycerol steam reforming

Abstract The influence of lanthanum promotion on the physico-chemical properties and catalytic activity of Ni/Mg-Al catalysts in the glycerol steam reforming (GSR) reaction was studied. An Mg-Al and different Mg-Al-La supports with various molar ratios were synthesized using a co-precipitation technique. The calcined supports were then impregnated with 5 wt% Ni. After calcination at 600 °C, physico-chemical properties of the Ni-based catalysts were investigated by XRD, BET, H2-TPR, and CO2-TPD techniques. H2-TPR analyses showed that the quantity of lanthanum in the support composition influenced the reducibility of Ni species as well as their dispersion. CO2-TPD analyses showed that lanthanum addition improved catalyst basicity. The activity of all catalysts in the GSR reaction was tested (T = 400−700 °C, water/glycerol feed ratio 9:1, flow rate of 0.025 mL/min). The composition of the Ni/MAL0.4 (Ni/Mg6Al1.6La0.4; subscripted numbers indicate the molar ratio of each metal) catalyst provided a good metal-support interaction and Ni dispersion which translated to an overall superior performance in terms of hydrogen yields, glycerol conversion to gaseous products, and total glycerol conversions. TG-DSC analyses of the spent catalysts showed that the lanthanum quantity also influenced the quantity of coke deposition. The formation of encapsulating coke over all catalysts was linked to high concentrations of dehydration products observed in liquid product analysis. A stability test conducted at 600 °C for Ni/MAL0.4 revealed its deactivation due to encapsulating coke formation which resulted in active metal site blockage. With a reduced flow rate (0.008 mL/min), a different coke formation mechanism allowed the catalyst to last for 24 h.

Methanol steam reforming for hydrogen generation: A comparative modeling study between silica and Pd-based membrane reactors by CFD method

Pd-based membranes are the most studied in applications of membrane reactors in the field of high grade hydrogen production. The main issues of Pd-membranes such as high cost and relatively low hydrogen permeability limit their wide development at larger scale, favoring other inorganic materials such as silica to be used as membrane for hydrogen generation/purification. Therefore, this theoretical study aims to evaluate the performance of silica (4 mm of thickness and 5 cm of active length) and PdAg (50 μm thick and 5 cm of active length) membrane reactors exercised at the same operating conditions and using the same reaction kinetics to produce hydrogen from methanol steam reforming reaction. Furthermore, an equivalent traditional reactor is studied for comparison. A computational fluid dynamics model was developed, firstly validating the former with experimental literature data. The effects of reaction pressure and temperature on the reactors performance in terms of hydrogen yield, methanol conversion and CO selectivity were hence studied and discussed. The simulations via CFD method indicated that the silica membrane reactor results to be the best solution over the PdAg MR and the TR as well, presenting the best simulation results at 513 K, 10 bar, sweep-factor = 6, GHSV = 6000 h−1 and feed molar ratio = 3/1 with CO selectivity equal to 0.04%, methanol conversion and hydrogen yield >90%.

Identification of a novel hydrogen producing bacteria from sugarcane bagasse waste

Abstract A new hydrogen producing strain with potent cellulose degrading ability was isolated from soil sample collected from sugarcane bagasse (SCB) storage yard. Among the colonies screened, the newly identified strain, Bacillus subtilis AuChE413 has shown better performance in terms of hydrogen yield and cellulose degradation. Morphological, physiological, and biochemical traits of the isolated strain were studied. And its molecular characterization was studied by analyzing the sequence of 16S rRNA gene. The sequence of Bacillus subtilis AuChE413 was compared with other GenBank sequences using BLASTn to study its homology with other species. Phylogenetic tree was constructed using the neighbor joining method. The hydrogen production capacity of Bacillus subtilis AUChE413 was tested by employing the pretreated SCB and sweet sorghum stalk biomass (SSB) as substrates. In comparison, the substrate sorghum stalk has produced the highest hydrogen yield of 55.2 l H2 /kg SSB at pH 7 and 37 °C.

Revealing the impact of hydrogen production-consumption loop against efficient hydrogen recovery in single chamber microbial electrolysis cells (MECs)

Microbial electrolysis for hydrogen production exhibited great advantages over many other biohydrogen production techniques in terms of hydrogen yield (HY) and energy efficiency (EE). With the elimination of methanogens, homoacetogens could thrive as the major hydrogen sink to impair HY and EE. However, the determination of hydrogen loss in microbial electrolysis cells (MECs) was rather controversial. In this study, we quantitatively investigated the negative impact of homoacetogens on hydrogen recovery in single chamber MECs. Hydrogen partial pressure (HPP) ranging from 0 to 40 kPa greatly affected the hydrogen consumption rate while acetate concentration ranging from 0 to 100 mM had little impact. HY base on consumed substrate was not significantly affected with less than 20 kPa HPP but decreased from 87% to 66% with 20–34 kPa HPP. And the EE based on input electricity was decreased from 160% to 48% accompanied with the increase of HPP from 7 to 34 kPa. Microbial community analysis revealed that Acetobacterium was the dominant homoacetogenic hydrogen scavenger in cathodic biofilm and planktonic cells in the single chamber MECs.

