Dry and steam reforming of biomass pyrolysis gas for rich hydrogen gas

Biomass pyrolysis gas (including H₂, CO, CH₄, CO₂, C₂H₄, C₂H₆ and etc.) reforming for hydrogen production over Ni/Fe/Ce/Al₂O₃ catalysts was presented in this study. This study investigated how the operating conditions, such as the calcinations temperature of catalysts, the reaction temperature, the gas hourly space velocity (GHSV) and the ratio of H₂O/C, affect the conversion of CH₄ and CO₂ and the selectivity of hydrogen from dry and steam reforming of pyrolysis gas. The experimental results indicated that, under the conditions: the reaction temperature of 600 °C, the GHSV of 900 h⁻¹ and H₂O/C of 0.92, the reaction efficiency is the optimal. Especially, the concentration of H₂, CO, CH₄, CO₂, and C₂H_n (C₂H₄ and C₂H₆) were 36.80%, 10.48%, 9.61%, 42.62%, 0.49% respectively. The conversion of CH₄ and CO₂ reached 45.9% and 51.09%, respectively. There were all kinds of reactions during the processing of reforming of pyrolysis gas. And the main reactions changed with the operation condition. It was due to the promoting or inhibiting interaction among different constituents in the pyrolysis gas and the different activity of catalysts in the different operation condition.     

Syngas yield during pyrolysis and steam gasification of paper

Main characteristics of gaseous yield from steam gasification have been investigated experimentally. Results of steam gasification have been compared to that of pyrolysis. The temperature range investigated were 600–1000 °C in steps of 100 °C. Results have been obtained under pyrolysis conditions at same temperatures. For steam gasification runs, steam flow rate was kept constant at 8.0 g/min. Investigated characteristics were evolution of syngas flow rate with time, hydrogen flow rate and chemical composition of syngas, energy yield and apparent thermal efficiency. Residuals from both processes were quantified and compared as well. Material destruction, hydrogen yield and energy yield is better with gasification as compared to pyrolysis. This advantage of the gasification process is attributed mainly to char gasification process. Char gasification is found to be more sensitive to the reactor temperature than pyrolysis. Pyrolysis can start at low temperatures of 400 °C; however char gasification starts at 700 °C. A partial overlap between gasification and pyrolysis exists and is presented here. This partial overlap increases with increase in temperature. As an example, at reactor temperature 800 °C this overlap represents around 27% of the char gasification process and almost 95% at reactor temperature 1000 °C.     

Inhibition of steam gasification of biomass char by hydrogen and tar

The influence of hydrogen and tar on the reaction rate of woody biomass char in steam gasification was investigated by varying the concentrations in a rapid-heating thermobalance reactor. It was observed that the steam gasification of biomass char can be separated into two periods. Compared with the first period, in the second period (in which the relative mass of remaining char is smaller than 0.4) the gasification rate is increased. These effects are probably due to inherent potassium catalyst. Higher hydrogen partial pressure greatly inhibits the gasification of biomass char in the first and second periods. By calculating the first-order rate constants of char gasification in the first and second periods, we found that the hydrogen inhibition on biomass char gasification is caused by the reverse oxygen exchange reaction in the first period. In the second period, dissociative hydrogen adsorption on the char is the major inhibition reaction. The influence of levoglucosan, a major tar component derived from cellulose, was also examined. We found that not only hydrogen but also vapor-phase levoglucosan and its pyrolysates inhibited the steam gasification of woody biomass char. By mixing levoglucosan with woody biomass sample, the pyrolysis of char proceeds slightly more rapidly than with woody biomass alone, and gas evolution rates of H₂ and CO₂ are larger in steam gasification.     

