Selective Hydrogenation of Phenol to Cyclohexanone over a Highly Stable Core-Shell Catalyst with Pd-Lewis Acid Sites

Abstract

Cyclohexanone is widely used in coatings, pesticides, dyes, lubricants, and other industries due to its high solubility and low volatility, but designing highly active and stable heterogeneous catalysts for selective hydrogenation of phenol to cyclohexanone is a still challenge. In this paper, core-shell structure Pd@Al-mSiO 2 catalysts containing a Pd metal core and an Almodified mesoporous silica shell were design for hydrogenation of phenol to cyclohexanone. At 1 MPa, 1 h, and 100 °C, cyclohexanone with 98.5% of selectivity and 100% of phenol conversion was achieved over Pd@Al-mSiO 2 catalysts with trace aluminum modification. Pd cubes with (100) facets, as the hydrogenation active core, had higher cyclohexanone selectivity than nanoparticles with (111) facets, while mesoporous shells with abundant Lewis acid sites played an important role in activating aromatic rings and inhibiting carbonyl hydrogenation, and close metal−acid interfaces further enhance the synergy between multiple active sites. Moreover, owing to the protection of the shell, the catalyst could be repetitively used 5 times without any loss of catalytic activity.

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

“…In addition, the crystal face of metals also affects product selectivity. As reported by Liu et al , 70 the (100) plane existed on the palladium nanoparticles in Pd@Al–mSiO 2 . The total energy of hydrogenation of CHONE on the (100) face was higher than the desorption energy, thus CHONE was more inclined to desorb rather than continue hydrogenation.…”

Al-Doped Core–Shell-Structured Ni@Mesoporous Silica for Highly Selective Hydrodeoxygenation of Lignin-Derived Aldehydes

“…As shown in Figure a, the strong peaks at 1446 and 1608 cm –1 for all of the catalysts are attributed to the Lewis acid-bound pyridine. The intensity of the above peaks decreased significantly after desorption under 350 °C (Figure c), suggesting that Lewis acid sites were mainly present as weak acids . The bands at 1595 cm –1 were ascribed to hydrogen-bonded pyridine and disappeared at 200 °C (Figure b).…”

“…The intensity of the above peaks decreased significantly after desorption under 350 °C (Figure 7c), suggesting that Lewis acid sites were mainly present as weak acids. 40 The bands at 1595 cm −1 were ascribed to hydrogenbonded pyridine and disappeared at 200 °C (Figure 7b). Accordingly, the bands that appear at 1489 cm −1 were attributed to the adsorption of pyridine on both Lewis and Brønsted acid sites.…”

Facile self-propagated carbonization synthesis of phosphorus-doped carbon-based catalysts for partial oxidation and hydrogenation

“…This is because the Lewis acid provided by Zr promoted the reaction. 34 For comparison, Pd/C and PdZr/C prepared by conventional calcination were also investigated. The conversion of phenol over Pd/C was less than 40% and no activity enhancement is observed over PdZr/C.…”