Hydrogen production from renewable material

To utilize the full potential of hydrogen energy in the UK a number of economic, technical and environmental factors must be considered. An important factor in replacing fossil fuels with hydrogen will be the practicality of storing sufficient quantity to smooth out fluctuations in demand and provide a strategic reserve. This paper investigates the potential for large-scale hydrogen storage in the UK by considering the technical and geophysical problems of storage, the locations of salt deposits, legal and economic issues. In addition, reference is also made to the equations of state applicable to underground hydrogen storage. The results of this investigation show that the UK has a number of potential locations where underground storage would provide a strategic reserve of hydrogen.

A series of mesoporous TiO 2 (meso-TiO 2) were synthesized using the sol-gel technique. A Pluronic F127 triblock-copolymer, a structure-directing agent, was incorporated as a soft template into the sol-gel. In addition, and during a separate synthesis, the sol-gel was doped with a Pt precursor. Semiconductors were prepared with 1.00 wt.%, 2.50 wt.%, 5.00 wt.% Pt nominal loadings, respectively. They were calcined at 500 • C and 550 • C following synthesis. Morphological and structural properties were studied by: a) X-ray diffraction, b) UV–vis spectrophotometry, c) N 2 adsorption-desorption (BET, BJH), and d) X-ray photoelectron spectroscopy (XPS). Optical band gap values for meso-TiO 2 and Pt-meso-TiO 2 were calculated by Kubelka-Munk (K-M) function coupled with Tauc plot methodology. It was observed that the prepared semiconductors displayed pore sizes in the 10–40 nm range with bimodal distributions. Their photocatalytic activity for hydrogen production via water splitting was established in a Photo-CREC Water-II reactor under near-UV light irradiation. The aqueous solution contained 2% v/v ethanol, employed as a renewable organic scavenger. The prepared semiconductors showed that the mesoporous 2.50 wt.% Pt-TiO 2 has the highest photoactivity for hydrogen generation. This suggests the important role played by the loading of platinum as a TiO 2 dopant, reducing the optical band gap, increasing electron storage and diminishing, as a result, electron-hole recombination. The measured Quantum Yield (QY), obtained using a rigorous approach, was established for the mesoporous 2.50 wt.% Pt-TiO 2 at a promising level of 22.6%.

In this chapter, a comparative environmental impact study of possible hydrogen production methods from renewable and nonrenewable sources is undertaken with a special emphasis on Turkey. The goal is to make useful and practical recommendations to the authorities in terms of research and development, demonstration projects and applications. Environmental impacts (global warming potential, GWP and acidification potential, AP), production costs, energy and exergy efficiencies of eight different methods are compared. These methods are natural gas steam reforming, coal gasification, water electrolysis via wind and solar electrolysis, thermochemical water splitting with a Cu–Cl and S–I cycles, and high temperature electrolysis. The relations between environmental impacts and economic factors are also presented using the social cost of carbon (SCC) concept. The global warming and acidification potentials of the selected production methods show that thermochemical water splitting with the Cu–Cl and S–I cycles are advantageous over the other methods, followed by wind, solar, and high temperature electrolysis. In terms of hydrogen production costs, electrolysis methods are found to be least attractive. Energy and exergy efficiency comparisons show that biomass gasification becomes advantageous over the other methods.

