Device for producing and processing of aromatic carboxylic acid and its preparation

 

(57) Abstract:

Use: production of carboxylic acids. In the installation process and production of aromatic carboxylic acids, such as terephthalic acid, at least some of the parts of the installation (especially those that are exposed to the acidic environment of the reaction at elevated temperature and pressure over 180oC and 8 bar, respectively) are made of stainless steel-duplex, and the conditions under which such part of the unit is exposed to the reaction medium, is controlled in order to maintain a low corrosion rate. 2 C. and 16 h.p. f-crystals, 4 PL.

The invention relates to a method of producing aromatic carboxylic acids using a catalyst, which includes bromine or brominated compounds, as well as to an apparatus for carrying out the method. The invention applies in particular to obtain terephthalic acid.

Aromatic carboxylic acids such as terephthalic acid, normally produced by oxidation of substituted aromatic compounds such as p-xylene with molecular oxygen in a lower aliphatic monocarboxylic acid as a solvent (predpochtite the under catalyst, comprising one or more compounds of a heavy metal and bromine or promotergene connection.

It is widely known that the chemical reagents used in this chemical reaction, particularly corrosive under the conditions of temperature and pressure, usually used to obtain high output. This inevitably led to widespread use of suitable corrosion-resistant materials for constructing parts of the reactor and associated parts of the installation. Thus expensive titanium and titanium alloys are widely used as structural materials installation for efficient oxidation, such as p-xylene to terephthalic acid, especially when the oxidation reaction is carried out using a lower aliphatic monocarboxylic acid as a solvent and in the presence of bromine or prosteradlo connection. Thus, we need a quote from US-A-4330676 (column 4, lines 47-54): "If the catalyst contains bromide, the material must usually be capable of withstanding the resulting highly corrosive reaction mixture, for example titanium, but in the absence of bromide suitable less expensive materials, such as stainless steel.

For togal, did from time to time proposals involving the modification of reaction conditions, i.e., materials used in the oxidation reaction, and/or parameters, such as temperature and pressure at which the reaction is carried out oxidation. For example, US-A-4278810 and GB-A-2094800 describe the method of obtaining terephthalic acid, which deliberately excluded from the oxidation of bromine water is used as a substitute for acetic acid and the reaction is carried out at relatively low temperatures.

According to one aspect of the invention proposes a device for producing and processing of aromatic carboxylic acids, preferably terephthalic acid), in which the aromatic carboxylic acid is obtained by oxidation in the liquid phase of substituted aromatic compounds such as p-xylene, in a reaction medium comprising a lower aliphatic acid, in the presence of a catalyst system containing cobalt, manganese and bromine, characterized in that at least some of the parts of this installation, which when used are exposed to the reaction medium (especially when exposure occurs at elevated temperatures and pressures above 180oC and 8 BEM steel, containing ferritic and austenitic phases, usually austenite and ferrite are included in approximately equal parts.

Part of the unit that are exposed to the reaction medium under certain conditions, include the reactor vessel, which is above the oxidation reaction in the liquid phase, and also the first stage of crystallization vessel, which is part of a series of vessels stage of crystallization, which is the crystallization of the aromatic carboxylic acid from a liquid mother liquor. Conditions prevailing in these vessels, especially severe and still needed to use these vessels as materials titanium and titanium alloys.

Preferably the above parts are manufactured from ostlegionen stainless steel duplex consisting of molybdenum, and which when exposed neperesekayuschiesya environment of the liquid phase, having a composition, as defined below, at a temperature of 191oC for 14 days exhibit a corrosion rate of not more than 0.1 mm/year. The liquid phase consists of:

Acetic acid - 88,01% wt./wt.

Water - 11,99% wt./wt.

Bromine - 944 million hours

Cobalt - 410 million hours

Manganese - 412 million hours

and the composition of the reaction medium, present in the first mold unit for production of terephthalic acid.

Used herein, the term "corrosion rate" means the rate of corrosion of C, obtained by the following formula:

C = W/(S)3650/E (unit: mm/year)

where W stands for the weight loss (g) of the sample having a surface area S (cm2during exposure of the liquid phase for E days, a sample of the alloy has a density D (g/cm3).

