CS233221B3 - A method of alkylating p-cresol and / or tert -butyl-p-cresol - Google Patents

Abstract

Alkylation, or tert-butylation of p-cresol, as well as tert-butyl-p-cresol with the aim of producing mainly 2,6-di-terto-butyl-p-cresol is carried out according to MS. AO 202 607, where the tert-butylating agent is tert-butyl alcohol or methyl tert-butyl ether, also occurs with isobutene. It is difficult to remove by-products from the reaction environment, mainly methanol and water, as well as dimethyl ether and diisobutenes. The presence of methanol and water must not exceed 10% by weight in the reaction medium, it slows down the tert-butylation and reduces the yields of 2,6-di-tert-butyl-p-cresol.

Description

233221 2

The invention was solved in relation to MS. AO 202 607 discloses a process for the alkylation of p-cresol and / or tert-butyl-p-cresol, mainly with the aim of producing 2,6-di-tert-butyl-p-cresol using non-traditional tert-butylating agents. It has long been known to tert-butylate phenol with isobutanol or tert-butyl alcohol in the liquid phase under the catalytic action of strong mineral acids such as sulfuric acid, then zinc chloride, further strong acid cation exchangers and the like. [Liebmann A: Ber. 14th 1842 (1881); Ber. 15, 547 (1882); Belov P. S. and Col. Chim. thought. 1962. 470; FROM. prikl. chim. 21, 162 (1962); U.S. Pat. 2,923,745; 2,739,172 and 3,267,154; V. Brit. pat. 1 191 769], but relatively low yield and considerable catalyst consumption are achieved.

Very good results are obtained by isobutene tert-butylation. however, it is more difficult to obtain pure when used in admixture with other hydrocarbons, e.g., butadiene-denigrated pyrolysis (e.g., U.S. Pat. No. 202,461), other hydrogen sulfides, especially n-butenes, n-butene and isobutane, need to be utilized which remain after the isobutene is reacted.

However, this requires a special additional device and the possibility of technically and economically evaluating said C ^ ^-hydrocarbons. These problems are solved and, moreover, utilized by the novel tert-butylating agents for the alkylation of phenol and / or alkylphenol according to U.S. Pat. AO 202-607. In doing so, the specification of the conditions of the present invention solves the present invention.

According to the present invention, a process for the alkylation of p-cresol and / or tert -butyl-p-cresol, mainly to 2,6-di-tert-butyl-p-cresol, with the catalytic action of sulfuric acid and / or perchloric acid and / or or p-toluenesulfonic acid according to U.S. Pat. According to certificate 202 607, the tert-butylating agent is tec-butyl alcohol and / or methyl tert-butyl ether, optionally together with isobutene and / or isobutene-containing condensate, the resulting products being removed from the tert-butylation environment , generally together with the unconverted starting materials and the 2,6-di-tert-butyl-p-cresol formed is isolated. An advantage of the method of alkylating p-cresol and / or tert -butyl-p-cresol according to the invention is the fact that, in addition to tert-butyl alcohol, methyl tert-butyl ether as tert-butylating agents is easy to transport and store. Furthermore, the fact that the alkylating catalyst is also used in one step for the catalytic-thermal decomposition of methyl-tert-butyl-aperture isobutene and methanol or the tert-butyl alcohol dehydrate. By removing methanol and water from the tert-butylation medium, the rate of tert-butylation and the yields of β-tert-butyl-β-cresol and especially 2,6-di-tert-butyl-β-cresol is increased. Another advantage is the possibility to use isobutene, respectively. regenerated isobutene with other, mainly lowering components.

The tert-butylation of p-cresol and / or tert-butyl cresol is suitable at atmospheric pressures at temperatures of 70-140 ° C, but it is even more preferable to operate at 90-110 ° C so as to remove as much as possible. distilling off methanol and water from the reaction medium, as well as other minor low boiling products, especially dimethyl ether and diisobutenes. Water and methanol have a particularly negative effect on the tert-butylation rate as well as the yield of 2,6-di-tert-butyl-p-cresol.

Therefore, it is necessary to take care of them quickly, according to the possibility of complete removal from the reaction medium; their concentration in the reaction medium should in no case exceed a concentration of 10% by weight. In addition to methyl tert-butyl ether or tert-butyl alcohol, isobutene may be fed simultaneously as the tert-butylating agent, alone or with other C -u-hydrogen sulfides, in particular with methyl tert-butyl ether, dimethyl ether, or as long-butenes, i.e. as obtained from the regeneration of uncoupled isobutene already formed from tert-butyl alcohol or methyl tert-butyl ether. 3 233221

In this case, it is suitable to introduce into the reaction medium preheated alkylating agents and to the bottom of the alkylator in order to obtain a sufficient residence time of the formed isobutene required for tert-butylation of p-cresol and tert-butyl-p-cresol. For preheating, it is advantageous to use condensation heat of the leaving low fractions or even the reaction temperature of tert-butyl.

