mL Of H2 Research Articles

Additively Manufactured Silicone Polymer Composite with High Hydrogen Getter Content and Hydrogen Absorption Capacity.

Hydrogen getters consisting of 1,4-bis[phenylethynyl] benzene (DEB) and a carbon-supported palladium catalyst (Pd/C) have been used to mitigate the accumulation of unwanted hydrogen gas in a sealed system. Here, we report the formulation of a composite resin consisting of silicone polymer plus DEB-Pd/C as an active getter material and the additive manufacturing of silicone getter composites with a high getter content (up to 50 wt %). NMR and DSC studies suggest no reaction between the silicone polymer resin and DEB even at elevated curing temperatures (75 °C). Getter composites with varying amounts of getter and filler were formulated, and their rheological properties were studied. The two composite resins with good printability parameters and different getter contents were chosen to make 3D-printed samples. The hydrogen absorption capacity of these samples was studied at a low hydrogen pressure of 750 mTorr of pure hydrogen. The getter composite with 50 wt% of getter showed normalized DEB conversion of 83%, with the hydrogen adsorption capacity of 100.2 mL of H2 per gram of polymer getter composite.

Improving solar fuel production performance from H2O and CO2 thermochemical dissociation using custom-made reticulated porous ceria

Thermochemical CO2- and H2O-splitting cycles for sustainable fuel generation were investigated by using custom-made reticulated ceria foams integrated in a solar-heated cavity reactor. A parametric study revealed the suitable conditions to produce H2/CO with maximum fuel rates and yields per unit mass of redox material. Various operating parameters such as the total pressure during the reduction step, the gas inlet flowrates, the temperature, or the reactive gas content during the oxidation step were studied in detail. A series of on-sun experiments including more than 20 cycles under different cycling conditions were carried out with relevant performance repeatability and stability. With a ceria foam reduction temperature in the range 1400–1470 °C and a reduction pressure of 103 mbar, the ceria foams produced 281 μmol of H2 and 332 μmol of CO per gram of material during oxidation below 1000 °C under cooling with a maximum production rate of 3.0 mL/min.g and 10.2 mL/min.g, respectively. Direct syngas production was also evidenced during on-sun experiments with simultaneous H2O- and CO2-splitting, which yielded a H2:CO ratio ranging from 0.7 to 1.14. The dual-scale porous ceria structures were characterized using X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis to confirm material thermal stability during cycling. Finally, optimization of fuel production capacity was achieved by maximizing the total amount of ceria foam loaded into the reactor, yielding 667 mL of CO (409 μmol/g) and 513 mL of H2 (314 μmol/g) per cycle. A maximum solar-to-fuel efficiency of 10.1% was calculated for CO2-splitting vs. 4.9% for H2O-splitting cycle. This study thus demonstrated noteworthy fuel production performance in an efficient monolithic reactor under real concentrated solar radiation, from highly reactive customized ceria foams.

Thermochemical production of green hydrogen using ferrous scrap materials

Thermochemical water splitting is one of the methods to produce green hydrogen. In this study, metal scrap is used to split water by thermochemical process in a packed-bed reactor. Hydrogen production conditions are optimized by varying the particle size of the metal wastes in the range of 250 μm to greater than 1000 μm and the temperatures from 900 °C to 1200 °C. The maximum yield of hydrogen obtained is ∼500 mL of H2 per gram of the scrap sample. This study demonstrates that the discarded metal wastes can be utilized as feed-materials for thermochemical production of green hydrogen. The process has good conversion efficiency and is a promising solution for both metal waste management and the production of green hydrogen. Medium size metal particles show higher hydrogen production capacity compared to both smaller (<250 μm) and larger (600–1180 μm) size particles.

