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Atom‐economy Synthesis of N ‐Substituted Carbamate from Urea Derivative and Dimethyl Carbonate Catalyzed by La/SiO 2 : Characterization and Activity
Author(s) -
Guo Xiaoguang,
Shang Jianpeng,
Li Jian,
Wang Liguo,
Ma Yubo,
Shi Feng,
Deng Youquan
Publication year - 2010
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201090048
Subject(s) - chemistry , catalysis , lanthanum , dimethyl carbonate , atom economy , inorganic chemistry , bet theory , x ray photoelectron spectroscopy , urea , nuclear chemistry , organic chemistry , chemical engineering , engineering
A series of silica gel immobilized lanthanum catalysts were prepared for the atom‐economy synthesis of N ‐substituted carbamates from urea derivatives and dimethyl carbonate. The La/SiO 2 catalysts with lanthanum loadings varied from 1.3 wt% to 8.5 wt% were characterized by AES, BET, XRD, TEM, FT‐IR, XPS and TPD. According to the characterization, lanthanum species with particle sizes of 5–10 nm on the surface of silica gel were formed. The catalysts were all amorphous and the surface areas were 336.5–530.2 m 2 /g. NH 3 ‐TPD analysis showed that all samples exhibited similar acid strength with different acid amounts. FT‐IR measurement indicated that the component of lanthanum species on the catalyst surface were La(OH) 3 , LaOOH and hydrated La 2 O 3 . Also, the peak value of the absolute amount of LaOOH was obtained with 4.3 wt% lanthanum loading. The BET surface area decreased dramatically when the lanthanum loading was above 4.3 wt%. In consideration of the results obtained from the catalytic reactions, it could be concluded that LaOOH was the possible active species and high surface area was important for the high catalytic activity.