Conversion Of Low Density Polyethylene Research Articles

Stable cage for photocatalyst in plastics enables conversion of low density polyethylene to photodegradable plastics with visualizable stable stage

Converting conventional plastics into photodegradable plastics using photocatalysts as additives shows promise to develop degradable plastics sustainably and efficiently. However, inhibiting the degradation performance of the photocatalyst visually during usage of plastics remains challenging. We propose constructing a photocatalyst with a visualizable stable stage by using a complex of I-/I2, α-cyclodextrin, and hydroxyethyl cellulose as the stable cage to modify TiO2. The stable cage possessing blue color inhibits the photocatalytic performance under illumination forming stable stage. After specific illumination periods, the stable cage changes to white and the photocatalytic performance starts. The photocatalyst is then added to low density polyethylene forming photodegradable plastics with a visualizable stable stage. The complex consumes photogenerated electrons and holes via I5-/I3- interconversion. During illumination, the evolution of the complex’s band energy is crucial for controlling photocatalytic performance. This work paves the way to converting 99 % of plastics in the market into usable photodegradable plastics.

Surface Modification of Fe-ZSM-5 Using Mg for a Reduced Catalytic Pyrolysis Temperature of Low-Density Polyethylene to Produce Light Olefin

Although the catalytic pyrolysis of low-density polyethylene (LDPE) to produce light olefin has shown potential industrial application advantages, it has generally suffered when using higher pyrolysis temperatures. In this work, Mg-modified Fe-ZSM-5 was used for catalytic conversion of LDPE to obtain light olefin in a fixed bed reactor. The effects of catalyst types, pyrolysis temperatures, and Mg loading on the yield of light olefin were investigated. The 1 wt% Mg loading slightly improved the yield of light olefin to 38.87 wt% at 395 °C, lowering the temperature of the pyrolysis reaction. We considered that the higher light olefin yield of Fe-Mg-ZSM-5 was attributed to the introduction of Mg, where Mg regulated the surface acidity of the catalyst, inhibited the secondary cracking reaction, and reduced coking during the pyrolysis process. Furthermore, the addition of Mg also dramatically reduced the average particle size of Fe oxides from 40 nm to 10 nm, which is conducive to a lower catalytic reaction temperature. Finally, the spent catalyst could be easily regenerated at the conditions of 600 °C in airflow with a heating rate of 10 °C/min for 1 h, and the light olefin yield remained higher than 36.71 wt% after five cycles, indicating its excellent regeneration performance.

Conversion of Low-Density Polyethylene (LDPE) and Mixed Low-Density Polyethylene with Polyethylene Terepthalate (LDPE and PET) into Hybrid Fuel

This research aims to provide the recycling techniques of low-density polyethylene (LDPE) and mixture of polyethylene terephthalate (PET) with low-density polyethylene (LDPE) waste. As a means of converting abundant waste to wealth, pyrolysis of LDPE and mixed LDPE - PET was carried out in a batch reactor made of stainless steel at temperatures between 450 – 460OC. The vapor produced from melting the waste was condensed to form the liquid hydrocarbon (fuel oil) product. The effect of reaction time and product yield were investigated. The physicochemical properties of the pyrolysis oil measured include density, specific gravity, flash point, color, fire point, flammability and viscosity. For the LDPE the flash point, fire point, density, specific gravity, and viscosity was found to be 39.5 oC, 48 oC, 8.1872, 0.793g/cm, 0.775g/cm3, and 1.566 cSt respectively while for the Mixture of LDPE with PET the flash point, fire point, density, specific gravity, viscosity and Sulphur content was found to be 44 oC, 48 oC, 8.1872, 0.7837g/cm, 0.7916 g/cm3, 1.1660 cSt and 8.1872 respectively. These values were found to be within the range of kerosene values. The fuel was tested in both kerosene lamp and petrol generator.

