Ammonia Synthesis Catalysts

Transcription

1 SHANGHAI Ammonia Synthesis Catalysts Innovation and Practice Huazhang Liu Zhejiang University of Technology, China CO Chemical Industry Press \[p World Scientific NEW JERSEY LONDON» SINGAPORE BEIJING HONG KONG TAIPEI CHENNAI

2 Contents Preface vi Foreword x Chapter 1. Historical Evolution of Catalysts for Ammonia Synthesis Introduction of Catalysts for Ammonia Synthesis Co-Mo hydrogenation catalysts Zinc oxide desulfurizer Hydrocarbon steam reforming catalysts CO high-temperature shift catalysts CO low-temperature shift catalysts Methanation catalysts Refine catalysts Historical Retrospect of Catalysts for Ammonia Synthesis Basic studies on physical chemistry of ammonia synthesis reaction Realization of ammonia synthesis under high pressure Development of fused iron catalysts for ammonia synthesis Development of ammonia synthesis catalysts in China Development trend of ammonia synthesis catalysts Development of Magnetite (Fe304 j Based Fused Iron Catalysts Magnetite (Fes04) based fused iron catalysts Development of Fe304 based catalysts containing cobalt Discovery of Wustite Based Fused Iron Catalysts Search for new breakthrough of the technique Activity of wustite (Fei_xO) based catalysts Reduction of Fei_xO based catalysts Technical characteristics of wiistite-based catalysts Significance of the Fei_xO-based catalysts in theory Industrial application 50 xiii

3 xiv Ammonia Synthesis Catalysts: Innovation and Practice 1.5 Discovery of Ruthenium Based Catalysts Properties of the elements in the activation of dinitrogen Properties of the elements in ammonia synthesis Alloying effect Activated carbon supported ruthenium catalysts for ammonia synthesis 59 References 62 Chapter 2. Catalytic Reaction Mechanisms of Ammonia Synthesis Introduction The development of catalysis theory The chemical essences of catalysis The methodology of catalytic investigation Adsorption and Heterogeneous Catalysis Adsorption and heterogeneous catalysis Non-uniformity of the surface of heterogeneous catalysts Isotherms of chemisorptions Rate of adsorption: Elovich equation Chemisorption state Chemisorption states of hydrogen Adsorption states of nitrogen Infrared spectroscopy study of nitrogen adsorption The study of electronic energy spectroscopy for nitrogen adsorption The study of adsorption of N2 on non-iron metals Mechanism of Catalytic Ammonia Synthesis Reaction Elementary reactions Catalytic reaction mechanisms for ammonia synthesis The mechanisms of ammonia synthesis reaction The mechanisms of ammonia decomposition Isotope exchanges of N2 Ill Distinguishing reaction mechanisms Analysis of microreaction (intrinsic) kinetics of ammonia synthesis Analysis of reactor The conclusion of microkinetic analysis Kinetics of Overall Reactions for Ammonia Synthesis General relation between overall reaction and elementary steps Two-step sequences Fundamental hypothesis of Temkin theory The reaction rate equation of Temkin-Pyzhev for ammonia synthesis 137

4 Contents xv Consequence of Temkin's theory and search for best catalysts The riddling search for the optimal active site or the best catalyst Difference of catalytic activity on different active site (or catalyst) Interpretation of very large differences in catalytic activity Structure-sensitivity of ammonia synthesis reaction Apparent Reaction Kinetics External diffusion Internal diffusion Utilization ratio of internal surface Macrokinetic equation of catalytic reactions Design of Ammonia Synthesis Reactor Applied form of kinetic equation Mathematic model for design of reactor Distribution between various beds of multi-beds adiabatic reactors for ammonia synthesis Fundamental data for design of ammonia synthesis reactor An example of simulating design calculation 176 References 177 Chapter 3. Chemical Composition and Structure of Fused Iron Catalysts Iron Oxides Fe Fe FeO Oxidative Non-stoichiometry Metastability-disproportionating reactions Relationship between various iron oxides Complex oxides and their solid solution of irons Compound-type complex oxides Sosoloid-type complex oxides Defect structures of iron oxides Classification of defects Intrinsic defects and impurity defects Irregularity of lattice and heterogeneous catalysis Iron Oxides and Catalytic Activity Classical volcano-type activity Hump-type activity curve 214 curve Monophasical principle 219

