Catalytic Pyrolysis of Plastic Waste: Moving Toward Pyrolysis Based Biorefineries

Abstract

Pyrolysis based biorefineries have great potential to convert waste such as plastic and biomass waste into energy and other valuable products, to achieve maximum economic and environmental benefits. In this study, the catalytic pyrolysis of different types of plastics wastes (PS, PE, PP, and PET) as single or mixed in different ratios, in the presence of modified natural zeolite (NZ) catalysts, in a small pilot scale pyrolysis reactor was carried out. The NZ was modified by thermal activation (TA-NZ) at 550 • C and acid activation (AA-NZ) with HNO 3 , to enhance its catalytic properties. The catalytic pyrolysis of PS produced a higher liquid oil (70 and 60%) than PP (40 and 54%) and PE (40 and 42%), using TA-NZ and AA-NZ catalysts, respectively. The gas chromatography-mass spectrometry (GC-MS) analysis of oil showed a mixture of aromatics, aliphatic and other hydrocarbon compounds. The TA-NZ and AA-NZ catalysts showed a different effect on the wt% of catalytic pyrolysis products and liquid oil chemical compositions, with AA-NZ showing higher catalytic activity than TA-NZ. FT-IR results showed clear peaks of aromatic compounds in all liquid oil samples with some peaks of alkanes that further confirmed the GC-MS results. The liquid oil has a high heating value (HHV) range of 41.7-44.2 MJ/kg, close to conventional diesel. Therefore, it has the potential to be used as an alternative source of energy and as transportation fuel after refining/blending with conventional fuels.

Analysis of a High-Voltage Room Quasi-Smoke Gas Explosion

“…The observation of a minimum of residue on the heated cabling is, however, in agreement with the thermogravimetric analysis (TGA) performed by Miandad et al [17]. By heating test specimens at a rate of 10 K/minute, they found that PE had a two-stage decomposition process, where the initial degradation started at 270 • C and lasted until the temperature reached 385 • C. After that temperature, a sharp increase in degradation was observed, and 95% degradation was achieved with a further temperature increase to 485 • C. They also observed a minimum of remains at temperatures above 510 • C. Comparing the virtually char-free cabling observed in the present study with the TGA by Miandad et al [17] indicates that the cabling was heated to temperatures in excess of 500 • C. The mass loss experienced in the present study shows that there were sufficient pyrolysis products in the smoke layer trapped beneath the ceiling to make it combustible. The CCTV footage shows that the flames emerging after the explosion were smaller than expected, if the whole room volume had been involved in the smoke gas combustion process.…”

“…When heating XLPE and PE to about 400 • C, ethylene, hydrogen, and soot products as well as numerous other products start to form [17]. In this particular case, about a 10-meter length of cabling was pyrolyzed, with only a minimum of residue on the cabling.…”

“…It should be noted that the operator at ground level, not visible in Figure 5, did not see any open flames when looking into the room, either at the electrical equipment releasing pyrolysis products or in the smoke layer. The high-voltage room door was then closed, and the accumulation of combustible pyrolysis products under the ceiling continued and most likely accelerated with increasing spool and wire temperatures [17]. At 10:48:50, an operator, fully dressed in firefighter PPE, slightly opened the door to evaluate the situation and then quickly closed it.…”

Biogenic Composite Filaments Based on Polylactide and Diatomaceous Earth for 3D Printing

“…In these conditions, diatom shells acted as catalyst of thermal decomposition, similarly as zeolites used in the catalytic pyrolysis of organic matter, including polymers. The decrease in T DTG being rather small was related to a low contribution of diatom shell mass in the composites [ 26 ]. The dry mass left after pyrolysis increased, as expected, with a growing concentration of the filler and with an increasing size of the filler fraction used.…”

Catalytic Fast Pyrolysis of Poly (Ethylene Terephthalate) (PET) with Zeolite and Nickel Chloride

“…Thilakaratne et al have suggested that benzene free radicals could react with olefins to produce naphthalenes [37]. The analysis of pyrolysis residue and gaseous products in the previous literature proved that the solid residue is mainly composed of polycyclic aromatic hydrocarbons (PAHs) [13], and carbon oxides (CO 2 , CO) [12,15] account for a large proportion of gases. The same results can be concluded in our work, and it explains the high yield of carbon oxides in catalytic pyrolysis.…”