Method for preparing high-quality isopropanolamine

Abstract

The invention provides a method for preparing high-quality isopropanolamine, which comprises the following steps: reacting propylene oxide with ammonia water, and post-treating the reaction mother liquor to obtain monoisopropanolamine, diisopropanolamine and triisopropanolamine, the total content of aldehydes and ketones in the epoxypropane used for preparing the monoisopropanolamine, the diisopropanolamine and the triisopropanolamine is controlled to be 1 to 100 ppm. According to the invention, the total amount of aldehydes and ketones in the epoxypropane raw material used in the preparation process of the isopropanolamine is controlled to be 1-100ppm, so that the generation of imine and oxazolidine impurities can be reduced, and the application of the isopropanolamine in the fields of personal care industry, medicines, pesticides and electronics can be met.

Description

Technical Field

[0001] The invention belongs to the field of isopropanolamine production, relates to a method for preparing high-quality isopropanolamine, and more specifically to total amount control of characteristic impurity aldehydes in raw material propylene oxide used in the process of preparing high-quality isopropanolamine. Background Art

[0002] In the prior art documents, the technical route of synthesizing a series of isopropanolamine mixtures using ammonia and propylene oxide as raw materials, and then separating the three products of monoisopropanolamine, diisopropanolamine and triisopropanolamine step by step is known, such as patents CN1410416A, CN 109748805A, and CN 101265196A. The prepared isopropanolamine is currently widely used in industries such as synthetic surfactants, industrial and civilian cleaning agents, metal cutting, propylene diamine, and coatings. Moreover, as the recognition of the low-toxicity and green characteristics of isopropanolamine by all sectors of society continues to deepen, the many effects of isopropanolamine are better utilized, and its new technologies and new uses are also continuously developed. In recent years, isopropanolamine has been applied and developed in the personal care industry, such as disinfectant hand sanitizers, cosmetics, and other fields. This makes the impurity problem in isopropanolamine a problem that has received increasing attention.

[0003] During the research and development of isopropanolamine, the laboratory found that the main impurities in the product were 1,2-propylene glycol, imine compounds, five-membered oxygen heterocycles and other impurities, but there are few prior art reports on the control of isopropanolamine impurities in the relevant field. The literature [Zhang Xiaoyan, Research on the Preparation Process of Single-Component DIPA, 2020] reported on the control of propylene glycol impurities. The author of the literature reduced the generation of propylene glycol by adjusting the process such as catalyst feed amount, PO feed distribution, distillation temperature, and reflux ratio, but did not study other impurities. Patent CN 106083617 B proposed in the field of diethanol monoisopropanolamine production that the aldehydes in propylene oxide will react with diethanolamine to form Schiff bases and further form colored substances, and by adding ammonia to diethanolamine, the aldehydes react with ammonia first, avoiding the formation of color-forming substances. However, this method requires the addition of excess liquid ammonia. The addition of liquid ammonia not only increases the danger of the process, but also greatly increases the energy consumption of subsequent deamination. In addition, the patent does not disclose the specific content of impurities, and cannot solve the generation of impurities from the source. Summary of the invention

[0004] Aiming at the needs of personal care industry, medicine, pesticide, and electronics fields for high-quality isopropanolamine, the present invention proposes requirements for isopropanolamine impurity control, specifically studies and solves the impurity problems of imine compounds and methyloxazolidine compounds in isopropanolamine from the source, and provides a method for preparing high-quality isopropanolamine.

[0005] The inventors of the present invention have found through research that the imine compounds in the isopropanolamine product are mainly introduced by the reaction of aldehydes and ketones with the amine groups in the isopropanolamine, and these imine compounds and methyl oxazolidine compound impurities are almost impossible to be completely removed in the subsequent distillation separation, and thus are retained in the isopropanolamine product. The inventors can reduce the generation of imine and oxazolidine impurities by controlling the total amount of aldehydes and ketones in the propylene oxide raw material used in the preparation process of isopropanolamine, thereby completing the present invention.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing high-quality isopropanolamine comprises the steps of reacting propylene oxide with aqueous ammonia and post-treating the reaction mother liquor to obtain monoisopropanolamine, diisopropanolamine and triisopropanolamine, wherein the total content of aldehydes and ketones in the propylene oxide used for preparing the monoisopropanolamine, diisopropanolamine and triisopropanolamine is controlled to be 1 to 100 ppm.

