To Terephthalic Acid Research Articles

From Furan to High Quality Bio-based Poly(ethylene furandicarboxylate)

2,5-Furandicarboxylic acid (2,5-FDCA) has been regarded as the ideal bio-based alternative to terephthalic acid (TPA). In recent years, great efforts have been made to synthesize 2,5-FDCA through the following methods: (1) oxidation of 5-hydroxymethylfurfural (HMF) in the presence of complex biocatalyst or metallic catalyst; (2) conversion of 2-furoic acid via the well-known Henkel Reaction. Herein, a new strategy for the synthesis of 2,5-FDCA from furan and acetic anhydride under mild condition is reported. The purity of the resulted 2,5-FDCA was above 99.9%. Acetic acid and iodoform generated in the reaction were recyclable and no other harmful by-products were detected. The thus-obtained 2,5-FDCA was applied for the preparation of poly(ethylene furandicarboxylate) (PEF) of high quality in terms of high molecular weight and good appearance.

Development of an efficient route for combined recycling of PET and cotton from mixed fabrics

Most textile waste is either incinerated or landfilled today, yet, the material could instead be recycled through chemical recycling to new high-quality textiles. A first important step is separation since chemical recycling of textiles requires pure streams. The focus of this paper is on the separation of cotton and PET (poly(ethylene terephthalate), polyester) from mixed textiles, so called polycotton. Polycotton is one of the most common materials in service textiles used in sheets and towels at hospitals and hotels. A straightforward process using 5–15 wt% NaOH in water and temperature in the range between 70 and 90 °C for the hydrolysis of PET was evaluated on the lab-scale. In the process, the PET was degraded to terephthalic acid (TPA) and ethylene glycol (EG). Three product streams were generated from the process. First is the cotton; second, the TPA; and, third, the filtrate containing EG and the process chemicals. The end products and the extent of PET degradation were characterized using light microscopy, UV-spectroscopy, and ATR FT-IR spectroscopy, as well as solution and solid-state NMR spectroscopy. Furthermore, the cotton cellulose degradation was evaluated by analyzing the intrinsic viscosity of the cotton cellulose. The findings show that with the addition of a phase transfer catalyst (benzyltributylammonium chloride (BTBAC)), PET hydrolysis in 10% NaOH solution at 90 °C can be completed within 40 min. Analysis of the degraded PET with NMR spectroscopy showed that no contaminants remained in the recovered TPA, and that the filtrate mainly contained EG and BTBAC (when added). The yield of the cotton cellulose was high, up to 97%, depending on how long the samples were treated. The findings also showed that the separation can be performed without the phase transfer catalyst; however, this requires longer treatment times, which results in more cellulose degradation.

The formation of p-toluic acid from coumalic acid: a reaction network analysis

Diels–Alder cycloaddition of biomass-derived 2-pyrone coumalic acid (CMA) with propylene provides an alternative pathway to produce toluic acid (TA), a precursor to terephthalic acid (TPA) which is a key component in the manufacture of polyethylene terephthalate (PET).

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.

Transformation of dimethyl phthalate esters (DMPEs) by a marine red yeast Rhodotorula mucilaginosa isolated from deep sea sediments of the Atlantic Ocean

A marine red yeast capable of degrading dimethyl phthalate esters (DMPEs) was isolated from deep-sea sediments of the Atlantic Ocean using enrichment culture technique. The yeast was identified as Rhodotorula mucilaginosa Mar-Y3 based on internal transcribed spacer (ITS) gene sequence analysis. The biochemical degradation pathways of three DMPE isomers, namely dimethyl phthalate (DMP), dimethyl isophthalate (DMI), and dimethyl terephthalate (DMT), were investigated using this yeast. The yeast cannot completely mineralize DMPEs, but can transform them to respective phthalate monoester or phthalic acid. R. mucilaginosa Mar-Y3 also degraded different DMPE isomers through varied metabolism pathways and biodegradation rates. The yeast performed one-step ester hydrolysis with a relatively low degradation rate to transform DMP and DMI to the respective monoester; however, monomethyl phthalate (MMP) and monomethyl isophthalate (MMI) were the dead-end products and further metabolism did not proceed. The yeast carried out sequential ester hydrolysis with a relatively high degradation rate to transform DMT to terephthalic acid (TA) via monomethyl terephthalate (MMT), but TA was resistant to further metabolism. These results suggested that phthalate esterases produced by the deep-sea yeast R. mucilaginosa Mar-Y3 had a very high substrate specificity for different DMPE isomers, and that the degradation of DMPEs by this yeast involved distinct esterases responsible for the hydrolysis of two identical carboxylic ester bonds.

