Hydrogen production via catalytic steam reforming of the aqueous fraction of bio-oil using nickel-based coprecipitated catalysts

Hydrogen production was studied in the catalytic steam reforming of a synthetic and a real aqueous fraction of bio-oil. Ni/Al coprecipitated catalysts with varying nickel content (23, 28 and 33 relative atomic %) were prepared by an increasing pH technique and tested during 2 h under different experimental conditions in a small bench scale fixed bed setup. The 28% Ni catalyst yielded a more stable performance over time (steam-to-carbon molar ratio, S/C = 5.58) at 650 °C and a catalyst weight/organic flow rate (W/m_org) ratio of 1.7 g catalyst min/g organic. Using the synthetic aqueous fraction as feed, almost complete overall carbon conversion to gas and hydrogen yields close to equilibrium could be obtained with the 28% Ni catalyst throughout. Up to 63% of overall carbon conversion to gas and an overall hydrogen yield of 0.09 g/g organic could be achieved when using the real aqueous fraction of bio-oil, but the catalyst performance showed a decay with time after 20 min of reaction due to severe coke deposition. Increasing the W/m_org ratio up to 5 g catalyst min/g organic yielded a more stable catalyst performance throughout, but overall carbon conversion to gas did not surpass 83% and the overall hydrogen yield was only ca. 77% of the thermodynamic equilibrium. Increasing reaction temperatures (600–800 °C) up to 750 °C enhanced the overall carbon conversion to gas and the overall yield to hydrogen. However, at 800 °C the catalyst performance was slightly worse, as a result of an increase in thermal cracking reactions leading to an increased formation of carbon deposits.     

Hydrogen production from supercritical water reforming of glycerol in an empty Inconel 625 reactor

Glycerol reforming was investigated under supercritical water conditions (450–575 °C, 250 bar). A feed containing 5 wt.% of glycerol was continuously fed to an empty Inconel 625 reactor. The products of the reaction were separated into gas and liquid phases in a condenser. At a feed rate of 2.15 g/min, the glycerol conversion significantly increased from 0.05 to 0.97 when increasing operating temperature from 450 to 575 °C. Although lowering the feed rate (i.e. increasing the residence time) could considerably improve the conversion, carbon formation became a problem especially at high operating temperatures (550–575 °C). The major gaseous products were hydrogen (approximately 60 mol%), carbon monoxide, carbon dioxide and methane with some traces of ethane, ethylene, propane, and propylene. Various liquid products were detected including acetaldehyde, acetol, methanol, acetic acid, propionaldehyde, allyl alcohol, acetone, acrolein, ethanol, ethylene glycol, and acrylic acid but the major liquid components were acetaldehyde and acetol. With a feed glycerol concentration of 2.5 wt.% and operating temperature of 525 °C, glycerol conversion of 0.91 and H₂ yield of 2.86 can be obtained without carbon formation. Finally, it was demonstrated that higher H₂ yield with much lower carbon formation was observed in supercritical water reforming (250 bar) compared to conventional steam reforming at 1 bar under similar temperatures.     

Integrated catalytic adsorption (ICA) steam gasification system for enhanced hydrogen production using palm kernel shell

This paper investigates the integrated catalytic adsorption (ICA) steam gasification of palm kernel shell for hydrogen rich gas production using pilot scale fluidized bed gasifier under atmospheric condition. The effect of temperature (600–750 °C) and steam to biomass ratio (1.5–2.5 wt/wt) on hydrogen (H₂) yield, product gas composition, gas yield, char yield, gasification and carbon conversion efficiency, and lower heating values are studied. The results show that H₂ hydrogen composition of 82.11 vol% is achieved at temperature of 675 °C, and negligible carbon dioxide (CO₂) composition is observed at 600 °C and 675 °C at a constant steam to biomass ratio of 2.0 wt/wt. In addition, maximum H₂ yield of 150 g/kg biomass is observed at 750 °C and at steam to biomass ratio of 2.0 wt/wt. A good heating value of product gas which is 14.37 MJ/Nm³ is obtained at 600 °C and steam to biomass ratio of 2.0 wt/wt. Temperature and steam to biomass ratio both enhanced H₂ yield but temperature is the most influential factor. Utilization of adsorbent and catalyst produced higher H₂ composition, yield and gas heating values as demonstrated by biomass catalytic steam gasification and steam gasification with in situ CO₂ adsorbent.     

