2 5 dimethyltetrahydrofuran

Nitric acid (70–71%, Aencore Chemical Co., LTD.), Urea for electrophoresis (99%, Sigma-Aldrich), i-propanol (HPLC grade, J.T. Baker), 5-hydroxymethylfurfural; 5-HMF (98%, AK scientific), 2,5-Bis (hydroxymethyl)furan; BHMF (98%, AK scientific); 2,5-dimethylfuran; 2,5-DMF (99%, Acros); 2,5-Dimethyltetrahydrofuran; DMTHF (mixture of cis- and trans-, 96%, Sigma-Aldrich); 5-Methylfurfural (5-MF, 99%, Sigma-Aldrich), 5-Methyl-2-furanmEthanol; MFA (97%, Acros), Ruthenium chloride n-Hydrate (39% metal content, UniRegion Bio-Tech), Hydrogen fluoride (HF, 48% Sigma-Aldrich), Hydrochloric acid ( ≥ 37%, Honeywell Fluka), Ethanol (99.9%, Honeywell Riedel-de-Haën), Aluminum (III) Chloride (98%, Sigma-Aldrich), Poly (ethylene glycol)-b-poly (propylene glycol)-b-poly (ethylene glycol), Pluronic P123 (Sigma-Aldrich), Furfuryl alcohol; FUL (98%, Acros Organics), Tetraethyl silicate (98%, Sigma-Aldrich), Ammonium hydroxide (28–30%, JT Baker Chemicals), Cetyltrimethylammonium bromide (98%, Alfa Aesar), Pluronic F-127(Sigma-Aldrich). Unless otherwise stated, all chemicals were used as received without further purification.

The flavor standards, methanethiol (97 %), eucalyptol (99 %), 2,5-dimethyltetrahydrofuran (98 %), 2,5-dimethylpyrazine (98 %), hexanal (98 %), 2-ethyl-5-methylpyrazine (96 %), (E)-2-octenal (97 %), 3-ethyl-2,5-dimethylpyrazine (98 %), benzaldehyde (99.5 %), (Z)-2-octen-1-ol (97 %), 2-pentylfuran (98 %), carvone (96 %), methyleugenol (98 %), anethole (99 %), (E, E)-2,4-decadienal (97 %), 2,3,5-trimethylpyrazine (99 %), (Z)-3-phenylacrylaldehyde (97 %), p-cresol (99 %), 4-hydroxy-5-methyl-3(2H)-furanone (97 %), 2,3-dimethyl-5-ethylpyrazine (99 %), dimethyl trisulfide (98 %), 2(5H)-furanone (98 %), 1-octen-3-ol (98 %), 3-furaldehyde (97 %), and 2-furanmethanol (98 %) were commercially purchased from Sigma-Aldrich (Shanghai, China). And methyl pyrazine (98 %) and benzene acetaldehyde (98 %) were purchased from TCI (Shanghai, China). Meanwhile, 2-methyl-3-heptanone (99 %) from Dr. Ehrenstorfer (Beijing, China) as the internal standard and the n-alkanes external standard (C7-C40, ≥ 97 %) from o2si Smart Solutions (Shanghai, China) were purchased.

5‐Hydroxymethylfurfural (95 %) was supplied by AVA Biochem. 2,5‐Bis(hydroxymethyl)furan (95 %) and 2,5‐bis(hydroxymethyl)tetrahydrofuran (95 %) were provided by AKos GmbH. 5 wt%Ru/C, ethanol (96 %), toluene (>99 %), and 2,5‐dimethyltetrahydrofuran (96 %) were purchased from Sigma‐Aldrich. Amberlyst‐70 and Amberlyst‐15 were provided by Rohm and Haas. Aquivion P87S was obtained by Solvay Specialty Polymers. Two commercial zeolites HZSM‐5 having Si/Al equal to 15 and 25 (Zeocat PZ‐2/25H and Zeocat PZ‐2/50H) were purchased from ZeoChem AG. The catalysts were dried at 90 °C under reduced pressure for 3 h before their employment. Since all the employed acid catalysts are commercial, their characteristics are reported in the literature and summarized in Table 8.