Co-production Of Hydrogen Research Articles

Clean Syngas and Hydrogen Co-Production by Gasification and Chemical Looping Hydrogen Process Using MgO-Doped Fe2O3 as Redox Material

Gasification converts biomass into syngas; however, severe cleaning processes are necessary due to the presence of tars, particulates and contaminants. The aim of this work is to propose a cleaning method system based on tar physical adsorption coupled with the production of pure H2 via a chemical looping process. Three fixed-bed reactors with a double-layer bed (NiO/Al2O3 and Fe-based particles) working in three different steps were used. First, NiO/Al2O3 is used to adsorb tar from syngas (300 °C); then, the adsorbed tar undergoes partial oxidization by NiO/Al2O3 to produce CO and H2 used for iron oxide reduction. In the third step, the reduced iron is oxidized with steam to produce pure H2 and to restore iron oxides. A double-layer fixed-bed reactor was fed alternatively by guaiacol and as tar model compounds, air and water were used. High-thermal-stability particles 60 wt% Fe2O3/40 wt% MgO synthetized by the coprecipitation method were used as Fe-based particles in six cycle tests. The adsorption efficiency of the NiO/Al2O3 bed is 98% and the gas phase formed is able to partially reduce iron, favoring the reduction kinetics. The efficiency of the process related to the H2 production after the first cycle is 35% and the amount of CO is less than 10 ppm.

Biohydrogen production from brown algae fermentation: Relationship between substrate reduction degree and hydrogen production

In this study, mannitol and mannitol-rich seaweed were fermented to investigate the relationship between substrate reduction degree and hydrogen production performance. The results showed that acetate was required in mannitol fermentation with an optimum acetate/mannitol mass ratio of 1:5. Hydrogen production and yield of mannitol fermentation reached 123.76 mL and 2.12 mol/mol-mannitol, respectively, 42.02 % and 26.95 % higher than that of glucose, respectively. The acetate was fully assimilated and the butyrate selectivity reached 100 % in the effluent. Redox potential and electron distribution showed that mannitol increased the overall electron input from mannitol and acetate, leading to the increase in hydrogen and butyrate generation. Hydrogen yield reached 2.33 mol/mol-mannitol with brown algae hydrolysate, which was the highest ever reported. This study demonstrated that substrate with a higher reduction degree could yield higher hydrogen and showed the great application potential of brown algae fermentation for the co-production of hydrogen and butyrate.

Single-atom zinc catalyst for co-production of hydrogen and fine chemicals in soluble biomass solution

Single-atom photocatalysts (SAPCs) have attracted great interests due to their remarkable atom utilization efficiency, excellent activity, and selectivity, yet no application in synchronous biorefinery and water splitting. Here, efficient SAPCs based on atomically dispersed Zn atoms on carbon nitride (named Zn−mCN) were produced. Experiments verified that Zn−mCN has widened adsorption range of visible-light and lowered ability of electron−hole recombination, leading to excellent photocatalytic redox activity for synchronous biorefinery and water splitting to co-produce lactic acid (selectivity up to 91.0%) and hydrogen (∼15898.8 ​μmol ​g − 1 ​h − 1 ). This system has excellent universality for small- molecule monosaccharides and macromolecular xylan. Poisoning experiments showed that h + , 1 O 2 , ·O 2 − and ·OH can promote the simultaneous production of lactic acid and hydrogen. This work realized full utilization of whole redox reaction and provided a novel strategy for efficient and concomitant production of hydrogen and value-added chemicals from biomass-derived feedstocks aqueous solutions. The Zn@mCN single atom photocatalyst with Zn-N6 coordination has widened adsorption range of visible light and lowered ability of electron-hole recombination, leading to excellent photocatalytic redox activity for synchronous biorefinery and water splitting to co-produce lactic acid and hydrogen. Meanwhile, this system presents excellent universality for small molecule monosaccharides and macromolecular xylan.

