Method for simultaneously eliminating isobutanal and ethanol from olefinic feedstocks by adsorption on a porous refractory oxide-based material

Abstract

This invention pertains to a method for purifying an olefinic feedstock that comprises olefins with 4 carbon atoms and impurities including isobutanal, ethanol, and acetone, where said method comprises a pretreatment that comprises a step for eliminating acetone and optionally a step for eliminating the water that is present in said olefinic feedstock, and a step for simultaneously eliminating isobutanal and ethanol by running the feedstock obtained from the pretreatment over at least one fixed bed having at least one adsorbent that comprises at least one porous refractory oxide-based material, optionally impregnated with one or more alkaline or alkaline-earth cations; where said step for simultaneously eliminating isobutanal and ethanol operates at a temperature of between 0 and 200 C., at a pressure of 0.1 to 10 MPa, and with an hourly volumetric flow rate (VVH) of the feedstock on the fixed bed of between 0.1 and 10 h.sup.1.

Claims

1. A method for purifying an olefinic feedstock that comprises olefins with 4 carbon atoms and impurities including isobutanal, ethanol, and acetone, wherein said method comprises: a) pretreatment that comprises at least one acetone elimination; and b) simultaneously eliminating isobutanal and ethanol by running the pretreated feedstock obtained from a) over at least one fixed bed with at least one adsorbent that comprises at least one porous refractory oxide-based material, wherein b) operates at a temperature of between 0 and 200 C., at a pressure of 0.1 to 10 MPa, and with an hourly volumetric flow rate (VVH) of the pretreated feedstock obtained from a) over the fixed bed of between 0.1 and 10 h.sup.1.

2. The method in accordance with claim 1, wherein said olefinic feedstock is produced from the dehydration of isobutanol or a mixture of butanol isomers that comprises isobutanol.

3. The method in accordance with claim 1, wherein the pretreatment also comprises eliminating water that is present in said olefinic feedstock, wherein acetone-elimination and water-elimination are carried out simultaneously or successively.

4. The method in accordance with claim 1, wherein the porous refractory oxide-based material is: alumina, silica, titanium oxide, zirconium oxide, magnesium oxide, or mixtures thereof.

5. The method in accordance with claim 1, wherein the porous refractory oxide-based material is based on alumina.

6. The method in accordance with claim 1, wherein the porous refractory oxide-based material has a macropore volume, defined as a cumulative volume of the pores that are greater than 50 nm in diameter, as measured by mercury intrusion, of greater than or equal to 0.01 ml/g, a total pore volume, as measured by mercury intrusion according to the Standard ASTM D4284 with a wetting angle of 140, greater than or equal to 0.05 ml/g, and a specific surface area, expressed in terms of S.sub.BET and measured by the B.E.T. method in accordance with the Standard ASTM D3663, between 30 m.sup.2/g and 400 m.sup.2/g.

7. The method in accordance with claim 1, wherein the porous refractory oxide-based material is impregnated with one or more alkaline or alkaline-earth cations.

8. The method in accordance with claim 7, wherein the cation is a cation of sodium, potassium, magnesium, or calcium.

9. The method in accordance with claim 7, wherein the porous refractory oxide-based material is impregnated with one or more alkaline or alkaline-earth cations at a level from 0.2 to 40% by weight, relative to the total weight of the adsorbent after impregnation.

10. The method in accordance with claim 1, wherein b) operates at a temperature between 20 and 60 C.

11. The method in accordance with claim 1, wherein b) operates at a pressure between 0.3 and 5 MPa.

12. The method in accordance with claim 1, wherein b) is carried out such that the hourly volumetric flow rate (VVH) of said feedstock on said fixed bed is between 0.2 and 5 h.sup.1.

13. The method in accordance with claim 1, wherein b) is carried out in a reactor that comprises multiple fixed beds that are arranged in parallel and that can be shuffled.

14. A method for transforming olefins, comprising purification of the olefinic feedstock in accordance with claim 1 upstream from a metathesis method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 presents the breakthrough curves of ethanol and isobutanal that were obtained during the co-adsorption test on the adsorbent prepared in Example A and under the conditions of Test 2 of Table 1.

(2) Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

(3) In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

(4) The entire disclosures of all applications, patents and publications, cited herein and of corresponding French application No. 17/62.091, filed Dec. 13, 2017, are incorporated by reference herein.

