CN108774100B

CN108774100B - Combined method for preparing methyl tert-butyl ether and isobutene from tert-butyl alcohol and methanol

Info

Publication number: CN108774100B
Application number: CN201810403251.2A
Authority: CN
Inventors: 朱德权; 代俊明; 马敏; 解淑民
Original assignee: CENWAY TECHNOLOGIES Ltd
Current assignee: CENWAY TECHNOLOGIES Ltd
Priority date: 2018-04-28
Filing date: 2018-04-28
Publication date: 2020-01-21
Anticipated expiration: 2038-04-28
Also published as: WO2019206324A1; CN108774100A

Abstract

The invention provides a combined method for preparing methyl tert-butyl ether and isobutene from tert-butyl alcohol and methanol, which is carried out in a device comprising a catalytic rectifying tower, wherein the catalytic rectifying tower comprises a catalytic reaction section positioned in the middle part, tert-butyl alcohol enters the catalytic rectifying tower from the catalytic reaction section, and methanol and water enter the catalytic rectifying tower from the top of the tower; in the catalytic reaction section, one part of tertiary butyl alcohol is dehydrated to generate isobutene, and the other part of tertiary butyl alcohol and the isobutene respectively continue to react with methanol fed from the top of the tower to generate methyl tertiary butyl ether; wherein the tert-butyl alcohol is pretreated, and the feeding molar ratio of the tert-butyl alcohol to the methanol is 10: 1-10: 9. The combined process combines reaction and separation, promotes the reaction to be carried out rightwards, completes the synthesis of preparing isobutene and MTBE by dehydrating tert-butyl alcohol by a one-pot method, greatly simplifies the operation flow, reduces the process cost, facilitates the implementation and integrally improves the conversion rate of raw materials.

Description

Combined method for preparing methyl tert-butyl ether and isobutene from tert-butyl alcohol and methanol

Technical Field

The invention belongs to the technical field of chemical synthesis, and particularly relates to a combined method for preparing methyl tert-butyl ether and isobutene from tert-butyl alcohol and methanol.

Background

Methyl tert-butyl ether and isobutene are important C4 raw materials, and are mainly separated and reacted from mixed C4 by-products of oil refining, ethylene cracking and coal-to-olefin production.

After the mixed C4 extracts butadiene from the mixture, the boiling points of isobutene and butene-1 in the remaining mixture are only different by 0.6 ℃, and the isobutene and the butene-1 are difficult to separate by a rectification method, and a method of adding methanol to generate methyl tert-butyl ether from the isobutene is generally adopted. The methyl tert-butyl ether is liquid at normal temperature and normal pressure, is convenient to transport, is mostly used for oil blending, and is prepared into isobutene by in-situ cracking to be used for synthesizing various organic chemical raw materials and fine chemicals such as butyl rubber, polyisobutylene, methacrylate and the like.

In order to obtain high-purity isobutene for the synthesis of butyl rubber and other products, the isobutene is prepared by two methods of cracking methyl tert-butyl ether or dehydrating tert-butyl alcohol. For example, CN201410670660.0 discloses a method for preparing high-purity isobutene by dehydrating tert-butyl alcohol.

US5741953 describes a process for the synthesis of methyl tert-butyl ether by reaction of tert-butanol with methanol. The process uses water as an extracting agent, the process flow comprises two reactors connected in series and a catalytic distillation tower, and the problem of azeotropic reaction of tertiary butanol and water is not considered, so that the total conversion rate of the tertiary butanol can only reach 84% at most.

US5744652 discloses a process for the preparation of methyl tert-butyl ether from the reaction of tert-butanol and methanol. The process comprises two reactors in series and a plurality of catalytic distillation columns. Similar to US5741953, in the preparation process of US5744652, the reaction and separation are completed in steps, not only because the azeotropic problem affects the total conversion rate of t-butanol, but also the reaction process is increased, which aggravates the economic cost.

CN201310257316.4 describes a synthesis process for the complete conversion of tert-butyl alcohol and methanol into methyl tert-butyl ether. The process uses ethylene glycol or octanol as an extracting agent, and avoids the azeotropic problem of tert-butyl alcohol and water. However, one extraction tower and two extraction agent recovery towers are added in the process flow, so that the equipment is complex and the investment cost is high.

