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Terephthalic acid

Terephthalic acid is a dicarboxylic acid with the chemical formula C6H4(COOH)2.
It is an important industrial chemical used in the production of polyethylene terephthalate (PET), a widely used plastic material.
Terephthalic acid can be derived from p-xylene through oxidation, and is also found naturally in some plant species.
It plays a key role in the manufacture of various polymers, fibers, and other chemicals.
Researchers can use PubCompare.ai's AI-driven platform to optimize their terephthalic acid studies, locate the best protocols, and streamline their research process.
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Most cited protocols related to «Terephthalic acid»

1
Phthalate Temporal Variability in Men
Cited 38 times
Eleven men from our ongoing study of the relationship between environmental agents and male reproductive health agreed to participate in the phthalate variability study. Participant recruitment into the environmental agents and male reproductive health study has been previously described (Hauser et al. 2003 (link)). Briefly, men who were the partner in couples seeking fertility evaluation for inability to conceive were recruited to participate. The study site was the Massachusetts General Hospital (MGH) Andrology Laboratory, so most men resided in the New England area. At the clinic visit, each man was asked to produce a single semen sample and to collect a single spot urine sample.
For each of the 11 men in the phthalate temporal variability study, up to nine additional spot urine samples were collected during three cycles over a 92-day period. Ten of these 11 men each contributed a total of 10 urine samples (nine for the variability study and one for the male reproductive study), whereas one of the men provided a total of seven samples (including six for the variability study). Nested within each of the three cycles were three urine samples, collected on the first 3 consecutive days of each cycle. The first cycle began upon enrollment into the phthalate temporal variability study, and urine samples were collected on days 0, 1, and 2. Cycles 2 and 3 began 30 days and 90 days after cycle 1, respectively. Therefore, the nine urine samples were collected on days 0, 1, and 2 (cycle 1); days 30, 31, and 32 (cycle 2); and days 90, 91, and 92 (cycle 3).
All the urine samples were collected in a sterile specimen cup. The urine sample on day 0 was collected at the MGH Andrology laboratory. All other samples were collected at the subject’s home and frozen before overnight shipment to the Harvard School of Public Health (HSPH) on blue ice. All urine samples were then shipped frozen on dry ice from HSPH to CDC. Eight phthalate monoesters—MBzP, MBP, MEP, MEHP, monomethyl phthalate (MMP), mono-n-octyl phthalate (MOP), mono-3-methyl-5-dimethylhexyl phthalate (MINP), and monocyclohexyl phthalate (MCHP)—were measured in each spot urine sample using an analytical approach developed at the CDC (Silva et al. 2003 ). Briefly, the determination of phthalate metabolites in urine involved enzymatic deconjugation of the glucuronidated metabolites, solid-phase extraction, separation with high-performance liquid chromatography, and detection by tandem mass spectrometry. Detection limits were in the low micrograms per liter range. Reagent blanks and 13C4-labeled internal standards were used along with conjugated internal standards to increase the precision of the measurements. One method blank, two quality control samples (human urine spiked with phthalates), and two sets of standards were analyzed along with every 21 unknown urine samples. Analysts at the CDC were blind to all information concerning subjects.
Several methods adjust for urine volume (Boeniger et al. 1993 (link); Teass et al. 1998 ). Although creatinine is a frequently used form of adjustment, if a compound is excreted primarily by tubular secretion it is not appropriate to adjust for creatinine level (Teass et al. 1998 ). Although the methods of excretion of the phthalate monoesters measured in this study are unknown, terephthalic acid was found to be actively secreted by renal tubules and actively reabsorbed by the kidney (Tremaine and Quebbemann 1985 (link)). Furthermore, because organic compounds that are glucuronidated in the liver, like the phthalates, are eliminated by active tubular secretion (Boeniger et al. 1993 (link)), creatinine adjustment may not be appropriate for phthalates. Additionally, creatinine levels may be confounded by muscularity, physical activity, urine flow, time of day, diet, and disease states (Boeniger et al. 1993 (link); Teass et al. 1998 ). For these reasons, specific gravity, rather than creatinine, was used to normalize phthalate levels.
Urinary phthalate levels were normalized for dilution by specific gravity adjustment using the formula Pc = P × [(1.024 – 1)/(SG – 1)], where Pc is the specific-gravity–corrected phthalate concentration (micrograms per liter), P is the observed phthalate concentration (micrograms per liter), and SG is the specific gravity of the urine sample (Boeniger et al. 1993 (link); Teass et al. 1998 ). Specific gravity was measured using a handheld refractometer (National Instrument Company, Inc., Baltimore, MD), which was calibrated with deionized water before each measurement.
Hauser R., Meeker J.D., Park S., Silva M.J, & Calafat A.M. (2004). Temporal Variability of Urinary Phthalate Metabolite Levels in Men of Reproductive Age. Environmental Health Perspectives, 112(17), 1734-1740.
Publication 2004
2
Protein Oxidation by Hydroxyl Radicals