Production of renewable hydrogen by steam reforming of tar from biomass pyrolysis over supported Co catalysts

Co catalyst supported on BaAl₁₂O₁₉ (BA) showed higher activity in the steam reforming of tar from the pyrolysis of biomass than those supported on Al₂O₃, ZrO₂, SiO₂, MgO, and TiO₂. Characterization results indicate that the Co metal particles supported on BA had high dispersion, although the surface area of Co/BA was small. High dispersion of Co metal particles on BA can account for the high steam reforming activity, and this high dispersion is related to the strong basicity of the BA surface. Strong basicity of BA and high dispersion of Co metal particles on BA are connected to high H₂O reactivity to form H₂, probably at the interface between Co metal and BA. In addition, the Co/BA catalyst exhibited higher reusability through the coke combustion and the subsequent reduction treatment than the Co/Al₂O₃ catalyst. This is attributed to the suppression of the solid reaction between the oxidized Co and BA.     

Catalytic steam reforming of acetic acid for hydrogen production

A variety of supported metal catalysts were tested under conditions of steam reforming of acetic acid (HAc), which was selected as a model compound for pyrolysis oil. The influence of several parameters on catalytic activity and selectivity were examined, including catalyst composition, i.e. nature of the metal and the carrier, reaction temperature and time on stream. The metallic phase of such catalysts was comprised of various metals, such as Pt, Pd, Rh, Ru and Ni, which were supported on metal oxides carriers, such as _Al2O3${\mathrm{Al}}_2{\mathrm{O}}_3$, _La2O3/_Al2O3${\mathrm{La}}_2{\mathrm{O}}_3/{\mathrm{Al}}_2{\mathrm{O}}_3$, MgO/_Al2O3$\mathrm{MgO}/{\mathrm{Al}}_2{\mathrm{O}}_3$ and _CeO2/_Al2O3${\mathrm{CeO}}_2/{\mathrm{Al}}_2{\mathrm{O}}_3$. It was found that Ni-based and Ru-based catalysts present high activity and selectivity toward hydrogen production. Ru catalysts supported on _La2O3/_Al2O3${\mathrm{La}}_2{\mathrm{O}}_3/{\mathrm{Al}}_2{\mathrm{O}}_3$ and MgO/_Al2O3$\mathrm{MgO}/{\mathrm{Al}}_2{\mathrm{O}}_3$ carriers, showed good long-term stability as a function of time on stream. However, Ni catalysts were not as stable as Ru catalysts. The amount of carbon deposited on each catalyst was estimated, and it was found that it depends strongly on the nature of the catalyst.     

Hydrogen from aqueous fraction of biomass pyrolysis liquids by catalytic steam reforming in fluidized bed

Sustainable pathways for producing hydrogen as a synthesis intermediate or as a clean energetic vector will be needed in the future. Renewable biomass resources should be taken into account in this new scenario. Processing through a pyrolysis step, optimized to high liquid production (bio-oil), increases the energy bulk density of biomass for transportation. Steam reforming of the aqueous fraction is an alternative process that increases the hydrogen content of the syngas. However, the thermochemical conversion of organic compounds derived from biomass involves drawbacks such as coke formation on the catalysts. This work studies the performance of Ni-Al catalysts modified with Ca or Mg in the steam reforming of the aqueous fraction of pyrolysis liquids and the resulting coke deposits. The catalyst composition influenced the quantity and type of coke deposits. Calcium improved the formation of carbonaceous products leading to lower H₂/CO ratios while magnesium improved the WGS (water gas shift) reaction. The strategy of reducing the space velocity resulted in a low coke removal although the addition of small quantities of oxygen decreased the coke content of the catalyst by more than 50% weight. Greater efficiency and further catalyst development are needed to improve the energetic requirements of the process.     

