TY - JOUR
T1 - Monoatomically dispersed Pd/TiO 2 catalyst effective for epoxidation of propylene at ambient temperature in the presence of H 2 and O 2
AU - Hikazudani, Susumu
AU - Mochida, Tatsuya
AU - Matsuo, Naofumi
AU - Nagaoka, Katsutoshi
AU - Ishihara, Tatsumi
AU - Kobayashi, Hisayoshi
AU - Takita, Yusaku
N1 - Funding Information:
We gratefully acknowledge the financial support of Grant-in-Aid on the Nano Environmental Catalyst from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan .
PY - 2012/6
Y1 - 2012/6
N2 - The catalytic activity of monoatomically dispersed Pd supported on TiO 2 toward propylene epoxidation in the presence of H 2 and O 2 was studied at ambient temperature, and both propylene oxide (PO) and propane were obtained. Short-chain alkanes also reacted but epoxide formation was not observed in those reactions except in the case of isobutane, which formed isobutylene oxide at a low rate. The optimum surface concentration of Pd on TiO 2 was 0.005-0.01 atom/nm 2; because the supported amount of Pd is extremely small relative to the surface area of the support, the supported Pd is thought to be monoatomically dispersed. Pd/TiO 2 catalysts prepared from a tetraphenylporphyrin-Pd chloride complex showed almost the same product distribution for propylene epoxidation as did catalysts prepared from Pd(NO 3) 2. Isotope exchange between H 2 and D 2 proceeded over Pd/TiO 2 with a low surface concentration (0.0001 atom-Pd/nm 2), and chemical potential calculations suggested that H 2 molecules could dissociatively adsorb onto the monoatomically dispersed Pd/TiO 2. A PO formation mechanism over the catalyst is proposed on the basis of these results. The results presented here may provide the first clear evidence of catalysis by monoatomically dispersed noble metals.
AB - The catalytic activity of monoatomically dispersed Pd supported on TiO 2 toward propylene epoxidation in the presence of H 2 and O 2 was studied at ambient temperature, and both propylene oxide (PO) and propane were obtained. Short-chain alkanes also reacted but epoxide formation was not observed in those reactions except in the case of isobutane, which formed isobutylene oxide at a low rate. The optimum surface concentration of Pd on TiO 2 was 0.005-0.01 atom/nm 2; because the supported amount of Pd is extremely small relative to the surface area of the support, the supported Pd is thought to be monoatomically dispersed. Pd/TiO 2 catalysts prepared from a tetraphenylporphyrin-Pd chloride complex showed almost the same product distribution for propylene epoxidation as did catalysts prepared from Pd(NO 3) 2. Isotope exchange between H 2 and D 2 proceeded over Pd/TiO 2 with a low surface concentration (0.0001 atom-Pd/nm 2), and chemical potential calculations suggested that H 2 molecules could dissociatively adsorb onto the monoatomically dispersed Pd/TiO 2. A PO formation mechanism over the catalyst is proposed on the basis of these results. The results presented here may provide the first clear evidence of catalysis by monoatomically dispersed noble metals.
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U2 - 10.1016/j.molcata.2012.03.001
DO - 10.1016/j.molcata.2012.03.001
M3 - Article
AN - SCOPUS:84860275441
SN - 1381-1169
VL - 358
SP - 89
EP - 98
JO - Journal of Molecular Catalysis A: Chemical
JF - Journal of Molecular Catalysis A: Chemical
ER -