Yield Of Terephthalic Acid Research Articles

Hydrothermal liquefaction of post-consumer mixed textile waste for recovery of bio-oil and terephthalic acid

Fast fashion trends lead to significant quantities of textiles produced and discarded, its waste is incinerated or landfilled due to a lack of recycling technologies for mixed textiles. Recycling of mixed textiles by hydrothermal liquefaction (HTL) is a novel approach to produce bio-oil and monomers, as no prior sorting or color removal is required. Herein, post-consumer polyester (polyethylene terephthalate (PET)) and cotton garments were subjected to HTL to produce bio-oil and terephthalic acid (TPA). The effects of blending ratio of PET and cotton, temperature and alkali catalyst on the product distributions are investigated. A maximum bio-oil yield of 26% was attained at 325 °C for a 95% Cotton/ 5% PET mix under alkali conditions. TPA yields ranged from 48 to 91%, where 50/50% PET/cotton resulted in a higher TPA yield than 95/5% PET/cotton textile wastes. The results obtained contribute to the development of sustainable recycling processes of mixed textiles.

Effect of Cellulose and Polypropylene on Hydrolysis of Polyethylene Terephthalate for Chemical Recycling

We examined the hydrolysis of polyethylene terephthalate (PET) with added polypropylene or cellulose and measured the yield of the terephthalic acid (TPA) monomer recovered. The TPA yield from hydrolysis at 250 °C for 30 min nearly doubled from 40 to 75% with the addition of polypropylene (PP). It increased to 55% with the addition of cellulose. There were no statistically significant increases in TPA yield from hydrolysis with the added plastic or biomass at 300 or 350 °C. The solid material recovered from the hydrolytic depolymerization, after first recovering water- and dichloromethane-soluble compounds, was largely TPA, and the amounts of the other reaction products present with it were largely the same irrespective of the presence or absence of PP or cellulose in the reactor. The TPA yield was affected strongly by the reaction time, reaction temperature, and PET type (fiber-reinforced pellet vs chips from a water bottle). The addition of PP or cellulose to the reactor reduces the influence of reaction time on TPA yield from PET hydrolysis.

Photocatalytic upcycling of poly(ethylene terephthalate) plastic to high-value chemicals

Much attention has been drawn to develop efficient poly(ethylene terephthalate) (PET) recycling methods. Reported here is the solar-driven PET recycling coupled with H2 production with carbonized polymer dots-graphitic carbon nitride (CPDs-CN) as catalyst. PET plastic is a “greener” alternative feedstock where its hydrolytic monomer ethylene glycol is converted into high added-value chemicals, mainly including glycolic acid, glycolaldehyde and ethanol; meanwhile, H2 is produced from water splitting. The monomer terephthalic acid yield reaches 304.7 ± 17.2 μmol, exceeding the value of the catalyst-free group nearly twofold. Increased H2 production rate upon hybridization with CPDs is achieved (1034 ± 134 vs. 291 ± 35 μmol g–1 h–1, respectively). The adopted strategy allows plastic waste to be used as a valuable feedstock for the sustainable production of value-added solar chemicals and solar fuels.

Sulfonic acid group functionalized Brönsted acidic ionic liquid catalyzed depolymerization of poly(ethylene terephthalate) in water

Sulfonic acid group functionalized 1,3-dialkyl imidazolium Brönsted acidic ionic liquids are shown as better catalysts in comparison to sulfuric acid with similar acid concentration for the depolymerization of poly(ethylene terephthalate) in hot compressed water. The highest activity was found by using 1.00 M aqueous 1-(3-propylsulfonic)-3-methylimidazolium chloride catalyst, where a practically complete decomposition of poly(ethylene terephthalate) could be achieved after 24 h at 210 °C with a 94% isolated yield of terephthalic acid. The superior catalytic activity of 1-(alkylsulfonic)-3-methylimidazolium chloride in comparison to sulfuric acid with similar acidic strength is explained as a result of charge-transfer and dipolar interactions between catalyst and poly(ethylene terephthalate).

