Search

This work addresses a novel bio-solvolysis process for the treatment of complex poly(ethylene terephthalate) (PET) waste using a biobased monoethylene glycol (BioMEG) as a depolymerization agent in order to achieve a more sustainable chemical recycling process. Five difficult-to-recycle PET waste streams, including multilayer trays, coloured bottles and postconsumer textiles, were selected for the study. After characterization and conditioning of the samples, an evaluation of the proposed bio-solvolysis process was carried out by monitoring the reaction over time to determine the degree of PET conversion (91.3–97.1%) and bis(2-hydroxyethyl) terephthalate (BHET) monomer yield (71.5–76.3%). A monomer purification process, using activated carbon (AC), was also developed to remove the colour and to reduce the metal content of the solid. By applying this purification strategy, the whiteness (L*) of the BHET greatly increased from around 60 to over 95 (L* = 100 for pure white) and the Zn content was significantly reduced from around 200 to 2 mg/kg. The chemical structure of the purified monomers was analyzed via infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), and the composition of the samples was measured by proton nuclear magnetic resonance (1H-NMR), proving a high purity of the monomers with a BHET content up to 99.5% in mol.

The chemical recycling of poly(ethylene terephthalate) –PET– fractions, derived from actual household packaging waste streams, using solvolysis, was investigated. This recycling strategy was applied after a previous on-line automatic identification, by near-infrared spectroscopy –NIR–, and a subsequent selective sorting of the different PET materials that were present in the packaging wastes. Using this technology, it was possible to classify fractions exclusively including PET, virtually avoiding the presence of both other plastics and materials, such as paper, cardboard and wood, that are present in the packaging wastes, as they were efficiently recognised and differentiated. The simple PET fractions, including clear and monolayered materials, were adequate to be recycled by mechanical means meanwhile the complex PET fractions, containing highly coloured and multi-layered materials, were suitable candidates to be recycled by chemical routes. The depolymerisation capacity of the catalytic glycolysis, when applied to those complex PET wastes, was studied by evaluating the effect of the process parameters on the resulting formation and recovery of the monomer bis(2-hydroxyethyl) terephthalate –BHET– and the achieved quality of this reaction product. Comparable and reasonable results, in terms of monomer yield and its characteristics, were obtained independently of the type of complex PET waste that was chemically recycled.

Polietilen tereftalato birziklatuaren (rPET) eskaera handiak ingurumenaren gaineko sentsibilizazioak eta legediak bultzatuta, kontsumitu osteko PET plastiko-hondakinen sorkuntza handiarekin batera, birziklatze-prozesu eraginkorren premia ekarri du. Birziklapen-teknologia klasikoak, birziklapen mekanikoa adibidez, ez dira eraginkorrak birziklatzen zailak diren edo birziklatzen ez diren plastikoen kasuan; hau da, geruza anitzekoak diren eta oso kutsatuta dauden hondakinen kasuan. Teknologia hauek ziklo-kopuru mugatua dute, eta despolimerizazio kimikoa, berriz, gai da jatorrizko PETetik hasierako ekoizpeneko lehengaiak ekoizteko. Testuinguru honetan, polietilen tereftalatoaren (PET) hidrolisia PET-hondakinen despolimerizaziorako estrategia jasangarria da, rPET-a birpolimerizatzeko abiapuntu gisa erabil daitekeena eta, beste despolimerizazio teknologiak ez bezala, oso kutsatuta dauden kontsumo osteko PET-hondakinen elikadurak onartzen dituena. Lan honek PET-solbolisiaren egungo egoera aztertzen du, eta bereziki PET-hidrolisiarena, bai laborategi mailan bai industria eskalan, eta haren garapenaren alderdirik garrantzitsuenak zehazten ditu.; The high demand for recycled polyethylene terephthalate (rPET) driven by environmental awareness and legislation, together with the large increase in post-consumer PET plastic waste generation, has resulted in an urgent need for efficient recycling processes. Classical recycling technologies, such as mechanical recycling, are ineffective for those materials which show difficulties to be recycled or non-recycled plastics such as multilayer and highly contaminated waste. These technologies are only applied for a limited number of cycles, whereas chemical depolymerization produces raw materials from original PET to those of its initial production. In this context, polyethylene terephthalate (PET) hydrolysis is a sustainable strategy for depolymerization of PET waste that can be used as a starting element for repolymerization to rPET and

In this work, the low-temperature pyrolysis of a real plastic mixture sample collected at a WEEE-authorised recycling facility has been investigated. The sample was pyrolysed in a batch reactor in different temperature and residence time conditions and auto-generated pressure by following a factorial design, with the objective of maximising the liquid (oil) fraction. Furthermore, the main polymers constituting the real sample were also pyrolysed in order to understand their role in the generation of oil. The pyrolysis oils were characterised and compared with commercial fuel oil number 6. The results showed that in comparison to commercial fuel oil, pyrolysis oils coming from WEEE plastic waste had similar heating values, were lighter and less viscous and presented similar toxicity profiles in fumes of combustion.

