A Multiphase Microreactor for A Multiphase Microreactor for Organic Nitration Organic Nitration Dr. John R.Burns Dr. John R.Burns Dept. Chemical & Process Engineering, Dept. Chemical & Process Engineering, University of Newcastle, University of Newcastle, U.K. U.K.
Intensifying Multiphase Reactions Intensifying Multiphase Reactions Using Narrow Channel Flow Using Narrow Channel Flow Key Points Key Points • Geometry Scaled to Produce Short Diffusion Path Lengths Geometry Scaled to Produce Short Diffusion Path Lengths • • Residence Time Determined by Length/Velocity Residence Time Determined by Length/Velocity •
Diffusion between streams Diffusion in/out of droplets PARALLEL DROPLET FLOW EMULSION Diffusion across Internal convective Typical Methods Typical Methods the interface transport for Contacting for Contacting Two Fluid Phases Two Fluid Phases Fluid 1 Fluid 1 Channel Scale Channel Scale µ µ m - 500 µ µ m 50 µ µ µ µ m - 500 µ µ µ µ µ µ µ µ Fluid 2 Fluid 2 SLUG FLOW m 50
Benefits of Slug Flow Benefits of Slug Flow Easy Post-Reaction Separation : Slugs are large enough • Easy Post-Reaction Separation : Slugs are large enough • µ m scale) to (>100 µ m scale) to be separated by gravity. No emulsions. be separated by gravity. No emulsions. (>100 Convective Mixing : Rapid internal circulation reduces • Convective Mixing : Rapid internal circulation reduces • effective diffusion path lengths to less than that for parallel effective diffusion path lengths to less than that for parallel flow. flow. • Effective at Larger Scales Effective at Larger Scales : Can be used in larger : Can be used in larger • channels than would be effective for parallel flow. channels than would be effective for parallel flow.
Transport Processes in Slug Flow Transport Processes in Slug Flow Aqueous Slug Organic Slug Diffusion Convection
Method of Slug Flow Generation Method of Slug Flow Generation Example in a Glass Device Example in a Glass Device Input 1 Input 1 Static Static (no input) (no input) Input 2 Input 2 Output Output Organic Phase Dyed Blue Organic Phase Dyed Blue Aqueous Phase Transparent Aqueous Phase Transparent
Examples of Slug Flow in a Perspex Chip Examples of Slug Flow in a Perspex Chip High Viscosity : 3.2mm/s High Viscosity : 9.6mm/s High Viscosity : 3.2mm/s High Viscosity : 9.6mm/s Low Viscosity : 3.2mm/s Low Viscosity : 29mm/s Low Viscosity : 3.2mm/s Low Viscosity : 29mm/s
EXPERIMENTAL WORK EXPERIMENTAL WORK Aqueous/Organic Titration Aqueous/Organic Titration Using Slug Flow Using Slug Flow A Model Reaction to Examine A Model Reaction to Examine Mass Transfer in Slug Flow Mass Transfer in Slug Flow
Titration Process - Acid Extraction Titration Process - Acid Extraction Liquid-Liquid Reaction Specifications Liquid-Liquid Reaction Specifications Organic Phase (ACID) Organic Phase (ACID) Kerosene + Acetic Acid (0.50 to 0.65 mole/litre) Kerosene + Acetic Acid (0.50 to 0.65 mole/litre) Sudan III (red dye) Sudan III (red dye) insoluble in this phase Base insoluble in this phase Base Aqueous Phase (BASE) Aqueous Phase (BASE) Water + NaOH NaOH / KOH (0.10 to 0.40 mole/litre) / KOH (0.10 to 0.40 mole/litre) Water + Phenol Red (pH indicator) Phenol Red (pH indicator) completely soluble in this phase Acid completely soluble in this phase Acid
Experimental Facility - Glass Reactor Experimental Facility - Glass Reactor Channel 0.38mm wide, 0.38mm deep 70 mm Drilled Holes 1.6mm Experiment Aqueous Organic - Acetic Aqueous/Organic (mole.litre -1 ) (mole.litre -1 ) mole ratio KOH (a) 0.25 (KOH) 0.50 0.50 NaOH (a) 0.25 (NaOH) 0.65 0.42 NaOH (b) 0.40 (NaOH) 0.65 0.62 NaOH (c) 0.10 (NaOH) 0.65 0.15 Experimental Conditions Examined Experimental Conditions Examined µ m Reactor Channel Width of 380 µ m Reactor Channel Width of 380
Photographs of Slug Flow Titration Photographs of Slug Flow Titration Inside the Glass Reactor Inside the Glass Reactor 1.9mm Aqueous Slugs (Pink) Generated at 2.8mm/s 1.9mm Aqueous Slugs (Pink) Generated at 2.8mm/s Organic Organic Direction of Flow Direction of Flow Phase Phase Aqueous Aqueous Phase Phase Completed Reaction 10mm Downstream (3.6s Later) Completed Reaction 10mm Downstream (3.6s Later) (Yellow colour indicates base neutralised) (Yellow colour indicates base neutralised) Glass Device - 0.38mm wide/deep channels Glass Device - 0.38mm wide/deep channels