Cited 8 times
Protein samples with hydroxyl radical dosimeter was oxidized using a 248 nm GAM EX100 KrF excimer laser to photolyze hydrogen peroxide as described previously.3 (link) Each reaction was carried out in a 20 μL volume with a final concentration of 20 μM protein or peptide, a dosimeter (5.8 mM terephthalic acid, 5 μM Alexa Fluor 488 or 1mM adenine), freshly prepared hydrogen peroxide at various concentrations, and glutamine sufficient to balance the radical scavenging characteristics of 20 mM glutamine with no dosimeter (0mM for the terephthalic acid dosimeter, 20 mM for the Alexa Fluor 488 dosimeter, or 17 mM for the adenine dosimeter). The appropriate glutamine concentrations were calculated by using the kinetics simulator Tenua to ensure that the concentration of hydroxyl radicals were decreased to 100 nM within 1 μs; see Figure S1 in Supporting Information.15 (link)–16 (link), 18 (link), 24 Tris-HCl or sodium phosphate were also added, in concentrations ranging from 0mM to 160 mM. The reaction solution was loaded into a 100 μL syringe and flowed through 100 μm i.d. fused silica tubing using a syringe pump (Harvard Apparatus, Holliston, MA, USA). The flow rate used to introduce solution to laser beam was set at 12.19 μL/min. The laser was foucused through a convex lens with 120 mm focal length (Edmunds Optics, Barrington, NJ, USA) onto the fused silica tubing located 180 mm from the lens. The excimer laser power (GAM Laser Inc., Orlando, FL, USA) at 248 nm was adjusted to ~70 mJ/pulse at a laser pulse repetition rate of 20 Hz to provide approximately 10% of the total volume remaining unirradiated to prevent multiple irradiations per volume. The capillary outflow was collected in a microcentrifuge tube containing 50 nM catalase and 20 mM methionine amide in ammonium bicarbonate buffer (50 mM, pH=7.8) to quench any remaining hydrogen peroxide and other reactive oxygen species. For terephthalic acid and Alexa Fluor 488 combined with fluorescence detection experiment, the irradiated sample solution was diluted to 1mL solution prior to fluorescence analysis. All fluorescence measurements were collected using a Shimadzu RF-5301PC spectrofluorophotometer (Kyoto, Japan). For adenine UV absorbance measurements, 2 μL of irradiated sample solution was introduced into the Thermo NanoDrop 2000c UV spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA). The absorbance of the buffer blank at 260 nm subjected to FPOP under identical conditions to the adenine-containing sample was subtracted from the adenine UV reading to correct for the UV absorbance of buffer subjected to FPOP. A control solution without photolyzation was also included in each sample set.
Xie B, & Sharp J.S. (2015). Hydroxyl Radical Dosimetry for High Flux Hydroxyl Radical Protein Footprinting Applications Using a Simple Optical Detection Method. Analytical chemistry, 87(21), 10719-10723.
Publication 2015
Adenine alexa fluor 488 Amides ammonium bicarbonate Buffers Capillaries Catalase Eye Fluorescence Glutamine Hydroxyl Radical Kinetics Lasers, Excimer Lens, Crystalline Methionine Peptides Peroxide, Hydrogen Proteins Pulse Rate Reactive Oxygen Species Silicon Dioxide sodium phosphate Staphylococcal Protein A Syringes terephthalic acid Tromethamine
3
Synthesis and Characterization of Novel Copper(II) and Silver(I) Complexes
Cited 5 times
Chemicals were purchased from commercial sources and used as received without further purification. Infrared (IR) spectra were recorded in the region 4,000–370 cm−1 on a Perkin Elmer System 2000 FT spectrometer and using anhydrous potassium bromide to form solid KBr discs. Elemental analysis (CHN) was carried out for all the complexes using a FLASH EA 1112 Series Elemental Analyser with Eager 300 operating software. Room temperature, solid state magnetic susceptibility measurements for the Cu(II) compounds, [Cu(3,6,9-tdda)].H2O and {[Cu(3,6,9-tdda)(phen)2].3H2O.EtOH}n (7), were made using a Johnson Matthey Magnetic Susceptibility Balance.
The following metal chelates were prepared using previously published methods: [Cu(ph)(phen)(H2O)2] (1) (phH2 = phthalic acid) (Kellett et al., 2012 (link)); [Cu(ph)(phen)2].3H2O.2EtOH (2) (Kellett et al., 2011 (link)); [Cu(isoph)(phen)2].6H2O.EtOH (3) (isophH2 = isophthalic acid) (Kellett et al., 2011 (link)); [{Cu(phen)2}2(terph)](terph).13.5H2O.2EtOH (4) (terphH2 = terephthalic acid) (Kellett et al., 2011 (link)); [Cu2(oda)(phen)4](ClO4)2.2.76H2O.EtOH (5) (odaH2 = octanedioic acid) (Devereux et al., 1999 (link)); [Cu(phendione)3](ClO4)2.4H2O (6) (phendione = 1,10-phenanthroline-5,6-dione) (McCann et al., 2004 (link)); [Mn(ph)(phen)(H2O)2] (8) (Devereux et al., 2000 (link)); [Mn(ph)(phen)2(H2O)].4H2O (9) (Devereux et al., 1999 (link)); [Mn2(isoph)2(phen)3].4H2O (10) (Devereux et al., 2000 (link)); {[Mn(phen)2(H2O)2]}2(isoph)2(phen).12H2O (11) (Devereux et al., 2000 (link)); [Mn(tereph)(phen)2].5H2O (12) (Leon, 2000 ); [Mn2(oda)(phen)4(H2O)2][Mn2(oda)(phen)4(oda)2].4H2O (13) (Casey et al., 1994 (link)); {[Mn(3,6,9-tdda)(phen)2].3H2O.EtOH}n (14) (3,6,9-tddaH2 = 3,6,9-trioxaundecanedioic acid) (McCann et al., 1997 (link)); [Ag(phendione)2]ClO4 (15) (McCann et al., 2004 (link)); [Ag(phen)2]ClO4 (17) (McCann et al., 2004 (link)) and [Ag2(phen)3(udda)].3H2O (18) (uddaH2 = undecanedioic acid) (Thornton et al., 2016 (link)). The novel complexes, {[Cu(3,6,9-tdda)(phen)2].3H2O.EtOH}n (7) and [Ag2(3,6,9-tdda)(phen)4].EtOH (16), were synthesized using the two-step procedures outlined below. The preparation of all silver compounds was conducted in the absence of light and the products were stored in the dark.