Exergy analysis of hydrogen production from steam gasification of biomass: A review

Exergy analysis of hydrogen production from steam gasification of biomass was reviewed in this study. The effects of the main parameters (biomass characteristics, particle size, gasification temperature, steam/biomass ratio, steam flow rate, reaction catalyst, and residence time) on the exergy efficiency were presented and discussed. The results show that the exergy efficiency of hydrogen production from steam gasification of biomass is mainly determined by the H₂ yield and the chemical exergy of biomass. Increases in gasification temperatures improve the exergy efficiency whereas increases in particle sizes generally decrease the exergy efficiency. Generally, both steam/biomass ratio and steam flow rate initially increases and finally decreases the exergy efficiency. A reaction catalyst may have positive, negative or negligible effect on the exergy efficiency, whereas residence time generally has slight effect on the exergy efficiency.     

Hydrogen production from catalytic steam reforming of biomass pyrolysis oil or bio-oil derivatives: A review

Steam reforming of biomass pyrolysis oil or bio-oil derivatives is one of the attractive approaches for hydrogen production. The current research focused on the development of promising catalysts with favorable catalytic activity and high coke resistance. Noble metal such as Rh has been proven to achieve promising reforming reaction efficiencies. However, Ni has attracted considerable attention owing to its stability, cost effectiveness, and good activity in breaking C–C and C–H bonds. Nevertheless, Ni-based catalysts have serious carbon deposition problems arising from chemical poisoning, metal sintering, and poor metal dispersion. This paper attempted to review the current trends in catalyst development considering the aspects of supports, metals, and promoters as an effort to find possible solutions for the limitations of Ni-based catalysts. The present review also covered the current understanding on the reaction mechanisms as well as the future prospects in the field of steam reforming catalysts.     

Absorption-enhanced steam gasification of biomass for hydrogen production: Effect of calcium oxide addition on steam gasification of pyrolytic volatiles

The effect mechanism of calcium oxide (CaO) addition on gasification of pyrolytic volatiles as a key sub-process in the absorption-enhanced steam gasification of biomass (AESGB) for H₂ production at different conditions was investigated using a two-stage fixed-bed pyrolysis–gasification system. The results indicate that CaO functions as a CO₂ absorbent and a catalyst in the volatiles gasification process. CaO triggers the chemical equilibrium shift to produce more H₂ and accelerates volatile cracking and gasification reactions to obtain high volatile conversion rates. Increasing the gasification temperature could improve the reaction rate of cracking and gasification of volatiles as well as the catalytic effect of CaO, which continuously increase H₂ yield. When the gasification temperature exceeds 700 °C, the sharp decrease in CO₂ absorption capability of CaO drastically increases the CO₂ concentration and yield, which significantly decrease H₂ concentration. The appropriate temperature for the absorption-enhanced gasification process should be selected between 600 °C and 700 °C in atmospheric pressure. Increasing the water injection rate (represented as the mass ratio of steam to biomass) could also improve H₂ yield. The type of biomasses is closely associated with H₂ yield, which is closely related to the volatile content of biomass materials.     

Pyrolysis-catalytic steam reforming of agricultural biomass wastes and biomass components for production of hydrogen/syngas

The pyrolysis-catalytic steam reforming of six agricultural biomass waste samples as well as the three main components of biomass was investigated in a two stage fixed bed reactor. Pyrolysis of the biomass took place in the first stage followed by catalytic steam reforming of the evolved pyrolysis gases in the second stage catalytic reactor. The waste biomass samples were, rice husk, coconut shell, sugarcane bagasse, palm kernel shell, cotton stalk and wheat straw and the biomass components were, cellulose, hemicellulose (xylan) and lignin. The catalyst used for steam reforming was a 10 wt.% nickel-based alumina catalyst (NiAl₂O₃). In addition, the thermal decomposition characteristics of the biomass wastes and biomass components were also determined using thermogravimetric analysis (TGA). The TGA results showed distinct peaks for the individual biomass components, which were also evident in the biomass waste samples reflecting the existence of the main biomass components in the biomass wastes. The results for the two-stage pyrolysis-catalytic steam reforming showed that introduction of steam and catalyst into the pyrolysis-catalytic steam reforming process significantly increased gas yield and syngas production notably hydrogen. For instance, hydrogen composition increased from 6.62 to 25.35 mmol g^?1 by introducing steam and catalyst into the pyrolysis-catalytic steam reforming of palm kernel shell. Lignin produced the most hydrogen compared to cellulose and hemicellulose at 25.25 mmol g^?1. The highest residual char production was observed with lignin which produced about 45 wt.% char, more than twice that of cellulose and hemicellulose.     

