High Conversion of Concentrated Sugars to 5-Hydroxymethylfurfural over a Metal-free Carbon Catalyst: Role of Glucose-Fructose Dimers.

To reduce the production cost of chemicals from renewable resources, the feedstock loading must be high and the catalyst must be of low cost and efficient. In this study, at a very short reaction time of 10 min at 125 °C, concentrated sugar solutions (20 wt %, 101 wt % on solvent) were converted to 5-hydroxymethylfurfural (HMF) over a cotton gin trash (CGT)-derived sulfonated carbon catalyst in a 1-butyl-3-methyl-imidazolium chloride ([BMIM]Cl) and 2-methyltetrahydrofuran (MeTHF) biphasic system. We report, for the first time, that the presence of glucose either as a covalently bonded monomer in sucrose or in a mixture with fructose achieved yields of HMF up to 62 mol % compared to a value of only 39 mol % obtained with fructose on its own.

Effect of HCOOK/Ethanol on Fe/HUSY, Ni/HUSY, and Ni-Fe/HUSY Catalysts on Lignin Depolymerization to Benzyl Alcohols and Bioaromatics.

We have investigated the production of benzyl alcohols and bioaromatics via the reductive lignin depolymerization process over Fe/H-style ultrastable Y (HUSY), Ni/HUSY, and Ni-Fe/HUSY catalysts using HCOOK/ETOH in air. Synergy effect between HCOOK and the catalysts improved the depolymerization process, resulting in a higher bio-oil recovery. HCOOK does not act solely as an in situ hydrogen source; it also interacts with lignin to enable its initial depolymerization via a base-catalyzed mechanism to low-molecular-weight fragments, and in tandem with the catalyst, the hydrogenolysis rate of the depolymerized lignin monomers was enhanced.

Electrospray mass spectrometry of stable iminyl nitroxide and nitronyl nitroxide free radicals.

Electrospray ionization (ESI) mass spectra have been recorded for a range of substituted nitronyl nitroxide and iminyl nitroxide monoradicals and biradicals. Secondary species formed in the ESI source were observed as the dominant ions in both the iminyl nitroxide and nitronyl nitroxide spectra. Daughter ion spectrometry was used to establish fragmentation mechanisms for the nitronyl nitroxide and iminyl nitroxide moieties as well as the secondary species under ESI conditions.