Catalytic Pyrolysis of Waste Low-Density Polyethylene (LDPE) Carry Bags to Fuels: Experimental and Exergy Analyses

The present investigation reports the results of experiments related to the conversion of low-density polyethylene (LDPE) waste carry bags to fuel through an economic catalytic pyrolysis method in a batch reactor using zinc oxide (ZnO) as the catalyst. Plastics are highly beneficial for the day-to-day activities of human beings; however, their decomposition is limited due to their strong covalent bonding. Degradation of these big molecules into smaller ones or monomers has been attempted by several researchers in recent decades, with limited success. Pyrolysis is one of the ideas used to convert plastics, with the crowded structure of polymers, into fuel rather than small molecules. Among these plastics, LDPE is widely used as carry bags throughout the world, and, herein, the results of catalytic pyrolysis of the conversion of LDPE into fuel are reported. A compact laboratory-scale batch reactor, specially designed at our laboratory, was used to carry out the pyrolysis process. Different dosages of ZnO were used as a catalyst to carry out the pyrolysis at a specific temperature. The optimal dosage of ZnO for a 50 g waste LDPE batch was found to be 0.6 g to get the maximum oil yield. The yielded oil was analyzed chemically through Fourier transform infrared spectroscopy (FTIR) and a Reformulyzer M4 Hydrocarbon Group Type Analyzer. Evaluation of physical and chemical exergy along with exergetic efficiency of the process was carried out. The described experiments and the results represent a small but significant step toward curbing the menace of plastic solid wastes, which are degrading the environment and human life worryingly, and allowing them to be utilized for generating low-cost fuel for transportation and other applications.

Conversion of low-density polyethylene into monocyclic aromatic hydrocarbons through continuous microwave pyrolysis with ex-situ dual-catalyst beds

The single-use of polyolefins-based individual protective equipment has led to the rapid generation of substantial plastic waste. This study aimed at cleaner disposal of the polyolefin waste, and carried out the continuous microwave pyrolysis (CMP) of low-density polyethylene (LDPE) over dual-catalyst beds of MCM-41 and HY. The dual-catalyzed trial was able to produce more condensate fractions with higher selectivity of monocyclic aromatic hydrocarbons (MAHs), compared with using only MCM-41 or HY zeolite. It was because the larger pore size of the MCM-41 catalyst (4.00 nm) could crack long-chain polyolefin intermediates into shorter chains. This alleviates steric and diffusional resistance while entering and exiting the micropores of the HY zeolite (0.74 × 0.74 nm). The maximum liquid yield (63.75 wt%) and MAHs selectivity (78.21%) were achieved at a catalysis temperature of 450 °C, feedstock to catalyst ratio of 8:3, and HY to MCM-41 ratio of 2:1. In addition, the performance of the CMP reactor was also compared favorably with the batch microwave pyrolysis (BMP) reactor under the same conditions. It has been found that the CMP reactor generated more MAHs products, whereas the BMP reactor was more selective for the generation of polycyclic aromatic hydrocarbons (PAHs) and gas products. The combination of CMP and the co-catalysis process offers new insight into sustainable management and value-added recovery of medical plastic waste.

Systematic study of low temperature cracking of low-density polyethylene with ZSM-5

The viability of cracking low-density polyethylene (LDPE) over H-ZSM-5 catalysts at reaction temperatures below 300 °C was demonstrated using ZSM-5 catalysts with varying textual properties and acid site content. While ZSM-5 made from standard syntheses could catalyze LDPE cracking it was found that increasing the external surface area of H-ZSM-5 from 24 m2/g to 325 m2/g resulted in a dramatic increase in LDPE conversion. For all catalysts the products were permanent hydrocarbon gas products in the C1–C5 range. H-ZSM-5 prepared in nanosheet and nanosphere morphologies achieved 64 wt% and 58 wt% LDPE conversion, respectively, compared to a standard H-ZSM-5 sample with micron-sized crystals that achieved 28 wt% conversion after 8 h at 250 °C under inert conditions. It was also found that strong Brønsted acid sites were necessary for high conversion of LDPE in this temperature regime as shown by the relatively weaker solid acid catalysts Al-MCM-41 and B-MFI converting negligible LDPE under the same reaction conditions. Lastly, a low molecular weight model molecule (n-tetracosane) was tested to gain insight into the cracking mechanism of LDPE over MFI catalysts. The findings in this work point to new approaches for catalyst design to achieve low temperature LDPE depolymerization.

