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G-L Taylor Flow reactor system Oxidation of ethylbenzene
R. Sumbharaju
L.A. Correia D.F. Meyer
Y.C. van Delft A. de Groot
This presentation was presented at the CAMURE-8 & ISMR-7 conference,
Naantali, Finland, 22-25 May, 2011 ECN-M--11-084 AUGUST 2011
www.ecn.nl
G-L Taylor Flow reactor system Oxidation of ethylbenzene
R. Sumbharaju, L.A. Correia, D.F. Meyer, Y.C. van Delft and A. de Groot
2 23-8-2011
Contents• ECN – Research E&I • Research PI
- Process and technology selection• Structured reactor• Realization prototype reactor
- Selection of G/L oxidation process- Prototype
• Experimental- Process window
• Kinetics• Hydrodynamics
- Results- Summary- Future work
3 23-8-2011
• Largest Dutch R&D institute on energy • Independent and committed• Link between fundamental academic research and market application
Mission statementECN develops and brings to market high-level knowledge and technology for a sustainable energy society
ECN Mission and Units
Solar energy Wind energyBiomass Policy Studies
ECN Business units
Efficiency & Infrastructure
Research areas ECN - E&I
4 23-8-2011
by products
rawmaterials
clean air
clean water
Scheiding
Separation
Separation
Separation
SeparationREACTOR
Waste heat
1. Industrial waste heat
3. Process intensification/ Multifunctional reactors
2. Molecular Separation Technology
Process and technology selection
5 23-8-2011
NH3+MeOH21%
Others (exo)11%
Others (endo)5%
Oxidation30%
Cracking19%
Oxi
datio
n
Cra
ckin
g
Am
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Hyd
roge
natio
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Deh
ydro
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tion
Hyd
ratio
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Deh
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Con
dens
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Alk
ylat
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Isom
eriz
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MR / pervaporation membrane 0 0 0 0 0 7 2 26 0 0MR / hydrogen selective 0 0 21 0 19 0 0 0 0 0Catalytic membrane reactor 5 3 1 0 1 0 1 0 1 1HEX-reactor 48 29 0 2 6 19 3 0 15 0Structured (monolith) reactor 22 0 0 1 0 15 2 1 2 1Micro-reactor 54 28 3 5 8 27 5 4 8 3Short residence time reactor 11 9 0 0 2 0 2 0 2 0Reactive distillation 4 20 14 1 11 2 2 20 3 11Sorption enhanced reactor 7 21 21 1 19 4 1 26 6 18Supercritical reactor 8 0 0 10 0 10 4 11 0 4Advanced distillation 7 14 1 19 4 0 6 18
Relative energy usage NL
J. Hugill Monolith reactors for gas-liquid reactions: Internal ECN Report
Technologies for process intensification
6 23-8-2011
Structured reactor and Taylor flow
Close to plug flow
Thin liquid layerseparates gas/solid Intensive mixing in the slugs
• Good mass transfer• Good mixing in the liquid slugs• Overall plug flow• Good heat transfer
Structured reactor - 2-phase flow pattern
7 23-8-2011
Flow patterns depend on VG ,VL[1]Best operating condition for the reaction in the channels is Taylor flow (PF).
[1] Kreutzer et al (2001), Chem. Engg. Sci. 56 (2001) p.p.:6015-6023
Bubble flow Taylor flow Unstable slug flow
Annular flow
8 23-8-2011
Process selection for energy savings in NL [1]
• Inventory of oxidation processes in the NL• Selection of top 5 oxidation processes in NL based on energy usage• Selection of one process based on
-Total production capacity in the NL-Reaction heat-Temperature-Pressure-Catalyst
• Result : Styrene - Propylene oxide process
Styrene process
9 23-8-2011
Focus area
EB oxidation to EBHPProcess conditions:P = 2 barT = 140 °CConversion = 10 wt%Selectivity = 90 %Residence time = 1 hr
Realization prototype reactor• G/L oxidation reactions are highy exothermic in nature • Formation of explosive gas mixtures • Demanding high safely operating equipment
Procedure for realization prototype reactor:- Chemical and physical hazards- Conceptual design of installation - Critical operation hazards and required safety measures- Detailed design of installation- Prototype - computer controlled
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11 23-8-2011
Prototype Taylor flow reactor
Prototype Taylor flow reactor - control unit
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13 23-8-2011
Prototype Taylor flow reactor
Reactor Section G/L separator and product Section
Feed Section
Preliminary oxidation study
14 23-8-2011
Demonstrating that in TF mode oxidation can be performed with improved yield.
