Al-MCM-41 catalyzed decomposition of polypropylene and hybrid genetic algorithm for kinetics analysis

Mesoporous catalysts (Al-MCM-41) are synthesized by sol–gel and hydrothermal methods to study their effects on the catalytic decomposition of polypropylene (PP) sample. The catalysts are characterized by X-ray diffraction (XRD) analysis and nitrogen adsorption study. Since sol–gel Al-MCM-41 catalyst shows better catalytic activity, further experimental studies were conducted to find its reusability and its activity at five different heating rates. The constant pattern behaviour of the TG curves for different catalyst percentages possibly suggests existence of similar reaction mechanism where large polymer fragments are cracked on the external surface of the catalyst and then enters into the mesopores for further cracking. Thus, presence of catalyst surfaces not only converts the polymer into comparatively smaller fractions, but also makes the decomposition of PP energy effective. Kinetics parameters are estimated based on 15 different decomposition models and the multi-heating rate experimental data both for catalytic and noncatalytic decomposition of PP using hybrid genetic algorithm (HGA). Suitability of the model is tested using corrected Akaike's Information Criteria (AIC_c). Results show that Nucleation and Growth model better predicted the experimental TGA data. However, nth order model also shows good AIC_c score and well predicted the experimental TGA data. Thus, though apparently it seems that Nucleation and Growth model controls the decomposition of PP sample, further investigation in detail including infrared or mass spectroscopy, morphology study using SEM or TEM during such decomposition is very much essential to conclude upon the actual reaction mechanism that controls decomposition of PP sample.