Ammonia Plant Technology
Pre-Commissioning Best Practices:
Piping and Vessels Flushing and Cleaning Procedure
CONTENTS
1 Scope
2 Aim/purpose
3 Responsibilities
4 Procedure
4.1 Main cleaning methods
4.1.1 Mechanical cleaning
4.1.2 Cleaning with air
4.1.3 Cleaning with steam (for steam networks only)
4.1.4 Cleaning with water
4.2 Choice of the cleaning method
4.3 Cleaning preparation
4.4 Protection of the devices included in the network
4.5 Protection of devices in the vicinity of the network
4.6 Water flushing procedure
4.6.1 Specific problems of water flushing
4.6.2 Preparation for water flushing
4.6.3 Performing a water flush
4.6.4 Cleanliness criteria
4.7 Air blowing procedure
4.7.1 Specific problems of air blowing
4.7.2 Preparation for air blowing
4.7.3 Performing air blowing
4.7.4 Cleanliness checks
4.8 Steam blowing procedure
4.8.1 Specific problems of steam blowing
4.8.2 Preparation for steam blowing
4.8.3 Performing steam blowing
4.8.4 Cleanliness checks
4.9 Chemical cleaning procedure
4.9.1 Specific problems of cleaning with a chemical solution
4.9.2 Preparation for chemical cleaning
4.9.3 Performing a chemical cleaning
4.9.4 Cleanliness criteria
4.10 Re-assembly - general guideline
4.11 Preservation of flushed piping

Gymnema  sylvestre  (Asclepiadaceae) is  a  good  source  of  large
number  of  bioactive  substances.  It  has  deep  roots  in  history,  being
one  of  the  major  botanicals  used  in  traditional  medicine  to  treat
conditions ranging from diabetes, malaria, to snakebites. This study
was conducted to quantitatively evaluate anti-haemolytic activity of
aqueous  extract  of  stem,  leaf  and  flower  parts  of  this  plant,  against
hydrogen  peroxide  induced  haemolysis  using  human  erythrocyte  in
an in vitro  assay. Prior to the addition of H
2O2
to induce haemolysis,
different concentrations (50-500 mg/ml) of the extract was added to
2ml  of  4%  erythrocyte  suspension  and  allowed  to  incubate  for  5
minutes  at  room  temperature.  The  mixture  was  centrifuged  and  the
colour  density  of  the  supernatant  was  measured
spectrophotometrically.  Quercetin  was  used  as  standard.  The
percentage haemolysis and IC
50
values were calculated. The extracts
were  potent  against  haemolysis  of  the  erythrocyte  in  concentration
dependent  manner.  The  leaf  extract  exhibited  the  highest  antihaemolytic  effect  with  IC
50 =  29.83  mg/ml  followed  by  the  flower
with IC50= 34.96 mg/ml and the least was the stem with IC50
= 37.75
mg/ml. the IC50
value of Quercetin was 386.72 mg/ml. The lower the
IC
50
the more protection offered against haemolysis by  the extracts.
These results suggest that the plant extracts are better anti-haemolytic
agents  and  offered  significant  biological  action  compared  with
standard compound used.

This paper presents an exergy and environmental assessment of a 1000 metric t/day ammonia production plant based on the steam methane reforming (SMR) process, including the syngas production, purification (CO 2 capture) and compression units, as well as the ammonia synthesis and purge gas treatment. An integrated heat recovery system produces power and steam at three pressure levels, besides exporting hot water, CO 2 and fuel gas, with no additional heat or power consumption being required. Two configurations for ammonia refrigeration process (À20 C) are compared in terms of power consumption. Exergy cost data for upstream processing stages of natural gas is used to calculate the extended exergy cost of the products of the plant, namely ammonia, CO 2 and fuel gas. Moreover, an appropriated methodology is employed to properly allocate the renewable and non-renewable exergy costs, as well as the CO 2 emissions of the reforming, shift and furnace stack among the products of the plant. By considering that the cost reduction of the combustion gases is a linear function of the exergy flow rate reduction in each component of the heat recovery system, an improved allocation of the CO 2 emission cost along the convection train is performed. A breakdown of the total exergy destruction rate of the plant (136.5 MW) shows that about 59% corresponds to the reforming process followed far behind by the ammonia synthesis and condensation (18.3%) and the gas purification units (13.2%). The overall exergy efficiency of the ammonia plant is calculated as 66.36%, which is enhanced by recovering the hydrogen-rich and fuel gases in the purge gas treatment process. The total and non-renewable exergy costs and CO 2 emission cost of the ammonia produced are calculated as 1.7950 kJ/kJ and 0.0881 kg CO2 /MJ, respectively. In addition, a rational exergy cost of 1.6370 kJ/kJ and CO 2 emission cost of 0.0821 kg CO2 /MJ are allocated to the CO 2 gas, which can be supplied as feedstock to an associated chemical plant (urea, methanol, polymers, etc.).

