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ChE 512Transport Effects in Chemical Reactors
PART 2Module 1
Introduction to Heterogeneous Reactors and Application Areas
P.A. [email protected]
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Topical Outline
• Introduction• Kinetic models• Transport effects• Gas-solid reactions• Gas-liquid reactions• Three Phase Reactors• Biochemical reactors• Electrochemical reactors
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Course ObjectivesCourse Objectives• Review basic multiphase reaction engineering
reactor types and applications in petroleum processing, fine chemicals, and specialty chemicals.
• Develop basic relationships that describe thecoupling between transport effects and kineticsfor multiphase systems on a local level.
• Derive the basic performance equations for integralreactor performance using ideal flow patterns forthe various phases.
• Present case studies or examples where the theoryis put into practise.
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Module 1 Outline
• Industrial Applications and Examples• Review of Common Reactor Types• Guidelines for Reactor Selection
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Starting ReferencesStarting References1. Doraiswamy L.K. and Sharma. M. M. Heterogenous
Reactions,2. P. A. Ramachandran and R. V. Chaudhari,
Three-Phase Catalytic Reactors, Gordon & Breach,London (1983).
3. P. L. Mills, P. A. Ramachandran, and R. V. Chaudhari,Reviews in Chemical Engineering, 8, pp. 1-192 (1992).
4. P. L. Mills and R. V. Chaudhari, “Multiphase catalyticreactor engineering and design for pharmaceuticals and fine chemicals,” Catalysis Today, 37(4), pp. 367-404 (1997).
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Multiphase Catalytic ReactionsMultiphase Catalytic Reactions
Reactants ProductsCatalyst
Δ
• Gases
• Liquids
• Solids
• Solvent
• Gases
• Liquids
• Solids
• Solvent
Homogeneous
Heterogeneous
EnzymeBacteria
Cells
Present
Future
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Classification Based on Number of Phases
• Gas-Solid Catalytic• Gas-Solid Non-Catalytic• Gas-Liquid• Gas-Liquid Solid Catalytic• Gas-Liquid with Solid Reacting• Liquid-Liquid• Gas-Liquid-Liquid-Solid
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Some Examples of Some Examples of Multiphase Catalytic ProcessesMultiphase Catalytic Processes
• Hydrogenation of specialty chemicals• Oxidation of glucose to gluconic acid• Oxidation of n-paraffins to alcohols• Methanol synthesis• Fischer-Tropsch (FT) synthesis• Hydrodesulfurization (HDS) of heavy
residuals• Adiponitrile synthesis• Production of animal cells• Fermentation processes
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Other EmergingOther EmergingMultiphase Catalytic TechnologiesMultiphase Catalytic Technologies
• Catalysis by water soluble metal complexes in biphasic and nonionic liquid media
• Reactions in supercritical fluid media
• Asymmetric catalysis for chiral drugs/agrichemicals
• Polymerization with precipitating products(e.g., Polyketones)
• Phase transfer catalysis
• Catalysis by adhesion of metal particles to liquid-liquid interfaces
• Catalysis by nano-particles and encapsulation of metal complexes
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Multiphase Reactor Technology AreasMultiphase Reactor Technology AreasPetroleum
Refining
PolymerManufacture
EnvironmentalRemediation
Syngas & Natural Gas Conversion
BulkChemicals
Fine Chemicals& Pharmaceuticals
HDS, HDN, HDM,Dewaxing, Fuels, Aromatics, Olefins, ...
MeOH, DME, MTBE,Paraffins, Olefins,Higher alcohols, ….
Aldehydes, Alcohols,Amines, Acids, Esters,LAB’s, Inorg Acids, ...
Ag Chem, Dyes, Fragrances, Flavors, Nutraceuticals,...
Polycarbonates,PPO, Polyolefins,Specialty plastics
De-NOx, De-SOx,HCFC’s, DPA,“Green” Processes ..