In the disclosed technology, the excess methanol is reacted with tert-butyl alcohol to produce methyl tert-butyl ether, which requires recycling of methanol and a plurality of reactors to consume the excess methanol, thereby increasing energy consumption.

Therefore, there is a need for a new process that reduces the energy load associated with excess methanol, increases the reaction conversion efficiency, and significantly reduces the organic content of wastewater.

Disclosure of Invention

The invention aims to provide an integrated method for preparing methyl tert-butyl ether and isobutene from tert-butyl alcohol and methanol, which has the advantages of simple operation process, low energy consumption and cost and high conversion rate.

The invention realizes the aim through the following technical scheme:

an integrated method for preparing methyl tert-butyl ether and isobutene from tert-butyl alcohol and methanol is carried out in a device comprising a catalytic rectifying tower, wherein the catalytic rectifying tower comprises a catalytic reaction section positioned in the middle, tert-butyl alcohol (TBA for short) enters the catalytic rectifying tower from the catalytic reaction section, and methanol and water enter the catalytic rectifying tower from the top of the tower;

in the catalytic reaction section, a part of tertiary butyl alcohol is dehydrated to generate isobutene, and the other part of tertiary butyl alcohol and the isobutene respectively continue to react with methanol fed from the top of the tower to generate methyl tertiary butyl ether (which can be simply called MTBE);

wherein the tert-butyl alcohol is pretreated, and the feeding molar ratio of the tert-butyl alcohol to the methanol is 10: 1-10: 9.

In the embodiment of the invention, the feeding molar ratio of the tertiary butanol to the methanol is 10: 1-10: 5, preferably 10: 1-10: 2.

In the embodiment of the invention, the weight ratio of the water added at the top of the tower to the tertiary butanol is 1 (10-40), preferably 1 (20-30), such as 1:20, 1:22, 1:24, 1:26, 1:28, 1: 30.

In an embodiment of the present invention, excess t-butanol is reacted with methanol over a catalyst to produce isobutylene and methyl t-butyl ether.

According to the invention, the overhead product comprises isobutene which has not reacted with methanol, the methyl tert-butyl ether produced and unreacted tert-butanol, methanol and small amounts of water; the bottoms production is essentially water. Preferably, the overhead product is separated to yield isobutylene and methyl tertiary butyl ether.

Preferably, the compositions and the weight percentages of the components of the tower top extract comprise: 15-65 wt% of isobutene, 30-70 wt% of MTBE and 5-15 wt% of methanol.

In some preferred embodiments, after further separation and purification of the overhead product, a polymer grade isobutene content of not less than 99.9 percent and a methyl tert-butyl ether content of not less than 98 percent can be respectively obtained.

Preferably, the overhead output also contains some light impurity components, which may be acetone, for example.

In some preferred embodiments, the water, methanol, tert-butanol or any mixture thereof obtained after further separation and purification of the overhead is returned to the catalytic distillation column.

In some embodiments of the invention, the bottom temperature of the catalytic distillation column is 110 to 150 ℃, preferably 120 ℃, and the column pressure is 0.1 to 0.5MPa, preferably 0.3 MPa.

In some embodiments of the invention, the temperature of the catalytic reaction section of the catalytic distillation column is 90-120 ℃, preferably 100-110 ℃; the pressure is 300-310 kPa.

The applicant has found that in the prior art, when preparing methyl tert-butyl ether, the tert-butyl alcohol as the raw material is mostly an upstream reaction product without further purification treatment, and contains a large amount of organic impurities, wherein some organic impurities are easy to form azeotropes with water. The methyl tert-butyl ether prepared by using the tert-butyl alcohol often generates a large amount of sewage with high Chemical Oxygen Demand (COD) value, and the sewage is directly discharged to seriously affect the ecological environment; if the sewage is treated, the treatment procedure is very complicated, and the economic cost is increased. Thus, in some embodiments of the invention, the starting tert-butanol may be pretreated prior to being fed. For example, the tert-butanol is purified. The tertiary butanol before being fed may be purified using a purification method conventionally used in the art, such as extractive distillation, etc. In some preferred embodiments of the present invention, the t-butanol before feeding is purified by a rectification column to obtain a refined t-butanol having a mass content of not less than 95.5% and wherein the mass content of organic impurities capable of forming an azeotrope with water is not more than 0.1%.

