Significance of acetogenic H2 consumption in dark fermentation and effectiveness of pH

2008 ◽  
Vol 57 (6) ◽  
pp. 809-814 ◽  
Author(s):  
B. Calli ◽  
J. Zhao ◽  
E. Nijssen ◽  
K. Vanbroekhoven
Keyword(s):  
Partial Pressure ◽  
Consumption Rate ◽  
H2 Production ◽  
Dark Fermentation ◽  
Batch Experiments ◽  
Acetate Production ◽  
Butyrate Fermentation ◽  
Reduction Of Co2 ◽  
H2 Yield

Two identical thermophilic H2 fermenters (R1 and R2) were operated at different pH levels between 4.7 and 5.7. In R1, several unexpected and severe drops in H2 yield inversely proportional to increase in acetate production were experienced at pH 5.5 and 5.7. In contrast, R2 operated at pH 5and 4.7 performed more stable H2 production mainly through butyrate fermentation. Although the H2 partial pressure (>50 kPa) was far above the favorable values, acetate was produced as well as butyrate in all pH levels tested. To determine whether some portion of the acetate is produced through another pathway such as autotrophic synthesis via H2 dependent reduction of CO2 or not, batch dissolved H2 consumption rate tests were performed at pH 5.0, 5.5 and 6. The specific H2 consumption rate was 488(±49) μmol/gVSS.hr at pH 6 and slightly higher than at pH 5and 5.5. The results of continuous and batch experiments revealed that acetogenic H2 consumption is more favorable at pH levels above 5.5 and is one of the reasons of instabilities in dark fermentative H2 production.

scholarly journals Role of Mixed Oxides in Hydrogen Production through the Dry Reforming of Methane over Nickel Catalysts Supported on Modified γ-Al2O3

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 157
Author(s):  
Ahmed Sadeq Al-Fatesh ◽  
Mayankkumar Lakshmanbhai Chaudhary ◽  
Anis Hamza Fakeeha ◽  
Ahmed Aidid Ibrahim ◽  
Fahad Al-Mubaddel ◽  
...  
Keyword(s):  
Mixed Oxides ◽  
Nickel Catalysts ◽  
H2 Production ◽  
Dry Reforming ◽  
Dry Reforming Of Methane ◽  
Incipient Wetness Impregnation ◽  
Thermally Stable ◽  
Oxide Systems ◽  
Catalyst Systems ◽  
H2 Yield

H2 production through dry reforming of methane (DRM) is a hot topic amidst growing environmental and atom-economy concerns. Loading Ni-based reducible mixed oxide systems onto a thermally stable support is a reliable approach for obtaining catalysts of good dispersion and high stability. Herein, NiO was dispersed over MOx-modified-γ-Al2O3 (M = Ti, Mo, Si, or W; x = 2 or 3) through incipient wetness impregnation followed by calcination. The obtained catalyst systems were characterized by infrared, ultraviolet–visible, and X-ray photoelectron spectroscopies, and H2 temperature-programmed reduction. The mentioned synthetic procedure afforded the proper nucleation of different NiO-containing mixed oxides and/or interacting-NiO species. With different modifiers, the interaction of NiO with the γ-Al2O3 support was found to change, the Ni2+ environment was reformed exclusively, and the tendency of NiO species to undergo reduction was modified greatly. Catalyst systems 5Ni3MAl (M = Si, W) comprised a variety of species, whereby NiO interacted with the modifier and the support (e.g., NiSiO3, NiAl2O4, and NiWO3). These two catalyst systems displayed equal efficiency, >70% H2 yield at 800 °C, and were thermally stable for up to 420 min on stream. 5Ni3SiAl catalyst regained nearly all its activity during regeneration for up to two cycles.

scholarly journals The Effect of Ni Addition onto a Cu-Based Ternary Support on the H2 Production over Glycerol Steam Reforming Reaction

Nanomaterials ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 931 ◽  
Author(s):  
Kyriaki Polychronopoulou ◽  
Nikolaos Charisiou ◽  
Kyriakos Papageridis ◽  
Victor Sebastian ◽  
Steven Hinder ◽  
...  
Keyword(s):  
Sol Gel ◽  
Strong Acid ◽  
H2 Production ◽  
Impregnation Method ◽  
Reaction Products ◽  
Cu Content ◽  
Ni Addition ◽  
Support Matrix ◽  
Temperature Programmed ◽  
H2 Yield

