Effects of Electrode Structure and Packing Materials on Conversion of Methane and Carbon Dioxide into Synthesis Gas

Synthesis gas is a versatile feedstock for many synthesis processes. There are several conventional reactions to produce synthesis gas i.e. steam reforming, partial oxidation, and carbon dioxide reforming but these catalytic processes have to be operated at high temperatures. Because of non-equilibrium property of low temperature plasma, it is thought to be an alternative way to drive the methane reforming reaction to synthesis gas instead of high temperature catalytic processes. In this study, synthesis gas production from methane using an ac corona discharge was conducted with and without catalysts. To study partial oxidation of methane, air was used as feed gas for reducing investment and operating cost as compared to pure oxygen. The methane conversion dropped dramatically but oxygen conversion increased with addition of ethane to the feed gas. The nitrogen in air not only acts as a dilute gas but also affects the reactions. The results show that oxygen is the most effective active species to reduce carbon formation and increases methane conversion as well as lower the specific energy consumption. For this reason, steam reforming could not be operated alone under corona discharge to convert methane into synthesis gas because of the carbon formation. For carbon dioxide reforming with methane in low temperature plasmas, methane and carbon dioxide conversions both increased with increasing voltage, gap width, and carbon dioxide to methane feed mole ratio but decreased with increasing frequency and flow rate. Under the studied conditions, methane conversion was always higher than carbon dioxide conversion. Sinusoidal and square waveforms gave negligibly different results of the reactant conversions and the product distribution of partial oxidation of methane with air and carbon dioxide reforming with methane. To find the way to increase the efficiency of producing synthesis gas, the partial oxidation of methane with carbon dioxide was carried out in the presence and absence of Pt loaded KL zeolite (Pt/KL) and Pt/ZrO₂. The results showed that the combination of catalyst and electric discharge gave a higher oxygen conversion but a little bit lower methane conversion. The presence of catalyst did not show that synergetic effect on both partial oxidation and carbon dioxide reforming. The challenging method to improve synthesis gas production efficiency by introducing water in feed steam was investigated. Combined carbon dioxide and steam reforming with methane produced higher methane conversion and CO/C₂ ratio than either carbon dioxide or steam reforming. In case of the combined partial oxidation and steam reforming, the energy consumed to convert a methane molecule decreased dramatically from 68 to 13 eV/m[subscript c] with increasing the percentage of watervapor from 0 to 50% at a CH₄/O₂ ratio of 2:1

Coal is the main energy source in China, and coal chemistry wastewater treatment has always been a research hotspot. For the large amount of concentrated organic wastewater, high cost caused by complex treatment process is the key issue. In this paper, the fixed bed Lurgi gasifier wastewater coupled with solid oxide cells (SOCs) system is employed for its treatment. Based on Aspen Plus software, the purified methane from marsh gas is sent to solid oxide fuel cell (SOFC) for electricity generation. While carbon dioxide separated from biogas purification and acid gas removal enters solid oxide electrolysis cell (SOEC) to produce syngas by co-electrolysis with steam.The simulation results show that the efficiency of SOFC is 48.5 %. The generated electric energy can be used for auxiliary equipment in wastewater treatment and SOEC to produce syngas, recycling of carbon dioxide. SOEC with wind power of 12.84 MW is enough to treat the waste gas generated by the 1,100 t/h Lurgi gasification wastewater treatment process. Economically, the cost of producing syngas, with high purity and fewer contaminant contents, is about 0.126 $/Nm3. It can be used to produce various chemicals, so as to further improve the economic benefit of wastewater treatment.