The aim of this paper is for the production of oils processed in refineries to come from the pyrolysis of real waste from the high plastic content rejected by the recycling industry of the Basque Country (Spain). Concretely, the rejected waste streams were collected from (1) a light packaging waste sorting plant, (2) the paper recycling industry, and (3) a waste treatment plant of electrical and electronic equipment (WEEE). The influence of pre-treatments (mechanical separation operations) and temperature on the yield and quality of the liquid fraction were evaluated. In order to study the pre-treatment effect, the samples were pyrolyzed at 460 °C for 1 h. As pre-treatments concentrate on the suitable fraction for pyrolysis and reduce the undesirable materials (metals, PVC, PET, inorganics, cellulosic materials), they improve the yield to liquid products and considerably reduce the halogen content. The sample with the highest polyolefin content achieved the highest liquid yield (70.6 wt.% at 460 °C) and the lowest chlorine content (160 ppm) among the investigated samples and, therefore, was the most suitable liquid to use as refinery feedstock. The effect of temperature on the pyrolysis of this sample was studied in the range of 430–490 °C. As the temperature increased the liquid yield increased and solid yield decreased, indicating that the conversion was maximized. At 490 °C, the pyrolysis oil with the highest calorific value (44.3 MJ kg−1) and paraffinic content (65% area), the lowest chlorine content (128 ppm) and more than 50 wt.% of diesel was obtained.

[EN] The performance of olivine, dolomite and gamma-alumina primary catalysts was evaluated in the continuous tar elimination process in which toluene was selected as the biomass gasification tar model compound. Iron was incorporated into these catalysts in order to improve their catalytic activity. All the experiments were performed in a continuous flow fluidized bed micro-reactor, with a steam/toluene ratio of 4 and a space velocity (GHSV) of 820 h(-1), which corresponds to a catalyst amount of 3.8 cm(3). The effect of temperature was studied using olivine in the 800-900 degrees C range, which allowed concluding that 850 degrees C was the best temperature for tar removal. The fresh and deactivated catalysts were characterized by N-2 adsorption-desorption, X-ray fluorescence (XRF), X-ray diffraction (XRD) and temperature-programmed oxidation (TPO). Tar conversion efficiency was assessed by means of carbon conversion, H-2 yield (based on the maximum allowed by stoichiometry), gas composition and product yields, with Fe/Al2O3 leading to the highest conversion (87.6 %) and H-2 yield (38 %). Likewise, Fe/Al2O3 also provided the highest stability, as it allowed operating for long periods with high conversion values (85.9 % after 35 min on stream), although it underwent severe deactivation. The analysis of the spent catalysts revealed that deactivation occurred mainly by coke deposition on the catalyst surface and iron phase oxidation, with Fe/olivine and Fe/dolomite leading to the faster deactivation due to their poorer metal dispersion related to their reduced surface area. The TPO profiles showed that the coke deposited on the three catalysts was amorphous with a very small contribution of highly structured carbon.

The slow pyrolysis of recycled high-density polyethylene (HDPE) has been investigated in a batch autoclave reactor at 430–490 °C and reaction times of 15–60 min, with the aim of obtaining the maximum yield of plastic oil (PO) with an adequate composition for its subsequent valorization in refinery. Specifically, PO yields up to 85–90 wt% have been achieved operating at 430 °C and 15–37.5 min, noting that the obtained yields strongly depend on temperature and, to a lesser extent, on reaction time. Simulated distillation and gas chromatography analyses of PO have shown its potential for its valorization in a waste refinery scheme targeting the production of alternative fuels. Thus, the PO obtained at 430 °C and 15 min is suitable to be cofed to the fluidized catalytic cracking (FCC) unit since it has a simulated distillation curve similar to that of vacuum gasoil (VGO). On the other hand, the PO obtained at 430 °C at the longest reaction time and those obtained at 460 °C are suitable to be fed together with light cycle oil (LCO) into a hydroprocessing unit. The composition of naphtha and middle distillates of PO reveals that these fractions are appropriate for their blending with commercial diesel and gasoline pools after a mild hydrotreating to reduce their olefin content.