{[Cu(3,6,9-tdda)(phen)2].3H2O.EtOH}n(7). Step (i): Copper(II) acetate hydrate (1.50 g; 7.51 mmol) was dissolved in ethanol (50 mL) and the solution was added to an ethanolic solution (25 mL) of 3,6,9-trioxaundecanedioic acid (3,6,9-tddaH2) (2.84 g; 8.95 mmol). The light-green suspension was refluxed for 1 h, and after cooling to room temperature the light-green solid, [Cu(3,6,9-tdda)].H2O, was filtered off, washed with cold ethanol and air dried. Yield: 1.88 g (82.97%). % Calculated: C: 31.84, H: 4.68. % Found: C: 32.20, H: 4.60. IR (KBr) νmax: 3280, 2930, 1585, 1430, 1330, 1250, 1130, 1090, 1055, 965, 920, 840, 720, 475 cm−1. μeff: 1.93 B.M. Solubility: soluble in H2O, MeOH, EtOH and insoluble in CHCl3, ethyl acetate and acetone. Step (ii): [Cu(3,6,9-tdda)].H2O (1.00 g; 3.31 mmol) and phen (2.39 g; 13.26 mmol) were dissolved together in ethanol (50 mL) and the resulting dark-green mixture was refluxed for 2 h. The suspension was cooled and the green solid, {[Cu(3,6,9-tdda)(phen)2]3H2O.EtOH}n(7), was filtered off, washed with cold ethanol and air dried. Yield: 1.63 g (66.09%). % Calculated: C: 54.87, H: 5.42, N: 7.53. % Found: C: 54.65, H: 5.63, N: 7.39. IR (KBr) νmax: 3982, 3415, 3041, 2901, 1989, 1752, 1618, 1587, 1513, 1421, 1320, 1252, 1221, 1121, 1090, 1077, 1011, 934, 893, 847, 770, 720, 704, 643, 619, 603, 573, 555, 507, 426 cm−1. μeff: 1.92 B.M. Solubility: soluble in H2O, MeOH, EtOH and insoluble in ethyl acetate and acetone.
[Ag2(3,6,9-tdda)(phen)4].EtOH (16). Step (i): Silver(I) acetate (3.00 g; 17.97 mmol) was dissolved in ethanol (30 mL) and the solution was added to an ethanolic solution (25 mL) of 3,6,9-trioxaundecanedioic acid (3,6,9-tddaH2) (2.84 g; 8.95 mmol) and the orange-brown suspension refluxed for 3 h. After cooling to room temperature, the light orange-brown powder, [Ag2(3,6,9-tdda].2H2O, was filtered off, washed with cold ethanol and then air dried. Yield: 3.79 g (44.69%). % Calculated: C: 20.36, H: 2.56. % Found: C: 20.34, H: 2.51. IR (KBr) νmax: 3425, 2896, 1614, 1406, 1116 cm−1. 1H NMR: (D2O) δ = 3.81 (s, 4H), 3.56 (s, 8H). Solubility: soluble in hot H2O and hot DMSO. Step (ii): [Ag2(3,6,9-tdda].2H2O (0.50 g; 1.06 mmol) and phen (0.827 g; 4.589 mmol) were dissolved together in ethanol (40 mL) and the mixture refluxed overnight. After cooling to room temperature the mixture was placed in an ice bath. Green [Ag2(3,6,9-tdda)(phen)4].EtOH (16) precipitated and was filtered off, washed with cold ethanol and air dried. Yield: 0.83 g (65.10%). % Calculated: C: 57.92, H: 4.19, N: 9.32. % Found: C: 57.75, H: 5.16, N: 9.02. IR (KBr) νmax: 3380, 3046, 2905, 1978, 1804, 1618, 1585, 1509, 1421, 1322, 1263, 1215, 1121, 1077, 1018, 932, 890, 838, 726, 621, 465, 413 cm−1. 1H NMR (500 MHz, DMSO-d6, 313 K, TMS) δ = 9.12(8H, s), 8.63 (8H, d), 8.08 (8H, s), 7.91 (8H, dd), 3.74 (4H, s), 3.57 (8H, dd). 13C NMR (125 MHz, DMSO-d6, 313 K, TMS) δ = 173.41, 151.28, 143.57, 138.03, 129.24, 127.37, 124.74, 71.44, 70.42, 69.74. Solubility: soluble in H2O, MeOH, EtOH and insoluble in ethyl acetate and acetone.
Gandra R.M., Mc Carron P., Fernandes M.F., Ramos L.S., Mello T.P., Aor A.C., Branquinha M.H., McCann M., Devereux M, & Santos A.L. (2017). Antifungal Potential of Copper(II), Manganese(II) and Silver(I) 1,10-Phenanthroline Chelates Against Multidrug-Resistant Fungal Species Forming the Candida haemulonii Complex: Impact on the Planktonic and Biofilm Lifestyles. Frontiers in Microbiology, 8, 1257.
Publication 2017
4
Dye Degradation by Plasma-Generated RONS
Cited 4 times
A 1 g/L stock solution of MB, MO and CR is prepared by dissolving the required amount of analytical grade dye in Millipore water. The experimental solutions (200 mg/L) are obtained by diluting the stock solution in accurate proportions. Degradation of the dyes is monitored via a UV-Vis spectrophotometer S-3100, with a wavelength resolution, accuracy, and reproducibility of 0.95 nm, ±0.5 nm and ±0.02 nm, respectively. The absorption is measured at 660 nm, 460 nm, and 500 nm for MB, MO and CR, respectively, and the degradation percentage and energy efficiency (g/kWh) are calculated using a previously reported method22 (link). The H2O2 concentration is measured using titanyl ions34 (link)35 (link) in the presence of sodium azide to control the H2O2 degradation by nitrites. The NO concentration is detected using 4-amino-5-methylamino-2′,7′-difluorofluorescein (DAF-FM)36 , and the OH concentration is measured using terephthalic acid (20 mM) by means of the procedure described earlier in ref. 37 (link). The NO2− concentration is measured using Griess reagent supplied by Aldrich Chemical Co. (USA), whereas the NO3− concentration is obtained using the Acorn Series ION 6 meter (pH/mV/°C Meter), nitrate electrode, from Oakton Instruments, USA. After exposure of both plasmas (generated from the ID- and D-APPJs) to deionized (DI) water and the three different solutions, the pH and temperature of the water and of the solutions are measured using a pH meter (Eutech Instruments, Singapore) and Infrared (IR) camera (Fluke Ti100 Series Thermal Imaging Cameras, UK). All measurements are performed in triplicate. The density of the dyes in the solution is measured using an Anton-Paar DSA 5000 with an accuracy in temperature ±0.01 K, whereas the uncertainty in the density is ±0.00005 g cm−3. Prior to the measurements, the instrument is calibrated with DI water and dry air as standards at 293.15 K38 (link)39 (link)40 (link).
