Pentenenitrile isomerization

Abstract

Pentenenitrile oligomers formed in a process for isomerizing cis-2-pentenenitrile to 3-pentenenitrile are minimized in the presence of an aluminum oxide catalyst. The process comprises providing an aluminum oxide catalyst having an alkali metal and/or alkaline earth metal and/or iron content, measured in the form of alkali metal oxide and/or alkaline earth metal oxide and/or iron oxide, respectively of less than 5000 ppm by weight.

Claims

1. A method for minimising the amount of pentenenitrile oligomers formed in a process for isomerizing cis-2-pentenenitrile to 3-pentenenitrile in the presence of an aluminium oxide catalyst; said method comprising isomerizing the cis-2-pentenenitrile in the presence of an aluminium oxide catalyst comprising an alkali metal and/or alkaline earth metal and/or iron, wherein the alkali metal and/or alkaline earth metal and/or iron content of the aluminum oxide catalyst, measured in the form of alkali metal oxide and/or alkaline earth metal oxide and/or iron oxide, respectively, is less than 5000 ppm by weight of the aluminum oxide catalyst, wherein the aluminum oxide catalyst comprises sodium, and wherein the sodium content is at least 5.5 ppm and less than 10 ppm by weight of the aluminum oxide catalyst.

2. The method according to claim 1 wherein the amount of pentenenitrile oligomers formed in the process for isomerizing cis-2-pentenenitrile to 3-pentenenitrile is less than 300 ppm by weight for every 10 wt % of cis-2-pentenenitrile starting material which is converted to 3-pentenenitrile and trans-2-pentenenitrile products.

3. The method according to claim 1, wherein the pentenenitrile oligomers are C10-dinitriles.

4. The method according to claim 1, wherein the aluminium oxide catalyst has an alkali metal content, measured in the form of alkali metal oxide, of less than 5000 ppm by weight of the aluminum oxide catalyst.

5. The method according to claim 3, wherein the aluminium oxide catalyst has an alkaline earth metal content, measured in the form of alkaline earth metal oxide, of less than 5000 ppm by weight of the aluminum oxide catalyst.

6. The method according to claim 3, wherein the aluminium oxide catalyst has an iron content, measured in the form of iron oxide of less than 5000 ppm of the aluminum oxide catalyst.

7. The method according to claim 1, wherein the aluminium oxide catalyst has an alkali metal and alkaline earth metal content, measured in the form of alkali metal oxide and alkaline earth metal oxide of less than 5000 ppm by weight of the aluminum oxide catalyst.

8. The method according to claim 1, wherein the alkali and alkaline earth metal content of the aluminium oxide catalyst is less than 1000 ppm by weight of the aluminum oxide catalyst.

9. The method according to claim 1, wherein the alkali metal is selected from sodium or potassium and the alkaline earth metal is selected from calcium or magnesium.

10. The method according to claim 1, wherein the aluminium oxide catalyst has an alkali metal and alkaline earth metal and iron content, measured in the form of alkali metal oxide, alkaline metal oxide and iron oxide, of less than 5000 ppm by weight of the aluminum oxide catalyst.

11. The method according to claim 1, wherein the isomerization is carried out in the liquid phase.

12. The method according to claim 1, wherein the isomerization is carried out at a temperature in the range from 50 C. to 250 C.

13. The method according to claim 1, wherein the isomerization is carried out at a temperature in the range from 120 C. to 200 C.

14. The method according to claim 1, wherein the ratio of C10-dinitriles formed (wt %)/total of 3-pentenenitriles and trans-2-pentenenitriles (PNs) formed (wt %) is about 350 or less.

15. The method according to claim 1, wherein the sodium content, measured in the form of sodium oxide (Na2O), is less than 8 ppm by weight of the aluminum oxide catalyst.

Description

DESCRIPTION OF THE FIGURES

(1) The invention will now be described further by reference to the following figures and examples which are not intended to be limiting on the scope of the claim.

(2) FIG. 1 illustrates the correlation between the formation of byproducts due to cis-2-pentenenitrile dimerization and the sodium content of the aluminum oxide catalysts of examples 1 to 6; and

(3) FIG. 2 illustrates the correlation between cis-2-pentenenitrile conversion and selectivity to 3-pentenenitriles using the aluminium oxide catalysts of Examples 7 to 15 which have varying sodium contents.

