Effects of reaction conditions on catalytic hydroconversion of phenethoxybenzene over bifunctional Ni/Hβ

Abstract

An active Ni/Hβ catalyst was successfully prepared by decomposing nickel carbonyl to dispersed metallic Ni onto Hβ support. Phenethoxybenzene (POB) was used as a lignin model compound to evaluate the catalytic activity. The effects of reaction temperature, initial H2 pressure (IHP), and reaction time on the catalytic hydroconversion (CHC) of POB was studied. The results show that Ni/Hβ effectively catalyzed POB convert to monocyclic cyclanes via direct hydrogenation of benzene ring (BR) in POB, the cleavage of C‐O bridged bond induced by H+ addition, dehydration, and H− abstraction under higher IHPs. Alternatively, the CHC of POB proceeds preferentially via direct cleavage of C–O bridged bond induced by H+ addition, followed by BR hydrogenation, dehydration, and H− abstraction under lower IHP. Bicyclic cyclanes were produced via rearrangement reactions, which proceed more easily either at higher temperatures or under lower IHPs.

The Role of Metal and Acid Sites in the Liquid‐phase Hydrodeoxygenation of Lignin‐derived Phenolic Dimers

“…A similar trend was also observed for the conversion of PEB over Ru/SO 4 -ZrO 2 (SZ) [75] (8 bar H 2 , water) and Ni/Hβ [77] (40 bar H 2 , n-hexane). At low temperatures (< 180 °C), hydrogenolysis and hydrogenation reactions co-existed, whereas the hydrogenolysis of the C aliph -O bond occurred as the main pathway at high temperatures (> 200 °C).…”

“…The effect of hydrogen pressure on the conversion of PEB was studied by Zhou et al [77] over 20 wt.% Ni/Hβ, at 220 °C in nhexane. Under 10 bar of H 2 , 16 % of PEB was mainly converted into 2-phenethylphenol (42.8 %), ethylbenzene (26.2 %), phenol (14.4 %), and cyclohexane (10.3 %).…”

“…Nickel supported on zeolite β (20 wt.% Ni) was used to study the conversion of PEB at 220 °C, under 40 bar H 2 in nhexane. [77] Over bare Hβ, 11 % of PEB was converted into phenol (36 %), 2-phenethylphenol (2-PEP; 38 %), and 4-phenethylphenol (4-PEP; 20 %). First, PEB was cleaved to produce 2-phenyleth-1ylium and phenol intermediates.…”

“…The effect of hydrogen pressure on the conversion of PEB was studied by Zhou et al [77] . over 20 wt.% Ni/Hβ, at 220 °C in n ‐hexane.…”

“…The first category of model molecules consists of phenolic monomers such as guaiacol, [29–34] anisole, [35–40] cresol, [41–46] and phenol [47–54] that contain hydroxyl and/or methoxy groups attached to the aromatic ring. But dimeric aryl ethers such as benzyl phenyl ether (BPE), [55–69] 4‐(benzyloxy) phenol (4‐BOP), [52,63,69–72] phenethoxybenzene (PEB), [56,57,61,70,73–77] 2‐phenoxy‐1‐phenylethanol (PP), [64,78–84] and diphenyl ether (DPE), [56,57,62,63,70,85–89,89–100] are more representative of the α‐O‐4, β‐O‐4, and 4‐O‐5 ether linkages of lignin structure (Figure 2). According to Yanding et al., [101] the cleavage of diaryl ether plays a key role in the reduction of the molecular weight of lignin, which could contribute to the high yields of monomers obtained in the RCF process.…”