DD298636A5 - PROCESS FOR PREPARING OVER DIETHANOLAMINE CONTAINING REACTION MIXES FROM THE IMPLEMENTATION OF ETHENOXIDE AND AMMONIA - Google Patents

Abstract

The invention relates to a process for the preparation of diethanolamine by reacting ammonia and ethene oxide in the gas phase over a heterogeneous catalyst. The catalyst used is a crystalline silicate of the pentasil type. The reaction is carried out at normal pressure in the temperature range between 100 and 250 ° C. {diethanolamine; ethene oxide; Ammonia; Gas phase; Normal pressure; heterogeneous catalyst; Silicate pentasil type}

Description

Characteristic of the known state of the art

It is known that in the reaction between ammonia and ethene oxide in the presence of water or another polar solvent, a mixture of monoethanolamine, diethanolamine and triethanolamine is formed. The ratio of the individual ethanolamines to each other depends almost exclusively on the ratio of ammonia and ethene oxide and can thus be varied within relatively wide limits, but it is not possible in the usual way to obtain diethanolamine as the main product. The highest achievable content of diethanolamine in the reaction mixture of the reaction of ammonia and ethene oxide is about 35%, based on mass, already about 30%, based on the weight of triethanolamine, are formed and still about 35%, based on the weight of monoethanolamine front-indan are, (Ullmann's Encyclopedia of Industrial Chemistry, 4th edition)

The recovery of the pure diethanolamine from this reaction mixture is carried out by distillation and requires a high energy expenditure, in particular because of the separation of the excess ammonia and the water necessary to accelerate the reaction.

It is also known to produce diethanolamine by the reaction of monoethanolamine with ethene oxide. The known technical processes operate in the liquid phase at elevated pressure (> 2.0 MPa) and a three to seven-fold excess of monoethanolamine. The technical effort for the pressure reaction, the use of expensive monoethanolamine as starting material and the still required excess of monoethanolamine burden in an economically intolerable manner the recovery of pure diethanolamine. (US-PS 2373199)

A process has furthermore been described in which diethanolamine can be prepared in good yield by reacting pure monoethanolamine with ethenoxide in the vapor phase at about the boiling point of the monoethanolamine. The diethanolamine formed is removed immediately after its formation from the reaction zone in order to largely avoid its reaction with further ethene oxide to triethanolamine. (DE-OS 1119296) The main disadvantage of these two methods described for the production of diethanolamine is the use of pure monoethanolamine as starting material. Monoethanolamine must be prepared in an upstream reaction of aqueous ammonia solution and ethene oxide, with high pressures and a large excess of ammonia in the reaction mixture are required to obtain monoethanolamine as the main product. The recovery of pure monoethanolamine from the resulting reaction mixture requires its work-up by distillation, which is a very energy-intensive process step because of the separation of the water.

Objective of the invention

The aim of the invention is to produce diethanolamine by reaction of cheap starting materials with a reduced technological complexity and with a reduced energy expenditure in the distillative workup of the resulting reaction mixture.

Explanation of the essence of the invention

The object of the invention is to increase the yield of diethanolamine to at least 50% in the reaction of ethene oxide with ammonia in a reaction step.

According to the invention the object is achieved in that takes place in the reaction of ammonia and ethene oxide in the gas phase without the addition of water or another polar solvent on a heterogeneous catalyst, the formation of diethanolamine as the main product in a single reaction step. As a heterogeneous catalyst a crystalline silicate of the pentasil type with the chemical composition 0,9-1,2Na ₂ O ♦ Al ₂ O ₃ · 25-70SiO ₂ is inserted. It proves to be particularly advantageous that the crystalline silicate in the form in which it is obtained in the hydrothermal synthesis, can be used. The reaction of ammonia and ethene oxide is carried out at atmospheric pressure in the temperature range between 100 and 250 ° C, preferably between 150 and 200 ⁰ C. The molar ratio of ammonia to ethene oxide can be varied between 2: 1 and 12: 1. The reaction takes place in a reactor designed so that the reaction products can quickly leave the reaction zone formed by the catalyst. Unreacted ammonia and ethene oxide are removed in gaseous form and reacted again. The reaction mixture, which consists of the main product diethanolamine and monoethanolamine, triethanolamine and small amounts of glycols as by-products, leaves the reactor in liquid form and is fed directly to a distillative workup.

embodiments example 1

In a tubular reactor are 5crr ^{3 of} a crystalline silicate Pentaslltyp with the chemical composition 0.9-1 Na ₂ O * Al ₂ O ₃ * 25-70SiO ₂ as a catalyst. A gas mixture consisting of ammonia and ethene oxide is passed through the reactor at about atmospheric pressure. The molar ratio of ammonia to ethene oxide is 6: 1. The charge of the catalyst with gaseous ethene oxide is 400 h ^-1 , With the aid of a heat transfer circuit, the reactor is heated to 160 ° C. Under these reaction conditions, 30% of the ethene oxide is converted in a single pass through the reactor obtained liquid reaction product containing 9%, based on the weight of monoethanolamine, 55%, based on the weight of diethanolamine and 23%, based on the weight of triethanolamine and small amounts of ethylene glycol and diethylene glycol.

Example 2 In the leaker described in Example 1, again 5 cm ^{3 of} the catalyst described above are used. By the At a reaction temperature of 190 ^° C., the reactor is composed of ammonia and ethene oxide in a molar ratio of 10: 1 Guided gas mixture. The load of the catalyst with gaseous ethene oxide is 200 h ^-1 . Among these Reaction conditions convert 38% of the ethene oxide. The liquid reaction product contains 10% by mass Monoethanolamine, 69%, based on the weight of diethanolamine, 16%, based on the weight of triethanolamine and a small amount Ethylene glycol.

Claims (1)

Procedure. '. ¹ Jr Preparation of predominantly diethanolamine-containing reaction mixtures from the reaction of ammonia with ethene oxide, characterized in that the reaction in the gas phase at atmospheric pressure and in the temperature range between 100 and 200 ⁰ C on a crystalline silicate of pentasil type with the chemical composition 0.9- 1.2 Na ₂ O ♦ Al ₂ O ₃ * 25-70SiO _{2 is performed} as a heterogeneous catalyst. field of use The invention relates to a process for the preparation of diethanolamine, which is an important starting material for many organic syntheses.