The filtrates are measured by a high performance liquid chromatography method using HPLC-UV (Agilent 1200, USA) containing a ZORBAX SB-C18 column (2.1 mm 150 mm, 5 mm). 30/70 (v/v) of acetonitrile/10% acetic acid is used as the mobile phase for MB, MO and CR in HPLC-UV. The analysis is performed at 25 °C with 0.8 mL/min flow rate of an injected 100 mL volume of sample. The final degradation products are analyzed using LC[QTOF]MSMS. The LCMSMS consists of a TripleTOF 5600 (quadrupole-Time of flight) tandem mass spectrometer (ABSciex). The TOF mass range is 40,000 m/z with a maximum resolution power of MS 25,000@m/z 195, MS/MS 35,000@m/z 965, and a mass accuracy of <0.05 ppm.
To understand the effect of various RONS, generated by the plasma, on the decolorization/degradation of the dyes, we also treat the dye solutions with ozone and nitric oxide. Ozone (O3) is generated using an ozone machine (Model: LAB-II, Company: OZONE TECH). Applying this technique we generate 5580 ppm of ozone, the concentration of which is measured using the detection tubes obtained from Gastec (Product No. 18M and 18L, Gastec, Japan). These tubes contain a reagent which changes its color after coming into contact with the ozone. Note that these tubes have an accuracy of about ±10% due to the presence of other interfering species. Nitric oxide (NO) is generated using a microwave plasma system. This system consists of a magnetron, waveguide component (WR-340 for 2.45 GHz) and a microwave plasma torch apparatus, as described in our earlier work41 , which can generate 5712 ppm of NO.
Attri P., Yusupov M., Park J.H., Lingamdinne L.P., Koduru J.R., Shiratani M., Choi E.H, & Bogaerts A. (2016). Mechanism and comparison of needle-type non-thermal direct and indirect atmospheric pressure plasma jets on the degradation of dyes. Scientific Reports, 6, 34419.
Publication 2016
5
Synthesis and Characterization of Terephthalate Compounds
Cited 3 times
Identity and purity of all synthesized compounds was verified by NMR. 1H spectra were measured in DMSO-d6 on a Bruker Avance II 300 equipped with a 5 mm PABBO BB-1H/D Z-GRD Z104275/0398 probehead at 25–28 °C (Fig. S7a-f). For the calibration of the measurements tetramethylsilane was used.
Bishydroxyethyl terephthalate (BHET): BHET was synthesized from a PET bottle by alcoholysis with ethylene glycol. Twenty grams PET and 0.2 g anhydrous sodium acetate were refluxed in 120 mL ethylene glycol for 8 h and afterwards cooled overnight. 120 mL H2O was added and filtration was performed at 4 °C. The product was washed with 20 mL cold H2O and extracted several times with hot H2O. BHET appeared as white needles (18 g (68%), Mp 210–212 °C).
Bishydroxyethyl terephthalic acid amide (BHETA): BHETA was synthesized from PET by aminolysis with 2-amino ethanol. Twenty grams PET and 0.2 g anhydrous sodium acetate were refluxed in 120 mL ethanolamine for 8 h and afterwards cooled overnight. 120 mL H2O was added and filtration was performed at 4 °C. The product was washed with 20 mL cold H2O and recrystallized twice with 100 mL hot H2O. BHETA appeared as lightly rose needles (20 g (76%), Mp 240–243 °C).
Dimethyl terephthalate (DMT): DMT was synthesized by esterification of terephthaloyl chloride with methanol. 25 mmol terephthaloyl chloride was reacted with 30 mL methanol at RT and then refluxed for 3 h. After distilling the methanol and drying at 60 °C, 4.08 g was obtained (Mp 144–148 °C). Washing with 0.5 M KOH and water did not change the melting point.
Monohydroxyethyl terephthalate (MHET): MHET was synthesized from BHET by partial hydrolysis with KOH. 8.7 mmol BHET was reacted with 8.4 mmol KOH in 18 mL MgSO4-dried ethylene glycol at 110–130 °C for 2.5 h. Thirty milliliters H2O was added and the mixture was extracted three times with 5 mL CHCl3. The aqueous phase was adjusted to pH 3 with 25% HCl and filtered at 4 °C. After two extraction steps with 30 mL hot H2O and filtration at 4 °C, the precipitate was dried at 60 °C (0.56 g (30%), Mp 185–190 °C).
Monohydroxyethyl terephthalic acid amide (MHETA): MHETA was synthesized by partial amidation of terephthaloyl chloride with ethanolamine. 150 mmol NaOH and 50 mmol ethanolamine in 50 mL H2O were added dropwise within 1 h to 50 mmol terephthaloyl chloride in 50 mL H2O at 0 °C. The reaction was performed for another 2 h at 0 °C and 2 h under reflux, followed by hot filtration. The pH was adjusted to 3 with 25% HCl. The obtained suspension was filtered cold and the filtrate was washed with 20 mL cold water. The product was recrystallized from 100 mL hot H2O to yield shiny crystals (2.4 g (23%), Mp 209–212 °C).
Mono-4-nitrophenyl terephthalate (MpNPT): MpNPT was synthesized by esterification of terephthaloyl chloride with 4-nitrophenolate. 50 mmol terephthaloyl chloride and 50 mmol sodium 4-nitrophenolate were suspended in 50 mL diethylether and reacted for 2 h at 0 °C, then at RT overnight. 2.5 g Na2CO3 and 4.5 g NaHCO3 in 50 mL H2O were added and reacted at RT for 10 h. The pH was adjusted to 8.5 with NaOH. The insoluble fraction was further extracted with a total of 2.5 g Na2CO3 and 2.5 g NaHCO3 in 100 mL H2O and then washed until a neutral pH. MpNPT was precipitated with HCl at pH 3 and washed twice with 50 mL 0.1 M HCl and then until a neutral pH. MpNPT was separated from contaminating bis-4-nitrophenyl terephthalate by extraction with 100 mM NaPi pH 7.4 and acid precipitation. The very faint yellow slurry was dried at 60 °C (Mp 202 °C).
Palm G.J., Reisky L., Böttcher D., Müller H., Michels E.A., Walczak M.C., Berndt L., Weiss M.S., Bornscheuer U.T, & Weber G. (2019). Structure of the plastic-degrading Ideonella sakaiensis MHETase bound to a substrate. Nature Communications, 10, 1717.
Publication 2019