Modulating lattice oxygen activity of Ca2Fe2O5 brownmillerite for the co-production of syngas and high purity hydrogen via chemical looping steam reforming of toluene

The chemical looping steam reforming (CLSR) of biomass tar enables the process intensification for the co-preparation of syngas and high purity hydrogen. The practical application of brownmillerite-structured Ca2Fe2O5 is hindered by activity-related issues such as low fuel conversion and oxygen transfer capacity. Here, the doping of heteroatoms, e.g. Ni induces structural changes to the brownmillerite lattice, transforming it from a Pnma phase to a Pcmn one, with increased distortion of the FeO6 octahedra. The structural changes lead to the upwards shifts of the O 2p band of oxygen carrier, and subsequently improved lattice oxygen activity as well as oxygen transfer capacity. The formation of oxygen vacancy is a rate determining step during CLSR, while the Ni-doped Ca2Fe2O5 reduces the energy of oxygen vacancy formation and energy barrier for lattice oxygen migration through the bulk. During CLSR, Ca2Ni0.25Fe1.75O5 lead to significant improvement in syngas productivity, hydrogen purity and fuel conversion.

Boosting Hydrogen Production by Selective Anodic Electrooxidation of Ethanol over Trimetallic PdSbBi Nanoparticles: Composition Matters.

The conventional hydrogen evolution from water electrolysis is severely impeded by the sluggish kinetics of oxygen evolution reaction (OER). In this work, an integrated electrolysis system of replacing the anodic OER with a thermodynamically favorable ethanol oxidation reaction (EOR) has been developed by using PdSbBi/C as an electrocatalyst. To maximize the EOR performance, the composition of PdSbBi nanoparticles is tuned by varying the ratio of Sb and Bi precursors. Ternary PdSbBi-based electrocatalysts exhibit enhanced activity and stability toward EOR compared to commercial Pd/C and binary catalysts. In particular, the Pd76Sb17Bi7/C catalyst delivers a very high specific activity up to 52.4 mA cm-2 and mass activity of 2.66 A mg-1Pd. Besides, this EOR process is demonstrated to have high selectivity with acetic acid as the oxidation product in the electrolyte. When coupled with a cathodic platinum mash, the two-electrode electrolyzer cell requires a voltage input of merely 0.61 V to afford a current density of 10 mA cm-2. Density functional theory calculations reveal that the presence of Sb and Bi can promote the adsorption of hydroxide ions and facilitate the removal of reaction intermediates in the EOR pathway. This work provides a novel catalyst for the energy-efficient coproduction of acetic acid and hydrogen fuel.

Pre-combustion mercury removal with co-production of hydrogen via coal electrolysis

Pre-combustion mercury removal via coal electrolysis was performed and investigated on a bench-scale coal electrolytic cell (CEC) systemically, and factorial design was used to determine the effect of different operating conditions (coal particle size, operating temperature, operating cell voltage, and flow rate of slurry) on the percentage of mercury removal, percentage of ash removal, and dry heating value change. The results showed that the operating cell voltage, as well as the interaction between operating cell voltage and coal particle size, are significant factors in the percentage of mercury removal. There is no significant factor in the percentage of ash removal and the dry heating value change, but the coal could be purified while keeping the dry heating value almost constant after electrolysis. A co-product of hydrogen could be produced during coal electrolysis with 50% lower energy consumption compared with water electrolysis. Meanwhile, a mechanism for mercury removal in coal was proposed. The facts indicate that coal electrolysis is a promising method for pre-combustion mercury removal.

Ni2P with phosphorus vacancy supported Pt clusters for efficiently electrocatalytic co-production of hydrogen and value-added chemicals from methanol-water at low potential

Low loading Pt clusters are deposited on Ni2P with phosphorus vacancy which is coated at carbon cloth (Vp-Ni2P-Pt/CC). And Vp-Ni2P-Pt/CC is synthesized as efficient bifunctional electrocatalysts for hydrogen evolution reaction (HER) and selective methanol oxidation reaction (MOR) at methanol–water co-electrolysis. The loading of Pt is only 12.97 μg cm−2, and the synergistic effect with the substrate material Ni2P enables efficient MOR at low potential (0.6 V vs RHE), and the mass activity of Pt can reach 9.16 A mg-1Pt. Compared with the oxygen evolution reaction (OER) in the water electrolysis, the MOR potential is negatively shifted by 931 mV during co-electrolysis, and the energy consumption of hydrogen production is saved by 40–55%. Moreover, value-added chemicals formate is simultaneously co-generated while without CO2 emission.