Partial inhibition of the inter-photosystem electron transfer at cytochrome b6f complex promotes periodic surges of hydrogen evolution in Chlamydomonas reinhardtii

Periodic surges of H2 evolution were observed in the wild-type strain CC-5325 of the green unicellular alga Chlamydomonas reinhardtii in the presence of the electron transport inhibitors dibromo-6-isopropyl-3-methyl-1,4-benzoquinone (DBMIB, 3.5 μM) and 2,4-dinitrophenylether and iodonitrothymol (DNP-INT, 0.6 μM). Addition of DBMIB partly inhibited the electron transfer from Cytochrome b6f complex to Photosystem I, over-reduced the plastoquinone pool, gradually inhibited photosystem II and created anoxic conditions in cells. During 30 days of anaerobic incubation, continues H2 photoproduction with a minimum rate of 1 ml/L of culture per day was accompanied with additional outbursts of H2 evolution. The first noticeable peak of H2 evolution was observed on day 6 of incubation, with maximum rate of 23 ml of H2 per L of culture per day. It was repeated on day 9 and day 22 with the 2 and 4 times lower rates respectively. Addition of DNP-NT showed similar effect by inducing the H2 photoproduction for 15 days, albeit at much lower rates. Contribution of the direct and indirect pathways to the H2 production is shown by fluorescence, thermoluminescence and electron paramagnetic resonance spectroscopy. It is proposed that photosynthetic electron transport in combination with photorespiration, chlororespiration and starch accumulation can switch on and off between photosynthetic, H2 producing and survival modes of cell metabolism. Controlled switching between these modes could potentially maintain the long lasting photosynthetic H2 production in the wild-type of Chlamydomonas.

Base- or acid-assisted polystyrene plastic degradation in supercritical CO2.

The online version contains supplementary material available at 10.1007/s42768-023-00139-1.

Electrospun NiPd Nanoparticles Supported on Polymer Membrane Nanofibers as an Efficient Catalyst for NaBH4 Dehydrogenation.

Sodium borohydride (SBH) hydrolysis in the presence of cheap and efficient catalysts has been proposed as a safe and efficient method for generating clean hydrogen energy for use in portable applications. In this work, we synthesized bimetallic NiPd nanoparticles (NPs) supported on poly(vinylidene fluoride-co-hexafluoropropylene) nanofibers (PVDF-HFP NFs) via the electrospinning approach and reported an in-situ reduction procedure of the NPs being prepared by alloying Ni and Pd with varying Pd percentages. The physicochemical characterization provided evidence for the development of a NiPd@PVDF-HFP NFs membrane. The bimetallic hybrid NF membranes exhibited higher H2 production as compared to Ni@PVDF-HFP and Pd@PVDF-HFP counterparts. This may be due to the synergistic effect of binary components. The bimetallic Ni1-xPdx(x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3)@PVDF-HFP nanofiber membranes exhibit composition-dependent catalysis, in which Ni75Pd25@PVDF-HFP NF membranes demonstrate the best catalytic activity. The full H2 generation volumes (118 mL) were obtained at a temperature of 298 K and times 16, 22, 34 and 42 min for 250, 200, 150, and 100 mg dosages of Ni75Pd25@PVDF-HFP, respectively, in the presence of 1 mmol SBH. Hydrolysis utilizing Ni75Pd25@PVDF-HFP was shown to be first order with respect to Ni75Pd25@PVDF-HFP amount and zero order with respect to the [NaBH4] in a kinetics study. The reaction time of H2 production was reduced as the reaction temperature increased, with 118 mL of H2 being produced in 14, 20, 32 and 42 min at 328, 318, 308 and 298 K, respectively. The values of the three thermodynamic parameters, activation energy, enthalpy, and entropy, were determined toward being 31.43 kJ mol-1, 28.82 kJ mol-1, and 0.057 kJ mol-1 K-1, respectively. It is simple to separate and reuse the synthesized membrane, which facilitates their implementation in H2 energy systems.

Electrospun Co Nanoparticles@PVDF-HFP Nanofibers as Efficient Catalyst for Dehydrogenation of Sodium Borohydride.

