WANG Qingyin et al. / Chinese Journal of Catalysis, 2013, 34: 548–558
perior catalytic activities in the thermal decomposition of car‐
100
80
60
40
20
0
bamic esters. An MDPC conversion of 99.8% and MDI selectivi‐
ty of 86.2% were achieved. Although the MDI selectivity
achieved using a solvent‐free method is slightly lower than that
using a solvent, the preparation of MDI by catalytic thermal
decomposition of MDPC under solvent‐free conditions avoids
the use of large amounts of high‐boiling‐point solvents. More‐
over, the process is much simpler, which is more favorable for
purifying MDI. Industrialization of MDI using a non‐phosgene
process can be achieved by developing catalysts with improved
activities and enhanced MDI selectivities.
(1)
(2)
(3)
0.00
0.25
0.50
0.75
1.00
1.25
1.50
References
Catalyst amount (%)
Fig. 12. Effect of catalyst amount on MDPC pyrolysis. Reaction condi‐
tions: 12 min, 0.6 kPa, 220 °C. (1) MDPC conversion; (2) MDI selectivity;
(3) MPI selectivity.
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composition. MDPC conversion remains almost constant with
increasing reaction time, whereas the MDI selectivity reached
its highest value (64.4%) at 12 min. Increasing the reaction
time promotes decomposition of MPI to MDI. The –NCO group
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3.4.4. Effect of catalyst amount on thermal decomposition of
MDPC
Figure 12 shows the effect of catalyst amount on MDPC de‐
composition. The maximum values of MDPC conversion and
MDI selectivity are both obtained at a catalyst amount of 0.06%
(wt%) of the total amount of raw materials. The MDI selectivity
is 86.2% and the MDPC conversion is 99.8%. The drop in MDI
selectivity with increasing catalyst amount may be attributed to
accelerated thermal decomposition and polymerization of MDI
as a result of the presence of excess catalyst. The catalyst con‐
tent is therefore fixed at 0.06% of the total amount of raw ma‐
terials.
4. Conclusions
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Among various investigated metal oxides, amphoteric ox‐
ides, especially nano‐Cu2O prepared by hydrolysis, exhibit su‐
Graphical Abstract
Chin. J. Catal., 2013, 34: 548–558 doi: 10.1016/S1872‐2067(11)60494‐4
Solvent‐free thermal decomposition of methylenediphenyl
di(phenylcarbamate) catalyzed by nano‐Cu2O
WANG Qingyin, KANG Wukui, ZHANG Yi, YANG Xiangui, YAO Jie,
CHEN Tong, WANG Gongying*
Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences;
University of Chinese Academy of Sciences; Qingdao Agricultural University
O
O
O
C
N
N C O
O
N
N
O
H
H
+
OH
Nano‐Cu2O shows high catalytic activity for the thermal decomposition of
methylenediphenyl di(phenylcarbamate) under solvent–free conditions.
Solvent‐free thermal decomposition is a green synthetic route to meth‐
ylene di(phenylisocyanate).
Cu2O