In the present study, Ni/Ce-Sm-xCu (x = 5, 7, 10 at.%) catalysts were prepared using microwave radiation coupled with sol-gel and followed by wetness impregnation method for the Ni incorporation. Highly dispersed nanocrystallites of CuO and NiO on the Ce-Sm-Cu support were found. Increase of Cu content seems to facilitate the reducibility of the catalyst according to the H2 temperature-programmed reduction (H2-TPR). All the catalysts had a variety of weak, medium and strong acid/basic sites that regulate the reaction products. All the catalysts had very high XC3H8O3 for the entire temperature (400–750 °C) range; from ≈84% at 400 °C to ≈94% at 750 °C. Ni/Ce-Sm-10Cu catalyst showed the lowest XC3H8O3-gas implying the Cu content has a detrimental effect on performance, especially between 450–650 °C. In terms of H2 selectivity (SH2) and H2 yield (YH2), both appeared to vary in the following order: Ni/Ce-Sm-10Cu > Ni/Ce-Sm-7Cu > Ni/Ce-Sm-5Cu, demonstrating the high impact of Cu content. Following stability tests, all the catalysts accumulated high amounts of carbon, following the order Ni/Ce-Sm-5Cu < Ni/Ce-Sm-7Cu < Ni/Ce-Sm-10Cu (52, 65 and 79 wt.%, respectively) based on the thermogravimetric analysis (TGA) studies. Raman studies showed that the incorporation of Cu in the support matrix controls the extent of carbon graphitization deposited during the reaction at hand.

scholarly journals H2 Production from Catalytic Methane Decomposition Using Fe/x-ZrO2 and Fe-Ni/(x-ZrO2) (x = 0, La2O3, WO3) Catalysts

Catalysts ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 793
Author(s):  
Fahad Al-Mubaddel ◽  
Samsudeen Kasim ◽  
Ahmed A. Ibrahim ◽  
Abdulrhman S. Al-Awadi ◽  
Anis H. Fakeeha ◽  
...  
Keyword(s):  
Supported Catalysts ◽  
Thermo Gravimetric Analysis ◽  
Space Velocity ◽  
H2 Production ◽  
Methane Decomposition ◽  
Gravimetric Analysis ◽  
Impregnation Method ◽  
Carbon Deposits ◽  
Surface Areas ◽  
H2 Yield

An environmentally-benign way of producing hydrogen is methane decomposition. This study focused on methane decomposition using Fe and Fe-Ni catalysts, which were dispersed over different supports by the wet-impregnation method. We observed the effect of modifying ZrO2 with La2O3 and WO3 in terms of H2 yield and carbon deposits. The modification led to a higher H2 yield in all cases and WO3-modified support gave the highest yield of about 90% and was stable throughout the reaction period. The reaction conditions were at 1 atm, 800 °C, and 4000 mL(hgcat)−1 space velocity. Adding Ni to Fe/x-ZrO2 gave a higher H2 yield and stability for ZrO2 and La2O3 + ZrO2-supported catalysts whose prior performances and stabilities were very poor. Catalyst samples were analyzed by characterization techniques like X-ray diffraction (XRD), nitrogen physisorption, temperature-programmed reduction (TPR), thermo-gravimetric analysis (TGA), and Raman spectroscopy. The phases of iron and the supports were identified using XRD while the BET revealed a significant decrease in the specific surface areas of fresh catalysts relative to supports. A progressive change in Fe’s oxidation state from Fe3+ to Fe0 was observed from the H2-TPR results. The carbon deposits on Fe/ZrO2 and Fe/La2O3 + ZrO2 are mainly amorphous, while Fe/WO3 + ZrO2 and Fe-Ni/x-ZrO2 are characterized by graphitic carbon.

