Elizabeth M. Hill, James M. Broering, Jason P. Hallett, Charles L. Liotta, Charles A. Eckert, Andreas S. Bommarius, “Coupling Chiral Homogeneous Biocatalytic Reactions with Benign Heterogeneous Separation,” Green Chemistry, 9, 888-893, 2007.

We describe a method for sustainable biocatalysis in an organic aqueous tunable solvent (OATS) system in which a hydrophobic substrate is transformed with a homogeneous enzymatic catalyst in a single liquid phase. Subsequent CO 2 addition produces a biphasic mixture where the hydrophobic product partitions preferentially into the organic rich phase for separation while the hydrophilic enzyme catalyst partitions into the aqueous rich phase, where it is recyclable. Greater than 99% enantiomeric excess (ee) is shown for catalyzed hydrolysis of rac -1-phenylethyl acetate with Candida antarctica lipase B (CAL B) both before and after CO 2 -induced separation. Additionally, processing parameters in OATS systems are discussed. This system combines homogeneous enzymatic reactions with a built-in heterogeneous separation for enantiomerically pure products.

 

D. Vinci, M. Donaldson, J. P. Hallett, E. A. John, P. Pollet, C. A. Thomas, J. D. Grilly, P. G. Jessop, C. L. Liotta, C. A. Eckert, “Piperylene Sulfone: a Labile and Recyclable DMSO Substitute,” Chem. Commun, 2007, 1427 - 1429.

The properties and uses of piperylene sulfone as a new, recyclable dipolar, aprotic solvent for conducting organic reactions are presented.

 

Ross R. Weikel, Jason P. Hallett, Charles L. Liotta , and Charles A. Eckert, “Self-neutralizing in situ acid catalysis for single pot synthesis of iodobenzene and methyl yellow in CO2-expanded methanol,” I&EC Res, 46, 5252 – 5257, 2007.

Despite widespread use, homogeneous acid catalysis has the drawback of requiring downstream neutralization, resulting in salt waste. Methylcarbonic acid is a self-neutralizing acid that forms in situ in methanol/CO 2 systems at mild pressures (10-47 bar) and then decomposes by depressurization. In the work presented here, methylcarbonic acid catalyzes the diazotization of aniline, which is either coupled with N , N -dimethyl aniline to form methyl yellow or reacted with iodide to form iodobenzene. The syntheses of methyl yellow and iodobenzene represent a class of industrially important reactions.

Charles Eckert, Charles Liotta , Arthur Ragauskas, Jason Hallett , Christopher Kitchens, Elizabeth Hill, and Laura Draucker , “Tunable Solvents for Fine Chemicals from the Biorefinery,” Green Chemistry, 2007, 545 - 548.

Making biorefineries economically and environmentally sustainable is the biggest barrier to the mass commercialization of biofuels in this country. One way to add economic value to the biofuel process is to isolate and extract fine chemicals from waste biomass such as lignin, extractives, and unreacted cellulose and hemicellulose. In this paper we demonstrate a technique for extracting high-value added chemicals such as vanillin, syringaldehyde, and syringol from lignin using a novel CO 2 -expanded organic solvent (gas-expanded liquid). This method incorporates many principles of green chemistry while offering several economical advantages to the biorefinery: low operating costs, easy recycling of organic solvents, use of a renewable feedstock, and a way to produce chemicals without wasteful synthesis. Furthermore, this technique demonstrated the ability to produce high-value chemicals ($5–25 lb –1 ) from a waste source that is presently being burned for a fuel value of 2–3 cents lb –1 . We believe the process presented in this paper will spark interest in developing other sustainable techniques to extract fine chemicals from biorefinery waste.

 

Gregory P. Robbins, Jason P. Hallett, David Bush , Charles A. Eckert, “Liquid-Liquid Equilibria and Partitioning in Organic-Aqueous Systems,” Fluid Phase Equil., 252, 48–53, 2007

Liquid–liquid equilibria at ambient temperature and pressure were measured for four ternary systems: n-hexane + THF + water, n-hexane + acetonitrile + water, n-hexane + 1,4-dioxane + water, and ethyl ether + 1,4-dioxane + water. Partitioning of 1-octene and 1-nonanal in these systems was also measured. The results were modeled with the UNIQUAC and NRTL gE models. The experiments showed an aqueous phase in the n-hexane–THF–water system that was 90% water on average, and an organic n-hexane phase in the n-hexane–acetonitrile–water system that was 96% n-hexane on average. 1,4-Dioxane distributes fairly equally to both phases in the n-hexane–1,4-dioxane–water and ethyl ether–1,4-dioxane–water systems .

 

Timothy C. Frank, John J. Anderson, James D. Olson, and Charles A. Eckert, “Application of MOSCED and UNIFAC to Screen Hydrophobic Solvents for Extraction of Hydrogen-Bonding Organics from Aqueous Solution,” I&EC Res, 46, 4621-4625, 2007.

Liquid-liquid extraction using hydrophobic extraction solvents is a technology well-suited to the removal of certain hydrogen-bonding organics from water or brine. Even when distillation is technically feasible, extraction might allow a significant reduction in energy consumption depending on the specific application. Various methods are available for estimating the partition ratio (K) to assess technical feasibility; however, these methods often provide only rough approximations because of the complexity of hydrogen-bonding interactions in solution. To better understand the application of the MOSCED and standard UNIFAC activity-coefficient prediction methods for screening extraction solvents, calculations were compared with K data for the extraction of propylene glycol n-propyl ether (PnP), a model hydrogen-bonding compound. Estimates of limiting activity coefficients for PnP dissolved in the organic phase (PnP,organic) obtained using MOSCED and UNIFAC are shown to be highly correlated with K data for a variety of hydrophobic organic solvents, including various alcohols, ketones, ethers, chlorinated hydrocarbons, aromatics, and aliphatic hydrocarbons. This example demonstrates how MOSCED or UNIFAC can be used to quickly rank candidate solvents for this class of compounds. The methodology facilitates process synthesis and design efforts by reducing the number of experiments required to identify suitable solvents.