Homo- and copolymers of N-vinylimidazole belong to a rapidly emerging class of polymeric materials. Because of the fact that these materials can be utilized in several high-temperature processes and applications, such as catalysis, fuel cells, polymeric ionic liquids (PIL), precursors for new materials by thermolysis, etc., and because fundamental details on the thermal behavior of such polymers are lacking, systematic investigations have been carried out to reveal the stability and the mechanism of thermal decomposition of poly(N-vinylimidazole) (PVIm) by using a variety of techniques, such as differential scanning calorimetry (DSC), thermogravimetry (TG), thermogravimetry–mass spectrometry (TG-MS), and pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS). The investigated PVIm was obtained by free radical polymerization initiated by AIBN in benzene at 70 °C. By the unique combination of the applied methods to investigate the thermal decomposition mechanism of PVIm, it was found that the thermal decomposition of PVIm takes place in one main step in the temperature range 340–500 °C. An initial mass loss of 4% occurs before the main endothermic decomposition step due to the evaporation of water and acetone physically bound to the polymer during purification. The major products of the thermal decomposition of PVIm are 1H-imidazole and 1-vinylimidazole accompanied by several minor products, such as benzene and several alkyl aromatics. The relative ratios between imidazoles and aromatics, i.e., the 2 orders of higher amounts of imidazoles, indicate that in contrast to other polymers with heteroatom pendant groups, e.g., poly(vinyl chloride) (PVC), poly(vinyl acetate), (PVAc) and poly(vinyl alcohol) (PVA), not zip-elimination of 1H-imidazole but homolytic scission of the carbon–nitrogen bond is the main reaction of its formation. 1-Vinylimidazole is formed by main chain scission followed by depolymerization. Both 1H-imidazole and 1-vinylimidazole formation lead in part to macroradicals and short conjugated double bond sequences (polyenes) in the chain, the thermolytic cyclization, isomerization, and aromatization of which result in the low amounts of aromatics. These findings served for the basis of formulating the mechanism of the thermal decomposition of PVIm, which can be utilized in the course of further investigations with this unique polymer.

The catalytic effect of HZSM-5 zeolite was studied on the thermal decomposition of model waste mixtures of plastics (composed of PE, PP, and PET) and biomass (composed of newspaper, cardboard, and pine sawdust). The influence of temperature and catalyst ratio as well as the hindering effect of cellulose and lignin on the catalytic decomposition of plastic waste were studied applying analytical pyrolysis at low and high heating rate by thermogravimetry/mass spectrometry (TG/MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), respectively. The products of laboratory scale batch pyrolysis and thermo-catalytic pyrolysis were analyzed in details and compared. HZSM-5 catalyst reduced the thermal stability of plastic waste, but the catalytic effect was blocked when 50% cellulose or 10% lignin were mixed in the plastic waste. Principal component analysis (PCA) has been applied to reveal correlations between the composition of pyrolysis products, pyrolysis temperature and proportion of the applied catalyst. It was established that the hindering effect of biomass could be compensated by applying higher catalyst ratio. In a batch reactor, the use of HZSM-5 catalyst led to a significant increase in the yields of volatiles (both gases and pyrolysis oil); moreover aromatization or isomerization effects have been observed. Aromatic compounds were produced to a reduced extent by thermo-catalytic pyrolysis of biomasscontaining plastic waste compared to that of plastic waste indicating that the cellulose and lignin components of the waste lower the HZSM-5 catalyst activity.