9 xanthydrol

Conventional multipass, low-cob corn stover
was harvested in Hamilton County, IA. Wheat straw was harvested in
Leslie, MI. Rice straw was harvested from Craighead County, AR, and
Butler County, MO. All materials were initially stored in large square
bales before being chopped to ∼2.5 cm particle size using a
Vermeer BG 480 grinder. Chopped biomass was stored in plastic-lined
supersacks at <10% moisture prior to use. AFEX treatment in a packed
bed reactor was performed using the method described by Sarks et al.^{17 (link)} After treatment, the biomass was pelletized
using a Buskirk PM810 flat die pelletizer and stored at room temperature
and <10% moisture. For comparison, AFEX treatment was also performed
in a Parr reactor using the method described by Hanchar et al.^{18 (link)}Acetamide (99%, CAS no. 60-35-5), d₃-Acetamide (D + 99%, CAS no. 23724-60-9), propionamide
(97%, CAS no. 79-05-0), 9-xanthydrol (98%, CAS no. 90-46-0), and methanol
were purchased from Sigma-Aldrich (St. Louis, MO, USA). Ethyl acetate
and hexane were purchased from Fisher Chemicals. Water was prepared
using a Millipore Milli-Q purification system, and hydrochloric acid
was purchased from EMD Millipore.

Acetamide, d₃-Acetamide, propionamide, 9-xanthydrol, and methanol
were purchased from Sigma-Aldrich (St. Louis, MO). Ethyl acetate and
hexane were purchased from Fisher Chemicals (Fair Lawn, NJ). Sodium
chloride and acetone were purchased from Macron Fine Chemicals (Center
Valley, PA). Acetone was confirmed by GC/MS to be free of detectable
Acetamide.
Water was prepared using a Millipore Milli-Q purification
system, and hydrochloric acid was purchased from EMD Millipore (Burlington,
MA).
HCl solution (0.5 M) was prepared in methanol by adding
8.25 mL
of HCl stock solution (12.1 M) to 191.75 mL methanol in a 200 mL volumetric
flask. KOH solution (0.7 M) was prepared by dissolving 0.39 g of KOH
in 10 mL water. 9-xanthydrol solution (5%) was prepared by dissolving
2.5 g of 9-xanthydrol in 50 mL of methanol. Stock solutions of Acetamide,
propionamide, and d₃-Acetamide were prepared
in methanol at 1 g/L by dissolving 10 mg of the chemicals in 10 mL
of methanol. Working solutions (10, 50, and 100 ppm) of each chemical
were prepared by dilution of 1 g/L stock solution accordingly.