Renewable Hydrogen from Ethanol Reforming over CeO2-SiO2 Based Catalysts

In this research, a bimetallic Pt-Ni/CeO2-SiO2 catalyst, synthetized via wet impregnation, was successfully employed for the oxidative steam reforming of ethanol between 300 and 600 °C. The reaction performance of the Pt-Ni catalyst was investigated and compared with the Ni/CeO2-SiO2, Pt/CeO2-SiO2 as well as CeO2-SiO2 sample. The bimetallic catalyst displayed the best results in terms of hydrogen yield and by-products selectivity, thus highlighting the crucial role of active species (Pt and Ni) in promoting ethanol conversion and reaching the products distribution predicted by thermodynamics. The most promising sample, tested at 500 °C for more than 120 h, assured total conversion and no apparent deactivation, demonstrating the stability of the selected formulation. By changing contact time, the dependence of carbon formation rate on space velocity was also investigated.

Parallel plates reactor simulation: Ethanol steam reforming thermally coupled with ethanol combustion

This work presents a theoretical study on the thermal coupling of ethanol steam reforming with ethanol combustion in a parallel plates reactor. A one-dimensional, heterogeneous, mathematical model is used and the effects of the main operative and constructive variables on the performance of the system are analyzed. Thermal coupling between combustion and reforming of ethanol is plausible and an adequate behavior of the reactor in terms of hydrogen yield and conversion of ethanol is predicted. The importance of distributing the source of heat is evidenced since high molar fractions of ethanol in the combustion stream can lead to excessive hot spots.

Dark bio-hydrogen fermentation by an immobilized mixed culture of Bacillus cereus and Brevumdimonas naejangsanensis

Based on the immobilized mixed culture technology, both the hydrogen production and synergy mechanism between Bacillus cereus A1 and Brevumdimonas naejangsanensis B1 were investigated. Different immobilization carriers were chosen. In terms of hydrogen yield and the multi-cycle use of the carriers in batch fermentation, corn stalk as carrier was found to be a better candidate than fiber material (polyester fiber) and activated carbon (AC). The obtained cumulative hydrogen production was 2205 mL/L within 180 h, significantly higher than that of the suspended fermentation. The average cumulative hydrogen production and hydrogen yield were 1845 mL/L and 1.50 mol H2/mol glucose for ten cycles of repeated fermentation batches respectively, which was 62.5% higher than that of suspended fermentation. The experimental results also showed that the system could use starch as direct substrate and the tolerance of the immobilized system to the substrate loading was improved. The activities of amylase and hexokinase were respectively 2 to 3 and 2 times higher than in the suspended fermentation due to the synergistic effect of co-immobilization compared with the suspended fermentation.

Hydrogen production from hydrocarbons over Rh supported on Ce-based oxides for automotive applications

On-board hydrogen production by reforming of fuel in the exhaust gas recirculation loop allows increasing the engine yield, thus decreasing the fuel consumption, and the formation of pollutants such as NOx. Various catalysts based on Rh supported on cerium-based oxides with alumina were prepared and characterized. Their catalytic performances were evaluated in the reforming of isooctane, chosen as model molecule, in the presence of a gas mixture of composition representative of the exhaust gas, i.e. H2O, CO2, O2 and N2. It was shown that the best performances in terms of hydrogen yield were obtained with the supports containing both ceria, in high amounts, and alumina, due to the high thermal stability of the support, the high metal dispersion and the limited sintering.

Activity of Copper and Nickel Loaded on HZSM-5Zeolite Based Catalyst for Steam Reforming of Glycerol to Hydrogen

The study focuses on hydrogen production via glycerol steam reforming over copper and nickel loaded on HZSM-5 zeolite based catalyst. The catalysts were prepared by using different loading amount of copper (0-10wt%) and nickel (0-10wt%) on HZSM-5 zeolite catalysts through wet impregnation method and was characterized by X-Ray Diffraction (XRD). The performances of catalysts were evaluated in terms of glycerol conversion and hydrogen production at 500°C using 6:1 of water to glycerol molar ratio (WGMR) in a tubular fixed bed reactor. All the catalysts had achieved more than 85% of glycerol conversion except that of 5%Cu loaded on HZSM-5 catalyst. The addition of nickel into 5% Cu/HZSM-5 catalyst had increased the hydrogen yield. Similar trend was observed when copper was added into Ni/HZSM-5 catalyst but using copper loaded on HZSM-5 alone was unable to produce hydrogen compared to using nickel catalyst alone. It showed that copper acted as a promoter for hydrogen production. It was established that a 5wt% of Cu with 10wt% of Ni loaded on HZSM-5 catalyst showed significant improvement in terms of hydrogen yield and gaseous product compositions at selected operating conditions.