In this study, we investigate the economic, environmental and social impacts of various hydrogen production methods,
based on fossil fuel and renewable energy resources with a special emphasis on hybrid photoelectrochemical systems perform
comparative assessments of these methods for applications. The sources considered for hydrogen production in this
study are water, fossil hydrocarbons, and biomass. Furthermore, the primary energy sources considered in this study are
natural gas, coal, biomass, wind and solar. In order to address sustainability, the relationship between efficiency and environmental
impact is also investigated. The results show that solar based hydrogen production options (photocatalysis,
photoelectrolysis, and photoelectrochemical methods) provide near zero global warming potentials and air pollutants, while
coal gasification has the highest ones. In regards to the exergy efficiencies, biomass gasification gives the highest exergy
efficiency, while photoelectrochemical method ends up with the lowest one.

This paper examines photocatalytic hydrogen production as a clean energy solution to address challenges of climate change and environmental sustainability. Advantages and disadvantages of various hydrogen production methods, with a particular emphasis on photocatalytic hydrogen production, are discussed in this paper. Social, environmental and economic aspects are taken into account while assessing selected production methods and types of photocatalysts. In the first part of this paper, various hydrogen production options are introduced and comparatively assessed. Then, solar-based hydrogen production options are examined in a more detailed manner along with a comparative performance assessment. Next, photocatalytic hydrogen production options are introduced, photocatalysis mechanisms and principles are discussed and the main groups of photocatalysts, namely titanium oxide, cadmium sulfide, zinc oxide/sulfide and other metal oxide-based photocatalyst groups, are introduced. After discussing recycling issues of photocatalysts, a comparative performance assessment is conducted based on hydrogen production processes (both per mass and surface area of photocatalysts), band gaps and quantum yields. The results show that among individual photocatalysts, on average, Au–CdS has the best performance when band gap, quantum yield and hydrogen production rates are considered. From this perspective, TiO 2 –ZnO has the poorest performance. Among the photocatalyst groups, cadmium sulfides have the best average performance, while other metal oxides show the poorest rankings, on average.

In this study, different hydrogen production sources and systems and some hydrogen storage options are comparatively investigated in detail. Economic, environmental, social, and technical performance and reliability of the selected options are compared in detail. Biomass, geothermal, hydro, nuclear, solar, and wind are the selected hydrogen production sources; biological, thermal, photonic, and electrical are the selected hydrogen production methods; and chemical hydrides, compressed gas, cryogenic liquid, metal hydrides, and nanomaterials are the selected hydrogen storage systems. In addition, some case studies and basic research needs to enhance the performance of hydrogen energy systems and to tackle the major challenges of the hydrogen economy are provided. The results show that solar has the highest environmental performance (8/10) and the total average ranking (7.40/10), nuclear has the lowest environmental performance (3/10), and geothermal has the lowest total average ranking (4/10/10) among selected hydrogen production sources. Hydrogen production systems’ comparison indicates that photonic options have the highest environmental performance ranking (8/10), thermal options have the lowest environmental performance ranking (5/10), electrical options have the highest average ranking (7.60/10), and biological options have the lowest average ranking (4.80/10).