Synergistic effect of curcumin and activated carbon catalyst enhancing hydrogen production from biomass pyrolysis

This study observes the synergistic effect of low cost and environmentally friendly catalysts, Activated Carbon and curcumin on the production of hydrogen gas in the biomass pyrolysis process. The Study used turmeric containing curcumin as an anti-oxidant agent added to the activated carbon (AC) catalyst. Biomass from coconut wood was pyrolyzed up to 550 °C using a fixed bed reactor. Both AC and curcumin were combined with a ratio of 1:0, 1:1, 1: 3, 0:1, and 3:1. The addition of AC and curcumin was able to increase the production of hydrogen and methane gas. The combination of AC and curcumin with 1:1 ratio was able to increase hydrogen gas by 25.6%. In addition, this combination was also increase methane gas by 71.8%.Curcumin as an anti-oxidant is able to prevents recombination reactions between radical molecules. Activated carbon surface is more protected from free radicals attacking and sticking to the surface. The phi-phi interaction between the two aromatic rings and the surface of activated carbon produces electrostatic forces on the surface of activated carbon to become stronger therefore it is more reactive in cracking hydrocarbon molecules and producing hydrogen gas. Software simulation, SEM, XRD, and FTIR tests were performed to support the analysis of experimental results.     

Renewable hydrogen production via steam reforming of simulated bio-oil over Ni-based catalysts

The production of hydrogen via steam reforming (SR) of simulated bio-oil (glycerol, syringol, n-butanol, m-xylene, m-cresol, and furfural) was investigated over Ni/CeO₂-Al₂O₃ and Me-Ni/CeO₂-Al₂O₃ (Me = Rh, Ru) catalysts. Monometallic (Ni) and bimetallic (Rh-Ni and Ru-Ni) catalysts were prepared by the wetness impregnation technique of the CeO₂-Al₂O₃ support previously synthesized by the surfactant-assisted co-precipitation method. The as-prepared powders were systematically characterized by N₂-physisorption, XRD, H₂-TPR, and TEM measurements to analyze their structure, morphology, and reducibility properties. Experiments were performed in a continuous fixed-bed reactor at atmospheric pressure, temperature of 800 °C, steam to carbon (S/C) ratio of 5, and WHSV of 21.15 h⁻¹. Then, the temperature was decreased to 700 °C and increased afterwards to 800 °C. After the experiments TPO and TEM analysis were performed on the spent catalysts to check any evidence of catalyst deactivation. The results showed that the incorporation of noble metal (Ru or Rh) promoter positively affected the activity of the Ni/CeO₂-Al₂O₃ catalysts by enhancing the reducibility of Ni²⁺ species. Ni-based catalyst deactivated under the studied conditions, whereas Ru- and mainly Rh-promoted systems showed increased resistance to carbon deposition by favouring the gasification of adsorbed carbon species. Between all tested catalysts, the Rh-Ni/CeO₂-Al₂O₃ provided the highest H₂ yield and coking-resistance in SR of simulated bio-oil.     

High hydrogen content syngas for biofuels production from biomass air gasification: Experimental evaluation of a char-catalyzed steam reforming unit

This work investigates the performance of a reformer reactor for the upgrading of syngas and char derived from a pilot-scale air gasifier. The proposed setup represents a circular approach for the production of hydrogen-rich syngas from air gasification. Specifically, the reforming-unit was operated under a range of temperatures (from 700 °C to 850 °C) and steam flow rates and for each the improvement in producer gas composition and reducing species yield is evaluated. The results highlight that an increase in hydrogen concentration is obtained at higher temperature, moving from 16.2% to 21.3%, without using steam, and to 45.6%, with steam injection on the char-bed, while CO concentration did not follow a monotonic behavior. Moreover, the gas quality index, defined as a ratio between reducing species and inert species, delivered the highest values at the highest temperatures and steam flow rates. These results provide a guide for future gas quality optimization studies.     