Nowadays, syngas production from renewable energy sources particularly by methanation process has taken great interest. The aim of the process is energy saving by converting surplus produced energy into a truthful chemical product. Methanation reactor outlet stream contains a gas mixture which is not feasible to be used directly in distributing grids, where a higher purity of methane is necessary to obtain the highest power density. To reach the different grades of methane (for heat, electricity and vehicle fuels applications), various purification levels should be provided for syngas. For use as a fuel, elimination of carbon dioxide and water is needed, because water affects negatively on the mechanical components within the vehicles’ engine equipment. Moreover, CO2 removal should be carried out to enhance heat quality of methane and cause less pollution in the atmosphere. In the current study, the performance of a combination of flash separator and hollow fiber membranes for syngas purification was studied. For this purpose, a flash separator model was implemented to condense water from the wet feed. Then for the elimination of CO2 from methane, a hollow fiber membrane system was considered. Therefore, a unit operation user model in FORTRAN was developed to incorporate into Aspen Plus® V8.6. Different designs and arrangements of membrane modules were compared, and the best result was to purify methane up to 98 %vol. obtained using a two-stage gas permeation system with recycle streams. The model scheme can be beneficial in the design and performance analysis of a complex methanation plant system prior to practical realization.

The Pd/MOX/HfO2 p-i-n diodes on Si substrate were developed for methane gas (CH4) sensing applications. Firstly, the p(100) Si substrates were etched by AgNO3 mixed HF solution to form nanorod structure. Then the intrinsic layer HfO2 film was deposited on the Si nanorods with radio frequency sputtering system, and followed by deposition of various metal oxide such as WO3、SnO2、ZnO as sensing elements. The sensing element was examined using XRD、AFM and SEM, respectively for crystallinity, surface roughness and morphology. Finally, Pd metal was deposited thermally on the top as the catalyst and electrode contact to complete the device. We optimized the CH4 gas sensor performances through the following studies :(1) using different intrinsic layer materials such as p/n、HfO2、SiO2、TiO2 , (2) to deposit HfO2 film with varying O2/Ar flow ratio, (3) comparing the 3D nanorod structure to the conventional 2D thin film p/n diode one , and(4) use of different metal oxides such as WO3、SnO2、ZnO as sensing element. Experimental results show the intrinsic layer of hafnium oxide with oxygen atomic ratio of 5/1 is best dielectric for reduction of off leakage current. Besides, the 3D p-i-n nanostructure enhances the sensitivity of the sensor, from 498.5% of the conventional 2D thin film type to 1652%. In addition, under 200 oC, 3V reverse bias and 100ppm methane ambient, the WO3 sensing element can attain the highest sensitivity of 152.9%, which is more than 85.5% and 21.9% for SnO2 and ZnO, respectively. Furthermore, the WO3 has the fast response time of 20 sec and the highest selectivity compared with hydrogen and carbon dioxide gases. In this work, under 200 oC and 100ppm ambient, the developed 3D nanorod p-i-n CH4 sensor has the best performance of 152.9% and 20 sec, respectively for sensitivity and response time. The performances are better than that of 18% and 52.2 sec for the reported Pt/ZnO/Zn MSM Schottky diode under same conditions.

