ACS Catalysis p. 3061 - 3071 (2016)
Update date:2022-08-24
Topics:
Lwin, Soe
Li, Yuanyuan
Frenkel, Anatoly I.
Wachs, Israel E.
Supported WOx/SiO2 catalysts were investigated for propylene metathesis as a function of tungsten oxide loading and temperature. The catalysts were synthesized by incipient-wetness impregnation of an aqueous ammonium metatungstate solution onto the silica support and calcined at elevated temperatures to form the supported tungsten oxide phase. In situ Raman spectroscopy under dehydrated conditions revealed that below 8% WOx/SiO2, only surface WOx sites are present on the silica support: dioxo (O=)2WO2 and mono-oxo O=WO4. The in situ XANES analysis showed that dioxo surface WO4 sites were the dominant surface WOx sites on SiO2 (>90%). The isolated nature of the surface WOx sites was confirmed with in situ UV-vis spectroscopy. The surface WOx sites are activated by exposure to propylene at elevated temperature that removes oxygen from these sites. The activation process produces a highly active surface WOx site that can perform olefin metathesis at 150-250 °C. For 8% WOx/SiO2 and higher tungsten oxide loading, crystalline WO3 nanoparticles (NPs) are also present, and their amount increases with greater tungsten oxide loading. WO3 NPs, however, are not active for propylene metathesis. The acid character of the surface WOx sites (Lewis) and WO3 NPs (Br?nsted) is responsible for formation of undesirable reaction products (C4-C6 alkanes and dimerization of C2= to C4=). This study represents the first time that molecular level structure-activity/selectivity relationships have been established for propylene metathesis by conventionally impregnated supported WOx/SiO2 catalysts.
View MoreShangyu Sanhechemicals Co.,LTD.
Contact:86-0571-56696839
Address:Num.2952,Nanhuan Road,Binjiang District,Hangzhou,China
NingBO Hong Xiang Biochem.Co.Ltd
website:http://www.hxbiochem.com
Contact:0574-66003444
Address:Ning Bo Bei Lun
Fusilin chemical science & technology co., ltd.
Contact:532-80698166/86057573, +86-400-669-7885
Address:School of Material Science & Engineering, Shandong Uinversity of Science & Technology, Huangdao Zone, Qindao, Shandong
Hebei Fulong Import & Export Co., Ltd.
Contact:86-311-87795661
Address:15A19 Zhongyuan Building,368 Youyi North Street,Shijiazhuang 050070,China
Junkai (Tianjin) Chemical Co., Ltd.
website:http://www.junkaichem.com
Contact:86-22-85689515
Address:Room 8-501, Building K2, The Hi-Tech Green Industrial Base, No.6, 6th Road, Hi-Tech Development Road, Tianjin Hi-Tech IndustrialPark, Tianjin, China.
Doi:10.1007/s10562-015-1636-y
(2016)Doi:10.1021/ja307612b
(2012)Doi:10.1021/jo00235a012
(1987)Doi:10.1039/c39870000037
(1987)Doi:10.1039/c7nj04632d
(2018)Doi:10.1021/acs.organomet.5b00551
(2015)