Hydrolysis Of PET Research Articles

Biomass-derived γ-valerolactone: efficient dissolution and accelerated alkaline hydrolysis of polyethylene terephthalate

The dissolution and further alkaline hydrolysis of PET in biomass-derived γ-valerolactone is realized at a relatively mild temperature and high efficiency.

Engineering terephthalic acid product from recycling of PET bottles waste for downstream operations

Since global oil prices have declined, the price of virgin PET has dropped dramatically, and caused the recycling of PET more challenging. To make the situation worse, the rapid precipitation of terephthalic acid (TPA) from alkaline hydrolysis of PET resulted in very small particles of TPA with unfavorable filtration and drying behaviors. The aim of this work was to engineer product properties of TPA for downstream operations with the existing processing steps. The size effects of TPA crystals/precipitates on filtration, and on drying behaviors, were conducted in terms of specific cake resistance and drying-rate curve, respectively. The whole operating windows was determined for a process optimization by varying operating temperature, feeding strategy, the proportion of water to dimethyl sulfoxide, and the introduction of a cooling operation. Our whole process could be achieved within 8 h at the optimal conditions. As compared to the literature method for chemical recycling of PET, the optimal case exhibited much improved specific cake resistance of ~4.8 × 106 m/g by two orders, and shortened the drying time to 3 h by three times. The TPA crystalline products were also characterized by FTIR for identification, NMR for purity, PXRD for crystallinity, and SEM for particle morphology.

Supplementation of watermelon peels as an enhancer of lipase and esterase production by Yarrowia lipolytica in solid-state fermentation and their potential use as biocatalysts in poly(ethylene terephthalate) (PET) depolymerization reactions

Yarrowia lipolytica is a yeast that presents high biotechnological potential due to its ability to produce many metabolites, among them lipases and esterases, which are important industrial biocatalysts. Since Brazil is an agroindustrial country, it generates an enormous diversity of residues or byproducts that can be used as a platform for biomolecules production. This work aims to evaluate lipase and esterase production by Y. lipolytica via solid-state fermentation using soybean bran and soybean bran supplemented with watermelon peels in different contents, and subsequent use of the enzyme extracts for poly(ethylene terephthalate) (PET) hydrolysis. Supplementation of watermelon peels in the lowest content led to an improvement of lipase activity in almost 31%, reaching 75.22 U g−1. Esterase productivity was 1.5-fold higher when 20 wt% of watermelon peels were added to the media culture. Timecourse evaluation of enzymes production showed a maximum lipase activity in 14 h and similar esterase activity in 14 and 20 h of fermentation. Proteases production were also intensified in supplemented samples. Enzymes produced with 5 wt% watermelon peels supplementation led to higher terephthalic acid concentration (up to 42.02 µmol L−1) during PET depolymerization. Results suggest a great potential of enzyme production in low cost fermentative media to act as biocatalysts in PET hydrolysis reactions.

Depolymerization of PET into terephthalic acid in neutral media catalyzed by the ZSM-5 acidic catalyst

Reprocessing of waste plastic has been extensively studied. Herein, a facile and efficient method for solving the plastic recycling crisis was developed using micro-wave assisted hydrolysis of poly(ethylene terephthalate) (PET) into terephthalic acid (TPA). Previously developed acid or base catalysts are soluble in reaction media and difficult to separate after the reaction. ZSM-5 based zeolites, which are simply recoverable and facilely re-generable catalysts with Brønsted and Lewis acidic sites, were used herein as an acidic catalyst for the PET hydrolysis reaction. Controlling the Brønsted and Lewis acidic site concentration in the ZSM-5 zeolite by changing the Si/Al ratio of the zeolite framework and counter ion species was applied. The reaction kinetics and activation energy of the PET hydrolysis reaction in the presence of the developed catalyst were studied and compared with catalyst-free conditions. Based on this investigation, the correlation between Brønsted and Lewis acidic sites in ZSM-5-based catalysts and PET depolymerization yield was identified.