Improvement of hydrogen production with thermophilic mixed culture from rice spent wash of distillery industry

Biohydrogen production processes were investigated using thermophilic bacterial consortia enriched from sludge of the anaerobic digester. A multiple parameter optimization viz. temperature, pH and substrate concentration was performed for maximization of hydrogen production. Heat shock pre-treatment followed by BES (2-bromo ethane sulfonate) treatment was done for the enrichment of hydrogen producing bacteria. Box–Behnken design and response surface methodology were adopted to investigate the mutual interaction among the process parameters. Experimental optimization of process parameters (60 °C, pH 6.5 and 10 g/L) gave the maximum hydrogen production and yield of 3985 mL/L and 2.7 mol/mol glucose respectively in the batch system which is higher than the reported value on UASB. These experimental parameters found concurrent with the values obtained from the theoretical model i.e. 58.4 °C, pH 6.6, 10.8 g/L and yield of 2.71 mol/mol glucose. At optimized conditions, maximum hydrogen production rate (R_m) of 850 mL/h, gas production potential (P) of 4551 mL/L and lag time (λ) of 1.98 h were determined using modified Gompertz equation. Using the optimum conditions, hydrogen production from rice spent wash was conducted in which hydrogen yield of 464 mL/g carbohydrate and hydrogen production rate of 168 mL/L h were obtained. PCR-DGGE profile showed that the thermophilic mixed culture was predominated with species closely affiliated to Thermoanaerobacterium sp.     

Synthesizing hydrogen from ammonia over Ru incorporated SiO2 type nanocomposite catalysts

In this study, Ruthenium incorporated SiO₂ type nanocomposite catalysts were prepared for CO_x free hydrogen production by using one-pot hydrothermal synthesis procedure. Experiments which were carried out under the flow of pure ammonia (300 ml/min) presented that 86% ammonia conversion was obtained at 500 °C over the catalyst having Ru/Si molar ratio of 0.060. Using promoter in the preparation of catalyst enhanced the catalytic activity especially for the ones prepared at low ruthenium loadings. While the catalyst that was prepared at a Ru/Si molar ratio of 0.010 without promoter gave negligible activity at 500 °C, the promoted one gave 33% conversion at 500 °C and 73% at 600 °C. Experiments were also repeated with lower feed flow rate values of ammonia such as 60 ml/min and 5 ml/min. It was seen that catalyst prepared at a Ru/Si molar ratio of 0.010 with promoter gave conversion value over 80% at 400 °C under the feed flow rate of 5 ml/min.     

Biohydrogen production from sugarcane bagasse hydrolysate by elephant dung: Effects of initial pH and substrate concentration

Pre-heated elephant dung was used as inoculum to produce hydrogen from sugarcane bagasse (SCB) hydrolysate. SCB was hydrolyzed by H₂SO₄ or NaOH at various concentrations (0.25-5% volume) and reaction time of 60 min at 121 °C, 1.5 kg/cm² in the autoclave. The optimal condition for the pretreatment was obtained when SCB was hydrolyzed by H₂SO₄ at 1% volume which yielded 11.28 g/L of total sugar (1.46 g glucose/L; 9.10 g xylose/L; 0.72 g arabinose/L). The maximum hydrogen yield of 0.84 mol H₂/mol total sugar and the hydrogen production rate of 109.55 mL H₂/L day were obtained at the initial pH 6.5 and initial total sugar concentration 10 g/L. Hydrogen-producing bacterium (Clostridium pasteurianum) and non hydrogen-producing bacterium (Flavobacterium sp.) were dominating species in the elephant dung and in hydrogen fermentation broth. Sporolactobacillus sp. was found to be responsible for a low hydrogen yield obtained.     