Metallic Co NPs@poly(vinylidene fluoride-co- hexafluoropropylene) nanofibers (PVFH NFs) were successfully synthesized with the help of electrospinning and in situ reduction of Co2+ ions onto the surface of PVFH membrane. Synthesis of PVFH NFs containing 10, 20, 30, and 40 wt% of cobalt acetate tetrahydrate was achieved. Physiochemical techniques were used to confirm the formation of metallic Co@PVFH NFs. High catalytic activity of Co@PVFH NFs in the dehydrogenation sodium borohydride (SBH) was demonstrated. The formulation with 40 wt% Co proved to have the greatest performance in comparison to the others. Using 1 mmol of SBH and 100 mg of Co@PVFH NFs, 110 mL of H2 was produced in 19 min at a temperature of 25 °C, but only 56, 73, and 89 mL were produced using 10, 20, and 30 wt% Co, respectively. With the rise of catalyst concentration and reaction temperature, the amount of hydrogen generated increased. By raising the temperature from 25 to 55 °C, the activation energy was lowered to be 35.21 kJ mol-1 and the yield of H2 generation was raised to 100% in only 6 min. The kinetic study demonstrated that the reaction was pseudo-first order in terms of the amount of catalyst utilized and pseudo-zero order in terms of the SBH concentration. In addition, after six cycles of hydrolysis, the catalyst showed outstanding stability. The suggested catalyst has potential applications in H2 generation through hydrolysis of sodium borohydride due to its high catalytic activity and flexibility of recycling.

Simultaneous Production of Biohydrogen (bioH2) and Poly-Hydroxy-Alkanoates (PHAs) by a Photoheterotrophic Consortium Bioaugmented with Syntrophomonas wolfei

Mixed cultures represent better alternatives to ferment organic waste and dark fermentation products in anerobic conditions because the microbial associations contribute to electron transfer mechanisms and combine metabolic possibilities. The understanding of the microbial interactions in natural and synthetic consortia and the strategies to improve the performance of the processes by bioaugmentation provide insight into the physiology and ecology of the mixed cultures used for biotechnological purposes. Here, synthetic microbial communities were built from three hydrogen (bioH2) and poly-hydroxy-alkanoates (PHA) producers, Clostridium pasteurianum, Rhodopseudomonas palustris and Syntrophomonas wolfei, and a photoheterotrophic mixed consortium C4, and their performance was evaluated during photofermentation. Higher hydrogen volumetric production rates (H2VPR) were determined with the consortia (28–40 mL/Lh) as compared with individual strains (20–27 mL/Lh). The designed consortia reached the highest bioH2 and PHA productions of 44.3 mmol and 50.46% and produced both metabolites simultaneously using dark fermentation effluents composed of a mixture of lactic, butyric, acetic, and propionic acids. When the mixed culture C4 was bioaugmented with S. wolfei, the bioH2 and PHA production reached 32 mmol and 50%, respectively. Overall, the consumption of organic acids was above 50%, which accounted up to 55% of total chemical oxygen demand (COD) removed. Increased bioH2 was observed in the condition when S. wolfei was added as the bioaugmentation agent, reaching up to 562 mL of H2 produced per gram of COD. The enhanced production of bioH2 and PHA can be explained by the metabolic interaction between the three selected strains, which likely include thermodynamic equilibrium, the assimilation of organic acids via beta-oxidation, and the production of bioH2 using a proton driving force derived from reduced menaquinone or via electron bifurcation.

Production of Hydrogen by Purple Non-Sulfur Bacteria Rhodopseudomonas yavorovii IMV B-7620