Most recents protocols related to «Terephthalic acid»

1
Quantifying Terephthalic Acid in Polyesters via NMR
Not available on PMC !

Example 1

In Comparative Example 1, measurement of the PET sample is performed under the measurement condition used in NMR measurement for the purpose of quantifying the terephthalic acid terminal of a polyester.

About 3 mg of Sample-1: PET (Mn: about 14,000) was dissolved in a mixed solvent of CDCl3/HFIP-2d (volume ratio of 1:1), isopropylamine (about 0.3 mg) was added, and the 1H NMR measurement was carried out at T=50° C., thereby confirming the following peaks (see FIG. 2).

(a): δ8.09 (s, 4H)

(b): δ7.89 (d, J=8.7 Hz, 2H)

In Example 1, measurement was carried out changing the type of the sample from that of Comparative Example 5. In Comparative Example 5, Sample-3, a mixture of a PET resin with Mn of about 14,000 and terephthalic acid, was used as the sample. It is considered that the reason for the undissolution of the sample in Comparative Example 5 is because the PET resin is not dissolved well in TFEA. However, the acidity of TFEA is relatively high due to the electron withdrawing effect of the trifluoromethyl group, and therefore, the present inventors considered that, as long as it has a relatively low molecular weight, even a PET resin can be dissolved in TFEA and can be subjected to the 1H NMR measurement.

Based on the above observation, in Example 1, the sample of Comparative Example 5 was changed from Sample-3: mixture of PET (Mn: about 14,000), about 2.7 mg and terephthalic acid, about 0.1 mg to Sample-4: mixture of PET (Mn: about 1,500), about 2.7 mg and terephthalic acid, about 0.1 mg, and the 1H NMR measurement was carried out.

Specifically, Sample-4 was dissolved in a mixed solvent of CDCl3/TFEA-2d (volume ratio of 1:1), isopropylamine (about 0.3 mg) was added, and the 1H NMR measurement was carried out at T=50° C.

As a result, the 1H NMR measurement was carried out with no occurrence of undissolved sample, and the peaks of (b) and (c) were separated, as shown in FIG. 5.

(a): δ8.07 (s, 4H)

(b): δ7.90 (d, J=8.7 Hz, 2H)

(c): δ7.85 (s, 4H)

When substituting the integrated values of peaks into the following formula, “CTPA=(c)/{(a)+(b)+(b′)+(c)}×100=1.89/44.28×100=4.3”. This coincided well with the molar concentration of terephthalic acid relative to the entire aromatic rings derived from terephthalic acid in Sample-4, which is calculated from the following formula.
(the number of moles of terephthalic acid in Sample-4)/{(the number of moles of aromatic rings derived from terephthalic acid contained in the PET resin of Sample-4)+(the number of moles of terephthalic acid in Sample-4)}×100=(0.1 mg/166 g/mol)/{(2.7 mg/192 g/mol)+(0.1 mg/166 g/mol)}×100=4.3

According to the present Example, it was found that, when a PET resin sample has a relatively low molecular weight and the sample is dissolved in a mixed solvent of CDCl3/TFEA-2d, the concentration of terephthalic acid can be determined.

Example 2

In Comparative Example 2, measurement of terephthalic acid is performed under the same conditions as in Comparative Example 1. Sample-2: terephthalic acid (about 3 mg) was measured under the same conditions as in Comparative Example 1, and the following peak was confirmed (see FIG. 3).

(c): δ7.88 (s, 4H)

In Example 2, measurement was carried out changing the mixing ratios of solvents from those of Comparative Example 6. The 1H NMR measurement was carried out for (Sample-3) changing the mixing ratios of the ternary mixed solvent used in Comparative Example 6. The results are shown in Table 3.

