Highest H2 Yield Research Articles

Hydrogen production from oilfield wastewater by gasification in supercritical water with a continuous system

Multi-component supercritical thermal fluid (MCSCTF) generated based on supercritical water gasification (SCWG) technology can significantly enhance heavy oil recovery. In this paper, the performance of oilfield wastewater SCWG was systematically investigated with a continuous system. Thermodynamic analysis showed that total gasification of oilfield wastewater in supercritical water (SCW) was feasible due to the inhibition of coke generation. The addition of Na2CO3 or K2CO3 can facilitate steam reforming and water–gas shift reactions to achieve high H2 yields and carbon gasification efficiency (CE). The generation of the abundant gas was attributed to the rapid decomposition of the liquid products by free radical reactions at high temperatures. As the feedstock concentration increased, the oil–water emulsion structure may favor the intense pyrolysis reaction over the steam reforming reaction resulting in lower CE. The suitable ratio of emulsion to preheat water flow (1:5) can increase the heating rate of the feedstock and ensure the decomposition time of the intermediate products to obtain high CE (96%). The trends in the change of gas products at different operating parameters were supported by thermodynamic calculations. This work can provide the basis for the subsequent coupled hydrogen oxidation technology to generate MCSCTF.

Study of the impregnation sequence of active phase and effect of cobalt content over Co-CeO2/MgΑl2O4 catalysts in ethanol steam reforming

Co–CeO2/MgAl2O4 catalysts were obtained by varying the impregnation order (sequential or co‒impregnation) of active phase (Co) and Ce and were evaluated in the ethanol steam reforming (ESR) reaction. Results from TPR and XPS revealed that the impregnation order influenced the metal‒metal and/or metal‒support interactions and Co0/Con+, Ce3+/Ce4+ and the Co/Ce surface molar ratio, affecting the catalyst behavior in the ESR reaction. The solids prepared by sequential impregnation, Co/Ce/S and Ce/Co/S exhibited a greater degree of reduction than the solid obtained by co‒impregnation (CoCe/S), though these systems displayed low dispersion of Co species and low content of surface Co°. The solid CoCe/S showed the highest dispersion (68.5%) and greater presence of Co0 on the surface. The effect of the cobalt content (4, 8 and 12 wt%) was also examined in catalysts prepared using the co‒impregnation method. With the increase in cobalt content, a greater loss of stability and a greater amount of carbon deposits were observed. The highest H2 yield (5.3 mol H2/mol C2H5OH) and stability were achieved over the solid obtained by co‒impregnation with 8 wt% Co, which was attributed to the high dispersion of the active phase and its high content of surface metallic cobalt.

Ruthenium-Catalyzed Transformation of Ethylene Glycol for Selective Hydrogen Gas Production in Water

We developed an efficient process for producing hydrogen gas from aqueous ethylene glycol (EG) at 90–160 °C over a ruthenium catalyst. We achieved a high yield of hydrogen gas (up to 3.0 n(H2)/n(EG)) and formic acid (85% yield) from ethylene glycol in aqueous alkaline medium at 110 °C, where the role of reaction temperature and base concentration was found to be critical in achieving a high yield of H2. The chemical and morphological properties of the synthesized ruthenium catalyst were established using P-XRD, TEM, XPS, and other techniques. Advantageously, the ruthenium catalyst exhibited appreciably high long-term stability for over 70 h, generating ca. 290 L of H2 per gram of Ru with a yield of 1035 L of H2 per L of ethylene glycol.

The Realization of complete carbon conversion and hydrogen purification in the coal-fueled chemical looping technology using a cost-effective iron-based oxygen carrier

The development of cost-effective and reactive oxygen carriers and the fast and complete conversion of solid fuels are two critical issues in the solid fuel chemical looping technology. Red mud, a solid waste from the alumina industry, was found to be an economic oxygen carrier candidate simultaneously realizing the use of solid wastes and the CO2 abatement after comparing with other two different iron-based materials (pure Fe2O3 and hematite). This study validated red mud as an excellent oxygen carrier to achieve the almost complete conversion of char in solid fuels (SFs) (99.4%) and meanwhile the hydrogen production with high-purity (97% H2 purity) and higher H2 yield (around 500 mL/g), in the optimized pyrolysis procedure of solid fuels with proper gasification agent and rationalized reaction temperatures (1000 °C) and residence time (10mins). Characterizations of red mud using SEM-EDS and XRD revealed that the unique microscopic crystalline structures of both Fe2O3 and Ca2Al2SiO7 particles nested on Na4Al2Si2O9 molten substrate, implying that the existence of Na-containing component of the red mud OC likely accounts for its higher reactivity and stability in multiple redox cycles.

