阅读说明：本技术 干燥环氧丙烷的方法 (Method for drying propylene oxide ) 是由 杨学勇 D·F·怀特 H·H·阮 R·J·雷布曼 C·A·阿尔塞诺 于 2020-05-13 设计创作，主要内容包括：干燥包括环氧丙烷的流的方法。所述方法可包括使包括环氧丙烷的流与分子筛接触。分子筛可以在干燥单元中,并且可以再生。包括环氧丙烷的流可以包括一种或多种其他有机化合物。(A process for drying a stream comprising propylene oxide. The process may include contacting a stream comprising propylene oxide with a molecular sieve. The molecular sieve may be in a drying unit and may be regenerated. The stream comprising propylene oxide may comprise one or more other organic compounds.)

1. A method of drying, the method comprising:

providing a first stream comprising propylene oxide and a first amount of water; and

contacting the first stream with a plurality of molecular sieves to form a second stream comprising propylene oxide and a second amount of water;

wherein the first amount of water is greater than the second amount of water.

2. The method of claim 1, wherein the plurality of molecular sieves are in a reservoir having an inlet and an outlet, and contacting the first stream with the plurality of molecular sieves comprises feeding the first stream into the inlet of the reservoir.

3. The method of claim 2, wherein the feed rate of the first stream at the inlet is effective to achieve about 0.01hr^-1To about 1.0hr^-1Space velocity of (a).

4. The method of claim 2, wherein the feed rate of the first stream at the inlet is effective to achieve about0.5hr^-1To about 1.0hr^-1Space velocity of (a).

5. The method of claim 2, wherein the reservoir is at ambient temperature and ambient pressure.

6. The process of claim 1, wherein the weight ratio of propylene oxide to the first amount of water in the first stream is from about 88: 12 to about 99: 1.

7. The process of claim 1, wherein the weight ratio of propylene oxide to the first amount of water in the first stream is from about 97: 3 to about 99: 1.

8. The method of claim 1, wherein the first amount of water comprises from about 1 wt.% to about 10 wt.% of the first stream.

9. The method of claim 1, wherein the first stream further comprises organic compounds, wherein the organic compounds are present in the first stream in an amount from about 0.001 wt.% to about 10 wt.% of the first stream.

10. The method of claim 9, wherein the organic compound comprises a hydrocarbon.

11. The process according to claim 10, wherein the hydrocarbon comprises 2-methyl-pentane.

12. The method of claim 1, wherein the second amount of water comprises from about 50ppm to about 300ppm of the second stream.

13. The method of claim 1, wherein the second amount of water comprises from about 100ppm to about 200ppm of the second stream.

14. The method of claim 1, wherein the plurality of molecular sieves has a molecular weight of aboutThe average pore diameter of (a).

15. The method of claim 1, further comprising regenerating the plurality of molecular sieves.

16. The method of claim 15, wherein the regenerating of the plurality of molecular sieves comprises (i) heating the plurality of molecular sieves at a temperature for a time effective to regenerate the plurality of molecular sieves, (ii) heating the plurality of molecular sieves at the temperature under vacuum for a time effective to regenerate the plurality of molecular sieves, (iii) heating the plurality of molecular sieves at the temperature for a time effective to regenerate the plurality of molecular sieves and contacting the plurality of molecular sieves with a carrier gas, or (iv) a combination thereof.

17. A method of drying, the method comprising:

providing a first stream comprising propylene oxide and a first amount of water, wherein the first amount of water constitutes from about 1 wt.% to about 12 wt.% of the first stream;

providing a molecular sieve drying unit comprising (i) a reservoir having an inlet and an outlet, and (ii) a plurality of molecular sieves in the reservoir, wherein the plurality of molecular sieves have a molecular sieve content of about(ii) an average pore diameter;

subjecting the first stream to a temperature effective to achieve about 0.01hr^-1To about 1.0hr^-1Is fed into the inlet of the reservoir; and

collecting a second stream at an outlet of the reservoir;

wherein the second stream comprises propylene oxide and a second amount of water, wherein the second amount of water comprises from about 50ppm to about 300ppm of the second stream.

