Inexpensive Volcanic Ash Catalyst for Pyrolysis of Plastic Waste into Fuel Using Sequential Thermo-Catalytic Reactor

Abstract

Abstract Single-stage thermal pyrolysis of plastic waste produces liquid fuel (LF) of low quality and quantity and requires high temperature and long complete pyrolysis time. Pyrolysis of plastic waste via thermal and catalytic route using an existing sequential pyrolysis reactor and catalytic reformer was addressed to overcome this issue. Each low density polyethylene (LDPE) and polystyrene (Styrofoam) waste was converted plastic waste into LF at intervals of 200–400 oC and a pyrolysis time of 30–90 minutes. Low-cost and type of catalyst, such as volcanic ash was divined as important roles in the characteristics and quantity of LF produced. The volcanic ash is revisited to find a better and more effective catalyst in converting plastic waste into LF due to it contains quite high SiO2 and Al2O3. The volcanic ash was activated physically and chemically. The catalyst characteristics were observed based on Brunauer-Emmet-Teller (BET) and Scanning Electron Microscopy–Energy Dispersion Spectroscopy (SEM-EDS) analysis. The properties and influence of using this catalyst in a reformer for second-stage degradation of plastic waste were observed. The characteristics of LF were observed by flash point, smoke point, ignition point, density, viscosity, calorific value, and GC-MS analysis. The results of the BET analysis of activated volcanic ash and inactivated volcanic ash showed a surface area of 3.8475 m2/g and 1.1188 m2/g, respectively. The results of SEM-EDS analysis depicted that the content of SiO2 and Al2O3 in volcanic ash was quite high of 81.89% and 5.57%, respectively with a better adsorption rate than inactive volcanic ash. The most dominant LF composition of styrofoam and LDPE is C8H8 (70.323%) and C10H20 (25.831%), respectively. LF fraction of LDPE pyrolysis has the largest composition in the range of C9–C14 carbon atoms of 61.27% as a high aliphatic proportion. Whereas the LF fraction from styrofoam pyrolysis has the largest composition in the range of C5–C9 carbon atoms of 92.49% with a low percentage of aliphatic hydrocarbons alkanes (paraffin) and alkenes (olefin). Based on the results characteristics and GC-MS analysis, the LF of LDPE pyrolysis is the closest hydrocarbon composition to kerosene, whereas the LF fraction from styrofoam is on par with gasoline fuel, with higher quality compared to commercial gasoline.