This paper examines various potential methods of hydrogen production using renewable and non-renewable sources and comparatively assesses them for environmental impact, cost, energy efficiency and exergy efficiency. The social cost of carbon concept is also included to present the relations between environmental impacts and economic factors. Some of the potential primary energy sources considered in this study are: electrical, thermal, biochemical, photonic, electro-thermal, photo-electric, and photo-biochemical. The results show that when used as the primary energy source, photonic energy based hydrogen production (e.g., photocatalysis, photoelectrochemical method, and artificial photosynthesis) is more environmentally benign than the other selected methods in terms of emissions. Thermochemical water splitting and hybrid thermochemical cycles (e.g. Cu–Cl, S–I, and Mg–Cl) also provide environmentally attractive results. Both photoelectrochemical method and PV electrolysis are found to be least attractive when production costs and efficiencies are considered. Therefore, increasing both energy and exergy efficiencies and decreasing the costs of hydrogen production from solar based hydrogen production have a potential to bring them forefront as potential options. The energy and exergy efficiency comparisons indicate the advantages of fossil fuel reforming and biomass gasification over other methods. Overall rankings show that hybrid thermochemical cycles are primarily promising candidates to produce hydrogen in an environmentally benign and cost-effective way.

The use of biomass to produce transportation and related fuels is of increasing interest. In the traditional approach of converting oils and fats to fuels, trans-esterification processes yield a very large coproduction of glycerol. Initially, this coproduct was largely ignored and then considered as a useful feedstock for conversion to various chemicals. However, because of the intrinsic large production, any chemical feedstock role would consume only a fraction of the glycerol produced, so other options had to be considered. The reforming of glycerol was examined for syngas production, but more recently the use of photocatalytic decomposition to hydrogen (H 2) is of major concern and several approaches have been proposed. The subject of this review is this greener photocatalytic route, especially involving the use of solar energy and visible light. Several different catalyst designs are considered, together with a very wide range of secured rates of H 2 production spanning several orders of magnitude, depending on the catalytic system and the process conditions employed. H 2 production is especially high when used in glycerol-water mixtures.

Thermocatalytic decomposition of methane (TCD) is a fully green single step technology for producing hydrogen and nano-carbon. This review studying all development in laboratory-scale research on TCD, especially the recent advances like co-feeding effect and catalyst regeneration for augmenting the productivity of the whole process. Although a great success on the laboratory-scale has been fulfilled, TCD for greenhouse gas (GHG) free hydrogen production is still in its infancy. The need for commercialization of TCD is greater than ever in the present situation of huge GHG emission. TCD usually examined over various kind of catalysts, such as monometallic, bimetallic, trimetallic, combination of metal–metal oxide, carbonaceous and/or metal doped carbon catalysts. Deactivation of catalysts is the prime drawback found in TCD process. Catalyst regeneration and co-feeding of methane with other hydrocarbon are the two solutions put forwarded in accordance to overcome deactivation hurdle. Higher amount of co-feed hydrocarbon in situ produce more amount of highly active carbonaceous deposits which assist further methane decomposition to produce additional hydrogen to a great extent. The methane conversion rate increases with increase in the temperature and decreases with the flow rate in the co-feeding process in a similar manner as observed in normal TCD. The presence of co-components in the post-reaction stream is a key challenge tackled in the co-feeding and regeneration. Hence, this review hypothesizing the integration of hydrogen separation membrane in to methane decomposition reactor for online hydrogen separation.

Hydrogen is a zero-carbon footprint energy source with high energy density that could be the basis of future energy systems. Membrane-based water electrolysis is one means by which to produce high-purity and sustainable hydrogen. It is important that the scientific community focus on developing electrolytic hydrogen systems which match available energy sources. In this review, various types of water splitting technologies, and membrane selection for electrolyzers, are discussed. We highlight the basic principles, recent studies, and achievements in membrane-based electrolysis for hydrogen production. Previously, the Nafion TM membrane was the gold standard for PEM electrolyzers, but today, cheaper and more effective membranes are favored. In this paper, CuCl-HCl electrolysis and its operating parameters are summarized. Additionally, a summary is presented of hydrogen production by water splitting, including a discussion of the advantages, disadvantages, and efficiencies of the relev...