Preferably stainless steel-duplex is that under certain conditions, is the corrosion rate is not more than 0.05 mm, more preferably not more than 0.04 mm/year and especially preferably not more than 0.025 mm/year.

According to the second aspect of the invention features a method of obtaining an aromatic carboxylic acid, including the oxidation of aromatic compounds such as p-xylene, in an aqueous reaction medium lower aliphatic monocarboxylic acid at a temperature of 180 - 220oC and a pressure of 8 to 20 bar and in the presence of a catalytic oxidation system comprising cobalt, manganese and bromine, in order to obtain the above-mentioned aromatic carboxylic acid, the supply of liquid mother liquor of the above aromatic carboxylic acid characterized about:

by carrying out the oxidation process and/or at least the first stage of crystallization in an oxidizing and/or crystallization vessels, whose surface in contact with the reaction medium are made of stainless steel-duplex;

by controlling the reaction conditions and, in particular, the water content in the reaction medium in order to comply with the conditions under which the corrosion rate of the solution in contact with steel duplex and having a composition, as defined below, when exposed to the reaction medium in liquid phase under such conditions, does not exceed 0.15 mm/year.

The above composition comprising the following components in the amounts given 5%:

Carbon - 0,017

Silicon - 0,21

Manganese - 0,44

Phosphorus - 0,018

Sulfur - 0,001

Chrome - 24,74

Nickel - 6,72

Molybdenum - 3,8

Nitrogen - 0,28

Copper - 0,1

Tungsten - 0,1

Iron - Rest

Preferably the reaction conditions are controlled so as to correspond to the conditions under which the rate of corrosion of steel duplex with a specific composition when it is exposed to such conditions, not more than 0.1, more preferably 0.05 mm/year.

Usually at least the first is 180oC and 8 bar.

In a more specific aspect of the invention, the reactor vessel and/or vessel of the mold and other parts inside or associated with the reactor vessel and/or vessel of the mold, and subjected to the reaction medium in liquid phase at a certain temperature and pressure, are made from stainless steel-duplex, which set out the conditions exhibits a corrosion rate of not more than 0.15 (more preferably 0.1 and particularly preferably 0,05) mm/year.

Preferably stainless steel-duplex, used for the production of the reactor vessel and/or vessel for the first crystallization, has a composition lying within the following limits:

Carbon is Not more than 0,03

Silicon is Not more than 2.0

Manganese - Not more than 2.0

Phosphorus - Not more than 0.04

Sulfur is Not more than 0.04

Chrome - 24 - 26

Nickel - 5 - 8

Molybdenum - 3 - 4

Nitrogen - 0,2 - 0,3

Tungsten is Not more than 1.0

Copper is Not more than 2.5

Iron - Rest

Part, made of stainless steel, duplex, can be basically entirely made of such material, alternatively, they may be produced from a first material, which is less corrosion resistant than Vienna-resistant material to protect it from exposure to corrosive fluids. For example, the reactor vessel can be covered inside a steel duplex coating of steel duplex is attached to or associated with any suitable way with a material that is less corrosion-resistant, such as carbon steel, thus less corrosion-resistant material is protected by the coating of steel-duplex.

In addition, we do not exclude the possibility that part of the installation and/or installation components were made of two or more materials, including steel, duplex and material that has better corrosion resistance in comparison with steel-duplex when process conditions. For example, we found that in some parts of the installation, such as the oxidation reactor, the chemical composition can be particularly corrosive in the vapor phase and in the water content and the vapor phase is higher than in the liquid phase. In this case, it is preferable to do so as part of the installation, for example the oxidation reactor and/or the first mold has been designed so that the core and/or mold in contact with the liquid phase, were made of steel duplex (or covered by it), while the core and/or mold in contact with the steam is sustainable materials (or covered by), for example, titanium, titanium alloy or Nickel alloy, such as a suitable alloy Hastelloy.

