Architectural Control of Isosorbide-Based Polyethers via Ring-Opening Polymerization.

Isosorbide is a rigid, sugar-derived building block that has shown promise in high-performance materials, albeit with a lack of available controlled polymerization methods. To this end, we provide mechanistic insights into the cationic and quasi-zwitterionic ring-opening polymerization (ROP) of an annulated isosorbide derivative (1,4:2,5:3,6-trianhydro-d-mannitol, 5). Ring-opening selectivity of this tricyclic ether was achieved, and the polymerization is selectively directed toward different macromolecular architectures, allowing for formation of either linear or cyclic polymers. Notably, straightforward recycling of unreacted monomer can be accomplished via sublimation. This work provides the first platform for tailored polymer architectures from isosorbide via ROP.

Quantitative carbon detector for enhanced detection of molecules in foods, pharmaceuticals, cosmetics, flavors, and fuels.

Analysis of trace compounds, such as pesticides and other contaminants, within consumer products, fuels, and the environment requires quantification of increasingly complex mixtures of difficult-to-quantify compounds. Many compounds of interest are non-volatile and exhibit poor response in current gas chromatography and flame ionization systems. Here we show the reaction of trimethylsilylated chemical analytes to methane using a quantitative carbon detector (QCD; the Polyarc™ reactor) within a gas chromatograph (GC), thereby enabling enhanced detection (up to 10×) of highly functionalized compounds including carbohydrates, acids, drugs, flavorants, and pesticides. Analysis of a complex mixture of compounds shows that the GC-QCD method exhibits faster and more accurate analysis of complex mixtures commonly encountered in everyday products and the environment.

On the Method of Pulse-Heated Analysis of Solid Reactions (PHASR) for Polyolefin Pyrolysis.

The continued need for plastics necessitates an effective solution for processing and recycling polymer wastes. While pyrolysis is a promising technology for polyolefin recycling, an experimental apparatus must be designed to measure the intrinsic kinetics and elucidate the chemistry of the plastics pyrolysis process. To resolve this issue, a modified Pulse-Heated Analysis of Solid Reactions (PHASR) system was designed, constructed, and evaluated for the purposes of polyolefin pyrolysis. Experimental results demonstrated that the new PHASR system is capable of measuring the millisecond-resolved evolution of plastic [e. g., low-density polyethylene (LDPE)] pyrolysis products at a constant temperature. The PHASR system was shown to be capable of producing a repeatable, fast heating time (20 ms) and cooling time (130-150 ms), and of maintaining a stable temperature during reaction. A second, Visual PHASR system was developed to enable high-speed photography and visualization of the real-time pyrolysis of LDPE.

Spontaneous Aerosol Ejection: Origin of Inorganic Particles in Biomass Pyrolysis.

At high thermal flux and temperatures of approximately 500 °C, lignocellulosic biomass transforms to a reactive liquid intermediate before evaporating to condensable bio-oil for downstream upgrading to renewable fuels and chemicals. However, the existence of a fraction of nonvolatile compounds in condensed bio-oil diminishes the product quality and, in the case of inorganic materials, catalyzes undesirable aging reactions within bio-oil. In this study, ablative pyrolysis of crystalline cellulose was evaluated, with and without doped calcium, for the generation of inorganic-transporting aerosols by reactive boiling ejection from liquid intermediate cellulose. Aerosols were characterized by laser diffraction light scattering, inductively coupled plasma spectroscopy, and high-speed photography. Pyrolysis product fractionation revealed that approximately 3 % of the initial feed (both organic and inorganic) was transported to the gas phase as aerosols. Large bubble-to-aerosol size ratios and visualization of significant late-time ejections in the pyrolyzing cellulose suggest the formation of film bubbles in addition to the previously discovered jet formation mechanism.

Quantitative carbon detector (QCD) for calibration-free, high-resolution characterization of complex mixtures.

Current research of complex chemical systems, including biomass pyrolysis, petroleum refining, and wastewater remediation requires analysis of large analyte mixtures (>100 compounds). Quantification of each carbon-containing analyte by existing methods (flame ionization detection) requires extensive identification and calibration. In this work, we describe an integrated microreactor system called the Quantitative Carbon Detector (QCD) for use with current gas chromatography techniques for calibration-free quantitation of analyte mixtures. Combined heating, catalytic combustion, methanation and gas co-reactant mixing within a single modular reactor fully converts all analytes to methane (>99.9%) within a thermodynamic operable regime. Residence time distribution of the QCD reveals negligible loss in chromatographic resolution consistent with fine separation of complex mixtures including cellulose pyrolysis products.

Reactive Liftoff of Crystalline Cellulose Particles.

The condition of heat transfer to lignocellulosic biomass particles during thermal processing at high temperature (>400 °C) dramatically alters the yield and quality of renewable energy and fuels. In this work, crystalline cellulose particles were discovered to lift off heated surfaces by high speed photography similar to the Leidenfrost effect in hot, volatile liquids. Order of magnitude variation in heat transfer rates and cellulose particle lifetimes was observed as intermediate liquid cellulose droplets transitioned from low temperature wetting (500-600 °C) to fully de-wetted, skittering droplets on polished surfaces (>700 °C). Introduction of macroporosity to the heated surface was shown to completely inhibit the cellulose Leidenfrost effect, providing a tunable design parameter to control particle heat transfer rates in industrial biomass reactors.