Hydrothermal gasification of pure and crude glycerol in supercritical water: A comparative study

A comparative gasification study between pure glycerol and two different kinds of crude glycerol is conducted in supercritical water under various operating parameters to investigate the effect of different compositions in crude glycerol on the gasification behaviors. Among various types of impurities in the crude glycerol, fatty acid methyl esters (FAMEs) exhibit a negative effect on the gas yield and gasification efficiency of crude glycerol in a batch apparatus due to the enhanced tar/char formation. At 650 °C and 5 wt%, gasification in a continuous apparatus exhibits H₂ yields of 26.44 and 35.85 mmol/g feed in 1 min for both types of crude glycerol, which could not be achieved by the batch system even with the reaction time extended up to 120 min. A shorter duration in the non-supercritical state may be the dominant parameter that leads to complete conversion of FAMEs and total gasification of crude glycerol using the continuous system.     

Improved yield parameters in catalytic steam gasification of forestry residue; optimizing biomass feed rate and catalyst type

The catalytic gasification (900 °C) of forestry industry residue (Eucalyptus saligna) was laboratory-studied. Biomass feed rate and type and amount of catalyst were assayed for their effect on the gasified product composition and the overall energy yield of the gasification reaction. The use of a calcined dolomite catalyst resulted in a combustible gas mixture of adequate calorific power (10.65 MJ m^?3) for use as fuel, but neither the product gas composition nor the energy yield varied significantly with widely different amounts of the catalyst (2 g and 20 g). The use of NiO-loaded calcined dolomite catalysts did not affect the product gas composition significantly but led to a 30% increase in the total product gas volume and to a reduction in the rate of tar and char formation. The catalyst loaded with the smallest amount of NiO studied (0.4 wt%. Ni/Dol) led to the highest energy yield (21.50 MJ kg^?1 on a dry-wood basis) based on the use of the gasified product as fuel. The gasified product was found to have an adequate H₂/CO molar ratio and H₂ content for use as synthesis gas source and partial source of H₂.     

Decomposition characteristics of softwood lignophenol under hydrothermal conditions

Lignophenol is a novel lignin-based functional polymer. Hydrothermal decomposition of ligno-p-cresol derived from softwood (Douglas fir) was studied from 300 to 400 °C as a candidate technology for modification of the molecular structure and the recovery of monophenols. Ligno-p-cresol was promptly depolymerized probably by hydrolysis of aryl ether linkages and the half was converted to ether-soluble compounds at 300 °C for 10 min. With increasing temperature and reaction time, the yields of char and gas were increased, indicating the acceleration of carbonization and decomposition of monophenols. The monophenols obtained were mainly p-cresol and guaiacol. Their yields only exceed 10% at 365 °C and 60 min probably due to the inefficient pyrolysis of 1,1-bis aryl structures.     

A study on bioethanol production from cashew apple pulp and coffee pulp waste

Bioethanol production from dry cashew apple pulp and coffee pulp was investigated. The pulp was digested with 2% sulfuric acid and subjected to high pressure (15 psi) cooking at 120 °C for 10 min followed by further 1 and a half hour pressure cooking at 90 °C to solubilize the pulp. Solubilized pulp was filtered and the debris on the filter paper was washed with minimum quantity of distilled water and then oven dried to find the weight of the insoluble lignin mass. Total sugar content in squeezed and dried cashew apple pulp (CAP), dry coffee pulp (DCP) and wet coffee pulp (WCP) was found to be 2.12, 1.62 and 0.62 g/100 ml of hydrolyzate. Reducing sugar content in squeezed CAP, DCP and WCP was found to be 0.14, 0.71and 0.23g/100 ml of hydrolyzate. Filtrate was neutralized with thick suspension of calcium hydroxide slurry until the pH reaches to 6.0. Neutralized slurry was kept at lab temperature overnight and the supernatant was decanted through filter paper. To 150 ml of filtrate yeast (Saccharomyces creviciae) was added at a concentration of 5.0 g/l concentration and subjected to fermentation for 48 h at 30 °C in a shaker incubator at 120 rpm. Ethanol content in the fermented broth was estimated by titrimetric and gas chromatographic method. Ethanol yield in the fermented broth was found to be 0.5, 0.46 and 0.46 g/g of sugar in squeezed CAP, DCP and WCP. Theoretical ethanol yield (Y_max%) of squeezed CAP, DCP and WCP was found to be 46, 9.35 and 40% respectively.     

