Conversion Of High-density Polyethylene Research Articles

Quantitative and qualitative analysis of products formed during co-liquefaction of biomass and synthetic polymer mixtures in sub- and supercritical water

The co-liquefaction of biomass and high-density polyethylene (HDPE) mixtures in sub- and supercritical water was studied in a 500 mL stainless steel autoclave. The effects of reaction temperature (613–713 K), holding time (0–80 min), water to biomass-HDPE ratio (4–10), water filling ratio (6–18 vol.%) and biomass-plastic composition (100/0, 80/20, 50/50, 20/80 and 0/100) on the liquefaction of biomass and plastic to oils were investigated in 15.2–27.1 MPa. At 653 K, the most important parameter for the oil yield was biomass/HDPE ratio in the feedstock, and oil yield close to 60 wt.% was obtained for the 20/80 weight ratio of biomass/HDPE mixture. In some cases, non-additive effects were observed, leading to higher yield of oils. Results showed that the addition of biomass to HDPE liquefaction could make the reaction conditions milder, and enhance the conversion of HDPE at lower temperature, implying the synergistic effect of biomass and HDPE. The oils were analyzed by GC-MS and Elemental Analyzer, indicating that the oil from co-liquefaction was better in quality, comparing with that produced from pure biomass.

Enhanced Production of α-Olefins by Thermal Degradation of High-Density Polyethylene (HDPE) in Decalin Solvent: Effect of the Reaction Time and Temperature

The thermal degradation of high-density polyethylene (HDPE) in decalin has been investigated as a method for the feedstock recycling of plastic wastes. The study is focused on the effects of the reaction time and temperature. The solvent increased the HDPE conversion and had a significant effect on the product distribution, which may be assigned mainly to the decalin participation on the reaction mechanism. Short reaction times and low temperatures in the presence of decalin contributed to an enhanced production of gaseous hydrocarbons. Longer reaction times and high temperatures in the presence of this solvent improved the production of C5−C55 hydrocarbons. The gaseous olefins and C5−C32 α-olefins increased with time and temperature; however, the best selectivity to olefins (96.5%) in the gaseous fraction was obtained at 5 h and 375 °C, whereas the higher selectivity to α-olefins (76%) within the C5−C32 fraction was achieved after 5 h and 425 °C.

Catalytic degradation of high density polyethylene over microporous and mesoporous materials

High-density polyethylene (HDPE) was converted to a mixed of lower and higher hydrocarbons over micro (ZSM-11 zeolite with MEL structure) and mesoporous (MCM-41) modified materials. The main liquid hydrocarbons (LHC) were: benzene, toluene, xylenes (BTX), using Zn-, Mo-, and H-containing MEL-zeolites as catalysts. The Zn-zeolite exhibited the highest levels of LHC (>57 wt%) with BTX selectivity of 47 wt%. H-zeolite gave a higher fraction of gaseous hydrocarbons (C1–C4) than Mo- and Zn-zeolites. Zn–MCM-41 produced mainly C5–C16 products. LPG (C3–C4) levels were interesting for all the samples. Thermo gravimetric analyses studies of mixtures catalyst/polymer, have been used to investigate the performance of different catalysts on degradation reactions of the polymer. The catalytic transformation of the polyolefin occurs at lower temperature with respect to thermodecomposition of the pure HDPE (500 °C). A one-pass reactor in the temperature range of 410–500 °C and atmospheric pressure was employed. We observed the complete conversion of HDPE, in the range of temperatures studied (410–500 °C). The synthesized and modified samples after cation incorporation were characterized by TG–DSC, XRD, TPD-FID, FTIR and surface area by BET, in order to verify and to confirm the crystallinity (for microporous materials) and regularity (for mesoporous materials) of the structures, stability and the type of active sites. The reactant was characterized by FTIR, XRD and TG–DSC. Reaction products were analyzed by gas chromatography. By means of development of a competitive catalytic system, we determine the feasibility of the process of degradation of HDPE remainders towards the synthesis of gaseous and liquid hydrocarbons.

97/00837 Coal water slurry reburning ‘low cost NO x compliance system for cyclone-fired boilers’

An investigation has been made of the coprocessing of paper and other lignocellulosic wastes, and also of waste plastics, with coal via the COsteam route—treatment with CO, water and alkali at elevated pressures. The liquefaction of lignocellulosic and polymeric wastes was studied separately and then with the addition of coal. High conversion of lignocellulosic wastes could be achieved at 400°C. Polypropylene and polystyrene are completely converted to liquids and gases at 400°C; however, the conversion of high density polyethylene requires a temperature of 445°C. Coprocessing of Wyodak coal and lignocellulosics at 400°C did not change the yields or product quality compared with the liquefaction of Wyodak coal or lignocellulosics alone. However, the coprocessing of Wyodak coal and polypropylene at 400°C resulted in a decrease in coal conversion accompanied by an increase in the asphaltene fraction from coal. It is possible that the combination of free radicals from the polymer with coal fragments is responsible for this result. However, coliquefaction of Wyodak coal with less than 30% high density polyethylene at 445°C resulted in good coal conversion (85–90%) and did not increase the asphaltene yield from coal.

97/00223 Liquefaction of Taiheiyo coal impregnated with an iron based catalyst

An investigation has been made of the coprocessing of paper and other lignocellulosic wastes, and also of waste plastics, with coal via the COsteam route—treatment with CO, water and alkali at elevated pressures. The liquefaction of lignocellulosic and polymeric wastes was studied separately and then with the addition of coal. High conversion of lignocellulosic wastes could be achieved at 400°C. Polypropylene and polystyrene are completely converted to liquids and gases at 400°C; however, the conversion of high density polyethylene requires a temperature of 445°C. Coprocessing of Wyodak coal and lignocellulosics at 400°C did not change the yields or product quality compared with the liquefaction of Wyodak coal or lignocellulosics alone. However, the coprocessing of Wyodak coal and polypropylene at 400°C resulted in a decrease in coal conversion accompanied by an increase in the asphaltene fraction from coal. It is possible that the combination of free radicals from the polymer with coal fragments is responsible for this result. However, coliquefaction of Wyodak coal with less than 30% high density polyethylene at 445°C resulted in good coal conversion (85–90%) and did not increase the asphaltene yield from coal.

Liquefaction of lignocellulosic and plastic wastes with coal using carbon monoxide and aqueous alkali

An investigation has been made of the coprocessing of paper and other lignocellulosic wastes, and also of waste plastics, with coal via the COsteam route—treatment with CO, water and alkali at elevated pressures. The liquefaction of lignocellulosic and polymeric wastes was studied separately and then with the addition of coal. High conversion of lignocellulosic wastes could be achieved at 400°C. Polypropylene and polystyrene are completely converted to liquids and gases at 400°C; however, the conversion of high density polyethylene requires a temperature of 445°C. Coprocessing of Wyodak coal and lignocellulosics at 400°C did not change the yields or product quality compared with the liquefaction of Wyodak coal or lignocellulosics alone. However, the coprocessing of Wyodak coal and polypropylene at 400°C resulted in a decrease in coal conversion accompanied by an increase in the asphaltene fraction from coal. It is possible that the combination of free radicals from the polymer with coal fragments is responsible for this result. However, coliquefaction of Wyodak coal with less than 30% high density polyethylene at 445°C resulted in good coal conversion (85–90%) and did not increase the asphaltene yield from coal.