Poly(ethylene terephthalate) (PET) degradation by Yarrowia lipolytica: Investigations on cell growth, enzyme production and monomers consumption

The development of technologies for poly(ethylene terephthalate) (PET) depolymerization, such as biocatalysis, has been pointed as a very promising alternative to chemical hydrolysis processes. This work aims to understand the behavior of Yarrowia lipolytica, a robust yeast for diverse applications, in the presence of molecules from the PET production chain such as monoethylene glycol (MEG), terephthalic acid (TPA), bis (2-hydroxyethyl) terephthalate (BHET), PET oligomers, amorphous PET and post-consumer PET. The yeast was cultivated in rich media with and without glucose addition, in order to compare monomers release or consumption. TPA and MEG were consumed more intensely in the absence of glucose. The addition of the diester BHET yielded a 3-fold increased lipase production both at 160 rpm (118 U/L) and 250 rpm (385 U/L). In addition, 250 rpm agitation also provided a higher consumption of TPA (26% increase). The mono(2-hydroxyethyl) terephthalate (MHET) was the main intermediate released during polymer hydrolysis, followed by TPA and BHET. Thus, the use of Yarrowia lipolytica, which is capable of catalyzing the PET hydrolysis is of great potential to reduce the environmental impacts caused by unappropriated disposal of packages.

Efficient Degradation of Poly(ethylene terephthalate) with Thermobifida fusca Cutinase Exhibiting Improved Catalytic Activity Generated using Mutagenesis and Additive-based Approaches

Cutinases are promising agents for poly(ethylene terephthalate) (PET) bio-recycling because of their ability to produce the PET monomer terephthalic acid with high efficiency under mild reaction conditions. In this study, we found that the low-crystallinity PET (lcPET) hydrolysis activity of thermostable cutinase from Thermobifida fusca (TfCut2), was increased by the addition of cationic surfactant that attracts enzymes near the lcPET film surface via electrostatic interactions. This approach was applicable to the mutant TfCut2 G62A/F209A, which was designed based on a sequence comparison with PETase from Ideonella sakaiensis. As a result, the degradation rate of the mutant in the presence of cationic surfactant increased to 31 ± 0.1 nmol min−1 cm−2, 12.7 times higher than that of wild-type TfCut2 in the absence of surfactant. The long-duration reaction showed that lcPET film (200 μm) was 97 ± 1.8% within 30 h, the fastest biodegradation rate of lcPET film thus far. We therefore believe that our approach would expand the possibility of enzyme utilization in industrial PET biodegradation.

Cobalt release of oxygen scavenger added multilayered PET bottles in various domestic solvents

Cobalt catalyzed oxygen scavenger added multilayered PET bottles were inspected in our work. X-ray fluorescent spectrometry (XRF) technique was used to select the investigated bottles. Inductive coupled plasma mass spectrometry (ICP-MS) was applied to determine the cobalt content of different domestic solvents after extraction. Extraction experiments were separated into 48 hour extractions, Lakanen-Erviö extraction, and extraction kinetic experiments. The fruit brandy and the orange juice contained in the bottles were the two most successful agents dissolving cobalt without chemical reactions. 1 M NaOH was the agent dissolving the highest quantity of cobalt as a consequence of the hydrolysis of PET. Continuous cobalt dissolving over time could be experienced when NaOH agent penetrated into the grains of flakes. Reuse of active multilayered bottles for domestic solvents did not show harmful cobalt concentration, but the ground and oxygen scavenger added multilayered PET bottles showed cobalt concentration over the limit value.

Synergistic chemo-enzymatic hydrolysis of poly(ethylene terephthalate) from textile waste.

SummaryDue to the rising global environment protection awareness, recycling strategies that comply with the circular economy principles are needed. Polyesters are among the most used materials in the textile industry; therefore, achieving a complete poly(ethylene terephthalate) (PET) hydrolysis in an environmentally friendly way is a current challenge. In this work, a chemo‐enzymatic treatment was developed to recover the PET building blocks, namely terephthalic acid (TA) and ethylene glycol. To monitor the monomer and oligomer content in solid samples, a Fourier‐transformed Raman method was successfully developed. A shift of the free carboxylic groups (1632 cm−1) of TA into the deprotonated state (1604 and 1398 cm−1) was observed and bands at 1728 and 1398 cm−1 were used to assess purity of TA after the chemo‐enzymatic PET hydrolysis. The chemical treatment, performed under neutral conditions (T = 250 °C, P = 40 bar), led to conversion of PET into 85% TA and small oligomers. The latter were hydrolysed in a second step using the Humicola insolens cutinase (HiC) yielding 97% pure TA, therefore comparable with the commercial synthesis‐grade TA (98%).

Enzymatic Degradation of Aromatic and Aliphatic Polyesters by P. pastoris Expressed Cutinase 1 from Thermobifida cellulosilytica.