18. The method of claim 17, further comprising regenerating the plurality of molecular sieves.

19. The method of claim 17, wherein the first stream further comprises organic compounds, wherein the organic compounds are present in the first stream in an amount from about 0.001 wt.% to about 10 wt.% of the first stream.

20. The method of claim 19, wherein the organic compound comprises 2-methyl-pentane, acetone, or a combination thereof.

Background

Propylene oxide is useful in many processes. For example, purified propylene oxide can be used as a feedstock in a process for producing 1, 4-butanediol. The production of 1, 4-butanediol can be achieved by isomerization of propylene oxide to allyl alcohol, which is then followed by synthesis gas (H)₂+ CO) to produce 4-hydroxybutyraldehyde, which is hydrogenated to 1, 4-butanediol.

Propylene oxide can be produced as a product or by-product of many processes. Propylene oxide produced by such processes may include more water than the refined propylene oxide stream used as a feedstock in certain processes, including the aforementioned processes for producing 1, 4-butanediol. For example, some processes produce a propylene oxide sample having a water content of about 2 wt.%.

Efforts to reduce the amount of water in propylene oxide have been based on distillation. Distillation, however, is a thermal separation process that is not ideal in terms of energy consumption.

There remains a need for a process for drying propylene oxide that is energy efficient, effective, does not cause the propylene oxide to react with one or more other compounds, and/or undesirably increases the likelihood that the propylene oxide can react with one or more other compounds.

Disclosure of Invention

Provided herein are methods of drying a stream comprising propylene oxide and water with a molecular sieve, including methods that may be energy efficient and/or effective. In some embodiments, the process has minimal or no effect on propylene oxide, including its chemical structure and/or reactivity. In some embodiments, the amount of water in the stream is reduced to about 50 ppm.

In one aspect, a method of drying a stream is provided. In some embodiments, the method includes providing a first stream comprising propylene oxide and a first amount of water, and contacting the first stream with a plurality of molecular sieves to form a second stream comprising propylene oxide and a second amount of water. In some embodiments, the first amount of water is greater than the second amount of water. In some embodiments, the method further comprises regenerating the molecular sieve.

In some embodiments, the process comprises providing a first stream comprising propylene oxide and a first amount of water, wherein the first amount of water comprises from about 1 wt.% to about 12 wt.% of the first stream; providing a molecular sieve drying unit comprising (i) a reservoir having an inlet and an outlet, and (ii) a plurality of molecular sieves in the reservoir; feeding a first stream into an inlet of the reservoir; and collecting the second stream at an outlet of the reservoir; wherein the second stream comprises propylene oxide and a second amount of water, wherein the second amount of water comprises from about 50ppm to about 300ppm of the second stream. In some embodiments, the first stream is effective to achieve about 0.01hr^-1To about 1.0hr^-1Is fed into the inlet of the reservoir.

Additional aspects will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the aspects described below. The advantages described below will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive.

Drawings

Fig. 1 depicts an embodiment of a molecular sieve drying unit.

Fig. 2 depicts a graph of water content (wt.%) versus the amount of Propylene Oxide (PO) by an embodiment of a molecular sieve drying unit.

Fig. 3 depicts a graph of water content (wt.%) versus the amount of Propylene Oxide (PO) by an embodiment of a molecular sieve drying unit including regenerated molecular sieve.

Detailed Description

Provided herein are methods of drying a stream comprising propylene oxide and water. As used herein, the term "drying" refers to the removal of at least a portion of the water present in the stream. In some embodiments, the processes described herein are capable of drying propylene oxide in an energy efficient manner, particularly as compared to other processes. Embodiments of the processes described herein have minimal or no effect on propylene oxide, including its reactivity and/or chemical structure.

In some embodiments, the methods herein can include providing a first stream comprising propylene oxide and a first amount of water; and contacting the first stream with a plurality of molecular sieves to form a second stream comprising propylene oxide and a second amount of water, wherein the first amount of water is greater than the second amount of water.

Contacting the first stream with the plurality of molecular sieves can be accomplished by any technique. In some embodiments, the plurality of molecular sieves may be in a reservoir having an inlet and an outlet, and contacting the first stream with the plurality of molecular sieves comprises feeding the first stream into the inlet of the reservoir. When multiple molecular sieves are in the reservoir, the resulting apparatus may be referred to herein as a "molecular sieve drying unit". Feeding the first stream into the inlet of the reservoir may be performed and/or assisted by a device such as a pump.