The invention has, in particular, the use in installations in which the oxidation process is performed under conditions of relatively high temperature and pressure in the presence of bromine and water so that the resulting final crude terephthalic acid containing 4-carboxybenzene (4-CBA) in the range from 300 to 7000 hours per million relative to crude terephthalic acid. If the oxidation reaction is weak, the content of 4-CBA higher in comparison with the previously defined limit, and the subsequent purification of crude terephthalic acid may further include an oxidation reaction of an aqueous solution of crude terephthalic acid oxidizing agent such as gaseous oxygen or other agent, (which is not necessarily gaseous), in order to transform at least part of the 4-CRA terephthalic acid. This additional oxidation reaction can be followed in the usual hydrogenation reaction, including the interaction of the aqueous solution of terephthalic acid with hydrogen in terms of recovery, in order to transform the remaining impurities in forms that are compatible with final Proenza, such as the United filtering and washing using a band filter of Pannevis described in Filtration and Separation, Marcb/April 1979, R. 176 et seg.).

The composition of the mixture of the liquid phase in the reactor vessel oxidation is usually: 85 to 97 wt.% wt./ acetic acid, 3 - 15 wt.% wt./water, 300 - 3000 hours per million concentration of bromine, 250 to 2000 hours per million manganese content, 100 - 2000 hours per million cobalt content and 0 to 250 hours per million of sodium. Preferably the water content relative to the content of water/acetic acid is 3 to 10 wt.%/wt., and the content of cobalt and manganese can be up to 750 hours per million Usually of bromine present in the oxidation reaction, a small portion (usually about 20 - 30%) it is in the ionic form.

Suddenly, the water content of the mixture in the liquid phase in the reactor oxidation was found especially important. It is found that the conditions existing in the vapor phase generated during the oxidation reaction, are more stringent than in the liquid phase, and the main factor contributing to this, is identified as the content of water present in a couple. The amount of water present in the vapor phase, is determined by the number present in the liquid phase. By restricting kolacny allows the use of steel duplex in those parts of the reactor, which comes into contact with the vapor phase. According to a preferred aspect of the image, the moisture content in the mixture of the liquid phase in the oxidation reactor is maintained at a level not exceeding 8 wt.%/wt. in a mixture of water/acetic acid, more preferably 4 to 8 wt.%/wt. This way you can save water content in the vapor phase at a level that allows the use of steel duplex in the area of the vapor phase.

The water content in the reactor of the oxidation is conveniently controlled by removing steam from the reactor, or monocarboxylic acid and water from the steam, the regulation of the water content of the condensed liquid and the liquid return after such a regulation in the reactor as a reverse flow.

Currently, the preferred alloy steel duplex for reactor vessel and/or vessel of the first mold and connected components is alloy Sandvik SAF 2507 (UNS NS 32750), which is commercially available from Sandvik AB, Sandviken, Sweden. It is found that when the action neperesekayuschiesya liquid phase at 191oC for 14 days, as described previously, SAF 2507 alloy exhibits a corrosion rate of 0.01 mm/year, But can be used alloy steels-duplex, metallurgically mn such nchester, UK. The compositions Sandvik type 2507 and cash equivalents shown here in table. 3.

Unexpectedly, in the conditions (composition of the reaction medium and the conditions of increasing temperature and pressure), usually existing in the oxidation reactor and the first mold, the alloy Sandvik SAF 2507 is undergoing more less corrosion than the number of higher alloyed austenitic stainless steels, including Sandvik alloy 2 RK65 (UNS N S 08904), Avesta 254 SMO alloy (UNS N S 31254) and alloy Sandvik Sanicro 28 (UNS N S 08028). In addition, it was found that Sandvik SAF 2507 steel duplex in such conditions, is significantly better corrosion resistance compared to other stainless steels duplex, such as Sandvik 2205 alloy and Ferralium 255 (UNS N S 32550) to the degree that the alloy 2507 has sufficient corrosion resistance, so it is almost an alternative to titanium and titanium alloys in the production of at least parts of the oxidation reactor and the first mold.