5 xvi Ammonia Synthesis Catalysts: Innovation and Practice Activity pattern of reduced catalyst with iron oxides as precursor Iron oxides and reduction performance of catalysts Iron oxides and the surface textures of catalysts Iron oxides and the adsorption properties on catalyst Promoters of Fused Iron Catalyst Design of promoter Structural promoters Electronic promoters Enrichment phenomena of promoters partial to surface of catalysts Distribution of promoters in unreduced catalysts Structures of Unreduced Catalysts Structural images of the classical fused iron catalysts Structural images of Fei _xo based fused iron catalysts Structure of Activated Iron Catalyst Pore structures Surface structure of activated iron catalyst The role of surface restructuring Nanometer effect Single-crystal structure of a-fe and the active sites About Fei_xO Based Catalysts and Their Highly Active Mechanism 300 References 304 Chapter 4. Preparation of Fused Iron Catalysts Technology and Equipments for the Preparation of Fused Iron Catalysts Purification of raw materials Proportion and mixing of materials Melting of materials Discharging and cooling of molten material Crushing and sieving of molten materials Packing, storage and transportation Chemical Reaction During Preparation Process Phase Transformation and Phase Diagram Analysis During Preparation Segregation of Promoters During Solidification Processes Preparation of Prereduced Catalysts Preparation Technique of Spherical Catalysts Shaping technique of catalysts Preparation technique of spherical catalysts for ammonia synthesis Methods of mechanical impact dispersion and liquid spurt impact dispersion Continuous glomeration method Spraying glomeration method 351

6 Contents xvii 4.7 Recycling of Waste Catalyst for Ammonia Synthesis 354 References 356 Chapter 5. Reduction of Fused Iron Catalysts Solid-State Reactions Involved in Reduction Process General laws of solid state reaction Solid state reaction kinetics Kinetic model of solid state reaction Kinetic model for gas-solid non-catalytic reaction Kinetic model for reduction of fused iron catalyst Crystal nucleus growing model Reduction Process of Oxides Reduction Thermodynamics for Iron Oxides Reduction Reaction Kinetics of Iron Oxides Reduction mechanism of oxides Reduction of single particle catalyst The relation between activity and physical properties with the reduction degree Factors of Influence on Reduction Rate Influence of temperature Influence of pressure Influence of space velocity Influence of gas composition Influence of oxide precursor Influence of promoters to reduction rate Reduction in Industrial Equipments Reduction rate of catalyst in industrial reactor Characteristic of reduction processes in catalyst bed Characteristic of reduction processes by pure H2 in catalyst bed Characteristic of reduction processes by syngas in catalyst bed The choice of reduction condition in industrial reactor The reduction program in the industrial converter 421 References 422 Chapter 6. Ruthenium Based Ammonia Synthesis Catalysts Chemical Compositions of Ruthenium Catalysts Ruthenium precursor compound Supports of ruthenium catalysts Activated carbons Oxides Molecular sieve Other supports The promoter of ruthenium catalyst Mechanism on the role of support and promoter Hydrogenolysis of precursor of promoter Electronic contribution of active site 447

7 xh20 xviii Ammonia Synthesis Catalysts: Innovation and Practice 6.2 Preparation of Ruthenium Catalyst Outline Pretreatment of supports Graphitization of activated carbons Acid treatment The treatment in H2 or inert atmosphere Microwave treatment Impregnation Impregnation methods The influencing factors during impregnation Reduction of RUCI3 and elimination of chlorine ions The effect of chlorines on catalytic performances The elimination of chlorines in catalyst Discussion on mechanism of chlorine poison on Ru catalyst Drying Performance Characteristic of Ruthenium Catalysts Structural sensitivity The activity of ruthenium catalyst The strong inhibition of H The phenomenon of strong H2 inhibition The possible reasons of hydrogen inhibition Measures to reduce hydrogen inhibition Methanation reaction of activated carbon The stability of ruthenium catalyst The effect of graphitization on methanation Influence of physical and chemical property of activated carbon on methanation The effect of compositions of catalyst on the methanation Thermodynamics and mechanism of methanation reaction of carbon 534 References 537 Chapter 7. Performance Evaluation and Characterization of Catalysts Performance Evaluation of Catalysts Basic concepts Activity Selectivity Stability Performance evaluation of catalysts The reactor for performance evaluation and dynamic test of catalyst Experimental device Evaluation of catalytic activity Measurement of Physical Properties of Catalysts Particle size and density 562

8 Contents xix Particle size and particle shape factor (</js) Density of catalyst Voidage of catalyst bed (e) Surface area and pore structure Specific surface area Pore volume Porosity Average pore size Twist-factor Distribution of pore size Lag-ring and pore structural model Nature and Structure of Surface Introduction Intensity and quantity of chemisorption Adsorbed state of gas on surface of catalysts Chemisorption stoichiometry Physical and chemical adsorption experiment on iron catalyst Measuring the number of total surface metal atoms by chemisorption Measuring surface area and acid-base of various component by chemisorption Measurement of exposed fraction of surface metal atoms Measurement of metal particle nanosize on the surface of catalyst Turnover frequency and active site Chemisorption: measure the rate and activation energy of adsorption Temperature Programmed Analysis Technology (TPAT) Temperature programmed desorption (TPD) Temperature programmed reduction (TPR) TPR dynamic equation Impact factors of TPR dynamic equation Measurement dispersion of metal catalyst by TPR Temperature programmed oxidation (TPO) Temperature programmed sulfuration (TPS) Temperature programmed surface reaction (TPSR) Application of Thermal Analysis Technology in Catalyst Research Derivatography analysis (DTA) and its application Thermogravimetric analysis (TGA) and its application Characterization of the Microstructure and Properties of Catalysts Application of XRD in the study of catalysis Quantitative analysis of phase composition Determination of lattice constant Determination of average nanoparticle size by line width method 615

