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Process Intensification

Methanol carbonylation process for the synthesis of acetic acid
by

Jan Fockedey

on 17 June 2015

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Transcript of Process Intensification

Water is necessary for catalyst activity & stability and higher reaction rate (here already higher)
Requires use of ceramic/silica membranes
Methanol carbonylation process for the synthesis of acetic acid
Process Intensification in the Chemical Industry [H09E5a]
May 18, 2015
Students:
Jan Fockedey
Senne Fransen
Katja Huys
Brecht Van Severen
Professor:
Prof. dr. ir. Tom Van Gerven
Acetica process simplified flow sheet
Reaction
Separation
Reaction time
Side products
Water level
Extensive separation train
Catalyst inactivation
Slurry
1
2
3
4
5
5
6
Packed bed reactor
Monolith reactor
Catalytic foam reactor
Membrane reactor
Off-gases
Packed bed reactor
Catalyst
recirculation
Cooler
Methanol
Random
Structured
Catalyst coated on packing
Technology
CO
Column containing packing
Good mass transfer
Low pressure drop
Application in this process
Replace bubble column reactor

Catalyst immobilization: no catalyst recycle required
Large catalyst surface possible
Ceramic packing for corrosive environment
Bottleneck scoring
Well-known, fully developed technology
Uncertainty on cost (cleaning/replacement cost, corrosion-resistant packing, cost of coated catalyst)

No effect on either term
0
0
No direct effect on selectivity
0
No effect
+1
Better mixing: less dead zones of CO
+2
Catalyst immobilized on packing
0
No effect
0
No effect
0
Reaction time:

Side products:

Water level:

Catalyst inactivation:

Slurry:

Separation train:

Safety:

Costs & reliability:
1
3
1
2
4
5
6
8
7
Laminar: low pressure drop
Uniform residence time
Excellent mass transfer
Membrane distillation
Application in this process
Replace light ends column
Bottleneck scoring
Not fully developed
Commercial modules are still quite expensive
Simpler control and automation
No effect
0
0
No effect
0
No effect
0
No effect
0
No effect
+1
Lower energy requirements
Low-grade energy can be used
+1
Smaller volume
Lower operating temperature
Reduced vapor spaces
0
Reaction time:

Side products:

Water level:

Catalyst inactivation:

Slurry:

Separation train:

Safety:

Costs & reliability:
3
1
2
4
5
6
8
7
Monolith reactor
Technology
Honeycomb structure
Application in this process
Replace bubble column reactor

Catalyst immobilization: no catalyst recycle required
Large catalyst surface possible
Uniform CO concentration
Bottleneck scoring
Low pressure drop
Simple reactor
Immature technology

High surface/volume ratio: larger catalyst surface
Plug flow: no shortcuts & uniform residence time
+2
+1
Uniform residence time -> better control
0
Minor effect: less side products & higher catalyst stability
+2
Uniform CO concentration due to high G-L mass transfer
+2
Catalyst immobilized on channel wall
Laminar flow: less erosion of catalyst coating
0
Minor effect by improved selectivity
+1
Reduced reactor size
+1
Reaction time:

Side products:

Water level:

Catalyst inactivation:

Slurry:

Separation train:

Safety:

Costs & reliability:
3
1
2
4
5
6
8
7
Catalytic foam reactor
For gas and/or liquid reactants
Different materials (carbon, metal, plastic, ceramic)
Technology
Solid foam structure as support for catalyst
Enhanced mass transfer
Low pressure drop
Very light
Application in this process
Replace bubble column reactor

Catalyst immobilization: no catalyst recycle required
High porosity (100 PPI) leads to high surface/volume ratio
Uniform CO concentration
Bottleneck scoring
Expensive foam based catalyst
Immature technology
Turbulent flow => more erosion => catalyst loss and abrasion downstream

