Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1995-05-19
2001-04-17
Moore, Margaret G. (Department: 1712)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S698000, C568S699000
Reexamination Certificate
active
06218582
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
This invention relates to a process for the manufacture and purification of methyl tertiary butyl ether. More particularly, this invention relates to a process for reducing the formation of tertiary butyl alcohol in a finishing reactor in a process for the manufacture of methyl tertiary butyl ether (MTBE) from tertiary butyl alcohol (TBA) and methanol (MeOH). Still more particularly, this invention relates to a process for the manufacture of MTBE from TBA and MeOH wherein by-product isobutylene formed by the reaction of TBA with MeOH is reacted with methanol in a finishing reactor under substantially anhydrous conditions to selectively provide additional methyl tertiary butyl ether with the reduced formation of tertiary butyl alcohol.
2. Prior Art
In U.S. Pat. No. 4,144,138 (1979) to Rao et al., there is disclosed a method for recovering methyl tertiary butyl ether from etherification reaction effluent by azeotropic distillation to recover methanol-ether azeotrope overhead which is water-washed to give pure ether extract, the latter being azeotropically distilled to yield ether-methanol overhead which is recycled to water washing.
The preparation of methyl tert-butyl ether from methyl and tert-butyl alcohols is discussed in S. V. Rozhkov et al., Prevrashch Uglevodorodov, Kislotno-Osnovn. Geterogennykh Katal. Tezisy Dokl., Vses. Konf., 1977, 150 (C. A. 92:58165y). Here the TBA and methanol undergo etherification over KU-2 strongly acidic sulfopolystyrene cation-exchangers under mild conditions. This reference contains data on basic parameters of such a process.
Kruse et al. U.S. Pat. No. 5,243,091 discloses a method for the preparation of methyl tertiary butyl alcohol wherein a mixture of methanol and tertiary butyl alcohol are catalytically reacted to form a reaction product that is separated into a first lighter distillation fraction comprising isobutylene, methanol and methyl tertiary butyl ether and a second heavier distillation fraction comprising methanol, tertiary butyl alcohol and water, wherein the first distillation fraction and a first recycle isobutylene fraction are reacted to form an isobutylene conversion product that is charged, together with recycle isobutylene to a methanol extraction zone and countercurrently contacted with water to provide an overhead raffinate comprising aqueous isobutylene, and wherein the isobutylene is recovered and recycled.
Gupta U.S. Pat. No. 5,292,964 discloses a method for the preparation of methyl tertiary butyl ether wherein a mixture of methanol and tertiary butyl alcohol are catalytically reacted to form a reaction product containing the water of etherification and at least one mol of methanol per two moles of methyl tertiary butyl ether, wherein the reaction product is fractionated to separate a lighter methanol and methyl tertiary butyl ether fraction from the water and tertiary butyl alcohol and wherein the methanol in the lighter distillation fraction is reacted with isobutylene to form additional methyl tertiary butyl ether.
Gupta states that it is essential to provide a reaction product containing at least one mol of methanol per two moles of methyl tertiary butyl ether, so that water is separable from the methyl tertiary butyl ether in the fractionating column to provide a lighter distillation fraction substantially free from water.
BACKGROUND INFORMATION
Methyl tert-butyl ether is finding increasing use as a blending component in high octane gasoline as the current gasoline additives based on lead and manganese are phased out.
It is known to react methanol with tertiary butyl alcohol in the presence of a catalyst in order to produce methyl tertiary butyl ether. A wide variety of catalysts have been suggested for this purpose.
In U.S. Pat. No. 2,282,469 to Frolich there is disclosed a process for preparing methyl tertiary butyl ether over a catalyst comprising Kieselguhr impregnated with phosphoric acid at a temperature of about 175° F. to 350° F.
Japanese Patent 0007432 teaches the use of zeolites to make dialkyl ethers containing primary or secondary alkyl groups. The zeolites have a porous structure and are represented by:
M
2
O·Al
2
O
3
·xSiO
2
·yH
2
O
where M is an alkali metal or alkaline earth metal cation or organic base cation, n is the valence of the cation and x and y are variables.