For all of Entry No. 15 to Entry No. 19, the sample was dissolved and the peaks of (b) and (c) were separated. Also, when CTPA was determined from the integrated values of peaks, it coincided well with the molar concentration of terephthalic acid relative to the entire aromatic rings derived from terephthalic acid in (Sample-3), which is calculated from the following formula.
(the number of moles of terephthalic acid in Sample-3)/{(the number of moles of aromatic rings derived from terephthalic acid contained in the PET resin of Sample-3)+(the number of moles of terephthalic acid in Sample-3)}×100=(0.1 mg/166 g/mol)/{(2.7 mg/192 g/mol)+(0.1 mg/166 g/mol)}×100=4.3

TABLE 3
CTPA
CDCl3/TFEA-Dissolu-Separationcalculated
2d/HFIP-2dtion ofof peaks ofvalue
Entry No.A:B:Csample(b) and (c)[mol %]
1 (Comparative1:0:1∘x—
Example 3,
reshown)
9 (Comparative1:1:0x∘—
Example 4,
reshown)
11 (Comparative1:1:1∘x—
Example 6,
reshown)
13 (Comparative1:3:1Δx—
Example 6,
reshown)
15 (Comparative3:1:1∘Δ—
Example 6,
reshown)
164:1:1∘∘4.1
173:2:1∘∘4.5
182:2:1∘∘4.3
193:3:1∘∘4.2
202:3:1∘∘4.3

Here, in the solvent according to the above embodiment, the mixing ratio of chloroform, 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol is defined as A:B:C. In addition, as shown in FIG. 6, A/C is taken on the horizontal axis and B/C is taken on the vertical axis, and the points where (b) and (c) were separated are marked with “0”, and the points where they were not separated and where dissolution of the sample was insufficient are marked with “x”. From FIG. 6, for sufficient separation of (b) and (c), it is necessary to satisfy the conditions “A/C>1, 8>(A+B)/C>3 and 5>(A−B)/C>−2”.

Example 3

In Comparative Example 3, measurement of a mixed sample of PET and terephthalic acid is performed under the same conditions as in Comparative Examples 1 and 2. When Sample-3: mixture of PET (Mn: about 14,000), about 2.7 mg and terephthalic acid, about 0.1 mg was measured under the same conditions as in Comparative Examples 1 and 2, the peaks of (b) and (c) were overlapped.

In Comparative Example 1, the peaks of the doublet in (b) decline on the right shoulder, whereas in Comparative Example 3, (c) overlaps with the peak on the side of higher magnetic field of the doublet, resulting in a rise in the right shoulder.

Note that there has been no reported case so far indicating that the peaks of (b) and (c) are overlapped when the sample is dissolved in a mixed solvent of [CDCl3/HFIP-2d (volume ratio of 1:1)] under the present measurement condition, isopropylamine (about 0.3 mg) is added, and the 1H NMR measurement is performed at T=50° C. Through Comparative Examples 1 to 3, the present inventors revealed for the first time that separation of the peaks of (b) and (c) is a problem for quantifying terephthalic acid with the 1H NMR measurement (see FIG. 4).

(a): δ8.11 (s, 4H)

(b): δ7.91 (d, J=9.3 Hz, 2H)

(c): δ7.89 (s, 4H)

In Example 3, measurement was carried out changing the type of the organic base and the measurement temperature from those of Example 2. Based on Entry No. 18 [CDCl3/TFEA-2d/HFIP-2d (2:2:1) was used as the mixed solvent], the measurement was carried out changing the type of the organic base and the measurement temperature. The results are shown in Table 4.

For all of Entry No. 21 to Entry No. 26, the sample was dissolved and the peaks of (b) and (c) were separated. Also, when CTPA was determined from the integrated values of peaks, it coincided well with the molar concentration of terephthalic acid relative to the entire aromatic rings derived from terephthalic acid in (Sample-3), 4.3.

It was confirmed that the organic base to be added is not limited to isopropylamine (primary amine) and may be diethylamine (secondary amine), N-ethyldiisopropylamine (tertiary amine) or pyridine (heterocyclic amine). It can be readily analogized that n-propylamine, n-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, diisopropylamine, dibutylamine, triethylamine, tributylamine, aziridine, pyrrolidine, pyrrole, piperidine, imidazole, triazole, pyrimidine and the like are also available.

In addition, with respect to the measurement temperature, based on the fact that the boiling point of each solvent is as follows: chloroform 61° C.; TFEA 72° C.; and HFIP 58° C., and also the solvents are easily admixed at a higher temperature, the measurement was also performed at 55° C., 40° C. and 30° C. and it was confirmed that the measurement may be carried out at any of these temperatures.

TABLE 4
SeparationCTPA
Measurementof peakscalculated
temperatureof (b)value
Entry No.Organic base[° C.]and (c)[mol %]
18 (Example 2,Isopropylamine50∘4.3
reshown)
21Diethylamine50∘4.5
22N-Ethyldiiso-50∘4.2
propylamine
23Pyridine50∘4.1
24Isopropylamine55∘4.1
25Isopropylamine40∘4.3
26Isopropylamine30∘4.4

When quantification of the terephthalic acid content of a polyester or of decomposition products of a polyester is carried out with liquid chromatography, it takes several tens of minutes to measure a single sample, and if startup and shutdown operations of the device are included as well, it takes several hours to perform the overall quantification operation. As a measurement technology that is simpler than the liquid chromatography, mention may be made of NMR.

In the NMR measurement, it is necessary to dissolve the sample in a solvent, and in the polyester measurement, a mixed solvent of 1,1,1,3,3,3-hexafluoro-2-propanol and chloroform, which dissolves a polyester well, is commonly used. However, the present inventors confirmed that, with the NMR measurement using the above mixed solvent, it is difficult to separate the peak of terephthalic acid from those of other components and terephthalic acid cannot be quantified.

