Built-in micro-interface oxidation system and built-in micro-interface oxidation 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 comprises a first reactor, a rectifying tower and a second reactor which are sequentially connected, wherein a first outlet is formed in the side wall of the first reactor; a first inlet is formed in the side wall of the second reactor; a material inlet is formed in the side wall of the rectifying tower; a material outlet is formed in the bottom of the rectifying tower; the first outlet is connected with the material inlet of the rectifying tower; the first inlet is connected with the material outlet of the rectifying tower; micro-interface units are arranged in the first reactor and the second reactor; and the micro-interface units are used for dispersingbroken air into bubbles. According to the built-in micro-interface oxidation system, the micro-interface units are arranged in the reactors, and a sectional process is adopted, so the problems of highenergy consumption, high raw material consumption and low reaction efficiency in traditional processes are solved, and the effect of saving cost for enterprises is achieved.

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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