P. L. MillsNASCRE 1,
Houston, Jan 2001
Value of Shipmentsin $US billions
http://www.eia.doe.gov/
350
150
450
250
1987 1989 1995 19971991 1993
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The Global Chemical Industry
CR&D Chemical Sciences & EngineeringP. L. Mills
CS&E
• Generates > $2 trillion gross income- 70,000 products- 1000 corporations (many small ones)
• Largest contributor to GDP
• Distribution:European Union
35%
USA27%
Asia15%
Japan13%
Balance10%
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Multiphase Catalytic ReactionsMultiphase Catalytic Reactions-- Business Drivers Business Drivers --
• Increased globalization of markets
• Societal demands for higher environmental performance
• Financial market demands for increased profitabiltyand capital productivity
• Higher customer expectations
• Changing work force requirements
Technology Vision 2020, The US Chemical Industry, Dec. 1996http://www.eere.energy.gov/industry/chemicals/pdfs/chem_vision.pdf
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Cost Breakdown for Chemical ProductionCost Breakdown for Chemical Production
• For large-scale processes, research must focus on reducing cost of raw materials and/or capital
• Small-scale processes can benefit from almost any improvement
0
10
20
30
40
50
60
70Small Scale Product
Large Scale Product
< 10 MM lb/yr
*
*
Adapted from Keller & Bryan, CEP, January (2000)
> 100 MM lb/yr
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Process Development MethodologyProcess Development Methodology
Lerou & Ng, CES, 51(10) (1996)
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Oxidation of Oxidation of pp--XyleneXylene to Terephthalic Acidto Terephthalic Acid
• G-L (homogeneous) catalytic oxidation with precipitating solid product.• Oxygen mass transfer limitation, starvation of oxygen (due to safety limits) and
exothermicity are key issues in reactor performance• Undesired impurity 4-CBA in ppm level requires a separate hydrogenation step
(g-l-s reaction) to purify TPA• Involves dissolution of impurities, hydrogenation and re-crystallization to
achieve purified TPA• Selection of suitable multiphase reactors has been a major challenge
CH3
COOH
CH3
CH3
CH3
COOH
CHO
COOH
COOH
COOH
O2
cat I
O2
cat I
O2
cat I
H2
cat IIp-xylene
4-CT
4-CBA
TPA
4-CT
Oxidation:Cat I: Co-Mn-BrTemp.: 190-205°CPO2: 1.5-3.0 MPa
Hydrogenation:Cat II: Pd/supportTemp.: 225-275°C
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Key Multiphase Reactor TypesKey Multiphase Reactor Types
• Mechanically agitated tanks• Multistage agitated columns• Bubble columns• Draft-tube reactors• Loop reactors
Soluble catalysts&
Powdered catalysts
Soluble catalysts&
Tableted catalysts
• Packed columns• Trickle-beds• Packed bubble columns• Ebullated-bed reactors
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Classification of Multiphase Classification of Multiphase GasGas--LiquidLiquid--SolidSolid Catalyzed ReactorsCatalyzed Reactors
1. Slurry ReactorsCatalyst powder is suspended in the liquidphase to form a slurry.
2. Fixed-Bed Reactors
Catalyst pellets are maintained in place asa fixed-bed or packed-bed.
K. Ostergaard, Adv. Chem. Engng., Vol. 7 (1968)
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Modification of the Classification for Modification of the Classification for GasGas--Liquid Liquid SolubleSoluble Catalyst ReactorsCatalyst Reactors
1. Catalyst complex is dissolved in the liquidphase to form a homogeneous phase.
2. Random inert or structured packing, if used,provides interfacial area for gas-liquid contacting.
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Common types of gas-solid reactors
• Packed bed• Fluid bed• Monolith• Riser and Downer
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Multiphase Reactor Types Multiphase Reactor Types at a Glanceat a Glance
Middleton (1992)
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Mechanically Agitated ReactorsMechanically Agitated Reactors--Batch or SemiBatch or Semi--Batch OperationBatch Operation--
(a) Batch (b) Semi - Batch“ Dead - Headed “
Gas
Gas
P
G
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Mechanically Agitated ReactorsMechanically Agitated Reactors-- Continuous Operation Continuous Operation --
G
G
G
LG
L
G
Multistage Agitated Column for theSynthesis of Vitamin “carbol”(Wiedeskehr, 1988)
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Mechanically Agitated ReactorsMechanically Agitated Reactors-- Pros and Cons Pros and Cons --
Pros Cons• Small catalyst particles • Catalyst handling• High effectiveness factor • Catalyst fines carryover• Highly active catalysts • Catalyst loading limitations• Well-mixed liquid • Homogeneous reactions• Catalyst addition • Pressure limitations• Nearly isothermal • Temp. control (hot catalysts)• Straightforward scale-up • Greater power consumption• Process flexibility • Large vapor space
Source: P. L. Mills, R. V. Chaudhari, and P. A. RamachandranReviews in Chemical Engineering (1993).
