Green Chemistry and the United States Environmental Protection Agency A Postdoc s Perspective James T. Ciszewski & Michael A. Gonzalez United States Environmental Protection Agency Office of Research and Development Sustainable Technology Division
Acknowledgements 4 Rivers Bioenergy, Inc. Mr. Tyler O Dell (Lake Superior State University) Disclaimer: It is understood the use of products in this research is not an endorsement by the U.S. Environmental Protection Agency.
Sustainable Chemistry The USEPA-ORD is dedicated to developing and enhancing technologies which increase the sustainability of chemical reactions Achieved using: Green Chemistry Green Engineering Life Cycle Assessment and Impact Assessment Industrial Ecology
Examples of Green Chemistry Alternative Solvents Supercritical Fluids Ionic Liquids Aqueous Solventless Systems Alternative Synthesis Techniques Ultrasound Microwave Green Oxidants Hydrogen Peroxide Molecular Oxygen Catalysis Nanotechnology
Process Intensification Ability to have a minimized physical and environmental footprint, while maintaining or increasing desired throughput Potential Benefits (some): energy usage solvent usage by-product formation separation steps worker safety feedstock utilization conversions and selectivities
Novel Reactors for Green Engineering Cooperative Research and Development Agreement (CRADA) with 4 Rivers Bioenergy Merging the catalyst expertise from EPA with the reactor technology of 4 Rivers Expands the scope of our program to include Green Engineering and Process Intensification Also incorporates reactor engineering into our sustainability program
STT Reactor Basics The STT is an annular thin-film reactor. Shear (mass transfer) and flow rate (residence time) are independently variable. Advantages include: improved reaction control (yield, selectivity) decreased reaction time (often 2-3 orders of magnitude) Easy scale-up
STT Reactor Basics
STT Flow Characteristics Thin-film flow is bounded between heat transfer surfaces Shear rate dependent on rotor speed and reactor dimensions (gap) Residence time dependent on reagent flow rate and reactor dimensions (length and gap) Axial plug flow Minimized back-mixing
Schematic Representation of the Process Liquid Pumps (syringe, gear, HPLC) Gases Mass flow meters Solid reagents dissolve and pump melt and pump suspend and pump suspension must be stable particle size must be compatible with rotor/stator gap
STT Reactor Technology Control Panel and Syringe Pumps
STT Reactor Technology Innovator - 28 ml working volume
STT Reactor Technology Magellan - 1.2 ml working volume
Reactions Investigated Ioinc Liquid Synthesis High conversion, high throughputs, minimal byproducts Imine synthesis Good to excellent yields of dialkyl substituted imines at moderate flow rates Cyclohexane Oxidation Cyclohexanol and cyclohexanone 5 min retention time (48x) same conversion and selectivity distribution Toluene Oxidation Can select product (benzyl alcohol, benzaldehyde and benzoic acid) based on retention time Ethylbenzene Oxidation Can select product distribution (alcohol product or acetophenone) based on RT Numerous proprietary reactions successfully explored under non-disclosure agreements (NDA s)
Synthesis of Ionic Liquids N N + RX N N R X - Current Synthesis Solvent intensive Long reaction times Cumbersome purifications Gonzalez, M. A..; Ciszewski, J. T. "High Conversion, Solvent Free, Continuous Synthesis of Imidazolium Ionic Liquids In Spinning Tube-in-Tube Reactors" Org. Process Res. Dev. 2009, 13 (1), 64-66.
Examples of Ionic Liquids Synthesized Entry Alkylating Reagent Equiv. T (ºC) Production Rate (kg/day) % Conversion 1 ethyl chloride 1.19 174 1.4 92 2 ethyl bromide 1.20 112 2.9 >99 3 ethyl iodide 1.06 83 16.6 >99 4 ethyl tosylate 1.25 102 8.1 >99 5 ethyl triflate 1.01 73 17.9 >99 6 isopropyl bromide 1.07 176 2.6 76 7 t-butyl bromide 1.06 106 2.9* >99 8 benzyl bromide 1.05 155 15.7 >99 9 butyl bromide 1.05 129 3.2 >99 10 hexyl bromide 1.05 131 18.3 >99 11 octyl bromide 1.05 142 8.4 >99 12 1,2-dibromobutane 0.48 158 5.0 >99 * Reaction produced 1-methylimidazolium bromide.
Conversion vs. Shear Rate
Synthesis of 1-methyl-3-butyl imdiazolium bromide
Conclusions The STT offers a continuous chemical process which has been investigated for a variety of chemical reactions The STT provides higher yields and conversions with decreased residence times when compared to batch processes Reactions have been demonstrated to be performed in a solvent-free environment Reactor design allows for real-time analysis and optimization Ionic liquid reactions were optimized in the matter of hours (3-4) rather than days or weeks Explorations into additional chemical reactions are currently on-going