In some embodiments of the invention, the subsequent reaction is carried out using refined tert-butyl alcohol, and the water taken from the bottom of the catalytic distillation column has a COD of not more than 2000, preferably less than 1000, at the most.

And the inventor has found through experiments that the COD of the water extracted from the bottom of the tower exceeds 15000, even 20000 if the tert-butyl alcohol is not purified before the reaction.

To increase separation efficiency, in some embodiments of the invention, water is supplemented to the top of the catalytic rectification column. The make-up water may be newly introduced water or may be circulating water collected after the reaction. After water is added from the top of the tower, the reflux ratio can be effectively increased, the reaction time is prolonged, and the reaction conversion efficiency is increased.

In some embodiments of the invention, the feed ratio of t-butanol to methanol in the reaction feed is adjusted within the above ranges according to downstream product requirements.

In the integrated process of the present invention, the catalytic rectification column may use a catalytic rectification column conventionally used in the art, for example, the specific configuration and characteristics of some conventional catalytic rectification columns are described in CN 202342929.

In some preferred embodiments of the present invention, the catalytic distillation column of the present invention comprises, in addition to the catalytic reaction section, a rectifying section and a stripping section, respectively located in the upper and lower portions of the catalytic reaction section. Wherein, the rectifying section and the stripping section can adopt a packed tower structure or a plate tower structure, and the invention preferably adopts the plate tower structure. More preferably, the number of theoretical plates is about 15-17. The separation effect is possibly poor due to the fact that the number of theoretical plates is too low, on one hand, COD (chemical oxygen demand) of the tower kettle sewage exceeds the standard, and on the other hand, the unit consumption is high due to the fact that a large amount of tert-butyl alcohol is wasted. If the number of the theoretical plates is too high, the investment and the energy consumption are too high.

According to the invention, in the catalytic distillation column, the catalytic reaction section is a middle part filled with a catalyst.

The catalytic reaction section has 4-10 (preferably 6) beds, and the feed inlet has 5-11 (preferably 7) beds and is respectively arranged on each bed and the first tower plate. The lower the feed position, the lower the reaction bed temperature. The feed location is currently preferably at the penultimate feed port.

In some embodiments of the invention, the catalyst may be the catalyst of patent US 4144138. Such as a cationic resin catalyst.

In some preferred embodiments, the catalyst is a sulfonic acid resin catalyst, such as Amberlyst 15, Amberlyst35, Amberlyst 70, and the like, preferably Amberlyst 15.

In some embodiments of the invention, the rectifying and stripping sections of the catalytic rectification column may be packed with packing, such as theta rings and/or glass packing.

In some embodiments of the present invention, the filler is prepared by wrapping DNW-II temperature-resistant resin catalyst (special resin limited of dandong mingzhu) in a stainless steel mesh and arranging the stainless steel mesh and the corrugated plate at intervals.

Preferably, the packing is structured packing, catalyst particles are wrapped in titanium mesh and made into sheets, and each sheet is sandwiched between two titanium corrugated sheets. This is described in particular in patent CN 205340190.

In some embodiments of the invention, the overhead product is condensed to obtain gas phase isobutene, and then the gas phase isobutene is separated and purified by a static separation unit, wherein the static separation unit comprises an oil-water separation tank for separating methyl tert-butyl ether and the rest of the overhead product.

In some embodiments of the invention, the mass content of the resulting gas-phase isobutene is not less than 97%.

In some embodiments of the invention, the major component of the organic layer in the miscella is methyl tert-butyl ether; the main components of the water layer in the oil-water separation tank are water, methanol, tert-butyl alcohol and methyl tert-butyl ether; preferably, the water layer is separated and returned to the top of the catalytic distillation tower for recycling.

Preferably, a rectifying device for further purifying the separated methyl tert-butyl ether is arranged after the oil-water separation tank.

Preferably, the organic layer containing methyl tert-butyl ether is separated and sent to a subsequent rectification device for further purification.

