No abstract

Pt supported on HY zeolite is successfully used as a bifunctional catalyst for phenol hydrodeoxygenation in a fixed-bed configuration at elevated hydrogen pressures, leading to hydrogenation-hydrogenolysis ring-coupling reactions producing hydrocarbons, some with enhanced molecular weight.

The reactivity of monosaccharides, furfural, and 5-hydroxymethyl-2-furfural (HMF) in the presence of a Brønsted acid (added as H(2)SO(4)) in the ionic liquid 1-butyl-3-methylimidazolium chloride (BMImCl) is investigated at 120 °C. Fructose is converted much faster than mannose, glucose, and xylose and yields HMF with high selectivity, even in the absence of acid. Conversion of mannose, glucose, and xylose involves more complex reaction networks. Only small amounts of furfural and HMF are converted in the absence of other reactants but both compounds are consumed when monosaccharides and their degradation products are present. Acid-catalyzed degradation reactions also lead to the formation of solid residues (humins).

Organosolv switchgrass lignin is depolymerized and hydrodeoxygenated with a formic acid hydrogen source, 20 wt % Pt/C catalyst, and ethanol solvent. The combination of formic acid and Pt/C is found to promote production of higher fractions of lower molecular weight compounds in the liquid products. After 4 h of reaction, all of the switchgrass lignin is solubilized and 21 wt % of the biomass is shown to be converted into seven prominent molecular species that are identified and quantified. Reaction time is shown to be an important variable in affecting changes in product distributions and bulk liquid product properties. At 20 h of reaction, the lignin is significantly depolymerized to form liquid products with a 76 % reduction in the weighted average molecular weight. Elemental analysis also shows that the resultant liquid products have a 50 % reduction in O/C and 10 % increase in H/C molar ratios compared to the switchgrass lignin after 20 h.

A comprehensive study of the acid hydrolysis of the softwood species, Loblolly pine (Pinus taeda), using different hydrolysis conditions is presented. The effect of the type of acid, pH, reaction temperature, and reaction time on hydrolysis products such as monosaccharides (mannose, glucose, galactose, xylose, and arabinose) and the subsequent degradation products, 5-hydroxymethyl-2-furaldehyde (HMF) and 2-furaldehyde (furfural) is reported using a batch reactor. Trifluoroacetic acid (TFA) is found to yield the highest amount of overall soluble monosaccharides (∼70% yield from the hemicelluloses fraction) at 150 °C at pH 1.65. The mineral acids (HCl, H2SO4, HNO3, and H3PO4) gave a slightly lower yield of monosaccharides from hydrolyzed hemicellulose (∼60%). At 200 °C, cellulose is hydrolyzed by the mineral acids as evidenced by higher levels of solid dissolution and higher soluble hexose (relative to pentose) yields. Larger amounts of degradation products are also noted at higher temperatures. Furthermore, an increased amount of HMF and furfural is noted in the liquid product as compared to lower temperatures. TFA was found to be the most “gentle” acid, leading to limited monosaccharide degradation among the acids used. The presence of soluble oligosaccharides in solution after hydrolysis was confirmed by applying a secondary acid hydrolysis to the solid-free liquid hydrolysate. Good closure of mass balances was possible using total organic carbon (TOC) analysis.