Method for producing N-methyl-p-toluidine for use as an additive for aviation gasoline

Abstract

The invention relates to novel methods for preparing N-methyl-p-toluidine for the use thereof as additive for aviation fuel, and to specific catalysts for these methods.

Claims

1. A method for preparing N-methyl-p-toluidine, comprising: reacting p-toluidine with methanol in the presence of at least one catalyst, wherein the at least one catalyst comprises, in the following proportions, Cu: 45.5-68.0% by weight, Zn: 12.3-22.5% by weight, Al: 1.9-4.1% by weight, and 7.8-28.2% by weight of oxygen, wherein Cu, Zn, Al and oxygen comprise at least 99% by weight, of the total amount of the catalyst.

2. The method according to claim 1, wherein the catalyst is pretreated by supplying hydrogen at temperatures of at least 150 C.

3. The method according to claim 2, wherein the pretreatment of the catalyst with hydrogen can take place prior to introduction into the reactor or in the reactor itself.

4. The method according to claim 1, wherein the catalyst loading is 0.1 to 1.5 kg of p-toluidine per kg of catalyst per hour.

5. The method according to claim 1, wherein the molar ratio of p-toluidine to methanol is 1:0.7 to 1:5.

6. The method according to claim 1, wherein the molar ratio of p-toluidine to hydrogen is 1:0.1 to 1:5.

7. The method according to claim 1, wherein the method is carried out at a temperature of 200 to 300 C.

8. The method according to claim 1, wherein the at least one catalyst comprises, in the following proportions, Cu: 47.0-64.1% by weight, Zn: 14.3-21.5% by weight, Al: 2.2-3.8% by weight, and 13.6-25.1% by weight, of oxygen and 0-10% by weight of carbon, wherein Cu, Zn, Al, oxygen and carbon comprise at least 99.5% by weight, of the total amount of the catalyst.

9. The method according to claim 1, wherein the at least one catalyst comprises, in the following proportions, Cu: 47.5-60.5% by weight, Zn: 15.2-19.5% by weight, Al: 2.5-3.6% by weight, and 16.2-24.5% by weight, of oxygen and 0-10% by weight of carbon, wherein Cu, Zn, Al, oxygen and carbon comprise at least 99.5% by weight, of the total amount of the catalyst.

10. The method according to claim 1, wherein the catalyst loading is 0.3 to 1 kg of p-toluidine per kg of catalyst per hour.

11. The method according to claim 1, wherein the molar ratio of p-toluidine to methanol is 1:1 to 1:3.5.

12. The method according to claim 1, wherein the molar ratio of p-toluidine to hydrogen is 1:0.5 to 1:4.

Description

EXAMPLES

Example 1

(1) Production of the catalyst according to the invention:

(2) Preparation:

(3) Charge 1:

(4) 18 773 g of copper nitrate solution with 14.6% Cu and 5522 g of zinc nitrate solution with 15.9% Zn were made up to 22 400 ml with distilled water. The pH was then adjusted to 0.5 with HNO.sub.3.

(5) Charge 2:

(6) 8959 g of sodium carbonate were dissolved in 31 038 g of water.

(7) Procedure:

(8) The contents of the precipitation vessel, consisting of 40 000 g of deionized water, were heated to 70 C. using a thermostat. Charges 1 and 2 were likewise heated to 70 C. 273.6 g of aluminium oxide were added to the precipitation vessel with stirring. The mixture of copper nitrate and zinc nitrate solution from Charge 1 was pumped continuously (190-220 ml/min) into the precipitation vessel using a diaphragm pump, while a second diaphragm pump supplied the sodium carbonate solution from Charge 2 by pumping, with the result that the pH was held at 7.9-8 during the precipitation.

(9) The suspension was subsequently concentrated on a crossflow filter and washed with deionized water to a conductivity <100 S.

(10) The suspension was filtered with suction over a porcelain suction filter. The filter cake was dried in a drying cabinet at 110 C. and pressed through a 0.8 mm sieve. The product was calcined in a rotary kiln at 450 C.

(11) 4505 g of the calcined product were processed with 225 g of graphite into 55 mm tablets on a tabletting press (Korsch XL 100).

(12) Physical Properties:

(13) Bulk density: 1746 g/l,

(14) lateral fracture hardness: 168 N,

(15) BET surface area: 65.4 m.sup.2/g, determined to ISO9277,

(16) Pore volume: 0.163 cm.sup.3/g,

(17) Loss on ignition (1 h, 900 C.): 10.7%,

(18) Specific Cu surface area: 5.8 m.sup.2/g, measured to DIN 66131-3,

(19) Average copper particle size: 54.8 nm, measured to DIN 66131-3.

(20) The composition of the catalyst gave the following values:

(21) Cu: 51.0% by weight, Zn: 16.3% by weight, Al 2.7% by weight, O: 23.8% by weight, which changed after heating to 900 C. and a hold time of 1 h as follows:

(22) Cu: 57.0% by weight, Zn: 18.3% by weight, Al: 2.9% by weight, O: 21.4% by weight

Example 2

(23) Testing of the catalyst according to the invention: 81 ml of the catalyst produced in accordance with Example 1 (screen fraction 1.6-3.15 mm) were introduced into a reaction tube having an internal diameter of 32 mm and a length of 180 mm, additionally containing an internal tube with thermocouple. The reaction tube was maintained at 275 C. using an electrical heating means, wherein the catalyst was initially pretreated with a mixture of nitrogen and hydrogen. Subsequently, a reaction mixture of 40.4 g/h of p-toluidine, 24.1 g/h of methanol and 25.4 l/h of hydrogen was metered in continuously. The reaction product was condensed and analysed by gas chromatography.

(24) The composition of the mixture, after subtraction of water and methanol and measured after 300 hours, was:

(25) p-toluidine: 0.48% by weight

(26) N-methyl-p-toluidine: 96.27% by weight

(27) N,N-dimethyl-p-toluidine: 3.25% by weight

(28) and after 600 h:

(29) p-toluidine: 0.59% by weight

(30) N-methyl-p-toluidine: 97.67% by weight

(31) N,N-dimethyl-p-toluidine: 1.74% by weight

(32) Even after 600 hours of running time, no significant deactivation of the catalyst was apparent.

Comparative Example 1

(33) Production of the catalyst analogously to U.S. Pat. No. 2,580,284:

(34) 209.5 g of aluminium oxide were admixed with 113 ml of an impregnation solution consisting of 94.33 g of calcium nitrate*4H.sub.2O and 48.7 g of copper(II) nitrate*3H.sub.2O dissolved in 34 g of water. After impregnation, the material was dried in a hot air dryer at 120 C. and subsequently calcined for 4 hours at 450 C. 243.9 g of catalyst having proportions of metals of 5.17% by weight of Cu and 6.46% by weight of Ca on aluminium oxide were obtained.

(35) Testing of the Catalyst:

(36) 81 ml of the catalyst produced in accordance with Comparative Example 1 were used analogously to Example 1 for the alkylation of p-toluidine.

(37) The typical composition of the mixture, after subtraction of water and methanol and measured after 300 hours, was:

(38) p-toluidine: 33.02% by weight

(39) N-methyl-p-toluidine: 66.70% by weight

(40) N,N-dimethyl-p-toluidine: 0.28% by weight

(41) The direct comparison of the two catalysts is represented in FIG. 1. It is clearly apparent that the catalyst used according to the prior art has a service life of less than 300 hours, whereas the catalyst according to the invention displays no deactivation even after 600 hours.