Palladium-doped hierarchical ZSM-5 for catalytic selective oxidation of allylic and benzylic alcohols.
Shengzhe DingMuhammad GaneshYilai JiaoXiaoxia OuMark A IsaacsMark S'ariAntonio Torres LopezXiaolei FanChristopher M A ParlettPublished in: Royal Society open science (2021)
Hierarchical zeolites have the potential to provide a breakthrough in transport limitation, which hinders pristine microporous zeolites and thus may broaden their range of applications. We have explored the use of Pd-doped hierarchical ZSM-5 zeolites for aerobic selective oxidation (selox) of cinnamyl alcohol and benzyl alcohol to their corresponding aldehydes. Hierarchical ZSM-5 with differing acidity (H-form and Na-form) were employed and compared with two microporous ZSM-5 equivalents. Characterization of the four catalysts by X-ray diffraction, nitrogen porosimetry, NH3 temperature-programmed desorption, CO chemisorption, high-resolution scanning transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy allowed investigation of their porosity, acidity, as well as Pd active sites. The incorporation of complementary mesoporosity, within the hierarchical zeolites, enhances both active site dispersion and PdO active site generation. Likewise, alcohol conversion was also improved with the presence of secondary mesoporosity, while strong Brønsted acidity, present solely within the H-form systems, negatively impacted overall selectivity through undesirable self-etherification. Therefore, tuning support porosity and acidity alongside active site dispersion is paramount for optimal aldehyde production.
Keyphrases
- electron microscopy
- high resolution
- quantum dots
- highly efficient
- mass spectrometry
- hydrogen peroxide
- alcohol consumption
- magnetic resonance imaging
- dual energy
- metal organic framework
- high speed
- visible light
- computed tomography
- magnetic resonance
- tandem mass spectrometry
- climate change
- contrast enhanced
- walled carbon nanotubes