A review on pyrolysis of plastic wastes

A review on thermal and catalytic pyrolysis of plastic solid waste (PSW)

A comparative investigation on adsorption performances of mesoporous activated carbon prepared from waste rubber tire and activated carbon for a hazardous azo dye--Acid Blue 113.

Processing methods, characteristics and adsorption behavior of tire derived carbons: a review.

This review deals with the state-of-the-art of waste tyre pyrolysis for the first time in literature. Pyrolysis has been addressed as an attractive thermochemical process to tackle the waste tyre disposal problem while allowing energy recovery. Pyrolysis enables the separation of carbon black from tyres and the volatile matter released (condensable and non-condensable compounds) has the potential of renewable energy recovery given the significant proportion of natural rubber present in the tyre. Given this waste-to-energy pathway, a comprehensive review has been carried out in order to show the effects of the main process conditions (heating rate, temperature, pressure, carrier gas flow rate and type, volatiles residence time and pyrolysis time) on the physicochemical properties and distributions of the resulting products (gas, liquid and solid fractions). It has also been reviewed the influence of the size and composition of the feedstock. All reported results have been framed regarding the type of reactor as well as the experimental conditions used to avoid contradictions among the large number of publications on the subject. It is shown that the occurrence of secondary reactions is very sensitive to the interaction of the aforementioned variables. Also, the main properties of the pyrolytic products are pointed out. The liquid and gaseous fractions obtained are a valuable fuel source; while the solid fraction (char) has the recovery potential of low- grade carbon black or as carbon adsorbent after applying an activation step. Special attention has been given to the liquid fraction, highlighting its properties as alternative fuel in compression ignition engines.

Waste tyre pyrolysis – A review

Catalytic pyrolysis of high density polyethylene in a conical spouted bed reactor

The effect of operating conditions on product yields and compositions has been studied in the catalytic cracking of polyolefins (high- and low-density polyethylene and polypropylene) in a conical spouted bed reactor. The catalyst has been prepared by agglomerating an HZSM-5 zeolite (SiO2/Al2O3 = 30) with bentonite and alumina. The study has been carried out in continuous mode, in the 450–570 °C range, with polyolefin flow rates between 1 and 2 g min–1 and feeding up to 1 kg of polyolefin into a 30 g catalyst bed. The result is an excellent performance of the reactor–catalyst pairing for continuous catalytic pyrolysis, given that the yields obtained in the pyrolysis of high-density polyethylene at 500 °C without defluidization problems and very low catalyst deactivation are as follows: 60 wt % C2–C4 olefins, 15 wt % nonaromatic C5–C11 hydrocarbons, 10 wt % single-ring aromatics, and 14 wt % C4- alkanes. Only small differences are observed in the pyrolysis of the different polyolefins.

Continuous Polyolefin Cracking on an HZSM-5 Zeolite Catalyst in a Conical Spouted Bed Reactor

The pyrolysis of poly-(methyl methacrylate) (PMMA) has been studied in a pyrolysis plant provided with a conical spouted bed reactor. This reactor is an interesting technology for the pyrolysis of waste plastics due to its excellent hydrodynamic behaviour and its high heat transfer and versatility. A previous kinetic study was carried out in thermobalance, in which the degradation of this polymer was observed to begin at low temperatures, 553 K. Consequently, the activation energy is low compared to other plastics. The influence of temperature on pyrolysis product distribution in the conical spouted bed reactor has been studied in the 673–823 K range. The products obtained at low temperatures are mainly the monomers of the polymer used for the study methyl methacrylate (MMA) and ethyl acrylate (EA). When the pyrolysis temperature is increased, the yield of monomers is lower due to the higher severity of secondary reactions, and there is a significant increase in the yield of gases. The maximum monomer recovery has been obtained at 673 K, with the yields of MMA and EA being 86.5% and 6.2%, respectively.

Recycling poly-(methyl methacrylate) by pyrolysis in a conical spouted bed reactor

The catalytic cracking of HDPE (high density polyethylene) at 500 °C using a spent FCC catalyst agglomerated with bentonite (50 wt %) has been studied in a conical spouted bed reactor. The reaction is carried out in continuous regime (1 g min–1 of HDPE is fed) with no bed defluidization problems. The results obtained, namely, total conversion, and high yields of gasoline (C5–C11 fraction) (50 wt %) and C2–C4 olefins (28 wt %), are explained by favorable reactor conditions and good catalyst properties. These results are compared with those for a catalyst prepared in the laboratory by agglomerating a commercial HY zeolite (SiO2/Al2O3 = 5.2). The conical spouted bed is a suitable reactor for enhancing the physical steps of melting the polymer and coating the catalyst with the melted polymer. Furthermore, high heat and mass transfer rates promote devolatilization, and short residence times minimize secondary reactions from olefins by enhancing primary cracking products. The meso- and macroporous structure of ...

Polyethylene Cracking on a Spent FCC Catalyst in a Conical Spouted Bed

The catalytic cracking of high density polyethylene (HDPE) has been carried out at 500 °C in a conical spouted bed reactor with two catalysts prepared with HZSM-5 zeolites with SiO2/Al2O3 ratios of 30 and 80. The polyethylene has been fed continuously (1 g min−1) over 10 h to a 30 g catalyst bed. The results show the good performance of the conical spouted bed reactor in minimising the limitations of the physical steps of the process. The deactivation of the catalysts is very low and it is demonstrated that the moderation of the acidity is useful in modifying the product distribution. The SiO2/Al2O3 ratio increment involves a decrease in the total acidity and in the acid strength, resulting in a higher yield of C2–C4 olefins and that of the non-aromatic C5–C11 fraction, and a decrease in the yields of aromatic components and C1–C4 paraffins. The yield of the C2–C4 olefins obtained with the HZSM-5 zeolite catalyst with a ratio of Si/Al2O3 = 80 is 59.8 wt% (that of propylene is 29.6 wt%) and the yield of the gasoline fraction (C5–C11) accounts for 32.1 wt%. The coke deposited on the catalyst has a heterogeneous nature and is constituted by two types of coke, which are deposited on the exterior and the interior of the crystalline channels of the HZSM-5 zeolite. The evolution of the coke is attenuated as the SiO2/Al2O3 ratio of the zeolite is increased.

Gorka Elordi

Papers

Catalytic pyrolysis of high density polyethylene in a conical spouted bed reactor

Continuous Polyolefin Cracking on an HZSM-5 Zeolite Catalyst in a Conical Spouted Bed Reactor

Recycling poly-(methyl methacrylate) by pyrolysis in a conical spouted bed reactor

Polyethylene Cracking on a Spent FCC Catalyst in a Conical Spouted Bed

Effect of the acidity of the HZSM-5 zeolite catalyst on the cracking of high density polyethylene in a conical spouted bed reactor