No / Methane reforming in the presence of hydrogen sulfide (H2SMR) is not only conspicuous in terms of producing valuable material but also because of its advantages in obtaining hydrogen as a clean fuel. Substitution of traditional hydrogen production processes such as methane steam reforming (MSR), elimination of natural gas amine–based H2S removal, and sulfur recovery processes have attracted much attention. The current hydrogen production is associated with consuming energy that is usually supplied by burning fossil fuels. Thus, producing hydrogen by current high greenhouse gas emitter methods seems not to be a rational approach to benefit from this clean energy source. Additionally, H2SMR with the potential of producing four moles of hydrogen and one mole of CS2 from methane could be a promising alternative as providing the opportunity to benefit from producing cleaner fuels and simultaneously making CS2 that is used for the production of more valuable products. This chapter reviews the recent progress in CS2 production from methane reforming in the presence of H2S and brings the effect of dominant parameters on this process.

There is a global need for sustainable, renewable and clean energy sources. Microbial production of hydrogen from renewable carbon sources, biorefinery compounds such as succinic acid or from food and drinks industry waste meets all these criteria. Although it has been studied for several decades, there is still no large scale bio-hydrogen production because the rate and yield of hydrogen production are not high enough to render the process economical. The dependency of biological hydrogen production of incipient light energy is also an important factor affecting economics. In order to improve the prospects of biohydrogen as a renewable and sustainable energy alternative, the genetic and process engineering approaches should be helped and targeted by metabolic engineering tools such as metabolic flux balance analysis. The overall aim of this research was the development of computational metabolic flux balance analysis for the study of growth and hydrogen production in Rhodobacter sphaeroides. The research reported in this thesis had two approaches; experimental and computational. Batch culture experiments for growth and hydrogen production by Rhodobacter sphaeroides were performed with either malate or succinate as carbon source and with glutamate as the nitrogen source. Other conditions investigated included; i) aerobic and anaerobic growth, ii) light and dark fermentation for growth, and iii) continuous light and cycled light/dark conditions for hydrogen production. The best growth was obtained with succinate under anaerobic photoheterotrophic conditions with the maximum specific growth rate of 0.0467 h– 1, which was accompanied with the maximum specific hydrogen production rate of 1.249 mmol(gDW.h)– 1. The range of the photon flux used was 5.457 - 0.080 mmol(gDW.h)– 1. The metabolic flux balance model involved 218 reactions and 176 metabolites. As expected the optimised specific rates of growth and hydrogen production were higher than those of the experimental values. The best prediction was for hydrogen production on succinate with computed specific hydrogen production rates in the range of 2.314 - 1.322 mmol(gDW.h)– 1. Sensitivity analyses indicated that the specific growth rate was affected by the nitrogen source uptake rate under aerobic dark condition whereas the flux of protein formation had the largest effect on the specific growth rate under anaerobic light condition.

No description available.

