Ethanol preparation method

Abstract

The invention provides a low-energy consumption method for preparation of ethanol by acetic acid hydrogenation. The method includes the steps of: (1) first stage gas phase hydrogenation; (2) gas-liquid separation and second stage hydrogenation; (3) esterification reaction; and (4) product refining: sending a liquid phase product B to a first rectification tower, sending first tower bottom fraction to a second rectification tower, returning part of the second tower top fraction into a hydrogenation reactor of (1), and recovering part of the second tower top fraction as a mixed solvent product, sending second tower bottom fraction into a neutralization reactor, adding an alkaline substance to carry out neutralization reaction; and sending the neutralized second tower bottom fraction to a third rectification tower. The method can reduce energy consumption and improve the quality of ethanol product.

Description

technical field [0001] The present invention relates to a kind of method of producing ethanol, more specifically, relate to a kind of method of preparing highly selective ethanol product by acetic acid hydrogenation. Background technique [0002] There are two ways to use acetic acid as a raw material to produce ethanol products. One is to generate acetate through esterification of acetic acid, then hydrogenate acetate to generate ethanol, and then refine it to produce ethanol products; the other is to directly hydrogenate acetic acid to generate ethanol, which is then refined process to produce ethanol products. Compared with the second method, the first method has an extra esterification process, and a large amount of ethanol needs to be recycled as an esterification raw material, which increases the size of the hydrogenation reactor and the size and energy consumption of the heat exchangers before and after it, at least Part of the refining process is also doubled. The a...

AI Technical Summary

Problems solved by technology

In these patents, acetic acid is generally removed first by rectification, which can reduce the material requirements in the subsequent separation, thereby reducing investment costs, but there are also some problems: ethanol and ethanol, which account for the vast majority of product quality Water needs to be vaporized, so the energy consumption of rectification and deacidification is extremely high, and the deacidification tower has a large size and high material requirements, and the investment cost is extremely high; and in the actual rectification separation, there may be a very small amount of In the case of acetic acid, fuel ethanol and industrial ethanol products have strict requirements on acidity, so the product is unqualified in the case of operational fluctuations

The present inventor has also carried out detailed research on the direct gas phase hydrogenation of acetic acid. After research, it has been found that it is relatively difficult to achieve higher ethanol selectivity (>98mol%), because it requires extremely high ethanol selectivity to achieve such selectivity. High molar ratio of hydrogen to acetic acid (>30), since hydrogen needs to be recycled, such a high molar ratio of hydrogen to acetic acid will greatly increase the energy consumption of the compressor, and the energy consumption of the entire system will also be very high

Images