SYSTEMATIC METHODS FOR SOLVENT DESIGN: TOWARDS BETTER REACTIVE PROCESSES Eirini Siougkrou National Technical University of Athens KT Consortium annual meeting, DTU 8 June 2017
Outline • Systematic methods for solvent design • A methodology for the integrated design of a gas-expanded liquid and reactive system • Ab-Initio Computer-Aided Molecular Design for the Identification of Optimal Solvents for Reactions • Semantics and Process Systems Engineering
Outline • Systematic methods for solvent design • A methodology for the integrated design of a gas-expanded liquid and reactive system • Ab-Initio Computer-Aided Molecular Design for the Identification of Optimal Solvents for Reactions • Semantics and Process Systems Engineering
Solvents and chemical reactions • The importance of solvents in chemical reactions is well known: nitromethane 0.4 • bring reactants together acetonitrile • temperature control 0.3 acetone • selectivity/reaction rate [P] (mol/L) 0.2 • transport THF • separation 0.1 chloroform toluene Reaction rate constants • 0.0 0 200 400 600 800 1000 1200 1400 1600 1800 can vary by several orders t (s) The concentration of the product for different of magnitude from solvent solvents for the Menschutkin reaction of phenacyl to solvent. bromide and pyridine 1 : H. Struebing et al., 2013 Solvent optimisation very important Need for alternative “green” solvents
Objectives • The development of novel methodologies for the design of solvents for chemical reactions • Two aspects considered: Design of solvent mixture CO 2 -expanded solvents • experimental data needed • integration in process design • Ab-initio solvent design no experimental data • generic QM-CAMD methodology •
6 Gas-Expanded Liquids (GXLs) GXLs 1 are mixed solvents composed of: organic solvent + compressible gas (usually CO 2 ) • Why mixed solvents? • tuneable properties combination of desirable properties of co-solvents elimination of undesirable properties of co-solvents 500 g PA / kg solvent Solubility of 400 paracetamol in 300 water+acetone 200 mixture, at T = 23 ◦ C. 100 0 0 25 50 75 100 mass % water in acetone R.A. Granberg, A.C.Rasmuson, 2000 P.G.Jessop, B.Subramanian, 2007
6 Gas-Expanded Liquids (GXLs) GXLs 1 are mixed solvents composed of: organic solvent + compressible gas (usually CO 2 ) • Why mixed solvents? • Why GXLs? • tuneable properties • recovery and recycle of both the organic solvent and CO 2 through depressurisation • moderate operating pressures 500 g PA / kg solvent Solubility of 400 • enhanced transport rates and reaction paracetamol in 300 rates water+acetone 200 mixture, at T = 23 ◦ C. 100 0 • reduced environmental impact 0 25 50 75 100 mass % water in acetone R.A. Granberg, A.C.Rasmuson, 2000 GXLs meet process and environmental requirements P.G.Jessop, B.Subramanian, 2007
Objectives To develop a methodology for the integrated design of a reactive system including a solvent mixture. Given a reaction and a production rate, find the optimal CO 2 -expanded solvent equipment size operating conditions that minimise the total cost of the process. Case study: the Diels-Alder reaction of anthracene with PTAD. Challenges: high pressure presence of solids effect of solvent composition on reaction rate
Our Model • For the process we consider a CSTR , a separator (evaporator), a condenser and a compressor . Compressor Condenser CSTR • T = 40 o C • Neglect heat effects Separator • treated as black box The model is implemented in gPROMS 1 . • solvent evaporation only • 100% recovery 1. Process Systems Enterprise, gPROMS, 1997-2009
Our Model • The model can be divided in five sub-models: Reaction rate constant model: Solvatochromic equation 1 Composition dependence of solvent properties 2 Phase Equilibrium: Group-contribution VTPR EoS 3 Process mass balances ∗ = + π + α + β k k s a b 0 Cost model = + + s s s Y x Y x Y x Y 1 1 2 2 12 12 • Organic co-solvents: acetonitrile , − + + − 2 2 acetone , methanol . Y ( 1 x ) Y f ( x ) Y f ( 1 x ) x = 1 2 2 2 / 1 2 12 12 / 1 2 2 Y − + + − 2 2 ( 1 ) ( ) ( 1 ) x f x f x x 2 2 / 1 2 12 / 1 2 2 Fitted to experimental 1. J.W. Ford, J.Lu, C.L.Liotta, C.A.Eckert, 2008 data. 2 . C.Ràfols, M.Rosés, E.Bosch, 1997 E. Siougkrou, A. Galindo, C.S. Adjiman, 2011 E. Siougkrou, A. Galindo, C.S. Adjiman, 2014 3. J.Ahlers, T.Yamaguchi, J.Gmehling, 2004