This work describes the application of porous metal supported Pd-membranes to the water-gas shift catalytic membrane reactor in the context of its potential application to the Integrated Gasification Combined Cycle (IGCC) process. The objective of this work was to develop a better understanding of Pd-membrane fabrication techniques, water-gas shift catalytic membrane reactor operation, and long-term behavior of the Pd-membranes under water-gas shift conditions. Thin (1.5 - 16 um) Pd-membranes were prepared by electroless deposition techniques on porous metal supports by previously developed methods. Pd-membranes were installed into stainless steel modules and utilized for mixed gas separation (H2/inert, H2/H2O, dry syngas, and wet syngas) at 350 - 450C and 14.5 atma to investigate boundary layer mass transfer resistance and surface inhibition. Pd-membranes were also installed into stainless steel modules with iron-chrome oxide catalyst and tested under water-gas shift conditions to investigate membrane reactor operation in the high pressure (5.0 - 14.6 atma) and high temperature (300 - 500C) regime. After the establishment of appropriate operating conditions, long-term testing was conducted to determine the membrane stability through He leak growth analysis and characterization by SEM and XRD. Pd and Pd/Au-alloy membranes were also investigated for their tolerance to 1 - 20 ppmv of H2S in syngas over extended periods at 400C and 14.0 atma. Water-gas shift catalytic membrane reactor operating parameters were investigated with a focus on high pressure conditions such that high H2 recovery was possible without a sweep gas. With regard to the feed composition, it was desirable to operate at a low H2O/CO ratio for higher H2 recovery, but restrained by the potential for coke formation on the membrane surface, which occurred at a H2O/CO ratio lower than 2.6 at 400C. The application of the Pd-membranes resulted in high CO conversion and H2 recovery for the high temperature (400 - 500C) water-gas shift reaction which then enabled high throughput. Operating at high temperature also resulted in higher membrane permeance and less Pd-surface inhibition by CO and H2O. The water-gas shift catalytic membrane reactor was capable of stable CO conversion and H2 recovery (96% and 88% respectively) at 400C over 900 hours of reaction testing, and 2,500 hours of overall testing of the Pd-membrane. When 2 ppmv H2S was introduced into the membrane reactor, a stable CO conversion of 96% and H2 recovery of 78% were observed over 230 hours. Furthermore, a Pd90Au10-membrane was effective for mixed gas separation with up to 20 ppmv H2S present, achieving a stable H2 flux of 7.8 m3/m2-h with a moderate H2 recovery of 44%. The long-term stability under high pressure reaction conditions represents a breakthrough in Pd-membrane utilization.

A variety of unicellular green algae have the ability to photo-produce molecular hydrogen (H2). Using sunlight to power the production of H2 from water is attractive due to the abundant supply of both resources and the potential for the technology to address global warming and energy supply concerns. Increasing levels of H2 production from those currently achievable with algal systems is a necessity for the technology to become economically feasible. Green unicellular algae are rare amongst organisms in that some have an ability to switch to an H2-producing metabolism when environmental conditions become anaerobic. The process of H2 production is greatly accentuated in the light due to the role of the photosynthetic apparatus directing electron flow to hydrogenase enzymes located in the chloroplast. Difficulties in maintaining continuous systems of H2 production largely result from the O2 sensitivity of hydrogenase enzymes. As O2 is generally produced through photosynthesis, the process of H2 production has always been short-lived. Recently, a process of inducing H2 production for several days was accomplished by depriving the growth medium of sulphur (Melis et al., 2000). Lacking sulphur, photosystem II activity diminishes to a point where any O2 evolved is consumed by respiration; this leads to the culture becoming anaerobic and to the onset of H2 production. The method of sulphur depletion has proven to be very useful for studies of H2 production due to enhanced rates over longer time periods being possible. This work was performed to search for new H2-producing Australian algal species and to shed light upon the molecular and biochemical interactions occurring when algal species move from aerobic photosynthetic growth to an anaerobic H2-producing status. An assay to test new species for an H2-producing ability was developed and implemented; leading to the isolation of new H2-producing species from Australian waters. The assay involved purging algal cultures in the dark with N2, sealing them in bioreactors and then exposing them to light. Metabolic profiling performed during this assay revealed cells to rapidly enter a fermentative metabolism upon the onset of anoxia. Acetate, formate and ethanol were key metabolites produced alongside H2 during this period. Metabolomics was used as a tool to understand the biochemical interactions occurring during 120 h of sulphur depleted H2 production. Extraction protocols were developed that allowed the detection and identification of over 100 metabolites using gas chromatography coupled to mass spectrometry, nuclear magnetic resonance spectroscopy and thin layer chromatography. Shifts in primary energy metabolism when cells switch from O2 production to H2 production were revealed. Indications are that both starch and triacylglyceride accumulate during the first 24 h of sulphur depletion prior to anoxia. Following the onset of anoxia, fermentative metabolism begins, H2 is produced and amino acids generally increase. A build-up of toxic fermentative end products and a lack of sulphur are believed to cause the termination of H2 production, rather than a lack of energy reserves. Key achievements of this work have been: • The establishment of an assay that can be used for future bio-prospecting work aimed at finding H2-producing algal species. • The isolation of new H2-producing green algal species from Australian waters. • The establishment of protocols for the extraction of metabolites from small volumes (1 ml) of Chlamydomonas reinhardtii cultures for analysis on a variety of analytical platforms. • The mapping of changes in metabolism of C. reinhardtii during the switch from an aerobic environment to an anaerobic H2-producing environment. • A range of recommendations for future research that may lead to higher H2 production.