The distillation apparatus after the oil-water separation tank for further purification of methyl t-butyl ether may be a distillation apparatus conventionally used in the art. In some preferred embodiments, the rectification apparatus for purifying methyl tert-butyl ether has the following rectification conditions: 1) the temperature range of the tower bottom is 100-120 ℃, preferably 110 ℃, 2) the pressure range of the tower is 0.1-0.3 MPa, preferably 0.2 MPa; the top extract is methyl tert-butyl ether, and the bottom extract can be water, methanol, tert-butyl alcohol or any combination thereof. More preferably, the water, the methanol, the tertiary butanol or any combination thereof is returned to the top of the catalytic rectifying tower for recycling.

The invention has the beneficial effects that:

1) the combined process of the invention mainly dehydrates and converts excessive tert-butyl alcohol into isobutene, and can simultaneously produce isobutene and methyl tert-butyl ether, and the feed ratio can be conveniently adjusted according to the actual demand of the product in the production, thereby realizing the controllable preparation of the product.

2) The combined process combines reaction and separation, promotes the reaction to be carried out rightwards, completes the synthesis of preparing isobutene and MTBE by dehydrating tert-butyl alcohol by a one-pot method, greatly simplifies the operation flow, reduces the process cost, facilitates the implementation and integrally improves the conversion rate of raw materials.

3) The method has the advantages that the method that the methanol which is rarely adopted industrially is fed in a mode that the using amount of the tert-butyl alcohol is lower than that of the tert-butyl alcohol is adopted, so that the amount of the unreacted methanol in the process is greatly reduced, the subsequent separation steps and difficulty are reduced, the energy consumption is greatly reduced, and the conversion rate of the methanol can be further improved; meanwhile, the azeotropic problem of the tertiary butanol and the water is also overcome.

4) The raw material tert-butyl alcohol pretreatment process is adopted, and organic matters which can form azeotropy with water are removed in advance, so that the COD value of the process discharge wastewater is obviously reduced, and the long-term requirement on the green production process is met.

5) The top of the catalytic rectifying tower is sprayed with water, so that the separation efficiency is further improved, and the conversion rate is improved.

Drawings

FIG. 1 is a flow diagram of an integrated process for the preparation of methyl t-butyl ether and isobutylene from t-butanol and methanol,

the system comprises a rectifying tower 1, a catalytic rectifying tower 2, a heat exchanger 3, an oil-water separation tank 4, a rectifying device 5, crude tert-butyl alcohol 6, light components 7, heavy components 8, refined tert-butyl alcohol 9, a tower top extract 10, water 11, a water layer 12, a gas phase part 13 of isobutene, a fine methyl tert-butyl ether 14, an organic layer 15, a tower bottom extract 16, methanol 17, water 18 and a reflux opening 19.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that various changes or modifications can be made by those skilled in the art after reading the disclosure of the present invention, and such equivalents also fall within the scope of the invention.

Examples

And (3) the crude tertiary butanol 6 passes through a rectifying tower 1, the tower bottom temperature is 135 ℃, the tower pressure is 0.07MPa, and light components 7 and heavy components 8 are removed to obtain refined tertiary butanol 9 with the mass content of not less than 95.5%, wherein the mass content of organic impurities is not more than 0.1%.

Purified refined tertiary butanol 9 enters a catalytic reaction section of a catalytic rectifying tower 2, the number of theoretical plates of the catalytic rectifying tower 2 is 16, the temperature of the bottom of the tower is 120 ℃, the pressure of the tower is 0.3MPa, methanol (the mass content is not lower than 99.8%) 17 enters the top of the catalytic rectifying tower 2 through a reflux opening 19, the molar ratio of the tertiary butanol to the methanol is 8:5, and water 18 enters the top of the catalytic rectifying tower 2 through the reflux opening 19.

Wherein, the catalytic reaction section has 6 beds, and the feed inlet has 7, is respectively arranged on each bed and the first column plate. The feed position is at the penultimate feed inlet. In addition, the temperature of the catalytic reaction section of the catalytic distillation tower is 100-110 ℃; the pressure is 300-310 kPa.

The catalyst is Amberlyst 15. Dehydrating a part of tertiary butyl alcohol entering from the catalytic reaction section to generate isobutene, and continuously reacting the other part of tertiary butyl alcohol and the isobutene with methanol fed from the top of the tower to generate methyl tertiary butyl ether;

the composition and the component weight percentage content of the tower top extract 10 are as follows: 44.6 wt% of isobutene, 41.6 wt% of MTBE, 1.5 wt% of water, 10.2 wt% of methanol, 1.9 wt% of tert-butanol and 0.2 wt% of others.