Integration of catalytic methane oxy-reforming and water gas shift membrane reactor for intensified pure hydrogen production and methanation suppression over Ce0.5Zr0.5O2 based catalysts

The production of pure hydrogen from methane or biomethane is a multistep process that can be intensified by the use of membrane reactors. In this study we have synthetized by microemulsion technique Rh and Pt supported over Ce0.5Zr0.5O2 to be applied to the catalytic methane oxy-reforming and water gas shift (WGS) reaction respectively. At first the reformate produced by the reforming process at 750 °C was purified using and hydrogen selective empty Pd-based membrane operated at 400 °C. This led to pure hydrogen production but it resulted also in a not-fully exploitation of the membrane performances. Thus, the Pt-based catalyst was loaded in the membrane reactor configuration leading to in situ hydrogen production that helped to increase the separation driving force. The water gas shift reaction downstream oxy-reforming was also studied on the Pt/Ce0.5Zr0.5O2 catalyst and evidenced the consumption of hydrogen by methanation at high H2/H2O ratio. Comparing the WGS membrane reactor with a classical fixed bed demonstrated that removing hydrogen led to increased CO conversion over the equilibrium of an analogous fixed bed, higher H2 yield and suppression of the methanation reaction, even at high inlet H2/H2O ratio. Optimizing the reaction conditions allowed to reach high hydrogen recoveries (89 %) for the integrated oxy-reforming/membrane water gas shift at high GHSV and without the need of a sweep gas.

Enhanced anaerobic hydrogen production from cotton straws assisted by copper molybdate.

Hydrogen production from dark fermentation has potential application due to its environmental friendliness, low production cost, and sustainability. However, there is still an obstacle to improving the efficiency of bioH2 production to meet the requirements in practical applications. In this research, copper molybdates are synthesized under different pH conditions as additives to study their different influence processes during anaerobic hydrogen production from cotton straws with the pure cultural system. A series of results indicate that CuMoO4 with appropriate experimental conditions has the highest H2 yield at 191.3mL/g straws at 37°C, which is 236% higher than the control group. It can be shown that O. ethanolica 8KG-4 has an obvious accompanying with high stability and low cytotoxicity for this clean energy production system as well as the improvement of metabolic pathway. These results extend new thinking of obtaining higher H2 yield as a biofuel in future production.

Low-temperature upcycling of PET waste into high-purity H2 fuel in a one-pot hydrothermal system with in situ CO2 capture.

The accumulation and improper disposal of a large amount of plastic waste have exacerbated the deterioration of the global ecosystem and environment. To simplify the complex management system and alleviate the environmental impact of plastic wastes, this study reports a novel one-pot hydrothermal conversion strategy for polyethylene terephthalate (PET), integrating three steps, namely depolymerization, subsequent in-situ aqueous phase reforming, and in-situ CO2 capture. Here, the PET waste was converted directly into the clean high-purity H2 fuel and the disodium terephthalate (Na2-TPA). A high yield of H2 at 23.7mol/kgPET with ca. 99 % of H2 concentration was obtained at a temperature as low as 240°C. The feasibility of this strategy in handling real-world PET plastic wastes was demonstrated through a series of tests on beverage bottles, food packaging, and polyester fabric waste. The Na2-TPA crystals produced from the proposed PET conversion system exhibited purity close to that of the standard sample, and thus had the potential to be directly used as an electrode material. Overall, this strategy provides an efficient way to transform PET waste into high-value products and improves the sustainability of the PET waste disposal process.

