论文题目：Facile Preparation of Methyl Phenols from Ethanol over Lamellar Ce(OH)SO4·xH2O

论文作者：Jinqiu Guo, Zongjing Feng, Jun Xu, Jie Zhu, Guanghui Zhang, Yaping Du*, Hongbo Zhang, Chunhua Yan

发表期刊：ACS Catalysis, 11(10), 6162-6174, 2021   

Abstract： 

Ethanol transformation with high product selectivity is a great  challenge, especially for high weight molecules. Here, we show a  combination study of kinetic, thermodynamic, and in situ spectroscopy  measurements to probe the selective upgrading of ethanol over lamellar  Ce(OH)SO4 center dot xH(2)O catalysts, with 60-70% Ce3+ preserved during  the catalysis. High methyl phenols (MPs) selectivity at similar to 80%  within condensation products was achieved at similar to 50% condensation  yield (3.0 kPa C2H5OH, 15 kPa H-2, Ar balanced, 693 K, 1 atm, gas  hourly space velocity (GHSV) similar to 5.4 min(-1)), with acetaldehyde,  acetone, 4-heptanone, and 2-pentanone as the key reaction  intermediates. Kinetic measurements with the assistance of isotope  labeling proved that MPs generated from the kinetically relevant step  (KRS) of C-C bond coupling of enolate nucleophilically attacks surface  C2H4O following a Langmuir-Hinshelwood model. Low ethanol and water  pressures and high acetaldehyde and hydrogen pressures were proved to be  favored for MPs generation rather than dehydration, in which hydrogen  could reduce the amount of lattice oxygen and facilitate the preparation  of MPs while water and ethanol both compete with acetaldehyde for  active sites during catalysis. On the basis of in situ X-ray diffraction  (XRD), quasi-in situ X-ray photoelectron spectroscopy (XPS), and Raman  characterizations, the Ce(OH)SO4 crystal structure was proved to be  maintained along with ethanol activation, and the Ce3+-OH Lewis  acid-base pair was proved to be the active species for the selective C-C  bond coupling. The KRS assumption was also supported by the apparent  activation energy assessment within the reaction network on dehydration,  dehydrogenation, aldol condensation, and cyclization and a series of  negligible kinetic isotope effects (KIEs). This system can be easily  extended to some other systems related to C-C bond coupling and is  attracting attention on converting oxygenate platform molecules over  lanthanide species.