Experimental evidence obtained in the measurement of the electrochemical method of corrosion rate, shows that the corrosion rate of alloy 2507 increases with increasing water content in the normal composition of the oxidation reactor, but, if the water content is maintained within the range of 4 to 8 wt.%/mimic with corrosion rate, which may be acceptable, for example below 0.15 mm/year (more preferably 0.1 and particularly preferably 0.05 mm/year). Electrochemical measurements also show that the deviation in the temperature of the oxidation reactor (in the range of 180 - 220oC) and bromine (within 1000 - 2600 hours per million) are relatively less important factor when it comes to the corrosion rate. The technique of electrochemical measurements of corrosion rate are well known (for example, article 223 N "Electrochemical Poise Technigues for Determining Corrosion Rates and Mechanisms", A. N. Rothwell et al., Corrosion 92, the NACE Annual Conference and Corrosion Show available from NACE Products Division PO BOX 218340, Houston, Texas 77218 USA).

Typical installation of obtaining terephthalic acid further comprises an area of extraction of the product recovery section of the solvent, the plot of dehydration and the removal unit and the regeneration of the catalyst; in each of these areas the processes carried out in a medium containing at least hot acetic acid and water, and most cases, bromine, cobalt, manganese, and possibly sodium at different temperatures and pressures. Some of the processes carried out in the presence of acetic acid and water under conditions less stringent temperature and pressure and a lower content of bromine. In such cases, although the usual practice and I stainless steel duplex suitable corrosion resistance. Because the conditions are less stringent, however, such parts of an installation or a full installation can be made of stainless steel-duplex, such as Sandvik 2205 alloy (UNS N S 31803), which, although not included as a possible material for the construction of the oxidation reactor and the first mold (and associated components, such as the top of the vessel, the heat exchanger system steam supply and return system return drain the piping system, pump, various valves and valves and equipment for mixing), found with acceptable corrosion resistance when exposed to liquids, comprising acetic acid and water at temperatures and pressures lower than those that prevail in the oxidation reactor and the first mold.

The composition of the alloy Sandvik 2205 shown in table. 4. It is shown that the steel duplex stainless steel, which are metallurgically mn equivalent and similar to Sandvik alloy 2205, can also be used for these less difficult requirements, such as the equivalent alloys are mostly AFNOR Z3 CND 22.05.AZ, Uranus UR45N, SS 2377 and UNS N S 31803 alloy.

The invention is further illustrated by examples only, with reference to the following examples.

Example 1. In the laboratory the action environment of the liquid phase, having a composition that includes the reaction medium acetic acid/water, present in the first crystallizer typical installation of obtaining terephthalic acid:

Acetic acid: water - 88.01:11.99 wt.%/wt.

Bromine - 994 million hours

Cobalt - 410 million hours

Manganese - 412 million hours

Sodium - 98 hours per million

Samples of rectangular configuration size HH mm are subjected to the influence of the environment of the liquid phase in the autoclave without stirring for 14 days at a temperature of 191oC, which is common to the first mold.

The corrosion rate is determined by the weight loss of the test sample during the period of exposure and found that the corrosion rate is 0.01 mm/year in these conditions.

Under these conditions Sandvik 2205 has a corrosion rate at the level of 0.06 to 0.07 mm/year, whereas, for comparison, 317L stainless steel has a corrosion rate of more than 0.5 mm/year

Tests performed to assess the stability and corrosion resistance of a number of commercially acceptable stainless steels when exposed to them in the conditions typical of those parts of the installation for producing terephthalic acid, which is usually made from titanium and titanium spravki, each sample stainless steel has a size HH mm. effect on the samples in all cases is more than 3 months, and in some cases much longer. The results of these tests are somewhat qualitative in nature, since the measured corrosion rate is distorted by the presence of large losses of materials in the field of welding and can be significantly reduced by applying more satisfactory welding equipment, which is known). In addition, since all of the tested samples are exposed to an increased risk of loss of materials in welding, the results are an indicator of the relative quality of the tested material.