The reservoir may have any shape. In some embodiments, the reservoir is cylindrical. In some embodiments, the reservoir is cylindrical and has one or more tapered ends. The reservoir may also have any volume sufficient to hold a plurality of molecular sieves. In some embodiments, the volume of the reservoir is equal to or exceeds about 0.1% to about 10% of the minimum volume occupied by the plurality of molecular sieves.

The reservoir may have an inlet and an outlet. The reservoir may have a first end and a second end, and the inlet and outlet may be disposed at or near the first and second ends, respectively. In some embodiments, the inlet and outlet are located at positions that increase and/or maximize the residence time of the stream in the reservoir, increase and/or maximize the percentage of molecular sieve in contact with the stream, or a combination thereof.

Fig. 1 depicts an embodiment of a molecular sieve drying unit. The molecular sieve drying unit 100 of fig. 1 includes a reservoir 110, which in this embodiment is made of a transparent material (e.g., glass, plastic, etc.). The reservoir 110 is cylindrical and has a tapered end 111. The reservoir 110 also includes an inlet 120 and an outlet 130 disposed at opposite ends of the reservoir 110. Within the reservoir 110 is a plurality of molecular sieves 160. Although the volume occupied by the plurality of molecular sieves 160 corresponds approximately to the volume of the reservoir 110, other configurations are possible. For example, in other embodiments, the plurality of molecular sieves 160 can occupy a portion of the volume of the reservoir 110 (e.g., 1/2, 3/4, etc.). A first stream 140 comprising propylene oxide and a first amount of water is fed into the reservoir 110 via the inlet 120 and a second stream 150 comprising propylene oxide and a second amount of water exits the reservoir 110 via the outlet 130.

The first stream can be fed into the inlet of the reservoir at any rate effective to dry the stream. The rate may be static, dynamic, or a combination thereof. For example, the first stream may be fed at a static rate during a first portion of the process, and then the rate may be reduced during a second portion of the process.

In some embodiments, the rate of feeding the first stream in the inlet is effective to achieve about 0.01hr^-1To about 1.0hr^-1Space velocity (mass flow rate of the first stream/mass of the plurality of molecular sieves). In some embodiments, the rate of the first stream fed at the inlet is effective to achieve about 0.1hr^-1To about 1.0hr^-1Space velocity of (a). In some embodiments, the rate of the first stream fed at the inlet is effective to achieve about 0.2hr^-1To about 1.0hr^-1Space velocity of (a). In some embodiments, the rate of the first stream fed at the inlet is effective to achieve about 0.3hr^-1To about 1.0hr^-1Space velocity of (a). In some embodiments, the rate of the first stream fed at the inlet is effective to achieve about 0.4hr^-1To about 1.0hr^-1Space velocity of (a). In some embodiments, the rate of the first stream fed at the inlet is effective to achieve about 0.5hr^-1To about 1.0hr^-1Space velocity of (a). In some embodiments, the rate of the first stream fed at the inlet is effective to achieve about 0.6hr^-1To about 1.0hr^-1Space velocity of (a). In some embodiments, the rate of the first stream fed at the inlet is effective to achieve about 0.7hr^-1To about 1.0hr^-1Space velocity of (a). In some embodiments, the rate of the first stream fed at the inlet is effective to achieve about 0.8hr^-1To about 1.0hr^-1Space velocity of (a). In some embodiments, the rate of the first stream fed at the inlet is effective to achieve about 0.9hr^-1To about 1.0hr^-1Space velocity of (a).

When the plurality of molecular sieves is in the reservoir, the reservoir may be subjected to any temperature and/or any pressure. In some embodiments, the reservoir is at ambient temperature during the methods described herein. When not trying to affect the temperature of the reservoir, the reservoir is at ambient temperature; for example, the reservoir is not placed in or near a heating or cooling device. It should be noted that when water molecules are adsorbed onto the plurality of molecular sieves, the temperature of the reservoir can be changed by the heat of adsorption. Due to the heat of adsorption, a reservoir at ambient temperature as defined herein may have a temperature slightly higher than the ambient temperature at which the reservoir is used. Thus, as used herein, the phrase "ambient temperature" includes [1] the temperature of the reservoir when no effort is made to change the temperature of the reservoir, and [2] the temperature resulting from one or more features of the processes described herein, such as the heat of adsorption resulting when water molecules adsorb to the plurality of molecular sieves.