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The BIAZZI Hydrogenation ReactorThe BIAZZI Hydrogenation Reactor
GG
M
Inefficient cooling
Catalyst deposition in low turbulence area
Sealing problems
Poor mixing and non-homogeneous conditionsin low turbulence area
Inefficient heat andmass transfer
Powerful gas dispersion and recirculation:high mass transfer
No heat transfer limitations
(up to 20 m2/m3)
Negligible fouling
Safer than the conventional reactors
Easy catalyst recycling
Conventional Reactor BIAZZI Reactor
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Multistage Agitated Column for Synthesis Multistage Agitated Column for Synthesis “Carbol”“Carbol”--Pharmaceutical Intermediate Pharmaceutical Intermediate
• Continuous reactor system with a cascade column and multistage agitator ensures good mixing, long mean residence time and narrow residence time distribution
• Gas phase voidage is minimum, hence safer for acetylene handling
• High productivity/smaller volume
Chem. Eng. Sci., 43, 1783, 1988
R
O
+
(i) aq. KOH(ii) NH3, -5oC
R OH(iii) H2SO4α,β-unsaturated
ketoneCarbol
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Bubble Column ReactorsBubble Column Reactorsat a Glanceat a Glance
Tarhan (1983)
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Key Types of Bubble ColumnsKey Types of Bubble Columns
G G G
G G G
L
L L L
L L
(a) Empty (b) Plate (c) PackedSemi - Batch Continuous Semi - Batchor Continuous or Continuous
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Bubble Column Reactors Bubble Column Reactors -- Pros and Cons Pros and Cons --
Pros Cons• Small catalyst particles • Catalyst handling• High effectiveness factor • Catalyst fines carryover• Highly active catalysts • Catalyst loading limitations• Well-mixed liquid • Homogeneous reactions• Nearly isothermal • Selectivity Control• Lower power consumption • No guidelines for internals• High pressure operation • More complex scaleup
Source: P. L. Mills, R. V. Chaudhari, and P. A. RamachandranReviews in Chemical Engineering (1993).
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Draft Tube and Loop ReactorsDraft Tube and Loop Reactors
Internal Circulation
External Circulation
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VenturiVenturi Loop ReactorsLoop Reactors
Cramers et al. (1994)
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O OO OH HO
OO
O
O2 H2O H2
n-C4 Maleic anhydride Maleic acid Tetrahydrofuran
Example: DuPont Butane to THF ProcessExample: DuPont Butane to THF Process
Pilot Plant ReactorPonca City, OK
n-C4 OxidationReactor Maleic acid
Hydrogenation Reactor
Purification Train
Commercial PlantAsturias, Spain
$$$$$$$
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Other Types of Loop ReactorsOther Types of Loop Reactors
Internal External Jet Loop withRecirculation Recirculation External Recirculation
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Jet Loop Recycle ReactorsJet Loop Recycle Reactors
Batch Operation Continuous Operation
• Excellent mass & heat transfer performance
• Uniform catalyst distribution and mixing
• Commercially used in hydrogenation, alkylation, oxidation, amination, carbonylation and bio-catalytic reactions
• Higher Productivity/ Throughput
• Lower Catalyst Consumption
• Safer Operation
• Higher Yields & Selectivity
• Lower Power Consumption
Source : Davy Process Technology
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GasGas--lift and Loop Reactorslift and Loop Reactors-- Pros and Cons Pros and Cons --
Pros Cons• Small catalyst particles • Catalyst handling• High effectiveness factor • Catalyst fines carryover• Highly active catalysts • Catalyst loading limitations• Well-mixed liquid • Homogeneous reactions• Nearly isothermal • Selectivity control• High pressure operation • Possible pressure limitations(Gas-lift reactor) (Loop reactor)
• Process flexibility • Greater power consumption(Loop reactor)
• Modular design • Catalyst attrition
Source: P. L. Mills, R. V. Chaudhari, and P. A. RamachandranReviews in Chemical Engineering (1993).
