(600a) Hydrogenation of Succinic Acid Using Ruthenium Nanoparticles Embedded Catalysts

Hydrogenation of
Succinic Acid Using Ruthenium Nanoparticles Embedded Catalysts

Sang-Ho
Chung^a, Hee-Jun Eom^a, Min-Sung
Kim^a and Kwan-Young Lee^a,b,*

^a Department of
Chemical and Biological Engineering, Korea University, 5-1, Anam-dong,
Sungbuk-gu, Seoul, 136-701, Republic of Korea

^b Green School, Korea
University, 5-1, Anam-dong, Sungbuk-gu, Seoul, 136-701, Republic of Korea

There has been much effort on the
preparation of noble metal nanoparticles for the effective heterogeneous
catalysis because current synthetic technology in nanoparticles is well
established. However, the synthesized metal nanoparticles have been not yet
fully applied to the variety of special catalysis because its born-nature
shortcomings such as aggregation in the reaction conditions, loss of surface
facets, and deactivation. Therefore, up to date, the noble metals were loaded
on structure-enhancing support materials like SiO₂ and Al₂O₃
using several preparation method such as homogeneous deposition precipitation
and dry or wet incipient wetness method. In several chemical reactions, the
reaction conditions of hydrogenation in C4 chemicals are very severe condition
and the catalysts should have durability for the high temperature and pressure.

                  Ruthenium
is very well known active material in the hydrogenation of several chemicals
and several papers discussed its size-dependent surface atomic numbers of its
hydrogenation activity. Here, we attempt to convert succinic acid (SA) into g-butyrolactone
(GBL), 1,4-butanediol (BDO) and tetrahydrofuran (THF), which is an alternative
pathway of petroleum based chemicals because SA can be produced by cellulose-based
biomass materials (Scheme 1).

Scheme
1.
Conversion pathway of hydrogenation of succinic acid.

The ruthenium nanoparticles (Ru NPs) were
synthesized by polyol method and directly embedded in SiO₂ support materials
by modified sol-gel method. The size of Ru NPs was easily controllable by
changing the the synthetic temperature and a bright-field transmission electron
microscopy of synthesized ruthenium nanoparticles directly reveals the
uniformity of the spherical nanoparticles (Fig. 1).
In the modified sol-gel method, the growth kinetics in SiO₂ supports
were divided into three elements and the structure of synthesized SiO₂
cluster just after drying process showed ballistic-vold monomer clusters which
mean this growth of silicate systems occurred predominantly by the condensation
of monomers with growing clusters and the mean free path of the aggregating
species was large compared to the cluster size.

Fig.
1. Bright field
transmission electron microscopy (BF-TEM) image of synthesized ruthenium
nanoparticles. TEM image was taken using a Philips FEI Technai G2 F30 machine,
operated at 300 kV. The average particle size and standard deviation and shape
of ruthenium nanoparticles were calculated by counting 100 particles from TEM
images.

The prepared Ru NPs/SiO₂
catalysts by the combined polyol and modified sol-gel method had another
advantages for securing the enough pore size up to 8.9 nm and pore volume to
1.17 cm³/g. This was obtained by volume expansion phenomena of fluorine-catalyzed
precipitation and the remained PVP in the SiO2 supports just after drying
process and this was confirmed by nitrogen adsorption and desorption analysis (Fig. 2).

Fig.
2. Nitrogen
adsorption-desorption isotherms (left) and pore size distribution (right) of
prepared materials; (a) MCM-41, (b) SBA-15 and (c) RuNPs/SiO₂
catalysts. The nitrogen adsorption and desorption isotherms were measured at
-195° using Micromeritics ASAP 2010 surface area analyzer. BET surface area
was calculated from the BET plot and pore size distribution were calculated
using the BJH method.

The catalytic activity of the
prepared Ru NPs/SiO2 catalysts was tested for conversion of SA into GBL, BDO
and THF and the reaction was carried out from 170 to 215° and filled with pure
hydrogen at 100 bar. When the reaction temperature was 170°, the conversion of
SA was slightly lower but selectivity towards BDO was relatively higher than
other reaction conditions. However, the SA conversion significantly increased
to 95% at 215° while the selectivity towards THF increased (Fig. 3).

Fig.
3. Nitrogen
adsorption-desorption isotherms (left) and pore size distribution (right) of
prepared materials; (a) MCM-41, (b) SBA-15 and (c) RuNPs/SiO₂
catalysts. The nitrogen adsorption and desorption isotherms were measured at
-195° using Micromeritics ASAP 2010 surface area analyzer. BET surface area
was calculated from the BET plot and pore size distribution were calculated
using the BJH method.

Based on this work, GBL, BDO and THF could be
produced by the hydrogenation of succinic acid using the newly synthesized Ru NPs/SiO2
catalysts. Furthermore, the conversion
of SA and selectivity to GBL, BDO and THF was controlled by
adjusting the reaction temperatures.