Example 2. The first mold is a series of vessels, which is the crystallization of terephthalic acid from the mother liquor after the oxidation of p-xylene in acetic acid as solvent in the presence of a catalyst system comprising cobalt, manganese and bromine. Conditions prevailing in the first mold, typically include (see tab.1):

The impact of these conditions within 350 days gives the following results (see tab.2):

Of these alloys Sandvik SAF 2507, Sandvik 2205 and Ferralium 255 (F255) are all alloys duplex, while the other alloys is I.

From the preceding it is seen that in the harsh conditions of the liquid phase existing in the first mold (for example, high temperatures and high levels of bromine) SAF 2507 experience lower corrosion than other alloys in the liquid phase. In less severe conditions, the vapor phase, all steel alloys duplex show significantly better corrosion resistance than alloy, austenite alloys.

Example 3. Similar tests conducted in the field of the liquid phase of the first mold over 170 DN when using sample SAF 2507 alloy under the following conditions:

Acetic acid: water - 92 : 8 wt.%

Temperature - 191oC

The metals of the catalyst - 630 am on million

The total content of bromine is 750 hours per million

Ionic bromine - 260 hours per million

In this example, the corrosion rate was found to 0.06 mm/year, it illustrates the impact of reduced water content and bromine in the liquid phase.

Example 4. Another similar test is carried out in the area of the liquid phase of the first mold within 240 Nam again when using the sample SAF 2507 alloy under the following conditions

Acetic acid: water 94 : 6 wt.%

Temperature - 200oC

The metals of the catalyst - 690 am meloche corrosion rate of alloy SAF 2507 found less than 0.01 mm/year, again showing the effect of preserving the low concentration of water in the reaction medium.

Example 5. Sample SAF 2507 alloy are placed in a reactor oxidation to obtain terephthalic acid in the liquid phase p-xylene in acetic acid as solvent in the presence of a catalyst comprising cobalt, manganese and bromine. Conditions existing in the reactor oxidation:

Acetic acid: water is 93 : 7 wt.%

Temperature - 215oC

The metal catalyst is 650 million hours

The total number of bromine - 770 am on million

Ionic bromine - 190 million hours

After exposure to these conditions for 140 DN corrosion rate of alloy 2507 is 0.03 mm/year

1. Device for producing and processing of aromatic carboxylic acids in which the aromatic carboxylic acid is obtained by oxidation in the liquid phase of substituted aromatic compounds such as p-xylene, in the environment of the water-containing lower aliphatic monocarboxylic acid as a solvent, in the presence of a catalyst system comprising cobalt, manganese and bromine containing parts which are exposed when using the effects of water and bromoderma acidic environment of the races is stop which are when using the effects of water and bromoderma environment acidic solvent, made of stainless steel, duplex, alloy nitrogen and molybdenum.

2. Installation under item 1, characterized in that at least those parts of the installation that is exposed to water and bromoderma environment acidic solvent at elevated temperature and pressure, respectively, above 180oC and 8 bar, made from stainless steel-duplex.

3. Installation under item 2, characterized in that part of the installation include the reactor vessel, in which the oxidation reaction in the liquid phase.

4. Installation under item 2, characterized in that part of the installation include the vessel for the first stage of crystallization, which is part of a series of stages of crystallization, in which the controlled crystallization of the aromatic carboxylic acid from the mother liquor.

5. Installation on PP.1 to 4, characterized in that the above-mentioned parts are made of nitrided alloy stainless steel-duplex containing molybdenum, which when exposed neperesekayuschiesya environment of the liquid phase, having a composition, as defined below, at a temperature of 191oIn techrigy acid - 88,01

Water - 11,99

and the catalytic system containing man-1:

Bromine - 944

Cobalt - 410

Manganese - 412

Sodium - 98

6. Installation under item 5, characterized in that the stainless steel duplex manifests in certain conditions, the corrosion rate is not more than 0.04 mm/year.

7. Installation according to p. 6, characterized in that the steel duplex exhibits a corrosion rate of not more than 0.025 mm/year.