The Performance Characteristics of Anaerobic Baffled Reactor (ABR) Fermentation System

2012 ◽  
Vol 610-613 ◽  
pp. 347-351
Author(s):  
Guo Chen Zheng ◽  
Zhu Jun Tian ◽  
Jian Zheng Li ◽  
Li Wei ◽  
Ajay Kumar Jha ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Activated Sludge ◽  
Production Efficiency ◽  
Oxygen Demand ◽  
H2 Production ◽  
Anaerobic Baffled Reactor ◽  
Steady Stage ◽  
Start Up ◽  
Acid Type ◽  
H2 Yield

A anaerobic baffled reactor (ABR) with an effective volume of 28.7 L was adopted, and the hydrogen production efficiency was investigated with diluted molasses as the substrate. Using a mixture of aerobic and anaerobic activated sludge, the ABR was start-up with a hydraulic retention time (HRT) of 24 h and 35°C. When the influent chemical oxygen demand (COD) concentration was gradually increased from 500 mg/L to 6000 mg/L after a 63-day operation, the ABR kept a steady state. The increase of influent COD concentration, from 6000 mg/L to 8000 mg/L stage by stage, had the remarkable changes on the fermentative system. The ethanol-type fermentation was formed in the first three compartments, while butyric acid-type fermentation in the 4th compartment. In the steady stage at the influent COD of 8000 mg/L, the biogas (H2) yield was found 61.54 L/d (12.85 L/d) while specific H2 production rate of the activated sludge was 48 L/kgMLVSS∙d. Although the ABR system accumulated hydrogen-producing acetogen, due to the hydrogen-consuming bacteria (methanogen and homoacetogenic bacteria), the hydrogen production efficiency was badly inhibited.

Characteristics of Biohydrogen Production by Mixed Culture Using Bagasse as the Substrate

2010 ◽  
Vol 113-116 ◽  
pp. 1749-1754
Author(s):  
An Ying Jiao ◽  
Yong Feng Li ◽  
Bing Liu ◽  
Kun Liu
Keyword(s):  
Gas Chromatography ◽  
Mixed Culture ◽  
Dark Fermentation ◽  
Biohydrogen Production ◽  
Hydrogen Yield ◽  
Batch Experiments ◽  
Ethanol Acetic Acid ◽  
Liquid Products ◽  
Initial Ph ◽  
Favorable Conditions

Batch culture of dark fermentation was carried out to study the feasibility of biohydrogen production using bagasse as the substrate. In dark fermentation, hydrogen was produced by mixed culture using bagasse as the substrate. To establish favorable conditions for maximum hydrogen production, process parameters such as temperature and initial pH of the medium were investigated. Also, the component of biogas and liquid products of effluent by fermentation were analyzed by gas chromatography. The VFAs were mostly ethanol, acetic acid, propionic acid and butyric acid, and no valeric acid was observed. It is demonstrated that the hydrogen yield reached the maximum of 30.5mlH2/g bagasse while the temperature was 35°C in batch experiments under a series of temperature (25, 30, 35, 40°C) conditions. The initial pH ranged from 6.8 to 8.5, and the yield of hydrogen reached the maximum of 32mlH2/g bagasse with the initial pH of 8.5.

scholarly journals The prospects of alcohol industry wastes application in photoproduction of hydrogen by the purple bacteria Rhodobacter sphaeroides

2021 ◽  
pp. 70-77
Author(s):  
Lilit S. Gabrielyan
Keyword(s):  
Growth Rate ◽  
Rhodobacter Sphaeroides ◽  
Purple Bacteria ◽  
Carbon Sources ◽  
H2 Production ◽  
Distillers Grains ◽  
Industrial Wastes ◽  
Alcohol Industry ◽  
Spent Grains ◽  
H2 Yield

The possibilities of using various industrial wastes to produce biofuel are currently being considered. It will provide not only novel, efficient and cheap sources of hydrogen (H2), but will also help to solve the problem of waste disposal. The current work presents the prospects of application of alcohol industry wastes, such as distillers grains and brewery spent grains, for production of H2 by the purple bacteria Rhodobacter sphaeroides MDC6522. The data obtained showed the possibility of using distillers grains and brewery spent grains as effective carbon sources for producing H2. It was shown that pre-treatment of wastes, their dilution and neutralization are necessary to ensure the effective bacterial growth and H2 production by R. sphaeroides. The growth rate and H2 yield during the cultivation of bacteria on a 2-fold diluted distillers grains medium increased 2- and 4-fold, respectively, compared with a culture, grown on standard Ormerod medium. At the same time, the growth rate and photoproduction of H2 on a 10-fold diluted brewery spent grains medium were 2-fold higher, in comparison with the control. Thus, the results obtained indicate that these alcohol industry wastes can be used as promising substrates for biohydrogen production.