EXAMPLES

(5) In Examples B and D below, the olefinic feedstock was first stripped with nitrogen and then run over a sieve 3A. At the end of this pretreatment, the water and acetone contents of the feedstock are verified by, respectively, the method of Karl Fischer and gas-phase chromatography according to the UOP 960 method. The olefinic feedstock that is tested in Examples B and D no longer contains either water or acetone.

(6) In Example C below, the olefinic feedstock was first run over a sieve 3A. An analysis by the method of Karl Fischer shows that, at the end of this pretreatment, the olefinic feedstock that is tested in Example C no longer contains water.

Example A. Preparation of an Adsorbent According to the Invention

(7) The adsorbent is prepared by dry impregnation of a material such as flash alumina, which is shaped by granulation, using a solution of NaOH.

(8) The alumina selected has a pore volume of 0.5 ml/g, a macropore volume of 0.1 ml/g, a specific surface area of 341 m.sup.2/g, and a sodium content before impregnation of 1,948 ppm by mass.

(9) The specific surface area is determined by the B.E.T. method according to the Standard ASTM D3663. The total pore volume and the macropore volume are determined by application of the Standard ASTM D4284 by mercury intrusion measurement with a wetting angle of 140, using a device such as the Autopore III model of the Micromritics brand. The sodium content is measured by atomic absorption spectroscopy.

(10) Impregnation is done as follows:

(11) a) Preparation of 50 mL of a soda (NaOH) solution by dissolving 8.84 g of NaOH in 50 g of water;

(12) b) Streaming, drop by drop using a burette, of 5 mL of the soda solution prepared according to Step a), onto 10 g of flash alumina that has been placed in advance in a rotating receptacle (impregnation phase);

(13) c) Curing of the impregnated material in a closed water-saturated container at 20 C. for 3 hours;

(14) d) Drying of the solid under dry air at 90 C. for 3 hours in an oven;

(15) e) Calcining of the solid under dry air at 350 C. for 1 hour.

(16) After impregnation, the sodium content as measured by atomic absorption spectroscopy is 4.1% by weight relative to the total weight of the adsorbent.

(17) The adsorbent A that is prepared is white in color.

Example B. Co-Adsorption of Isobutanal and Ethanol and Production of Purified Butenes

(18) The adsorbent A, prepared in accordance with Example A, is tested in a fixed-bed reactor at 30 C. under 0.8 MPa. The feedstock is composed of 80% n-butene and 20% isobutene and comprises isobutanal and ethanol in variable proportions (see Table 1, Tests 1 to 3).

(19) In parallel, an adsorbent of the NaY zeolite type from Zeolyst, white, shaped by pelletizing and crushing, is tested under the same conditions. The feedstock is composed of 80% n-butene and 20% isobutene and comprises isobutanal and ethanol at levels of 3,023 and 963 ppm by mass, respectively.

(20) The fixed bed of adsorbent is first activated at 290 C. under N.sub.2 for 12 hours and is then filled with butane at 30 C. under 0.8 MPa. The feedstock is then injected into the reactor at a flow rate of 0.5 ml/min continuously, i.e., an hourly volumetric flow rate of 0.5 h.sup.1.

(21) The tracking of the concentrations of isobutanal and ethanol at the reactor outlet is done by means of gas-phase chromatography analysis on a microGC 4900 from Varian.

(22) The test is halted when the concentrations of isobutanal and ethanol impurities in the discharge effluent are the same as those in the entry feedstock.

(23) At the end of the test, the adsorbent A and the NaY zeolite are white in color.

(24) The capture capacities of the adsorbents at saturation with regard to isobutanal and ethanol are calculated by means of a material balance between what enters the column and what leaves it. These capture capacities, expressed in g of the impurity in question (isobutanal or ethanol) for 100 g of adsorbent, are recorded in Table 1, along with the feedstock concentrations of isobutanal and ethanol, expressed in ppm by mass and their molar ratio.

(25) TABLE-US-00001 TABLE 1 Quantities of Isobutanal and Ethanol in the Feedstock and Quantities Adsorbed by Adsorbent A (Sodium-Doped Alumina) and by the NaY Zeolite [Isobutanal] [Ethanol] Molar Ratio of q.sub.ads.sub..sub.isobutanal q.sub.ads.sub..sub.ethanol Adsorbent Test (ppm by Mass) (ppm by Mass) Isobutanal/Ethanol (g/100 g) (g/100 g) A 1 1796 330 3.5 6.4 2.2 (According 2 644 410 1 4.3 3.4 to the 3 9 30 0.2 2.9 5.2 Invention) NaY 4 13,023 963 2 1.4 18.4 (Comparitive Test)

(26) The adsorbent A has significant capture capacities for isobutanal and ethanol, and these capacities are of the same order of magnitude regardless of the concentrations and proportions of isobutanal and ethanol in the feedstock. Even in the case of a feedstock with an excess of ethanol relative to isobutanal (isobutanal/ethanol molar ratio at 0.2), the capture capacity of adsorbent A for isobutanal remains high (2.9 g for 100 g of adsorbent).