Analysis of Titration in Glass Device Analysis of Titration in Glass Device 4.0 Average Slug Length (mm) System 3.5 3.0 KOH (a) 2.5 NaOH (a) NaOH (b) 2.0 NaOH (c) 1.5 1.0 0.5 0 10 20 30 40 Flow Speed (mm/s) Average Length of Aqueous Slug Produced Average Length of Aqueous Slug Produced
Analysis of Titration in Glass Device Analysis of Titration in Glass Device 9 System 8 Colour Change Time (s) 7 KOH (a) 6 NaOH (a) 5 4 NaOH (b) 3 NaOH (c) 2 1 0 0 10 20 30 40 Flow Speed (mm/s) Time Requirements for Complete Colour Change Time Requirements for Complete Colour Change Neutralisation of Base by Acetic Acid ) (That is : Neutralisation of Base by Acetic Acid ) (That is :
Analysis of Titration in Glass Device Analysis of Titration in Glass Device 12 10 Model Prediction (s) 8 v = velocity 6 L = slug length 4 α = transfer proportion 2 t = time 0 0 2 4 6 8 10 12 Measured Transfer Time (s) -0.19 0 . 94 v L = α 0 . 67 t 4 . 67 . . seconds v L 0 0 Empirical Correlation for Transfer Time Empirical Correlation for Transfer Time
Simulation of Slug Flow Titration Simulation of Slug Flow Titration Simulation of 1.2mm Slugs in a 0.4mm Channel Simulation of 1.2mm Slugs in a 0.4mm Channel Results for 93% Base Neutralisation for 2:1 Acid:Base Results for 93% Base Neutralisation for 2:1 Acid:Base 0.25 mm/s (at 28s) 0.5 mm/s (at 22s) 0.25 mm/s (at 28s) 0.5 mm/s (at 22s) 2 mm/s (at 14s) 4 mm/s (at 11s) 2 mm/s (at 14s) 4 mm/s (at 11s) Base Slug Acid Slug Base Slug Acid Slug Acid Concentration (mole %) Acid Concentration (mole %)
Titration of Slug Flow in Perspex Titration of Slug Flow in Perspex Pattern of Neutralisation in Aqueous Slug Pattern of Neutralisation in Aqueous Slug Acid Slug Perspex Chip with 0.76mm Channel Perspex Chip with 0.76mm Channel Base Acid Zone zone Average Flow Velocity of 8.4mm/s Average Flow Velocity of 8.4mm/s Pink = pH > 7 Yellow = pH < 7 Pink = pH > 7 Yellow = pH < 7
Comparison of Experimental and Comparison of Experimental and Simulation Models Simulation Models Simulation Prediction Simulation Prediction ∝ -0.3 0.8 Reaction Time v . L . w Experimental Results Experimental Results ∝ -0.19 0.94 ? Reaction Time v . L . w v = velocity, L = slug length, w = channel width v = velocity, L = slug length, w = channel width
EXPERIMENTAL WORK EXPERIMENTAL WORK Organic Nitration Organic Nitration Using Slug Flow in Capillary Tubing Using Slug Flow in Capillary Tubing A Practical Test of a Slug Flow A Practical Test of a Slug Flow for Chemical Production for Chemical Production
Experimental Facility for Nitration Experimental Facility for Nitration Reactor Capillary Liquids Cooled and Diluted on Exit Liquids Cooled and Diluted on Exit Tube Modified Tee Narrow Gap to Allow The capillary tube The capillary tube Liquid Flow was heated to was heated to provide the reactor provide the reactor temperature temperature Capillary Tube 1 Capillary Tube 2 Organic Input Acid Input Slug Flow Pattern Produced in a PTFE Capillary Slug Flow Pattern Produced in a PTFE Capillary
Mixed Acid Nitration Process Mixed Acid Nitration Process Liquid-Liquid Reaction Specifications Liquid-Liquid Reaction Specifications Organic Phases : Organic Phases : Benzene & Toluene Benzene & Toluene Acid Phase : Acid Phase : H 2 SO 4 + HNO 3 + H 2 O H 2 SO 4 + HNO 3 + H 2 O Process Specifications Process Specifications Benzene Nitration : Stainless Steel Capillary Benzene Nitration : Stainless Steel Capillary 10:1 Acid:Organic Flow Ratio 10:1 Acid:Organic Flow Ratio Syringe Driver Pumping Syringe Driver Pumping µ m Bore) PTFE Capillary (150 µ Toluene Nitration : PTFE Capillary (150 Toluene Nitration : m Bore) Varied Acid:Organic Flow Ratios Varied Acid:Organic Flow Ratios HPLC Pumps HPLC Pumps
Benzene Nitration : Influence of Diameter Benzene Nitration : Influence of Diameter 25 Initial Nitric Reaction Rate (min -1 ) 0.127 mm 20 0.254 mm 83% H 2 SO 4 , 2.2% HNO 3 15 (mass concentration) 10 5 15cm/s Flow 0 55 60 65 70 75 80 85 90 95 Temperature ( o C) Smaller Tube = Better Performance Smaller Tube = Better Performance
Benzene Nitration : Influence of Flow Velocity Benzene Nitration : Influence of Flow Velocity 100 Initial Nitric Reaction Rate (min -1 ) Flow Velocity 18.5 cm/s 7.7 cm/s 10 2.0 cm/s Mass Transfer Limited 1 Kinetic Limited 0.1 65 70 75 80 85 90 H 2 SO 4 Concentration (mass %) ° C Capillary Diameter 178 µ m Temperature 90 ° C Capillary Diameter 178 µ m Temperature 90 HNO 3 Mass Concentration of 4% HNO 3 Mass Concentration of 4%
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