KR820001586B1 - Process for production of tertiary butyl methyl ether - Google Patents

Abstract

C4 Hydrocarbon streams contg. 5-60 wt.% isobutene were contacted with MeOH(MeOH-isobutene molar ratio 1.02-1.20) over acid ion exchange resins at 90-170↿F and 12-25 atm to give the title ether. A stream contg. 4% isobutene was contacted with MeOH(7% excess) over Dower 50 at 150↿F and -20 atm. to give the title ether.

Description

Process for preparing tert-butyl methyl ether

1 is a graph showing the correlation between polymer formation when the molar ratio of methanol and isobutylene is changed.

2 is a graph showing the correlation with the methanol-butene azeotrope concentration when the pressure is changed.

FIG. 3 is a graph showing the correlation between the debutene column pressure required to remove all methanol from tert-butyl methyl ether when the molar ratio of methanol to isobutene was changed at 93% conversion of isobutene.

4 is a process diagram for producing a TBME according to the present invention.

The present invention relates to a process for inhibiting the formation of diisobutylene and / or triisobutylene and purifying crude product to produce tert-butyl methyl ether.

In the prior art, Rum et al. Described a method for selectively etherifying tertiary olefins with alcohols using an acidic ion exchange catalyst in US Pat. No. 2,480,940, and Hound Shield in US Pat. No. 3,629,478 as a clean-up reactor. A process for preparing tertiary butyl methyl ether in two stages using an exchange resin was described. Offenaus et al., Published in the German Federal Republic Publication No. 2,629,769 (published on Jan. 5, 1978) followed by elevated pressure. A method for azeotropic separation of methanol from TBME has been described by azeotropic distillation and separation of unreacted C ₄ hydrocarbons from the effluent discharged from the reactor. This German patent emphasizes the formation of azeotropic mixtures of TBME and methanol.

Although many people have made steady efforts in the manufacture of TBME for decades, efforts are still underway to produce TBME free of diisobutylene, methanol and similar impurities.

According to the present invention, the pressure used to separate unreacted C ₄ hydrocarbons from the effluent to prepare TBME is 7 to 25 atm and prevents the formation of diisobutylene, triisobutylene and other undesirable byproducts. In order to suppress, the reaction mixture should be adjusted to contain 2 to 20% excess methanol.

As shown in FIG. 4, the C ₄ hydrocarbon fraction 11 containing n-butene and 5% to 60% isobutene is mixed with an appropriate amount of methanol fraction 12 so that the unit molar ratio of methanol to isobutene is 1.02 to 1.20, preferably Obtain a reaction mixture fraction 13 which is 1.03 to 1.07. This unit molar ratio may be 2 to 20% excess methanol with respect to the formula quantitative reaction molar ratio. Particular attention is paid to the formation of diisobutylene and triisobutylene when the reaction mixture contains excess methanol. Fresh feed mixture 13 containing 2-20% excess methanol is introduced into reactor 14 containing the catalyst bed of acidic ion exchange resin. The etherification reaction is carried out at an hourly space, per weight of dry catalyst, at a space velocity of 2 to 20 total feed weight. The reactor temperature is in the range of 90 to 170 ° F. and for temperature control a portion of the reactor effluent may be recycled by mechanical operation. The fraction 15 exited from the reactor 14 is introduced into a pressurized azeotropic distillation zone 16 while maintaining the pressure of the azeotropic distillation zone 16 at 7-25 atmospheres. The azeotropic distillate 17 is a mixture of n-butene and methanol with a molar concentration of 5 to 15% of the mixture of methanol and C ₄ hydrocarbons, and unreacted isobutene is part of this distillate. Of particular importance, bottom oil 18 is composed of high purity tert-butyl methyl ether with little methanol, eliminating the need to wash TBME with water before using it as a fuel component in gasoline.

The maximum temperature required for distillation uses a lower temperature than when distilling TBME at the same pressure.

In various variations of the invention, it is easy to change the molar ratio of methanol to isobutene to 1.02 to 1.2 (i.e. excess of 2 to 20%), which still has the advantages of the present invention.

In order to inhibit the formation of diisobutylene or triisobutylene, there should be enough excess methanol in the reaction mixture.