Promotional Effects on the Catalytic Activity of Co-Fe Alloy Supported on Graphitic Carbon for CO2 Hydrogenation.

Starting from the reported activity of Co-Fe nanoparticles wrapped onto graphitic carbon (Co-Fe@C) as CO2 hydrogenation catalysts, the present article studies the influence of a series of metallic (Pd, Ce, Ca, Ca, and Ce) and non-metallic (S in various percentages and S and alkali metals) elements as Co-Fe@C promoters. Pd at 0.5 wt % somewhat enhances CO2 conversion and CH4 selectivity, probably due to H2 activation and spillover on Co-Fe. At similar concentrations, Ce does not influence CO2 conversion but does diminish CO selectivity. A 25 wt % Fe excess increases the Fe-Co particle size and has a detrimental effect due to this large particle size. The presence of 25 wt % of Ca increases the CO2 conversion and CH4 selectivity remarkably, the effect being attributable to the CO2 adsorption capacity and basicity of Ca. Sulfur at a concentration of 2.1% or higher acts as a strong poison, decreasing CO2 conversion and shifting selectivity to CO. The combination of S and alkali metals as promoters maintain the CO selectivity of S but notably increase the CO2 conversion. Overall, this study shows how promoters and poisons can alter the catalytic activity of Co/Fe@C catalysts, changing from CH4 to CO. It is expected that further modulation of the activity of Co/Fe@C catalysts can serve to drive the activity and selectivity of these materials to any CO2 hydrogenation products that are wanted.

Coke formation in the co-production of hydrogen and phenols from pyrolysis-reforming of lignin

The phenolics derived from pyrolysis of lignin are important fractions of bio-oil, which could be reformed to generate hydrogen. Nevertheless, some phenolics are value-added chemicals and they might not have to be utilized as source of hydrogen. In this study, we have explored the concept of co-production of hydrogen and phenolics via a pyrolysis-reforming process at the low to medium temperatures of 450–650 °C over Ni/Al2O3 catalyst. The results indicated that, below 500 °C, pyrolysis of lignin was almost the exclusive reaction route to form phenolics of varied side chains. The effective reforming of the phenolics initiated at 600 °C and became remarkable at 650 °C. Meanwhile, cracking of the methoxy group and other side chains of the phenolics was also intense at these higher temperatures, producing phenol as the main phenolic compound. Polymerization of the phenolics on Ni/Al2O3 catalyst occurred from 450 to 650 °C, while the gasification of the precursors of coke accelerated at 650 °C, forming remarkably lower amount of coke together with enhanced yield of hydrogen. The coke formed from the phenolics was generally the polymeric type with abundant aliphatic structures like C–O–C, –OH and -C-H, low thermal stability, low carbon crystallinity, hydrophilic surface and amorphous morphology at 450–650 °C. The polymerization or cracking of the phenolics could form multiple carbon layers in the vicinity of nickel species, and also on alumina.

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.

Hydrogen and CNT Production by Methane Cracking Using Ni–Cu and Co–Cu Catalysts Supported on Argan-Derived Carbon

The 21st century arrived with global growth of energy demand caused by population and standard of living increases. In this context, a suitable alternative to produce COx-free H2 is the catalytic decomposition of methane (CDM), which also allows for obtaining high-value-added carbonaceous nanomaterials (CNMs), such as carbon nanotubes (CNTs). This work presents the results obtained in the co-production of COx-free hydrogen and CNTs by CDM using Ni–Cu and Co–Cu catalysts supported on carbon derived from Argan (Argania spinosa) shell (ArDC). The results show that the operation at 900 °C and a feed-ratio CH4:H2 = 2 with the Ni–Cu/ArDC catalyst is the most active, producing 3.7 gC/gmetal after 2 h of reaction (equivalent to average hydrogen productivity of 0.61 g H2/gmetal∙h). The lower productivity of the Co–Cu/ArDC catalyst (1.4 gC/gmetal) could be caused by the higher proportion of small metallic NPs (<5 nm) that remain confined inside the micropores of the carbonaceous support, hindering the formation and growth of the CNTs. The TEM and Raman results indicate that the Co–Cu catalyst is able to selectively produce CNTs of high quality at temperatures below 850 °C, attaining the best results at 800 °C. The results obtained in this work also show the elevated potential of Argan residues, as a representative of other lignocellulosic raw materials, in the development of carbonaceous materials and nanomaterials of high added-value.