The methane reforming of carbon dioxide reaction could transform the greenhouse gas CH4 and CO2 into syngas CO and H2. The syngas could be used to produce methanol or some high value organic compounds. In order to enhance the reaction activity, stability, and carbon resistibility of the LaNiO3 catalyst used in the reforming reaction, the catalyst was prepared by citrate method and promoted by adding Mg, Ce or supported by α-Al2O3. Finally, LaNiO3, LaNi0.94Mg0.06O3, La0.96Ce0.04Ni0.94Mg0.06O3, and 5wt.% LaNi0.94Mg0.06O3 / α-Al2O3 catalysts would be discussed and compared in the catalytic performance. The LaNiO3 phase was formed at 600°C initially from precursor prepared by the cictrate method. The specific surface area and particle size were 9.06 m2/g and about 91.3 nm respectively of LaNiO3 catalyst pre-heated at 350°C for 0.5 h and calcined at 700°C for 2 h. The conversion of CH4 and CO2 were 76.2% / 77.9% respectively when LaNiO3 catalyst reacted at 700°C, but the reaction was forced to terminate due to the serious carbon deposition after 1 h. To improve the LaNiO3 catalyst used in the methane reforming of carbon dioxide reaction, magnesium was introduced as promoter to catalyst by two steps. First, the LaNi1-xMgxO3 catalyst was prepared by citrate method and discussed the best Mg adding content. And LaNi0.94Mg0.06O3 showed the best catalytic performance at 700°C, the CH4/CO2 conversion reached to 62.7% / 79.3%. Second, to improve the catalytic performance and carbon resistability of catalyst, the LaNi1-xMgxO3 catalyst was promoted by co-doping and supported method. In co-doping way, Ce was adding to LaNi0.94Mg0.06O3 catalyst with different content. And La0.96Ce0.04Ni0.94Mg0.06O3 showed the best catalytic performance at 700°C, the CH4/CO2 conversion reached to 75.9% / 91.4%. In supported method way, LaNi0.94Mg0.06O3 was supported by α-Al2O3 with particle size 200 nm. 1 g of 5wt. LaNi0.94Mg0.06O3 / α-Al2O3 catalyst showed the best catalytic performance, carbon resistability, and stability in different using amounts. The CH4/CO2 conversion reached to 88.9% / 98.1%. It was only 1wt.% carbon deposition amount after 2 h activity reaction. And it could maintain the activity and stability(duribility) after reaction at 700°C for 8 h. It was also superior in these four catalysts. Key words: Catalytic, LaNiO3, CH4, CO2, dry reforming.

To investigate carbon dioxide and methane emissions from the river water, mercuric chloride was added to the water for retarding microbial activities during the period from water sampling to laboratory measurement. But the effects of mercuric chloride on emissions of these green house gases from water remain unknown. Therefore, carbon dioxide and methane emissions from water of Tamsui River with different amounts of saturated mercuric chloride solution (69 mg/mL at 20℃) were determined at 25℃ for 6 days. Carbon dioxide and methane emissions decreased with increasing amount of saturated mercuric chloride solution added from 50 to 600 μL (3.45-41.4 mg) in 100 mL water. The gas emissions decreased slightly when the amount of saturated mercuric chloride was higher than 200 μL (13.8 mg). Carbon dioxide and methane emissions decreased linearly with the amount of saturated mercuric chloride supplemented between 0 and 100 μL (0-6.9 mg). The effect of bottle color on the carbon dioxide and methane emissions was studied with colorless and brown-colored bottles. Water in the brown-colored bottles had higher carbon dioxide and methane emissions than in the colorless bottles. The downstream area of Tamsui River had the highest carbon dioxide and methane emissions, followed by the middle-stream area, and the upstream area was the lowest due to the high pollution in the downstream area. Therefore, addition of 100 μL saturated mercuric chloride solution (6.9 mg) in 100 mL of water to retard the microbial activities after sampling in the fields for measurement of greenhouse gases emissions from water is a feasible method.