Stepwise photoassisted decomposition of carbohydrates to H2

Stepwise photoassisted decomposition of carbohydrates to H2

Novel nanowire self-assembled hierarchical CeO2 microspheres loaded with nickel-based catalysts for hydrogen production from steam reforming of glycerol

The nickel-based catalysts with shape-specific CeO2 nanocrystals (hierarchical and spheres) and adjustable impregnation solvents were successfully synthesized. The synthesized Ni-CeO2 catalysts were used as the model catalyst to study the structure-dependent catalytic behavior and catalytic reaction mechanism for hydrogen production from glycerol steam reforming (GSR). Ni/CeO2-HE with the hierarchical structure and ethanol impregnation solvent obtained the strongest metal-support interaction. Electron effects because of the strong interaction between nickel and cerium dioxide promoted the formation of reducible nickel species. High nickel reduction and nickel dispersion contributed to the maximum active nickel exposure surface area, thus Ni/CeO2-HE exhibited superior glycerol conversion than other catalysts. The abundant oxygen vacancies generated due to strong Ni-CeO2 interaction facilitated the dissociation of water, thereby achieving a high yield of H2 for Ni/CeO2-HE. As a comparison, Ni/CeO2 and Ni/CeO2-E showed relatively poor catalytic activity due to lower exposed specific surface area and oxygen vacancy concentration. Moreover, the strong oxygen storage-release ability (CO-OSCC) promoted the oxidation of carbon deposition on Ni/CeO2-HE. As a result, Ni/CeO2-HE obtained good catalytic stability with no inactivation within 25 h. The study of the modulation role of Ni-CeO2 interaction on catalytic behavior can provide valuable guidelines for designing efficient catalysts for GSR.

A mini review on recent progress of steam reforming of ethanol.

H2 is one of the promising renewable energy sources, but its production and transportation remain challenging. Distributed H2 production using liquid H2 carriers is one of the ideal ways of H2 utilization. Among common H2 carriers, ethanol is promising as it has high H2 content and can be derived from renewable bio-energy sources such as sucrose, starch compounds, and cellulosic biomass. To generate H2 from ethanol, steam reforming of ethanol (SRE) is the most common way, while appropriate catalysts, usually supported metal catalysts, are indispensable. However, the SRE process is quite complicated and always accompanied by various undesirable by-products, causing low H2 yield. Moreover, the catalysts for SRE are easy to deactivate due to sintering and carbon deposition under high reaction temperatures. In recent years, lots of efforts have been made to reveal SRE mechanisms and synthesize catalysts with high H2 yield and excellent stability. Both active metals and supports play an important role in the reaction. This mini-review summarizes the recent progress of SRE catalysts from the view of the impacts of active metals and supports and draws an outlook for future research directions.

Laser-Induced Methanol Decomposition for Ultrafast Hydrogen Production

Methanol (CH3OH) is a liquid hydrogen (H2) source that effectively releases H2 and is convenient for transportation. Traditional thermocatalytic CH3OH reforming reaction is used to produce H2, but this process needs to undergo high reaction temperature (e.g., 200 °C) along with a catalyst and a large amount of carbon dioxide (CO2) emission. Although photocatalysis and photothermal catalysis under mild conditions are proposed to replace the traditional thermal catalysis to produce H2 from CH3OH, they still inevitably produce CO2 emissions that are detrimental to carbon neutrality. Here, we, for the first time, report an ultrafast and highly selective production of H2 without any catalysts and no CO2 emission from CH3OH by laser bubbling in liquid (LBL) at room temperature and atmospheric pressure. We demonstrate that a super high H2 yield rate of 33.41 mmol·h-1 with 94.26% selectivity is achieved upon the laser-driven process. This yield is 3 orders of magnitude higher than the best value reported for photocatalytic and photothermal catalytic H2 production from CH3OH to date. The energy conversion efficiency of laser light to H2 and CO can be up to 8.5%. We also establish that the far from thermodynamic equilibrium state with high temperature inside the laser-induced bubble and the kinetic process of rapid quenching of bubbles play crucial roles in H2 production upon LBL. Thermodynamically, the high temperature induced using laser in bubbles ensures fast and efficient release of H2 from CH3OH decomposition. Kinetically, rapidly quenching of laser-induced bubbles can inhibit reverse reaction and can keep the products in the initial stage, which guarantees high selectivity. This study presents a laser-driven ultrafast and highly selective production of H2 from CH3OH under normal conditions beyond catalytic chemistry.