Optimization and characterization studies on bio-oil production from palm shell by pyrolysis using response surface methodology

In this work palm shell waste was pyrolyzed to produces bio-oil. The effects of several parameters on the pyrolysis efficiency were tested to identify the optimal bio-oil production conditions. The tested parameters include temperature, N₂ flow rate, feed-stock particle size, and reaction time. The experiments were conducted using a fix-bed reactor. The efficient response surface methodology (RSM), with a central composite design (CCD), were used for modeling and optimization the process parameters. The results showed that the second-order polynomial equation explains adequately the non-linear nature of the modeled response. An R² value of 0.9337 indicates a sufficient adjustment of the model with the experimental data. The optimal conditions found to be at the temperature of 500 °C, N₂ flow rate of 2 L/min, particle size of 2 mm and reaction time of 60 min and yield of bio-oil was approximately obtained 46.4 wt %. In addition, Fourier Transform infra-red (FT-IR) spectroscopy and gas chromatography/mass spectrometry (GC-MS) were used to characterize the gained bio-oil under the optimum condition.     

Biohydrogen production from hydrolyzed waste wheat by dark fermentation in a continuously operated packed bed reactor: The effect of hydraulic retention time

The aim of the study is biohydrogen production from hydrolyzed waste wheat by dark fermentation in a continuously operated up-flow packed bed reactor. For this purpose, the effect of hydraulic retention time (HRT) on the rate (R_H2) and yield (Y_H2) of hydrogen gas formation were investigated. In order to determine the most suitable hydraulic retention time yielding the highest hydrogen formation, the reactor was operated between HRT = 1 h and 8 h. The substrate was the acid hydrolyzed wheat powder (AHWP). Waste wheat was sieved down to 70 μm size (less than 200 mesh) and acid hydrolyzed at pH = 2 and 90 °C in an autoclave for 15 min. The sugar solution obtained from hydrolysis of waste wheat was used as substrate at the constant concentration of 15 g/L after neutralization and nutrient addition for biohydrogen production by dark fermentation. The microbial growth support particle was aquarium biological sponge (ABS). Heat-treated anaerobic sludge was used as inoculum. Total gas volume and hydrogen percentage in total gas, hydrogen gas volume, total sugar and total volatile fatty acid concentrations in the feed and in the effluent of the system were monitored daily throughout the experiments. The highest yield and rate of productions were obtained as Y_H2 = 645.7 mL/g TS and R_H2 = 2.51 L H₂/L d at HRT = 3 h, respectively.     

Pyrolysis of Alternanthera philoxeroides (alligator weed): Effect of pyrolysis parameter on product yield and characterization of liquid product and bio char

In the present work, fast pyrolysis of Alternanthera philoxeroides was evaluated with a focus to study the chemical and physical characteristics of bio-oil produced and to determine its practicability as a transportation fuel. Pyrolysis of A.philoxeroides was conducted inside a semi batch quartz glass reactor to determine the effect of different operating conditions on the pyrolysis product yield. The thermal pyrolysis of A. philoxeroides were performed at a temperature range from 350 to 550 °C at a constant heating rate of 25 °C/min & under nitrogen atmosphere at a flow rate of 0.1 L/min, which yielded a total 40.10 wt.% of bio-oil at 450 °C. Later, some more sets of experiments were also performed to see the effect on pyrolysis product yield with change in operating conditions like varying heating rates (50 °C/min, 75 °C/min & 100 °C/min) and different flow rates of nitrogen (0.2, 0.3, 0.4 & 0.5 L/min). The yield of bio-oil during different heating rate (25, 50, 75 and 100 °C/min) was found to be more (43.15 wt.%) at a constant heating rate of 50 °C/min with 0.2 L/min N₂ gas flow rate and at a fixed pyrolysis temperature of 450 °C. The High Heating Value (HHV) value of bio-oil (8.88 MJ/kg) was very less due to presence of oxygen in the biomass. However, the high heating value of bio-char (20.41 MJ/kg) was more, and has the potential to be used as a solid fuel. The thermal degradation of A. philoxeroides was studied in TGA under inert atmosphere. The characterization of bio-oil was done by elemental analyser (CHNS/O analyser), FT-IR, & GC/MS. The char was characterized by elemental analyser (CHNS/O analysis), SEM, BET and FT-IR techniques. The chemical characterization showed that the bio-oil could be used as a transportation fuel if upgraded or blended with other fuels. The bio-oil can also be used as feedstock for different chemicals. The bio-char obtained from A. philoxeroides can be used for adsorption purposes because of its high surface area.     

