Dp. Serrano et al., Catalytic conversion of polystyrene over HMCM-41, HZSM-5 and amorphous SiO2-Al2O3: comparison with thermal cracking, APP CATAL B, 25(2-3), 2000, pp. 181-189
Citations number
16
Categorie Soggetti
Physical Chemistry/Chemical Physics","Environmental Engineering & Energy
HMCM-41, amorphous SiO2-Al2O3 and HZSM-5 zeolite have been studied as catal
ysts in the degradation of polystyrene (PS) at 375 degrees C. HMCM-41 is th
e only catalyst that shows a slight increase in activity with regard to the
thermal cracking, whereas the other two materials present similar or even
lower conversions. This fact has been explained by the existence of competi
tive cross-linking reactions promoted by the acid catalysts. Two types of b
ehaviour can be clearly distinguished according to the product distribution
. Thermal cracking and catalytic degradation over HZSM-5 yield mainly styre
ne (similar to 50 wt.%). On the contrary, the main products resulting from
the catalytic cracking over HMCM-41 and SiO2-Al2O3 are benzene, ethylbenzen
e and cumene but in proportions lower than 20 wt.%. The results obtained ov
er HZSM-5 zeolite are attributed to both its microporous structure and acid
features. External acid sites are practically the only ones active for PS
degradation, since this polymer is too bulky to enter the zeolite micropore
s. In addition, competitive cross-linking reactions also take place, which
are highly promoted by the strength and Bronsted nature of the zeolite acid
sites. Finally, the superior activity obtained over HMCM-41 is explained i
n terms of its uniform mesoporous structure and its medium acid strength. (
C) 2000 Elsevier Science B.V. All rights reserved.