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FixedFixed--Bed Multiphase ReactorsBed Multiphase Reactors
L L
L
L L
G
G G G
G
L
G
Semi-Batch or Continuous Operation; Inert or Catalytic Solid Packing
(a) Trickle - Bed (b) Trickle - Bed (c) Packed - Bubble FlowCocurrent Countercurrent Cocurrentdownflow flow upflow
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Trickle Bed Reactors Trickle Bed Reactors -- Advantages Advantages --
• Plug flow of gas and liquid• High catalyst / liquid ratio• Stationary catalyst• Minimal catalyst handling problems• Operating mode flexibility• High pressure operation• Heat of reaction used to volatize liquid• Large turndown ratio• Low dissipated power• Lower capital and operating costs
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• Larger particles, low catalyst effectiveness
• Possible poor liquid - solid contacting
• High crushing strength required for small particles
• Potential for reactor runaway
• Long catalyst life required
• Inability to handle dirty feeds
• Potential for liquid maldistribution
• More difficult to scale - up
Trickle Bed Reactors Trickle Bed Reactors -- Disadvantages Disadvantages --
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Packed Bubble Flow ReactorsPacked Bubble Flow Reactors-- Advantages Advantages --
• Complete liquid - solid contacting
• Higher liquid holdup
• Better temperature control
• Less problems with liquid maldisdribution
• Higher heat and mass transfer rates
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Packed Bubble Flow ReactorsPacked Bubble Flow Reactors-- Disadvantages Disadvantages --
• Higher dissipated power than in TBR
• Throughput limited by bed fluidization velocity
• Increased potential for runaway
• Promotion of undesired homogeneous reactions
• Greater pressure drop
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Bioreactor TypesBioreactor Types(After Bailey and Ollis, 1986)
Mechanical agitation External pumping Gas agitation
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Commercial or Planned BioprocessesCommercial or Planned BioprocessesHigh Volume ProductsHigh Volume Products
Product Carbon source Production, t/year
Lactic acid corn syrup, whey permeate, agric. waste 300,000Citric acid molasses, glucose 550,000Amino acids molasses, glucose, corn syrup 250,000lysine, glutamic acid
Ethanol molasses, corn syrup, cellulose, agric. waste 28,000,000a
Single cell protein methane 50,000b
1,3 Propane diol corn syrup NA Penicillin glucose, corn steep liquor 25,000Detergent enzymesc glucose, maltose, starch
a for fuels only (US production 14.5x106 t/year in 1996)b a target of 500,000 t/year is projected for Europe for 2010c yearly product value in excess of 109 US$
Leib, Pereira & Villadsden, NASCRE 1, Houston 2001
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Biological Biological vsvs Chemical SystemsChemical Systems• Tighter control on operating conditions is essential
(e.g., pH, temperature, substrate and product concentrations, dissolved O2 concentration)
• Pathways can be turned on/off by the microorganism through expression of certain enzymes depending on the substrate and operating conditions, leading to a richness of behavior unparalleled in chemical systems.