In some embodiments, the reservoir is subjected to a temperature greater than ambient temperature. The temperature above ambient temperature may be achieved by any technique, such as placing the reservoir in or near a heating device. The heating apparatus may include a heated oil bath in which the reservoir is at least partially submerged, a heated wrap adjacent to and/or in contact with at least a portion of an outer surface of the reservoir, a heat source positioned proximate to the reservoir, or a combination thereof.

In some embodiments, the reservoir is subjected to a temperature less than ambient temperature. A temperature less than ambient temperature may be achieved by any technique, such as placing the reservoir in or near a cooling device. The cooling apparatus may include a cooling bath (e.g., an ice bath) in which the reservoir is at least partially submerged, a cooling source placed at or near the reservoir, or a combination thereof.

The plurality of molecular sieves used in the methods described herein can be regenerated. As used herein, the terms "regenerated," "regenerated," and the like refer to the elimination or reduction of the amount of water adsorbed onto the plurality of molecular sieves. Regeneration of molecular sieves can increase their effectiveness because regeneration can increase the area of the molecular sieve to which water molecules can be adsorbed.

In some embodiments, the regenerating of the plurality of molecular sieves comprises (i) heating the plurality of molecular sieves at a temperature for a time effective to regenerate the plurality of molecular sieves, (ii) heating the plurality of molecular sieves at the temperature under vacuum for a time effective to regenerate the plurality of molecular sieves, (iii) heating the plurality of molecular sieves at the temperature for a time effective to regenerate the plurality of molecular sieves and contacting the plurality of molecular sieves with a carrier gas, or (iv) a combination thereof. The carrier gas may be an inert gas, a dry (or near dry) gas, or a combination thereof. For example, nitrogen (N) may be used₂) Argon, or combinations thereof.

First stream

The methods described herein can include providing a first stream including propylene oxide and a first amount of water.

The first stream may be a stream produced by a chemical process, such as a chemical process that produces propylene oxide as a product or byproduct.

Without wishing to be bound by any particular theory, it is believed that the mixture of propylene oxide and water may include up to about 12.6 wt.% water before phase separation can occur. Thus, in the first stream described herein, the weight ratio of propylene oxide to the first amount of water can be from about 87.4: 12.6 to about 99.999: 0.001.

In some embodiments, the weight ratio of propylene oxide to the first amount of water for the first stream is from about 88: 12 to about 99: 1. In some embodiments, the weight ratio of propylene oxide to the first amount of water for the first stream is from about 90: 10 to about 99: 1. In some embodiments, the weight ratio of propylene oxide to the first amount of water for the first stream is from about 95: 5 to about 99: 1. In some embodiments, the weight ratio of propylene oxide to the first amount of water for the first stream is from about 97: 3 to about 99: 1.

In some embodiments, the first stream comprises at least one third compound (i.e., a compound other than propylene oxide and water). The at least one third compound may include any compound that does not undesirably affect the methods described herein.

In some embodiments, the first stream comprises organic compounds (i.e., organic compounds other than propylene oxide). The organic compound may include one or more hydrocarbons (e.g., C)₄-C₆Hydrocarbons, such as 2-methyl-pentane), one or more oxygenates (e.g., propionaldehyde, methanol, acetone, methyl formate, and aldehydes), or combinations thereof. The organic compound may be present in the first stream in an amount of about 0.001 wt.% to about 10 wt.% of the first stream, about 0.001 wt.% to about 8 wt.% of the first stream, about 0.001 wt.% to about 6 wt.% of the first stream, about 0.001 wt.% to about 5 wt.% of the first stream, about 0.001 wt.% to about 4 wt.% of the first stream, about 0.001 wt.% to about 2 wt.% of the first stream, or about 0.001 wt.% to about 1 wt.% of the first stream.