[0008] The present invention controls the total amount of aldehydes and ketones in the propylene oxide raw material used in the preparation process of isopropanolamine to be 1-100 ppm, so that the monoisopropanolamine, diisopropanolamine and triisopropanolamine obtained by the reaction are almost free of imine and oxazolidine impurities, and can meet the application of isopropanolamine in the personal care industry, medicine, pesticide and electronic fields.

[0009] In some specific embodiments, the method for preparing high-quality isopropanolamine comprises the following steps:

[0010] S1: using propylene oxide with a total aldehyde and ketone content of 1 to 100 ppm, mixing it with ammonia water in proportion, and undergoing an ammonolysis reaction in a reactor to obtain a reaction mother liquor;

[0011] S2: The reaction mother liquor obtained in step S1 is subjected to deamination and dehydration treatment in sequence to obtain an isopropanolamine mother liquor;

[0012] S3: The isopropanolamine mother liquor obtained in step S2 is subjected to primary iso-rectification and secondary iso-rectification in sequence, and monoisopropanolamine and diisopropanolamine are obtained at the top of the tower, and triisopropanolamine is obtained at the bottom of the tower.

[0013] In the present invention, the aldehydes and ketones in the propylene oxide are any one or more of aldehydes and ketones such as formaldehyde, acetaldehyde, propionaldehyde, and acetone.

[0014] In the present invention, the total content of aldehydes and ketones in the propylene oxide is preferably controlled within a range of 1 to 50 ppm.

[0015] In the present invention, the mass concentration of ammonia in the ammonia water is 90-99%, and the preferred mass concentration is 95-98%.

[0016] In the present invention, the mass ratio of the aqueous ammonia to propylene oxide is 1.1 to 5.1, and the preferred mass ratio is 2.1 to 3.6.

[0017] In the present invention, the reaction temperature of the ammonolysis reaction is 100-200°C, preferably 130-150°C.

[0018] In the present invention, the reaction pressure of the ammonolysis reaction is 9-14 MPa, and the preferred pressure is 11-13 MPa.

[0019] In the present invention, the prepared isopropanolamine mother liquor contains imine and oxazolidine impurities, and the total amount of the imine and oxazolidine impurities is 10 to 500 ppm, based on the total mass of the isopropanolamine mother liquor.

[0020] In the present invention, the content of imine and oxazolidine impurities in the prepared monoisopropanolamine is 2 to 300 ppm, based on the total mass of the monoisopropanolamine.

[0021] In the present invention, the content of imine and oxazolidine impurities in the prepared diisopropanolamine is 2 to 100 ppm, based on the total mass of the diisopropanolamine.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention discovers and clarifies for the first time that the imine and oxazolidine impurities in the isopropanolamine product are mainly introduced by the reaction between the aldehyde and the amino group in the propylene oxide. Starting from the source, the quality of the isopropanolamine can be controlled by controlling the aldehyde and ketone content in the propylene oxide to 1-100 ppm, thereby effectively promoting the application of the isopropanolamine product in the personal care industry, medicine, pesticide, and electronic fields. DETAILED DESCRIPTION

[0024] The present invention is further described by means of specific embodiments. The embodiments of the present invention are only used as illustrations of the present invention and do not limit the scope of the present invention.

