Catalytic Reactor Design Catalysts: Applications: Oil & Gas, Petrochemicals, Enviroment, Energy, Fine Chemicals Definintion Types: Bio (enzymes), Homogeneous, Heterogeneous Multi Disciplinary: Physics & Chemistry (Surface Scienece & Organometallics), Enzymology Chemical Engineering, Materials Science Properties of Heterogeneous Catalysts Synthesis & Characterization of Heterogeneous Catalysts Catalysis Mechanism: Chemisorption, Surface reactions, RDS, LH, ... Kinetics Fogler Ch10 Deactivation of Catalysts (Ch. 10) External and Internal Mass-Transfer Resistances and Overall Rates (Ch. 11 & 12) Reactor Design of Fixed Bed Reactors, Moving and Fluidized Beds, Multi-Phase, … A. A. Khodadadi, Catalysis & Nanostructured Materials Research Lab. Industrial Heterogeneous Catalysis; Examples Reaction Catalyst Reactor CH4 + H2O = CO + H2 Steam Reforming Ni-Al2O3 + CaO Multitube, FB Vegetable oil hydrogenation Raney Ni or Ni/Al2O3 slurry N2+ 3H2 = 2NH3 160 MT/y Fertilizer, HNO3 Fe-Al2O3 - CaO ad. FB C2H2 = C2H4 selective Hyd. Pd/Al2O3 ad. FB SO2 + ½ O2 = SO3 V2O5/SiO2 + K2SO4 ad. FB NH3 + CH4 + air = HCN in methyl methacrylate 90% Pt – 10% Rh Wire Gauze C3H6 + NH3 +3/2O2 = CH2-CHCN + 3H2O Bismuth phosphomolybdate on silica Fluidiz. bed Catalytic Cracking on Solid Acids RE-US-Y, ASA, Kaolin, … Fluidiz. beds Hydrocracking – Hydrotreating (S & N Removal) Ni/Co-Mo/W -Alumina ad. FB Catalytic Reforming ON↑ Pt-Re/ Cl-Alumina ad. FB GTL: CO+ H2 = CH3OH, Liq. Fuels, … Cu-ZnO, Fe/Co/Al2O3 FB, slurry NOx SCR VOx/TiO2 Oxidation Acrylonitrile گاز دنيا%18-16 : روشهای تبديل گاز طبيعي C2 H 6 ODH C2H4 گاز طبيعي CH عمدتا CH3OH C3H6, C4H8 MTG 4 CO + H2 Syngas-derived chemicals DME WGS: CO+H2O CO2 + H2 + ~1% CO + H2 CH4 سوخت مايع پيل سوختی Cathode catalytic reaction: Anode catalytic reaction: O2 + 4H+ + 4e- 2H2O H+ 2H2 4H+ + 4e- Overall reaction: 2H2 + O2 2H2O + Heat https://www.youtube.com/watch?v= Fl3aD1qJrEg 100 HC Fuel CO stoic NOx 0 ECU 14.3 14.9 14.6 A/F ratio 120,000,000/y Exhaust Catalyst Engine Oxygen sensor Air Accelerator Pt/Pd/Rh Alumina-ceria washcoat Atomotive Emission Control Three-way catalyst: Pt/Pd/Rh on Al2O3-CeO2 Pt/Pd: CO + 1/2 O2 CO2 Pt/Pd: HC + O2 CO2 + H2O Rh: NOx + CO/HC N2 + CO2 + H2O نانو لوله های كربنCarbon NanoTubes By Chemical Vapor Deposition (CVD) of CO, CH4, C2H2, xylene … On Catalyst: Nano-Ni/Co/Fe-Mo/SiO2-Al2O3 1-5 atm 700-900oC Bulk CNTs: for e.g. adsorbents, hydrogen storage, nanocomposites, sensors, electronic... Examples of Challenges Catalytic Solutions Environmental Pulltion Catalysis Stable CO2 Utilization fuels/chemicals: Photo/Electro-Catalysis BioMass Catalytic Pyrolysis-Deoxygenation/Gassification Fuel PhotoCatalytic Watetr Splitting Hydrogen for Fuel Cells …., …, …, … DeOxygenation Catalyst size and shape for fixed-bed reactors DP↑ : U↑, dp↓ Diffusion, M-T and Overall Reaction Rates↑ U↑, dp↓ (hollow) pellet, (lobed) extrudate, spherical, … CA Strength: (Hollow) Pellet … Selectivity: Wire gauze Catalysts for fluidized bed reactors 50-100 mm spherical particles High attrition resistance Monolith Catalysts & Microreactors Catalyst Definition Catalyst is a substance that increases the rate at which a chemical reaction approaches equilibrium without itself becoming permanently involved in the reaction Substance: not light, not plasma, not electric or magnetic field but photo/Bio(electro)catalyst Catalyst increases the rate of a reaction: via a new path with lower activation energy Catalyst increases the rate of a reaction via a new path with lower activation energy k A Ae Arrhenius Eqn : Ea RT Why Ea of catalytic reaction is lower? Example: H2+0.5O2 H2O --------------------1,000,000 