Hydrogen production by microorganisms is studied by using different sources of carbon for their cultivation. Purple non-sulfur bacteria are capable of producing molecular hydrogen phototrophically with the simultaneous accumulation of biomass on organic substrates that may be waste from various industries. That fact makes the study of this group of microorganisms very much promising. The aim. The determination of the ability of purple non-sulfur bacteria Rhodopseudomonas yavorovii IMV B-7620 to produce hydrogen consuming different organic substrates and their effects on the main metabolic indicators of culture growth. Methods. Bacteria were grown in 100 mL glass jars in liquid modified ATCC No. 1449 medium for 14 days at temperature +27...+30ºC and at constant light (200 lux). Biomass accumulation and hydrogen production in the cultivation medium were determined using sodium acetate (12 and 36 mM), malate (12 and 36 mM), succinate (36 mM), glucose (36 mM), starch (36 mM), sodium citrate (36, 60, 90 mM). Biomass was determined turbidimetrically, the composition of the gas phase was determined using a gas chromatograph LHM-8-MD, redox potential and pH were estimated potentiometrically. The volume of gas synthesized was measured on a syringe scale. Determination of the content of organic acids in the culture liquid was analyzed by high performance liquid chromatography. Results. The utilization of organic compounds (malate, glucose, starch, sodium citrate) by R. yavorovii IMV B-7620 is accompanied by hydrogen synthesis. Under the growth with sodium acetate, bacteria produce small amounts of succinate. The malate metabolism results in the production of small amounts of fumarate on the 7th day of cultivation and isocitrate on the 10th day of cultivation. On the 14th day of cultivation, the cultural liquid contains a small amount of succinate. On the 14th day of cultivation, R. yavorovii IMV B-7620 produces 7.64±0.04% of hydrogen in the medium with malate (36 mM). However, the maximum concentration of hydrogen in the gas phase (21.26±0.08%) was gained on the 14th day of cultivation in the medium with sodium citrate. The maximum concentration of H2 in the gas phase during the growth in the medium with sodium citrate (60 mM) and NH4+ was 27.83±5.46% on the 7th day of cultivation and 35.69±0.40% with increasing concentration of sodium citrate up to 90 mM on the 10th day of cultivation. The total volume of hydrogen was 25.54±0.49 mL of H2 during the growth of R. yavorovii IMV B-7620 in the medium with 90 mM sodium citrate and NH4+. That is 1.5 times more than the amount of H2 produced during the growth of bacteria in the medium with 60 mM sodium citrate with the addition of NH4+. Conclusion. Purple non-sulfur bacteria R. yavorovii IMV B-7620 synthesize hydrogen during photofermentation of organic compounds. Bacteria were isolated from the water of Yavoriv Lake (Lviv region, Ukraine) formed as a result of flooding of the sulfur quarry. Bacteria consume sodium citrate, malate, glucose, starch and emit hydrogen. The total volume of hydrogen during the growth of R. yavorovii IMV B-7620 in the medium with 90 mM sodium citrate and NH4+ is 25.54±0.49 mL H2.

Hydrogen Production via Activated Waste Aluminum Cans and Its Potential for Methanation

The production of hydrogen via aluminum waste can powder (AWCP) prepared via disintegration and mechanochemical activation using metals was explored. AWCP and its composites were reacted in 1 M NaOH to produce hydrogen at standard temperature (25 °C) condition. Ternary AWCP (3% Sn–3% Mg) composite produced the highest amount of H2 (660 mL/0.5 g in 660 s) in terms of weight percentage of AWCP used as compared to the best binary AWCP (3% Sn) with 680 mL of H2 produced in 240 s. The activation metals contributed microgalvanic activity in AWCP, which in result yielded higher hydrolysis of AWCP. The undoped AWCP, binary, and ternary composites were tested for batch methanation at 220 °C using CO2 gas and Ni based catalyst. H2 produced from aluminum–water reaction was successfully used to produce CH4 via continuous methanation process. However, not all the H2 produced participated in the reaction. This was mainly due to the role of gas hourly space velocity and the performance of the catalyst. Undoped AWCP performed better than binary and ternary composite despite higher amount H2 produced due to the gas hourly space velocity. The potential of AWCP as a raw material for H2 production and simultaneous methanation has led to a promising solution of producing clean, sustainable, and economical energy for the future.

Biohydrogen production from thermochemically pretreated corncob using a mixed culture bioaugmented with Clostridium acetobutylicum

Bovine ruminal fluid (BRF) bioaugmented with Clostridium acetobutylicum (Clac) was assessed for hydrolyzing cellulose and produce biohydrogen (BioH2) simultaneously from pretreated corncob in a single step, without the use of external hydrolytic biocatalysts. The corncob was pretreated using three thermochemical methods: H2SO4 2%, 160 °C; NaOH 2%, 140 °C; NaOCl 2%, 140 °C; autohydrolysis: H2O, 190 °C. Subsequently, BioH2 production was carried out using the pretreated material with the highest digestibility applying a Taguchi experimental array to identify the optimal operating conditions. The results showed a higher glucose released from pretreated corncob with H2SO4 (134.7 g/L) compared to pretreated materials by autohydrolysis, NaOH and NaOCl (123 g/L, 89.8 g/L and 52.9 g/L, respectively). The mixed culture was able to hydrolyze the pretreated corncob and produce 575 mL of H2 (at 35 °C, pH 5.5, 1:2 ratio of BRF:Clac and 5% of solids loading) equivalent to 132 L H2/Kg of biomass.