An innovative strategy on co-production of porous carbon and high purity hydrogen by alkaline thermal treatment of rice husk

An innovative biomass conversion method was proposed to co-produce porous carbon and high purity hydrogen by alkaline thermal treatment (ATT). Hydrogen with purity over 80 vol % and porous carbon with a specific surface area of 2298.5 m2/g were co-produced at 500 °C for the first time. In this study, the effects of various reaction parameters on hydrogen production and the properties of porous carbon were investigated. The composition of gas products was tested, and the pore structure, morphology, graphitization degree and crystal structure of porous carbon were analyzed. The results showed that the optimum experimental conditions were alkali/rice husk mass ratio of 3:1, reaction temperature of 500 °C and reaction time of 60 min. A variety of characterization results showed that alkali etched the surface of rice husk at appropriate temperature, forming a large number of pore structures, and releasing volatile substances and hydrogen. The addition of alkali reduced the microcrystalline structure between graphite layers and increased the proportion of amorphous structure in porous carbon. Electrochemical test results showed that the specific capacitance of porous carbon prepared under the best reaction conditions reached 228.94 F/g at the current density of 0.2 A/g.

Effects of Catalytic Promoter Mn on Ni/ZSM-5 Catalyst to Catalyst Waste Plastic Syngas to Prepare Carbon Nanotubes for Co-Production of Hydrogen

Carbon nanotubes (CNTs) produced by catalytic reforming of the waste plastic syngas is a high value-added by-product of hydrogen production. Catalysts play an important role in the growth of carbon nanotubes. The influences of Ni/ZSM-5 catalyst, Ni–Mn/ZSM-5 catalyst and temperature were performed in a lab-scale tubular reactor. The catalysts and product carbon were analyzed by different characterization methods, including temperature-programed reduction/oxidation, X-ray diffractometer, scanning electron microscope, transmission electron microscope, X-ray energy spectrometer. The results showed that in the presence of Ni–Mn/ZSM-5 catalyst with the addition of catalytic promoter Mn, 650 °C was the optimum temperature during the operating temperature range of 600 °C~800 °C for the rate of carbon production and hydrogen production, and the carbon production was the highest, which was 2.95gCNTs/gCatalyst (wherein the Multi-walled carbon nanotubes (MWCNTs) were main product), and compared with the monometallic Ni/ZSM-5 catalyst, the Ni–Mn/ZSM-5 catalyst with Mn addition increased the H2 content in the syngas from 14 Vol.% to 39 Vol.%. The highest carbon nanotubes proportion of 95.81% to total carbon deposition was obtained under the conditions of 750 °C. The introduction of catalytic promoter Mn transforms the growth mode of carbon nanotubes from top growth mode to bottom growth mode, and obtains carbon nanotubes with more regular structure. It suggested that Ni–Mn/ZSM-5 catalyst had the potential for high quality carbon nanotubes and H2-riched gas production from waste plastic syngas.

A theoretical study of molten carbonate fuel cell combined with a solar power plant and Cu–Cl thermochemical cycle based on techno-economic analysis

A novel power and hydrogen coproduction system is designed and analyzed from energetic and economic point of view. Power is simultaneously produced from parabolic trough collector power plant and molten carbonate fuel cell whereas hydrogen is generated in a three-steps Cu–Cl thermochemical cycle. The key component of the system is the molten carbonate fuel cell that provides heat to others (Cu–Cl thermochemical cycle and steam accumulator). A mathematic model is developed for energetic and economic analyses. A parametric study is performed to assess the impact of some parameters on the system performance. From calculations, it is deduced that electric energy from fuel cell, solar plant and output hydrogen mass are respectively 578 GWh, 25 GWh and 306 tons. The overall energy efficiency of the proposed plants is 46.80 % and its LCOE is 7.64 c€/kWh. The use of MCFC waste heat allows increasing the solar power plant efficiency by 2.15 % and reducing the annual hydrogen consumption by 3 %. Parametric analysis shows that the amount of heat recovery impacts the energy efficiency of fuel cell and Cu–Cl cycle. Also, current density is a key parameter that influences the system efficiency.