• The global stoichiometry changes with operating conditions and feed composition; Kinetics and stoichiometry obtained from steady-state (chemostat) data cannot be used reliably over a wide range of conditions unless fundamental models are employed
• Long term adaptations (mutations) may occur in response to environment changes, that can alter completely the product distribution
Leib, Pereira & Villadsden, NASCRE 1, Houston 2001
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Complex Reactor example: Complex Reactor example: parapara--Amino Phenol Amino Phenol by 4by 4--Phase HydrogenationPhase Hydrogenation
• Single step process
• Intermediate phenylhydroxylaminerearranged by interfacial reaction to para-aminophenol
• Selectivity determined by competing hydrogenation in organic phase and & interfacial rearrangement with aqueous acid catalyst
PhNH3+
Aq. PhaseOrg. Phase
Pt/C
Gas phase
PhNO2
PhNHOH
PhNH2
PhNHOH
4-PhNH2(OH)
H+
H+
PhNH2
4-PhNH3+(OH)
H+
H2
H2
H+
PhNH3+
H+
H2
NO2 NHOH
NH2
NH2
OH
H2
Pt/C
Phenyl hydroxylamine
p-Amino phenol
Aniline
R.V. Chaudhari et al., CES, 56, 1299, 2001
An intermediate used in the manufacture of several analgesic and antipyretic drugs, e.g., paracetamol, acetanilide, & phenacetin
P. L. Mills, CAMURE-5, June 2005
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Complex Reactor: Example 2Complex Reactor: Example 2Phenyl Acetic Acid by 3Phenyl Acetic Acid by 3--Phase HydroformylationPhase Hydroformylation
CHO
CHO
ProductsReactant
CO H2
Rh
P
SO3Na
SO3Na
SO3Na
P
NaO 3S
NaO 3S
NaO 3S
PSO3Na
SO3Na
SO3Na
OCH
Rh/TPPTS Catalyst
Gas Phase
Aor Bor Eor Por
Ag Bg
Organic Phase
Aqueous Phase
Aaq Baq Eaq Paq
Gas - Organic Phase Interface
Aqueous-Organic Phase
Interface
Soluble catalyst
Cl CO/H2
Pd-Catalyst
OH
OBenzyl chloride Phenyl acetic acid
Wan & Davis, 1993
GasGas--LiquidLiquid--Liquid w/Soluble CatalystLiquid w/Soluble Catalyst
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Electrochemical Reactors
• Electrolytic production of chlorine and NaOH; Chloralkali industry.
• Aluminum production (Halls process)• Fuel cells• Monsanto adiponitrile process• Paired electrosynthesis• Pollution prevention; Metal recovery
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Strategies for Multiphase Reactor SelectionStrategies for Multiphase Reactor Selection
• Maximize yield• Ease of scale-up• High throughput• Low pressure drop• Lowest Capital cost• Other requirements
ProcessRequirements
Reactor ?Reactants
• Intrinsically safe• “Green” processing• Zero emissions• Sustainable
Desired Products
Undesired Products
Unconverted ReactantsEnvironmentaland Safety
)
“Wish List”
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Summary: Distinguishing Features Summary: Distinguishing Features of Multiphase Reactorsof Multiphase Reactors
• Efficient contacting of reactive phases and separation of product phases is key to safety, operability and performance
• Various flow regimes exist, depending on phase flow rates, phase properties, operating conditions, and geometry
• Reaction and interphase transport time-scales, and phase flow patterns dictate reactor type, geometry and scale
• Gradual scale-up over several scales may be required for reliable commercialization
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ThreeThree--Level Strategy for Reactor SelectionLevel Strategy for Reactor Selection
Level I
Level I
Level II
Level III
Catalyst Design
Reactant& EnergyInjectionStrategies
HydrodynamicFlow Regimes
• Analyze process on three levels• Make decisions on each level
Use fundamentals, data,& basic models for screeningof various reactor alternatives
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Multiphase TransportMultiphase Transport--Kinetic InteractionsKinetic Interactions
)T,C(R )C(L Ib
Ib
IIIb
I η=
∑ −=j
Ib
Ib
Ij
IjR
Ib
Ih )T,C(R )H( )T(L I
jηΔ
( ) IPhase in transport & kinetics f Ij =η
I0
I0
I0 P ,C ,T
Time & Length ScalesReactor Eddy or Particle Molecular
II0
II0
II0 P ,C ,T
)T,C(R )C(L IIb
IIb
IIIIIIb
II η=
∑ −=j
IIb
IIb
IIj
IIjR
IIb
IIh )T,C(R )H( )T(L II
jηΔ
( ) IIPhase in transport & kinetics g IIj =η
III P ,C ,T
IIIIII P ,C ,T
Phase II
Phase IIeQ I, Phase
IIeQ II, PhaseII
inQ II, Phase
IinQ I, Phase
Reactor Performance Determines Raw Material Utilization, Separations,Recycle Streams, Remediation, and Hence Process Economics & Profitability