The bottom of the catalytic rectifying tower is extracted as water 11, and the total content of organic matters in the water is not higher than 0.01 percent, namely COD is lower than 1000.

Wherein, the product 10 at the top of the tower is condensed by a heat exchanger 3 to obtain a gas phase part of isobutene 13, the mass content of the obtained isobutene is not less than 97 percent, and the obtained isobutene is purified to obtain polymerization grade isobutene with the mass content of not less than 99.9 percent and can be used for producing butyl rubber.

After being condensed by a heat exchanger 3, the obtained liquid phase part is subjected to oil-water separation in an oil-water separation tank 4, and an organic layer 15 is mainly a crude MTBE product; the main components and composition of the water layer 12 are water 60%, methanol 30%, t-butanol 6% and MTBE 4%, and the water layer 12 is refluxed to the top of the catalytic distillation column 2 through a reflux port 19.

Wherein, a rectifying device 5 for further purifying the MTBE crude product obtained by separation is arranged behind the oil-water separation tank, the MTBE crude product enters the rectifying device 5 for purification, the temperature at the bottom of the tower is 110 ℃, the pressure of the tower is 0.2MPa, the extracted product at the top of the tower is fine methyl tert-butyl ether 14, and the content of the MTBE extracted at the top of the tower is not lower than 98 percent; the compositions of the material 16 extracted from the tower bottom are water, methanol and tertiary butanol, and the material 16 extracted from the tower bottom returns to the top of the catalytic rectifying tower 2 through a reflux port 19.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An integrated method for preparing methyl tert-butyl ether and isobutene from tert-butyl alcohol and methanol is carried out in a device comprising a catalytic rectifying tower, wherein the catalytic rectifying tower comprises a catalytic reaction section positioned in the middle, the tert-butyl alcohol enters the catalytic rectifying tower from the catalytic reaction section, and the methanol and water enter the catalytic rectifying tower from the top of the catalytic rectifying tower; wherein the water entering the catalytic distillation tower from the top of the catalytic distillation tower is newly introduced water or circulating water collected after reaction, and the weight ratio of the water added to the top of the catalytic distillation tower to the tertiary butanol is 1 (10-40);

in the catalytic reaction section, one part of tertiary butyl alcohol is dehydrated to generate isobutene, and the other part of tertiary butyl alcohol and the isobutene respectively continue to react with methanol fed from the top of the catalytic rectifying tower to generate methyl tertiary butyl ether;

wherein the tert-butyl alcohol is pretreated, and the feeding molar ratio of the tert-butyl alcohol to the methanol is 10: 1-10: 5; the pretreatment is to purify the tertiary butanol, the purification is extractive distillation, the tertiary butanol before feeding is purified by a rectifying tower to obtain refined tertiary butanol with the mass content of not less than 95.5%, and the mass content of organic impurities capable of forming azeotropy with water is not more than 0.1%;

the extract at the top of the catalytic distillation tower comprises isobutene which does not react with methanol, generated methyl tert-butyl ether, unreacted tert-butyl alcohol, methanol and a small amount of water; the bottom extracted material of the catalytic rectifying tower is basically water, and the highest COD of the water extracted from the bottom of the catalytic rectifying tower is not more than 2000;

the components of the produced substance at the top of the catalytic rectifying tower in percentage by weight comprise: 15-65 wt% of isobutene, 30-70 wt% of methyl tert-butyl ether and 5-15 wt% of methanol.

2. The method according to claim 1, wherein the feed molar ratio of tert-butanol to methanol is 10:1 to 10: 2.

3. The method as claimed in claim 1, wherein the weight ratio of the water added to the top of the catalytic distillation tower to the tertiary butanol is 1 (20-30).

4. The method of claim 1, wherein the overhead product of the catalytic distillation column is separated to obtain isobutylene and methyl tertiary butyl ether.

5. The method as claimed in claim 4, wherein the polymer grade isobutene with the content of not less than 99.9 percent and the methyl tert-butyl ether with the content of not less than 98 percent are respectively obtained after the products at the top of the catalytic distillation tower are further separated and purified.

