Mass spectrometric methodology was developed for the determination and manipulation of the primary products of fast pyrolysis of carbohydrates. To determine the true primary pyrolysis products, a very fast heating pyroprobe was coupled to a linear quadrupole ion trap mass spectrometer through a custom-built adaptor. A home-built flow tube that simulates pyrolysis reactor conditions was used to examine the secondary reactions of the primary products. Depending on the experiment, the pyrolysis products were either evaporated and quenched or allowed to react for a period of time. The quenched products were ionized in an atmospheric pressure chemical ionization (APCI) source infused with one of two ionization reagents, chloroform or ammonium hydroxide, to aid in ionization. During APCI in negative ion mode, chloroform produces chloride anions that are known to readily add to carbohydrates with little bias and little to no fragmentation. On the other hand, in positive ion mode APCI, ammonium hydroxide forms ammonium adducts with carbohydrates with little to no fragmentation. The latter method ionizes compounds that are not readily ionized upon negative ion mode APCI, such as furan derivatives. Six model compounds were studied to verify the ability of the ionization methods to ionize known pyrolysis products: glycolaldehyde, hydroxyacetone, furfural, 5-hydroxymethylfurfural, levoglucosan, and cellobiosan. The method was then used to examine fast pyrolysis of cellobiose. The primary fast pyrolysis products were determined to consist of only a handful of compounds that quickly polymerize to form anhydro-oligosaccharides when allowed to react at high temperatures for an extended period of time.
A versatile and portable apparatus was developed to demonstrate exciting visual displays of catalytic phenomena that introduce basic concepts in catalysis, renewable energy, and chemical safety, in order to pique scientific curiosity in a variety of audiences including middle and high school students, undergraduate and graduate students, and the general public. The demonstration uses the platinum-catalyzed oxidation of hydrogen by oxygen as a model reaction to illustrate concepts in thermodynamics, reaction kinetics, and electrochemistry. The apparatus was designed to contain inherent safety features and the versatility to adopt several configurations to perform a wide range of experiments in classroom settings, informal science education activities, and public outreach events. Soap bubbles are used to confine small, controlled volumes (<35 cm3) of hydrogen/oxygen gas mixtures and probe the reactivity of bulk and nanoparticle forms of platinum to illustrate how high metal surface areas increase catalytic reaction rates. In parallel, a hydrogen/oxygen proton-exchange fuel cell is used to demonstrate how chemical energy released from the exergonic hydrogen oxidation reaction can be converted into electricity by using a platinum-containing electrocatalyst. With adjustments of the operating configuration and the experimental conditions of the apparatus, the demonstrations can be tailored toward target demographics of varying scientific proficiency to emphasize specific learning objectives for topics in reaction chemistry and engineering. Potential hazards and important safety precautions are addressed.
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