US EPA

7733010 

Journal Article 

Towards inhibition of yellowing of mechanical pulps .1. Catalytic hydrogenation of lignin model compounds under mild conditions 

Hu, TQ; James, BR; Lee, CL 

1997 

Yes 

Journal of Pulp & Paper Science
ISSN: 0826-6220 

23 

4 

J153-J156 

English 

WOS:A1997WU94700002 

Di-μ-chloro-bis(η4-1, 5-hexadiene)-dirhodium(I) effectively catalyzed the hydrogenation of the aromatic rings of the lignin model compounds 4-propylphenol, eugenol, 1,2-dimethoxy-4-propylbenzene and 2,6-dimethoxy-4-propyl-phenol under extremely mild conditions (25°C, 1 Mm H2) in a two-phase, hexane/aqueous pH 7.5 medium. This catalyst was more active than di-μ-chloro-bis (η4-1,5-cyclooctadiene)-dirhodium(I), rhodium(III) trichloride trihydrate and ruthenium(III) trichloride trihydrate. The reactivity of three predominant functional groups in lignin toward the rhodium(I) catalyzed hydrogenation followed the descending order of carbon-carbon double bond > aromatic ring > carbonyl group. The hydrogenation reactions were sensitive to steric and electronic effects of the substituent(s) on the aromatic rings. Moderate to extremely high diastereoselectivities were observed for the hydrogenated products. 

inhibition; yellowing; mechanical pulps; hydrogenation; catalysts; lignin model compounds; aromatic groups; carbonyl groups; chromophores; eugenol; hydrogenolysis; quinones