Hydrogen is known as a clean energy carrier which has the potential to play a major role in addressing the climate change and global warming, and thermochemical water splitting via the copper-chlorine cycle is a promising method of hydrogen production. In this research, thermal management of the copper-chlorine cycle for hydrogen production is investigated by performing analytical and experimental analyses of selected heat recovery options. First, the heat requirement of the copper-chlorine cycle is estimated. The pinch analysis is used to determine the maximum recoverable heat within the cycle, and where in the cycle the recovered heat can be used efficiently. It is shown that a major part of the potential heat recovery can be achieved by cooling and solidifying molten copper(I) chloride exiting one step in the cycle: the oxygen reactor. Heat transfer from molten CuCl can be carried out through direct contact or indirect contact methods. Predictive analytical models are developed to analyze a direct contact heat recovery process (i.e. a spray column) and an indirect contact heat recovery process (i.e. a double-pipe heat exchanger). Characteristics of a spray column, in which recovered heat from molten CuCl is used to produce superheated steam, are presented. Decreasing the droplet size may increase the heat transfer rate from the droplet, and hence decreases the required height of the heat exchanger. For a droplet of 1 mm, the height of the heat exchanger is predicted to be about 7 m. The effect of hydrogen production on the heat exchanger diameter was also shown. For a hydrogen production rate of 1000 kg/day, the diameter of the heat exchanger is about 3 m for a droplet size of 1 mm and 2.2 m for a droplet size of 2 mm. The results for axial growth of the solid layer and variations of the coolant temperature and wall temperature of a double-pipe heat exchanger are also presented. It is shown that reducing the inner tube diameter will increase the heat exchanger length and increase the outlet temperature of air significantly. It is shown that the air temperature increases to 190oC in a heat exchanger with a length of 15 cm and inner tube radius of 10 cm. The length of a heat exchanger with the inner tube radius of 12 cm is predicted to be about 53 cm. The outlet temperature of air is about 380oC in this case. The length of a heat exchanger with an inner tube diameter of 24 cm is predicted to be about 53 cm and 91 cm for coolant flow rates of 3 g/s and 4 g/s, respectively. Increasing the mass flow rate of air will increase the total heat flux from the molten salt by increasing the length of the heat exchanger. Experimental studies are performed to validate the proposed methods and to further investigate their feasibility. The hazards involving copper(I) chloride are also investigated, as well as corresponding hazard reduction options. Using the reactant Cu2OCl2 in the oxygen production step to absorb CuCl vapor is the most preferable option compared to the alternatives, which include absorbing CuCl vapor with water or CuCl2 and building additional structures inside the oxygen production reactor. / UOIT

Production of hydrogen is primarily achieved via catalytic steam reforming, partial oxidation,and auto-thermal reforming of natural gas. Although these processes are mature technologies, they are somewhat complex and CO is formed as a by-product, therefore requiring a separation process if a pure or hydrogen-rich stream is needed. As an alternative method, supported metal catalysts can be used to catalytically decompose hydrocarbons to produce hydrogen. The process is known as catalytic cracking of hydrocarbons. Methane, the hydrocarbon containing the highest percentage of hydrogen, can be used in such a process to produce a hydrogen-rich stream. The decomposition of methane occurs on the surface of the active metal to produce hydrogen and filamentous carbon. As a result, only hydrogen is produced as a gaseous product, which eliminates the need of further separation processes to separate CO2 or CO. Nickel is commonly used in research as a catalyst for methane cracking in the 500-700C temperature range. To conduct methane catalytic cracking in a continuous manner, regeneration of the deactivated catalyst is required and circulation of the catalysts between cracking and regeneration cycles must be achieved. Different reactor designs have been successfully used in cyclic operation, such as a set of parallel fixed-bed reactors alternating between cracking and regeneration, but catalyst agglomeration due to carbon deposition may lead to blockage of the reactor and elevated pressure drop through the fixed bed. Also poor heat transfer in the fixed bed may lead to elevated temperature during the regeneration step when carbon is burned in air, which may cause catalyst sintering. A fluidized bed reactor appears as a viable option for methane catalytic cracking, since it would permit cyclic operation by moving the catalyst between a cracker and a regenerator. In addition, there is the possibility of using fine catalyst particles, which improves catalyst effectiveness. The aims of this project were 1) to develop and characterize a suitable nickel-based catalyst and 2) to develop a model for thermal catalytic decomposition of methane in a fluidized bed.