The process of the present invention is particularly suitable for the preparation of 2,6-di-tert-butyl-p-cresol, which is generally isolated from the reaction medium, and tert-butyl-p-cresol is most frequently returned from the separating line at least substantially. into the alkylation, respectively. a tert-butylation reactor wherein tert-butyl is combined with p-cresol. Further details of the method of the invention, as well as other advantages, will be apparent from the examples. Přikladl

50 g of p-cresol having a purity of 98% by weight are placed in a 250 cnP three-necked flask equipped with a thermometer stirrer. and 0.75 g of sulfuric acid at a concentration of 98% by weight.

The contents of the flask are heated to 102 ± 2 ° C with an oil bath and methyl tert-butyl ether with a purity of 99% by weight is fed to the bottom of the flask. at 13.6 g.h- for 8 h.

Under these conditions, the methyl tert-butyl ether is decomposed to isobutene and the methanol is temporarily alkylated with p-cresol by the resulting isobutene. Outgoing vapors from the flask are cooled with a water cooler. The condensed liquid particles are trapped! in the separator, non-condensed! in the freezer cooled to -30 ° C.

The product in the flask at 93.6 g contains 0.94 wt. unreacted p-cresol and 38.4 wt. 2,6-di-tert-butyl-p-cresol. 46.7 g of a liquid product of this composition (5 wt.%): 16.4 isobutene, 27.8 methyl tert-butyl ether, 1.0 diisobutenes and 54.0 methanol are collected in a separator. 19.6 g of the composition (% w / w): 90.0 isobutene, 5.5 methyl-tert-butyl ether, 2.0 diisobutenes and 2.5 methanol are collected in the freezer. The total yield at this stage is the conversion of p-cresol to 98.2%, the conversion of methyl-tert-butyl ether to 87.1% and the yield of 35.6% of 2,6-di-tert-butyl-p-cresol relative to the p-cresol used.

The contents of the flask are cooled to 80 ± 2 ° C and alkylated with pure isobutene at 9.4 g / h for 3.5 h to give 102 g of the alkylated product containing 80.7% by weight of 2,6-diisocyanate. tert-butyl p-cresol and 0.2 wt. unreacted phenol. Overall, the conversion of p-cresol was 99.6% and the yield of 80.8% was 2,6-di-tert-butyl-p-cresol. Example 2-

The procedure is similar to Example 1, with the difference that a 0.5 dm three-necked flask? 150 g of p-cresol having a purity of 98% by weight are placed. and 5.01 g of sulfuric acid at a concentration of 98% by weight. Methyl tert-butyl ether was introduced into the flask with stirring at 46.5 g / h for 10 h. 236.3 g of a liquid lower-boiling portion of the composition (% by weight) were collected in the separator: 12.5 isobutene, 33.6 methyl tert-butyl ether, 3,4-diisobutene 50.5 methanol. In the freezer, 72 g of a lower weight fraction (% by weight) are collected: 88.2 isobutene, 9.07 methyl tert-butyl ether, 0.4 diisobutenes and 2.4 methanol. The 298.7 alkylated product remained in the flask (% w / w): 0.12 p-cresol and 65 2,6-di-tert-butyl-p-cresol. At this stage, the conversion of p-cresol to 99.8% and the yield of 64.8% of 2,6-di-tert-butyl-β-cresol with respect to β-cresol is achieved. The product is cooled to 85-2 ° C and alkylated at this temperature with a condensate from the freezer at 5.8 g / 6 h. 320.4 g of alkylated product (% by weight) is obtained: 0.1 p-cresol and 74.2 2,6-di-tert-butyl-β-cresol. Overall, the conversion of p-cresol to 99.80 and the yield of 79.4% of 2,6-di-tert-butyl-β-cresol relative to β-cresol is achieved. Example 3