• Verification of flow pattern with water/N2 and different P and T.
• Development of a kinetic model for EB oxidation
Defining process window
Operating window - fluid flow
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◊ Unstable region□ Border region○Taylor/Plug flow
Prediction of Temp. window by Kinetic model
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[1] A.Yurdakul “Reactor Modelling of GL Reactions in Small Channels Intermediate Report” ECN-ei-2009-265
17 23-8-2011
Experimental Program (1)Reaction steps in oxidation of Ethylbenzene
Autocatalytic reaction• Initiation (Low residence time improve initiation rate)• Propagation• Termination
Competing reactions for byproducts• Decomposition of Ethylbenzene hydroperoxide
L.A. Tavadyan et al., Kinetics and Catalysis, 44, 91-100, 2003
Preliminary results Different commercial initiators: A, B, C (4 mol%)
18 23-8-2011
Initiator A shows highest Yield
19 23-8-2011
Experiment vs Kinetic model
• Industrial yield is in agreement with the model at 140 °C• Experimental yield is lower than the model at 180 °C• By-product formation in our reactor at 180 °C is higher than predicted
Summary
• Prototype CRS can handle dangerous reactions without reaching explosive situations.
• Oxidation in TF mode is demonstrated.• In the prototype CRS EBHP yield is lower than expected. • Hydrodynamic results are in agreement with the literature.• Yield highly depends on initiator type.
20 23-8-2011
Plans for future
• Experimental kinetic studies (increasing yield) - Reactor geometry- Process conditions
• Other oxidation reactions
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22 23-8-2011
Questions
Commercial Initiators:A
23 23-8-2011
• Increase of temperature increases conversion and selectivity• wt% increase in concentration has negative effect on selectivity• 180 °C is promising for selection
24 23-8-2011
Small channels- Small fluid mixture hold-up: safe operation of explosive mixtures
Increased mass and heat transfer - Heat transfer: Large surface-area/volume ratio - Improved temperature control- Mass transfer: Large contact area of the phases.- Improved mixing in Taylor flow (TF) operation
Structured reactor in 2-phase flow (1)
[1] F.Kaptein et al ,CATTECH, Vol 3(1999), No.1,24-41
Hydrodynamics – Flow windowExperimental vs literature
25 23-8-2011
Taylor flow boundary [1]• Dimensionless number, We, flow pattern map for all
experimental conditions, p and t shows a sharp border between Taylor and bubble flow:
6.05.5 GSLS WeWe =
Gas hold-up [1]• Armand correlations relates gas hold-up to the gas volume
fraction
• Found Armand correlation is: 0.88.
GG βε 833.0=
LG
GG VV
V+
=βSSSS
SG LG
WLG
G+
−++
= )16
(πε
Gas slug length (GS) [1]• The gas slug length scales linearly with the ratio VG/VL .
• For our system, α1=1.24 and α2=0.59 (α1=1.0 and α2=1.0 [2])L
G
VV
WGs
21 αα +=
[1] Jun, Y., et al, Chem. Engineering Science, 63, pp. 4189-4202, 2008[2] van Steijn, V. (2010): Formation and Transport of Bubbles in Micro-Fluidic Systems. pp. 136, Delft, 2010.