Conversion of low-density polyethylene into monocyclic aromatic hydrocarbons by catalytic pyrolysis: Comparison of HZSM-5, Hβ, HY and MCM-41

The catalytic properties of different catalytic materials on the pyrolysis of plastics have been extensively investigated. In order to better understand the relevant mechanism of catalytic pyrolysis of plastic waste, the effect of different acidity and pore size of catalytic material on its pyrolysis kinetic parameters and the distribution of pyrolysis products needs to be studied to provide a stronger theoretical basis for its resource utilization. This study aims to study the effects of HZSM-5, Hβ, HY and MCM-41 on the thermodynamic properties , kinetic parameters and pyrolysis characteristics of low-density polyethylene (LDPE), analyze the relationship between the specific catalytic pyrolysis products and the properties of the catalyst. Among the four catalysts, HZSM-5 obtained the most concentrated product distribution and the highest yield of monocyclic aromatic hydrocarbons , and it was found that the cracking of LDPE mainly occurred in its pores. Due to the large pore size and low concentration of acid sites, the main product type obtained by MCM-41 was olefins . In addition, it was found that HY reduced the pyrolysis temperature of LDPE and the activation energy of the reaction to the greatest extent. The different catalytic effects were mainly caused by different pore structures and acid site concentration. Moreover, it was found that the addition of catalyst changed the cracking mechanism of LDPE. Under the comprehensive consideration with the goal of producing monocyclic aromatic hydrocarbons, HZSM-5 is the most suitable catalyst among them. • The catalytic effects of HZSM-5, Hβ, HY and MCM-41 were studied. • HZSM-5 is the most suitable catalyst for the production of MAHs from LDPE. • Different pore structures and acid sites cause the changes of catalytic effects. • Partial LDPE scission sites changed from random-chain to end-chain due to catalysis. • The cracking reaction of LDPE occurs in the pores of HZSM-5.

A study on biofuel produced from cracking of low density poly ethylenes using TiO2/AlSBA-15 nanocatalysts

The burgeoning concerns over the non-biodegradable plastics wastes could be surpassed either by proper disposal technique or by an effective conversion of the plastic wastes into useful chemicals. Metal oxide; TiO2 and porous; AlSBA-15 catalysts were synthesized and a composite characterized using XRD, BET, N2 adsorption –desorption studies, TPD and SEM techniques. This work was focussed in the catalytic degradation of low density polyethylene over the synthesized catalysts in a fixed bed reactor. A hydrocarbon rich gasoline range of liquid fuel, coke and gas were the expected products from the experiment. The liquid products were analysed using GC MS equipped with J&W Scientific DB-Petro capillary column (100 m × 0.25 mm × 0.5 m). An optimum yield of liquid fuel was obtained with TiO2 catalyst at 1st h of reaction and further the product yield considerably decreased. A marginal increase in % conversion of low density polyethylene into fuel was observed with increasing catalyst: polymer ratio in the presence of TiO2 catalyst till 1:5 ratio. The liquid products contained lower range of hydrocarbons with higher content of active catalyst; while the samples collected at later stage contained heavier components. Mesoporous AlSBA-15 worked comparatively better than TiO2 by converting 89.7% of LDPE into 54.8% combustible liquid products. The catalytic activity of the catalyst followed the order of TiO2/AlSBA-15 (10%) < AlSBA-15 (27) < SiSBA-15 < TiO2. A considerable increase in gasoline fraction from 45.6% to 85.4%, yield of liquid fuel (89.1%) and conversion (98.4%) was observed during cracking in the presence of TiO2/AlSBA-15 catalyst. Plastic liquid fuel produced over the composite catalyst revealed the calorific value of 47.8 MJ/Kg which was higher than the commercial petroleum fuel. Finally, we obtain this biofuel application as mathematical model to evaluate and plot the interaction energy arising from the conjugation of TiO2 - AlSBA-15 nano-catalyst in two possible configuration, linear (conical) and spherical molecules, along the range of the αdistance (z-axis).

DC Thermal Plasma Design and Utilization for the Low Density Polyethylene to Diesel Oil Pyrolysis Reaction

