Enhanced Catalytic Performances for Guaiacol Aqueous Phase Hydrogenation over Ruthenium Supported on Mesoporous TiO₂ Hollow Spheres Embedded with SiO₂ Nanoparticles

Abstract

The catalytic hydrogenation of lignin‐derived phenolic compounds with high catalytic activity and yield is important for the efficient utilization of lignin derivatives. In this study, a series of mesoporous TiO2 sphere‐supported Ru catalysts were prepared, characterized, and used for hydrogenating guaiacol in aqueous solutions. Both the 100% conversion and 84.2% cyclohexanol yield were achieved using Ru supported on mesoporous TiO2 hollow spheres embedded with SiO2 nanoparticles (Ru‐TiO2‐eSiO2) catalyst under 1.5 MPa H2 at 160 °C for 100 min. Catalyst characterization indicated that the outstanding catalytic performance of the Ru‐TiO2‐eSiO2 is mainly due to its unique spherical structure and acidic properties. The TiO2 shell is polyporous with numerous 3.8 nm mesopores that favor mass transfer efficiency in the reaction process. Moreover, the moderate acidic sites of the catalyst promoted the removal of the –OCH3 group from guaiacol and improve cyclohexanol yield. The catalyst exhibited good water resistance and its catalytic activity presented no obvious loss after recycling for 5 times.

Advances in porous and nanoscale catalysts for viable biomass conversion

“…At optimized reaction conditions, 91.6% and 86.9% yields of cyclohexanol and alkyl cyclohexanols were obtained from guaiacol and alkyl phenols, respectively (entry 13, Table 2). Han et al 404 demonstrated the influence of shape-controlled TiO 2 spheres in guaiacol hydrogenation. Promising results were obtained in terms of guaiacol conversion (100%) and cyclohexanol yield (84.2%) over Ru supported on mesoporous TiO 2 hollow spheres embedded within SiO 2 NPs.…”

Recent Catalytic Approaches for the Production of Cycloalkane Intermediates from Lignin‐Based Aromatic Compounds: A Review

“…), zeolites (preferably H‐from of β, Y, ZSM‐5), mesoporous materials (SBA‐15/16, MCM‐41, MCM‐36, MCM‐48, and mesoporous carbon), metal oxides (SiO 2 , Al 2 O 3 , TiO 2 , MgO, CeO 2, ZrO 2 ), mixed metal oxides and hydroxides (SiO 2 −Al 2 O 3, ZrO 2 −SiO 2 , ZrO 2 −La(OH) 3 ) were reported for this conversion [40,56,57,59,60] . Ni and Ru based catalysts supported on moderate acidic and basic catalytic supports reported for hydrogenation‐hydrodemethoxylation of methoxyphenols to obtain high yields of cyclohexanols [61–63] . Pd metal on nitrogen‐containing supports such as mesoporous graphitic carbon nitride (Mpg‐C 3 N 4 ), polyaniline‐functionalized carbon‐nanofiber, carbon nitride, and N‐doped mesoporous carbon nanorods were employed for the conversion of phenolic compounds to cyclohexanone.…”

“…The combined Ru support (TiO 2 −eSiO 2 ) showed excess catalytic activity as compared to Ru on independent supports (either TiO 2 or SiO 2 ), which could be because of mesoporosity and acidity of TiO 2 −eSiO 2 . The catalyst indicate good catalytic activity for guaiacol and vanillin to generate cyclohexanol and 4‐methylcyclohexanol selectively with 91 and 90 % yields [63] …”

Integrated design of an amination process of lignin oxygenated model compounds to synthesize cyclohexylamine: catalyst nanostructure engineering and catalytic conditional strategy

“…When the metal loading of Pd/γ-Al 2 O 3 was 2.0 wt%, 4-ethylcyclohexanol was obtained in high yield possibly attributable to the surface Pd 0 species (93.6%). 68 Similarly, Wang et al 69 pointed out that the presence of metallic Ru nanoparticles on the surface of TiO 2 -eSiO 2 after H 2 reduction helped to improve the selectivity of CHOL, and the yield of CHOL increased from 83.8% to 85.9%. In addition, the crystal face of metals also affects product selectivity.…”

“…86 In particular, mesoporous materials show great potential in liquid-phase hydrogenation reactions. Wang et al 69 constructed catalysts with hollow mesoporous structures, which can excellently improve the mass transfer efficiency during the reaction process, thereby improving the catalytic hydrogenation efficiency. CHOL was obtained with only 75.2% and 78.1% yield when catalyzed by Ru-SiO 2 and Ru-TiO 2 , respectively.…”