[0025] A method for preparing high-quality isopropanolamine comprises the steps of reacting propylene oxide with ammonia water and post-treating a reaction mother liquor to obtain monoisopropanolamine, diisopropanolamine and triisopropanolamine, wherein the propylene oxide used to prepare the monoisopropanolamine, diisopropanolamine and triisopropanolamine needs to control the total content of aldehydes and ketones in the propylene oxide to be 1 to 100 ppm, such as 2 ppm, 3 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm, 55 ppm, 60 ppm, 65 ppm, 70 ppm, 75 ppm, 80 ppm, 85 ppm, 90 ppm, 92 ppm, 95 ppm, 100 ppm, etc., preferably 1 to 50 ppm, wherein the monoisopropanolamine, diisopropanolamine and triisopropanolamine obtained by the reaction are almost free of imine and oxazolidine impurities, and can meet the application of isopropanolamine in the personal care industry, medicine, pesticide and electronic fields.

[0026] Specifically, the method for preparing high-quality isopropanolamine comprises the following steps:

[0027] S1: using propylene oxide with a total aldehyde and ketone content of 1 to 100 ppm, mixing it with ammonia water according to a certain proportion, and carrying out an ammonolysis reaction in a reactor to obtain a reaction mother liquor;

[0028] S2: The reaction mother liquor obtained in step S1 is subjected to deamination and dehydration treatment in sequence to obtain an isopropanolamine mother liquor;

[0029] S3: The isopropanolamine mother liquor obtained in step S2 is subjected to primary iso-rectification and secondary iso-rectification in sequence, and monoisopropanolamine and diisopropanolamine are obtained at the top of the tower, and triisopropanolamine is obtained at the bottom of the tower.

[0030] The monoisopropanolamine prepared by the present invention is high-quality monoisopropanolamine, wherein the imine and oxazolidine impurities are 2 to 300 ppm, for example, 5 ppm, 10 ppm, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, etc., based on the total mass of the monoisopropanolamine.

[0031] The diisopropanolamine prepared according to the present invention is high-quality diisopropanolamine, wherein the imine and oxazolidine impurities are 2 to 100 ppm, for example, 2 ppm, 3 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm, 55 ppm, 60 ppm, 65 ppm, 70 ppm, 75 ppm, 80 ppm, 85 ppm, 90 ppm, 92 ppm, 95 ppm, 100 ppm, etc., based on the total mass of the diisopropanolamine.

[0032] The existing national standards have clear provisions for ethyl / propionaldehyde in propylene oxide: ethyl / propionaldehyde ≤ 0.02% in qualified products and ≤ 0.005% in superior products. However, there are no reports on the aldehyde and ketone content in propylene oxide used in high-quality isopropanolamine.

[0033] According to the present invention, the content of aldehydes and ketones in the propylene oxide is required to be controlled within 1 to 100 ppm, and the types of aldehydes and ketones and their relative proportions are not limited, as long as the total content of aldehydes and ketones is controlled within the range required by the present invention.

[0034] Specifically, the control means of the total content of aldehydes and ketones can be achieved by conventional control means in the art, such as extraction distillation, ion exchange resin or other adsorbent adsorption, etc. This is not the key to the present invention. For example, reference can be made to patents CN110041292A, CN 114634467A, etc. The control means of the prior art can be introduced into the present invention.

[0035] The present invention has found that the aldehyde in propylene oxide mainly undergoes the following process during the preparation of isopropanolamine: propylene oxide and liquid ammonia undergo an ammonolysis reaction under high temperature and high pressure to obtain monoisopropanolamine, diisopropanolamine and triisopropanolamine, wherein the raw material liquid ammonia, especially the product monoisopropanolamine and diisopropanolamine, has active hydrogen on the N atom, which is easy to undergo dehydration condensation with the carbonyl group in aldehydes and ketones such as acetaldehyde, propionaldehyde and acetone under high temperature and high pressure to generate imine and oxazolidine impurities. Taking monoisopropanolamine and acetaldehyde as an example, the specific reaction is as follows:

[0036]

[0037] During the post-processing process, these impurities such as imines and oxazolidines can easily enter the monoisopropanolamine and diisopropanolamine products. In subsequent applications of isopropanolamine, especially in the personal care industry, such as as a cosmetic matrix and detergent ingredient, it is usually necessary to add acidic substances to react with isopropanolamine. At this time, if isopropanolamine contains imines and oxazolidines, these impurities can easily hydrolyze under acidic conditions and regenerate aldehydes and ketones, which are harmful to human health.