High surface/volume ratio: larger catalyst surface
+2
0
No direct effect on selectivity
+1
+2
Better mixing: less dead zones of CO
Enhanced catalyst stability
+2
Catalyst immobilized on packing
0
No effect
0
No effect
-2
Reaction time:

Side products:

Water level:

Catalyst inactivation:

Slurry:

Separation train:

Safety:

Costs & reliability:
3
1
2
4
5
6
8
7
Membrane reactor
Catalyst immobilized on membrane surface (cf. monolith reactor)
Catalyst retained inside reaction volume
Technology
Process integration: catalytic reaction + membrane separation
Application in this process
Integrate reactor and first separation

Selectively permeate product: acetic acid
Keep byproducts inside the reaction mixture: suppress side-reactions
Bottleneck scoring
Process integration: reduced capital costs
Reduced distillation energy & use pressure of reaction for separation
Cheap membrane technology (e.g. UF) but short membrane lifetime in harsh conditions
0
+2
Reactants retained: equilibrium shift
Side products retained: equilibrium shift
Side reaction of methylacetate
+1
Less water needed to
suppress side reactions
0
No effect on CO mixing
0
+2
Water & methyliodide retained to large extent
Side products retained to small extent
+2
Process integration: reduced total volume & inventory
Membrane must be resistant to corrosive environment
+1
Reaction time:

Side products:

Water level:

Catalyst inactivation:

Slurry:

Separation train:

Safety:

Costs & reliability:
3
1
2
4
5
6
8
7
Pervaporation
Mechanism: solution-diffusion including evaporation
Technology
Membrane technique to remove water from organics
Application in this process
Dilemma:
Bottleneck scoring
PV is more energy efficient
PV is modular and smaller footprint
Relatively developed technology
Membrane replacement may be an important cost
No effect
0
+2
No recirculating water/acetic acid mixture:
0
No effect
0
No effect
0
No effect
+2
Dehydration column eliminated
+1
Reduction of inventory
+1
Reaction time:

Side products:

Water level:

Catalyst inactivation:

Slurry:

Separation train:

Safety:

Costs & reliability:
3
1
2
4
5
6
8
7
Often ceramic
Catalyst wall coating
Gas/liquid contact
Taylor flow
High surface/volume ratio
Difficult G-L distribution
Bottlenecks
Bottlenecks
Ideas
Selective product separation
2 catalyst configurations possible
Keep reagents inside the reaction mixture: improve reaction equilibrium
Sizing & design
a) Catalyst immobilization: + 2
b) Catalyst retention: 0
Sizing
Necessary membrane surface:
Aim: reduce water content in retentate from 8 wt% to 1 wt%
98 wt% pure actic acid in retentate
1 wt% water and 1 wt% sideproducts
5% losses downstream
8000 operational hours per year
Wijsmans and Baker:
Membrane is preferentially permeated by the minor component (water)
Application range 2wt% - 20wt% water
Vacuum allows to remove 90wt% water
Until 99wt% purity of organics
= 99 wt% (1 wt% water)
= 92 wt%
1) we want water in the reactor to suppress side reactions
2) we do not want water in the distillation towers
(very close boiling points)
Water in ideal concentration range (2-20 wt%)
Efficient use of excess reaction heat and reaction pressure to drive pervaporation
Well-suited:
Use pervaporation to remove water before distillation and recycle water to reactor
Technology
Membrane as G-L contactor
Without dispersing gas and liquid
Vapor goes through and is continuously removed (e.g. sweep gas or condensation)
High S/V ratio
Lower operating temperatures
Possible to use waste heat