Major concerns about the effects of increasing fossil fuel consumption on the environment and energy security have prompted the development of sustainable and environmentally-friendly energy conversion and storage technologies based on electrochemical processes (e.g. water electrolysers, batteries and supercapacitors). Electrode materials are a key component of these technologies, and high-performance electrode systems are essential for the realization of a clean-energy-based economy. Numerous efforts have been made to develop advanced electrode materials for energy conversion and storage applications. However, current electrode synthesis methods are usually energy-intensive, not environmentally friendly, difficult to scale, or costly to produce. This thesis aims to utilize electrode structure engineering to develop highperformance electrodes based on earth-abundant materials via low-cost, energy-efficient and green synthesis strategies. Further, the applications of these electrodes in various energy conversion and storage applications are explored. Nickel-iron oxides or hydroxides are considered promising electrocatalysts for the oxygen evolution reaction, featuring a high activity and long cycling life in alkaline solution. A room temperature, electroless method has been developed here to grow nickel-iron hydroxides on a nickel foam current collector. The activity of nickel foam for the oxygen evolution reaction can be remarkably enhanced by simply immersing the nickel foam in a ferric nitrate solution at room temperature. During this process, the oxidation of the nickel foam surface by ferric nitrate ions increases the near-surface concentration of hydroxide ions, which results in the in situ deposition of a highly active, amorphous nickel-iron hydroxide layer. This phenomenon is described in Chapter 2 of this thesis. Carbon cloth is a widely-adopted current collector for the fabrication of electrodes. A facile, two-step method has been investigated here to turn commercial carbon cloth into a high-performance electrode for zinc-air batteries. Mild acid oxidation followed by air calcination directly activate carbon cloth to generate uniform, nanoporous and superhydrophilic surface structures with optimized, oxygen-rich functional groups and dramatically increased surface area. This two-step-activated carbon cloth exhibits superior bifunctional oxygen electrocatalytic activity and durability. A rechargeable, flexible zinc-air battery using the activated carbon cloth as a binder-free, flexible air electrode yields a remarkably high peak power density, high flexibility, and good cycling performance, with a small charge-discharge voltage gap. This work is elaborated in Chapter 3. Cost-effective synthesis of large-scale, uniform electrode materials with high activity and cycling stability is challenging. In Chapter 4, a reaction environment confinement strategy for scalable and reproducible production of nanostructured materials is proposed. Nickel foam is simply immersed in metal nitrate aqueous solution, with the volume of solution per unit area of nickel foam kept very low. A precisely designed reactor with a spiral tunnel ensures the same width of solution on each side of the nickel foam. The reaction environment is confined to ensure reproducible and uniform synthesis of nanostructured materials across the Ni foam. This approach has the largest REAVC (ratio of electrode area to precursor volume consumption) value reported so far, 2.0 cm2 mL-1. The synthesized nickel-iron hydroxides/nickel foam electrodes with uniformity in both microstructure and electrochemical properties exhibit remarkable activity for both the oxygen evolution reaction and hydrogen evolution reaction. Manganese oxides are a class of promising electrode materials for high performance supercapacitors. However, not all types of manganese oxides with different phases are electrochemically active, and their crystal structures have a considerable effect on their capacitance. In Chapter 5, a facile strategy is developed for the transformation of manganese oxide from the orthorhombic to birnessite crystal structure. The product exhibits significantly enhanced electrochemical performance as a supercapacitor electrode. This work opens up new possibilities for changing the crystal structure of manganese oxides towards optimized properties in electrochemical applications. This thesis makes significant contributions to our understanding of electrode structure engineering, materials science and electrochemical energy conversion and storage through: (i) designing novel nanostructured nickel-foam-based electrode systems with high electrocatalytic activity towards water oxidation via a simple immersion strategy at ambient temperature; (ii) developing facile activation procedures to endow commercially available, inactive carbon cloth with oxygen-rich functional groups and high oxygen electrocatalytic activity; (iii) controlling ion diffusion in a confined zone for uniform deposition of active materials over large-size electrodes, electrodes useful for various electrochemical applications; (iv) probing the phase transformation of manganese oxides from orthorhombic to birnessite, a material with enhanced electrochemical performance; (v) investigating the growth mechanisms of these advanced electrode materials to understand the origin of their exceptional activity.

Natural gas, even more biogas, comply with this requirement but gas wells in the most areas are rather economically not accessible due to infrastructural or legislative requirements. The demands of small-scale module natural gas liquefaction plant have been gained considering attentions in recent years. In natural gas liquefaction plant, the core heat transfer equipment - efficient heat exchanger design and cold box systems integration technology promote the system design more compact and efficient. However, traditional plate-fin heat exchanger that be widely adopted as the core heat exchanger has strict purification standard definition, <50ppm for CO2 and <10ng/Nm3 for mercury, to prevent carbon dioxide (CO2) freezing and mercury corrosion inside aluminum material heat exchanger, which cause pretreatment system to large dimension and high cost. In this paper, a novel cold box with brazed plate heat exchangers (BPHE) for small-scale module LNG plant is proposed and designed. Firstly, the methane (CH4) /CO2 gas mixture cooling-down process are experimental conducted in a typical BPHE. The influences of carbon dioxide concentrations on solid precipitation from room temperature to liquid CH4 temperature are investigated, considering the flow resistance and heat transfer efficiency for natural gas liquefaction process. The maximum allowable carbon dioxide concentrations without clogging the flow channel of the plate heat exchanger and deteriorating the heat transfer efficiency under different pressures (2.5-5.5MPa) during the cooling process are obtained. Based on the research results, an optimized technology package of the cold-box has been designed and fabricated to achieve the practical application in a small-scale skid-mounted natural gas liquefaction process including cryogenic CO2 separation. First results and further optimization points will be discussed as well.

