Cleavage of Organosolv Lignin to Phenols Using Nitrogen Monoxide and Hydrazine

Abstract

From the variety of methods known for the depolymerization of organosolv lignin, a broad range of diversely substituted aromatic compounds are available today. In the present work, a novel two-step reaction sequence is reported, which is focused on the formation of phenols. While the first step of the depolymerization strategy comprises the 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-catalyzed oxidation of organosolv lignin with nitrogen monoxide so that two waste materials are combined, cleavage to the phenolic target compounds is achieved in the second step employing hydrazine and potassium hydroxide under Wolff–Kishner-type conditions. Besides the fact that the novel strategy proceeds via an untypical form of oxidized organosolv lignin, the two-step sequence is further able to provide phenols as cleavage products, which bear no substituent at the 4-position.

Boosting the catalytic performance of Ru nanoparticles in the cleavage of β-O-4 linkages in lignin by doping Mo

“…After 2 h reaction, the solid product was separated through centrifugation and washed alternately with ethanol and water. According to the ingredient Ru to Mo ratios, 20 : 1, 10 : 1, 5 : 1, 3 : 1, 1 : 1, 1 : 3, 1 : 5, 1 : 10, and 1 : 20, the as-obtained composites are named RuMo/rGO(20-1), RuMo/rGO(10-1), RuMo/rGO(5-1), RuMo/rGO(3-1), RuMo/rGO(1-1), RuMo/rGO(1-3), RuMo/rGO(1-5), RuMo/rGO(1-10), and RuMo/rGO (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), respectively. For comparison, monometallic composites Ru/rGO and Mo/rGO were also prepared under the same conditions.…”

“…[12][13][14] For instance, a two-step catalytic reaction system with VOSO 4 /(6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and Cu/1,10-phenanthroline for α-OH oxidation and C α -C β cleavage of the β-O-4 linkage, respectively, was reported by Wang et al 15 Hofmann and co-workers used 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)/NO and hydrazine as two catalysts, and 6.9% of total depolymerization yield of organosolv lignin was obtained. 16 Bosque et al developed a redox and photocatalytic system using N-hydroxyphthalimide (NHPI)/lutidine as the catalyst for α-OH oxidation and [Ir (ppy) 2 (dtbbpy)](PF 6 ) as the photocatalyst for β-O-4 cleavage. 17 Meanwhile, there have been a few catalysts and catalytic reaction systems developed for the oxidative cleavage of the β-O-4 linkage in lignin or lignin model compounds through one-pot reactions.…”