2,2,2-trifluoroethanol is a solvent that hardly dissolves polyesters and is generally not used in the NMR measurement for polyesters. However, in embodiments of the present invention, the present inventors focused on the fact that 2,2,2-trifluoroethanol has relatively high acidity, and considered that it may be applicable as the measurement solvent for polyesters if it is used as a mixed solvent. Then, by using a mixed solvent that contains 2,2,2-trifluoroethanol, adding an organic base thereto, and carrying out the measurement, simple quantification of the terephthalic acid content of a polyester was achieved.

Although 2,2,2-trifluoroethanol hardly dissolves polyesters, it was possible to perform the present measurement with a mixed solvent of 2,2,2-trifluoroethanol and chloroform as long as the polyester has a relatively low molecular weight. In addition, with respect to a polyester that has a larger molecular weight than that and is not dissolved in a mixed solvent of 2,2,2-trifluoroethanol and chloroform, although a mixed solvent that is normally used for the NMR measurement is a binary mixed solvent, it was confirmed that the measurement can be carried out by using a ternary mixed solvent of 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoro-2-propanol and chloroform in embodiments of the present invention. The ternary mixed solvent has a problem in the solubility of the sample or the separation of peaks depending on the mixing ratio of solvents, and therefore, embodiments of the present invention revealed a desired mixing ratio.

As described above, since embodiments of the present invention use a solvent that contains chloroform and 2,2,2-trifluoroethanol and has an organic base added thereto, measurement of the terephthalic acid content of a polyester or of decomposition products of a polyester is enabled through a nuclear magnetic resonance spectroscopy aiming at hydrogen atoms.

Note that the present invention is not limited to the embodiments described above, and it is obvious that those having ordinary skill in the art can make many modifications and combinations without departing from the technical idea of the invention.

Example 4

In Comparative Example 4, measurement is carried out changing the parameters of solvent mixing ratio, type of organic base, temperature and the like from those of Comparative Example 3.

Sample-3: mixture of PET (Mn: about 14,000), about 2.7 mg and terephthalic acid, about 0.1 mg was measured changing the parameters of solvent mixing ratio, type of organic base, temperature and the like from those of Comparative Example 3. Whether (b) and (c) can be separated or not in each measurement condition is shown in the following Table 1.

TABLE 1
Table 1 - 1H NMR measurement results
with mixed solvent of CDCl3/HFIP-2d
Separation
CDCl3/Measurementof peaks
HFIP-2dtemperatureof (b)
Entry No.A:COrganic base[° C.]and (c)
1 (Comparative1:1Isopropylamine50x
Example 3,
reshown)
21:4Isopropylamine50x
34:1Isopropylamine50x
41:1Diethylamine50x
51:1N-Ethyldiiso-50x
propylamine
61:1Pyridine50x
71:1Isopropylamine55x
81:1Isopropylamine40x
91:1Isopropylamine25x

Example 5

In Comparative Example 5, measurement is carried out changing the types of solvents from those of Comparative Example 4. Changing from the mixed solvent of CDCl3/HFIP-2d (1:1) used in Comparative Example 3, a mixed solvent of CDCl3/TFEA-2d (1:1) was used to measure Sample-3: mixture of PET (Mn: about 14,000), about 2.7 mg and terephthalic acid, about 0.1 mg.

TFEA is a solvent that hardly dissolves PET, and is thus not used for the purpose of PET measurement in the NMR measurement, which requires dissolution of the sample. However, the present inventors focused on the fact that TFEA is an organic solvent that is not as acidic as HFIP but has high acidity, and performed Comparative Example 5 in order to confirm the effect of TFEA on the peak shift.

In Comparative Example 5, the mixed solvent was added to Sample-3 and isopropylamine was then added thereto, but a residue remaining undissolved was present at this stage. Therefore, this measurement sample was heated to about 50° C. for about 10 minutes, but the residue still remained. As such, when the 1H NMR measurement was carried out in the presence of solid components remaining undissolved, measurement data was obtained for a dissolved part of the sample, and it was confirmed that the peaks of (b) and (c) can be separated.

Note that it is necessary to dissolve the sample in the 1H NMR measurement, and in the above measurement, while a dissolved part of the sample was measured, the PET resin remaining undissolved was not measured. Therefore, it is inappropriate to calculate the concentration of terephthalic acid based on the obtained spectrum.

(a): δ8.09 (s, 4H)

(b): δ7.90 (d, J=8.7 Hz, 2H)

(c): δ7.85 (s, 4H)

Hereinafter, Examples to which the present invention was applied will be described.

Example 6

In Comparative Example 6, measurement is carried out changing the types of solvents and the mixing ratio thereof from those of Comparative Example 5. In Comparative Example 5, the mixed solvent of CDCl3/TFEA-2d (volume ratio of 1:1) was used and the peaks of (b) and (c) were separated, but the PET resin in Sample-3 was not dissolved in the mixed solvent. Since TFEA hardly dissolves PET resins, the present inventors decided to investigate, as the mixed solvent, a ternary mixed solvent in which HFIP, which can dissolve PET resins, is also mixed into CDCl3 and TFEA. In the NMR measurement, it is most common to use a solvent with a single composition as the measurement solvent, and when there is a problem in the solubility of the sample or the like, a binary mixed solvent may be used, but it is not common to use a ternary mixed solvent.

The results of measurements at different mixing ratios of the solvents are shown in Table 2. In all conditions, the organic base is isopropylamine and the measurement temperature is 50° C.