Sustained photobiological hydrogen production by Chlorella vulgaris without nutrient starvation

This article describes the ability of the Chlorella vulgaris BEIJ strain G-120 to produce hydrogen (H2) via both direct and indirect pathways without the use of nutrient starvation. Photobiological H2 production reached a maximum rate of 12 mL H2 L−1 h−1, corresponding to a light conversion efficiency (light to H2) of 7.7% (average 3.2%, over the 8-day period) of PAR, (photosynthetically active irradiance). Cells presented a maximum in vivo hydrogenase activity of 25.5 ± 0.2 nmoles H2 μgChl−1 h−1 and the calculated in vitro hydrogenase activity was 830 ± 61 nmoles H2 μgChl−1 h−1. The strain is able to grow either heterotrophically or photo autotrophically. The total output of 896 mL of H2 was attained for illuminated culture and 405 mL for dark cultures. The average H2 production rate was 4.98 mL L−1 h−1 for the illuminated culture and 2.08 mL L−1 h−1 for the one maintained in the dark.

Hydrogen Production by Dark Fermentation Process: Effect of Initial Organic Load

The treatment of residual biomass through the dark fermentation (DF) process is presented as a sustainable alternative, where bio-hydrogen is produced, which has a high energy potential, and bio-based sub-products. Consequently, this work aimed to determine the maximum organic load for the production of bio-hydrogen, from residual biomass available in Colombia. An experimental design was constructed to determine the biochemical hydrogen potential (BHP) of mixtures composed of three substrates: pig manure (PM), cocoa mucilage (CCM), and coffee mucilage (CFM). The design managed two independent variables, the organic load (10 gVS/l, 20 gVS/l, 30 gVS/l, 40 g VS/l, and 50 gVS/l), which were determined according to the physicochemical characterization of the substrates, and the S/X evaluated on two levels 1:1 and 1:2. The experiments were carried under mesophilic conditions (±35°C), a C/N ratio of 35, and a pH of 5.5 was fixed. As a result, five mixtures were evaluated, plus five targets. The reactors were erlenmeyers of 250mL, hermetically sealed, heated, and stirred in a hot plate. The tests were allowed to run until the detection of CH4; daily monitoring with a Biogas 5000® portable gas analyser did this. Following the determination of the physicochemical characteristics of the effluent, total solids (TS), volatile solids (VS), proteins, and chemical oxygen demand COD were analysed for each of the reactors. The results show that the organic load of 10gSV/L and the S/X of 1 has the highest production rate with 232 mL of H2, with a production of volatile fatty acids (VFA) of 4040mg COD/L, and a VS removal percentage of 84%. The removal of VS and the VFA allows suggesting secondary processes associated with bio-refinery schemes, for a more significant elimination of volatile solids and the obtaining of other value-added by-products.

Hydrothermal Liquefaction and Photocatalytic Reforming of Pinewood (Pinus ponderosa)-Derived Acid Hydrolysis Residue for Hydrogen and Bio-oil Production

Pretreatment of lignocellulosic biomass (LCB) is a prerequisite for downstream bioconversion of its cellulosic components to second-generation biofuels. Acid hydrolysis pretreatment separates most of the hemicellulose and cellulose from lignin. However, the lignin-rich acid hydrolysis residue (AHR) may contain 20–50 wt % feedstock biomass. To improve the economics of LCB-based biorefinery, the AHR needs to be valorized. In this study, we have performed hydrothermal liquefaction (HTL) of AHR derived from the dilute acid treatment of pinewood for H₂ and bio-oil generation. A slurry of AHR at a biomass-to-water ratio of 1:30 was hydrothermally liquefied in the presence of a homogeneous Ni(NO₃)₂ catalyst at 250, 275, and 300 °C. About 16 wt % bio-oil and 51 mL of H₂ were generated at 300 °C and 60 min into the reaction. Based on elemental analysis, the higher heating value of bio-oil was found to be 29.8 MJ/kg. The aqueous coproduct generated during the HTL reaction was treated with activated carbon and subjected to the photocatalytic reforming (PR) process in the presence of a Pt/TiO₂ catalyst that produced an additional 90 mL of H₂ at NTP conditions. Preliminary calculations were performed to understand the energy recovery in terms of the products generated based on the total energy consumed for both HTL and PR processes.