In this study, CdS, TiO2, CdSe, WO3, Fe2O3, and CuO/Cu2O based photoelectrode coating materials are considered for investigation under some significant selected coating methods, namely, chemical vapor deposition (CVD), electrochemical deposition (ECD), electrodeposition (ED), solegel (SG), spin coating (SC), and spray pyrolysis (SP). Their performance evaluations are carried out comparatively for photoelectrochemical hydrogen production. The photocurrent generation and voltage/light requirements of these photoelectrodes are also compared to evaluate the impact of material and method selection on photoelectrochemical hydrogen generation. The results show that among selected photoelectrode coating materials, CdS based photoelectrodes generate the highest photocurrent (3715.58 mA/cm2), followed by CdSe (2963.43 mA/cm2), CuO/Cu2O (1873.33 mA/cm2), TiO2 (1500.60 mA/cm2), WO3 (1435.28 mA/cm2), and Fe2O3 (443.3 mA/cm2). Average photocurrent densities of selected coating methods show that photocathodes processed by spin coating produce the highest photocurrent (2343.57 mA/cm2), followed by electrochemical deposition (1623.36 mA/cm2), electrodeposition (1359.77 mA/cm2), spray pyrolysis (1217.50 mA/cm2), chemical vapor deposition (619.44 mA/cm2), and sol-gel (335.06 mA/cm2).

This thesis proposes, at laboratory scale, a new process to chemically store wave energy in hydrogen form. The conversion of the wave energy is achieved by concentrating potential
energy through a narrowing ramp and cup, through which the oscillations are forced, transforming it into kinetic energy (water jet). The shape of the device is inspired by the marine phenomenon known as “La Bufadora” and a Norwegian device called TAPCHAN. It thus resembles a musical instrument, the tuba, and it is called Blowjet. The Blowjet managed to direct the energy of small waves, between 8 and 20 cm, in intermittent jets, to a Pelton turbine generator, producing direct current between 2 and 200 mA and 1.7 to 1.8 V. This low quality, low cost electricity was sufficient to break the water molecule within the proton exchange membrane electrolyzers, obtaining, under the best experimental conditions, 82 cm3/h of hydrogen. In this way, the Blowjet has opened up a technological possibility of
obtaining hydrogen on a massive scale from a renewable energy source.

The present study investigates the integrated catalytic adsorption (ICA) steam gasification of palm kernel shell for hydrogen production in a pilot scale atmospheric fluidized bed gasifier. The biomass steam gasification is performed in the presence of an adsorbent and a catalyst in the system. The effect of adsorbent to biomass (A/B)  ratio (0.5-1.5 wt/wt), fluidization velocity (0.15-0.26 m/s) and biomass particle size (0.355-2.0 mm) are studied at temperature of 675 °C, steam to biomass (S/B) ratio of 2.0 (wt/wt) and biomass to catalyst ratio of 0.1 (wt/wt). Hydrogen composition and yield, total gas yield, and lower product gas heating values (LHVgas) increases with increasing A/B ratio, while particle size has no significant effect on hydrogen composition and yield, total gas and char yield, gasification and carbon conversion efficiency. However, gas heating values increased with increasing biomass particle size which is due to presence of high methane content in product gas. Meanwhile, medium fluidization velocity (0.21 m/s) favoured hydrogen composition and yield. The results showed that the maximum hydrogen composition and yield of 84.62 vol% and 91.11 g H2/kg biomass, respectively, are observed at A/B ratio of 1.5, S/B ratio of 2.0, catalyst to biomass ratio of 0.1 and temperature of 675 °C. The product gas heating values are observed in the range of 10.92-17.02 MJ/Nm3. Gasification and carbon conversion efficiency are observed in the range of 25.66-42.95 % and 20.61-41.95 %, respectively. These lower efficiencies are due to significant CO2 capturing using in-situ CO2 adsorption in pilot scale fluidized bed gasification system. The comparative study with literature shows that the combination of adsorbent and catalyst produces better results in terms of hydrogen composition and gas heating values compared to that of biomass steam catalytic gasification and steam gasification with in-situ CO2 adsorbent.