[0038] The invention starts from the source and controls the content of aldehydes and ketones in propylene oxide to be 1-100 ppm, thereby controlling the quality of isopropanolamine, thereby greatly promoting the application of isopropanolamine products in the personal care industry, medicine, pesticides, and electronic fields.

[0039] In the present invention, the mass concentration of ammonia in the ammonia water in step S1 is 90-99%, for example, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc., and the preferred mass concentration is 95-98%; the ratio of ammonia water to propylene oxide, by mass, is 1.1-5.1, for example, 1.2, 1.5, 1.8, 2.0, 2.1, 2.5, 2.7, 3.0, 3.3, 3.5, 3.8, 4.0, 4.5, 5.0 etc., preferably a ratio of 2.1 to 3.6; the reaction temperature of the ammonolysis reaction is 100 to 200°C, such as 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, etc., and the preferred temperature is 130 to 150°C; the reaction pressure of the ammonolysis reaction is 9 to 14MPa, such as 10MPa, 11MPa, 12MPa, 13MPa, etc., and the preferred pressure is 11 to 13MPa.

[0040] In the present invention, the deamination and dehydration treatment of the reaction mother liquor are both conventional distillation separation operations in the art. In the present invention, the one-isorectification and two-isorectification operations of the isopropanolamine mother liquor are both conventional vacuum distillation operations in the art. These conventional operations in the art can be, for example, referred to CN1410416A, CN114315612A, etc., and their related technical contents can be introduced into the present invention.

[0041] The present invention is further described below by more specific examples, but the scope of the present invention is not limited in any way.

[0042] The raw materials used in this embodiment are all from Wanhua Chemical. Among them, propylene oxide with low aldehyde and ketone content is a refined product obtained after distillation and ion exchange resin adsorption treatment. Specifically, propylene oxide with high aldehyde and ketone content is fed from the middle of the distillation tower (the top operating pressure is 0.1-0.2MPa, the reflux ratio is 2-5:1, the top temperature is 30-55°C, and the bottom temperature is 50-80°C), and the bottom discharge is then passed into a fixed bed filled with D113 ion exchange resin (the operating temperature is 20-100°C, the operating pressure is 0.1-5MPa, and the air velocity is 5-10h -1 ), after adsorption by ion exchange resin, propylene oxide with low aldehyde and ketone content can be obtained, wherein, by controlling the temperature and adsorption time, propylene oxide with different low aldehyde and ketone contents can be obtained.

[0043] The main testing methods involved in this embodiment are as follows:

[0044] Gas chromatograph: Agilent GC-7890A (FID) detector, PEG-20M capillary column (15m×0.53mm×1.0μm), injection port 300℃, detector 300℃; heating program: 100℃, constant temperature for 1min, then increase to 200℃ at a rate of 20℃ / min, and hold for 8min.

[0045] Example 1

[0046] The acetaldehyde content in the propylene oxide selected in this implementation case is 5 ppm, and the propionaldehyde content is 11 ppm.

[0047] Propylene oxide is passed through the reactor at a flow rate of 50kg / h and 95wt% ammonia water is passed through the reactor at a flow rate of 158kg / h, and reacted under the conditions of 100°C and 9MPa. The obtained reaction mother liquor is deaminated at a flash tower operating pressure of 0.8MPaG, a deamination tower operating pressure of 1.0MPaG, and a deamination tower operating temperature of 185°C, and is dehydrated at a dehydration tower operating pressure of -0.085MPaG and a dehydration tower operating temperature of 115°C to obtain isopropanolamine mother liquor, and then passes through an iso-rectification tower operating pressure of -0.098MPaG, an operating temperature of 150°C, and a diiso-rectification tower operating pressure of -0.097MPaG, an operating temperature of 130°C to obtain monoisopropanolamine and diisopropanolamine. After detection and analysis, the content of imine and oxazolidine impurities in monoisopropanolamine is 31ppm, and the content of imine and oxazolidine impurities in diisopropanolamine is 15ppm.