Nanoporous Microspheres of Co-Zn-S as Catalysts for Oxygen Evolution by Water Splitting and Hydrogen Generation by Ammonia Borane Hydrolysis

The nanoporous microspheres of Co-Zn-S were synthesized by a solvothermal method. The as-obtained Co-Zn-S microspheres, as a non-noble metal catalyst, exhibited highly electrocatalytic activity for oxygen evolution reaction (OER) in alkaline electrolyte. It showed a low overpotential of only 320 mV to afford a current density of 10 mA cm−2 and a Tafel slope of 80.43 mV dec−1. Furthermore, the nanoporous microspheres of Co-Zn-S retained excellent electrocatalytic stability within a period of 36000 s. The catalyst also showed good catalytic performance toward the hydrolysis of ammonia borane to produce around 70 mL of H2 within the time of 30 minutes at room temperature. The nanoporous microspheres of Co-Zn-S exhibits the potential applications for hydrogen/oxygen production by water splitting or ammonia borane hydrolysis.

Production of H2 from aluminium/water reaction and its potential for CO2 methanation

Carbon dioxide (CO2) is a natural gas that presents in excess in the atmosphere. Owing to its ability to cause global warming, capturing and conversion of CO2 have attracted much attention worldwide. CO2 methanation using hydrogen (H2) is believed to be a promising route for CO2 removal. In the present work, H2 is produced using aluminum-water reaction and tested for its ability to convert CO2 to methane (CH4). Different type of water i.e. tap water, distilled water, deionized water and ultrapure water, concentration of sodium hydroxide (NaOH) (0.2 M to 1.0 M) and particle size of aluminum (45 m to 500 μm) were varied as parameter study. It was found that the highest yield of H2 was obtained using distilled water, 1.0 M of NaOH and 45μm particle size of aluminium. However, the highest yield of methane was achieved using a moderate and progressive H2 production (distilled water, 0.6 M of NaOH and 45 μm particle size of aluminium) which allowed sufficient time for H2 to react with CO2. It was concluded that 1130 ml of H2 can produce about 560 ppm of CH4 within 25 min of batch reaction using nickel catalyst.

Synthesis of cerium and nickel doped titanium nanofibers for hydrolysis of sodium borohydride

A recyclable titanium nanofibers, doped with cerium and nickel doped was successfully synthesized by using sol-gel and electrospinning method for hydrogen generation from alkali free hydrolysis of NaBH4. The resultant nanocomposite was characterized to find out the structural and physical-chemical properties by a series of analytical techniques such as FT-IR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), SEM (scanning electron microscope), EDX (energy-dispersive X-ray spectroscopy),N2 adsorption-desorption and BET (Brunauer–Emmett–Teller), etc. The results revealed that cerium and nickel nanoparticles were homogeneously distributed on the surface of the TiO2 nanofibers due to having similar oxidation state and atomic radium of TiO2nanofibers with CeO2 and NiO for the effective immobilization of metal ions. The NiO doped catalyst showed superior catalytic performance towards the hydrolysis reaction of NaBH4 at room temperature. These catalysts have ability to produce 305 mL of H2 within the time of 160 min at room temperature. Additionally, reusability test revealed that the catalyst is active even after five runs of hydrolytic reaction, implying the as-prepared NiO doped TiO2 nanofibers could be considered as a potential candidate catalyst for portable hydrogen fuel system such as PEMFC (proton exchange membrane fuel cells).