The resources on earth are limited; thus, the demand for energy, goods and materials is surging because of the growth of the advanced technology and population. The issues of using the resources effectively and changing them into a useful energy are then important. Taiwan creates a vast amount of agricultural waste every year. The traditional way of eliminating the agricultural waste would be burned and buried. However, it is not only the agricultural waste cannot be reused and recycled, but also the problem of air pollution occurred. The objectives of this thesis are thus to transfer the agricultural waste into a useful energy. This study contents two parts. The first part changes the agricultural waste into sugar. The agricultural waste is full of wood fiber and can be transformed to sugar by a microorganism method. A cane which is a common agricultural waste is used; the wood fiber in cane will be added to the thermostable cellulolytic bacterial Geobacillus thermoleovorans T4 isolated from sugar refinery wastewater in southern Taiwan. T4 can convert wood fiber into sugar. Experimental results showed that the rate of reducing sugar is 13.77%. The second part studies the biological hydrogen production by Clostridium acetobutylicum ATCC 824, and the sugar will be added into the process. Also, this study uses ultrasonic treatment in the biological hydrogen production and calculates the natural frequency of ATCC 824. The experiment is designed using the Taguchi method for increasing hydrogen production, hydrogen production rate and hydrogen production efficiency by using an ultrasonic treatment to treat C. acetobutylicum ATCC 824. It is showed that the best combination is temperature 37¢XC, ultrasonic frequency 0.5 MHz, ultrasonic intensity 136 mW/cm2, exposure time 10 s, pH 7.5 and bacterial concentration 20%. This study can apply in bio-energy and fermentation food producing.