Hydrogen is a zero-carbon footprint energy source with high energy density that could be the basis of future energy systems. Membrane-based water electrolysis is one means by which to produce high-purity and sustainable hydrogen. It is important that the scientific community focus on developing electrolytic hydrogen systems which match available energy sources. In this review, various types of water splitting technologies, and membrane selection for electrolyzers, are discussed. We highlight the basic principles, recent studies, and achievements in membrane-based electrolysis for hydrogen production. Previously, the Nafion TM membrane was the gold standard for PEM electrolyzers, but today, cheaper and more effective membranes are favored. In this paper, CuCl-HCl electrolysis and its operating parameters are summarized. Additionally, a summary is presented of hydrogen production by water splitting, including a discussion of the advantages, disadvantages, and efficiencies of the relevant technologies. Nonetheless, the development of cost-effective and efficient hydrogen production technologies requires a significant amount of study, especially in terms of optimizing the operation parameters affecting the hydrogen output. Therefore, herein we address the challenges, prospects, and future trends in this field of research, and make critical suggestions regarding the implementation of comprehensive membrane-based electrolytic systems.

Bioethanol is an interesting feedstock that may be used for hydrogen production by steam or autothermal reforming. However, the impurities (heavy alcohols, esters, acids, N compounds) contained in the raw feedstock require a costly purification, as they have a dramatic impact on catalyst activity and stability. Thus, a method that can utilize the raw feedstock without severe degradation of the catalyst would be desirable.
In this Minireview, the composition of bioethanol from first and second generation biomass, the reactions involved in the catalytic ethanol steam reforming process and the design of catalysts adapted for hydrogen production from a real bioethanol feed are surveyed.

In this study, hydroxy gas (HHO) was produced by the electrolysis process of different electrolytes (KOH(aq), NaOH(aq), NaCl(aq)) with various electrode designs in a leak proof plexiglass reactor (hydrogen generator). Hydroxy gas was used as a supplementary fuel in a four cylinder, four stroke, compression ignition (CI) engine without any modification and without need for storage tanks. Its effects on exhaust emissions and engine performance characteristics were investigated. Experiments showed that constant HHO flow rate at low engine speeds (under the critical speed of 1750 rpm for this experimental study), turned advantages of HHO system into disadvantages for engine torque, carbon monoxide (CO), hydrocarbon (HC) emissions and specific fuel consumption (SFC). Investigations demonstrated that HHO flow rate had to be diminished in relation to engine speed below 1750 rpm due to the long opening time of intake manifolds at low speeds. This caused excessive volume occupation of hydroxy in cylinders which prevented correct air to be taken into the combustion chambers and consequently, decreased volumetric efficiency was inevitable. Decreased volumetric efficiency influenced combustion efficiency which had negative effects on engine torque and exhaust emissions. Therefore, a hydroxy electronic control unit (HECU) was designed and manufactured to decrease HHO flow rate by decreasing voltage and current automatically by programming the data logger to compensate disadvantages of HHO gas on SFC, engine torque and exhaust emissions under engine speed of 1750 rpm. The flow rate of HHO gas was measured by using various amounts of KOH, NaOH, NaCl (catalysts). These catalysts were added into the water to diminish hydrogen and oxygen bonds and NaOH was specified as the most appropriate catalyst. It was observed that if the molality of NaOH in solution exceeded 1% by mass, electrical current supplied from the battery increased dramatically due to the too much reduction of electrical resistance. HHO system addition to the engine without any modification resulted in increasing engine torque output by an average of 19.1%, reducing CO emissions by an average of 13.5%, HC emissions by an average of 5% and SFC by an average of 14%.

