The higher consumption of plastic causes environmental problems. This study was aimed at recycling plastic wastes by using a pyrolysis process with the variables were the ratio of polystyrene mixture and heating rate. The types of polystyrene were used namely, oriented polystyrene (OPS), expanded polystyrene (EPS) and high impact polystyrene (HIPS). Ratios of raw material mixture (OPS: EPS: HIPS) of 1: 0: 0, 0: 1: 0, 0: 0: 1, 2: 1: 1, 1: 2: 1, 1: 1: 2, 1: 1 : 1. Heating rate variations were 2 °C/min, 4 °C/min, 6 °C/min, 8 °C/min and 10 °C/min. The analysis was conducted to the physical properties of liquid produced by pyrolysis, namely heating value, kinematic viscosity, density, and flash point. The heating value tended to increase with the increase of heating rate, the highest heating value was obtained at a ratio of a mixture of 2: 1: 1. The lowest kinematic viscosity value was at the ratio of a mixture of 1: 2: 1 and 1: 1: 1. Density fluctuated but tended to increase with the increase of heating rate. Flashpoint of the entire sample was below 32.6 °C. The ratio of a raw material mixture and heating rate affected the content of the compound of the liquid fuel produced. These compounds had different physical properties. The difference of physical property of each compound of the liquid fuel would affect the physical properties of the liquid produced by pyrolysis.

The widespread use of plastics in the community has resulted in increased waste. Plastics are synthetic polymers that are formed as products of fossil fuel and that are difficult to decompose naturally. This research used the pyrolysis process on a fixed bed reactor to utilize plastic waste especially polystyrene type. The raw materials in this study are high impact polystyrene (HIPS), expanded polystyrene (EPS) and oriented polystyrene (OPS). The ratios of raw material (HIPS: EPS: OPS) are 1:0:0, 0:1:0, 0:0:1, 2:1:1, 1:2:1, 1:1:2, and 1:1:1 also heating rates at 2 °C/min, 4 °C/min, 6 °C/min, 8 °C/min and 10 °C/min. The highest yield at 0:0:1 ratio and with a heating rate of 10 °C/min. The heating rate of 10 °C/min generated the highest amount of yields in general at each ratio. Analysis of the compound using Gas Chromatography-Mass Spectrometry (GC-MS). The compound was dominated by aromatic hydrocarbons, with dominant compounds of ethylbenzene, p-xylene, styrene, 2-phenyl- 1propene, 1,3-diphenyl propane and methyl styrene.

The high use of plastic and the length of time the decomposition will worsen environmental conditions. The processing of plastic waste by incineration was not a safe method for the environment because it will produce gas emissions that potentially become pollutants. The catalytic cracking process is one of the ways to process polystyrene plastic waste into liquid fuel. The purpose of this study is to identify the effect of cracking temperature and mass of catalyst towards the volume and fuel quality of the production. The research conducted through the thermal catalytic cracking process. The mass of catalyst Cu-Al2O3 is 0.5 g, 1 g, 1.5 g. The cracking temperature is 150 °C, 200 °C, 250 °C. Cracking time is 90 minutes. The highest volume of the liquid fuel was 113 mL at a 250°C cracking temperature and the addition of 1g catalyst. The results of the best density analysis obtained at 0.74 g/mL, and the octane number of RON is 100, MON is 90, and AKI is 94.4.