In some embodiments, the organic compound is a polar organic compound, such as acetone. In some embodiments, the organic compound is a non-polar organic compound, such as a hydrocarbon. For example, the hydrocarbon may comprise 2-methyl-pentane. In some embodiments, the organic compound comprises at least one polar organic compound and at least one non-polar organic compound. In some embodiments, the methods described herein are not undesirably affected by the presence of organic compounds (i.e., organic compounds other than propylene oxide) in the first stream.

In some embodiments, the first amount of water in the first stream constitutes from about 0.001 wt.% to about 12 wt.% of the first stream. In some embodiments, the first amount of water in the first stream constitutes from about 1 wt.% to about 12 wt.% of the first stream. In some embodiments, the first amount of water in the first stream constitutes from about 1 wt.% to about 10 wt.% of the first stream. In some embodiments, the first amount of water in the first stream constitutes from about 1 wt.% to about 8 wt.% of the first stream. In some embodiments, the first amount of water in the first stream constitutes from about 1 wt.% to about 5 wt.% of the first stream. In some embodiments, the first amount of water in the first stream constitutes from about 1 wt.% to about 4 wt.% of the first stream. In some embodiments, the first amount of water in the first stream constitutes from about 1 wt.% to about 3 wt.% of the first stream.

Second stream

The processes described herein can produce a second stream comprising propylene oxide and a second amount of water. The first amount of water present in the first stream may be greater than the second amount of water present in the second stream. In some embodiments, the first and second flows may be similar except for the difference between the first and second amounts of water.

In some embodiments, the second amount of water comprises 0.1 wt.% or less of the second stream. Thus, the second stream may comprise propylene oxide and about 0.1 wt.% or less water; alternatively, the second stream can include propylene oxide, one or more third compounds (e.g., organic compounds other than propylene oxide), and about 0.1 wt.% or less of water.

In some embodiments, the second amount of water comprises from about 10ppm to about 500ppm of the second stream. Thus, the second stream may comprise propylene oxide and from about 10ppm to about 500ppm water; alternatively, the second stream can include propylene oxide, one or more third compounds (e.g., organic compounds other than propylene oxide), and from about 10ppm to about 500ppm water. In some embodiments, the second amount of water comprises from about 50ppm to about 300ppm of the second stream. In some embodiments, the second amount of water comprises from about 10ppm to about 400ppm of the second stream. In some embodiments, the second amount of water comprises from about 100ppm to about 400ppm of the second stream. In some embodiments, the second amount of water comprises from about 100ppm to about 300ppm of the second stream. In some embodiments, the second amount of water comprises from about 100ppm to about 200ppm of the second stream.

Molecular sieves

As used herein, the phrase "plurality of molecular sieves" refers to a collection of porous particles, wherein the porous particles are configured to adsorb molecules of a particular size (e.g., water molecules). The phrase "plurality of molecular sieves" includes, but is not limited to, monolithic structures consisting of one or more individual molecular sieves.

In some embodiments, the plurality of molecular sieves used in the methods described herein comprise a crystalline metal aluminosilicate having a three-dimensional interconnected network of silica and alumina tetrahedra.

In some embodiments, the plurality of molecular sieves comprises a molecular sieve having an average pore size of aboutThe "3A" molecular sieve of (1). In some embodiments, the plurality of molecular sieves comprises a molecular sieve having an average pore size of aboutThe "4A" molecular sieve of (1). In some embodiments, the plurality of molecular sieves comprises a molecular sieve having an average pore size of aboutOf a "3A" molecular sieve and having an average pore diameter of aboutThe "4A" molecular sieve of (1).

The plurality of molecular sieves can have any average particle size and/or shape. In some embodiments, the plurality of molecular sieves comprises spherical particles and/or spheroidal particles. In some embodiments, the plurality of molecular sieves can have similar average particle sizes. In some embodiments, the plurality of molecular sieves can have similar shapes. In some embodiments, the plurality of molecular sieves can have similar average particle sizes and similar shapes. In some embodiments, the plurality of molecular sieves have an average particle size of 8 mesh to 12 mesh (i.e., 1.68mm to 2.38 mm).