Chemical recycling of waste poly-p-phenylene terephthamide via selective cleavage of amide bonds catalyzed by strong Brönsted base in alcohols.

Poly-p-phenylene terephthamide (PPTA) is widely applied in bulletproof products and composite materials because of its high strength, high modulus, high temperature resistance and creep resistance. The PPTA molecule with highly symmetrical and regular structure is linear structure formed by the alternating connection of benzene ring and amide bond, and the amide bonds between the molecular chains form strong hydrogen bonds. Therefore, the dissolution and depolymerization of PPTA is very challenging. In this work, an efficient catalytic system was developed for the controllable degradation of waste PPTA, and the high-value added monomers terephthalic acid (TPA) and p-phenylenediamine (PPD) were recovered. The results show that the amide bonds of PPTA can be selectively cleaved by the strong Brönsted base catalysts in alcohols, especially in the NaOH/n-butanol system. Under the optimal degradation conditions (5wt% NaOH in n-butanol, 180°C, 6h), the percentage degradation of PPTA is 100%, and the yields of TPA and PPD are 92.0% and 91.5%, respectively. In addition, it is found that the wettability of n-alcohols on PPTA monofilament and the addition of a small amount of water have important influences on the degradation of PPTA. The work elucidates the degradation mechanism of PPTA, and reveals the important factors affecting the depolymerization of PPTA.

Selective catalytic synthesis of bio-based terephthalic acid from lignocellulose biomass

_Efficient synthesis of bio-based chemicals from renewable lignocellulosic biomass is of great significance to promote the sustainable development of chemical industry. This work aims to demonstrate that terephthalic acid, a bulk high value chemical in petrochemical industry, can be synthesized using biomass. This novel controllable transformation process was started with the selective catalytic pyrolysis of sawdust biomass to form p-xylene intermediate. The high p-xylene yield of 23.4% was obtained using the Ga2O3/SiO2/HZSM-5 catalyst under the optimized reaction condition. Subsequently, the selective oxidation of the biomass-derived aromatic intermediates to terephthalic acid was realized with the metal oxide catalysts. The highest terephthalic acid yield of 72.8% with the terephthalic acid selectivity of 82.3% was achieved using the CoMn2O4@SiO2@Fe3O4 catalyst. Based on the study of the catalytic conversion of the model compounds and the catalyst characterizations, the reaction pathways and possible reaction mechanism have been proposed.

Alkali Depolymerization of Poly(ethylene terephthalate) in a Quasi‐solid‐solid Kneading Reaction

AbstractThe alkaline depolymerization reaction of poly(ethylene terephthalate) (PET) under quasi‐solvent‐free conditions was investigated. This is a new approach for recycling PET waste to its monomer building blocks: terephthalic acid and ethylene glycol. The influence of base particle size, reaction temperature, and rotational speed of the employed laboratory kneader on terephthalic acid yield in the quasi‐solid‐solid reaction was investigated. PET is depolymerized almost quantitatively in a reaction time of 5 min at moderate reaction temperatures, with intense mixing affecting the yield of terephthalic acid. The quality of the terephthalic acid monomer, assessed by color index measurements, indicated that the reaction temperature primarily influences the color index of the monomer. By balancing terephthalic acid yield versus color index, optimum reaction conditions were proposed.

Chemo‐enzymatic depolymerization of industrial and assorted post‐consumer poly(ethylene terephthalate) (PET) wastes using a eutectic‐based catalyst

