GB1589013A - Process for preparing ammonium isobutyrate - Google Patents

Description

(54) PROCESS FOR PREPARING AMMONIUM ISOBUTYRATE (71) We, W. R. GRACE & CO., a corporation organized and existing under the laws of the State of Connecticut, United States of America, of Grace Plaza, 1114 Avenue of the Americas, New York, New York 10036, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the production of ammonium isobutyrate.

Zuffanti, J. Amer. Chem. Soc., 1941, 63, 3123-3124 describes a method for preparing an ammonium salt of an alkanoic acid. The preparation of such salts is also described by U.S. Patents No. 3,786,086 (Skov et al) and No. 3,899,588 (Skov et al). These two Patents and also U.S. Patents Nos. 3,958,009 (Lapore et al) and 3,806,600 (Lapore et al) teach uses of ammonium and other salts of alkanoic acids.

The process of the present invention for preparing a mixture of ammonium isobutyrate, water and optionally isobutyric acid, comprises: (a) forming a first admixture comprising ammonia, at least the stoichiometric amount of isobutyric acid and water in a tubular reaction zone; (b) forming a second admixture comprising the ammonium isobutyrate, any unreacted isobutyric acid and water by passing the first admixture through the tubular reaction zone at a temperature effective for forming the ammonium isobutyrate and above the crystallization temperature of the second admixture; (c) when the second admixture leaving the tubular reaction zone has a temperature above 1800F. (84"C.), passing the second admixture leaving the tubular reaction zone through a tubular cooling zone in which the second admixture is cooled to a temperature at which the ammonia vapour pressure over the second admixture is reduced substantially to zero, and above the crystallization temperature of the second admixture; and (d) recovering the cooled second admixture.

Preferably the first admixture contains water and a stoichiometric excess of the isobutyric acid, the particularly preferred mole ratios of ammonia to isobutyric acid to water in the first admixture being 1-1.36 :1.12- 1.70 :3.54-6.61.

The first admixture is preferably formed by admixing the ammonia, the isobutyric acid, and water in a mixing cross communicating with the tubular reaction zone through an inlet port of the tubular reaction zone. Alternatively the ammonia and water may be admixed in a mixing Tee communicating with the tubular reaction zone through an inlet port of the tubular reaction zone and fed from the mixing Tee into the tubular reaction zone.

The isobutyric acid is preferably fed into the tubular reaction zone through a second inlet port positioned downstream of the first inlet port.

In one preferred embodiment the first admixture comprising water, the ammonia, and an excess of the isobutyric acid is formed in a vertical tubular reaction zone having: (i) a first lower portion; (ii) a second lower portion positioned above the first lower portion; (iii) a middle portion positioned above the second lower portion; and (iv) an upper portion positioned above the middle portion, and (A) the water is fed into the reaction zone through a water inlet port positioned in the first lower portion of said reaction zone; (B) the ammonia is fed into the reaction zone through an ammonia inlet port positioned in the second lower portion of said reaction zone; and (C) the isobutyric acid is fed into the reaction zone through an isobutyric acid inlet port positioned in the middle portion of said reaction zone, the water, anhydrous ammonia, and isobutyric acid being fed into the reaction zone at rates effective to prevent the isobutyric acid from descending into the second lower portion of the said elongated vertical reaction zone; and the second admixture is removed from the upper portion of the reaction zone.

The residence time of the admixture containing isobutyric acid and ammonia in the tubular reaction zone (tubular reactor) is generally about 10-25 seconds but it can be less than 10 seconds or more than 25 seconds.

The feedstock generally enters the reaction zone at about 60-1400F (15-600C), but this temperature range is not critical. The product generally exits the reaction zone at about 160-2600F (70--1300C), but this temperature range is not critical. Product leaving the reaction zone is cooled generally to about 100-1800F (37-840C) in a tubular cooling zone (tubular cooler). However, this temperature range is not critical. If product leaving the reactor zone is already within this temperature range (ca. 100- 1800F) (37-840C) a separate cooling step is unnecessary.

The tubular reactor (tubular reaction zone) used in the process of this invention can be a vertical reactor, a horizontal reactor, or an inclined reactor. The tube comprising the reactor can be a straight tube, a curved tube, or a spiral or helical tube. The tube can be insulated and/or jacketed to receive heat from a heating fluid (e.g., water or steam) or to provide cooling (if required) from a cooling fluid such as water or oil.

The cooling zone can preferably be a jacketed extension of the tubular reactor having a separate. jacket (if the tubular reactor is jacketed) through which a cooling fluid can be circulated. Alternatively the cooling zone can be a tank which is jacketed to provide cooling or a tank with cooling coils therein.

Mixing the ammonia and the isobutyric acid with each other (and with water) to form a reaction mixture to pass through the tubular reactor can be accomplished via an inline mixer such as a mixing cross, one or more mixing Tees, one or more mixing Y's, or the like.