The procedure is similar to that of Example 2 except that the methyl tert-butyl ether which is fed to the alkylation at 38.4 g / h for 8 h is preheated to 65 ° C in the preheater. In the separator, 137 g of a liquid lowering fraction (.wt.%) Were collected: 12.4 isobutene, 26.1 methyl-tert-butyl ether, 3,7-diisobutenes and 57.8 methanol. 9 g of a lowering condensate of composition (% by weight): 89.9 isobutene, 7.8% methyl tert-butyl ether, 0.4 diisobutenes and 1.9 methanol. There remain 293.6 g of alkylated product in composition (% by weight): 0.45 p-cresol and 58.8 2,6-di-tert-butyl-p-cresol. At this stage, the conversion of p-cresol was 99.1% and the yield of 2,6-di-tert-butyl-p-cresol was 57.7% relative to the annealed p-cresol. The product in the flask is cooled to 86 ± 2 ° C and the salt is alkylated with a mixture of the same composition as the lower condensate freezer at 8.8 g / h for 6 h to give 325.9 g of the alkylated product (% by weight). ): 0.15 p-cresol and 81.3 2,6-di-tert-butyl-p-cresol. A total of 99.7% p-cresol was obtained and the yield of 2,6-di-tert-butyl-p-cresol was 88.0% based on the suspended p-cresol. Example 4 3

50 g of p-cresol having a purity of 98% by weight are placed in a 250 cm 3-necked flask equipped with a stirrer and a thermometer tempered with an oil bath and 0.75 g of 98% sulfuric acid is added. . and 0.5 g of perchloric acid at a concentration of 70% by weight. A 1: 1 mixture of n-hexane and tert-butyl alcohol is introduced into the bottom of the flask at 22.5 g / h for 8 h. Under these conditions, the tert-butyl alcohol is decomposed to isobutene and water and concomitant alkylation is carried out. cresol formed by isobutene. The vapor leaving the flask was cooled in an aqueous cooler and passed to a separator. Condensed steam is trapped! in a separator and non-condensed fractions are freeze-dried at -30 ° C.

The crude product in the flask at 92.9 g contains 1.2 wt. % unreacted p-cresol 36.1 wt. 2,6-di-tert-butyl-p-cresol. The contents of the flask are cooled to 60-2 ° C and alkylated with pure isobutene at 9.1 g / h for 4 h to give 103 g of the alkylated product with 82.7% by weight. 2,6-di-tert-butyl-p-cresol and 0.1 wt. p-cresol. Overall, the conversion of p-cresol was 99.8% and the yield of 2,6-di-tert-butyl-p-cresol was 83.6% relative to p-cresol. Example 5

Using a three-necked 250 cm 2 beaker equipped with a stirrer, tempered at 80 ° C with an oil bath, the effect of water and methanol on the p-cresol tert-butylation rate by isobutene and the 2,6-di-tert-butyl yield was investigated. butyl-p-cresol. In each experiment, 50 g of p-cresol, 0.75 g of sulfuric acid and an isobutene feed of 4.25 g are used in the batches. methanol and the reaction time are shown in Table 1. The results show the most potentating effect of water, but the presence of methanol in the reaction medium is undesirable.

Claims (2)

5 233221 Table 1 Additive Kind Quantity [% w / w cresol] 2 4 (reference) 2.6 8.4 water 3.4 2.2 6.6 water 7.6 1.1 2.9 water 13, 8 0,1 0,2 Methanol 3,2 4,1 10,6 Methanol 7,8 2,1 10,2 Methanol 13,2 1,9 8,7 Yield 2,6-di-tert-butyl-p cresol Experiment time [h] 6 8 10 12 14 25.8 38.4 .56.9 71.3 80.1 19.6 35.0 43.4 48.4 50.4 8.1 14.7 21, 1 23.5 23.8?, 4 0.6 1.7 3.0 - 21.4 36.9 55.1 69.0 71.9 19.0 33.3 41.2 50.9 56.3 17.4 28.1 35.6 44 * 1 45.9 P RE DME T INVENTION 1. A process for the alkylation of p-cresol and / or tert-butyl-p-cresol, in particular to 2,6-di-tert-butyl-p-cresol, under the catalytic action of sulfuric acid and / or chloristeil / or p-toluenesulfonic acid , under Ta 2s. AO 202 607, characterized in that the tert-butylating agent is tert-butanol and / or methyl tert-butyl ether, optionally together with isobutene / or isobutene-containing condensate, wherein the byproducts formed are removed from the tert-butylation environment, generally together with unconverted starting "raw materials" and the 2,6-di-tert-butyl-p-cresol formed is isolated. 2. A method of alkylation according to claim 1, characterized in that the resulting by-products, such as water, methanol, dimethyl ether and diisobutenes, are removed from the tert-butylation environment, preferably continuously so that their content in the tert-butylation reaction medium is not exceeded. % by weight.