Coproduction of hydrogen, butanol, butanediol, ethanol, and biogas from the organic fraction of municipal solid waste using bacterial cocultivation followed by anaerobic digestion

An integrated bioprocessing approach was applied to enhance energy recovery from the biodegradable fraction of municipal solid waste (BFMSW). Clostridium acetobutylicum and Enterobacter aerogenes with complementary characteristics were cocultivated for coproduction of hydrogen, 2,3-butanediol, and acetone-butanol-ethanol (ABE). Following the fermentation process, the remaining solids were used for biomethane production. The BFMSW was first subjected to ethanolic organosolv pretreatment and then enzymatic cellulose and hemicellulose hydrolysis at 5 and 8% solid loadings. The glucose (328 g/kg raw BFMSW), xylose (37.8 g/kg raw BFMSW), and starch (152.1 g/kg raw BFMSW) portions of the pretreated BFMSW hydrolysate with 5% solid loading were cofermented to hydrogen (162.8 L/kg raw BFMSW), 2,3-butanediol (42.5 g/kg raw BFMSW), butanol (121.9 g/kg raw BFMSW), ethanol (38.9 g/kg raw BFMSW), and acetone (45.2 g/kg raw BFMSW) by the coculture, and subsequently, the residual unfermented solids were further digested to biomethane (31.7 L/kg raw BFMSW). From the bioenergy perspective, 311.8 mL gasoline equivalent (10 MJ energy) was obtained from each kg of raw BFMSW, indicating the potential of the integrated fermentation-anaerobic digestion bioprocess for biofuels production from the zero-cost substrate.

Pt@MIL-101(Fe) for efficient visible light initiated coproduction of benzimidazoles and hydrogen from the reaction between o-Phenylenediamines and alcohols

A Pt@MIL-101(Fe) nanocomposite, with Pt nanoparticles (NPs) fully embedded and well dispersed in the matrix of MIL-101(Fe), was prepared via a microwave-assisted self-assembly of MIL-101(Fe) in the presence of PVP-capped Pt colloids (PVP = polyvinylpyrrolidone). The as-obtained Pt@MIL-101(Fe) nanocomposite shows a superior activity for the one-pot reaction between o-phenylenediamines and alcohols to synthesize benzimidazoles under visible light, with concomitant generation of clean energy hydrogen, ascribed to an efficient mass diffusion and substrate-catalyst interactions imparted by the MOFs. The embedding of the Pt NPs within the MIL-101(Fe) contributes to the relatively high stability of Pt@MIL-101(Fe), since the aggregation of the Pt NPs can be significantly inhibited. This study not only provides a green and atom-efficiency strategy for the synthesis of benzimidazoles with concomitant generation of clean hydrogen, but also demonstrates that a rational fabrication of metal NPs/MOFs nanocomposites is important for them to be used as multifunctional catalysts for light initiated one-pot tandem/cascade reactions.

Co-production of hydrogen and acetaldehyde from ethanol over a highly dispersed Cu catalyst

Ethanol is one of the most promising bio-based renewable platform chemicals. Catalytic upgrading of ethanol into valuable products is of great importance, and co-production of hydrogen and acetaldehyde via the dehydrogenation of ethanol is an effective way for its high atomic utilization. In this work, unsaturated Cu sites (Cu1.4/ZnxMg4.6-xAl2O7.6) with plenty interface of between Cu and support, strong metal-support interaction were synthesized via the controlled calcination and reduction of hydrotalcite-like Cu1.4ZnxMg4.6-xAl2(OH)16CO3 and used in the dehydrogenation of ethanol. Characterization results disclosed that the dispersion of Cu and surface area of Cu1.4/Zn3.2Mg1.4Al2O7.6 reached 77.8% and 167.5 m2/g, respectively. This catalyst exhibited excellent activity for the dehydrogenation of ethanol to acetaldehyde, and the detected selectivity of acetaldehyde and H2 was higher than 98.5% at 280 °C, 0.1 MPa and WHSV = 11.8 h−1. The calculated space–time yield of acetaldehyde reached 7.0 g-acetaldehyde/g-cat/h. At the same time, Cu1.4/Zn3.2Mg1.4Al2O7.6 could maintain its activity within 50 h on stream.

