PROCESS FOR REMOVING METHOXYETHANOL FROM A MIXTURE COMPRISING METHOXYETHANOL AND MORPHOLINE

Abstract

A method for removing methoxyethanol from a mixture comprising methoxyethanol and morpholine makes use of the selective adsorption of methoxyethanol onto a mixed oxide comprising a spinel phase. The mixed oxide comprises 20 to 30% by weight MgO and 80 to 70% by weight Al.sub.2O.sub.3. The spinel phase has the formula MgAl.sub.2O.sub.4. The mixture is a pre-purified reaction output of the reaction of diethylene glycol with ammonia in the presence of an amination catalyst.

Claims

1. A method for removing methoxyethanol from a mixture comprising methoxyethanol and morpholine by selective adsorption of methoxyethanol onto a mixed oxide comprising a spinel phase.

2. The method according to claim 1, wherein the spinel phase has the formula
AB.sub.2O.sub.4 in which A is a divalent cation; and B is a trivalent or tetravalent cation.

3. The method according to claim 2, wherein the spinel phase has the formula MgAl.sub.2O.sub.4.

4. The method according to claim 3, wherein the mixed oxide comprises 20 to 30% by weight MgO and 80 to 70% by weight Al.sub.2O.sub.3.

5. The method according to claim 1, wherein the mixture is passed over a bed of the mixed oxide.

6. The method according to claim 1, wherein the mixture comprises in addition at least one component selected from 1,2-ethylenediamine, methoxyethylmorpholine and formylmorpholine.

7. The method according to claim 1, wherein the mixture is dried prior to the selective adsorption.

8. The method according to claim 7, wherein the mixture is dried by bringing it into contact with a molecular sieve.

9. The method according to claim 1, wherein the mixed oxide is regenerated by treatment with water.

10. The method according to claim 9, wherein coadsorbed morpholine is desorbed prior to the regeneration of the mixed oxide.

11. The method according to claim 10, wherein coadsorbed morpholine is desorbed by passing over an inert gas or an inert gas containing steam.

12. The method according to claim 11, wherein the desorbed coadsorbed morpholine is condensed out from the inert gas or inert gas containing steam.

13. The method according to claim 2, wherein A is Mg, Fe, Co, Ni, Mn, Zn or Cd; and B is Al, Fe, Co, Cr, Ga, La or Ti.

14. The method according to claim 3, wherein the mixed oxide comprises 25 to 27.5% by weight MgO and 75 to 82.5% by weight Al.sub.2O.sub.3.

Description

[0034] The invention is more particularly elucidated by the appended figure and the examples which follow.

[0035] FIG. 1 shows the X-ray powder diffractogram of the mixed oxide according to example 2.

EXAMPLES

[0036] The XRD analyses were carried out using a D8 Advance Series 2 from Bruker/AXS using a CuK-alpha source (having a wavelength of 0.154 nm at 40 kV and 40 mA). The measurements were carried out over the measuring range: 10-80 (2Theta), 0.02 steps at 2.4 seconds/step. To determine the average crystallite sizes of the individual phase, the TOPAS (Bruker AXS) structure analysis software was used.

Example 1: Preparation of a Spinel-Containing Mixed Oxide Consisting of 25% MgO and 75% Al.SUB.2.O.SUB.3

[0037] An aqueous solution (1.95 L), comprising 628.23 g of magnesium nitrate and 1889.2 g of aluminum nitrate, was simultaneously precipitated with a 20 percent aqueous sodium carbonate solution at 80 C. in a stirred vessel in a constant stream such that the measured pH was maintained at 5.5. The pH was then adjusted to pH 7.8 with a sodium carbonate solution and the reaction solution was further stirred for circa 30 minutes. The resulting suspension was filtered and washed with water until the conductivity of the filtrate was about 50 S and then dried at 100 C. for 16 hours. The powder was milled to a particle size of below 500 m. An extrudate in the form of 1.5 mm length strands was produced from the powder at a pressure of 80 bar with 70 mL of water and at a kneading time of 70 min. The resulting extrudate was dried at 120 C. for 16 hours and subsequently calcined at 600 C. for 1 hour at a heating rate of 2 C./min.