U.S. Pat. No. 4,058,576 to Chang et al. teaches the use of (pentasil-type) aluminosilicate zeolites, such as ZSM-5, having a pore size greater than 5 angstrom units and a silica-to-alumina ratio of at least 12, to convert lower alcohols to a mixture of ethers and olefins.
In U.S. Pat. No. 4,822,921 there is disclosed a method for producing MTBE by reacting tertiary butyl alcohol and methanol in the presence of a catalyst comprising an inert support, such as titania, having a phosphoric acid impregnated thereon.
U.S. Pat. No. 4,827,048 discloses a method for producing MTBE by reacting tertiary butyl alcohol and methanol in the presence of a catalyst comprising a heteropoly acid such as 12-tungstophosphoric acid or 12-molybdophosphoric acid on an inert support, such as titania.
Two of the principal by-products formed during the reaction of the methanol with the tertiary butyl alcohol are water and isobutylene. Methanol and methyl tertiary butyl ether form an azeotrope which is broken only with difficulty and therefore the separation of methanol from MTBE during the recovery of purified methyl tertiary butyl ether presents a serious problem.
In U.S. Pat. No. 4,820,877, separation of methanol from MTBE is accomplished by using a refinery fuel gas to enhance the separation of methanol into the overhead stream of a distillation column.
In U.S. Pat. No. 4,814,517, separation of methanol from MTBE is accomplished by using a silica gel to preferentially adsorb methanol from an MTBE stream and by periodically regenerating the silica gel.
In U.S. Pat. No. 4,798,674, separation of methanol from MTBE is accomplished by using a membrane of cross-linked polyvinyl alcohol or a quaternary ammonium ion resin. Methanol preferentially permeates through the membrane increasing the MTBE concentration of the charge liquid.
In U.S. Pat. No. 4,759,850, separation of methanol from MTBE is accomplished by reverse osmosis.
In U.S. Pat. No. 4,440,963, separation of methanol from MTBE is accomplished by adding an agent such as 2-methyl pentane or Freon 113 to form an azeotrope with methanol. This azeotrope is recovered overhead giving a methanol-free MTBE bottoms product.
As recognized by Rao et al. in U.S. Pat. No. 4,144,138, isobutylene is formed as a by-product when methanol is reacted with tertiary butyl alcohol. In accordance with the Rao process, the isobutylene is separated from the reaction product in an initial azeotropic distillation step as a noncondensable gas. Rao teach that the part of the isobutylene may be flashed from the reaction product for recycle, depending upon purity.
SUMMARY OF THE INVENTION
This invention relates to a process for the manufacture of MTBE from TBA and MeOH wherein by-product isobutylene formed by the reaction of TBA with MeOH is reacted with methanol in a finishing reactor under substantially anhydrous conditions to selectively provide additional methyl tertiary butyl ether with the reduced formation of tertiary butyl alcohol.
A preferred process for reducing the formation of tertiary butyl alcohol in a finishing reactor in the manufacture of methyl tertiary butyl ether (MTBE) from tertiary butyl alcohol (TBA) and methanol (MeOH) comprises the steps of:
a) continuously passing a feed mixture comprising substantially peroxides-free tertiary butyl alcohol and methanol through a methyl tertiary butyl ether etherification reaction zone containing a bed of a TBA/MeOH etherification catalyst under etherification reaction conditions to form an etherification reaction product comprising unreacted methanol, unreacted tertiary butyl alcohol, water, isobutylene (IBTE) and methyl tertiary butyl ether,
b) continuously charging the etherification reaction product to a me
Benac Brian Lawrence
Kruse Charles Joseph
Preston Kyle Lee
Brown Ron D.
Huntsman International LLC
Moore Margaret G.
Ries Carl G.
Stolle Russell R.
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