PROCESS FOR THE ALKYLATION OF PHENOLS

Abstract

The present invention relates to a process for the preparation of 2,6-di-tert-butyl phenol by reacting phenol with isobutylene in presence of an aluminum phenoxide catalyst, comprising i) preparing an aluminum phenoxide catalyst and phenol comprising mixture a) by mix-ing aluminum metal with phenol, and activating the catalyst by heating the mixture to a temperature of 100 to 180? C., and ii) carrying out a reaction b) by reacting mixture a) with an isobutylene comprising stream comprising 20 to 90% by weight of isobutylene and 10 to 80% by weight of 1-butene and/or 2-butene, which reaction is carried out under pressure and the maximum pressure is 5 to 20 bar.

Claims

1. A process for the preparation of 2,6-di-tert-butyl phenol by reacting phenol with isobutylene in presence of an aluminum phenoxide catalyst, the method comprising: i) preparing an aluminum phenoxide catalyst and phenol comprising mixture a) by mixing aluminum metal with phenol, and activating the catalyst by heating the mixture to a temperature of 100 to 180? C.; and ii) carrying out a reaction b) by reacting mixture a) with an isobutylene-comprising stream comprising 20 to 90% by weight of isobutylene and 10 to 80% by weight of 1-butene and/or 2-butene, wherein the reaction is carried out under pressure and the maximum pressure is 5 to 20 bar.

2. The process according to claim 1, wherein the activation of the catalyst of mixture a) is carried out at a temperature of 120 to 180? C.

3. The process according to claim 1, wherein reaction b) is carried out at a temperature of 90 to 140? C.

4. The process according to claim 1, wherein for reaction b) a molar ratio of isobutylene to phenol is 1.9 to 2.6.

5. The process according to claim 1, wherein in reaction b) the maximum pressure is 10 to 20 bar.

6. The process according to claim 1, wherein the amount of isobutylene in the stream is 20 to 70% by weight.

7. The process according to claim 1, wherein the amount of isobutylene in the stream is 20 to 60% by weight.

8. The process according to claim 1, wherein the amount of 1-butene and 2-butene in the stream is 15 to 60% by weight.

9. The process according to claim 1, wherein during reaction b) at least one time the pressure is released and unreacted stream is removed.

10. The process according to claim 9, wherein during reaction b) the stream is fed continuously, wherein the feeding is at least one time interrupted by releasing the pressure and removing unreacted stream.

Description

EXAMPLE

a) Preparation of Aluminum Phenoxide Catalyst and Phenol Containing Mixture

[0031] Air from an autoclave is removed by flushing with nitrogen. 129 g of phenol as crystals are added to the inertised reactor together with 0.38 g of aluminum. The reactor is closed and the mass is heated under stirring up to 160? C. within 25 minutes. Once the target temperature is reached, the final pressure is normally 14.5 to 15.5 bar. These conditions are kept for 30 minutes, and then the gas is removed from the autoclave until an inner pressure (Pi) of 2 to 3 bar is reached. The reaction mass is cooled down to 90? C. within 30 minutes. Once the target temperature is reached, the residual pressure is released.

b) Reaction of the Mixture Prepared According to a) with an Isobutylene Comprising Stream

[0032] The mixture prepared according to a) is reacted with a stream comprising 78.5% isobutylene, 15% 1-butene, and 6.5% isobutane (each in percent by weight, based on the total weight of the stream).

[0033] The initial reaction temperature is 90? C. The stream is charged into the reactor at the rate of 4 g/minute for the first thirty two minutes (first addition of reactant gas).

[0034] Temperature is raised to 121? C. at the rate of 1.1? C./minute after 20 minutes of stream addition. Once the temperature is reached the pressure is about 15 bar.

[0035] The temperature is held steady at 121? C. for 65 minutes before cooling the reaction mass to 90? C. at the rate of 1? C./minute. In the course of holding the reaction mass at the temperature of 121? C. the pressure drops down to 9 bar.

[0036] The stream is then added at the start of the cool down period at the rate of 4 g/minute for 20 minutes (second addition of reactant gas). During the second addition of reactant gas, the pressure reaches again about 15 bar and at the end of cooling it is dropped down to 9 bar.

[0037] The temperature is held at 90? C. for the remainder of the reaction in which the pressure drops down to about 7 bar.

[0038] The total reaction time is 5 hours. The molar ratio of isobutylene to phenol is 2.12.

Comparative Example

[0039] The procedure of the above Example is followed exactly, but using a stream comprising 78.5% isobutylene, 1.1% 1-butene and 20.4% isobutane (each in percent by weight, based on the total weight of the stream).

Results

[0040]

TABLE-US-00001 Comparative Example Example 2,6-di-tert-butyl phenol 85.0% 73.6% Unreacted phenol 0.0% 0.5% By-product 2-tert-butyl phenol 3.7% 15.8% By-product 2,4-di-tert-butyl phenol 0.4% 1% By-product 2,5-di-tert-butyl phenol 0.1% 0.3% By-product 2,4,6-tri-tert-butyl phenol 10.0% 7.8% By-product 2-sec-butyl-6-tert-butyl phenol 0.2% 0% Sum of by-products 14.4% 24.9%

[0041] All amounts indicated in the above Table are given in percent by weight, based on the weight of the crude product obtained according to the respective example.

[0042] The amount of 2-sec-6-tert-butyl phenol in the Example according to the present invention is 0.2%, representing the reaction of 0.4% of the 1-butene in the initial stream.