Reaction Rate Constant acetonitrile + CO 2 acetone + CO 2 Solubility methanol + CO 2 0.006 3 0.005 2.5 0.004 2 x anthracene k (s -1 ) 1.5 0.003 1 0.002 0.5 0.001 0 0 0 0.2 0.4 0.6 0.8 1 0 2 4 6 8 10 x CO2 P (MPa) • The reaction rate constant The solubility of anthracene increases with increasing decreases with increasing x CO2 in all mixed solvents. x CO2 in all mixed solvents. J.W. Ford, J.Lu, C.L.Liotta, C.A.Eckert, 2008 E.A.Cepeda, M.Diaz, 1996 E. Siougkrou, A. Galindo, C.S. Adjiman, 2014 L.N. Petrova, 1974
Volume of the CSTR and Cost of the Process acetonitrile + CO 2 acetone + CO 2 1400000 1 0.9 1200000 0.8 Total Cost ($/year) 1000000 0.7 V reactor (m 3 ) 0.6 800000 0.5 600000 0.4 0.3 400000 0.2 200000 0.1 0 0 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 x CO2 x CO2 Methanol not shown as it requires very large volumes. Both acetonitrile and acetone seem to be suitable co-solvents. Optimum x CO2 = 0.45 in acetone. Taking into account environmental criteria, the optimum x CO2 is around 0.7. E. Siougkrou, A. Galindo, C.S. Adjiman, 2014
Volume of the CSTR and Cost of the Process acetonitrile + CO 2 acetone + CO 2 1 550000 0.9 0.8 Total Cost ($/year) 450000 0.7 V reactor (m 3 ) 0.6 350000 0.5 0.4 250000 0.3 0.2 150000 0.1 0 50000 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 x CO2 x CO2 Methanol not shown as it requires very large volumes. Both acetonitrile and acetone seem to be suitable co-solvents. Optimum x CO2 = 0.45 in acetone. Taking into account environmental criteria, the optimum x CO2 is around 0.7. E. Siougkrou, A. Galindo, C.S. Adjiman, 2014
Outline • A methodology for the integrated design of a gas- expanded liquid and reactive system • Ab-Initio Computer-Aided Molecular Design for the Identification of Optimal Solvents for Reactions
Objectives To develop a methodology for the design of the optimal solvent that maximises the rate constant of a given reaction. • Enables solution of more complex problems to be tackled • e.g., selectivity maximisation • Requirements of the methodology: Consider a large number of candidate solvents and take into • account multiple constraints & objectives ⇒ Computer-Aided Molecular Design (CAMD) Based on reliable prediction of kinetics ⇒ • Quantum Mechanics (QM) + Group Contribution (GC) Computational efficiency ⇒ limit number of QM calculations •
Solvent design problem A Computer-Aided Molecular Design optimisation formulation ( ξ f ) max n y ξ , , n y = ξ h ( , , ) 0 1 structure-property constraints n y ≤ ξ g ( , , ) 0 1 n y = chemical feasibility and molecular h ( , ) 0 2 n y complexity constraints ≤ g ( , ) 0 2 , n y ≤ ξ design constraints d ( , ) 0 m ∈ ℜ ξ physical properties n q ∈ ℜ number of groups in molecule { } q = binary variables y ∈ u i 1 ,..., 0 , 1 i
Solvent design problem However, the consideration of reaction kinetics brings significant challenges ( ξ reaction rate constant f ) max n y ξ , , n y = ξ h ( , , ) 0 1 structure-property constraints n y ≤ ξ g ( , , ) 0 1 n y = h ( , ) 0 2 n y ≤ g ( , ) 0 2 , n y ≤ ξ d ( , ) 0 m ∈ R ξ n q ∈ R { } q = y ∈ u i 1 ,..., 0 , 1 i
Property prediction for solvent design Continuum Solvation 2 Atoms Group Contribution Quantum Mechanics methods 1 Α Β ε k γ n D φ ψ solute at electronic scale solvent at macroscale solvent at macroscale described with bulk properties 1. T. J. Sheldon et al., Fluid Phase Equilibria 231 (2005) 27-37 2. A. V. Marenich et al., J.Phys. Chem. B 113 (2009) 6378-6396
Reaction rate constant from Quantum Mechanics • Rate constant from Conventional Transition State Theory (CTST): R 1 + R 2 ↔ TS → P O N Br ∆ ∆ ‡ G , solv O N Br O N Br
Reaction rate constant from Quantum Mechanics Free energy of solvation • Rate constant from Conventional Transition State Theory (CTST) using the SMD solvation model: R 1 + R 2 ↔ TS → P = ∆ ∆ activation free ε, Α, Β, γ, φ,ψ ‡ , solv k f ( G ( n , )) TST D energy of solvation ( ) ( ) ∆ = ∆ + ξ ε, ε, γ, φ,ψ o , solv * G ( ) min E ( ; A ) G A , A, B, n , r r i S ENP , i i CDS , i i D r i electrostatic non-electrostatic contribution contribution ( ) Bilevel problem ε = ∆ ε * , A arg min E ( ; , A ) r r with embedded i ENP , i i r i QM calculations
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