Photosynthetic bacteria and green algae photoproduce H2, but do so utilizing different catalysts and substrates. Green algae use reductant generate mostly by water oxidation to catalyze the reduction of protons to H2 gas, while photosynthetic bacteria catalyze H2 production from organic acids using the nitrogenase enzyme. Moreover, these two organisms utilize different regions of the solar spectrum to perform photosynthesis: green algae’s light harvesting antenna is comprised of chlorophyll molecules that absorb mostly blue and red light; photosynthetic bacteria harvest blue and far-red light through their light-harvesting pigments to run its non-oxygenic photosynthetic reactions. There is thus an opportunity to increase the range of solar spectrum used to photoproduce H2 by combining the light-harvesting and catalytic properties of these two organisms in a single process. In the current manuscript, we describe an experimental system that validates this hypothesis and demonstrates quantitatively the advantages of a two- organism process for production of higher amounts of H2 and thus achieving solar light conversion efficiencies.

In December 2021, the US Department of Energy (DoE) unveiled the Office of Clean Energy Demonstrations with $21.5bn in federal funding to deploy the advanced green technologies. The most significant portion of the budget, $9.5bn, has been dedicated to renewable hydrogen to commercialize innovative technologies and establish four regional hubs and a recycling and manufacturing program. Green hydrogen is already the focus of the DoE's energy initiatives, which aims to mitigate the cost of renewable hydrogen production by 80% over the next decade.

Nanostructured TiO 2 hollow spheres (THS) were prepared via a simple hydrothermal method with titanium butoxide, ethanol, urea, and ammonium sulphate. The effects of Ti/ethanol, and reflux temperature on the morphological properties of the nanostructured THS were investigated. An impregnation method was subsequently employed to load metals such as Cu, Co, Cr, Ag, and Ni on the optimized THS, followed by calcination in H 2 /N 2 at 450 °C for 4 h. The morphological properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron mi-croscopy (TEM), and ultraviolet-visible spectroscopy (UV/vis). The SEM and TEM pictures showed that the Ti/ ethanol ratio of 1:10 resulted in the formation of uniform hollow spheres. The XRD spectre revealed that phase transformation took place as the reflux temperature was increased, with pure anatase TiO 2 hollow spheres being formed at 200 °C. The BET surface areas of the calcined photocatalysts were in the range of 80.6–116 m 2 /g −1. The UV/vis spectra of the photocatalysts showed that loading of transition metals reduced the band gap of the THS. The activities of the prepared catalysts were tested for hydrogen production via photocatalytic reforming of glycerol under solar irradiation. The improved hydrogen evolution from photocatalytic reforming of glycerol was attributed to: the high surface area which enhanced the adsorption of glycerol onto the surface of photo-catalysts; high crystallinity and the reduced band gap which improved the solar light harvesting; the hollow chamber within the TiO 2 spheres which produced multiple reflection of the light harvested, thus producing efficient electron/hole pair formation; and the detailed composition of the solids retarded the electron/hole recombination by trapping the electrons generated during the photo excitation of the photocatalysts, and thereby promoted their activity.

El hidrógeno es una alternativa de gran interés frente a los combustibles convencionales porque solo genera agua como producto de combustión y tiene un alto valor calorífico. En este estudio se evaluó el efecto que tiene la relación sustrato-microorganismo en la producción de este combustible por vía fermentativa. Se encontró que usando un inóculo de una planta de tratamiento de aguas residuales de un ingenio azucarero se puede producir hasta 1.71 mol H2/1 mol C6H12O6 usando como condición operativa 3 g ST/L de inóculo y 3g/L de glucosa. También se determinó que la cinética de producción de hidrógeno se ajusta en un 98.05% al modelo de Gompertz, con una producción máxima de 434.5±18 mL, tasa de producción máxima de 38.997±3.3 mL/hr, tiempo de fase de latencia de 13.365±0.4 hr y velocidad máxima de consumo de sustrato de 58.25 mg C6H12O6/hr.