Alternatively, the water can be fed into the tubular reactor at, or near, one end (the inlet end), ammonia can be fed into the tubular reactor a short distance (e.g., 1-20 cm) downstream of the water inlet, and the isobutyric acid can be fed into the tubular reactor a short distance (e.g., 10-20 cm or more) downstream of the ammonia inlet.

Where using one or more inline mixers, such mixers can, if desired, be insulated or jacketed to provide heating or cooling.

It will be readily apparent to those skilled in the art that the reactants (plus water) can be premixed to form a reaction mixture which can be kept in a storage zone (e.g, a tank) maintained at a temperature above the crystallization temperature (or solidification temperature) of the reaction mixture. Said reaction mixture can be pumped (or passed by gravity-induced flow) through the tubular reactor and when necessary the subsequent cooling zone. No particular advantage is however gained by using this technique.

Where a vertical tubular reaction zone is used having a first lower portion, a second lower portion, a middle portion, and an upper portion, the first lower portion of such vertical tubular reaction zone (vertical tubular reactor) which also has a bottom and a top can extend upward from the bottom of the said tubular reaction zone to include about 1/20 to 1/10 of the total height thereof. The second lower portion of said vertical tubular reaction zone can extend upward from immediately above the first lower portion of said reaction zone for about 1/5 to 1/3 of the total height thereof. The middle portion of the vertical tubular reaction zone can extend upward from immediately above the second lower portion of said reaction zone for about 1/3 to 1/2 of the total height thereof, and the upper portion of said tubular reaction zone comprises the remainder thereof (i.e., that portion of the said reaction zone which is above the middle portion).

It will also be readily apparent to those skilled in the art that at least part of the ammonia and water can be provided as an aqueous ammonia solution. However, it is generally preferred to use anhydrous liquid ammonia as the ammonia source and water by itself as the water source.

It is preferred that flow rates be such as to maintain turbulent flow through the tubular reaction zone and the tubular cooling zone.

The mole ratios of the reactants (and water) recited in certain of the above embodiments are important but not critical.

The invention will now be described in more detail with reference to the accompanying drawings, in which Figures 1 and 3 are schematic diagrams of vertical tubular reactors useful for preparing ammonium isobutyrate, and Figure 2 is a schematic diagram of an inclined tubular reactor useful for preparing ammonium isobutyrate.

Referring to Figure 1: Water enters the first lower portion 11 of the vertical reactor (vertical reaction zone) shown generally at 15 via line 5 and pump 10. Ammonia enters the second lower portion 12 of said vertical reactor via line 20 and pump 25. The isobutyric acid (RCOOH) enters the middle portion 13 of said vertical reactor via line 30 and pump 35. The product exits from the top 14 of said vertical reactor via line 40 and passes into the cooling zone shown generally at 45. Cooling water enters jacket 65 of said cooling zone via line 55 and pump 60. The cooling water exits jacket 65 via line 70 and regulatory valve 75 which is used to restrict the rate of flow of the cooling water through the jacket. While the drawing shows countercurrent flow of the cooling water, concurrent flow is operable. Cooled product exits said cooling zone via line 50 and passes to a product storage tank (not shown).

Referring to Figure 2: Isobutyric acid (,RCOOH) enters mixing Tee 210 (which is an integral part of inclined reactor (inclined reaction zone) 220) via line 200 and pump 205. Ammonia enters mixing Tee 210 via line 225 and pump 230. Insulation 215 covers both inclined reactor 220 and mixing Tee 210.

The admixture of isobutyric acid and ammonia formed in mixing Tee 210 passes through inclined reactor 220 and into a cooler or cooling zone 235 (which is a continuation of inclined reactor 220 with jacket 240 (in place of insulation) surrounding it). Cooling water passes into jacket 240 via line 245 and pump 250. The cooling water exits jacket 240 via line 255 and regulatory valve 260. Although the drawing shows countercurrent flow of the cooling water, concurrent flow is operable. Cooled product exit cooling zone 235 passes via line 265 to a product storage tank (not shown).

Referring to Figure 3: Water enters first lower portion 311 of the vertical reactor (vertical reaction zone) shown generally at 315 via line 305 and pump 310. Ammonia enters second lower portion 31 2 of said vertical tubular reactor via line 320 and pump 325. Isobutyric acid (RCOOH) enters middle portion 316 of said vertical tubular reactor via line 330 and pump 335. Insulation 313 covers said vertical tubular reactor. Product leaves upper portion 317 of said vertical reactor and passes into the cooling zone shown generally at 345 (which is a continuation of said vertical tubular reactor with jacket 365 (in place of insulation) surrounding it).

Cooling water passes into jacket 365 via line 355 and pump 350. The cooling water exits jacket 365 via line 370 and regulatory valve 375. Cooled product exits said cooler via line 360 and passes to a product storage tank (not shown).

The invention is illustrated by the following Examples.

EXAMPLE 1.

The run of this Example was made using an apparatus of the type represented by Figure 1 except that the vertical tubular reactor (shown generally at 15) and the cooling zone (shown generally at 45) were insulated with a magnesia insulating composition.

