Sequential Catalyst System for Terephthalic Acid Esterification
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Solution Overview
Problem
Current methods for esterification of terephthalic acid to produce PVC plasticizers face challenges such as high energy consumption, long reaction times, high temperatures, and pressures, as well as issues with by-product formation, selectivity, and the quality of the final product, including color and acid number, which affect the product's durability and optical properties.
Innovation Solution
A method involving the sequential addition of a metal-containing catalyst followed by an acid catalyst in a single reaction vessel, optimizing conditions to achieve 100% conversion of terephthalic acid with reduced by-products, low acid number, and low color, using a total catalyst system not exceeding 0.7% by weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal-containing catalysts are used for esterification, then high activity and selectivity are achieved, but long reaction duration is required
Solution Approach 1:
The patent combines a metal-containing catalyst (titanium tetraisopropoxide) and an acid catalyst (p-toluenesulfonic acid) into a dual-catalyst system. The metal catalyst provides high selectivity and initial activity, while the acid catalyst accelerates the reaction rate and reduces reaction time. This merging of catalyst functions resolves the contradiction between maintaining high selectivity and reducing reaction duration.
Solution Approach 2:
The patent optimizes reaction parameters including temperature (180-225°C), pressure (atmospheric), and catalyst amounts (0.2 wt% metal catalyst, 0.1-0.5 wt% acid catalyst) to achieve both high conversion and reduced reaction time. By adjusting these parameters, the system maintains high catalyst activity while shortening the required reaction duration from 8-9 hours to 4-6 hours.
2Productivity
If protonic acid catalysts are used for esterification, then high reaction rate is achieved at lower temperature and pressure, but selectivity decreases and by-products increase
Solution Approach 1:
The patent merges the functions of a metal-containing catalyst (providing high selectivity) with an acid catalyst (providing high reaction rate). The metal catalyst component maintains selectivity and minimizes by-product formation, while the acid catalyst component accelerates the reaction rate at lower temperatures. This combination resolves the contradiction between productivity and selectivity.
3Productivity
If high temperature and pressure are applied for esterification, then reaction speed increases, but energy consumption increases
Solution Approach 1:
The patent changes the operational parameters by using a dual-catalyst system that enables the reaction to proceed at lower temperatures (180-225°C) and atmospheric pressure compared to conventional single-catalyst methods. This parameter optimization maintains high reaction speed while significantly reducing energy consumption and eliminating the need for high-pressure equipment.
4Loss of time
If acid catalysts are used for esterification, then reaction time is reduced, but product color and acid number increase
Solution Approach 1:
The patent combines a metal-containing catalyst (titanium tetraisopropoxide) that ensures high selectivity and product quality with an acid catalyst (p-toluenesulfonic acid) that reduces reaction time. The metal catalyst component prevents color formation and maintains low acid number, while the acid catalyst accelerates the reaction. This merged system resolves the contradiction between reaction time and product quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a high-yield, high-quality terephthalic acid ester with a low acid number and color, suitable for use as a PVC plasticizer, characterized by improved process efficiency and product quality.
Implementation Method 1
Reactions of esterification are catalyzed reactions. The use of inorganic and organic metal-containing compounds, in particular titanium-containing compounds, as a catalyst is known in the prior art.
Data Source
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AI summary
The present invention relates to the field of preparing esters of terephthalic acid, used as plasticizers for the manufacture of plasticizers for polyvinyl chloride plastic materials. The invention discloses a method according to which the step of esterification of the acid with an alcohol comprises the use of two catalysts of different nature, in particular a metal-containing catalyst and an acid catalyst, which are added sequentially. The technical result of the present invention is to increase conversion of terephthalic acid up to 100% and to reduce the amount of by-products formed during the production of a dicarboxylic acid ester. The obtained ester is characterized by a low acid number and a low value of color.