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Table of contents
1. Introduction
2. Aim of this PhD thesis
3 Chemical utilization of carbon dioxide
3.1 CO2 emissions
3.1.1 Reduction of CO2 emissions – policies
3.2 Solutions for the reduction of CO2 emissions
3.2.1 CO2 Capture Systems
3.2.1.1 CO2 separation technologies
3.2.2 Applications of CO2
3.2.2.1 General application of CO2
3.2.2.2 Enhanced Fossil Fuel Recovery
3.2.2.3 Biological use of CO2
3.3 Utilization of CO2 as a chemical feedstock
3.3.1 Physicochemical properties of carbon dioxide – CO2 activation
3.3.2 Urea synthesis
3.3.3 Synthesis of salicylic acid
3.3.4 Synthesis of carbonates, cyclic carbonates and polycarbonates
3.3.5 Production of inorganic substances – mineralization
3.3.6 CO2 – gasification of coal
3.3.7 CO2 – Oxidative Dehydrogenation (ODH)
3.3.8. Production of synthesis gas
3.3.9 Hydrogenation of CO2
3.3.9.1. Methanol production from CO2
3.3.9.2 DME production
3.3.9.3 Methanation – production of CH4
3.3.9.4 Production of formic acid
3.3.9.5 Hydrocarbons synthesis
4 Dry Reforming of Methane
4.1 Comparison of DRM with respect to other reforming processes
4.2 Thermodynamics of the DRM
4.2.1 Thermodynamics of side reactions
4.2.2 Optimal conditions for DRM reaction
4.3. Catalysts for dry reforming of methane
4.3.1 The role of active component
4.3.2 Nickel-based catalysts
4.3.2.1 The role of support
4.3.2.2 The role of promoters
4.3.2.3 Conclusions
4.4 Reaction Mechanism
4.5 Applications of DRM
4.5.1 Industrial experience with large scale reforming of CO2-rich gas
4.5.1.1 CALCOR process
4.5.1.2 SPARG process
4.5.2 Potential future applications of DRM reaction
4.5.2.1 Chemical Energy Transmission and/or Storage Systems (CETS)
4.5.2.2 DRM for production of chemicals
5 Hydrotalcites and hydrotalcite-derived materials
5.1 Structure and composition
5.2 Properties
5.2.1 Thermal stability
5.2.2 Memory effect
5.2.3 Acid-base properties
5.2.4 Anion Exchange Capacity
5.3 Synthesis and modification of hydrotalcites
5.3.1 Co-precipitation
5.3.2 Urea method
5.3.3 Sol-Gel method
5.3.4 Salt-oxide method (Induced Hydrolysis)
5.3.5 Reconstruction
5.3.6 Anion-exchange
5.3.7 Hydrothermal treatment
5.4 Applications of hydrotalcite-like materials
5.4.1 Adsorption of CO2
5.4.2 Catalysis
5.5 Hydrotalcites in DRM
5.5.1 Ni/Mg/Al and Ni/Al hydrotalcite-derived catalysts
5.5.2 Ce promotion
5.5.3 Other promoters
5.5.2 Advantages of hydrotalcite-derived catalysts
6 Experimental
6.1 Thermodynamic analysis of DRM process
6.2 Catalysts preparation
6.2.1 Co-precipitation
6.2.2 Reference catalysts
6.2.3 Method of nickel introduction
6.2.4 Influence of nickel loading in brucite-like layers
6.2.5 The influence of promoters (Ce and/or Zr)
6.2.6 Calcination
6.2.7 Catalyst activation
6.3 Characterization of the catalysts
6.3.1 X-Ray Diffraction (XRD)
6.3.2 Infrared spectroscopy
6.3.3 Low temperature N2 sorption
6.3.4 Elemental analysis
6.3.5 Temperature Programmed Reduction (H2-TPR)
6.3.6 Temperature Programmed Desorption of CO2 (CO2-TPD)
6.3.7 Scanning Electron Microscopy (SEM)
6.3.8 Transmission Electron Microscopy (TEM)
6.3.9 Thermogravimetric measurements (TG)
6.4 Dry reforming of methane catalytic tests
7 Thermodynamic analysis
7.1 The influence of temperature on equilibrium concentrations of reactants during DRM process
7.1.1 The effect of CH4/CO2/Ar feed gas composition on equilibrium concentrations of reactants during DRM process
7.2 The influence of pressure on reactant concentration during DRM
7.3 Thermodynamic limitations in tested reaction conditions
8.1 Composition, structural and textural properties of the hydrotalcite and hydrotalcite-derived materials
8.1.1 The influence of calcination temperature on hydrotalcite structure
8.2 The structural properties of the reduced catalysts
8.3 Reducibility of Ni species and acid-base properties
8.4 Activity and selectivity in DRM
8.4.1 Catalytic tests at temperature range 550-850°C
8.4.2 Low temperature DRM (isothermal tests at 550°C)
8.5 Conclusions
9 The effect of nickel content in brucite-like layers
9.1 Physicochemical features of the hydrotalcite precursors and the derived catalysts
9.1.1 XRD analysis of synthesized hydrotalcites and calcined materials
9.1.2 FTIR experiments
9.1.3 Elemental analysis
9.1.4 Texture of the prepared catalysts
9.1.5 Reducibility of hydrotalcite-derived mixed oxides
9.1.6 Basicity of hydrotalcite-derived materials containing nickel in brucite-like layers
9.1.7 TEM and SEM analysis of calcined and reduced catalysts
9.1.8 XRD analysis of reduced catalysts
9.2 Activity, selectivity and stability of the hydrotalcite-derived catalysts during DRM runs
9.2.1 The characterization of the spent catalysts
9.2.2 On the influence of CH4 decomposition
9.2.3 On the effect of catalysts basicity on their catalytic performance in DRM
9.2.4 On the influence of temperature on catalytic activity of Ni/Mg/Al hydrotalcite-derived catalysts
9.2.5 On the effect of feed gas composition
9.2.6 Stability tests
9.3 Conclusions
10 Influence of promoters (Ce, Zr)
10.1 Physico-chemical features of the Ce, Zr and CeZr doped HT-derived catalysts
10.1.1 XRD analysis of fresh, calcined and reduced hydrotalcite-derived catalysts
10.1.2 The elemental analysis of Ce and/or Zr promoted catalysts
10.1.3 FTIR experiments for Ce and/or Zr promoted hydrotalcites
10.1.4 Textural properties of Ce and/or Zr promoted hydrotalcite-derived catalysts
10.1.5 Reducibility of Ce and/or Zr promoted hydrotalcite derived catalysts
10.1.6 Basicity of Ce and/or Zr promoted hydrotalcite-derived catalysts
10.1.7 SEM and TEM analysis
10.2 Effect of Ce-promotion
10.2.1 Activity and selectivity in DRM at 550°C
10.2.2 The influence of the temperature
10.2.3 Characterization of the spent catalysts
10.2.4 On the effect of the feed gas composition
10.2.5 Stability tests for 24h
10.3 The comparison of Ce and Zr promoters
10.3.1 Activity and selectivity in DRM at 550°C
10.3.2 The influence of the reaction temperature
10.3.3 Characterization of the spent catalysts
10.3.4 Stability tests for 24h
10.4 Conclusions
11 Conclusions
References
Summary
