title: Enhancement in the catalytic activity of Pd/USY in the heck reaction induced by H2 bubbling.
abstract: Pd was loaded on ultra stable Y (USY) zeolites prepared by steaming NH(4)-Y zeolite under different conditions. Heck reactions were carried out over the prepared Pd/USY. We found that H₂ bubbling was effective in improving not only the catalytic activity of Pd/USY, but also that of other supported Pd catalysts and Pd(OAc)₂. Moreover, the catalytic activity of Pd/USY could be optimized by choosing appropriate steaming conditions for the preparation of the USY zeolites; Pd loaded on USY prepared at 873 K with 100% H₂O gave the highest activity (TOF = 61,000 h⁻¹), which was higher than that of Pd loaded on other kinds of supports. The prepared Pd/USY catalysts were applicable to the Heck reactions using various kinds of substrates including bromo- and chloro-substituted aromatic and heteroaromatic compounds. Characterization of the acid properties of the USY zeolites revealed that the strong acid site (OH(strong)) generated as a result of steaming had a profound effect on the catalytic activity of Pd.
authors.affiliation: Department of Chemistry and Biotechnology, Tottori University, 4-101 Koyama-cho Minami, Tottori, Japan. okmr@chem.tottori-u.ac.jp
authors.forename: Kazu
authors.initials: K
authors.lastname: Okumura
authors.forename: Takuya
authors.initials: T
authors.lastname: Tomiyama
authors.forename: Sayaka
authors.initials: S
authors.lastname: Moriyama
authors.forename: Ayaka
authors.initials: A
authors.lastname: Nakamichi
authors.forename: Miki
authors.initials: M
authors.lastname: Niwa
mesh_terms: D002384:Catalysis; D005583:Fourier Analysis; D006859:Hydrogen / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010165:Palladium / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D014961:X-Ray Diffraction; D017641:Zeolites / Q000737:chemistry*
chemical_list: D017641:Zeolites; D010165:Palladium; D006859:Hydrogen