High dimension feature extraction based visualized SOM fault diagnosis method and its application in p-xylene oxidation process

Purified terephthalic acid (PTA) is an important chemical raw material. P-xylene (PX) is transformed to terephthalic acid (TA) through oxidation process and TA is refined to produce PTA. The PX oxidation reaction is a complex process involving three-phase reaction of gas, liquid and solid. To monitor the process and to improve the product quality, as well as to visualize the fault type clearly, a fault diagnosis method based on self-organizing map (SOM) and high dimensional feature extraction method, local tangent space alignment (LTSA), is proposed. In this method, LTSA can reduce the dimension and keep the topology information simultaneously, and SOM distinguishes various states on the output map. Monitoring results of PX oxidation reaction process indicate that the LTSA–SOM can well detect and visualize the fault type.

Kinetics of alcoholysis of poly(ethylene terephthalate) in sub- and super-critical isooctyl alcohol to produce dioctyl terephthalate

The alcoholysis kinetics of poly(ethylene terephthalate) (PET) in sub- and super-critical isooctyl alcohol (2-EH) to produce dioctyl terephthalate (DOTP) was studied with a batch reactor under the temperature range from 533 to 653K. Owing to the fast decomposition of DOTP to terephthalic acid (TPA) in the super-critical 2-EH, the kinetics was studied according to two conditions based on temperature less and more than critical temperature of 2-EH as pseudo-first-order reaction. In the sub-critical 2-EH about the temperature range of 533–593K, the decomposition of DOTP was very slow, and thus the apparent activation energy of production rate of DOTP is determined to be 82.14kJ/mol without taking into account decomposition of DOTP. Whereas, as for the super-critical 2-EH, the decompositions of DOTP should be taken into account, and a consecutive pseudo-first-order reaction model from PET to DOTP, TPA and subsequent decomposition products is adopted. The apparent activation energies of production rates of DOTP are 30.29kJ/mol and the decomposition values of DOTP and TPA are 128.14 and 176.43kJ/mol of the super-critical temperature range of 613–653K.

Kinetic Investigations of p-Xylene Oxidation to Terephthalic Acid with a Co/Mn/Br Catalyst in a Homogeneous Liquid Phase

Kinetic investigations of the liquid phase oxidation of p-xylene (pX) to terephthalic acid (TPA) with Co/Mn/Br catalyst were performed in a stirred 50 mL Parr reactor at 200 °C and 15 bar pressure under conditions wherein product precipitation is avoided. The oxidant (O2) was introduced by sparging into the liquid phase at constant gas-phase O2 partial pressure. Apparent kinetic rate constants, estimated by regressing experimental conversion data to a pseudo-first order lumped kinetic model, are at least an order of magnitude greater than those reported in the literature for similar catalytic reactions. We attribute this difference to the presence of gas–solid and liquid–solid mass transfer resistances in the previous studies wherein the TPA product precipitates as it forms, trapping intermediate products and slowing down their oxidation rates. Our results also indicate that it is not possible to completely eliminate the gas–liquid mass transfer limitations associated with the fast intermediate oxidation steps, even when operating without solids formation and at high stirrer speeds. Other types of reactor configurations are therefore needed to better overcome gas–liquid mass transfer limitations. Systematic studies of bromide concentration effects show that the observed reaction rates become zero order in bromide concentration at sufficiently high bromide levels where the elimination of intermediate 4-(bromomethyl)benzoic acid by oxidation is favored. Further, the rate constants do not show any statistically significant dependence on pX concentration as suggested in other reports involving the traditional three-phase gas–liquid–solid reaction system. This again confirms that the formation of a solid phase hinders the overall oxidation rate, resulting in much smaller apparent rate constants.

