Method for producing acrolein

Abstract

The present invention relates to a process for preparing acrolein from propylene by catalytic gas phase oxidation with molecular oxygen (for example air). The invention further relates to the use of particular propylene-containing starting materials, for example refinery grade propylene, for preparation of acrolein.

Claims

1. A process for preparing acrolein by catalytic gas phase oxidation, the process comprising: a) providing a reaction gas comprising propylene and molecular oxygen, and b) contacting the reaction gas with an oxidation catalyst to form a gas mixture comprising acrolein, wherein the oxidation catalyst is a mixed oxide catalyst comprising at least one base component selected from the group consisting of molybdenum, vanadium, and tungsten, wherein the reaction gas is passed through a reactor tube or a plurality of reactor tubes in a bundle at a temperature of from 350° C. to 450° C., wherein the reaction gas comprises from 250 ppm to 5000 ppm by weight of sulphur in the form of a sulphur component and not more than 5000 ppm by weight of at last one unsaturated hydrocarbon selected from the group consisting of C.sub.2H.sub.4, C.sub.3H.sub.4, C.sub.4H.sub.8, C.sub.4H.sub.6, C.sub.5H.sub.10, and C.sub.5H.sub.8, wherein the reaction gas is passed through a reactor tube or a plurality of bundled reactor tubes in parallel, and the reactor tube or the plurality of bundled reactor tubes are filled with the oxidation catalyst to a length of at least 2 meters.

2. The process according to claim 1, wherein the reaction gas comprises more than 50 ppm by weight of the at least one unsaturated hydrocarbon selected from the group consisting of C.sub.2H.sub.4, C.sub.3H.sub.4, C.sub.4H.sub.8, C.sub.4H.sub.6, C.sub.5H.sub.10, and C.sub.5H8.

3. The process according to claim 1, wherein the reaction gas comprises from more than 250 ppm by weight to 1000 ppm by weight of sulphur in the form of a sulphur component.

4. The process according to claim 1, wherein the reaction gas comprises from more than 250 ppm to 1000 ppm by weight of sulphur in the form of H.sub.2S and/or SO.sub.2.

5. The process according to claim 1, wherein the reaction gas comprises from more than 100 ppm to 1500 ppm by weight of the at least one unsaturated hydrocarbon selected from the group consisting of C.sub.2H.sub.4, C.sub.3H.sub.4, C.sub.4H.sub.8, C.sub.4H.sub.6, C.sub.5H.sub.10, and C.sub.5H8.

6. The process according to claim 1, wherein the reaction gas comprises from more than 150 ppm to 1300 ppm by weight of the at least one unsaturated hydrocarbon selected from the group consisting of C.sub.2H.sub.4, C.sub.3H.sub.4, C.sub.4H.sub.8, C.sub.4H.sub.6, C.sub.5H.sub.10, and C.sub.5H8.

7. The process according to claim 1, wherein the mixed oxide catalyst further comprises at least one additional component selected from the group consisting of bismuth, antimony, tellurium, tin, iron, cobalt, nickel and copper.

8. The process according to claim 7, wherein the oxidation catalyst is a mixed oxide catalyst of the formula (I) or a mixture of various mixed oxide catalysts of the formula (I):
(Mo.sub.12Bi.sub.aC.sub.b(Co+Ni).sub.cD.sub.dE.sub.eF.sub.fG.sub.gH.sub.h)O.sub.x  (I), C=iron, D=at least one of the elements from W, P, E=at least one of the elements from Li, K, Na, Rb, Cs, Mg, Ca, Ba, Sr, F=at least one of the elements from Ce, Mn, Cr, V, G=at least one of the elements from Nb, Se, Te, Sm, Gd, La, Y, Pd, Pt, Ru, Ag, Au, H=at least one of the elements from Si, Al, Ti, Zr, a=0 to 5.0, b=0.5 to 5.0, c=2 to 15, d=0.01 to 5.0, e=0.001 to 2, f=0.001 to 5, g=0 to 1.5, h=0 to 800, and x=number which is determined by the valency and frequency of elements other than oxygen.

9. The process according to claim 1, wherein the reaction gas is produced by mixing at least refinery grade propylene and air, wherein the refinery grade propylene comprises from 0.05 to 2.0% by weight of ethane and/or from 9 to 40% by weight of propane.

10. The process according to claim 1, wherein the reaction gas is passed through a reactor tube or a plurality of reactor tubes in a bundle at a temperature of from 370° C. to 430° C.

11. The process according to claim 1, wherein the reactor tubes are charged with oxidation catalyst to the length of at least 3 meters.

12. The process according to claim 1, wherein the length the reactor tubes are charged with oxidation catalyst to the length of 1.5 to 5 meters.