[0048] Example 2

[0049] The acetaldehyde content in the propylene oxide selected in this implementation case is 7 ppm, and the propionaldehyde content is 20 ppm.

[0050] Propylene oxide is passed through the reactor at a flow rate of 100kg / h and 93wt% ammonia water is passed through the reactor at a flow rate of 269kg / h, and reacted under the conditions of 140°C and 12MPa. The obtained reaction mother liquor is deaminated at a flash tower operating pressure of 0.8MPaG, a deamination tower operating pressure of 1.0MPaG, and a deamination tower operating temperature of 185°C, and is dehydrated at a dehydration tower operating pressure of -0.085MPaG and a dehydration tower operating temperature of 115°C to obtain isopropanolamine mother liquor, and then passes through an iso-rectification tower operating pressure of -0.098MPaG, an operating temperature of 150°C, and a diiso-rectification tower operating pressure of -0.097MPaG, an operating temperature of 130°C to obtain monoisopropanolamine and diisopropanolamine. After detection and analysis, the content of imine and oxazolidine impurities in monoisopropanolamine is 52ppm, and the content of imine and oxazolidine impurities in diisopropanolamine is 24ppm.

[0051] Example 3

[0052] The formaldehyde content in the propylene oxide selected in this embodiment is 1 ppm, the acetaldehyde content is 9 ppm, and the propionaldehyde content is 13 ppm.

[0053] Propylene oxide is passed through the reactor at a flow rate of 50kg / h and 90wt% ammonia water is passed through the reactor at a flow rate of 222kg / h, and reacted under the conditions of 150°C and 13MPa. The obtained reaction mother liquor is deaminated at a flash tower operating pressure of 0.8MPaG, a deamination tower operating pressure of 1.0MPaG, and a deamination tower operating temperature of 185°C, and is dehydrated at a dehydration tower operating pressure of -0.085MPaG and a dehydration tower operating temperature of 115°C to obtain isopropanolamine mother liquor, and then passes through an iso-rectification tower operating pressure of -0.098MPaG, an operating temperature of 150°C, and a diiso-rectification tower operating pressure of -0.097MPaG, an operating temperature of 130°C to obtain monoisopropanolamine and diisopropanolamine. After detection and analysis, the content of imine and oxazolidine impurities in monoisopropanolamine is 41ppm, and the content of imine and oxazolidine impurities in diisopropanolamine is 21ppm.

[0054] Example 4

[0055] The acetaldehyde content in the propylene oxide selected in this embodiment is 15 ppm, the propionaldehyde content is 30 ppm, and the acetone content is 8 ppm.

[0056] Propylene oxide is passed through the reactor at a flow rate of 100kg / h and 98wt% ammonia water is passed through the reactor at a flow rate of 153kg / h, and reacted under the conditions of 120°C and 11MPa. The obtained reaction mother liquor is deaminated at a flash tower operating pressure of 0.8MPaG, a deamination tower operating pressure of 1.0MPaG, and a deamination tower operating temperature of 185°C, and is dehydrated at a dehydration tower operating pressure of -0.085MPaG and a dehydration tower operating temperature of 115°C to obtain isopropanolamine mother liquor, and then passes through an iso-rectification tower operating pressure of -0.098MPaG, an operating temperature of 150°C, and a diiso-rectification tower operating pressure of -0.097MPaG, an operating temperature of 130°C to obtain monoisopropanolamine and diisopropanolamine. After detection and analysis, the content of imine and oxazolidine impurities in monoisopropanolamine is 107ppm, and the content of imine and oxazolidine impurities in diisopropanolamine is 48ppm.

[0057] Example 5

[0058] The formaldehyde content of the propylene oxide selected in this embodiment is 3 ppm, the acetaldehyde content is 35 ppm, the propionaldehyde content is 39 ppm, and the acetone content is 10 ppm.