The plurality of molecular sieves can have an initial water adsorption capacity at 25 ℃ of at least 10 wt.%, at least 15 wt.%, at least 20 wt.%, at least 25 wt.%, at least 30 wt.%, at least 35 wt.%, or at least 40 wt.%. The plurality of molecular sieves can have an initial water adsorption capacity at 25 ℃ of about 10 wt.% to about 40 wt.%, about 15 wt.% to about 40 wt.%, about 20 wt.% to about 40 wt.%, about 25 wt.% to about 40 wt.%, about 30 wt.% to about 40 wt.%, or about 35 wt.% to about 40 wt.%. The phrase "initial water adsorption capacity" refers to the water adsorption capacity of the plurality of molecular sieves prior to the first regeneration. A first regeneration of the plurality of molecular sieves can result in a water adsorption capacity equal to or less than the initial water adsorption capacity, and each subsequent regeneration can have a similar effect on the water adsorption capacity. In some embodiments, the regeneration reduces the (i) initial water adsorption capacity or (ii) water adsorption capacity of the plurality of molecular sieves that previously underwent one or more regenerations by about 0 to about 10%, or about 0 to about 5%.

As used herein, "PO 90" typically includes at least 90 wt.% propylene oxide, 1.5-3 wt.% water, and one or more impurities (i.e., components other than propylene oxide). The one or more impurities may include: one or more of: hydrocarbons (e.g. C)₄-C₆Hydrocarbons such as 2-methyl-pentane or isobutylene), oxygenates (e.g., propionaldehyde, methanol, acetone, methyl formate, aldehydes, or combinations thereof), or combinations thereof.

In the description provided herein, the terms "comprising," being, "" containing, "" having, "and" including "are used in an open-ended fashion, and thus should be interpreted to mean" including, but not limited to. When a method is claimed or described in terms of "comprising" or "including" various elements or features, the method can also "consist essentially of" or "consist of" the various components or features, unless otherwise specified.

The terms "a", "an" and "the" are intended to include a plurality of alternatives, such as at least one. For example, unless otherwise specified, the disclosure of "first stream", "molecular sieve drying unit", "organic compound", or the like, is meant to encompass mixtures or combinations of one or more than one first stream, molecular sieve drying unit, organic compound, or the like.

Various numerical ranges may be disclosed herein. When applicants disclose or claim any type of range, it is the intention of applicants to disclose or claim individually each possible number that such a range can reasonably encompass, including the endpoints of the range and any subranges and combinations of subranges encompassed therein, unless otherwise specified. Furthermore, the numerical endpoints of the ranges disclosed herein are approximate. As a representativeBy way of illustrative example, applicants disclose in some embodiments that the rate at which the first stream is fed in the inlet is effective to achieve about 0.5hr^-1To about 1.0hr^-1Space velocity of (a). The disclosure should be construed to cover about 0.5hr^-1To about 1.0hr^-1And further covers "about" 0.6hr^-1、0.7hr^-1、0.8hr^-1And 0.9hr^-1Including any ranges and subranges between any of these values.

Embodiments of the invention are illustrated herein by reference to various embodiments, which are not to be construed in any way as imposing limitations upon the scope thereof. On the contrary, it is to be understood that various other aspects, embodiments, modifications, and equivalents thereof may occur to those of ordinary skill in the art upon reading the description herein, without departing from the spirit of the embodiments or the scope of the appended claims. Thus, other aspects of the embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein.

Examples

The present process is further illustrated by the following examples, which should not be construed as in any way imposing limitations upon the scope thereof. On the contrary, it is to be understood that various other aspects, embodiments, modifications, and equivalents thereof may occur to those of ordinary skill in the art upon reading the description herein, without departing from the spirit of the disclosure or the scope of the appended claims. Accordingly, other aspects of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the methods disclosed herein.

Example 1 drying of propylene oxide

In this example, a 50g sample was prepared by mixing propylene oxide and water. Prior to drying, the sample comprised 88.7 wt.% propylene oxide and 11.3 wt.% water.

A sample comprising propylene oxide (88.7 wt.%) and water (11.3 wt.%) was placed in a glass bottle containing 40g of fresh 3A molecular sieve. Maintaining the glass vial at ambient temperature and ambient pressure; in other words, no pressure is applied to the cell and the temperature of the cell does not increase beyond any increase caused by the heat of adsorption.