Example 2

[0038] The spinel was produced as in example 1 but a different ratio of magnesium nitrate and aluminum nitrate solutions was used. Thus, a spinel was obtained having the composition of 27.5% MgO and 72.5% Al.sub.2O.sub.3.

Example 3

[0039] Adsorption of Methoxyethanol (MeOEtOH) Onto the Spinel from Example 1

[0040] A laboratory column was packed with a molecular sieve (100 mL) and the spinel (80 mL), in which the molecular sieve was packed prior to the spinel. Subsequently, the molecular sieve and the adsorbent were dried in two steps, where nitrogen was initially passed through (20 NL/h) at 100 C. for 20 hours and then at 150 C. for 6 hours. Morpholine comprising about 0.1% by weight methoxyethanol was passed through the dry adsorbent material. The adsorption was carried out at room temperature at a flow rate of 10 g/h to 15 g/h. Samples were regularly analyzed by means of gas chromatography and a reduction of the methoxyethanol content by 50% was defined as breakthrough.

[0041] The results are shown in the following table.

TABLE-US-00001 Cumulative adsorbent loading Decrease of Methoxyethanol kg.sub.MeOEtOH/ methoxyethanol Sample area % t.sub.adsorbent [%] 1 0.0310 3.48 71.52 2 0.0194 8.05 82.17 3 0.0240 11.10 78.02 4 0.0433 16.43 60.23 5 0.0601 20.01 44.86 6 0.0764 24.91 29.93

[0042] The capacity of the adsorbent was about 17 kg.sub.MeOEtOh/t.sub.adsorbent.

Example 4

[0043] Adsorption of Methoxyethanol Onto the Spinel from Example 2

[0044] The adsorption experiments were performed analogously to example 3. The results are shown in the following table.

TABLE-US-00002 Cumulative adsorbent loading Decrease of Methoxyethanol kg.sub.MeOEtOH/ methoxyethanol Sample area % t.sub.adsorbent [%] 1 0.008 3.60 92.66 2 0.000 5.85 100.00 3 0.006 9.50 94.50 4 0.061 14.15 44.04 5 0.087 17.30 20.18

[0045] The capacity of the adsorbent was about 14 kg.sub.MeOEtOh/t.sub.adsorbent.

Example 5

[0046] Regeneration of the Spinel from Example 1

[0047] The spinel from example 1 was regenerated by washing with water at room temperature. For this purpose, 10 wash fractions were used, in which one wash fraction corresponds to one bed volume and the flow rate was 400 g/h. Each wash fraction was analyzed by gas chromatography and the mixed oxide was subsequently dried with nitrogen (20 NL/h; 2 d at 80 C., 2 h at 100 C., 2 h at 120 C., 6 h at 150 C.).

[0048] The results of the gas chromatography (area%) are shown in the following table. In this case, it was clear that the wash water still comprised considerable amounts of morpholine.

TABLE-US-00003 Morpholine content Fraction area % 1 30.48 2 7.46 3 0.49 4 0.07 5 0.02 6 0.02 7 0.02 8 0.01 9 0.01 10 0.01

Example 6

[0049] Regeneration of the Spinel from Example 2

[0050] The spinel was regenerated by a different process.

[0051] In the first regeneration, the column was heated to 50 C. to 80 C. and dry nitrogen was passed through. Subsequently, the charged nitrogen was passed over a cool condensor at 5 C., whereupon morpholine separated out. The adsorbent was then washed with 5 wash fractions of water and dried with nitrogen. The morpholine which separated out and the wash fractions were analyzed by means of gas chromatography.

[0052] The second regeneration was carried out in analogy to the first, with the difference that the column was heated to 50 C. to 150 C. The morpholine separated out on the condensor and the wash fractions were analyzed by means of gas chromatography. Morpholine loss was estimated from the data.

[0053] In the case of the third regeneration, the column was heated to 50 C. to 100 C. and, after passing through the dry nitrogen, was treated with nitrogen that had been moistened by means of a water bottle which comprised water at room temperature. The subsequent regeneration was carried out in analogy to the second regeneration, in which the morpholine separated off and the wash fractions were analyzed by means of gas chromatography.

[0054] The fourth regeneration was carried out in analogy to the third, with the difference that the nitrogen had been moistened with warm water at 90 C.

TABLE-US-00004 Morpholine loss Regeneration % 1 0.34 2 0.18 3 0.21 4 0.11