Nanoconfining hydrogen storage material inside nanopores has emerged as an intriguing strategy to influence the material characteristics but also sacrifices part of system gravimetric and volumetric hydrogen capacity. Herein, we tackle these two challenges by nanoconfining LiBH4 into a new scaffold, zeolite-templated carbon (ZTC), with high porosity and excellent mechanical stability to form a densified nanoconfinement system. After nanoconfinement of LiBH4 and 750 MPa densification, the nanocomposite begins to release hydrogen at 194 °C, 181 °C lower than that of the bulk LiBH4. The rehydrogenation of LiBH4 achieves under mild conditions with improved cycle stability. Moreover, the activation energy of hydrogen desorption is dramatically reduced by 60.4 kJ mol−1, coupled with the foaming effect of desorption almost eliminated. More importantly, the over-infiltrated LiBH4@ZTC systems are capable of maintaining their good hydrogen storage performances, which is attributed to the interface/surface effect between hydrides and scaffolds. With ultra-high pressure densification and high uploading amount of LiBH4, the nanoconfined composite achieves an exceptional gravimetric capacity of 6.92 wt% and volumetric capacity of 75.43 g L−1. These findings add new insights in the development of nanoconfinement systems with enhanced hydrogen storage capacity.

Glycerol is the main by-product during the trans-esterification of vegetable oils to biodiesel. In this study, we investigate the process of photocatalytic hydrogen production from glycerol aqueous solution, with the use of cobalt doped TiO2 photocatalyst under solar light irradiation. Cobalt doped TiO2 photocatalysts are prepared by impregnation method and these catalysts are characterized by XRD, EDAX, DRS, TEM, EPR and XPS techniques. DRS studies clearly show the expanded photo response of TiO2 into visible region on impregnation of Co2+ ions on surface of TiO2. XPS studies also show change in the binding energy values of O1s, Ti 2p and Co 2p, indicating that Co2+ ions are in interaction with TiO2. Maximum hydrogen production of 220 μ mol h−1 g−1 is observed on 2 wt% cobalt doped TiO2 catalysts in pure water under solar irradiation. A significant improvement in hydrogen production is observed in glycerol: water mixtures; and maximum hydrogen production of 11,021 μ mol h−1 g−1 is obtained over 1 wt% cobalt doped TiO2 in 5% glycerol aqueous solutions. Furthermore, to evaluate some reaction parameters such as cobalt wt% on TiO2, glycerol concentration, substrate effect (alcohols) and pH of the solution on the hydrogen production activity are systematically investigated. When the catalysts are examined under UV irradiation, a 3–4 fold increase in activity is observed where this activity seems to decrease with time; however, a continuous activity is observed under solar irradiation on these catalysts. The decreased activity could be ascribed the loss of cobalt ions under UV irradiation, as evidenced by EDAX and TEM analysis. A possible explanation for the stable and continuous activity of cobalt doped TiO2 photocatalysts under solar irradiation is proposed.

The present study investigates the optimization of hydrogen (H2) production with in-situ catalytic adsorption (ICA) steam gasification by using a pilot-scale fluidized bed gasifier. Two important response variables i.e. H2 composition (in percent volume fraction, %) and H2 yield (in g kg of biomass-1) are optimized with respect to five process variables such as temperature (600 °C to 750 °C), steam to biomass mass ratio (1.5 to 2.5), adsorbent to biomass mass ratio (0.5 to 1.5), superficial velocity (0.15 ms-1 to 0.26 ms-1) and biomass particle size (350 µm to 2 mm). The optimization study is carried out based on Response Surface Methodology (RSM) using Central Composite Rotatable Design (CCRD) approach. The adsorbent to biomass mass ratio is found to be the most significant process variables that influenced the H2 composition, whereas temperature and biomass particle size are found to be marginally significant. For H2 yield, temperature is the most significant process variables followed by steam to biomass mass ratio, adsorbent to biomass mass ratio and biomass particle size. The optimum process conditions are found to be at 675 °C, steam to biomass mass ratio of 2.0, adsorbent to biomass mass ratio of 1.0, superficial velocity of 0.21 m/s that is equivalent to 4 times the minimum fluidization velocity, and 1.0 mm to 2.0 mm of biomass particle size. The theoretical response variables predicted by the developed model fit well with the experimental results.