[0059] Propylene oxide is passed through the reactor at a flow rate of 100kg / h and 99wt% ammonia water is passed through the reactor at a flow rate of 455kg / h, and reacted under the conditions of 200°C and 14MPa. The obtained reaction mother liquor is deaminated at a flash tower operating pressure of 0.8MPaG, a deamination tower operating pressure of 1.0MPaG, and a deamination tower operating temperature of 185°C, and is dehydrated at a dehydration tower operating pressure of -0.085MPaG and a dehydration tower operating temperature of 115°C to obtain isopropanolamine mother liquor, and then passes through an iso-rectification tower operating pressure of -0.098MPaG, an operating temperature of 150°C, and a diiso-rectification tower operating pressure of -0.097MPaG, an operating temperature of 130°C to obtain monoisopropanolamine and diisopropanolamine. After detection and analysis, the content of imine and oxazolidine impurities in monoisopropanolamine is 168ppm, and the content of imine and oxazolidine impurities in diisopropanolamine is 89ppm.

[0060] Example 6

[0061] The formaldehyde content of the propylene oxide selected in this embodiment is 3 ppm, the acetaldehyde content is 18 ppm, the propionaldehyde content is 40 ppm, and the acetone content is 38 ppm.

[0062] Propylene oxide is passed through the reactor at a flow rate of 50kg / h, and 95wt% ammonia water is passed through the reactor at a flow rate of 158kg / h, and reacted under the conditions of 130°C and 12MPa. The obtained reaction mother liquor is deaminated at a flash tower operating pressure of 0.8MPaG, a deamination tower operating pressure of 1.0MPaG, and a deamination tower operating temperature of 185°C, and is dehydrated at a dehydration tower operating pressure of -0.085MPaG and a dehydration tower operating temperature of 115°C to obtain isopropanolamine mother liquor, and then passes through an iso-rectification tower operating pressure of -0.098MPaG, an operating temperature of 150°C, and a diiso-rectification tower operating pressure of -0.097MPaG, an operating temperature of 130°C to obtain monoisopropanolamine and diisopropanolamine. After detection and analysis, the content of imine and oxazolidine impurities in monoisopropanolamine is 281ppm, and the content of imine and oxazolidine impurities in diisopropanolamine is 100ppm.

[0063] Comparative Example 1

[0064] The acetaldehyde content in the propylene oxide selected in this comparative case is 76 ppm, the propionaldehyde content is 99 ppm, and the acetone content is 42 ppm.

[0065] Propylene oxide is passed through the reactor at a flow rate of 50kg / h, and 95wt% ammonia water is passed through the reactor at a flow rate of 158kg / h, and reacted under the conditions of 100°C and 9MPa. The obtained reaction mother liquor is deaminated at a flash tower operating pressure of 0.8MPaG, a deamination tower operating pressure of 1.0MPaG, and a deamination tower operating temperature of 185°C, and is dehydrated at a dehydration tower operating pressure of -0.085MPaG and a dehydration tower operating temperature of 115°C to obtain isopropanolamine mother liquor, and then passes through an iso-rectification tower operating pressure of -0.098MPaG, an operating temperature of 150°C, and a diiso-rectification tower operating pressure of -0.097MPaG, an operating temperature of 130°C to obtain monoisopropanolamine and diisopropanolamine. After detection and analysis, the content of imine and oxazolidine impurities in monoisopropanolamine is 578ppm, and the content of imine and oxazolidine impurities in diisopropanolamine is 340ppm.

[0066] Comparative Example 2

[0067] The formaldehyde content of the propylene oxide selected in this comparative case is 10 ppm, the acetaldehyde content is 64 ppm, and the propionaldehyde content is 101 ppm.