9 XX Ammonia Synthesis Catalysts: Innovation and Practice Extended X-ray absorption fine structure (EXAFS) analysis Multicrystalline structure determination Structure analysis by Rietveld fitting Application of XRD in the research of ammonia synthesis catalysts Structure of precursor and active phase of Fe304-based ammonia catalyst Grain-growth kinetics and microstructure evolution of nanocrystalline iron Application of other modern physical methods in catalyst characterization 639 References 643 Chapter 8. Performance and Application of Catalysts Activity of catalysts Reaction pressure Reaction temperature Active temperature of catalyst The optimum reaction temperature Realization of the optimum reaction temperature curve Control of temperature of catalyst beds Space velocity Gas compositions H2/N2 ratio Content of inert gas Content of ammonia in the inlet gas and temperature of ammonia refrigeration Particle Size of Catalysts Effect of particle size on catalytic activity and reaction rate of catalyst Effect of particle size on the utilization ratio of inner surface of catalyst Effect of particle size on the pressure drop of catalyst bed Choice of catalyst particle size for industrial applications Poison and Life of Catalyst Thermal sintering and changes of chemical composition of catalyst Poisons and the phenomenon of poisoning of catalyst Types of catalyst poisoning Poisons of catalyst Factors affecting toxicity Poisons and the poisoning phenomena for ammonia synthesis catalysts Mechanical Strength of Catalysts 705

10 Contents xxi Theoretical research on the mechanical strength for the solid catalyst The basis of catalyst solid mechanics The measurement of mechanical strength for solid catalyst Effect of chemical composition of catalysts on its mechanical strength The requirement of mechanical strength of catalysts in industry Usage and Maintenance of Ammonia Synthesis Catalysts Selection of the type of catalyst to use Type of catalysts for ammonia synthesis Pre-reduced catalysts Spherical catalysts for ammonia synthesis Proper use of catalysts The transport and storage of catalysts 728 References 728 Chapter 9. Effect of Catalyst Performance on the Economic Benefits of Catalytic Process Synthesis Processes and Catalysts Process with classical molten iron catalysts Kellogg process Tops0e process Braun process ICI-AMV process with Fe-Co catalyst Synthetic process flow with Ru catalysts The synthesis process with low ratio of H2 to N Synthetic process flow without circulation Process flow of using Fe catalyst combined with Ru catalyst Pressure of reaction and isopiestic process Pressure of reaction Process of synthesis at isotonic pressure The low-pressure renovation for the small-medium ammonia plant Ammonia Converter and Catalysts Performance of Catalyst and Recovery of Reaction Heat The theoretic energy consumption of synthesis ammonia The actual energy consumption of the ammonia production Catalyst activities and the use of the reaction heat Influence of Performance of Catalyst on the Economic Benefits of Catalytic Process Catalyst-consumed cost Economic factor of reduction for catalyst 774

11 xxii Ammonia Synthesis Catalysts: Innovation and Practice The economic benefits using the pre-reduced catalyst Effect of catalyst performance on the economic benefits of process Selectivity of catalyst Life period and service time of ammonia catalyst Economic appraisement of the service time of the catalyst Economic appraisement on replacement of catalyst Benefits of Operating Rate and Management of Enterprise 789 References 790 Chapter 10. Innovation and Speculation New Exploration of Ammonia Synthesis Catalyst Revelation of theory and practice of fusing-iron catalyst Exploration of non-iron and alloy catalysts Exploration of other non-iron catalyst for ammonia synthesis Non-crystal catalyst New Catalytic Technique for Ammonia Synthesis Progress in ammonia synthesis at normal pressure and temperature Photocatalysis for ammonia synthesis Photocatalytic reaction and photocatalyst Photocatalytic ammonia synthesis by water and dinitrogen Electrocatalytic ammonia synthesis at normal pressure Electrocatalytic reaction and electrocatalyst The progress of electrochemical ammonia synthesis Biocatalytic ammonia synthesis at normal temperature Ammonia synthesis at supercritical condition New Application of Ammonia Ammonia synthesis device is a highly efficient device for energy transformation and hydrogen production New application of ammonia 841 References 846 Index 851