13. The process according to claim 1, wherein the length the reactor tubes are charged with oxidation catalyst to the length of 2.0 to 4.5 meters.

14. The process according to claim 1, wherein the length the reactor tubes are charged with oxidation catalyst to the length of 2.5 to 4.0 meters.

15. The process according to claim 1, wherein the internal diameter of each reactor tube is from 1.0 to 3.5 cm.

16. The process according to claim 1, wherein the internal diameter of each reactor tube is from 1.5 to 3.3 cm.

17. The process according to claim 1, wherein the internal diameter of each reactor tube is from 2.0 to 3.0 cm.

Description

EXAMPLES

Example 1

(1) In a tubular reactor with 20 ml of catalyst bed, the heterogeneously catalysed partial oxidation of propylene was performed in the presence of molecular oxygen over a mixed metal oxide catalyst, the preparation method for which can be found in DE 10 2006 015710 A1 (Example 1). As well as propylene and air, nitrogen (and optionally steam) was fed in as additional inert gas. The reactor was heated to about 360° C. by means of an electrical oven. The temperature in the catalyst bed was monitored by means of thermocouples, and the maximum temperature was about 400° C. The analysis of the process gas was performed by means of gas chromatography.

(2) The reaction was first started up under standard conditions (=feed gas consisting of propylene, oxygen and inert gas, e.g. nitrogen). In order to study the influence of sulphur components, a mixture of sulphur component in inert gas (e.g. H.sub.2S in nitrogen) was metered in by means of an additional mass flow meter and replaces the inert gas of the standard conditions in a parallel stepwise manner, such that the total volume flow rate was kept constant. Results are given hereinafter according to various catalyst run times and the respective proportion by mass of sulphur component (based on the overall gas stream):

(3) TABLE-US-00001 TABLE 1 Catalyst performance after various run times with and without metered addition of H.sub.2S. Proportion Proportion by mass of by mass of sulphur H.sub.2S Run H.sub.2S [34 g/mol] [32 g/mol] metering Propylene Acrolein time [ppm by [ppm by time conversion yield [h] wt.] wt.] [h] [%] [%] 50 0 0 — 90.1 80.0 135 0 0 — 90.6 80.0 315 220 207 150 91.6 80.1 550 435 409 337 89.9 80.0 810 870 819 260 90.0 80.6 1080 1500 1412 103 91.3 80.9

Example 2

(4) A bed of 2850 mm of catalyst was introduced into a tubular reactor of length 3400 mm with internal diameter of 21.7 mm. The reactor is surrounded by a heat carrier medium and thus kept at a constant temperature of 350° C. The reactor was charged with a reaction gas composed of propylene (9.3% by weight), air (58.3% by weight), remainder inert gas. Via a separate control path, SO.sub.2 (as a pure substance and/or as a mixture with inert gas) was first metered in. The catalyst was run in and the metered addition of the sulphur component was commenced only after several days of steady-state operation. The proportion by mass was then increased gradually.

(5) TABLE-US-00002 TABLE 2 Catalyst performance after various run times without and with metered addition of SO.sub.2 or H.sub.2S. Proportion Proportion by by mass of SO.sub.2 Run mass of SO.sub.2 Sulphur metering Propylene Acrolein time [64 g/mol] [32 g/mol] time conversion yield [h] [ppm by wt.] [ppm by wt.] [h] [%] [%] 50 0 0 — 97.6 85.6 150 0 0 — 97.5 85.6 350 0 0 — 97.6 85.4 660 250 125 288 97.4 85.2 1000 1000 500 72 98.3 85.9 1200 2000 1000 120 98.7 85.9 1440 5000 2500 72 97.2 85.3 1670 10 000 5000 120 97.5 79.8 Regeneration Proportion SO.sub.2 Run Proportion by by mass of metering Propylene Acrolein time mass of SO.sub.2 Sulphur time conversion yield [h] [ppm by wt.] [ppm by wt.] [h] [%] [%] 1800 500 250 72 97.5 85.2 1950 1000 500 72 97.6 84.7

(6) The results (conversion, yield) up to a catalyst run time of 350 h, in which no sulphur component was metered in, show the performance of the catalyst without involvement of sulphur components.

(7) The run times reported in Tables 1 and 2 are gross run times. The period of H.sub.2S or SO.sub.2 metering with a particular proportion by mass of H.sub.2S or SO.sub.2 reported in each case took place within the period between the run times of H.sub.2S or SO.sub.2 metering with the next highest or next lowest proportion by mass of H.sub.2S or SO.sub.2.

(8) Example: The period of SO.sub.2 metering of 288 h at a proportion by mass of SO.sub.2 of 250 ppm by weight was within the interval between run time 350 and 1000 h.

(9) For the rest of the interval, reaction gas was passed through the tubular reactor without SO.sub.2 metering.