الملخص الإنجليزي
Abstract :
The project aims at hydrocracking of waste plastic mixture to produce useful liquid fuel. The plastic mixture used for this study is 24.76% LDPE, 29.85% HDPE, 10.57% PP and 34.82% PS. This project is novel in its work as; catalyst optimization and process optimization are carried using the optimized hierarchical zeolite catalyst in the reaction to degrade plastic mixture of waste origin to produce useful liquid product yield. Optimization is carried out using response surface methodology (RSM) with Central Composite Design (CCD). For preliminary experiments and catalyst synthesis optimization atmospheric setup is used, as for process parameters optimization a different autoclave setup is used. Preliminary experiments were carried out using mesoporous ZSM-5 and Beta Zeolite (BZ), where desilicated alumina impregnated BZ (DBZA) showed best results in terms of liquid yield. Optimization of alumina loading on desilicated catalyst were carried out, where alumina loading and synthesis temperature were considered as factors in the design of experiment. In catalyst optimization, on using 20g of mixed plastic waste as feed, a liquid yield of 9.9g (per 1g of catalyst) was achieved on using optimized mesoporous BZ catalyst which was desilicated at 0.1M NaOH at 75oC and doped with 3g aluminium nitrate per 5g of zeolite (22wt% Al2O3/zeolite) at 90oC, in comparison to parent BZ that gave only 2.1g of liquid yield. These experiments were carried out at catalyst to plastic (C-P) ratio of 1:20 at a temperature of 400oC. The optimized catalyst was then used in process optimization. The parameters selected for process optimization were temperature (360-440 oC), pressure (1-40 bars) and C-P ratio (1:5-1:40). The results indicated that pressure and C-P ratio parameters were not as statistically significant in comparison to temperature. At optimized conditions of 420
oC, 20 bar and C-P ratio of 1:30, 11.27g (per 1g of catalyst) of oil yield was achieved. Two quadratic regression models were developed for each optimization i.e. process optimization (R2~91%) and catalyst optimization (R2~95%). These obtained R2 values showed good fit with the experimental data. Various differential and integral mathematical methods were used based on the TGA data of ZSM-5, BZ and mesoporous Beta Zeolite (MBZ) catalysts. The range of activation energy values was found to be 91.68-170.80 kJ/mol, 51.10-86.80 kJ/mol and 44.74-67.40kJ/mol for ZSM-5, BZ, and MBZ, respectively. It is evident that on using MBZ, the process requires lowest activation energy in comparison to parent BZ or ZSM-5.