years in 1 s! ---- DH= - 285 kJ/mol DGo = -237 kJ/mol at 25oC: K=e237000/(8.314x298)=3.5x1049 Thermodynamically highly favorable But negligible rate, unless initiated by catalyst (e.g. Pt) or spark For reaction, H2 and/or O2 bonds (435 & 490 kJ/mol) must break No change in equilibrium e.g : A Catalyst C B D C A0 (1 x) C A0 (1 x) Catalyst C A0 x C A0 x DG x2 K e (1 x) 2 0 RT K1 DH 0 1 1 Ln ( ) K2 R T1 T2 DG 0 10 ?! DH0 < 0 K decreases with T N2+3H2 2NH3 Catalyst Types Homogeneous E.g.: Oxo (propylene hydrofomylation) process on cobalt complex in liquid 10-100 atm, 40-200oC Carbonyl Ligand Catalyst Temp. Limit Catalyst Separation Hydrolysis of esters by acid catalysis - all reactants and catalyst are dissolved in water. CH3CO2CH3(aq) + H2O(l) ↔ CH3CO2H(aq) + CH3OH(aq) - with H+ catalyst. Enzyme (Bio) catalyst in vinegar, cheese, & bread; 2000 years ago Heterogeneous Catalysis ------, Photo-, Electro-, Heterogenized homogeneous & enzymatic Fluid? reactants & Products / Solid catalyst: No or easy separation, High T Chemicals = ~7% GDP; 1/3 Materials GNP >85% of (Petro)Chemicals through catalytic reactions in Oil & Petrochemicals, in Environment Reforming, (Hydro) Cracking, Hydro-treatment, ... Alkylation, isomerization, oxidation, hydrogenation, … Gasoline & Diesel oil, Fertilizer, polymer, … methanol, sulfuric acid, ... • 85% of processes in the chemical industry use catalysts. • Catalyst sales in 2010 were worth 15 billion dollars. • Turnover in industries using catalysts was about 5,700 Billion dollars. • Growth in catalyst sales: 5% - 10% per year. • The conversion of oil or natural gas to anything uses a catalyst. Heterogeneous Catalyst Properties: Specific Surface Area 8.1 nm Catalytic reaction occurs on solid surface –r’A=Sa (-r”A, ~Const. for specific catalyst materials?) Increase surface/g = Specific Surface Area (SSA) 1 cm pellet 10 nm 106 times increase in surface area Porous catalyst A 4r 2 6000 m 2 Sa 3 V (4 3 r ) d g TEM of Automotive catalyst Alumina : s 3.7 g mL <5 nm Pt crystals d p 3 mm 3 106 nm, p 1.9 on ~10 nm Al2O3 ac 1.1 103 m 2 g Supported catalyst Pt-Re/Al2O3, V2O5/SiO2 300 3 mm m2/g, Pd/C, up to 1000 m2/g Raney Ni non-porous, e.g. Pt & Ag Gauze; in methanol & C2H4 oxidation S a 200 m 2 g d 8.1 nm S a ac 200 1.1 103 180000 How to prepare high SSA catalyst Sol-Gel/Percipitation X=H or R Hydrolysis: –M-OR + H2O → -M-OH + ROH, Condensation: -M-OR + -M-OX→-M-O-M + X-OH, High superSaturation Large # of nuclei, Limited growth Small nanoparticles, High SSA Ostwald ripening, Gelation, Drying (Capillary P), Calcination, … Nucleation burst: sudden addition of reducing/precipitating agents TiO2 nanoparticles synthesis in W/O microemulsions = NanoReactors W/O microemulsion Nano-Reactors 20-30 surfactants Small (5-50 nm) water droplets in continuous oil phase. W/O microemulsion + Ti(OC3H7)4 : H2O : Surfactant Nucleation & growth : Ti(OC3H7)4 : TiO2 Vent Aggregation Mesoporous materials Mixing aluminosilicate precursors (e.g. sodium aluminate, tetramethyl ammonium silicate) in a surfactant solution (e.g. ≥ 1 wt% cetyltrimethyl ammonium bromide (CTAB)) Impregnation of soluble precursor solution onto available support e.g. alumina or silica, e.g. Ni/Al2O3 for steam reforming HZSM5 Zeolite Y: 0.74 nm Zeolites: Molecular sieves By hydrothermal method Chemical Vapor Deposition (CVD) Carbonyls: Fe(CO)5, Ni(CO)4, … Halides: TiCl4 Acetates: Cu(CH3COO) Alkoxides: Ti(OC2H5)4, Si(OC2H5)4 … Alkyl Comp: Al(C2H5)3, …. Parameters: Surface reactionmass-transfer control Temperature: rate Decomposition, Hydrolysis, Oxidation, Reduction … Pressure: rate & uniformity Porous support catalyst? ALD