Hydrogen production by water-splitting using solar energy and nanostructure photocatalysts is very promising as a renewable, efficient, environmentally clean technology. The key is to reduce the cost of hydrogen production as well as increase the solar-to-hydrogen conversion efficiency by searching for cost-effective photocatalytic materials. In this dissertation, energy efficiency calculation was carried out based on hydrogen production observation to evaluate the nanomaterials activity. The results are important to gain better understanding of water-splitting reaction mechanism. Design, synthesis, characterization/properties and application of these nanomaterials was the road-map to achieve the research objectives. The design of TiO2 is selected based on unique photocatalytic and photovoltaic properties and high stability in aqueous solution. Various structures of nanocomposites TiO2 were designed according to their characteristics and potential activity. TiO2 with quantum dots, nanocomposites thin film, nanofibers, nanorods, nanowires (core/shell), nanotubes, nanopowders, nanoparticles, and nanosphere decorated with low cost metals, sensitized with dye, and doped with nitrogen are designed. Green physical and chemical synthesis methods such as sol-gel techniques, autoclave, microwave, electrospinning, wet impregnation, hydrothermal, chemical vapor deposition, template-based fabrication (porous anodic aluminium oxide membrane), drop casting, dip coating, wet coating were used to synthesize and fabricate the nanomaterials and quantum dots.Both bottom-up and top-down synthesis techniques were used. The ability to control and manipulate the size, shape/geometry, crystal structure, chemical compositions, interaction and interface properties of these materials at nano-scale during the synthesis enable to enhance their thermal, optical, chemical, electrical, …etc properties. Several characterization techniques such as XRD, XPS, EDS, SEM, UV-visible spectra, and optical microscopic and digital camera were also obtained to characterize the properties and confirm to achieve the desired design. The application or processing to test the activity of these nanomaterials for hydrogen production by water-splitting was conducted through extensive experimental program. It was carried out in a one photo-single column experimental set-up to detect hydrogen evolution. A high throughput screening process to evaluate single photo reduction catalysts was established here for simplicity, safety, cost-effective and flexibility of testing nanomaterials for water photoreduction reactivity and hydrogen generation. Therefore, methanol as electron donor or oxidation agent was mixed with water in equal volume ratio in order to prevent the oxygen evolution and only measured the time course of hydrogen production. The primary objectives of this study is to investigate the following (1) The structure-properties relationship through testing quantum dots, nanocomposites thin film, nanofibers, nanorods, nanowires (core/shell), nanotubes, nanopowders, nanoparticles, nanospheres of TiO2 decorated with metals, dye sensitization, and nitrogen-doping. (2) The role of adding electron donors/relays to solution and their effect on semiconductor surface-electrolyte interface under constant conditions such as KI, Mv 2, NaCl, NaHCO3, sea and pure water. (3) Band gap and defect engineering by cation and anion doping. (4) Quantum dots and dye sensitization effect. The nanomaterials activity evaluated based on observed hydrogen production rate (μmol/h/g) experimentally and based on the energy efficiency (percent) calculation. Major findings in this dissertation are (1) A high throughput screening process to evaluate single photoreduction catalysts for solar-hydrogen production by water-splitting was established. (2) nanofibers structure of TiO2 doped with nitrogen, sensitized with dye (Rose Bengal Sodium) and quantum dots (CuInS2), and decorated with metals (Ag) showed the high solar-to-hydrogen conversion efficiency and high hydrogen production rate (3) Simple, safe, inexpensive, robust, efficient and green physical and chemical synthesis methods were used to prepare the nanomaterials and quantum dots. (4) Gaining insight and better understanding of water-splitting reaction mechanism by (a) Studying the structure-properties relationship of nanomaterials (b) Studying the role of additives on surface-interface chemistry of semiconductor and electrolyte (c) Knowing how to reduce the electron-hole recombination reactions to enhance quantum efficiency (d) Extending the absorption of nanomaterials to harness the visible light of solar spectrum radiation by doping and defect chemistry.

Photobiological hydrogen production from organic materials occurs with the help of illumination and under aerobic conditions within photobioreactors. Novel designs are needed in order to increase the light conversion efficiency and to improve the biological hydrogen production. In this thesis, purple non sulfur bacteria Rhodobacter sphaeroides O.U. 001 was employed as the hydrogen producing microorganism. Two different types of photobioreactors, namely oscillatory helical photobioreactor and recycling helical bioreactor, were devised and successfully operated for bacterial growth and hydrogen production. Total liquid capacity of the pneumatically driven oscillatory flow helical tubular photobioreactor was 11.5 L, and 4.5 L of which was occupied by the bacterial culture. The bacteria grew very well both in malate-based and acetate-based media under nitrogen atmosphere. The bacteria sustained their vitality 24 days before the system was shut down. The recycling helical tubular photobioreactor, which was developed for hydrogen production, had a fully occupied total volume of 6.5L. The bacteria produced approximately 1.9L of hydrogen in four days on malate-based media. The hydrogen production rate was 0.009LH2/Lculture.h. The effects of molecular nitrogen gas and the sodium glutamate concentration on the growth of hydrogen producing photosynthetic bacteria Rhodobacter sphaeroides O.U.001 in the reactor were also examined in 500ml-bottles. The bacterial growth curves did not show any difference at the control medium containing 15mM of acetate and 10 mM of sodium glutamate. However, other bottles containing a lesser amount of N-source was found to grow earlier under the nitrogen atmosphere. Besides, even a 15/2 acetate/sodium glutamate ratio was observed to be sufficient to grow the bacteria for inoculation, and to spend extra sodium glutamate was not necessary. The novel designs developed in this study aim to improve the biological hydrogen production by photosynthetic bacteria, and to provide new ways in adaptation of photobiological systems to outdoor conditions for large-scale applications.