To study hydrolysis of aromatic and aliphatic polyesters cutinase 1 from Thermobifida cellulosilytica (Thc_Cut1) was expressed in P. pastoris. No significant differences between the expression of native Thc_Cut1 and of two glycosylation site knock out mutants (Thc_Cut1_koAsn and Thc_Cut1_koST) concerning the total extracellular protein concentration and volumetric activity were observed. Hydrolysis of poly(ethylene terephthalate) (PET) was shown for all three enzymes based on quantification of released products by HPLC and similar concentrations of released terephthalic acid (TPA) and mono(2-hydroxyethyl) terephthalate (MHET) were detected for all enzymes. Both tested aliphatic polyesters poly(butylene succinate) (PBS) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were hydrolyzed by Thc_Cut1 and Thc_Cut1_koST, although PBS was hydrolyzed to significantly higher extent than PHBV. These findings were also confirmed via quartz crystal microbalance (QCM) analysis; for PHBV only a small mass change was observed while the mass of PBS thin films decreased by 93% upon enzymatic hydrolysis with Thc_Cut1. Although both enzymes led to similar concentrations of released products upon hydrolysis of PET and PHBV, Thc_Cut1_koST was found to be significantly more active on PBS than the native Thc_Cut1. Hydrolysis of PBS films by Thc_Cut1 and Thc_Cut1_koST was followed by weight loss and scanning electron microscopy (SEM). Within 96 h of hydrolysis up to 92 and 41% of weight loss were detected with Thc_Cut1_koST and Thc_Cut1, respectively. Furthermore, SEM characterization of PBS films clearly showed that enzyme tretment resulted in morphological changes of the film surface.

Ultrasound-Assisted Alkaline Hydrolysis of Waste Poly(Ethylene Terephthalate) in Aqueous and Non-aqueous Media at Low Temperature

This work demonstrates an attempt to depolymerize the waste poly(ethylene terephthalate) (PET) at low temperature using 20 kHz frequency ultrasound. Alkaline hydrolysis of PET was carried out in an aqueous as well as in methanolic medium. Ultrasound has shown a significant enhancement in the rate of alkaline hydrolysis of PET in methanol compared to an aqueous medium. The rate of alkaline hydrolysis of PET increases with an increase in the temperature and alkali concentration. PET conversion of 69% and 46% was observed with and without ultrasound, respectively, using 10% (w/w) sodium hydroxide (NaOH)-methanol solution at 50°C temperature in 60 min. Pure terephthalic acid was recovered from the PET and characterized using Fourier-transform infrared spectroscopy and acid number. The shrinking core model was proposed for the reaction mechanism with surface reaction as the rate of the controlling step. Kinetic analysis indicates almost equal activation energy and yet shows a significant difference in the frequency factor with and without ultrasound-assisted alkaline hydrolysis. Thus, ultrasound does not alter the intrinsic mechanism of PET hydrolysis. The reason for enhancement in the rate of reaction may be the ultrasound-induced micro-mixing and thereby the frequency of interaction between PET and NaOH molecules.

Alkaline hydrolysis of PVC-coated PET fibers for simultaneous recycling of PET and PVC

Polyvinyl chloride (PVC)-coated poly(ethylene terephthalate) (PET) woven fibers are one of the hardest-to-recycle polymeric materials. Herein we investigate the possibility of recycling both PVC and PET through alkaline hydrolysis of PET. The coated woven fabrics were treated with NaOH, hydrolyzing the PET fibers into water-soluble sodium terephthalate, while the PVC could be removed by filtration. The PET fibers were completely hydrolyzed between 120 and 180 °C in the presence of 1 M NaOH solution, quantitatively yielding terephthalic acid. A minimum PVC dechlorination rate of 1% was simultaneously achieved at 120 °C. Furthermore, no alkaline hydrolysis of the plasticizer contained in the PVC, di(2-ethylhexyl)phthalate, was observed. Thus, the possibility of simultaneously recycling PET and PVC from PVC-coated woven fabrics was demonstrated. Kinetic analyses of PET hydrolysis and PVC dechlorination revealed that the simultaneously occurring reaction processes did not affect the progress of each other. Thus, the absence of interactions between PET, PVC, or their degradation products enables the design of a simplified recycling process without considering the interactions between the materials derived from coated woven fabrics.