Potential to retrofit existing small-scale gasifiers through steam gasification of biomass residues for hydrogen and biofuels production

This work investigates the opportunity of retrofitting existing small-scale gasifiers shifting from combined heat and power (CHP) to hydrogen and biofuels production, using steam and biomass residues (woodchips, vineyard pruning and bark). The experiments were carried out in a batch reactor at 700 °C and 800 °C and at different steam flow (SF) rates (0.04 g/min and 0.20 g/min). The composition of the producer gas is in the range of 46–70 % H₂, 9–29 % CO, 12–27 % CO₂, and 2–6 % CH₄. A producer gas specific production factor of approx. 10 NL_pg/g_char can be achieved when the lower SFs are used, which allows to provide 80 % of the hydrogen concentration required for biomethanation and MeOH synthesis. As for FT synthesis, an optimal H₂/CO ratio of approx. 2 can be achieved. The results of this work provide further evidence towards the feasibility of hydrogen and biofuels generation from residual biomass through steam gasification.     

Existing large steam power plant upgraded for hydrogen production

This paper presents and discusses the results of a complete thermoeconomic analysis of an integrated power plant for co-production of electricity and hydrogen via pyrolysis and gasification processes fed by various coals and mixture of coal and biomass, applied to an existing large steam power plant (ENEL Brindisi power plant – 660 MW_e). Two different technologies for the syngas production section are considered: pyrolysis process and direct pressurized gasification. Moreover, the proximity of a hydrogen production and purification plants to an existing steam power plant favors the inter-exchange of energy streams, mainly in the form of hot water and steam, which reduces the costs of auxiliary equipment. The high quality of the hydrogen would guarantee its usability for distributed generation and for public transport. The results were obtained using WTEMP thermoeconomic software, developed by the Thermochemical Power Group of the University of Genoa, and this project has been carried out within the framework of the FISR National project “Integrated systems for hydrogen production and utilization in distributed power generation”.     

Challenges for renewable hydrogen production from biomass

The increasing demand for H₂ for heavy oil upgrading, desulfurization and upgrading of conventional petroleum, and for production of ammonium, in addition to the projected demand for H₂ as a transportation fuel and portable power, will require H₂ production on a massive scale. Increased production of H₂ by current technologies will consume greater amounts of conventional hydrocarbons (primarily natural gas), which in turn will generate greater greenhouse gas emissions. Production of H₂ from renewable sources derived from agricultural or other waste streams offers the possibility to contribute to the production capacity with lower or no net greenhouse gas emissions (without carbon sequestration technologies), increasing the flexibility and improving the economics of distributed and semi-centralized reforming. Electrolysis, thermocatalytic, and biological production can be easily adapted to on-site decentralized production of H₂, circumventing the need to establish a large and costly distribution infrastructure. Each of these H₂ production technologies, however, faces technical challenges, including conversion efficiencies, feedstock type, and the need to safely integrate H₂ production systems with H₂ purification and storage technologies.     