Membrane flux limitations
Removal of minor components (methyl iodide, methyl acetate)
Very suitable, because only small permeate flux required
Only for a single distillation column, so no major impact
Application window
Legend
0
+1
+2
-1
-2
Existing acetica process
Bubble column
Process
Technologies
10
1
8
6
Reaction section
Separation section
Concept selection table
Pervaporation
Membrane distillation
1. Is the size of the new process unit realistic?
2. Can the new technology fit in the application window?
3. If realistic, quantify the gains of the new technology
Pervaporation
Assumptions:
Process variables:
Membrane variables:
N =
=
membrane permeability
permeate concentration of acetic acid
(function of the membrane separation factor)
Membrane category 1: 0,13m³ (cube with z = 50cm)
Membrane category 2: 0,75m³ (cube with z = 90cm)
Membrane category 3: 7,8m³ (cube with z = 2m)
Literature research:
50 very suited membranes found for this specific situation:
# membranes with A<100m² : 1
# membranes with 100m²<A<1000m² : 6
# membranes with 1000m²<A<10000m² : 43
133 membranes found with data for acetic acid
Calculation of A:
Volume of process unit
Module choice: no extreme fouling
spiral-wound (200 - 800 m²/m³)
hollow-fiber (500 - 9000 m²/m³)
assume 600 m²/m³
Pressure:
4 atm (distillation) - 40 atm (reaction)
Standard pressures for membrane modules
Temperature:
80°C (distillation) - 200°C (reaction)
Membranes from literature research: typically tested for 25°C - 40°C
Some at 80°C - 100°C
Temperature can be decreased to 80°C before PV
Crosslinked PVA and PPSU are able to sustain high T
Corrosivity:
Concentrated acetic acid
All experiments performed for concentrated acetic acid (up to 99%)
Design
Unit size
Current dehydration distillation column:
Energy use
Aspen details
Distillation column specifications
Assumptions
Assumptions: 24 inch per tray
Height of column: 10 m
Assumption: Vg=0.8*Vflooding
Active tray area = 90% of total tray
No foaming
Diameter of column: 2 m
Aspen results
Number of stages: 16
Distillation column size: 30 m³
Reflux ratio: 5.55
Reboiler duty: 4.9 MW
PV unit:
Based on Aspen analysis
Based on sizing analysis (see earlier)
Current dehydration distillation column:
PV unit:
Based on Aspen analysis
Based on PV analysis
4.9 MW
30 m³
0.13 - 7.8 m³
0.7 MW
Aspen details
Distillation column specifications
Assumptions
Assumptions: 24 inch per tray
Height of column: 10 m
Assumption: Vg=0.8*Vflooding
Active tray area = 90% of total tray
No foaming
Diameter of column: 2 m
Aspen results
Number of stages: 16
Distillation column size: 30 m³
Reflux ratio: 5.55
Reboiler duty: 4.9 MW
But 1.1 MW energy available in stream
(cooling required between reactor and distillation)
PV analysis details
Pervaporation unit specifications
Heat duty required for PV
Q=P*xHAc*HvapHAc+P*(1-xHAc)*HvapH2O
Median over all membranes in literature= 0.7 MW
Heat available in stream
Based on heat of evaporation of permeate stream:
Assume pure HAc in feed
Q=m*Cp*deltaT=1.1 MW
Note: The heat can no longer be used for other purpose, e.g. steam production
Based on cooling of reactor product (200°C) to distillation conditions (80°C)
Sizing
Necessary membrane surface:
Aim: 97.5 wt% pure acetic acid in permeate
keep 75% of water inside reactor => 2 wt% water in permeate
keep 50% of sideproducts inside reactor => 0.5 wt% sideproducts in permeate
5% losses downstream
8000 operational hours per year
Application window
Membrane reactor
Assumptions:
Process variables:
Membrane variables:
N =
=
membrane permeability
( permeate concentration of acetic acid)
Literature research:
24 membranes found
Pressure:
30 - 60 bar (reaction)
Temperature:
150°C - 200°C (reaction)
Corrosivity:
HI (very corrosive)
and concentrated acetic acid
Existing membranes are not suitable for permeating such large fractions of organics out of water
Most membranes retain acetic acid and permeate water
Special membranes required (less applications in literature):
organophilic PV membranes
organophilic NF membranes
Found membranes:
Only methylacetate, methanol, etc. (not acetic acid)
Only very low concentration of organic component in water
Typically 99% water and 1% organics
Only 4 membranes with 15-30 wt% organics
vs. now: 91 wt% organics
Possible (see earlier)
Literature research: only 1 silica-based membrane applicable
Ceramic NF membranes: more difficult to obtain reproducible pores
Sizing
Reactor volume depends on reaction kinetics
Monolith reactor
Pressure:
30 bar - 60 bar (reaction)
Monoliths tested up to 80 bar
Temperature:
150°C - 200°C (reaction)
Monoliths used in car exhaust de-NOx
Melting point of Cordierite exceeds 1450°C
Cordierite: very low thermal expansion coefficient
Corrosivity:
HI and concentrated acetic acid
Ceramic monoliths: OK
Design
Unit size
Potential size reduction:
Energy use
Based on sizing analysis (see earlier)
Strong reduction in pressure drop:
-97% (factor 36)
-72% (factor 3.6)
Depends on volume of catalyst /m³ reactor
Application window
Current bubble column:
0.08 m³ resin /m³ reactor
Assumptions/references:
Patent: 10 wt% rhodium ion carrying resin/methanol
Pure methanol in reactor
Mass gaseous phase is negligible
Monolith reactor bubble column:
0.29 m³ resin /m³ reactor
Assumptions/references:
Flow map of Jayawardena (1997)
Monolith reactor 3.6 times smaller than current bubble column
Monolith has at least 10 times lower P/V ratio
For same mass transfer coefficient
Ensuring homogeneous CO concentration
Device map Kreutzer et al. (2006)
8
4
4
Reaction time
2
Side products
3
Water level
4
Catalyst inactivation
5
Slurry
6
Separation train
7
Safety
8
Costs and reliability