EXAMPLES

Example 1

(4) The experiment was conducted in a 10 mL serum bottle, using a temperature-regulated aluminum heating block. Mixing was accomplished using a magnetic stir bar. The heating block was enclosed in a nitrogen purge box. Serum bottles were charged with F-200 (commercially available from Alcoa) aluminum oxide 0.5 g, and cis-2-pentenenitrile (4.5 grams) inside a glove-box and then transferred to the heating block at the beginning of the experiment. The temperature of the heating block was maintained at 100 C. Samples were then removed at the desired intervals for analysis by gas chromatography.

Example 2

(5) Example 1 was repeated except that AL-4126 aluminum oxide (commercially available from Engelhard) was used as the catalyst.

Example 3

(6) Example 1 was repeated except that AL-3996 aluminum oxide (commercially available from Engelhard) was used as the catalyst.

Example 4

(7) Example 1 was repeated except that AL-3995 aluminum oxide (commercially available from Engelhard) was used as the catalyst.

Example 5

(8) Example 1 was repeated except that Catalox SCFa-140 aluminum oxide (commercially available from Sasol) was used as the catalyst.

Example 6

(9) Example 1 was repeated except that sodium-modified aluminum oxide (Na/Al.sub.2O.sub.3) was used as the catalyst.

(10) Preparation of Sodium Modified Alumina:

(11) A ceramic mortar and pestle was used to prepare a sodium-modified aluminum oxide catalyst material that contained 1 percent by weight (wt %) sodium based on the combined weight percent of the precursor aluminum oxide and sodium hydroxide. The material was then dried under vacuum at minus 25 inches of mercury at 300 C. for 18 hours, and then allowed to cool under nitrogen prior to evaluation.

(12) The results of the evaluation of Examples 1 to 6, which have varying sodium contents, are shown in Table 1 below.

(13) TABLE-US-00001 TABLE 1 Na.sub.2O DDN (wt %)/PNs Example Catalyst (ppm).sup. formed (wt %) 1 F-200 3000 254 2 AL-4126 800 97 3 AL-3996 600 131 4 AL-3995 600 112 5 Catalox SCFa- 5.5 36 140 6 Na/Al.sub.2O.sub.3 10000.sup. 727 .sup.levels of Na.sub.2O as reported from the manufacturer. .sup.Aldrich alumina + 1 wt % NaOH, and calcined at 300 C./16 hours prior to evaluation. PN formed = trans-3-pentenenitrile, cis-3-pentenenitrile, and trans-2-pentenenitrile formed.

(14) The data presented in Table 1 show the effect of varying the sodium content of aluminum oxide catalysts used for isomerization of cis-2-pentenenitrile to 3-pentenenitriles. The data show that the formation of by-products formed by dimerization of 2-PN (i.e. C10-dinitriles) increases linearly as sodium content increases. This can also be seen in FIG. 1.

Example 7

(15) The experiment was conducted in a 10 mL serum bottle, using a temperature-regulated aluminum heating block. Mixing was accomplished using a magnetic stir bar. The heating block was enclosed in a nitrogen purge box. Serum bottles were charged with F-200 (commercially available from Alcoa) aluminum oxide 0.5 g, and cis-2-pentenenitrile (4.5 grams) inside a glove-box and then transferred to the heating block at the beginning of the experiment. The temperature of the heating block was maintained at 50 C. Samples were then removed at the desired intervals for analysis by gas chromatography.

Example 8

(16) Example 7 was repeated except that the temperature of the heating block during the experiment was maintained at 75 C.

Example 9

(17) Example 7 was repeated except that the temperature of the heating block during the experiment was maintained at 100 C.

Example 10

(18) Example 7 was repeated except that Catalox SCFa-140 alumina (commercially available from Sasol) was used as the catalyst, and the temperature of the heating block during the experiment was maintained at 50 C.

Example 11

(19) Example 10 was repeated except that the temperature of the heating block during the experiment was maintained at 75 C.

Example 12

(20) Example 10 was repeated except that the temperature of the heating block during the experiment was maintained at 100 C.

Example 13

(21) Example 7 was repeated except that AL-3996 alumina (commercially available from Engelhard) was used as the catalyst, and the temperature of the heating block during the experiment was maintained at 50 C.

Example 14

(22) Example 13 was repeated except that the temperature of the heating block during the experiment was maintained at 100 C.

Example 15

(23) Example 7 was repeated except that Catalox SBa-200 alumina (commercially available from Sasol) was used as the catalyst, and the temperature of the heating block during the experiment was maintained at 50 C.

(24) The results of Examples 7 to 15 are shown in Table 2 below.