Enzymatic recovery of polyester building blocks from polymer blends

Abstract In this study we investigated the ability of a cutinase from Thermobifida cellulosilytica (Thc_Cut1) to hydrolyze poly (ethylene terephthalate) (PET) moieties in different polymer blends. The composition of various materials including commercial available bottles and packaging was determined using Fourier Transform InfraRed spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC). When incubated with PET blended with polyethylene (PE) or polyamide (PA) from packaging and bottles without prior separation, Thc_Cut1 selectively hydrolyzed the PET moieties releasing terephthalic acid (TPA) and mono(2-hydroxyethyl) terephthalate (MHET). Polymer blends were hydrolyzed in an up to 9 times higher extent compared to higher crystalline pure PET. The influence of various parameters like temperature, particle size, crystallinity and product inhibition on hydrolysis of PET moieties by Thc_Cut1 was investigated. The amount of products released was up to 10 times higher when the incubation temperature was increased from 40 °C to 60 °C. The smaller the particle size the higher the hydrolysis rates were. Interestingly, semi-crystalline (24%) PET from bottles was hydrolyzed faster than powder from amorphous PET films (12%). An inhibitory effect of bis(2-hydroxyethyl) terephthalate (BHET) on hydrolysis of PET by Thc_Cut1 was observed.

The hygrothermal degradation of PET in laminated multilayer

This study concerns a multilayer film made with three PET layers coated with evaporated aluminum and a sealant material used for Vacuum Insulation Panels in severe conditions (70°C and 90%RH). The main goal was to determine the mechanism responsible of the multilayer degradation in order to improve the durability. In order to understand the chemical changes, the different PET layers were analyzed by FTIR spectroscopy coupled with microscopy. Firstly, this work overviews all former assignments of the infrared bands for PET polymer, together with a classification of each band according to its sensitivity to crystallization, orientation and chemical degradation. Then the study of PET outer layer by IR spectroscopy led to the identification of series of aging markers characteristic of the polymer hydrolysis: formation of oxidation products, evaluation of crystallinity correlated to molecular weight. A kinetic hydrolysis of PET can be established until 870days in continuous conditions of aging. The degradation on a chemical point of view became significant after 400days. Finally, the combination of macroscopic and microscopic FTIR permitted to determine the changes in each individual layer both in chemistry and crystallinity point of view. Surprisingly, the three PET layers in the multilayers over go similar degradation in severe hydrolysis.

Lipase from Candida antarctica (CALB) and cutinase from Humicola insolens act synergistically for PET hydrolysis to terephthalic acid

Abstract Poly(ethylene terephthalate) (PET) is one of the most important industrial plastics in the world. The development of technologies for its depolymerization aiming at monomer recycling is of paramount interest and in this context enzyme-catalyzed hydrolysis has been recognized as a promising alternative. In the present study, a screening of 10 commercial enzymes using bis-(hydroxyethyl) terephthalate (BHET) as model substrate revealed Candida antarctica lipase B (CALB) and Humicola insolens cutinase (HiC) as potential biocatalysts. HiC showed limitation for the last reaction step, but CALB completely converted BHET to terephthalic acid (TPA), even at the highest substrate concentration investigated (31 mM). When used for PET hydrolysis, HiC demonstrated better potential, although accumulating considerable amounts of the intermediate mono-(hydroxyethyl) terephthalate (MHET). After evaluation of the effects of PET pretreatment, temperature and enzyme addition strategy, the combination of these two enzymes revealed synergy for a more complete PET depolymerization to TPA (mole fraction up to 0.88) and a 7.7–fold increase in PET to TPA yield was achieved. This finding adds new investigation possibilities for one of the most studied and versatile lipases, CALB.

Polysaccharide polyelectrolyte multilayer coating on poly(ethylene terephthalate)

AbstractSurface modification of poly(ethylene terephthalate) (PET) film was conducted by surface hydrolysis with NaOH and layer‐by‐layer assembly based on the electrostatic adsorption of oppositely charged polysaccharides: chitosan and hyaluronic acid. Hydrolysis of PET was verified by water contact angle variation of obtained surfaces and quantified using the toluidine blue O colorimetric method. Polysaccharide coatings of ca 200 nm could be observed using transmission electron microscopy for 10 chitosan/hyaluronic acid layers on PET film. Layer growth and degradation were easily monitored using UV‐visible spectroscopy after labelling of chitosan with fluorescein isothiocyanate of (FITC). Evaluation of degradation of the multilayers by FITC–chitosan release in phosphate buffer solution at pH = 7.4 showed that multilayers remain stable in phosphate buffer during the first 14 days after the loss of weakly bound polyelectrolytes. This fact makes the prepared polyelectrolyte multilayers interesting candidates to be employed as potential antibacterial implants and indwelling biomedical devices. © 2016 Society of Chemical Industry

Hydrolysis of PET by Combining Direct Microwave Heating with High Pressure

The direct hydrolysis of waste poly(ethylene terephthalate) (PET) was carried out in a high pressure reactor under microwave heating condition. Microwave irradiation enhanced the diffusion of water into the PET matrix by the effect of the structure relaxation and therefore resultantly the degradation rate of PET became high compared with the state of the conventional heating. The complete degradation of PET by direct hydrolysis was achieved for 30 min at high reaction temperature (223-232oC) and high pressure (2.3-3.0 MPa) under the microwave heating condition. Although the use of HCl catalyst in the acid hydrolysis of PET decreased the yield of terephthalic acid (TPA) at the low HCl concentration region, the complete degradation of PET could be achieved for 15 min at the HCl concentration of 1.0 wt%.