AbstractBACKGROUNDEvery minute, 1 million bottled drinks were purchased worldwide in 2017. Poly(ethylene terephthalate) (PET) bottles are highly recalcitrant wastes, taking at least 450 years to decompose naturally, and their accumulation in the environment triggers a series of environmental impacts. Recycling is an environmentally friendly alternative to PET waste management. A two‐step PET depolymerization approach was studied in this work, comprising chemical glycolysis followed by enzymatic hydrolysis.RESULTSIn the glycolysis reaction, 100% PET was depolymerized in the presence of a eutectic solvent‐based catalyst and ethylene glycol, releasing bis(2‐hydroxyethyl) terephthalate (BHET) as the main product (70% yield). The recovered BHET was then hydrolysed by the highly efficient Candida antarctica lipase B, releasing terephthalic acid (TPA), achieving 0.98 of mole fraction in the best result of the experimental design. The overall yield of chemo‐enzymatic depolymerization of PET into TPA was 57%.CONCLUSIONUsing this integrated approach, a high overall yield of TPA from PET could be achieved within a short process timeframe (24 h). © 2021 Society of Chemical Industry (SCI).

Sub- and supercritical water for chemical recycling of polyethylene terephthalate waste

As a consequence of the widespread use of polyethylene terephthalate (PET), huge amounts of PET waste are generated annually, and thus a critical point of waste management strategy is to reduce these amounts. This study presents the chemical recycling of PET waste using sub- and supercritical water (SubCW and SCW). Two types of PET waste were chosen to study hydrolytic depolymerization: colorless and colored bottles. The experiments were carried out in a batch reactor at temperatures from 250 to 400 °C, with reaction period of 1–30 min. During the hydrolysis of PET waste, primary and secondary products were formed. The highest yield of terephthalic acid (TPA) was identified at 300 °C and a reaction period of 30 min; 90.0 ± 0.4% yield was observed from colorless PET waste and 85.0 ± 0.2% from green PET waste. The purity of final TPA obtained from PET waste was near 100%. The formation of secondary products such as benzoic acid, 1,4-dioxane, acetaldehyde, isophthalic acid (IPA) and carbon dioxide (CO2) were detected.

Chemical and Electrochemical Recycling of End-Use Poly(ethylene terephthalate) (PET) Plastics in Batch, Microwave and Electrochemical Reactors.

This work describes new methods for the chemical recycling of end-use poly(ethylene terephthalate) (PET) in batch, microwave and electrochemical reactors. The reactions are based on basic hydrolysis of the ester moieties in the polymer framework and occur under mild reaction conditions with low-cost reagents. We report end-use PET depolymerization in refluxing methanol with added NaOH with 75% yield of terephthalic acid in batch after 12 h, while yields up to 65% can be observed after only 40 min under microwave irradiation at 85 °C. Using basic conditions produced in the electrochemical reduction of protic solvents, electrolytic experiments have been shown to produce 17% terephthalic acid after 1 h of electrolysis at −2.2 V vs. Ag/AgCl in 50% water/methanol mixtures with NaCl as a supporting electrolyte. The latter method avoids the use of caustic solutions containing high-concentration NaOH at the outset, thus proving the concept for a novel, environmentally benign method for the electrochemical recycling of end-use PET based on low-cost solvents (water and methanol) and reagents (NaCl and electricity).

Manganese and Cobalt Doped Hierarchical Mesoporous Halloysite-Based Catalysts for Selective Oxidation of p-Xylene to Terephthalic Acid

Bimetallic MnCo catalyst, supported on the mesoporous hierarchical MCM-41/halloysite nanotube composite, was synthesized for the first time and proved its efficacy in the selective oxidation of p-xylene to terephthalic acid under conditions of the AMOCO process. Quantitative yields of terephthalic acid were achieved within 3 h at 200–250 °C, 20 atm. of O2 and at a substrate to the Mn + Co ratio of 4–4.5 times higher than for traditional homogeneous system. The influence of temperature, oxygen, pressure and KBr addition on the catalyst activity was investigated, and the mechanism for the oxidation of p-toluic acid to terephthalic acid, excluding undesirable 4-carboxybenzaldehyde, was proposed.

