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Epoxidation of cyclohexene with H 2 O 2 over efficient water‐tolerant heterogeneous catalysts composed of mono‐substituted phosphotungstic acid on co‐functionalized SBA‐15
Author(s) -
Jin Manman,
Niu Qingtao,
Guo Zhenmei,
Lv Zhiguo
Publication year - 2019
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.5115
Subject(s) - cyclohexene , phosphotungstic acid , chemistry , catalysis , selectivity , lewis acids and bases , cyclohexene oxide , mesoporous material , transition metal , inorganic chemistry , nuclear chemistry , organic chemistry
A series of Keggin‐type heteropolyacid‐based heterogeneous catalysts (Co‐/Fe‐/Cu‐POM‐octyl‐NH 3 ‐SBA‐15) were synthesized via immobilized transition metal mono‐ substituted phosphotungstic acids (Co‐/Fe‐/Cu‐POM) on octyl‐amino‐co‐functionalized mesoporous silica SBA‐15 (octyl‐NH 2 ‐SBA‐15). Characterization results indicated that Co‐/Fe‐/Cu‐POM units were highly dispersed in mesochannels of SBA‐15, and both types of Brønsted and Lewis acid sites existed in Co‐/Fe‐/Cu‐POM‐octyl‐NH 3 ‐SBA‐15 catalysts. Co‐POM‐octyl‐NH 3 ‐SBA‐15 catalyst showed excellent catalytic performance in H 2 O 2 ‐mediated cyclohexene epoxidation with 83.8% of cyclohexene conversion, 92.8% of cyclohexene oxide selectivity, and 98/2 of epoxidation/allylic oxidation selectivity. The order of catalytic activity was Co‐POM‐octyl‐NH 3 ‐SBA‐15 > Fe‐POM‐octyl‐NH 3 ‐SBA‐15 > Cu‐POM‐octyl‐NH 3 ‐SBA‐15. In order to obtain insights into the role of ‐octyl moieties during catalysis, an octyl‐free catalyst (Co‐POM‐NH 3 ‐SBA‐15) was also synthesized. In comparison with Co‐POM‐NH 3 ‐SBA‐15, Co‐POM‐octyl‐NH 3 ‐SBA‐15 showed enhanced catalytic properties (viz. activity and selectivity) in cyclohexene epoxidation. Strong chemical bonding between ‐NH 3 + anchored on the surface of SBA‐15 and heteropolyanions resulted in excellent stability of Co‐POM‐octyl‐NH 3 ‐SBA‐15 catalyst, and it could be reused six times without considerable loss of activity.