Selective preparation of tetrahydrofuran by hydrogenation of maleic anhydride

Abstract

A catalyst for the hydrogenation of C4-dicarboxylic acids and/or derivatives thereof, preferably maleic anhydride, in the gas phase comprises a) 20-94% by weight of copper oxide (CuO), preferably 40-92% by weight of CuO, in particular 60-90% by weight of CuO, andb) 0.005-5% by weight, preferably 0.01-3% by weight, in particular 0.05-2% by weight, palladium and/or a palladium compound (calculated as metallic palladium) andc) 2-79.995% by weight, preferably 5-59.99% by weight, in particular 8-39.95% by weight, of an oxidic support selected from the group consisting of the oxides of Al, Si, Zn, La, Ce, the elements of groups IIIA to VIIIA and of groups IA and IIA of the Periodic Table of the Elements.

Description

COMPARATIVE EXAMPLE C1

Production of CuO/Al₂O₃ Catalyst Pellets

3 l of water are placed in a heatable precipitation vessel fitted with a stirrer and are heated to 80° C. A metal salt solution consisting of 1754 g of Cu(NO₃)₂*2.5H₂O and 2944 g of Al(NO₃)₃*9H₂O in 4000 ml of water are metered simultaneously with a 20% strength by weight solution of sodium carbonate into this precipitation vessel over a period of one hour while stirring. The amount of sodium carbonate metered in is selected so that a pH of 6 is established in the precipitation vessel. After all the metal salt solution has been added, further sodium carbonate solution is metered in until the pH in the precipitation vessel has reached 8, and the mixture is stirred at this pH for another 15 minutes. The total consumption of sodium carbonate solution is 11 kg. The suspension formed is filtered and the solid is washed with water until the washings no longer contain nitrates (<25 ppm). The filter cake is firstly dried at 120° C. and subsequently calcined at 600° C.

600 g of this material are intimately mixed with 18 g of graphite and tabletted to produce pellets having a diameter of 3 mm and a height of 3 mm.

EXAMPLE 2

Production of a CuO/Pdb/Al₂O₃ Catalyst According to the Present Invention

550 g of the pellets from Example 1, which had a water uptake capacity of 0.33 cm³/g, were uniformly sprayed in an impregnation drum with a solution of 2.76 g of Pd as palladium nitrate in 172 ml of water, dried at 100° C. and finally calcined at 350° C. for 2 hours.

COMPARATIVE EXAMPLE C3

Production of a CuO/PtO/Al₂O₃ Catalyst for Comparison:

550 g of the pellets from Example 1, which had a water uptake capacity of 0.33 cm³/g, were uniformly sprayed in an impregnation drum with a solution of 2.76 g of Pt as platinum nitrate in 172 ml of water* dried at 100° C. and finally calcined at 350° C. for 2 hours.

COMPARATIVE EXAMPLE C4, EXAMPLE 5, COMPARATIVE EXAMPLE C6

Hydrogenation of Maleic Anhydride

100 ml of the catalyst pellets from Comparative Example C1 or Example 2 were in each case mixed with 100 ml of glass rings of the same size and placed in a tube reactor having an internal diameter of 27 mm. The temperature of the reactor was regulated by means of oil flowing around it, and the reaction gas was passed through the reactor from the top downwards. MA was pumped as a melt into a vaporizer operated at 200° C. where it was vaporized in a stream of water The MA/hydrogen mixture, which had an MA concentration of 1.2% by volume, was then passed through the reactor and preheated above the catalyst bed. Complete conversion of MA was obtained in all examples.

Before the MA/hydrogen mixture was fed into the reactor, the catalyst was subjected to a pretreatment with hydrogen. For this purpose, 200 standard 1/h of nitrogen were firstly passed through the reactor under atmospheric pressure and the reactor was simultaneously heated to a temperature in the catalyst bed of 180° C. over a period of one hour. The nitrogen flow was then increased to 950 standard 1/h and an additional 50 standard 1/h of hydrogen was fed in. A slight temperature increase in the catalyst bed to about 250° C. at the hot spot was observed. The hot spot migrates through the reactor from the reactor inlet to the end of the reactor. After the temperature had dropped to 190° C. throughout the catalyst bed, the nitrogen flow was reduced to 900 standard 1/h and the water flow was increased to 100 standard 1/h. The nitrogen flow was gradually switched off and the hydrogen flow was gradually increased to 250 standard 1/h.

To compare the activity of the catalysts, the GHSV was increased from 2500 to 6000 h⁻¹.

								Space-
								time
						STHF	Sothers	yield
Ex.	Cat.	T	GHSV	SBA	SGBL	[mol	[mol	[gTHF/
No.	No.	[° C.]	[l/h]	[mol %]	[mol %]	%]	%]	hlcat.]
C4	C1	250	2500	0	0	93	7	89
		250	3000	<1	13	83	7	95
		250	6000	30	62	7	1	16
5	2	250	2500	0	0	89	11	85
		250	3000	0	0	91	9	104
		250	6000	0	0	93	7	212
C6	C3	250	2500	0	2	76	22	73
		250	3000	10	71	15	4	17
		250	6000	32	59	7	2	16
Sxxx = selectivity to the respective product

As can be seen from the table, in the case of the Pd-free catalyst of Comparative Example 1, the maximum space-time yield of tetrahydrofuran is achieved at a GHSV of 3000 h⁻¹. The THF selectivity of 93% is achieved by the catalyst at a space-time yield of 89 g_THF/h1_catalyst.

In comparison thereto, the catalyst according to the invention from Example 2 achieves an increase in the space-time yield to 212 g _THF/h*1_catalyst at the same tetrahydrofuran selectivity of 93%. The platinum-doped catalyst from Comparative Example 3, on the other hand displays a poorer activity and selectivity to tetrahydrofuran compared to the undoped system.

Claims

1-4. (canceled)

5. A process for the hydrogenation of C4-dicarboxylic acids and/or derivatives thereof, in the gas phase in the presence of a catalyst, wherein said catalyst comprises 40-92% by weight of copper oxide 0.005-5% by) weight of palladium and/or of a material having acid sites, which support material is selected from the group consisting of: oxides of Al, Si, Zn, La, Ce, elements of groups IIIA to VIIIA and elements of groups IA and IIA.

6. A process as claimed in claim 5, wherein the GHSV is from 10 to 50 000 h−1.

7. A process as claimed in claim, wherein the reaction temperature is from 150 to 400° C., and the pressure during the reaction is from 0.5 to 50 bar.

8. A process as claimed in claim 5, wherein the concentration of C4-dicarboxylic acid or the derivative thereof is from 0.5 to 5% by volume.

9. (canceled)

10. The process for the hydrogenation of C4-dicarboxylic acids and/or derivatives thereof as claimed in claim 5 for the hydrogenation of maleic anhydride.

11. The process of claim 5, wherein the catalyst comprises palladium oxide and/or palladium nitrate.

12. The process of claim 5, wherein the support material is selected from the group consisting of aluminum oxide, silicon oxide, titanium oxide, zinc oxide, zirconium oxide and cerium oxide.

13. The process of claim 5, wherein the catalyst consists of copper oxide, palladium and/or a palladium compound and aluminum oxide.

14. The process of claim 5, wherein the GHSV is from 100 to 10 000 h−1.

15. The process of claim 7, wherein the reaction temperature is from 200 to 300° C.

16. The process of claim 7, wherein the pressure during the reaction is from 1 to 20 bar.

17. The process of claim 8, wherein the concentration of C4-di-carboxylic acid or the derivative thereof is from 0.2 to 2% by volume.