To investigate the effect of mercuric chloride on carbon dioxide and methane emissions from water, different amounts of saturated mercuric chloride were added to the water of Kaoping River and Chenching Lake, and incubated at 25℃ for 6 days. Carbon dioxide and methane emissions decreased with increasing the amount of saturated mercuric chloride (69 mg mL(superscript -1) at 20℃) addition from 50 to 600 μL (3.45-41.4 mg) in 100 mL of water. Carbon dioxide and methane emissions decreased slightly when the amount of saturated mercuric chloride was higher than 200 μL (13.8 mg). Carbon dioxide and methane emissions had linear correlation with the amount of saturated mercuric chloride supplement between 0 and 100 μL. The brown color bottle had higher carbon dioxide and methane emissions from water than those of colorless bottle. The down-stream area of Kaoping River had the highest carbon dioxide and methane emissions, followed by the mid-stream area, and the upstream area and Chenching Lake had the lowest values. High carbon dioxide and methane emissions at the down-stream area might be due to high pollution. Therefore 100 μL of saturated mercuric chloride (6.9 mg) added in 100 mL of water to retard the microbial activity is a feasible method during the measurement of greenhouse gases emissions from water.

This thesis employs a range of computational modelling techniques to explore the structure, properties and catalytic activity of yttrium stabilised zirconia (YSZ) with a focus on its functions as a catalyst in methane reforming by partial oxidation. The surface and bulk properties of the material are explored, including the use of an exhaustive search of all possible defect configurations at a low yttrium loading in a bulk and a surface system allowing conclusions to be drawn about the relationship between defect configurations and stability. One significant property of YSZ materials is their ability to become oxygen ionic conductors at high temperatures, which is crucial to their use in solid oxide fuel cells and may be significant in catalytic applications. This thesis presents results of calculations designed to explore the effects of surfaces and defects on the ionic conductivity of YSZ materials, presenting evidence that oxygen conduction may be significantly enhanced at the surfaces of the material. Calculations using electronic structure techniques are carried out to examine the catalytic properties of YSZ. Initially potential surface active sites are characterised. The surface model is then shown to strongly adsorb and activate molecular oxygen, carbon dioxide and water from the gas phase. The energetics and electron movements in these surface interactions are described. These results provide the basis for investigations of reforming reactions in subsequent chapters and will be of interest in investigations of other catalytic processes over YSZ materials. A novel mechanism of methane C-H bond activation is reported over YSZ, activated by the presence of an adsorbed partially reduced O2 species. The mechanism is investigated in detail, including the use of two electronic structure techniques to allow mechanistic details to be proposed and activation energy estimated. It may be that this mechanism is more generally applicable to oxidative C – H bond activation over many metal oxide materials.

Laminate zeolite structure prepared using papermaking techniques for carbon dioxide capture: synthesis, characterisation and performance