Development of a universal method for high yield of furfural and hydrogen from raw lignocellulosic biomass

In order to develop a universal method for the co-production of furfural and hydrogen from raw lignocellulosic biomass, three types of substrates (maple wood, wheat straw, and tall fescue) were investigated, integrating chemical and electrochemical technologies. The results show both furfural and pure hydrogen were produced from all the biomass substrates, and the substrate type, composition, concentration, and size all affected furfural and hydrogen production. The highest furfural production of 154 mg g−1 substrate was achieved from wheat straw. The highest conversion rate of 67% for the waste furfural residue was realized, and 335 ml pure hydrogen per gram of furfural residue with a Faradaic efficiency of 99.3% was obtained with a new electrolytic cell. A reaction mechanism for hydrogen evolution from furfural residue and a rule for co-production of furfural and hydrogen from raw biomass were proposed. The facts show that a promising universal method for the co-production of furfural and hydrogen from lignocellulosic biomass has been developed.

Stability investigation of polyPOSS-imide membranes for H2 purification and their application in the steel industry

In the present work, the high-temperature and long-term hydrothermal stability of novel polyPOSS-imide membranes for high-temperature hydrogen separation is investigated. The polyPOSS-imide membranes are found to exhibit an appropriate stability up to 300 °C. Above this temperature the membrane selectivity rapidly decreases, which is seemingly related to changes in the molecular structure coupled to silanol condensation forming siloxane groups. Surprisingly, the exposure of the membrane to temperatures of up to 300 °C even increases the H 2 permeance together with the selective feature of the polyPOSS-imide layer. Subsequently, the long-term hydrothermal stability of the polyPOSS-imide membranes was investigated over a period of close to 1000 h at 250 °C exposing the membrane to 10 mol% steam in the feed. An increase in H 2 /CH 4 selectivity was observed upon water addition, and even though a minor drop was noticed over time during the hydrothermal operation, the selectivity exceeds the initial selectivity obtained in the dry feed atmosphere. After the removal of steam from the feed the performance returns to its original state prior to the exposure to any steam showing an appropriate steam stability of the polyPOSS-imide membranes. A conceptual process design and assessment was performed for application of these membranes involving a combination of carbon reuse and electrification of the steel making process with co-production of hydrogen. The results indicate a CO 2 avoidance of 14%. The CO 2 reduction achieved using renewable electricity in the proposed scheme is a factor 2.76 higher compared to a situation where the same renewable electricity would be fed in the electricity grid. • Exposure of the polyPOSS-imide membrane to 300 °C increases the H 2 permeance. • Long-term hydrothermal stability of polyPOSS-imide membranes proven. • Membranes were operated over a period of 1000 h. • Process evaluation for implementation in the steel industry performed.

CO2-negative biomass conversion: An economic route with co-production of green hydrogen and highly porous carbon

The global consensus of carbon neutralization calls for new ideas of CO2 capture, conversion and utilization, especially CO2-negative technologies. In this work, a CO2-negative process was developed to convert three different types of biomass species into valuable products, green hydrogen and activated carbon (AC). Four reaction modules including pyrolysis, activation, flue gas reforming, and chemical looping were integrated and balanced in terms of mass and energy. After optimization, green H2 with up to 95.54% purity can be produced with price as low as $3.10/kg. The solid AC product can fix 10–20 wt% of carbon element from biomass to achieve a similar proportion of reduced CO2 emission. Part of the separated CO2 can be reused in the activation process and converted to CO product for internal use. Overall, this process demonstrates an economic route for biomass conversion with the co-production of green hydrogen and value-added AC products. Moreover, CO2-negative emission is also realized.