(25) TABLE-US-00002 TABLE 2 % C2PN Na.sub.2O Temperature conversion % Selectivity Example Catalyst (ppm).sup. ( C.) (X) (3PNs/X) 7 F-200 3000 50 1.0 84.1 2.4 79.6 4.2 76.5 0.5 84.0 0.6 82.0 8 F-200 3000 75 2.5 75.1 5.5 70.6 9.7 67.4 9 F-200 3000 100 10.4 63.9 17.1 59.8 26.8 55.1 10 SCFa 5.5 50 0.1 100 0.4 97.8 0.8 96.5 1.2 93.8 2.4 91.2 4.1 86.3 11 SCFa 5.5 75 2.5 91.0 4.5 87.0 7.1 81.6 12 SCFa 5.5 100 11.6 82.1 17.3 75.7 24.7 67.9 13 AL- 600 50 0.8 95.1 3996 1.4 92.7 2.4 90.2 14 AL- 600 100 8.3 83.3 3996 14.3 75.7 22.9 67.8 15 SBa 150 100 5.1 88.1 9.1 82.4 15.3 74.8 .sup.Levels of Na.sub.2O as reported from the manufacturer.

(26) The data presented in Table 2 show the effect of varying sodium content of aluminum oxide catalysts used for isomerization of cis-2-pentenenitrile to 3-pentenenitrile. The data show that selectivity to 3-pentenenitriles decreases as the sodium content of the aluminum oxide catalysts increases.

(27) Examples 16 to 19 were performed in order to assess the impact of alkali and alkaline earth modifications to aluminium oxide catalysts used to catalyze the isomerization of cis-2-pentenenitrile.

Example 16

(28) The experiment was conducted in a 10 mL serum bottle, using a temperature-regulated aluminum heating block. Mixing was accomplished using a magnetic stir bar. The heating block was enclosed in a nitrogen purge box. The serum bottle was charged with WN-6 (commercially available from SigmaAldrich) aluminum oxide 0.5 g, and cis-2-pentenenitrile (4.5 grams) inside a glove-box and then transferred to the heating block at the beginning of the experiment. The temperature of the heating block was maintained at 50 C. Samples were then removed after 2 hours for analysis by gas chromatography.

Example 17

(29) Example 16 was replicated except that sodium-modified aluminum oxide was used as the catalyst.

(30) Preparation of Sodium Modified Alumina:

(31) A ceramic mortar and pestle was used to prepare a sodium-modified aluminum oxide catalyst material that contained 1 percent by weight (wt %) sodium based on the combined weight percent of the precursor aluminum oxide and sodium hydroxide. The material was then dried under vacuum at minus 25 inches of mercury at 300 C. for 18 hours, and then allowed to cool under nitrogen prior to evaluation.

Example 18

(32) Example 17 was replicated except that the alumina was modified with 1 wt % KOH.

Example 19

(33) Example 17 was replicated except that the alumina was modified with 1 wt % Ca(OH).sub.2.

(34) The results are presented in Table 3 below.

(35) TABLE-US-00003 TABLE 3 Alkali/ C2PN 3PNs Alkaline Alkali/ conversion selectivity PN Example (wt %) Alkaline (%) (%) balance.sup.1 16 0 None 14.3 76.8 100 17 1 Na 33 16.5 76 18 1 K 20.3 63.8 97 19 1 Ca 14 73.7 99 .sup.1Sum of pentenenitriles in the product divided by the sum of the pentenenitriles in the feed times 100.

(36) The data presented in Table 3 show the effect of varying the alkali content of aluminum oxide catalysts used for isomerization of cis-2-pentenenitrile to 3-pentenenitrile. The data show that the pentenenitrile (PN) balance, a measure of the amount of pentenenitriles in the feed versus the amount of pentenenitriles in the product, is adversely affected. Likewise, it can be seen from the data in Table 3 that the selectivity of the reaction to 3-pentenenitriles is decreased by adding alkali, or alkaline earth metals to the aluminium oxide catalyst used.

Example 20

(37) Example 5 was repeated except that Catalox SCFa-140 aluminum oxide (commercially available from Sasol), which was contaminated with 1741 ppm iron was used as the catalyst. The amount of C10-dinitriles formed was approximately 2 orders of magnitude greater than when no iron was present in the aluminum oxide sample.

(38) Comparison of the data from Example 20 to that of Example 5 show that when iron is present on the aluminum oxide catalyst the formation of by-products formed by dimerization of 2-PN (i.e. C10-dinitriles) increases.