Alkaline hydrolysis and pretreatment of trilobal high dimethyl 5-sulfoisophthalate sodium cationic dyeable polyester

Lower glass transition temperature and crystallinity degree of trilobal high dimethyl 5-sulfoisophthalate sodium cationic dyeable polyester (THCDP) led to its more sensitivity to strong alkali and high temperature than regular Poly(ethylene terephthalate) (PET). The kinetic behaviors of alkaline hydrolysis of THCDP and PET were further explored, and the kinetics equations determined by regression analysis manifested that THCDP with high content of dimethyl 5-sulfoisophthalate sodium salt (SIP) was more prone to alkali hydrolysis and had higher weight loss rate. A comparatively lower power consumption pretreatment process of THCDP knitted fabrics benefited from the synergistic effect of various additives was applied in this study by response surface methodology and the optimum process with less auxiliaries, especially with less caustic treatment avoided large strength loss of fabric, as well as lower manufacturing cost in an environmentally friendly way.

The Ability of Rheological Studies for Assessment of Hydrolysis During Processing of Polyethylene Terephthalate Nanocomposites

Hydrolysis of poly(ethylene terephthalate) (PET) during processing in the presence of Fe2O3 (ferrite) nanoparticles (IO) was investigated. Three nanocomposites, filled with 2.5, 5, and 10 wt.% of IO nanoparticles, were processed in the melt state at 260°C. A nanocomposite containing 5 wt% of nano-silica was also prepared similarly as the blank sample. Dynamic mechanical thermal properties of the nanocomposites showed that, while the introduction of SiO2 nanoparticles increased the glass transition temperature (Tg) of PET, incorporation of IO nanoparticles led to a decrease in Tg. There was an increase in rheological storage modulus (G′) of PET with incorporation of SiO2 nanoparticles in the low-frequency region. Conversely, the incorporation of IO nanoparticles led to a decrease in G′ in this frequency region. The decrease of G′ was attributed to hydrolysis of PET due to the presence of impurities in the IO. The zero-shear rate viscosity (η0) increased with incorporation of SiO2 nanoparticles. Conversely, this value decreased with incorporation of IO nanoparticles. While rheological studies showed a significant decrease in molecular weight of the PET due to hydrolysis, the IR spectroscopy did not have sufficient ability for assessment of the hydrolysis phenomenon. However, the viscosity-average molecular weight () measurements showed that the molecular weight decrease found via rheological studies was in good accordance with the values.

Reaction kinetics and mechanism of catalyzed hydrolysis of waste PET using solid acid catalyst in supercritical CO2

Hydrolysis of waste poly(ethylene terphthalate) (PET) using solid acid catalyst in SCCO2 is presented in this work for the first time. The mechanism of PET chains scission was proved to be a combination of chain end and random chain scission by Fourier transform ‐ infrared spectroscopy (FT‐IR) and titration analysis. A new reaction kinetics model of PET hydrolysis in SCCO2 was setup by introducing the Arrhenius equation into an ordinary reaction rate equation, the frequency factor and apparent activation energy were expressed in terms of temperature and CO2 pressure, respectively. With this reaction kinetics model, the effects of temperature, and pressure were investigated. An interesting mechanism was proposed to describe the reaction process that both water molecules and hydroniums were carried and penetrated into the amorphous regions of the swollen PET by SCCO2, subsequently hydrolysis reaction preferentially took place in the amorphous regions of both surface and bulk of PET matrix. © 2014 American Institute of Chemical Engineers AIChE J, 61: 200–214, 2015

Determination of EG Content in the Liquid Products of PET Hydrolysis under Microwave Irradiation

The determination of EG content in the liquid products of PET hydrolysis process under microwave irradiation at 170°C 180°C and 190°C was measured by Gas chromatography. The chromatographic column was quartz capillary chromatographic column the carrier gas was nitrogen hydrogen flame ionization detector FID. The result indicated that the concentration curves of EG didn’t follow a dynamic process which suggested that PET hydrolysis under microwave was not a continuous process dynamics.