A feasible approach for the treatment of waste computer casing plastic using subcritical to supercritical acetone: Statistical modelling and optimization.

Electronic waste (e-waste) usage has increased tremendously with the rapid evolution of technologies. The accumulated e-waste has now emerged as one of the crucial concerns regarding environmental pollution and human health. Recycling e-waste is commonly focused on metal recovery; nevertheless, a significant fraction of plastics (20-30%) are in e-waste. There is an indispensable need to focus on e-waste plastic recycling in an effective way, which has been mostly overlooked to date. An environmentally safe and efficient study is conducted using subcritical to supercritical acetone (SCA) to degrade the real waste computer casing plastics (WCCP) in the central composite design (CCD) of response surface methodology (RSM) to achieve the maximum oil yield of the product. The experiment parameters were varied in the temperature span of 150-300 °C, residence time between 30 and 120 min, solid/liquid ratio between 0.02 and 0.05 (g/ml), and NaOH amount from 0 to 0.5 g. Adding NaOH into the acetone helps to achieve efficient degradation and debromination efficiency. The study emphasized the attributes of oils and solid products recovered from the SCA-treated WCCP. The characterization of feed and formed products is performed with different characterization techniques such as TGA, CHNS, ICP-MS, FTIR, GC-MS, Bomb calorimeter, XRF, and FESEM. The highest oil yield achieved is 87.89% from the SCA process at 300 °C, in 120min, 0.05 S/L ratio, and 0.5 g of NaOH. GC-MS results disclose that the liquid product (oil) comprises single- and duplicate-ringed aromatic and oxygen-containing compounds. Isophorone is the significant component of the liquid product obtained. Furthermore, SCA's possible polymer degradation mechanistic route, bromine distribution, economic feasibility, and environmental aspect were also explored. This present work represents an environmentally friendly and promising approach for recycling the plastic fraction of e-waste and recovering valuable chemicals from WCCP.

Controlling liquid hydrocarbon composition in valorization of plastic waste via tuning zeolite framework and SiO2/Al2O3 ratio.

Abundance of plastic waste has become threat to the mankind and aquatic life and thus needs to be recycled or converted into value added products. Liquefaction of waste plastics via catalytic cracking is one the efficient routes towards plastic waste management. Concerning this, in present study, conversion of polymer mixture containing polypropylene, low-density polyethylene and high-density polyethylene (PP, LDPE and HDPE) was done for the production of gasoline and diesel range hydrocarbons using two-step cracking approach. MWW and MFI (12 and 10 member ring structures respectively) type zeolites having different pore structure and acidity were used for catalytic cracking of polymer feed at 350 °C. Investigations revealed that MWW type zeolite having two independent pore channels selectively provides gasoline range of hydrocarbons (C7-C12, 99.12%) in polymer cracking reaction as compared to MFI type which results in C13-C20 range of hydrocarbons (73.19%). Hydrocarbon compositions were confirmed from GC-MS, 1H, 13C NMR and FT-IR techniques. In activity results it was observed that acidity of zeolites affects the liquid yield and hydrocarbon distribution as analysed by using zeolites of two different SiO2/Al2O3 (SAR) ratio (30 and 55) which directs that zeolite (MFI/MWW) with lower SAR (30) having higher acidity results in higher yield of fuel range liquid hydrocarbons as compared to higher SAR (55) zeolite. Characterization studies such as XRD, N2-physisorption, NH3-TPD, FE-SEM and EDX were performed to check the physiochemical properties of zeolite and correlated with the activity. Overall, the present investigation provides detailed comparative study on plastic degradation using MFI and MWW type zeolites resulting into different range of liquid hydrocarbons.

High quality liquid fuel production from waste plastics via two-step cracking route in a bottom-up approach using bi-functional Fe/HZSM-5 catalyst.

Plastic waste is a serious menace to the world due to its fastest growth rate of ~ 5% per annum and requires efficient technologies for its safe disposal. Plastic liquefaction producing liquid hydrocarbons is an effective way to dispose waste plastics in an eco-friendly manner. In present study, high quality liquid fuel is produced from waste plastics via two-step bottom-up cracking approach. A comparative analysis of liquid products obtained in thermal and catalytic cracking performed at relatively lower temperature (350 °C) with minimal catalyst to plastic feed ratio (1:30) has been studied. Catalytic cracking via two-step bottom-up route provides higher fraction of fuel range hydrocarbons in comparison to the thermal cracking. Catalytic cracking is performed using two different catalysts; HZSM-5 and 5%Fe/HZSM-5 in which later results in higher liquid yield (76 wt%) than former (60 wt%) having comparable fuel characteristics. GC-MS results confirm that liquid product obtained via catalytic cracking contains higher fraction of fuel range hydrocarbons (C6-C20); 66.39% for 5%Fe/HZSM-5 and 47.33% for HZSM-5 which is comparatively higher than that obtained in thermal cracking (27.39%). FT-IR, 1H and 13C NMR spectroscopic studies confirm that liquid hydrocarbons obtained via catalytic cracking have comparable chemical characteristics with fuel range hydrocarbons. Physiochemical properties of catalysts are studied using XRD, XPS, BET, FE-SEM, HR-TEM, NH3-TPD and H2-TPR techniques and correlated with activity results. Analysis of commercial diesel fuel is also incorporated to compare the fuel characteristics of liquid products.