[0068] Propylene oxide is passed through the reactor at a flow rate of 100kg / h, and 93wt% ammonia water is passed through the reactor at a flow rate of 269kg / h, and reacted under the conditions of 140°C and 12MPa. The obtained reaction mother liquor is deaminated at a flash tower operating pressure of 0.8MPaG, a deamination tower operating pressure of 1.0MPaG, and a deamination tower operating temperature of 185°C, and is dehydrated at a dehydration tower operating pressure of -0.085MPaG and a dehydration tower operating temperature of 115°C to obtain isopropanolamine mother liquor, and then passes through an iso-rectification tower operating pressure of -0.098MPaG, an operating temperature of 150°C, and a diiso-rectification tower operating pressure of -0.097MPaG, an operating temperature of 130°C to obtain monoisopropanolamine and diisopropanolamine. After detection and analysis, the content of imine and oxazolidine impurities in monoisopropanolamine is 402ppm, and the content of imine and oxazolidine impurities in diisopropanolamine is 134ppm.

[0069] By comparing the embodiments and the comparative examples, it can be seen that the total amount of aldehydes and ketones in propylene oxide is controlled to be 1-100 ppm, so that the total amount of imine and oxazolidine impurities in the isopropanolamine mother liquor is between 10 and 500 ppm, and finally the imine and oxazolidine impurities in monoisopropanolamine and diisopropanolamine are controlled to be between 2 and 300 ppm and 2 and 100 ppm, respectively, which meets the needs of downstream customers.

[0070] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention. Those skilled in the art will appreciate that, under the guidance of this specification, some modifications or adjustments may be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing high-quality isopropanolamine, characterized in that: The method comprises the steps of reacting propylene oxide with ammonia water and post-treating the reaction mother liquor to obtain monoisopropanolamine, diisopropanolamine and triisopropanolamine, wherein the total content of aldehydes and ketones in the propylene oxide used for preparing the monoisopropanolamine, diisopropanolamine and triisopropanolamine is controlled to be 1-100 ppm.

2. The method according to claim 1, characterized in that The following steps are involved: S1: using propylene oxide with a total aldehyde and ketone content of 1 to 100 ppm, mixing it with ammonia water in proportion, and undergoing an ammonolysis reaction in a reactor to obtain a reaction mother liquor; S2: The reaction mother liquor obtained in step S1 is subjected to deamination and dehydration treatment in sequence to obtain an isopropanolamine mother liquor; S3: The isopropanolamine mother liquor obtained in step S2 is subjected to primary iso-rectification and secondary iso-rectification in sequence, and monoisopropanolamine and diisopropanolamine are obtained at the top of the tower, and triisopropanolamine is obtained at the bottom of the tower.

3. The method according to claim 1 or 2, characterized in that: The aldehydes and ketones in propylene oxide are any one or more of formaldehyde, acetaldehyde, propionaldehyde and acetone.

4. The method according to any one of claims 1 to 3, characterized in that: The total content of aldehydes and ketones in propylene oxide is controlled at 1 to 50 ppm.

5. The method according to claim 1 or 2, characterized in that: The mass concentration of ammonia in the ammonia water is 90-99%, and the preferred mass concentration is 95-98%.

6. The method according to claim 1 or 2, characterized in that: The mass ratio of the aqueous ammonia to propylene oxide is 1.1 to 5.1, and the preferred mass ratio is 2.1 to 3.

6.

7. The method according to claim 6, characterized in that The reaction temperature of the ammonolysis reaction is 100 to 200°C, preferably 130 to 150°C; Preferably, the reaction pressure of the ammonolysis reaction is 9 to 14 MPa, preferably 11 to 13 MPa.

8. The method according to claim 1 or 2, characterized in that: The prepared isopropanolamine mother liquor contains imine and oxazolidine impurities, and the total amount of the oxazolidine impurities is 10 to 500 ppm, based on the total mass of the isopropanolamine mother liquor.

9. The method according to claim 1 or 2, characterized in that: The content of imine and oxazolidine impurities in the prepared monoisopropanolamine is 2-300 ppm, based on the total mass of the monoisopropanolamine.

10. The method according to claim 1 or 2, characterized in that: The content of imine and oxazolidine impurities in the prepared diisopropanolamine is 2-150 ppm, based on the total mass of the diisopropanolamine.

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