Effect of varying fraction of polypropylene waste on co-pyrolysis of Delonixregia and Polyalthialongifolia leaves

Abstract

Non-catalytic co-pyrolysis of Delonix Regia (DR) wood and Polyalthia Longifolia (PL) leaves and varying fractions of polypropylene (PP) has been carried out at 600 ​°C in a tubular reactor. The fractions of PP varied in order to have 0 ​wt.%, 10 ​wt.%, 30 ​wt.% and 50 ​wt.% of it in the feed while the composition of DR and PL maintained constant and equal to each other so that to study the effect of PP on co-pyrolysis of two lignocellulosic biomass waste materials. The feed materials, along with the products (bio-oil and biochar) have been extensively characterized for their physicochemical and fuel properties. In addition, extensive advanced material characterization techniques such as Fourier Transform Infrared Spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), etc. have been utilized for analysis purposes. The properties of bio-oil reported in this work are of the organic phase only of the liquid product. The average calorific value of organic fraction of bio-oil is increasing from 22.556 ​MJ/kg to 34.06 ​MJ/kg with increasing wt.% of polypropylene (PP) in co-feed from 0 ​wt.% to 50 ​wt.% respectively, while the calorific value of biochar is showing mixed trend. Density of organic phase decreases from 973 ​kg/m3 to 816 ​kg/m3 with increasing the fraction of PP, while pH display opposite trends i.e., increasing from 4.31 to 4.97 which are close to commercial fuel properties. FTIR confirm the presence of functional groups of alkanes, aromatics, alcohols, phenols, aliphatic, ketone, ethers, etc. in organic fraction of bio-oil; and also confirmed by proton NMR. Further it is also confirmed that fraction of alkanes and aliphatic in bio-oil samples increases with PP fraction in the co-feed. The main finding of this work indicates that the fraction of PP in co-feed improved the physicochemical, chemical and fuel potential of the organic phase of liquid product. However, the trend of yield of organic fraction of liquid is not as expected and the reason could be the presence of leaves of PL because often the yield of liquid product is very low when leafy biomass used as feed.