Efficient H2 Production from PET Plastic Wastes over Mesoporous Carbon-Supported Ru-ZnO Catalysts in a Mild Pure-Water System

The massive consumption of plastic is posing severe pollution-related challenges globally. As the most abundant polyester plastic, polyethylene terephthalate (PET) waste represents a largely untapped resource for generating chemicals and fuels. However, the current widespread use of alkali/organic solvents and the complex processing of PET reduce its environmental sustainability. Herein, a novel and simple one-pot strategy was first reported for the catalytic conversion of PET into H2 fuel and terephthalic acid in a pure-water system under mild conditions. A high H2 yield of 19.97 mol/kgPET and carbon conversion efficiency of 97.22% were obtained for the Ru-5ZnO/mesoporous carbon (MEC) catalyst at a low temperature of 250 °C. This process proceeds through tandem catalytic reactions with an initial PET depolymerization step, followed by in situ aqueous phase reforming (APR) of ethylene glycol of Ru. Remarkably, ZnO inhibited the deactivation of Ru/MEC in the PET depolymerization stage, causing an increase in H2 production from the in situ APR stage. Importantly, this strategy was successfully applied to four types of real-world PET waste and their mixtures, demonstrating that it has considerable potential in practical applications and provides a sustainable and clean solution to the plastic waste problem.

Strategies of co-cultures and bioaugmentation by Bacillus amyloliquefaciens, Clostridium bifermentans, Enterobacter muelleri, and E. tabaci for increasing the production of hydrogen from raw glycerol

The recovery of glycerol generated by the biodiesel industry was investigated to increase hydrogen production by different strategies by Bacillus amyloliquefaciens (BA), Clostridium bifermentans (CB), Enterobacter muelleri (EM) and E. tabaci (ET) singly, in co-culture and bioaugmentation of the microbial consortium (MC) at different amounts of inoculum (1X and 2X) in batch reactors containing raw glycerol. The inoculum concentrations provided changes in metabolic bioconversion. MC + BA bioaugmentation (2X) showed higher efficiency in converting glycerol (85%) and a high H2 yield (2.21 mol H2 mol−1 glycerol). BA and ET alone (1X) showed high substrate consumption and 0.92 and 0.89 mol H2 mol−1 glycerol, respectively. The cumulative production of H2 was 24% higher for the co-culture BA + CB + ET, but the consumption of glycerol and the yield of H2 were similar to those obtained by monoculture systems. In addition, the favoring of the oxidative metabolic pathway was highlighted, with ethanol generation and reduced concentration of acetic, butyric, and propionic acid for BA, EM, and ET (1X). The bioaugmentation assays (1X) highlighted the reductive pathway with high concentrations of 1,3-propanediol. Both metabolic pathways were used in co-culture. The possibility of valuing residual glycerol in the production of H2 and by-products of economic value using bioaugmentation or isolated microorganisms may be promising.

Concentrated Platinum‐Gallium Nanoalloy for Hydrogen Production from the Catalytic Steam Reforming of Ethanol

AbstractThe steam reforming of ethanol (SRE) is a key process for the production of H2 and other vital hydrocarbons. The present work describes the synthesis of Platinum‐Gallium (Pt−Ga) nanoalloys supported on mesostructured cellular foam (MCF‐17) via ultrasound‐assisted impregnation method. Ga was substituted with Pt in different wt.% i. e. Pt/MCF‐17, Pt99.9Ga0.1/MCF‐17, Pt99Ga1/MCF‐17, and Pt90Ga10/MCF‐17 and was evaluated towards the SRE at a temperature range of 473K‐773 K towards hydrogen (H2), acetaldehyde (CH3CHO), diethylether (DEE), ethylene (C2H4), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and ethane (C2H6). The SRE activity and H2 formation rate with Pt90Ga10/MCF‐17 catalyst were observed to be 68.1 % and 3047.2 nmole g−1 sec−1, which is 9.8 and 4.5 times more than the Pt/MCF‐17 counterparts. Moreover, as observed from DRIFTS, NH3‐TPD and XPS studies Ga showed high interaction with Pt in the electron deficit state which resulted in the increased dehydrogenating and acidic properties that resulted in a higher yield of H2.