After a few hours, the amount of water in the sample was reduced to 500ppm and then further reduced to 350ppm after the sample was left in a glass bottle and contacted with molecular sieves overnight.

Example 2 drying of a propylene oxide stream

In this example, a stream comprising propylene oxide and water was dried with a molecular sieve drying unit.

Prior to drying, the stream comprised 97 wt.% propylene oxide and 3 wt.% water.

The molecular sieve drying unit of this example comprised a cylindrical column containing 60g of 3A molecular sieve.

A stream containing propylene oxide (97 wt.%) and water (3 wt.%) was pumped through the molecular sieve drying unit at a rate of 3 mL/min. The molecular sieve drying unit operates at ambient temperature and ambient pressure; in other words, no pressure is applied to the cell other than the pressure imparted by the flow rate, and the temperature of the cell does not increase beyond any increase imparted by the heat of adsorption.

In this example, a total of four runs were performed, with each run comprising pumping 400mL of the stream through the molecular sieve drying unit. The first run was run with fresh molecular sieve and the second to fourth runs were run with spent molecular sieve. The water content of the streams was tested at intervals depicted in fig. 2 as each stream was pumped through the molecular sieve drying unit.

The results of fig. 2 show that for the first 325mL stream, the water content of the stream is reduced from 3 wt.% to about 150 ppm. The results show that after about 350mL of the stream is pumped through the molecular sieve drying unit, the performance of the molecular sieve is reduced, providing guidance as to how the mass of the molecular sieve should be adjusted to accommodate the larger volume of the stream.

Example 3 molecular Sieve regeneration

The molecular sieve of the molecular sieve drying unit of example 2 was regenerated in this example. The molecular sieve is heated to 260 ℃ for about 12 hours to about 24 hours under a nitrogen purge.

If the temperature is greater than 260 c, an increased heating time may be used, or conversely, if the temperature is less than 260 c, a decreased heating time may be used.

Example 4 drying of a propylene oxide stream

In this example, a stream comprising propylene oxide and water was dried with a molecular sieve drying unit comprising the regenerated molecular sieve of example 3.

Prior to drying, the stream comprised 96.5 wt.% propylene oxide, 2.4 wt.% water, 0.4 wt.% hydrocarbons/isobutylene, 0.34 wt.% 2-methylpentanes, and 0.35 wt.% other hydrocarbons/oxygenates.

The molecular sieve drying unit of example 2 was used and included the molecular sieve of example 2 that had been regenerated by the process of example 3.

The stream was pumped through the molecular sieve drying unit at a rate of 3 mL/min. The molecular sieve drying unit operates at ambient temperature and ambient pressure; in other words, no pressure is applied to the cell other than the pressure imparted by the flow rate, and the temperature of the cell does not increase beyond any increase imparted by the heat of adsorption.

In this example, a total of four runs were performed, with each run comprising pumping about 550mL of the stream through the molecular sieve drying unit. The first run was run with fresh molecular sieve and the second to fourth runs were run with spent molecular sieve. The water content of the streams was tested at intervals depicted in fig. 3 as each stream was pumped through the molecular sieve drying unit.

The results in figure 3 show that the regenerated molecular sieve of this example has improved performance relative to the molecular sieve of example 2.

Example 5 Effect of other hydrocarbons

The test of this example was designed to determine if the presence of one or more hydrocarbons other than propylene oxide in the stream might undesirably affect water removal.

In this example, two types of feed samples were tested. The first type consisted of "pure" feed samples in which propylene oxide and water accounted for at least 99.9% of their weight (represented as "PO" in the tables below). The second type consists of PO90, the PO90 having a specific water content as provided in the table below, 0.4 wt.% hydrocarbons/isobutylene, 0.34 wt.% 2-methylpentane and 0.35 wt.% other hydrocarbons/oxygenates, the balance of the feed sample being propylene oxide (about 96.4 to about 96.6 wt.%).

The parameters and results of the testing of this example are shown in the following table:

results of example 5

The data in the above table show that the presence of additional organic compounds does not undesirably affect the water removal of this example.