ACETONE STORAGE

Abstract

An acetone storage tank or acetone transfer pipe comprising stainless steel in which the amount of Cr is in the range 10.5 wt % to 20 wt %; the amount of Ni is 9 wt %, and the amount of Mo is 2.75%Mo0 wt %, of the stainless steel.

Claims

1. (canceled)

2. (canceled)

3. The process of claim 12, wherein the content of phosphorus in the stainless steel is equal to or higher than 0.02%.

4. The process of claim 12, wherein the content of sulphur in the stainless steel is equal or higher than 0.02%

5. The process of claim 12, wherein the stainless steel is doped with Cu and/or Ti and/or Nb.

6. The process of claim 12, wherein the stainless steel comprises 11 to 18.5 wt % Cr, 0 to 2.5 wt % Mo, and 9 to 15 wt % Ni.

7. The process of claim 12, wherein the stainless steel comprises 14 to 18.5 wt % Cr, 0.5 to 2.5 wt % Mo, and 9 to 13.5 wt % Ni.

8. The process of claim 12, wherein the stainless steel is 1.4306, 1.4541 or 1.4571 steel.

9. The process of claim 12, wherein the level of diacetone alcohol within the stainless steel storage tank or acetone transfer pipe is always below 80 ppm.

10. (canceled)

11. (canceled)

12. A process for storing acetone, comprising: putting acetone having a diacetone alcohol content of less than 25 ppm and/or a mesityl oxide content of less than 1 ppm in a stainless steel storage tank or acetone transfer pipe comprising: stainless steel with an amount of Cr in the range 10.5 wt % to 20 wt %, an amount of Ni of greater than or equal to 9 wt %, and an amount of Mo that is less than or equal to 2.75 wt % and greater than or equal to 0 wt %, of the stainless steel; and storing said acetone within the stainless steel storage tank or acetone transfer pipe for a period of at least one month during which time the stainless steel storage tank or acetone transfer pipe is repeatedly exposed to a temperature of at least 25 C. such that the amount of diacetone alcohol in the acetone after one month is below 80 ppm and/or that the amount of mesityl oxide in the acetone after one month is below 5 ppm.

13. A process for inhibiting the formation of impurities in acetone, sa process comprising storing acetone in a storage tank comprising: stainless steel with an amount of Cr in the range 10.5 wt % to 20 wt %, an amount of Ni of greater than or equal to 9 wt %, and an amount of Mo that is less than or equal to 2.75 wt % and greater than or equal to 0 wt %, of the stainless steel.

14. A process for inhibiting the formation of acetone oligomers and their dehydration products in acetone, said process comprising storing acetone in a storage tank, said storage tank comprising: stainless steel with an amount of Cr in the range 10.5 wt % to 20 wt %, an amount of Ni of greater than or equal to 9 wt %, and an amount of Mo that is less than or equal to 2.75 wt % and greater than or equal to 0 wt %, of the stainless steel.

15. (canceled)

16. The process of claim 12 comprising storing said acetone within the stainless steel storage tank or acetone transfer pipe for a period of at least one month during which time the stainless steel storage tank or acetone transfer pipe is repeatedly exposed to a temperature of at least 25 C. but no more than 50 C.

17. The process of claim 12, wherein the stainless steel comprises 14 to 18.5 wt % Cr, 0 to 2.5 wt % Mo, and 9 to 13.5 wt % Ni.

18. The process of claim 14, wherein the process inhibits the formation of diacetone alcohol and/or mesityl oxide.

Description

[0072] The invention will now be described with reference to the following non limiting examples and figures.

[0073] FIG. 1 is an illustration of total impurities vs time at 25 C.

[0074] FIG. 2 is an illustration of total impurities vs time at 50 C.

[0075] FIG. 3 shows the number of newly formed compounds on storage at these two temperatures.

[0076] FIG. 4 is an illustration of DAA formed vs time at 25 C.

[0077] FIG. 5 is an illustration of DAA formed vs time at 50 C.

[0078] FIG. 6 is an illustration of MO formed vs time at 25 C.

[0079] FIG. 7 is an illustration of MO formed vs time at 50 C.

[0080] FIG. 8 is an overview of the impurity formation during acetone storage in presence of different steel types.

[0081] FIG. 9 is an overview of the impurity formation during acetone storage in presence of different steel types.

EXAMPLES

[0082] Various different stainless steel bars are tested along with carbon steel and cast iron as control experiments. The storage temperatures were defined at 25 C. and 50 C. The metals were used as bars and the surface area of each bar was approximately the same. Table 1 summarises the main elemental contents of the steels employed in the examples.

TABLE-US-00001 TABLE 1 Used steel samples in the sample sets for acetone storage with its chemical analysis Metal Type elem. GG Con- 9055 CK 45 Hastelloy tent Cast Carbon C22- % iron Steel 1.4306 1.4571 1.4462 1.4541 2.4602 C 3.44 0.43 0.027 0.03 0.019 0.019 0.005 Si 1.77 0.29 0.56 0.47 0.4 0.51 0.026 Mn 0.47 0.58 1.34 1.49 1.51 1.91 0.26 Cr 0.02 0.13 18.15 14.82 22.36 17.15 21.39 Ni 0.18 0.09 10.7 11.58 5.72 9.65 n.a. Mo 0 0.05 n.a 2.16 3.17 n.a. 13.49

[0083] The storage experiments were carried out in transparent glass bottles, stored in the dark. The 50 C. samples were stored in a drying oven. Every few days samples were taken out and analysed by gas chromatography. Storage in the dark was chosen to minimize influence of daylight, especially UV-light and to mimic industrial reality as acetone is stored in the dark. As a control, an acetone sample was stored in brown bottles without steel.