Sorption enhanced aqueous phase reforming of biodiesel byproduct glycerol for hydrogen production over Cu-Ni bimetallic catalysts supported on gelatinous MgO

Hydrogen production from sorption enhanced aqueous phase reforming (APR) of biodiesel byproduct glycerol was studied by Ni-based monometallic and bimetallic catalysts supported on gelatinous MgO supports. Compared with Ni-based monometallic catalyst, the H2 selectivity and glycerol conversion of the Cu–Ni bimetallic catalyst were found to be increased more than 3% and 30%, respectively. Meanwhile, higher reaction temperature was found to have higher H2 yield with lower H2 selectivity. The H2 yield using the catalyst with gelatinous MgO support was 1.25 times higher than that of calcined support. Through in-situ CO2 capture, the addition of CaO to the Cu–Ni bimetallic catalyst increased more than 58.3% and 14.4% of the H2 yield and selectivity, respectively. An analysis about liquid product component indicate that the presence of CaO promote the further cleavage of the C–C bond, which further increased the conversion of glycerol. Furthermore, it was found that the presence of CaO could also improve the stability of the catalyst through the control experiments.

Insight into the effect of CeO2 morphology on catalytic performance for steam reforming of glycerol

Shape-specific CeO2 nanocrystals (spheres, rods, cubes and nanoparticles) with well-defined crystal facets were successfully synthesized and used as the support to synthesize series Ni/CeO2. Ni/CeO2 was employed as the model catalysts to study the structure dependent behavior and reaction mechanism for hydrogen production from glycerol steam reforming (GSR). The metal-support interaction was finely tuned by altering the morphology of CeO2 support, which in turn affected the exposed specific surface area of nickel and oxygen vacancy concentration. The relationship between exposed surface area of active nickel as well as surface oxygen vacancies and catalytic performance was studied. Ni/CeO2-S with the mainly exposed (111) type planes obtained the strongest metal-support interaction. Electron effects due to the strong metal-support between nickel and cerium dioxide facilitated the formation of readily reducible nickel species (Niδ+). High nickel reduction and nickel dispersion contributed to the maximum active nickel exposure surface area, thus Ni/CeO2-S showed exceptional glycerol conversion. Meanwhile, the strong Ni-CeO2 interaction resulting in abundant oxygen vacancies that facilitated the dissociation of water to produce hydrogen, thus possessing a high H2 yield. Conversely, Ni/CeO2-NR and Ni/CeO2-NC have lower exposure areas and oxygen vacancy concentrations due to the different exposed crystal planes, and therefore have relatively poor catalytic activity. Moreover, the strong oxygen storage-release ability (CO-OSC-OSCC) promoted the oxidation of carbon deposition on Ni/CeO2-S. Additionally, carbon deposition was mainly the filamentous carbon growing towards the periphery, hence, Ni/CeO2-S obtained up to 25-h catalytic stability. The study of the regulatory role of Ni-CeO2 interaction on catalytic behavior can offer worthwhile direction for designing high-efficiency GSR catalysts.

Hydrogen production by organic waste chemical looping gasification (OW-CLG) enhanced by V2O3 catalysed reforming via partial oxidation approach

Biomass and distillery wastewater are promising sources to produce H2-rich syngas through the thermal conversion. We propose the organic waste chemical looping gasification (OW-CLG) scheme for hydrogen production with straw stalk and concentrated distillery wastewater as feedstock. V2O3 was employed to promote methane reforming and enhance the efficiency of hydrogen production by partially oxidation. Experiments under different temperatures (T) and the molar ratio of V2O3 to CH4 (nV2O3/nCH4) are performed in details. The results show that the above parameters have a significant effect on OW-CLG process. The optimal methane conversion rate of 44.9 % is obtained at oxygen excess ratio, temperature, and mV2O3/mcorn stalk of 0.2, 700 ℃, and 2.16 respectively. The highest H2 yield is 2.05 l with 1 g corn stalk and 20 ml ethanol model solution. The reaction kinetics and the thermodynamics were analyzed, verifying that the introduction of ethanol liquid waste and V2O3 could boost hydrogen generation. The corn stalk OW-CLG is an endothermic process with the total endothermic heat of 5.396 kJ/mol. The thermodynamically feasible temperature range for the partial oxidation of CH4 to hydrogen by V2O3 is above 950 K. V2O3 OC during OW-CLG is regenerated by the reaction of VC and CO2.

