Catalytic Degradation of Polystyrene over ZSM-11 Modified Materials

LILIANA B. PIERELLA; MARÍA S. RENZINI; DANIEL S. CAYUELA; OSCAR A. ANUNZIATA

Rio de Janeiro, Brasil

Congreso; Enpromer 2005, 2nd Mercosur Congress on Chemical Engineering and 4th Mercosur Congress on Process Systems Engineering.; 2005

Catalytic transformation of waste polymers into hydrocarbons with higher commercial value shows a great interest. Polystyrene (PS) was transformed mainly to liquid (>94.96 wt %), over MEL modified zeolites: H-ZSM-11 and Zn-ZSM-11. The conversion levels were almost complete between 400-500oC. The main liquid hydrocarbons of PS degradation were 1,5-hexadiene and styrene, and in minor proportion indanes and α-methyl styrene, being these compounds very important in the polymers technology and fine chemical field. A single-pass reactor and atmospheric pressure was employed. The crystallinity, the nature of the structure and the stability of the synthesized and modified catalysts after cation incorporation were confirmed by XRD, FTIR and surface area by BET. According to FTIR experimental data of pyridine adsorbed (at room temperature and 3 Torr) and desorbed at different temperatures, we found the Brönsted (1550 cm-1) and Lewis (1450 cm-1) acidic sites in both samples. Zn-ZSM-11 material shows the formation of new and strong Electron-Donor-Acceptor Adduct (EDA) of pyridine to Lewis sites, compared with the HZSM- 11, since they retain more pyridine than the parent H-ZSM-11 material after outgassing at 400°C under vacuum. The reactant (atactic PS) was characterized by TG-DSC. The glass transition temperature and thermal degradation temperatures can be observed. Reaction products were analyzed by gas chromatography and mass spectrometry. By means of the development of a competitive catalytic system, we determine the feasibility of the process of degradation of PS remainders towards the synthesis of liquid hydrocarbons.