The exponential increase of plastic production produces 100 million tonnes of waste plastics annually which could be converted into hydrocarbon fuels in a thermal cracking process called pyrolysis. In this research work, a direct current (DC) thermal plasma circuit is designed and used for conversion of low density polyethylene (LDPE) into diesel oil in a laboratory scale pyrolysis reactor. The experimental setup uses a 270 W DC thermal plasma at operating temperatures in the range of 625 °C to 860 °C for a low density polyethylene (LDPE) pyrolysis reaction at pressure = −0.95, temperature = 550 °C with τ = 30 min at a constant heating rate of 7.8 °C/min. The experimental setup consists of a vacuum pump, closed system vessel, direct current (DC) plasma circuit, and a k-type thermocouple placed a few millimeters from the reactant sample. The hydrocarbon products are condensed to diesel oil and analyzed using flame ionization detector (FID) gas chromatography. The analysis shows 87.5% diesel oil, 1,4-dichlorobenzene (Surr), benzene, ethylbenzene and traces of toluene and xylene. The direct current (DC) thermal plasma achieves 56.9 wt. % of diesel range oil (DRO), 37.8 wt. % gaseous products and minimal tar production. The direct current (DC) thermal plasma shows reliability, better temperature control, and high thermal performance as well as the ability to work for long operation periods.

Conversion of low density polyethylene (LDPE) over ZSM-5 zeolite to liquid fuel

Catalytic cracking of plastics waste to produce fuel is increasingly gaining the attention of researchers worldwide. The objective of this study is to assess the effects of temperature and liquid hourly space velocity (LHSV) on composition of liquid products from catalytic cracking of LDPE dissolved in benzene. A plausible reaction mechanism was also proposed. The catalytic cracking produced C1C8 hydrocarbons in all runs due to the effective heat exchange between polymer chains and catalysts. Analysis of products composition indicated that catalytic cracking of LDPE generally produced high amount of aliphatic branched-chain compounds, together with moderate amount of cyclic compounds. The reaction conditions also led to alkylation of benzene by the cracking products from LDPE. Hence, it is concluded that the catalytic cracking of LDPE is dominated by free radical mechanism, while the influence of carbenium ion is less pronounced due to low acidity of the catalyst. Overall, it is shown that catalytic cracking of LDPE solution in fixed bed reactor produced higher polymer conversion and liquid yield than conventional reactors and has the potential to extract hydrocarbon energy from recycled polymer waste.

Conversion of low density polyethylene into fuel through co-processing with vacuum gas oil in a fluid catalytic cracking riser reactor

In this work, mixtures of vacuum gas oil and low density polyethylene, a major component of common industrial and consumer household plastics, were pyrolytically co-processed in a fluid catalytic cracking (FCC) riser reactor as a viable alternative for the energy and petrochemical revalorisation of plastic wastes into valuable petrochemical feedstocks and fuel within an existing industrial technology. Using equilibrium FCC catalyst, the oil–polymer blends were catalytically cracked at different processing conditions of temperatures between 773K and 973K and catalyst feed ratios of 5:1, 7:1 and 10:1. The influence of each of these processing parameters on the cracking gas and liquid yield patterns were studied and presented. Further analysed and presented are the different compositional distributions of the obtained liquids and gaseous products. The analysis of the results obtained revealed that with very little modifications to existing process superstructure, yields and compositional distributions of products from the fluid catalytic cracking of the oil–polymer blend in many cases were very similar to those of the processed oil feedstock, bringing to manifest the viability of the feedstock co-processing without significant detriments to FCC product yields and quality.

Conversion of Low Density Polyethylene (LDPE) and Polypropylene (PP) Waste Plastics into Liquid Fuel Using Thermal Cracking Process

Conversion of Low Density Polyethylene (LDPE) and Polypropylene (PP) Waste Plastics into Liquid Fuel Using Thermal Cracking Process

Conversion of Low Density Polyethylene (LDPE) and Polypropylene (PP) Waste Plastics into Liquid Fuel Using Thermal Cracking Process

In every sector of the world today energy is essential. Energy has many forms such as electricity, transportation fuel and so on. A large amount of energy is produced from crude oil, which is used to produce petroleum and petroleum to produce daily usable plastics. The solution to the above mentioned problems can be solved through the utilization of the new develop technology. This new developed technology will remove these hazardous waste plastics from the environment and convert them into eco friendly liquid fuel. The process is used to convert these waste plastics into liquid fuel creates no harmful emissions and can be produced at a very little overall cost. The thermal process utilized to break down the hydrocarbon chains of the polymers and convert them into liquid fuel. A Steel reactor with temperature range from 100 oC to 400 oC is utilized for the plastic thermal degradation process. The process yield about 80-90% liquid product. The experiment is conducted under a fume hood and open air system, no vacuum process is applied in this particular thermal cracking process.