Production of Terephthalic Acid from Corn Stover Lignin

Funneling and functionalization of a mixture of lignin-derived monomers into a single high-value chemical is fascinating. Reported herein is a three-step strategy for the production of terephthalic acid (TPA) from lignin-derived monomer mixtures, in which redundant, non-uniform substitutes such as methoxy groups are removed and the desired carboxy groups are introduced. This strategy begins with the hydro-treatment of corn-stover-derived lignin oil over a supported molybdenum catalyst to selectively remove methoxy groups. The generated 4-alkylphenols are converted into 4-alkylbenzoic acids by carbonylation with carbon monoxide. The Co-Mn-Br catalyst then oxidizes various alkyl chains into carboxy groups, transforming the 4-alkylbenzoic acid mixture into a single product: TPA. For this route, the overall yields of TPA based on lignin content of corn stover could reach 15.5 wt %, and importantly, TPA with greater than 99 % purity was obtained simply by first decanting the reaction mixture and then washing the solid product with water.

Production of Terephthalic Acid from Corn Stover Lignin

AbstractFunneling and functionalization of a mixture of lignin‐derived monomers into a single high‐value chemical is fascinating. Reported herein is a three‐step strategy for the production of terephthalic acid (TPA) from lignin‐derived monomer mixtures, in which redundant, non‐uniform substitutes such as methoxy groups are removed and the desired carboxy groups are introduced. This strategy begins with the hydro‐treatment of corn‐stover‐derived lignin oil over a supported molybdenum catalyst to selectively remove methoxy groups. The generated 4‐alkylphenols are converted into 4‐alkylbenzoic acids by carbonylation with carbon monoxide. The Co‐Mn‐Br catalyst then oxidizes various alkyl chains into carboxy groups, transforming the 4‐alkylbenzoic acid mixture into a single product: TPA. For this route, the overall yields of TPA based on lignin content of corn stover could reach 15.5 wt %, and importantly, TPA with greater than 99 % purity was obtained simply by first decanting the reaction mixture and then washing the solid product with water.

Zinc-catalyzed ester bond cleavage: Chemical degradation of polyethylene terephthalate

Polyethylene terephthalate (PET) materials were recycled by physical methods for a long time. Chemical degradation and recycling of PET materials draw more and more attention in recent years. In this work, PET materials were degraded and recycled via selective cleavage of ester bonds using ZnCl2 as catalysts in aqueous solution. Degradation system 70% ZnCl2/H2O presented excellent catalytic properties due to the coordination catalysis of Zn2+. Monomers terephthalic acid (TPA) was reclaimed at 180 °C for 8 h. The yield of TPA reached up to 98.31%, and the purity of TPA was up to 97.14%. The degradation system ZnCl2/H2O solution was recycled and reused for 3 times, and the degradation ratio of PET materials was still up to 100%. In the degradation process, no organic solvent was added. The work provides a green and sustainable strategy to recover high-value-added chemicals (TPA) from waste PET materials in aqueous phase.

Recycling and depolymerization of waste polyethylene terephthalate bottles by alcohol alkali hydrolysis

In this work, a novel alcohol alkali hydrolysis method was explored for the preparation of terephthalic acid (TPA) from waste polyethylene terephthalate (PET). First, a series of single factor experiments on the depolymerization rate of waste PET bottles and the yield of TPA were conducted to determine the optimized experimental conditions, in terms of reaction time, reaction temperature, dosage of ethylene glycol and sodium bicarbonate, amount of distilled water and stirring rate. Then IR spectra and elemental analysis were carried out for the characterization of obtained product. Under optimal experimental conditions, over 98% PET can be depolymerized into the target product (TPA) and the purity and yield of TPA are over 97% and 94%, respectively. Both the experimental and analytical results support a feasible process for the preparation of TPA from waste PET. It is expected that this alcohol alkali hydrolysis method can promise an effective way for the sustainable recycling of waste PET.

