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Test methods of purified terephthalic acid (PTA) for industrial use - Part 5: Determination of acid number
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Test method of purified terephthalic acid (PTA) for industrial use -- Part 5: Determination of acid number
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Basic data
| Standard ID | GB/T 30921.5-2025 (GB/T30921.5-2025) |
| Description (Translated English) | Test methods of purified terephthalic acid (PTA) for industrial use - Part 5: Determination of acid number |
| Sector / Industry | National Standard (Recommended) |
| Classification of Chinese Standard | G16 |
| Classification of International Standard | 71.080.40 |
| Word Count Estimation | 8,870 |
| Date of Issue | 2025-12-02 |
| Date of Implementation | 2026-07-01 |
| Older Standard (superseded by this standard) | GB/T 30921.5-2016 |
| Issuing agency(ies) | State Administration for Market Regulation, Standardization Administration of China |
GB/T 30921.5-2025: Test methods of purified terephthalic acid (PTA) for industrial use - Part 5: Determination of acid number
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
ICS 71.080.40
CCSG16
National Standards of the People's Republic of China
Replaces GB/T 30921.5-2016
Test methods for industrial purified terephthalic acid (PTA)
Part 5.Determination of Acid Value
Published on 2025-12-02
Implemented on July 1, 2026
State Administration for Market Regulation
The State Administration for Standardization issued a statement.
Foreword
This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1.Structure and Drafting Rules of Standardization Documents".
Drafting.
This document is Part 5 of GB/T 30921, "Test Methods for Purified Terephthalic Acid (PTA) for Industrial Use". GB/T 30921 has been issued.
The following parts were laid out.
---Part 1.Determination of p-carboxybenzaldehyde (4-CBA) and p-methylbenzoic acid (p-TOL) content;
---Part 2.Determination of Metal Content;
---Part 3.Determination of water content;
---Part 4.Determination of Titanium Content. Diantipyrin Methane Spectrophotometric Method;
---Part 5.Determination of Acid Value;
---Part 6.Determination of Particle Size Distribution;
---Part 7.Determination of b* value using a colorimeter.
This document replaces GB/T 30921.5-2016 "Test Methods for Industrial Purified Terephthalic Acid (PTA) - Part 5.Determination of Acid Value".
Compared with GB/T 30921.5-2016, the main technical changes in the revised version are as follows, except for structural adjustments and editorial modifications.
---The scope has been changed (see Chapter 1, Chapter 1 of the.2016 edition);
---The terminology and definition of acid value have been changed (see 3.1,.2016 edition of 3.1);
---Added content related to potentiometric titration (see Chapters 5 and 7);
---Added quality assurance and control (see Chapter 8).
Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.
This document was proposed by the China Petroleum and Chemical Industry Federation.
This document is under the jurisdiction of the National Technical Committee on Chemical Standardization (SAC/TC63).
This document was drafted by. China Petroleum & Chemical Corporation Yangzi Petrochemical Co., Ltd., China Petroleum & Chemical Research Institute Co., Ltd., and China Petroleum & Chemical Corporation.
Petrochemical Yizheng Chemical Fiber Co., Ltd., Sichuan Energy Investment Chemical New Materials Co., Ltd., and Metrohm China Ltd.
The main drafters of this document are. Shao Qiang, Ye Huili, Yu Hao, Wang Chuan, Li Chengwei, Zhong Xuanmeng, Lei Zhiwen, Ding Daxi, Xu Peng, Song Ling, and Gu Yufeng.
Li Dingsong, Yang Chao, Liu Binhua.
This document was first published in.2016, and this is its first revision.
Introduction
GB/T 30921 "Test Methods for Purified Terephthalic Acid (PTA) for Industrial Use" is equivalent to GB/T 32685 "Purified Terephthalic Acid (PTA) for Industrial Use".
The supporting methodology standard is proposed to consist of seven parts.
---Part 1.Determination of p-carboxybenzaldehyde (4-CBA) and p-methylbenzoic acid (p-TOL) content. Includes high performance liquid chromatography.
The method and high-performance capillary electrophoresis were used to describe the properties of p-carboxybenzaldehyde (4-CBA) in industrial purified terephthalic acid (PTA).
Test methods for determining the content of p-toluic acid (p-TOL).
---Part 2.Determination of Metal Content. This includes flame atomic absorption spectrophotometry, graphite furnace atomic absorption spectrophotometry, and electrochemical atomic absorption spectrophotometry.
Inductively coupled plasma atomic emission spectrometry (ICP-AES). The purpose is to describe the experimental method for determining the metal content of industrial purified terephthalic acid (PTA).
method.
---Part 3.Determination of Water Content. This includes Karl Fischer volumetric method and thermogravimetric method. The aim is to describe the water content of industrially purified terephthalic acid.
Test method for determining the water content of formic acid (PTA).
---Part 4.Determination of Titanium Content using Diantipyrrolidone Spectrophotometric Method. The purpose is to describe the process of determining the content of purified terephthalic acid for industrial use.
Test method for determining titanium content (PTA).
---Part 5.Determination of Acid Value. This includes indicator methods and potentiometric titration. The purpose is to describe the acid value of industrially purified terephthalic acid.
Test methods for determining the value.
---Part 6.Determination of Particle Size Distribution. This includes air jet sieving, laser diffraction, and dynamic imaging methods. The aim is to describe...
Test method for determining the particle size distribution of industrial purified terephthalic acid (PTA).
---Part 7.Determination of b* value using a colorimeter. The purpose is to describe the test method for determining the b* value of industrial purified terephthalic acid (PTA).
Verification method.
Test methods for industrial purified terephthalic acid (PTA)
Part 5.Determination of Acid Value
Warning. This document is not intended to address all security issues related to its use. Users are responsible for taking appropriate safety and health precautions.
Health measures shall be implemented and compliance with relevant national laws and regulations shall be ensured.
1 Scope
This document describes the indicator method and potentiometric titration method for determining the acid value of industrial purified terephthalic acid (PTA).
This document applies to the determination of the acid value of purified terephthalic acid (PTA) for industrial use.
2 Normative references
The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.
For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies.
This document.
GB/T 601 Preparation of Standard Titration Solutions for Chemical Reagents
GB/T 3723 General Safety Rules for Sampling of Industrial Chemical Products
GB/T 6679 General Rules for Sampling of Solid Chemical Products
GB/T 6682 Specifications and test methods for water used in analytical laboratories
GB/T 8170 Rules for rounding off numerical values and the representation and determination of limiting values
JJG814-2015 Verification Procedure for Automatic Potentiometric Titrator
3 Terms and Definitions
The following terms and definitions apply to this document.
3.1
acid number
The number of milligrams of potassium hydroxide required to neutralize 1g of PTA sample.
Note. The unit is milligrams per gram (mg/g).
4.Indicator Method
4.1 Method Summary
A certain amount of PTA sample was dissolved in an appropriate amount of dimethyl sulfoxide, and an appropriate amount of water was added. Phenolphthalein was used as an indicator, and the solution was diluted with hydroxide hydrate.
Titrate with sodium standard solution until the endpoint is reached (pink color). Calculate the acid value of the sample from the volume of sodium hydroxide standard solution consumed.
4.2 Reagents and Materials
4.2.1 Unless otherwise specified, all reagents used are of analytical grade, and the water used in the experiment meets the requirements for Grade III water in GB/T 6682.
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