1.1 Carbon dioxide 1.1.1 Significance Theoretical and experimental investigations of weakly bound molecular complexes are of fundamental importance for understanding of molecular interactions responsible for properties of condensed phases. The carbon dioxide clusters provide a simple model for such studies. Carbon dioxide has been a subject of many papers in recent years. Some deal with its role in the biosphere, mainly the greenhouse effect. The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapor, carbon dioxide, nitrous oxide, and methane, for example) trap energy from the sun. Without these gases, heat would escape back into space and Earth’s average temperature would be lower. Other investigations deal with the significance of carbon dioxide for the nutrition for plants, the supercritical carbon dioxide as a green solvent for extraction and synthesis and the existance of carbon dioxide in the atmospheres of Mars and Venus. 1.1.2 Previous Investigations The carbon dioxide dimer was first detected in 1966 by Leckenby et al.[?]. The slippedparallel( C2h - geometry) structure of the carbon dioxide dimer was shown experimentally in references [?] - [?](high-resolution infrared) and [?](Raman studies) to be the stable one. That the structure of the dimer is slipped-parallel(C2h - geometry) was shown in [?] as a result of quantum-chemical calculations. The dimerisation equilibrium constant was evaluated using partition functions [?]. 1.1.3 Dimer formation A new method is developed to calculate the equilibrium constant of weak dimer complexes and the life time of the dimer in the gas phase. Actually it is not an easy task to define when approaching monomers form a dimer. In the new method the defined time correlation function from the molecular dynamics simulations shows a slow decay corresponding to real dimers and a fast decay corresponding to unstable collisions. The results obtained for the carbon dioxide dimerization are compared to results obtained by two other methods using partition function and second virial coefficient. A possible application is to predict the dimer carbon dioxide concentration in the atmospheres of Mars and Venus. 1.2 Rebinding dynamics of nitric oxide to the V68F Myoglobin mutant In connection with the work on rebinding molecular dynamics of nitric oxide to the V68F Myoglobin mutant I would like to emphasize that the study of reactive processes in chemically and biologically relevant systems is a topic of much current interest. For fast reactions (proton transfer, ligand rebinding) computer simulations are a useful means to investigate and understand the energetics and dynamics of chemical reactions. A new surface-crossing algorithm suitable for describing bond-breaking and bond-forming processes in molecular dynamics simulations is presented in [?]. The method is formulated for two intersecting potential energy manifolds which dissociate to different adiabatic states. During simulations, crossings are detected by monitoring an energy criterion. If fulfilled, the two manifolds are mixed over a finite number of time steps, after which the system is propagated on the second adiabat and the crossing is carried out with probability one.

The urgency to develop new technologies that harness energy and natural feedstocks in a sustainable fashion has never been more apparent. With global power consumption growing at an exponential rate, only one resource is truly capable of powering the planet: the sun. Sunlight is reliable, clean, and free. Significant resources have been pledged to develop and refine solar energy devices that convert photons into electricity (i.e. photovoltaics), but the sun’s intermittency and the poor overlap of solar irradiance with global power demand a different strategy. In light of these limitations, we have proposed a device which converts solar energy into reduced chemical fuels (e.g. dihydrogen or methane) that can be indefinitely stored and easily transported. In principle, the only required inputs are sunlight, an earth-abundant feedstock such as carbon dioxide, protons (H + ), and reducing equivalents (e - ). The source of these protons and electrons must be abundant and ubiquitous—we chose water. Despite the 2-billion-year history of plants performing water oxidation to produce molecular oxygen, protons, and electrons (Photosystem II), our understanding of this complex 4H + /4e - process has been severely limited. Only recently have high-performing, earth-abundant heterogeneous electrocatalysts been reported that can be scaled up to make functioning devices. This dissertation describes progress on both the synthetic and mechanistic fronts in developing earth-abundant heterogeneous water oxidation catalysts for solar-driven water splitting. We have synthesized nanoparticulate Ni-Fe catalysts with the highest measured activity on flat electrodes to date. We carefully characterized these materials spectroscopically to determine that edge-site iron was active in catalysis. We then undertook novel in-situ spectroelectrochemical techniques in non-aqueous media to identify the active iron species, which is surprisingly a cis -dioxo-iron(VI) corner site. The data also indicate that geminal iron-oxo coupling may be the operative mechanism of O-O bond formation, a new scheme with potential biological relevance. Finally, we have expanded our goal to include sustainably reducing other feedstocks, such as carbon dioxide and hydrocarbons. In doing so, we aim to make pharmaceuticals, polymers, and other high-value products from sunlight and water.