As shown in Figure 1, it can be seen that the polymer formation increases as the molar ratio of methanol: butene decreases. Furthermore, it is desirable to maintain excess methanol to promote the formation of tert-butyl methyl ether at suitable space velocities and temperatures. It is not necessary to bring the tert-butyl methyl ether to reach the theoretical equilibrium concentration, which can be achieved by suitable conversion with suitable selectivity using small reactors with good machine operation and high space velocities.

The reactor may be equipped with a mechanical thermostat for controlling the temperature. The selectivity of isobutene in producing tert-butyl methyl ether is preferred when the unit molar ratio of methanol to isobutene in the fresh feed is 1.02 to 1.20.

Large amounts of excess methanol should not be used because this excess is not completely removed by azeotropic distillation of butenes. If the concentration of isobutene in the new feed C ₄ hydrocarbon fraction is too high to azeotropically remove both unreacted excess methanol and butene even with a molar ratio of methanol of 1.2, recycle some of the butenes and total feed C ₄ The concentration of isobutene in the hydrocarbon fraction should not exceed 60%. It is also expensive when the concentration of isobutene in the total C ₄ hydrocarbon feed is 5% or less, so it is preferred that the concentration of isobutene is between 5% and 60%.

According to figures 1,2 and 3, it can be seen that increasing the pressure increases the concentration of methanol in the azeotropic mixture, which is a surprising finding. Furthermore, in a suitable conversion, the unit molar ratio of the reactants and the pressure in the azeotropic distillation zone can affect the complete removal of methanol from the bottom fraction containing industrial tertiary butyl methyl ether.

As can be seen clearly in FIG. 4.

In washing the C ₄ hydrocarbon distillate, methanol is extracted from the hydrocarbon by washing with water and recycled.

In the distillation process, methanol can be recovered for recycle.

In a preferred embodiment, the fresh C ₄ hydrocarbon contains 40% of isobutene and the reaction effluent is not recycled.

The methanol concentration shows a 7% excess above the formula weight, and the reactor maintains an average temperature of 150 ° F. and an hourly space velocity of 7 times the total feed, per weight of Dowex 50 acidic ion exchange resin. The effluent is transferred to a distillation column maintained at 20 atmospheres. Most of the system maintains 19 to 21 atmospheres.

The azeotrope contains 12% methanolated 88% C ₄ hydrocarbons. The azeotrope is detained with 25% by volume of water and the extract is distilled off to recover methanol in recycle. Tertiary butyl methyl ether, the bottom fraction of the azeotropic distillate, is purified and used for gasoline, which contains little methanol and therefore does not require washing with water or distillation of TBME.

Many variations of the invention are possible and are within the scope of the invention.

Claims (1)

In the preparation of tertiary butyl methyl ether by reacting a C ₄ hydrocarbon containing n-butene and a large amount of isobutene with methanol in the presence of an acidic ion exchange resin catalyst, the concentration of iso-butene in the hydrocarbon and C ₄ fractions was determined. After adjusting to 5 to 60% based on the weight of the C ₄ hydrocarbon fraction in the water, and suppressing the formation of diisobutylene in the reactor by the unit molar ratio of methanol to isobutene in the total feed of 1.02 to 1.20, methanol, Acidic ion exchange of a total feed mixture containing isobutene and other C ₄ hydrocarbons, wherein the total feed is methanol to isobutene has a unit molar ratio of 1.02 to 1.20 at a weight rate of 2 to 20 per hour at 90 to 170 ° F. tert passed through a reactor containing the catalyst-butyl methyl ether, C ₄ to obtain an effluent comprising a hydrocarbon and an excessive amount of methanol to move this distillate as the azeotropic distillate emanating from 7 to 25 atm From the removal of substantially all of the methanol from tertiary-butyl methyl ester, it characterized in that the recovery of tert-butyl methyl ether by removing azeotropically with methanol in the effluent almost all of the C ₄ hydrocarbons by distilling a C ₄ hydrocarbon and then, A process for producing purified tertiary butyl methyl ether as a bottom oil from a pressurized azeotropic distillation table.

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