Multi-objective optimization of p -xylene oxidation process using an improved self-adaptive differential evolution algorithm

Abstract The rise in the use of global polyester fiber contributed to strong demand of the Terephthalic acid (TPA). The liquid-phase catalytic oxidation of p -xylene (PX) to TPA is regarded as a critical and efficient chemical process in industry [1] . PX oxidation reaction involves many complex side reactions, among which acetic acid combustion and PX combustion are the most important. As the target product of this oxidation process, the quality and yield of TPA are of great concern. However, the improvement of the qualified product yield can bring about the high energy consumption, which means that the economic objectives of this process cannot be achieved simultaneously because the two objectives are in conflict with each other. In this paper, an improved self-adaptive multi-objective differential evolution algorithm was proposed to handle the multi-objective optimization problems. The immune concept is introduced to the self-adaptive multi-objective differential evolution algorithm (SADE) to strengthen the local search ability and optimization accuracy. The proposed algorithm is successfully tested on several benchmark test problems, and the performance measures such as convergence and divergence metrics are calculated. Subsequently, the multi-objective optimization of an industrial PX oxidation process is carried out using the proposed immune self-adaptive multi-objective differential evolution algorithm (ISADE). Optimization results indicate that application of ISADE can greatly improve the yield of TPA with low combustion loss without degenerating TA quality.

Optimization of Microwave-Assisted Preparation of TPA from Waste PET Using Response Surface Methodology

Terephthalic acid (TPA) was prepared from waste polyethylene terephthalate by microwave-assisted depolymerization with TOMAB as catalyst, the structure and properties of TPA were elucidated by using physico-chemical and spectroscopic methods. Single-factors experiments demonstrated that the TPA yield was affected significantly by the factors of catalyst and alkali amount, depolymerization temperature and time. The effects of variables, including catalyst and alkali amount, depolymerization temperature and time, on the TPA yield were evaluted by response surface methodology with a Box-Behnken design. The modified and verified experiments were completed after considering product performance and actual operation, the optimum parameters were determined to be TOMAB 2.7 g, 15% NaOH 260 mL, temperature 85 °C, degradation time 2.2 h. Under these conditions, the average yield of TPA in three replicated experiments is 97.53%, and this value is not significantly different from the value of 98.59% predicted by the model. These results demonstrate that this method is feasible.

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%.

SYNTHESIS OF TEREPHTHALIC ACID BY CATALYTIC PARTIAL OXIDATION OF p-XYLENE IN SUPERCRITICAL CARBON DIOXIDE

Supercritical (sc) fluids are considered to be a promising alternative to toxic organic solvents in a variety of processes. In this work, a study of the synthesis of terephthalic acid (TPA) from p-xylene (PX) using supercritical carbon dioxide (scCO2) as a reaction medium was performed. The effects of various process parameters were investigated, including temperature, residence time, and catalyst loading. The maximum molar yield of TPA that was achieved was less than 35%. The oxidation reaction for producing TPA was unfavorable under most conditions, which is likely due to the poor solubility of the CoBr2 catalyst in scCO2. This was able to be improved by the addition of a small amount of acetic acid or water to the reaction mixture, resulting in improved PX conversion and TPA yield. Furthermore, it was found that the use of an organic cobalt alternative could improve the yield.

Hydrolysis of poly(ethylene terephthalate) waste bottles in the presence of dual functional phase transfer catalysts

ABSTRACTThe hydrolysis of poly(ethylene terephthalate) (PET) obtained from waste bottles was studied. The dual functional phase transfer catalyst [(CH3)3N(C16H33)]3[PW12O40] exhibited outstanding catalytic activity to the hydrolysis of PET. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy were used to confirm the main product terephthalic acid (TPA) of hydrolysis. The effects of temperature, time, particle size of PET and dosage of catalyst on hydrolysis reaction were examined. Under the optimum conditions of reaction temperature 145°C, time 2 h, particle size of PET at 0.5–1 mm and dosage of catalyst at 7 wt %, the conversion of PET and the yield of TPA were almost 100% and 93%, respectively. After easily separated from the product, the catalyst could be reused more than three times without obvious decrease in the conversion of PET and yield of TPA. An economical and convenient process was developed for hydrolysis of PET. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2790–2795, 2013