Water was continuously charged into first lower portion 11 of a vertical tubular reactor (vertical tubular reaction zone) shown generally at 15 via line 5. Liquid anhydrous ammonia was continuously charged into second lower portion 12 of said vertical tubular reactor via line 20, and isbutyric acid was continuously charged into middle portion 16 of said vertical tubular reactor via line 30.

Product (an aqueous solution comprising water, ammonium isobutyrate, and unreacted excess isobutyric acid) continuously passed from upper portion 14 of said vertical reactor into the jacketed cooling zone shown generally at 45. Cooled product continuously passed from said cooling zone via line 50 to a product receiver. Cooling water continuously passed through jacket 65 which surrounded cooling zone.

Flow rates were: Material Grams per Minute Water 29.5 Ammonia 6.1 Isobutyric Acid 36.0 Water and isobutyric acid were charged into the vertical tubular reactor at about 75 0F (240C) and the ammonia was charged into said reactor at a pressure of 6 pounds per square inch (6 psig, 414 mbar gauge).

Linear velocity in the vertical tubular reactor was 4.74 feet per minute (1.4 metres per minute) and residence time in the said reactor was 11.6 seconds.

The temperature of the ammonia-water mixture (aqueous ammonia) just below the middle portion of the vertical tubular reactor was 152 F (670C), the temperature of the product leaving the vertical tubular reactor (i.e., just before entering the cooler (cooling zone) was 235 F (113"C), and the temperature of the product leaving the cooler 45 was 156"F (690C).

Conversion (one pass yield) was substantially complete (i.e., 100% of theory).

EXAMPLE 2.

The general method of Example 1 was repeated. In this instance flow rates were: Material Grams per Minute Water 40.8 Ammonia 9.2 Isobutyric Acid 50.1 The water and isobutyric acid were charged into the vertical tubular reaction zone at about 75"F (240 C), and ammonia was charged into said reaction zone at a pressure of 6 psig (414 mbar gauge). Linear velocity in the vertical tubular reactor was 6.6 feet per minute (2 metres per minute) and residence time was 8.4 seconds.

The temperature of the ammonia-water mixture (aqua ammonia) just below the middle portion of the vertical tubular reaction zone was 148"F (64"C), the temperature of the product leaving the vertical tubular reaction zone was 228"F (1090C), and the temperature of the product leaving the cooler was 164"F (73"C).

Conversion was substantially complete.

Claims (8)

WHAT WE CLAIM IS:

1. A process for preparing a mixture of ammonium isobutyrate, water, and optionally isobutyric acid which comprises (a) forming a first admixture comprising ammonia, at least the stoichiometric amount of isobutyric acid and water in a tubular reaction zone; (b) forming a second admixture comprising the ammonium isobutyrate, any unreacted isobutyric acid and water by passing the first admixture through the tubular reaction zone at a temperature effective for forming the ammonium isobutyrate and above the crystallization temperature of the second admixture; (c) when the second admixture leaving the tubular reaction zone has a temperature above 1800F (840C), passing the second admixture leaving the tubular reaction zone through a tubular cooling zone in which the second admixture is cooled to a temperature at which the ammonia vapour pressure over the second admixture is reduced substantially to zero, and above the crystallization temperature of the second admixture; and (d) recovering the cooled second admixture.

2. Process according to claim 1 in which the mole ratio of ammonia to isobutyric acid to water in the first admixture is 1-1.36 1.12-1.70 : 3.54-6.61.

3. Process according to claim 1 or 2 in which the ammonia and water are admixed in a mixing Tee communicating with the tubular reaction zone through an inlet port of the tubular reaction zone and fed from the mixing Tee into the tubular reaction zone.

4. Process according to claim 3 in which the isobutyric acid is fed into the tubular reaction zone through a second inlet port positioned downstream of the first inlet port.

5. Process according to any of claims 1 to 4 in which the first admixture comprising water, the ammonia, and an excess of the isobutyric acid is formed in a vertical tubular reaction zone having: (i) a first lower portion, (ii) a second lower portion positioned above the first lower portion, (iii) a middle portion positioned above the second lower portion; and (iv) an upper portion positioned above the middle portion, and (A) the water is fed into the reaction zone through a water inlet port positioned in the first lower portion of said reaction zone; (B) the ammonia is fed into the reaction zone through an ammonia inlet port positioned in the second lower portion of said reaction zone; and (C) the isobutyric acid is fed into the reaction zone through an isobutyric acid inlet port positioned in the middle portion of said reaction zone, the water, anhydrous ammonia, and isobutyric acid being fed into the said reaction zone at rates effective to prevent the isobutyric acid from descending into the second lower portion of the said elongated vertical reaction zone; and the second admixture is removed from the upper portion of the reaction zone.

6. Process according to claim 1 substantially as hereinbefore described with reference to Figure 1, 2, or 3 of the accompanying drawings.

7. Process according to claim 1 substantially as described in Example 1 or 2.

8. A mixture of ammonium isobutyrate water and optionally isobutyric acid when produced by the process of any of the preceding claims.