The quantitative detection of HO˙ generated in a high temperature H2O2 bleaching system with a novel fluorescent probe benzenepentacarboxylic acid

A novel fluorescent probe, benzenepentacarboxylic acid (BA), was developed for the quantitative detection of hydroxyl radicals (HO˙) in a simulated hydrogen peroxide (H2O2) bleaching system. Compared to terephthalic acid (TA), a commonly-used fluorescent probe of HO˙ with four possible reaction sites, the present probe has only one reaction site for HO˙ addition that results in the formation of a single fluorescent product, hydroxybenzenepentacarboxylic acid (HBA). The generation of the single pure fluorescent product by BA, rather than mixtures by TA, made the present probe more sensitive, accurate and reproducible in the quantitative detection of HO˙. Based on the working curve obtained from the fluorescence intensity and HBA concentration, a fluorimetric method for the quantitative detection of HO˙ was developed. The present probe BA was successfully used for the quantitative detection of HO˙ under alkaline and high temperature (80 °C) conditions, in a simulated H2O2 bleaching system. The method was highly sensitive, reproducible, and applicable in a wide temperature range of 20–98 °C. The present novel fluorescent probe will be potential tool for evaluating the generation and function kinetics of HO˙ generated in biological and environmental fields.

Soluble polyarylates containing phosphorus in main chains with thermal stability

ABSTRACTA series of polyarylates containing phosphorus (pho‐PARs) were synthesized from bisphenol A with different molar ratios of bis‐(4‐carboxyphenyl) phenyl phosphine oxide (BCPPO) to terephthalic acid (TPA). When the contents of BCPPO are in the range of 0.4–1.0, the pho‐PARs are readily soluble in a wide range of organic solvents and have the glass transition temperatures of 243.0–260.4°C. The initial degradation temperatures of these pho‐PARs are all above 450°C and their char yields at 800°C under nitrogen atmosphere are in the range of 28.7–33.0%, suggesting they have excellent thermal stability. The results of TG‐FTIR and FT‐IR show the introduction of BCPPO change the decomposition model of the pho‐PARs. The limiting oxygen indexes are at a range of 30.7–34.5%, which suggests that the pho‐PARs are a kind of excellent inherent flame retardant materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3521–3529, 2013

Concurrent formation of furan-2,5- and furan-2,4-dicarboxylic acid: unexpected aspects of the Henkel reaction

The concurrent formation of furan-2,5- and furan-2,4-dicarboxylic acid under solvent free conditions via a disproportionation reaction is described. By reacting potassium-2-furoate at 260 °C in the presence of 22 mol% of (Lewis acidic) catalysts like CdI2 or ZnCl2, potassium-2-furoate is disproportionated to furan and furandicarboxylic acids. Besides furan and furan-2,5-dicarboxylic acid (2,5-FDCA) as the main products, furan-2,4-dicarboxylic acid (2,4-FDCA) is also formed as a by-product. Experimental evidence has been obtained that, under the reaction conditions applied, 2,5-FDCA and 2,4-FDCA are formed by separate reaction pathways. Selectivity towards the different FDCA isomers is affected by the type of catalyst used. Single-crystal X-ray analysis shows that 2,4-FDCA has a more ‘linear’ character compared to 2,5-FDCA and hence is structurally more comparable to terephthalic acid (TA), making it an interesting monomer for synthetic polyesters.