[0084] The GC analysis was carried out using a GC Perkin Elmer, detection with FID and as column DB-Wax 30 m 0.25 ID.

TABLE-US-00002 The GC analysis of the starting acetone is shown below. Impurity ppm DAA 14 Mesityloxide 0 Total Impurities 148

Results

[0085] FIGS. 1 and 2 show the total amount of impurities formed in the acetone during storage over time. The highest increase occurs with cast iron (GG9950).

[0086] At 50 C. an extreme increase in the amount of impurities takes place. Starting from a total amount of 150 ppm the amount raises up to 450 ppm. The two samples with highest rise are cast iron (GG9950) and carbon steel (CK45). The best inhibition of impurities is detected with 1.4306 and 1.4571 steel grades.

[0087] Besides the six known impurities (acetaldehyde, propionaldehyde, methanol, DAA, ethanol and benzene) in all samples new peaks are formed during storage. FIG. 3 shows the number of new peaks in the GC chromatogram. At 25 C. between 6 and 15 new peaks occur, at 50 C. up to 23 new peaks. In most cases the amount is smaller than 10 ppm.

[0088] In FIG. 4 at 25 C. the time dependent formation of diacetone alcohol is shown. At 25 C. no significant rise is visible after 3 months (90 days), except for the sample with cast iron. Here DAA is continuously formed and achieves 100 ppm after 4 months. In case of the sample with 1.4541 a low increase takes place.

[0089] At 50 C. (FIG. 5) the sample without steel increases significantly from 14 to 200 ppm in 4 months. Probably the slightly alkaline pH value plays an important role. The sample CK45 also shows a high amount of DAA after 4 months. All samples with stainless steel have a lower formation rate. The best steel type here is 1.4571. All samples stored at 50 C. contain latest after 3 months more than 80 ppm DAA, which is the preferred upper limit of the specification.

[0090] FIG. 6 demonstrates the same effect for mesityloxide (MO). After a time of 75 days at 25 C. and 30 days at 50 C. (FIG. 7) the amount of mesityloxide increases to detectable amounts. At 25 C. the formation is rather slow and stays for 4 months under the preferred upper limit of 5 ppm. However, at 50 C. the limit of MO is surpassed after 70 days. The best steel type here is 1.4571, same as for DAA formation.

Example 2

[0091] The results described above were obtained by continuous sampling of the acetone from the storage vessel. To determine whether continuous sampling was having an effect, a 2nd sample set was stored under the same conditions but without periodical sampling. The bottles were closed over 104 storage days and after opening an analysis was done. The results in comparison to the 1st sample set are shown in Table 4 (114 days=example 1). There is a small but insignificant difference in the storage days.

[0092] In case of MO in the 2nd sample set, except with GG9950, the formation of MO is approximately zero, although the DAA formation shows the same growth as the 1st sample set. Two possible reasons are limited oxygen content due to closed storage and no water elimination at DAA due to missing exchange of the water, because every opening of the bottles changes the humidity in the gas phase. Through this result the sum amount of the new formed impurities is lower as well and the number of impurities is also lower.

TABLE-US-00003 after 114 days MO DAA Total number of No. (2) after 104 days.sup.1) ppm new formed subst. starting point 0 14 148 0 2009- Without 25 190 355 14 0085-01 without (2) 1 220 385 11 2009- GG9950 69 212 430 23 0085-02 GG9950 (2) 70 195 413 13 2009- CK45 37 237 406 16 0085-03 CK 45 (2) 1 198 390 4 2009- 1.4306 13 128 280 12 0085-04 1.4306 (2) 1 198 397 7 2009- 1.4462 17 156 392 14 0085-07 2009- 1.4571 9 100 238 10 0085-05 1.4571 (2) 1 190 389 7 2009- 1.4541 17 120 262 13 0085-06 2009- 2.4602 18 154 317 12 0085-08 2.4602 (2) 0 185 387 7

[0093] The acetone storage experiment in presence of different steel types shows depending on the storage temperature (25 C. and 50 C.) significant differences. At 25 C. the formation of the main by-product diacetone alcohol (DAA) takes place especially for cast iron (GG9950). These materials perform worse than if there is no steel at all. In all samples new impurities were formed during the storage. The highest amounts were detected in the samples with the carbon steel CK 45, and cast iron (GG9950).

[0094] At 50 C. the formation of the main by-product DAA occurs. Here, the temperature rise is enough to accelerate the impurity formation. After a 2 month storage at 50 C. the concentration of DAA pass the specification of max. 80 ppm. At 50 C. the number of new formed impurities increases, especially in case of cast iron. 23 new impurities were formed.

[0095] It should be noted that Hastelloy steels (2.4602) containing large amounts of Cr and Mo are prohibitively expensive for use in the formation of large tanks. The fact that the steels of the present invention perform as well as Hastelloy steels is remarkable.