Calcium looping of CO2 capture coupled to syngas production using Ni-CaO-based dual functional material

Calcium looping (CaL), which involves carbonation of CaO by CO2 and regeneration of CaO through the conversion of the captured CO2 into useful products, shows promise for carbon capture and utilization. By integrating CaL with methane dry reforming (DRM), the captured CO2 can be converted into syngas, a valuable chemical feedstock and fuel. Herein, a dual functional material (DFM) composed of CaO (CO2 adsorbent), Ni (DRM catalyst) and CeO2 (promoter for DRM) had been developed to drive the CaL-DRM tandem processes. The CaO-Ni-CeO2 DFM possessed high performance of cyclic CaL-DRM: high CO2 uptake efficiency (10.3 mmolCO2/gCaO), high H2 and CO yields (754.4 mmolH2/gNi and 454.6 mmolCO/gNi), moderate required temperature for carbonation (450 °C) and subsequent methane dry reforming (680 °C), and sufficiently high stability. The carbonation of CaO was strongly influenced by the basicity of the material, and the conversion of CH4 with the captured CO2 was affected by the Ni dispersion in the material. Overall, our work demonstrates a prototype study of using a temperature-programmed reaction platform for a quantitative, real-time analysis on CaL-DRM kinetics. The mechanistic understanding of CaL-DRM by the CaO-Ni-CeO2 DFM were elucidated, showing promise for the catalyst optimizations.

Catalytic hydrothermal gasification of aqueous effluents obtained from microwave torrefaction of agricultural residue

A significant amount of aqueous liquids rich in organic, inorganic contents and leached metals is produced during torrefaction of biomass, which requires additional remediation before disposal. Hydrothermal gasification can produce H2-rich syngas from organic wastes, especially from feedstocks with high-water content. This study presents a novel method of valorizing liquid effluents produced from the torrefaction of oat hull and canola hull via microwave irradiation. Hydrothermal gasification of the liquid effluents (feedstock) was carried out at 375–525 °C for 15–60 min with 1:5 and 1:10 feed-to-water ratios under 22–25 MPa pressure to optimize the operating parameters of the process. Hydrothermal gasification of torrefaction effluents from canola hull and oat hull produced total gas yields of 6.6 mmol/g and 8.7 mmol/g, respectively without the addition of water at optimized conditions (525 °C and 45 min). However, with the addition of water (i.e., 1:10 feed-to-water ratio), the total gas yield increased to 12 mmol/g and 16.1 mmol/g from oat hull and canola hull effluents, respectively. The highest H2 yields (7.8 mmol/g) and carbon gasification efficiency (51%) were obtained at 525 °C in 60 min with a 1:10 feed-to-water ratio. Homogeneous catalysts including KOH, K2CO3 and Na2CO3 were used to improve the gas yields from torrefaction effluents from oat hull at optimal conditions. H2 gas yield increased by 58%, 65% and 66% in presence of K2CO3, Na2CO3 and KOH, respectively. KOH led to maximum H2 yield, hydrogen selectivity and carbon gasification efficiency of 12.8 mmol/g, 89% and 98%, respectively.

Simultaneous Decolorization of Tartrazine and Production of H2 in a Combined Electrocoagulation and Photocatalytic Processes using CuO-TiO2 Nanotube Arrays: Literature Review and Experiment

We reported the simultaneous decolorization of tartrazine and H2 production via electrocoagulation and photocatalysis using CuO-doped TiO2 nanotube arrays (TNTA) composites. Tartrazine was removed by the combination of adsorption, electrocoagulation, and photocatalytic degradation, while H2 was produced through water reduction at the cathode and water splitting process on the photocatalyst surface. The photoreactor contains CuO-TNTA as a photocatalyst and is equipped with an 80-W UV lamp. Deposition of CuO on TNTA was conducted using a successive ionic layer adsorption and reaction (SILAR) method. The nanotubular of the TNTA as well as the distribution of CuO were evaluated employing FESEM and HRTEM. XRD patterns confirmed weak diffraction of CuO and TNTA revealing an anatase crystallite phase. The band gap of the CuO-TNTA was also found to be redshifted from that of pure TNTA. The simultaneous processes with the combined systems (20 V, pH = 11) managed to remove 80% of tartrazine while producing a high H2 yield (1.84 mmol), significantly higher than those obtained by each process.