8. Installation on PP.1 to 4, characterized in that the stainless steel duplex has the following composition, wt.%:

Carbon is Not more than 0,03

Silicon is Not more than 2.0

Manganese - Not more than 2.0

Phosphorus - Not more than 0.04

Sulfur is Not more than 0.04

Chrome - 24 - 26

Nickel - 5 - 8

Molybdenum - 3 - 4

Nitrogen - 0,2 - 0,3

Tungsten is Not more than 1.0

Copper is Not more than 2.5

Iron - Rest

9. Installation under item 1, characterized in that at least some of the parts of the installation which are outside the reaction vessel, in which the oxidation reaction and which is exposed to the solvent environment containing at least 300 million-1bromine, made of stainless steel-duplex.

10. Installation under item 1, characterized in that the stainless steel duplex SL has the SFOR - Not more than 0.04

Sulfur is Not more than 0.04

Chrome - 21 - 26

Nickel - 4,5 - 8

Molybdenum - 2,5 - 4

Nitrogen - 0,15 - 0,3

Tungsten is Not more than 1.0

Copper is Not more than 2.5

Iron - Rest

11. Method for preparation of aromatic carboxylic acids by oxidation of aromatic compounds such as p-xylene, in the environment of the water-containing lower aliphatic monocarboxylic acid at a temperature of 180 - 220oC and a pressure of 8 to 20 bar in the presence of a catalytic oxidation system comprising cobalt and manganese, followed by feeding the mother liquor and the above-mentioned aromatic carboxylic acid from the oxidation reactor to the stage of crystallization, which carried out a controlled crystallization, while the oxidation reactor and/or crystallization is made of stainless steel-duplex, characterized in that the catalytic system further includes bromine, and steel-duplex, which made the surface of the reactor, which carry out the oxidation process and/or at least the first stage of crystallization, and which is in contact with the environment bromine and water, doped with nitrogen, contains molybdenum and consists of the following composition, wt.%:

Carbon is Not more than 0,03

Silicon is Not more than 2.0
Molybdenum - 3 - 4

Nitrogen - 0,2 - 0,3

Tungsten is Not more than 1.0

Copper is Not more than 2.5

Iron - Rest

the conditions of the process, in particular the water content, which is supported at the level of 3 to 10 wt.% relative to the total content of monocarboxylic acid and water, and bromine in a reaction medium, is controlled so that the corrosion rate mentioned nitrided alloy steel duplex when exposed to the specified reaction medium does not exceed 0.15 mm/year.

12. The method according to p. 11, characterized in that the process conditions are controlled so that the corrosion rate mentioned steel duplex having the above composition, when exposed to the specified reaction medium containing bromine and water, and an acid solvent, would not exceed 0.1 mm/year.

13. The method according to p. 11, characterized in that the reactor, and/or the mold, and/or portions thereof, located within or associated with the reactor and/or mold, which are exposed to the specified reaction medium, under specified temperature and pressure, are made of stainless steel-duplex, which under such conditions has a corrosion rate of not more than 0.15 mm/year.

14. The method according to PP. 11 to 13, characterized in that regiono-resistant, than steel duplex and steel duplex is applied by coating to the specified less corrosion-resistant material.

15. The method according to p. 11, characterized in that the water content in the reaction medium oxidation reactor maintained within the range of 4 to 8 wt.% relative to the total content of monocarboxylic acid and water.

16. The method according to PP.11 to 13, characterized in that the water content in the oxidation reactor is controlled by removing steam from the reactor, or monocarboxylic acid and water from the steam, regulation of water content in the condensed liquid and returning the condensed liquid after such regulation in the reactor, as reverse flow.

17. The method according to p. 11, characterized in that the water in the liquid phase of the reaction mixture is not more than 8 wt.%.

18. The method according to PP.11 to 13 and 17, characterized in that the oxidation reaction is performed under conditions that provide crude terephthalic acid having a content of 4-CBA in the range of 300 to 7000 million-1regarding the resulting terephthalic acid.

Priority points:

21.05.92 on PP.1 - 4, 8, 10;

01.03.93 on PP.5 - 7, 9, 11 - 18.

 

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