Built-in micro-interface oxidation system and method for preparing terephthalic acid from p-xylene

Abstract

The invention provides a built-in micro-interface oxidation system for preparing terephthalic acid from p-xylene. The oxidation system includes: a first reactor, a rectification column, and a second reactor connected in sequence, the side wall of the first reactor is provided with a first outlet, and the side wall of the second reactor is provided with a first Inlet, the side wall of the rectification tower is provided with a material inlet, the bottom of the rectification tower is provided with a material outlet, the first outlet is connected with the material inlet of the rectification tower, and the first inlet is connected with the The material outlet of the rectification tower is connected, and both the first reactor and the second reactor are equipped with a micro-interface unit, and the micro-interface unit is used to disperse and break air into bubbles. The built-in micro-interface oxidation system of the present invention solves the problems of high energy consumption, large consumption of raw materials, and low reaction efficiency in the traditional process by placing a micro-interface unit inside the reactor and adopting a segmented process, and realizes cost savings for enterprises Effect.

Description

technical field [0001] The invention relates to the field of oxidation reactions for preparing terephthalic acid from p-xylene, in particular to a built-in micro-interface oxidation system and method for preparing terephthalic acid from p-xylene. Background technique [0002] Terephthalic acid is an important chemical raw material, usually produced by the oxidation reaction of p-xylene and oxygen-containing gas. The reactor for p-xylene oxidation usually adopts a bubbling oxidation reactor, and the direct bubble is usually larger than 3mm, or even At the centimeter level, the area of ​​the mass transfer boundary phase is limited, and the gas utilization rate is low so that the reaction efficiency is low. In order to strengthen the gas-liquid mass transfer, the bubbling reactor generally adds internals such as trays and static mixers in the tower to enhance mixing. However, the diameter of the bubbles after mixing is usually 3-30 mm, and the provided phase boundary area and m...

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Problems solved by technology

[0002] Terephthalic acid is an important chemical raw material, usually produced by the oxidation reaction of p-xylene and oxygen-containing gas. The reactor for p-xylene oxidation usually adopts a bubbling oxidation reactor, and the direct bubble is usually larger than 3mm, or even At the centimeter level, the area of ​​the mass transfer boundary phase is limited, and the gas utilization rate is low so that the reaction efficiency is low. In order to strengthen the gas-liquid mass transfer, the bubbling reactor generally adds internals such as trays and static mixers in the tower to enhance mixing. However, the diameter of the bubbles after mixing is usually 3-30 mm, and the provided phase boundary area and mass transfer coefficient (liquid side, gas side) are limited, so it is difficult to obtain a breakthrough improvement in reaction performance, which in turn affects the overall efficiency of the reaction. Therefore, high temperature and high pressure operations have to be used in engineering to increase the mass transfer rate by increasing the solubility of the gas phase and / or liquid phase, thereby strengthening the reaction process. However, the process of p-xylene oxidation is very complicated, mainly including 4 steps, namely p-xylene oxidation. Toluene (PX) → p-toluene (TALD) → p-toluic acid (p-TA) → p-carboxybenzaldehyde (4-CBA) → terephthalic acid (TA), the first two steps should be acetic acid As a solvent, it is not suitable to use high temperature and high pressure. The prior art adopts a mixed reaction process, which has high energy consumption, large consumption of acetic acid, and low reaction efficiency.

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