The Effect of Hydrogen Peroxide Concentration on the Oxidative Dissolution of Unirradiated Uranium Dioxide

2000 ◽  
Vol 663 ◽  
Author(s):  
J. De Pablo ◽  
I. Casas ◽  
F. Clarens ◽  
F. El Aamrani ◽  
M. Rovira
Keyword(s):  
Hydrogen Peroxide ◽  
Dissolution Rate ◽  
Solid Surface ◽  
Uranium Dioxide ◽  
Consumption Rate ◽  
Reaction Order ◽  
Chemical Processes ◽  
Surface Chemical ◽  
Batch Experiments ◽  
Oxidative Dissolution

ABSTRACTThe dissolution rate of unirradiated uranium dioxide was studied in batch experiments as a function of hydrogen peroxide concentration (from 10−5 to 10−3 mol dm−3). Unirradiated UO2(s) was used in order to differentiate surface chemical processes from radiolytic effects. Dissolution rates were determined from both uranium release and hydrogen peroxide consumption. Results showed that H2O2consumption rate was higher than UO2 dissolution rate. This observation may indicate that the overall UO2 oxidative dissolution process would be controlled by the dissolution of the oxidized solid surface. The calculated hydrogen peroxide reaction order was 1 in the H2O2 concentration range from 10−5 to 10−4 mol dm−3, while at higher concentrations no clear dependence was observed.

Towards the integration of dark- and photo-fermentative waste treatment. 3. Potato as substrate for sequential dark fermentation and light-driven H2 production

2010 ◽  
Vol 35 (16) ◽  
pp. 8536-8543 ◽  
Author(s):  
Tatyana V. Laurinavichene ◽  
Boris F. Belokopytov ◽  
Kestutis S. Laurinavichius ◽  
Darya N. Tekucheva ◽  
Michael Seibert ◽  
...  
Keyword(s):  
Waste Treatment ◽  
H2 Production ◽  
Dark Fermentation

scholarly journals Photocatalytic Hydrogen Evolution Using Bi-Metallic (Ni/Pt) Na2Ti3O7 Whiskers: Effect of the Deposition Order

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 285 ◽  
Author(s):  
Luis F. Garay-Rodríguez ◽  
S. Murcia-López ◽  
T. Andreu ◽  
Edgar Moctezuma ◽  
Leticia M. Torres-Martínez ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Characterization ◽  
Sodium Titanate ◽  
H2 Production ◽  
Superior Performance ◽  
Hydrogen Yield ◽  
Wet Impregnation ◽  
X Ray ◽  
Co Catalysts ◽  
H2 Yield

Photocatalytic hydrogen production through ethanol photo-reforming using Na2Ti3O7 whiskers increases if the sodium titanate is decorated with well-known metallic catalysts such as Ni and Pt. Whereas wet impregnation with nickel gives only a slight increase in the activity, photo-deposition of Pt increased the H2 production by more than one order of magnitude. Through the combination of both co-catalysts (Ni and Pt) a superior performance in terms of H2 production is further observed. However, hydrogen yield is largely enhanced (almost three-fold), up to 778 μmol·g−1·h−1, if the Pt is photo-deposited on the surface of the catalyst before wet impregnation with Ni species (NTO/Pt/Ni) compared to H2 yield (283 μmol·g−1·h−1) achieved with the catalyst prepared in the reverse order (NTO/Ni/Pt). Structural, morphological, optical, and chemical characterization was carried out in order to correlate physicochemical properties with their photocatalytic activity. The X-ray photoelectron spectroscopy (XPS) results show a higher concentration of Pt2+ species if this metallic layer is under the nickel oxide layer. Moreover, X-ray diffraction patterns (XRD) show that Na2Ti3O7 surface is modified for both metal decoration processes.

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