Energy recovery from high density polyethylene plastic via pyrolysis with upgrading of the product by a novel nano MIL-53 (Cu) derived@Y zeolite catalyst using response surface methodology

Abstract

Pyrolysis of plastics is an economical method to recover valuable fuels from waste sources. In this study, the response surface methodology is adopted to model the behavior for the pyrolysis of high-density polyethylene (HDPE). The three operating parameters of temperature in the range of 415 to 585 ° C, feed density in a window between 959 and 967 kg/m3 and reactor loading range from 23 to 57% were selected as the main variables. Using the thermogravimetric analysis (TGA) study for different heat transfer rates, the range at which the feed is fully converted was determined, thus ensuring that the correct operating temperature range was selected. By drawing difference thermogravimetry (DTG) curves and using a dynamic model, the activation energy for converting heavy and light feeds was determined to be 300.984 and 273.57 kJ/mol, respectively. Analysis of the experimental results using the (Central Composite Design) CCD method shows the ease of pyrolysis of light feed, which is agreed upon with less activation energy. As the main goal of this study, the effect of parameters on the liquid fuel production was investigated, and it was turned out that under optimum conditions, the amount of liquid fuel production will be 95.3%. For the optimal conditions, a temperature of 500 ° C, feed density is 963 kg/m3 and reactor loading rate of 40% were determined. Analysis of the exhaust gases also showed that propylene and ethane are the most abundant components of this phase. Furthermore, with the help of analysis of variance, the proposed model to produce liquid fuel and gas yield was evaluated as a significant and the accurate model. Finally, under the optimized conditions, by using a new MIL-53 (Cu) derived @ Zeolite Y catalyst, the percentage of heavy compounds in the fuel was meaningfully reduced, and at the same time, the octane number of the gasoline produced was considerably improved. Based on the energy considerations, it was calculated that the recovery of energy from combustion as well as the sensible energy of the exhaust gases from the reactor, leads to significant savings in total energy consumption to produce each gram of liquid fuel.