Hybrid Model of Industrialp-Xylene Oxidation Incorporated Fractional Kinetic Model with Intelligent Models

A hybrid modeling approach for the oxidation of p-xylene (PX) to terephthalic acid (TA) in an industrial continuously stirred tank reactor (CSTR) was proposed. First, considering that the reaction factors have a highly nonlinear effect on the kinetic rate constants, support vector regression (SVR) was used to construct the rate constant model based on the data from a laboratory semibatch reactor (SBR). Second, due to the significant difference between the nature of PX oxidation in the laboratory SBR and that in the industrial CSTR, this model was extended via artificial neural network (ANN) to correlate the rate constants in the industrial CSTR with that in the laboratory SBR, and a genetic algorithm is employed to obtain the optimal weights and thresholds by direct fitting of the difference between the hybrid model results and the real industrial data. Further, the reliability of the hybrid model was investigated and satisfactory results were obtained.

Effect of quaternary ammonium salt as a phase transfer catalyst for the microwave depolymerization of polyethylene terephthalate waste bottles

Poly(ethylene terephthalate) (PET) obtained from waste bottle product was depolymerized under microwave irradiation in open vessel equipment. PET bottle was shredded and ground to <0.5mm particle size and subjected to basic hydrolysis to terephthalic acid (TPA) and ethylene glycol using 10% NaOH under the influence of microwave irradiation (200W) in the presence of quaternary ammonium salt as a phase transfer catalyst (PTC). The effect of irradiation time, base concentration, particle size, PTC quantity, and microwave irradiation power on the extent of depolymerization was investigated. Results show that the optimum conditions to give ∼99% of TPA were 10% NaOH, 60min, 200W power, and 3% wt./wt. PTC/PET. This process is viable economically and interesting, since that PTC could be recovered and the side products after acidification are glycol and sodium chloride.

Synthesis and properties of poly(aryl sulfone benzimidazole) and its copolymers for high temperature membrane electrolytes for fuel cells

Poly(aryl sulfone benzimidazole) (SO2PBI) and its copolymers with poly[2,2′-p-(phenylene)-5,5′-bibenzimidazole] (pPBI), termed as Co-SO2PBI, were synthesized with varied feeding ratios of 4,4′-sulfonyldibenzoic acid (SDBA) to terephthalic acid (TPA). Incorporation of the stiff para-phenylene and flexible aryl sulfone linkages in the macromolecular structures resulted in high molecular weight copolymers with good solubility. The chemical stability towards radical oxidation was improved for SO2PBI and its copolymer membranes due to the electron-withdrawing sulfone functional groups. Upon acid doping, the membrane swelling was reduced and the mechanical strength was improved, as compared with their meta structured analogues. At an acid doping level of 11 mol H3PO4 per average molar repeat unit, the Co-20%SO2PBI membrane exhibited a tensile strength of 16 MPa at room temperature and an H2-air fuel cell peak power density of 346 mW cm−2 at 180 °C at ambient pressure. Durability tests with the membrane under a constant current density of 300 mA cm−2 at 160 °C showed a degradation rate of 6.4 μV h−1 during a period of 2400 h, which was significantly lower than that for meta PBI membranes with a similar acid doping level.

Operation Condition Optimization of p-Xylene Oxidation Reaction Process Based on a Fuzzy Adaptive Immune Algorithm

The oxidation of p-xylene to terephthalic acid (TA) is a significant chemical process of purified TA production. Variation of operation conditions of the reaction directly affects the quality of TA. In this paper a fuzzy adaptive immune algorithm (FAIA) was proposed to realize the operation condition optimization of the p-xylene oxidation reaction. In FAIA, a chaotic hypermutation was developed to strengthen the searching ability of the algorithm, and a new immune network regulatory strategy was devised to maintain population adversity. Furthermore, two fuzzy logic modules were constructed to adjust parameters, further increasing the adaptability of the algorithm. The data of function optimization show that FAIA can quickly converge to the global optimum and overcome premature problems. Optimization results of process variable values of the p-xylene oxidation reaction indicate that the application of FAIA in an oxidation reaction process can greatly save the time of operation condition selection and reduc...