Increase catalyst concentration
Suppress side-reactions
Reduce water level without reducing its benefits
Prevent zones without CO
Mass transport and mixing
Immobilise catalyst
Combine separations
Different separation technique
Reduce inventory
Reduce production of dangerous side products
Weight
Conclusions
Monolith reactor replaces bubble column
Size footprint /3.6
Energy use /36

PV unit replaces dehydration column
Size footprint /4 to 200
Energy use /7

Task distribution
References I
No acetic acid recycled to reactor (equilibrium shift)
Less methylacetate side-product
Less distillation towers
No circulation of acetic acid/water mixture through plant
Only polishing needed (PV feasible until 99,8% purity)
Less water transported through light-ends column
Bottleneck analysis: Individual + together
Creating ideas: Brainstorm together
Concept screening:









Design and sizing:






Presentation: Together

Depends on situation:
Take worst-case scenario
4
Flow pattern: slug flow
= 10
diameter of single capillary = 2.8 mm
Improvement
Volume catalyst/volume reactor
Washcoat:
assume width = diameter original catalyst
= 0.2 mm
= 0.29 m³ resin /m³ reactor
In addition,
r
Pressure drop reduction:
Reaction product
Packed bed reactor
Seader, J.D. and Henley, Ernest J. and Roper, D. Keith; Separation Process Principles, 3rd Edition; United Kingdom: John Wiley & sons

Monolith reactor
Kreutzer, Michiel T. and Du, Peng and Heiszwolf, Johan J. and Kapteijn, Freek and Moulijn, Jacob A.; Mass transfer characteristics of three-phase monolith reactors; Chemical Engineering Science 56 (2001), 6015-6023
Crezee, Edwin and Barendregt, Arjan and Kapteijn, Freek and Moulijn, Jacob A.; Carbon coated monolith catalysts in the selective oxidation of cyclohexanone; Catalysis Today 69 (2001), 283-290
Cybulski, A. and Stankiewicz, A. and Edvinsson Albers, R.K. and Moulijn, J.A.; Monolithic Reactors for Fine Chemicals Industries: A Comparative Analysis of a Monolithic Reactor and a Mechanically Agitated Slurry Reactor; Chemical Engineering Science 54 (1999), 2351-2358
Haakana, T. and Kolehmainen, E. and Turunen, I, and Mikkola, J.P. and Salmi, T.; The development of monolith reactors: general stratey with a case study; Chemical Engineering Science 59 (2004), 5629-5635