Mechanistic study of bio-oil catalytic steam reforming for hydrogen production: Acetic acid decomposition

To clarify the understanding of the mechanism of bio-oil catalytic steam reforming, we selected acetic acid as a typical bio-oil model compound to study its detailed behavior in decomposition over an active stepped Ni surface by density functional theory calculations. The adsorption geometries and energies of various intermediates were reported. Linear correlations between the adsorption energy and the number of hydrogen atoms removed for CH_xCOOH, CH_xCOO, and CH_x species (x = 1–3) were found, with increments of ?1.56, ?0.81, and ?1.80 eV, respectively. Thirty-seven possible elementary reactions of acetic acid decomposition were proposed, and their activation energies, reaction energies, rate constants, and equilibrium constants were calculated. Acetic acid dissociation likely started via α-carbon dehydrogenation, OH dehydrogenation, and dehydroxylation. Combined with microkinetic modeling, the most preferable decomposition pathway was suggested as CH₃COOH → CH₃CO → CO + CH₃. The rate-determining step was CH₃COOH dehydroxylation to CH₃CO with an activation energy of 0.68 eV and a rate constant of 3.82 × 10⁸ s^?1. The formation of CH₃COO was dominant at high temperatures, whereas its decomposition occurred with difficulty.     

Exergy analysis of hydrogen production via steam methane reforming

The performance of hydrogen production via steam methane reforming (SMR) is evaluated using exergy analysis, with emphasis on exergy flows, destruction, waste, and efficiencies. A steam methane reformer model was developed using a chemical equilibrium model with detailed heat integration. A base-case system was evaluated using operating parameters from published literature. Reformer operating parameters were varied to illustrate their influence on system performance. The calculated thermal and exergy efficiencies of the base-case system are lower than those reported in literature. The majority of the exergy destruction occurs due to the high irreversibility of chemical reactions and heat transfer. A significant amount of exergy is wasted in the exhaust stream. The variation of reformer operating parameters illustrated an inverse relationship between hydrogen yield and the amount of methane required by the system. The results of this investigation demonstrate the utility of exergy analysis and provide guidance for where research and development in hydrogen production via SMR should be focused.     

Production of synthesis gas by partial oxidation and steam reforming of biomass pyrolysis oils

As the lowest cost biomass-derived liquids, pyrolysis oils (also called bio-oils) represent a promising vector for biomass to fuels conversion. However, bio-oils require upgrading to interface with existing infrastructure. A potential pathway for producing fuels from pyrolysis oils proceeds through gasification, the conversion to synthesis gas. In this work, the conversion of bio-oils to syngas via catalytic partial oxidation over Rh–Ce is evaluated using two reactor configurations. In one instance, pyrolysis oils are oxidized in excess steam in a freeboard and passed over the catalyst in a second zone. In the second instance, bio-oils are introduced directly to the catalyst. Coke formation is avoided in both configurations due to rapid oxidation. H₂ and CO can be produced autothermally over Rh–Ce catalysts with millisecond contact times. Co-processing of bio-oil with methane or methanol improved the reactor operation stability.     

Underwater vehicle hydrogen production from methanol steam reforming using hydrogen peroxide

Methanol steam reforming (MSR) can supply hydrogen (H₂) to underwater vehicles equipped with a fuel cell. Low reaction temperatures ensure the composition of the reformed gas suitable for the H₂ purification unit and increase the design freedom of a reforming plant. However, such temperatures decrease the catalyst activity and thereby the methanol (MeOH) conversion and H₂ production. Herein, hydrogen peroxide (H₂O₂) was supplied with MeOH and water (H₂O) to ensure sufficient MeOH conversion and H₂ production at low temperatures. A tube reactor loaded with a commercial Cu/Zn catalyst was installed in an electric furnace maintained at 200–250 °C, and MeOH and 0 wt%, 11.88 wt%, 22.51 wt%, and 32.07 wt% H₂O₂ were supplied. When the furnace temperature was 200 °C, the MeOH conversion was 49.3% at 0 wt% H₂O₂ but 93.5% at 32.07 wt% H₂O₂. The effect of adding H₂O₂ was greater under the temperature conditions where the MeOH conversion was 100% or less. To analyze the effect of H₂O₂ addition on catalyst durability, the furnace was maintained at 200 °C, and the reactor was continuously operated for 110 h with 0 wt% and 32.07 wt% H₂O₂. The addition of H₂O₂ did not significantly decrease the Cu/Zn catalyst durability.