6. The method as claimed in claim 4, wherein the water, methanol, tert-butanol or any mixture thereof obtained after further separation and purification of the top product of the catalytic distillation column is returned to the catalytic distillation column.

7. The method according to any one of claims 1 to 6, wherein the bottom temperature of the catalytic distillation column is 110 to 150 ℃ and the column pressure of the catalytic distillation column is 0.1 to 0.5 MPa.

8. The method according to claim 7, wherein the bottom temperature of the catalytic distillation column is 120 ℃ and the pressure of the catalytic distillation column is 0.3 MPa.

9. The method according to any one of claims 1 to 6, wherein the temperature of the catalytic reaction section of the catalytic distillation column is between 90 ℃ and 120 ℃; the pressure is 300-310 kPa.

10. The method as claimed in claim 9, wherein the temperature of the catalytic reaction section of the catalytic distillation column is 100-110 ℃.

11. The method according to any one of claims 1 to 6, wherein the subsequent reaction is carried out using purified tert-butyl alcohol, and the COD of the water extracted from the bottom of the catalytic distillation column is less than 1000.

12. The method according to any one of claims 1 to 6, wherein the catalytic distillation column comprises a rectifying section and a stripping section which are respectively positioned at the upper part and the lower part of the catalytic reaction section in addition to the catalytic reaction section, wherein the rectifying section and the stripping section adopt a packed column structure or a plate column structure.

13. The process of claim 12, wherein the rectification section and the stripping section are of a plate column structure, and the number of theoretical plates is about 15 to 17.

14. The process of any one of claims 1 to 6, wherein the catalytic reaction section is packed with a catalyst, the catalyst being a cationic resin catalyst.

15. The process of claim 14 wherein the catalytic reaction zone has 4 to 10 beds and 5 to 11 feed ports, one on each bed and on the first tray, with the feed being at the penultimate feed port.

16. The method of claim 14, wherein the catalyst is a sulfonic acid resin catalyst and the sulfonic acid resin catalyst is Amberlyst 15, Amberlyst35, or Amberlyst 70.

17. The method according to claim 12, wherein the rectifying section and the stripping section of the catalytic rectifying tower are filled with packing, and the packing is theta-ring and/or glass packing.

18. The method of claim 17, wherein the filler is prepared by wrapping DNW-II temperature-resistant resin catalyst in a stainless steel net and arranging the stainless steel net and the windowing flow-guiding corrugated plate at intervals.

19. The process of claim 17, wherein the packing is structured packing, and the catalyst particles are wrapped in a titanium mesh and formed into sheets, each sheet being sandwiched between two corrugated sheets of titanium.

20. The method according to claim 4, characterized in that the gas phase isobutene obtained by condensation of the catalytic distillation column overhead is separated and purified by a static separation unit, wherein the static separation unit comprises an oil-water separation tank for separating methyl tert-butyl ether from the rest of the catalytic distillation column overhead.

21. The process according to claim 20, wherein the mass content of the gaseous isobutene obtained is not less than 97%.

22. The method as claimed in claim 20, wherein the organic layer in the miscella comprises methyl t-butyl ether as a main component; the water layer in the oil-water separating tank contains water, methanol, tert-butyl alcohol and methyl tert-butyl ether as main components.

23. The method as set forth in claim 22, wherein the water layer is separated and returned to the top of the catalytic distillation column for recycling.

24. The method as claimed in claim 20, wherein the oil-water separation tank is followed by a distillation column for further purifying the separated methyl tert-butyl ether.

25. The process according to claim 20, wherein the organic layer containing methyl tert-butyl ether is separated and sent to a subsequent rectification apparatus for further purification.

26. The method according to claim 24, wherein the rectification column for purifying methyl tert-butyl ether has the following rectification conditions: 1) the temperature range of the bottom of the rectifying tower is 100 ℃ to 120 ℃, and 2) the pressure range of the rectifying tower is 0.1MPa to 0.3 MPa; the extract at the top of the rectifying tower is methyl tert-butyl ether, and the extract at the bottom of the rectifying tower is water, methanol, tert-butyl alcohol or any combination thereof.

27. The method of claim 26, wherein the water, methanol, tert-butanol or any combination thereof recovered from the bottom of the rectification column is returned to the top of the catalytic rectification column for recycling.