Catalytic foam reactor
European Federation of Chemical Engineering (EFCE); Report on the European Roadmap for Process Intensification, Appendix 1; 2015
Leon, Maria A. and Tschentscher, Roman and Nijhuis, T. Alexander and van der Schaaf, John and Schouten, Jaap C.; Rotating Foam Stirrer Reactor: Effect of Catalyst Coating Characteristics on Reactor Performance; Industrial & Engineering Chemistry Research 50 (2011), 3184-3193

Membrane reactor
Gallucci, Fausto and Fernandez, Ekain and Corengia, Pablo and van Sint Annaland, Martin; Recent advances on membranes and membrane reactors for hydrogen production; Chemical Engineering Science 92 (2013), 40-66
Gallucci, Fausto and Basile, Angelo and Hai, Faisal Ibney; Introduction - A review of membrane reactors; Membranes for membrane reactors: preparation, optimization and selection (2011), 1-61; United Kingdom: John Wiley & sons.
Mao, Xue and Si, Yang and Chen, Yuecheng and Yang, Liping and Zhao, Fan and Ding, Bin and Yu, Jianyong; Silica nanofibrous membranes with robust flexibility and thermal stability for high-efficiency fine particulate filtration; RSC Advances 2 (2012), 12216-12223


References II
Pervaporation
Wynn, Nick; Reactions and Separations: Pervaporation: Comes of Age; Sulzer Chemtech Membrane Systems; www.cepmagazine.org; October 2001
Van Baelen, D. and Van der Bruggen, B. and Van den Dungen, K. and Degrève, J. and Vandecasteele, C.; Pervaporation of water-alcohol mixtures and acetic acid-water mixtures; Chemical Engineering Science 60 (2005), 1583-1590
Chapman, Peter D. and Oliveira, Teresa and Livingston, Andrew G. and Li, K.; Membranes for the dehydration of solvents by pervaporation; Journal of Membrane Science 318 (2008), 5-37
Van der Bruggen, B.; Course text: Advanced seperation processes (2013); KULeuven
Alghezawi, N. and Şanli, O. and Aras, L. and Asman, G.; Separation of acetic acid-water mixtures through acrylonitrile grafted poly(vinyl alcohol) membranes by pervaporation; Chemical Engineering and Processing 44 (2005), 51-58
Jullok, Nora and Darvishmanesh, Siavash and Luis, Patricia and Van de Bruggen, Bart; The potential of pervaporation for separation of acetic acid and water mixtures using polyphenylsulfone membranes; Chemical Engineering Journal 175 (2011), 306-315

Membrane distillation
Wiesler Fred; Membrane contactors: An introduction to the technology; Hoeschst Celanese Corp. Ultrapure water (1996)
Van der Bruggen, B.; Course text: Advanced seperation processes (2013); KULeuven
Lawson, Kevin W. and Lloyd, Douglas R.; Review: Membrane distillation; Journal of Membrane Science 124 (1997), 1-25
Wódzki, R. and Nowaczyk, J. and Kujawski, M.; Separation of propionic and acetic acid by pertraction in a multimembrane hybrid system; Separation and Purification Technology 21 (2000), 39-54


Thank you!
Questions?

P =
General bottlenecks
Safety
Costs & reliability
5
5
7
8
R =
Methanol feed
Off-gases
Sulzer Chemtech, 2015
Van Gerven et al., 2013
Stutz et al., 2015
MFG Trade, Inc., 2015
Gallucci et al., 2013
KmX Corp., 2015
Van der Bruggen, 2013
Full transcript