Liquid phase oxidation of p-xylene to terephthalic acid at medium-high temperatures: multiple benefits of CO2-expanded liquids

The Co/Mn/Br catalyzed oxidation of p-xylene to terephthalic acid (TPA) is demonstrated in CO2-expanded solvents at temperatures lower than those of the traditional Mid-Century (MC) process. As compared with the traditional air (N2/O2) oxidation system, the reaction with CO2/O2 mixture at 160 °C and using an additional inert gas (N2 or CO2) pressure of 100 bar increases both the yield of TPA and the purity of solid TPA via a more efficient conversion of the intermediates, 4-carboxybenzaldehyde and p-toluic acid. At the same time, the amount of yellow colored by-products in the solid TPA product is also lessened, as determined by spectroscopic analysis. Equally important, the decomposition or burning of the solvent, acetic acid, monitored in terms of the yield of the gaseous products, CO and CO2, is reduced by ca. 20% based on labeled CO2 experiments. These findings broaden the versatility of this new class of reaction media in homogeneous catalytic oxidations by maximizing the utilization of feedstock carbon for desired products while simultaneously reducing carbon emissions.

Chemical Recycling Process of Poly(Ethylene Terephthalate) in High-Temperature Liquid Water

The depolymerization behavior of poly(ethylene terephthalate) (PET) to terephthalic acid (TPA) and ethylene glycol (EG) in high-temperature liquid water is examined in a batch reactor. PET is completely depolymerized in water for 10 min at 573 K. The total energy to obtain TPA and EG from a continuous PET depolymerization process with high-temperature liquid water is estimated.

Simple and convenient method in chemical recyclingSimple and convenient method in chemical recycling of poly(ethylene terephthalate) by using microwave radiation

Microwave assisted ester bond breaking of poly(ethylene terephthalate) (PET) to terephthalic acid (TPA) was performed by using glycerin, diethylene glycol (DEG) or monoethanolamine (MEA) as transesterification reagents and KOH or NaOH as the catalysts and results were compared with PET degradation by conventional heating method. Comparisons of reaction times showed significant enhancement of reaction rates in the microwave assisted experiments in comparison with the process going with use of conventional heating. In addition, collected data cleared the intense dependence of the recycled TPA recovery on the catalyst concentration and the minimum time observed for 1.3 mol L-1 of KOH and 1.9 mol L-1 of NaOH, respectively.

Co-oxidation of p-xylene and p-toluic acid to terephthalic acid in water solvent: Kinetics and additive effects

Co-oxidation of p-xylene (PX) and p-toluic acid (p-TA) to terephthalic acid (TA) in water with Mn acetate catalyst has been studied. Mn acetate showed better catalytic activity than Co acetate and no synergism was observed between two catalysts. During the reaction, PX was transformed to p-TA while p-TA was converted to TA by a radical reaction. In the co-oxidation, radicals generated from facile PX-to-p-TA conversion would assist more difficult p-TA to TA conversion. Addition of CO 2 in the oxygen promoted the TA formation and suppressed the CO 2 formation from the combustion of reactants. Additional transition metals such as Ni and Ti also promoted the catalytic activity of Mn catalyst. Furthermore, a synergism was observed between added CO 2 and the added transition metal. Finally, the yield of terephthalic acid reached about 95% with Mn + (Ti, Ni or Cr) catalyst system and CO 2 addition.

4-CBA Concentration Soft Sensor Based on Modified Back Propagation Algorithm Embedded with Ridge Regression

Abstract Considering that there exist many factors having highly nonlinear effects on the concentration of the 4-carboxybenzaldehyde (4-CBA), which is the most important intermediate product of the oxidation of the p-xylene (PX) to terephthalic acid (TA), a modified back propagation algorithm embedded with ridge regression (BP-RR) was proposed to develop a soft sensor of the 4CBA concentration. To overcome the two main flaws of regulaz multi-layer neural networks, i.e. the tendency of overfitting and the difficulty to determine the optimal number of neurons for the hidden layer, fustly, a three-layer network is selected and the number of the hidden-layer neurons is determined according to the number of the training samples and the number of the neural network pazameters. Then, BP is applied to learn from the training samples. In sequel, the ridge regression is employed to remove the multicollinearity among the hidden-layer-node outputs and obtain the optimal weights (and thresholds) between the hidden lay...