(654g) Controllable Synthesis of Highly Dispersed Cu/SiO2 Catalysts in Supercritical CO2 and Their Application in the Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Controllable Synthesis of
Highly Dispersed Cu/SiO₂ Catalysts in Supercritical CO₂ and their Application in the Hydrogenation of
Dimethyl Oxalate to Ethylene Glycol

Qin-Qin Xu, Guo-Yue Qiaoand
Jian-Zhong Yin*

 State Key Laboratory of Fine Chemicals,
School of Chemical Machinery, Dalian University of Technology, Dalian 116024,
China,

*
jzyin@dlut.edu.cn

Ethylene glycol (EG) is widely used as antifreeze and precursors in the
production of polyesters. One of the most promising approach to EG is coal-based production technology via dimethyl oxalate
(DMO) hydrogenation. Preparation of highly active
catalysts plays a key role in the synthesis of EG
through the coal chemical industry. There are some disadvantages for the
traditional methods to prepare these copper-based catalysts, for example, the
active components are usually poorly dispersed for the impregnation method and
the metal loading is quite low for the ion exchange method. Ammonia-evaporation
method is characterized by highly  dispersed
active components with high metal loading, however, ammonia is very toxic.        

In
this study, highly dispersed and
morphology controllable Cu nanostructures were synthesized within mesoporous
silica in supercritical CO₂ using organic or inorganic Cu precursors. Deposition
pressure, temperature, time and the mass ratio of the precursor to substrates
were found to influence the size of the nanostructures and the metal loading.
Furthermore, Co-solvent was found to have significant influence on the
morphology of the nanostructure. Although the inorganic precursor has large
solubility in ethanol, methanol and n-butyl alcohol, only big nanoparticles
outside the nanochannels were obtained when these
three co-solvents were used. However, when ethylene glycol or the mixture of ethylene
glycol and water were used as co-solvents, large amounts of short nanotubes
were found inside the nanochannels with large metal
loading. It indicates that the role of the co-solvent may have many aspects,
such as enhancement of the precursor dissolution, change of the interaction
between the precursor and the substrates and so on. Finally, the activity,
selectivity and stability of Cu/SiO₂
catalysts for the hydrogenation of dimethyl DMO to EG were evaluated.

Fig.1 TEM images of Cu/SBA-15 prepared in supercritical CO₂