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The ZSM-12 zeolite was synthesized by the hydrothermal method, using amorphous silica (Merk) as the source of silicon, sodium hydroxide (Merk), pseudoboehmite Catapal B (Vista Chemical, 70% Al 2 O 3 ) as the source of aluminum and methiltriethylammonium chloride (98% MTEACl, Sigma) as the structural template.;The precursors were added in stoichiometric proportion to obtain a gel with the following molar composition: 20MTEACl:10Na 2 O:x-Al 2 O 3 :100SiO 2 :2000H 2 O. The gel was heated at 140 8C for 144 h in a Teflon autoclave.;After crystallization, the autoclave was cooled to room temperature and the solid phase was separated from the liquid phase by vacuum filtration, washed with distilled water and dried at 100 8C for 12 h.;The solid was calcined and submitted to three successive ion exchange processes with 1 M NH 4 Cl solution to obtain the acidic form HZSM-12 zeolite.;HZSM-5 was synthesized in a similar way, using amorphous silica (Merk), sodium hydroxide (Merk), aluminum sulphate hexahydrate (Merk) and tetraproylammonium bromide (Merk) as the template.;The gel obtained by means of stoichiometric proportion was heated at 150 8C for 168 h in a Teflon autoclave.;The bulk structure of the zeolites was confirmed by XRD (Rigaku) analysis with Cu Ka radiation.;The acidic properties of the catalysts were determined by using n-butylamine as the molecular probe, followed by TGA, according to procedures described in the literature .;The specific total surface area of the catalysts was measured using a BET apparatus (Micromeritics ASAP 2010).;The micropore specific area was measured by the t-plot method .;The macropore and mesopore specific area was determined by the difference between the total area and the micropore area.;The crystallite size was determined by SEM spectroscopy (Phillips).


A polypropylene sample SM-6100 from Polibrasil S/A with 12 wt% of calcium carbonate, for use in making domestic furniture, was used for kinetic measurements. The polymer has a density of 0.9 � 103 kg m�3, a melting temperature (ASTM D-1525) of 152 8C and a melting index (ASTM D-1238, 230 8C, 16 kg) equal to 11.5 g/10 min. The sample was injected and mechanically pulverized to obtain a powder. The catalysts were thoroughly mixed with the polymer sample before the kinetics experiments, in a ratio of 10, 30 and 50 wt%. The degradation of the polymer was carried out using Mettler-TGA/SDTA851 TG equipment with a temperature range from 30 to 900 8C, under a nitrogen flow of 25 ml min�1 and different heating rates: 5, 10 to 20 8C min�1. Fivegramsofpolymermixedwithcatalystwere used. The Vyazovkin model-free kinetics method was employed to obtain activation energies and polymer conver- sion data for different temperatures and reaction times.

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