Electrochemistry

Advances in the utilization of complex hydrocarbon mixtures require molecular understanding of the chemistry and catalysis of thousands of organic compounds. In the past few decades, transition away from lumped chemistry models to “big chemistry” molecular models has dramatically improved the efficiency of hydrocarbon refining. Parallel experimental efforts in reaction analysis and compositional analysis work in tandem to build and validate large, complex molecular models. Here we present two new experimental techniques for rapid reaction screening and quantification of complex reacting systems containing hundreds of organic compounds.

Mixtures of organic chemicals can comprise thousands of compounds, necessitating expensive and time-consuming separation and detection with conventional calibration techniques. In this first technique, we demonstrate a catalytic microreactor which allows for calibration-free quantification of organic compounds within gas chromatography [[i]]. Analyte compounds eluting a conventional gas chromatograph column flow into the microreactor, where a series of catalytic reactions convert each analyte to methane. Subsequent detection via flame ionization thus results in a common carbon response factor for all compounds. By this approach, mixtures of hundreds of compounds including thiophenes, polyaromatics, and complex hydrocarbons with many heteroatoms can be quantified without calibration [[ii]]. The method is introduced with respect to thermodynamic design constraints, and implementation with conventional gas chromatograph systems is described [[iii]].

Detailed molecular analysis can be combined with advanced chemical reaction screening. Building on the micro-catalytic method first proposed by Kokes and Emmet [[iv]], we have developed a continuous-flow microreactor for rapid evaluation of the reactions of complex molecules. By this method, small quantities of reactant are provided as step pulses to a micro-reaction chamber, with product sampling occurring at steady state. The use of small reactant quantities enables short-time reactor and catalyst studies, which can provide detailed kinetics of rapid catalyst activation/deactivation. When paired with the quantitative carbon detection method, the combined experimental reaction system can rapidly provide automated evaluation of thousands of reaction conditions, leading to multi-dimensional screening and identification of optimal reactor performance [[v]].

[i] "Quantitative Carbon Detector (QCD) for Calibration-Free, High-Resolution Characterization of Complex Mixtures," S. Maduskar, A.R. Teixeira, A.D. Paulsen, C. Krumm, T.J. Mountziaris, W. Fan, P.J. Dauenhauer, Lab on a Chip, 2015, 15, 440-447

[ii] "Quantitative Carbon Detector for Enhanced Detection of Molecules in Foods, Pharmaceuticals, Cosmetics, Flavors, and Fuels" Connor A. Beach, Christoph Krumm, Charles S. Spanjers, Saurabh Maduskar, Andrew J. Jones, Paul J. Dauenhauer. Analyst. 2016, 141, 1627-1632

[iii] "Increasing Flame Ionization Detector (FID) Sensitivity using Post-Column Combustion-Methanation," Charles A. Spanjers, Connor Beach, Andrew Jones, Paul J. Dauenhauer, RSC Analytical Methods 2017, 9, 1928-1934.

[iv] R.J. Kokes, H. Tobin, P.H. Emmett, “New microcatalytic-chromatographic technique for studying catalytic reactions,” Journal of the American Chemical Society 1955, 5861.

[v] "Renewable Isoprene by Sequential Hydrogenation of Itaconic Acid and Dehydra-Decyclization of 3-Methyl-Tetrahydrofuran," Omar A. Abdelrahman, Dae Sung Park, Katherine P Vinter, Charles S. Spanjers, Limin Ren, Hong Je Cho, Kechun Zhang, Wei Fan, Michael Tsapatsis, Paul J. Dauenhauer, ACS Catalysis 2017, 7(2), 1428-1431. DOI: 10.1021/acscatal.6b03335