Fermentative bioenergy production from distillers grains using mixed microflora

The feasibility of hydrogen production from distillers grains substrate, an industrial cellulosic waste, was investigated. A substrate concentration of 80 g/L gave the maximum production at 50 °C and pH of 6.0 using sewage sludge. Four controllable factors with three levels: seed sludge (two sewage sludges and cow dung), temperature (40, 50, and 60 °C), pH (6, 7 and 8) and seed pretreatment (none, heat, and acid) were selected in Taguchi experimental design to optimize fermentation conditions. The peak hydrogen and ethanol productions were found with heat-treated cow dung seed, substrate concentration 80 g/L, 50 °C and pH 6. The peak hydrogen production rate and hydrogen yield were 7.9 mmol H₂/L/d and 0.40 mmol H₂/g-COD respectively whereas the peak ethanol production was 3050 mg COD/L and rate 0.22 g EtOH/L/d. A total bioenergy yield of 41 J/g substrate was obtained which was 21% and 79% from hydrogen and ethanol respectively.     

Utilization possibilities of palm shell as a source of biomass energy in Malaysia by producing bio-oil in pyrolysis process

Agriculture residues such as palm shell are one of the biomass categories that can be utilized for conversion to bio-oil by using pyrolysis process. Palm shells were pyrolyzed in a fluidized-bed reactor at 400, 500, 600, 700 and 800 °C with N₂ as carrier gas at flow rate 1, 2, 3, 4 and 5 L/min. The objective of the present work is to determine the effects of temperature, flow rate of N₂, particle size and reaction time on the optimization of production of renewable bio-oil from palm shell. According to this study the maximum yield of bio-oil (47.3 wt%) can be obtained, working at the medium level for the operation temperature (500 °C) and 2 L/min of N₂ flow rate at 60 min reaction time. Temperature is the most important factor, having a significant positive effect on yield product of bio-oil. The oil was characterized by Fourier Transform infra-red (FT-IR) spectroscopy and gas chromatography/mass spectrometry (GC-MS) techniques.     

Hydrogen-rich gas production by steam gasification of char derived from cyanobacterial blooms (CDCB) in a fixed-bed reactor: Influence of particle size and residence time on gas yield and syngas composition

Char derived from cyanobacterial blooms (CDCB), by-product of fast pyrolysis of cyanobacterial blooms from Dianchi Lake (Yunnan Province, China) at a final pyrolysis temperature of 500 °C were used as feedstock material in this study. Steam gasification characteristics of CDCB were investigated in a fixed-bed reactor to evaluate the effect of particle size (below 0.15 mm, 0.15–0.3 mm, 0.3–0.45 mm, 0.45–0.9 mm, 0.9–3 mm) and solid residence time (3, 6, 9, 12, 15 min) on gas yield and composition, and experiments were carried out at bed temperature range of 600–850 °C, steam flow rate of 0.178 g/min. The results showed that solid residence time played an important role on steam gasification process, while particle size presented less effect on gasification process; proper particle size and longer residence time were favorable for dry gas yield and carbon conversion efficiency (CCE). At the same time, higher reaction temperature reduced influence of particle size on gasification process, and smaller particle size required less residence time for reaction completed. Maximum dry gas yield and CCE reached 1.84 Nm³ kg⁻¹ and 98.82%, respectively, achieved at a temperature of 850 °C, flow rate of 0.178 g/min, solid residence time of 15 min and particle size range of 0.45–0.9 mm.     