In Entry No. 11, CDCl3/TFEA-2d/HFIP-2d (1:1:1) was used, and it was difficult to separate (b) from (c). Therefore, in Entry Nos. 11 and 12, the proportion of TFEA was increased in order to enhance the effect of peak shifting by TFEA, but the peaks of (b) and (c) were not separated. In Entry No. 13, it was confirmed that the solubility of the sample was decreased, and therefore, it was determined that it is inappropriate to further increase the proportion of TFEA, which decreases the solubility of the PET resin.

Next, in Entry Nos. 14 and 15, the proportion of chloroform in the mixed solvent was increased. In No. 14, the peaks of (b) and (c) were not separated, but in No. 15, two peaks were observed to be slightly apart from each other, albeit incompletely, compared to No. 11 and others.

TABLE 2
Table 2 - 1H NMR measurement results with
mixed solvent of CDCl3/TFEA-2d/HFIP-2d
CDCl3/TFEA-Separation
2d/HFIP-2dDissolutionof peaks of
Entry No.A:B:Cof sample(b) and (c)
1 (Comparative1:0:1∘x
Example 3,
reshown)
10 (Comparative1:1:0x∘
Example 4,
reshown)
111:1:1∘x
121:2:1∘x
131:3:1Δx
142:1:1∘x
153:1:1∘Δ

US11867647B2. Method for measuring terephthalic acid content and solvent for use in measurement (2024-01-09). Nippon Telegraph and Telephone Corporation [JP]. Inventors: Azusa Ishii [JP], Takashi Miwa [JP].
Patent 2024
2
Dimethyl Terephthalate Synthesis from PET
Not available on PMC !

Example 2

Polyethylene terephthalate (1000 g) was introduced in a reactor. DMSO (500 g) was added and the mixture was stirred at room temperature and at atmospheric pressure for about 40 mins. Sodium methoxide (45 g) and methanol (550 g) were then added to the reaction mixture was stirred and heated at 55° C. for 120 mins.

The reaction mixture was then filtered and the filter cake was washed with methanol. The filter cake was then melted and filtered at 140° C. to remove any unreacted materials. The filtered dimethyl terephthalate was then distilled under vacuum at 200° C. The liquid recovered from the filtration was distilled to recover the solvents and the mono ethylene glycol.

Dimethyl terephthalate was obtained in 89% yield.

US11866404B2. Terephthalic acid esters formation (2024-01-09). 9449710 CANADA INC. [CA]. Inventors: Adel Essaddam [CA], Fares Essaddam [CA].
Patent 2024
Atmospheric Pressure dimethyl 4-phthalate Esters Filtration Glycol, Ethylene Methanol Polyethylene Terephthalates Sodium Methoxide Solvents Sulfoxide, Dimethyl terephthalic acid Vacuum
3
Synthesis of Dimethyl Terephthalate from Polyethylene Terephthalate
Not available on PMC !

Example 1

Polyethylene terephthalate (1000 g) was introduced in a reactor. Dichloromethane (500 g) was added and the mixture was stirred at room temperature and at atmospheric pressure for about 40 mins. Sodium methoxide and methanol were then added to the reaction mixture was stirred and heated for 120 mins (see table below for amounts, time, and temperature details).

The reaction mixture was then filtered and the filter cake was washed with methanol. The filter cake was then melted and filtered at 140° C. to remove any unreacted materials. The filtered dimethyl terephthalate was then distilled under vacuum at 200° C. The liquid recovered from the filtration was distilled to recover the solvents and the mono ethylene glycol.

Weight ofReactionReaction
Weight ofsodiumtimetemperatureYield
methanol (g)methoxide (g)(min)(° C.)(%)
Example667321205590
1A
Example600541205090
1B
Example580501206090
1C

US11866404B2. Terephthalic acid esters formation (2024-01-09). 9449710 CANADA INC. [CA]. Inventors: Adel Essaddam [CA], Fares Essaddam [CA].
Patent 2024
Atmospheric Pressure dimethyl 4-phthalate Esters Filtration Glycol, Ethylene Methanol Methylene Chloride Polyethylene Terephthalates Sodium Sodium Methoxide Solvents terephthalic acid Vacuum
4
Monitoring Hydroxyl Radical Formation in BP-Au NPs
The hydroxyl (•OH)-radical-formation ability of the BP-Au NPs was monitored through the TA test. To do so, 1 mM (50 µL) of an aqueous solution of TA was mixed with the BP-Au NP solution (50 µL) and kept at room temperature for 10 min. Then, an H2O2 solution (10 mM, 50 µL) was added to it and after 30 min, the fluorescence intensity of the reaction product was recorded using a fluorescence spectrophotometer.
Alsulami T, & Alzahrani A. (2024). Enhanced Nanozymatic Activity on Rough Surfaces for H2O2 and Tetracycline Detection. Biosensors, 14(2), 106.
Publication 2024
5
Recycling PET Waste into Terephthalic Acid
Discarded polyethylene terephthalate (PET) bottle wastes were collected from local canteen and used for preparing terephthalic acid (TPA). Sodium hydroxide (NaOH), sodium dodecyl sulfate (SDS), ethanol, hydrochloric acid (HCl), zinc acetate (Zn(CH3COO)2), tetrahydrofuran (THF), dimethyl formamide (DMF), polyvinyl chloride (PVC, Mw~120,000), and polymethylmethacrylate (PMMA, Mw~350,000), were purchased from Sigma Aldrich. Body gel scrub was purchased from a local market. All chemicals were at the highest purity level (99.99%) available in the market and used as received. Deionized (DI) water was used for preparing the solutions and conducting experiments.
Chinglenthoiba C., Mahadevan G., Zuo J., Prathyumnan T, & Valiyaveettil S. (2024). Conversion of PET Bottle Waste into a Terephthalic Acid-Based Metal-Organic Framework for Removing Plastic Nanoparticles from Water. Nanomaterials, 14(3), 257.
Publication 2024

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