Composition of products from the pyrolysis of polyethylene and polystyrene in a closed batch reactor: Effects of temperature and residence time

The compositions of the pyrolysis products of pure low-density polyethylene (LDPE) and polystyrene (PS) and their mixtures have been investigated over a temperature range from 300 to 500 °C. The pyrolysis experiments were carried out in a closed batch reactor under inert nitrogen atmosphere to study the effects of reaction temperature and residence time. LDPE was thermally degraded to oil at 425 °C however, beyond this temperature the proportion of oil product decreased as a result of its conversion to char and hydrocarbon gas. Compositional analysis of the oil products showed that aliphatic hydrocarbons were the major components, but the proportion of aromatic compounds increased at higher temperatures and residence times. On the other hand, PS degraded at around 350 °C, mainly into a viscous dark-coloured oil. The formation of char only increased marginally until 425 °C, but was dramatically enhanced at 450 and 500 °C, reaching up to 30 wt.%. The oil product from PS even at 350 °C consisted almost entirely of aromatic compounds especially toluene, ethylbenzene and styrene. Under increasing temperatures and residence times, the oil product from PS was preferentially converted to char, while gas formation was preferred for the oil from LDPE. For instance at 500 °C, PS produced about twice the amount of char obtained from LDPE indicating the role of aromatic compounds in char formation via condensation of the aromatic ring structure. During the co-pyrolysis of a 7:3 mixture of LDPE and PS, wax product was observed at 350 °C leading to oil at 400 °C, indicating that the presence of PS influenced the conversion of LDPE by lowering its degradation temperature. The mixture produced more oil and less char than the individual plastics at 450 °C.

Feedstock recycling of polyethylene in a two-step thermo-catalytic reaction system

The conversion of low density polyethylene (LDPE) into high value hydrocarbons has been investigated using a two-step reaction system consisting of an initial pyrolytic furnace followed by an independent reactor containing nanosized n-HZSM-5 zeolite or Al-MCM-41 mesostructured material where the catalytic reforming of the pyrolytic vapours took place. The system was run at temperatures between 425 and 475 °C and the results compared with those obtained in the absence of catalyst. Temperatures of 450 °C and above were required to reach conversion values in excess of 90 wt%. At that temperature and in the absence of catalysts, thermal cracking of LDPE generated almost exclusively α-olefins and n-paraffins over a wide range of molecular weights, most of which (74.7 wt%) collected as liquid products. Catalytic reforming over n-HZSM-5 was effective at 425 °C and caused a significant increase in the proportion of gaseous hydrocarbons (73.5 wt% selectivity at 450 °C) that consisted primarily of olefins. The remaining liquid products contained a high proportion of valuable aromatic and branched species in the gasoline size range (C 5–C 12) making it suitable for blending with commercial gasolines. Owing to its weaker acid properties, catalytic reforming over Al-MCM-41 required the use of higher temperatures (450 °C and above) to produce a lower proportion of gas products (54–58 wt%) but a consequently higher amount of liquid (34–42 wt%) hydrocarbons. Besides, formation of aromatics was less significant than with n-HZSM5, but the resulting oils contained a good combination of olefins and iso-paraffins. This product composition is comparable to commercial transportation fuel.

Conversion of low density polyethylene into petrochemical feedstocks using a continuous screw kiln reactor

Thermal and catalytic degradation of low-density polyethylene (LDPE) has been investigated using a screw kiln reactor provided with two zones of reaction temperature. Thermal degradation experiments carried out at different temperatures and screw speeds have shown that this continuous system is suitable for the LDPE degradation, product outputs up to c.a. 100 g/h being obtained. Compared to a conventional batch reactor, the screw kiln system leads to a lower formation of gaseous products, whereas overcracking of the heavy fractions is also reduced. These differences are probably originated by the intimate contact and the same residence times for all the product fractions that exist within the screw reactor, which is in contrast with the selective and fast withdrawal of volatile products taking place in the batch system. In the catalytic experiments, a mesoporous MCM-41 type aluminosilicate has been used as catalyst, being continuously fed to the screw reactor mixed with the raw plastic material. In these conditions, yields up to 80% towards hydrocarbons within the gasoline range (C 5C 12) have been obtained. Moreover, high amounts of C 7 and C 8 hydrocarbons are present in the gasoline fractions, which is assigned to catalytic oligomerization reactions that selectively affect to C 3 and C 4 gaseous hydrocarbons.