Authors:Anabela Coelho, Luís Costa, Maria Marques, Isabel Fonseca, Maria Lemos, and Francisco Lemos
High-density polyethylene (HDPE) was cracked over HZSM-5 and HY zeolites and the reaction was followed using simultaneous
thermogravimetry (TG) and differential scanning calorimetry (DSC) and was compared with the degradation of the same material
in the absence of an added catalyst. The products obtained in the degradation reaction were analyzed by gas chromatography.
The simultaneous use of the signals from the TG and DSC allowed an accurate description of the thermal and catalytic degradation
of the polymer by application of a novel kinetic model that correlates the two signals that are measured. The kinetic parameters
were estimated by fitting this model to the experimental data obtained by TG and DSC. For both zeolites, the polymer degradation
takes place at lower temperatures when compared with pure thermal degradation. It was also observed that the two zeolites
have a distinct influence on the product distribution.
In the present study, non-conventional solid acid catalysts such as NaY, metal ion exchanged zeolite NaY (Zn2+, Fe3+, Ce3+, La3+ and Nd3+), H-mordenite, H-β and HZSM-5 were used in order to overcome the disadvantages of conventional Friedel-Crafts catalysts for
the acylation of anisole with acetic anhydride. Among the various zeolites studied, the HY zeolite shows an intermediate activity.
Zeolite containing transition metal ions (Zn2+ and Fe3+) are less active and zeolite NaY is nearly inactive. The catalysts exhibit the activity in the order H-β>transition metal
ions (Zn2+ and Fe3+)>HY>NaY zeolite. The highest catalytic activity of H-β could be due to its larger pore size. The type of acidity and the
acid strength in zeolite Y were determined by FTIR and differential scanning calorimetric (DSC) studies on the pyridine adsorbed
catalysts. The correlation of catalytic activity with acidity reveals that Brönsted acid sites in zeolite promote the acylation