Catalytic hydrolysis of starch for biohydrogen production by using a newly identified amylase from a marine bacterium Catenovulum sp. X3

An identified cold-adaptive, organic solvents-tolerant alkaline α-amylase (HP664) from Catenovulum sp. strain X3 was heterologously expressed and characterized in E. coli, and it was further applied to starch saccharification for biohydrogen production. The recombinant HP664 belongs to a member of glycoside hydrolase family 13 (GH13), with a molecular weight of 69.6kDa without signal peptides, and also shares a relatively low similarity (49%) to other reported amylases. Biochemical characterization demonstrated that the maximal enzymatic activity of HP664 was observed at 35°C and pH 9.0. Most metal ions inhibited its activity; however, low polar organic solvents (e.g., benzene and n-hexane) could enhance the activity by 35–50%. Additionally, HP664 also exhibited the catalytic capability on various polysaccharides, including potato starch, amylopectin, dextrin and agar. In order to increase the bioavailability of starch for H2 production, HP664 was utilized to elevate fermentable oligosaccharide level, and the results revealed that the maximal hydrolytic percentage of starch was up to 44% with 12h of hydrolysis using 5.63U of HP664. Biohydrogen fermentation of the starch hydrolysate by Clostridium sp. strain G1 yielded 297.7mL of H2 after 84h of fermentation, which is 3.73-fold higher than the control without enzymatic treatment of HP664.

Very fast H2production from the methanolysis of NaBH4by metal-free poly(ethylene imine) microgel catalysts

The polyethyleneimine (PEI) microgels prepared via microemulsion polymerization are protonated by hydrochloric acid treatment (p-PEI) and quaternized (q-PEI) via modification reaction with methyl iodide and with bromo alkanes of different alkyl chain lengths such as 1-bromoethane, 1-bromobutane, 1-bromohexane, and 1-bromooctane. The bare p-PEI and q-PEI microgels are used as catalysts directly without any metal nanoparticles for the methanolysis reaction of sodium borohydride (NaBH4). Various parameters such as the protonation/quaternization reaction on PEI microgels, the amount of catalyst, the amount of NaBH4, and temperature are investigated for their effects on the hydrogen (H2) production rate. The reaction of self-methanolysis of NaBH4 finishes in about 32.5 min, whereas the bare PEI microgel as catalyst finishes the methanolysis of NaBH4 in 22 min. Surprisingly, it is found that when the protonated PEI microgels are used as catalyst, the same methanolysis of NaBH4 is finished in 1.5 min. The highest H2 generation rate value is observed for protonated PEI microgels (10 mg) with 8013 mL of H2/(g of catalyst.min) for the methanolysis of NaBH4. Moreover, activation parameters are also calculated with activation energy value of 23.7 kJ/mol, enthalpy 20.9 kJ/mol, and entropy −158 J/K.mol. Copyright © 2016 John Wiley & Sons, Ltd.

Biohydrogen Production from Liquid and Solid Fractions of Sugarcane Bagasse After Optimized Pretreatment with Hydrochloric Acid

This work determined the optimal conditions to pretreat sucargane bagasse with HCl by using the liquid and the solid fractions resulting from the bagasse pretreament as substrate for fermentative hydrogen production by a mixed culture. A 23 full factorial central composite design (star configuration) helped to determine how temperature, time, and acid concentration affected the total monosaccharides (TM), total reducing sugars (TRS), and total inhibitors (TI) concentrations in the liquid fraction. Temperature, time, and acid concentration impacted the TRS and TM concentrations, but these variables did not influence the TI concentration significantly. The optimal pretreatment conditions were HCl at 7.36 % (v/v), 96.8 °C, and 441.6 min, which afforded the highest TRS concentration in the liquid hydrolysates. The liquid fraction obtained from the bagasse pretreated with acid under the optimal conditions (designated liq) was not suitable for H2 production by the mixed culture before treatment of the fraction with activated carbon. The solid residual bagasse (designated sol) alone afforded 6.0 mL of H2/g of bagasse. Liq treated with 10 % (m/v) activated carbon, to give liq + C, and sol added with the enzyme Celluclast® 10 U g−1, to afford sol + E, yielded 45.3 and 7.8 mL of H2/g of bagasse respectively, which amounted to 53.1 mL of H2/g of bagasse. The volumetric productivities—1450 and 1423 mL of H2 L−1 d−1 for liq + C and sol + E, respectively—are the highest ever reported in the literature for H2 production from sugarcane bagasse by a microbial consortium.