VINYL ACETATE FORMATION IN THE REACTION OF ACETYLENE
801
Compared to planar surface of other carbon supports,
the rugged surface of PCS provided enormous specific
surface area and offered much contact area for the
reactants and zinc acetate. Moreover, the holes also
helped to collect the product and possibly reduced the
extent of side reactions.
CONCLUSION
The porous carbon spheres possessing high
mechanical strength, narrow pore size distribution,
and high surface area proved itself to be an effective
support for zinc acetate. The PCS with bumps and
holes on its surface facilitated both heat transfer and
mass transport during the reaction process. Small in
pore diameter as it is, the PCSꢀZn catalyst still exhibꢀ
ited high activities in the formation of vinyl acetate
from acetic acid and acetylene at atmospheric pressure
and moderate temperatures. The singleꢀpass converꢀ
sions of acetic acid and acetylene were comparable to
others' results and the catalyst was supposed to be used
repeatedly due to the good physical properties of PCS
nm
8
6
4
2
Fig. 9. AFM image of the porous carbon sphere surface.
Scan size: 10.0 nm, Setpoint: 0.0 V, Scan rate: 1.6 Hz,
Number of samples: 256).
(
Because the PCS was synthesized via polymerization support.
method using very pure monomer, it meets the basic
demands on a support: low contents of ash and toxic
2
–1
ACKNOWLEDGMENTS
elements; surface area ca. 1000 m g , and well
developed microporous structure etc. In addition,
The financial support by Jiangsu Sopo Corporation
micropores are advantageous in the adsorption of zinc (Group) Ltd. is acknowledged.
acetate without adverse effect on the pore structure.
As already described, the PCS possessed uniform
size and global morphology. Such a support is suitable
for repeated use due to its excellent mechanical
strength originated from the high crystallinity. Found
in the SEM images (Fig. 8) is that the PCS was of regꢀ
ular spheres (Fig. 8a) with scaleꢀlike layers (Fig. 8b) on
its surface. Such a layer structure is advantageous for
heat transfer and mass transport at large scale. Meanꢀ
while the spherical shape could effectively reduce the
dead volume of the fixedꢀbed reactor. Figure 8c
depicts explicitly the gaps between layers and the uniꢀ
form distance between layers. As noticed in Fig. 8d,
most pores were existed in the limited space between
gaps, such that the reactant molecules easily permeꢀ
ated to the micropores directly via the gaps, thus
greatly reducing the diffusion resistance. In contrast,
the adsorption on common activated carbon had to
proceed step by step, first from the bulk phase into
mesopores and from mesopores into micropores subꢀ
sequently.
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7
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 84
No. 5
2010