(27) By contrast, the NaY zeolite exhibits a low capture capacity for isobutanal (1.4 g for 100 g of adsorbent) when the feedstock contains ethanol, even with an excess of isobutanal (2 more isobutanal than ethanol). This adsorbent is thus not suitable for ensuring eliminating isobutanal and ethanol jointly.

(28) The breakthrough curves of ethanol and isobutanal on the adsorbent as prepared in Example A, which were obtained during the ethanol/isobutanal co-adsorption test at molar iso-concentration in the feedstock (Test 2 of Table 1), are depicted in FIG. 1.

(29) As shown in FIG. 1, it appears that the method according to the invention, which is carried out on a bed of adsorbent A (sodium-impregnated alumina) and at 30 C., makes it possible to obtain isobutanal and ethanol contents in the output effluent that are less than 1 ppm by mass. As a matter of fact, the concentrations of isobutanal and ethanol in the reactor output effluent are below the detection limit of 1 ppm by mass for 75 and 105 minutes, respectively, for isobutanal and ethanol.

Example C. Co-Adsorption of Isobutanal, Ethanol, and Acetone and Production of Purified ButenesComparative Example

(30) A test similar to that of Example B is carried out with a feedstock that is composed of 80% n-butene and 20% isobutene and that comprises a mixture of isobutanal (642 ppm by mass), ethanol (413 ppm by mass), and acetone (519 ppm by mass).

(31) After the test, the adsorbent A is removed. It is orange in color.

(32) The comparison of the appearances of the adsorbent A after the tests, between Example B (feedstock comprising isobutanal and ethanol) and Example C (feedstock comprising isobutanal, ethanol, and acetone), shows that the presence of acetone in the feedstock has caused degradation thereof during the course of the test. A feedstock that contains acetone thus has to be pretreated in order to eliminate at least the acetone, before the step of joint elimination of isobutanal and ethanol on an adsorbent according to the invention is carried out.

Example D. Regenerability of the Adsorbent and Cycling

(33) The adsorbent A, as prepared according to Example A, is tested on a fixed bed in a column at 30 C. under 0.8 MPa. The feedstock is composed of 80% n-butene and 20% isobutene and comprises 644 ppm by mass of isobutanal and 410 ppm by mass of ethanol. The operating conditions tracked are those described in Example B.

(34) The isobutanal and ethanol concentrations in the output effluent are tracked by gas-phase chromatographic analysis on a microGC 4900 from Varian.

(35) When the output composition becomes identical to the input composition, the adsorbent is considered saturated. The flow of the feedstock is halted, and the adsorbent is regenerated under a stream of nitrogen at atmospheric pressure at 290 C. at 20 NL/h. When the concentrations of isobutanal and ethanol at the output of the column become zero, regeneration is considered completed. The stream of nitrogen is replaced by a flow of feedstock identical to that of the first cycle, so as to initiate a second adsorption cycle. The concentrations of isobutanal and ethanol at the reactor output are tracked as above by gas-phase chromatographic analysis on a microGC 4900. When the output composition becomes identical to the input composition, the column is again subjected to a stream of nitrogen at atmospheric pressure at 290 C. Four cycles of adsorption/regeneration are strung together. The capture capacities for isobutanal and ethanol are recorded in Table 2.

(36) TABLE-US-00002 TABLE 2 Quantities of Isobutanal and Ethanol Adsorbed by Adsorbent A after Each Adsorption/Desorption Cycle Cycle q.sub.ads.sub..sub.isobutanal (g/100 g) q.sub.ads.sub..sub.ethanol (g/100 g) 1 4.3 3.4 2 3.5 3.0 3 2.5 2.4 4 1.8 2.2 5 1.6 2.1

(37) The capture capacities for isobutanal and ethanol remain satisfactory after 5 cycles. The adsorbent A is thus always able to eliminate isobutanal and ethanol jointly after 5 cycles.

(38) The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

(39) From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.