Optimization of temperature and light intensity for improved photofermentative hydrogen production using Rhodobacter capsulatus DSM 1710

Photofermentative hydrogen production is influenced by several parameters, including feed composition, pH levels, temperature and light intensity. In this study, experimental results obtained from batch cultures of Rhodobacter capsulatus DSM 1710 were analyzed to locate the maximum levels for the rate and yield of hydrogen production with respect to temperature and light intensity. For this purpose, a 3^k general full factorial design was employed, using temperatures of 20, 30 and 38 °C and light intensities of 100, 200 and 340 W/m². ANOVA results confirmed that these two parameters significantly affect hydrogen production. Surface and contour plots of the regression models revealed a maximum hydrogen production rate of 0.566 mmol H₂/L/h at 27.5 °C and 287 W/m² and a maximum hydrogen yield of 0.326 mol H₂/mol substrate at 26.8 °C and 285 W/m². Validation experiments at the calculated optima supported these findings.     

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.     

Kinetics of cotton cellulose hydrolysis using concentrated acid and fermentative hydrogen production from hydrolysate

The kinetics of cotton cellulose hydrolysis using concentrated sulfuric acid and the performance of fermentative hydrogen production from the hydrolysate in the batch system was carried out in this study. Effects of sulfuric acid concentrations, cotton cellulose concentrations and operating temperatures on the cotton cellulose hydrolysis were investigated. It was found that cotton cellulose can dissolve completely in sulfuric acid concentration above 55% (by volume) at room temperature. The reduced sugar yields were varied from 64.3 to 73.9% (g R-sugar/g cotton cellulose) with the initial cotton cellulose concentrations of 30-70 g/L at a temperature of 40 °C.The reduced sugar concentrations and the initial pH of biohydrogen production were investigated at 37 °C. It was found that the optimal values of the hydrogen yield and substrate utilization were 0.95 mol H₂/mol R-sugar and 98% with an initial pH of 8.2, when substrate concentration was fixed at 20 g R-sugar/L. The maximum hydrogen yield was 0.99 mol H₂/mol R-sugar at a substrate concentration of 15 g R-sugar/L. Using the Gompertz Equation Model simulation, the maximum hydrogen production rate was 253 mL H₂/h/L at a substrate of 30 g/L and initial pH of 8.4.     

Insitu upgradation of biocrude vapor generated from non-edible oil cake's hydrothermal conversion over aluminated mesoporous catalysts

In this work, biocrude vapors generated from hydrothermal conversion of Pongammia pinnata cake using high pressure reactor at 400 °C and 25 kg/cm² were upgraded over three mesoporous catalyst namely SBA-15, KIT-6 and FDU-12. The catalysts were synthesized, aluminated and characterized using X-Ray Diffraction, N₂ adsorption-desorption, SEM techniques. A decrease in the surface area was observed on all three mesoporous catalyst after alumina loading with negligible effect on the pore diameter. Purely siliceous catalysts were found to give negligible effect on the yield of different product phases. Alumina supported SBA-15 (SAR 30) was observed as the suitable catalyst as compared to Al/FDU-12 (SAR 30) and Al/KIT-6 (SAR 30) for maximizing the biocrude yield with low heavy hydrocarbons (46.3 ± 2.2%), polyaromatic hydrocarbons (17.1%) and acidic compounds (9.1%) content. Therefore series of SBA-15 were synthesized by varying silicon to alumina ratio between 20 and 50 for maximizing hydrocarbons with boiling cut fractions between 195 and 317 °C corresponding to gasoline range hydrocarbons. Al/SBA-15(SAR 40) was found to give highest biocrude yield (∼34.8%) with highest selectivity towards gasoline fraction (23.7 ± 1.9%). GC/MS analysis was used to confirm the presence of aliphatic and aromatics. Highest asphaltene content was observed with Al/SBA-15 (SAR 50).