It has become increasingly important to control carbon dioxide (CO¬2) emissions and at the same time generate fuel sources to meet the growing global energy consumption need. CO2 (dry) reforming of methane (DRM) is a viable process as it generates fuel (syngas) and utilises greenhouse (CH4 and CO2) gas at the same time. The success of this process relies on the development of suitable noble-metal free catalysts. First principle’s based computational methods, such as density functional theory (DFT), has become a powerful predictive tool for catalyst development in modern science. Therefore the main objective of this thesis work has been to investigate suitable catalysts using computational methods for gas–phase CO2 utilisation reactions. In this research work, DFT calculations provided us with the fundamental insights into the DRM mechanism over bimetallic Sn/ Ni (111) periodic model surfaces. This analysis showed that low Sn concentration on Ni surface effectively mitigates carbon formation without compromising the CO2 conversion and the syngas production, showcasing superior characteristics of the bimetallic catalyst towards carbon tolerance stability. Other heterogeneous catalysts such as Ni2P and MoP have also been studied in this thesis. Theoretical analysis of DRM reaction on the unexplored nickel phosphide Ni2P (0001) surface showcased suitable syngas production under DRM reaction temperatures with low carbon deposition formation on the surface. This was mainly attributed to a lower number of active sites available for carbon adsorption compared to oxygen on the Ni2P (0001) surface. DFT study on activation of CO2 and CO on MoP (0001) and Ni2P (0001) surfaces showcased selective CO production from CO2 to be possible on both the surfaces. Further, direct CO activation is favoured on the MoP (0001) surface. Surface bounded oxygen removal on Ni2P (0001) is reasonably favourable. Findings from this thesis work will be beneficial in developing more robust catalysts for gas phase CO2 utilisation reactions and could contribute to a better understanding of CO2 conversion processes, catalysts deactivation and thus helping to develop new families of powerful catalysts for a greener society

To quantify the greenhouse gas emissions from rivers and lakes, environmental conditions, water qualities, carbon dioxide and methane emissions were determined in the up-, mid- and down-stream areas of Kaoping River and Chenching Lake. Atmospheric carbon dioxide concentrations were 292-430, 295-453, 328-476 and 302- 449 ppm, respectively, and atmospheric methane concentrations were 1.70-2.09, 1.71-3.10, 1.70-2.86 and 1.18- 3.60 ppm, respectively. By using the headspace method with brown color bottle, carbon dioxide concentrations were determined as 198-5,437, 1,077-8,584, 3,977-10,839 and 1,537-9,902 ppm, respectively, and methane concentrations fell into the range of 2.8-231.0, 38.9-881.2, 75.3-983.1 and 31.5-4,321.5 ppm, respectively. By using the static-chamber method, carbon dioxide emission rates were -51.3-209.3, -9.6-232.4, -25.7-265.8 and -155.9-217.1 mg m^(-2) h^(-1), respectively, and methane emission rates were 0.05-1.52, 0.05-4.50, 0.26-6.12 and 0.02- 2.68 mg m^(-2) h^(-1), respectively. There is a positive correlation between methane concentration with the headspace method and emission rate with the static-chamber method. Methane emission was very significantly negativelycorrelated with dissolved oxygen (DO), significantly negatively-covrelatived with redox potential (Eh), and very significantly positively-correlated with methane concentration, carbon dioxide concentration using the head-space method, total alkalinity (ALK), and conductivity (CD) in the tested river. Carbon dioxide emission in the tested river had positive correlation with methane concentration by the head-space method. Methane emission in the test lake had very significantly positive correlation with alkalinity (ALK), significantly positive correlation with redox potential (Eh), biological oxygen demand (BOD) and chemical oxygen demand (COD). The annual carbon flows from Kaoping River into ocean from 2003 to 2007 were estimated between 3.7 × 10^5 and 1.7 × 10^6 tons.