WO2019206324A1

WO2019206324A1 - Combined method for preparing methyl tert-butyl ether and isobutylene from tert-butyl alcohol and methanol

Info

Publication number: WO2019206324A1
Application number: PCT/CN2019/084749
Authority: WO
Inventors: 朱德权; 代俊明; 马敏; 解淑民
Original assignee: 信汇科技有限公司
Priority date: 2018-04-28
Filing date: 2019-04-28
Publication date: 2019-10-31
Also published as: CN108774100B; CN108774100A

Abstract

A combined method for preparing methyl tert-butyl ether and isobutylene from tert-butyl alcohol and methanol. The method is carried out in a device comprising a catalytic rectification tower. The catalytic rectification tower comprises a catalytic reaction section located at the middle part, tert-butyl alcohol enters the catalytic rectification tower from the catalytic reaction section, and methanol and water enter the catalytic rectification tower from the tower top. In the catalytic reaction section, a part of tert-butyl alcohol is dehydrated to generate isobutylene, and the other part of tert-butyl alcohol and the isobutylene are respectively further reacted with methanol fed from the tower top to generate methyl tert-butyl ether, wherein the tert-butyl alcohol is pretreated, and the molar feeding ratio of tert-butyl alcohol to methanol is 10:1 to 10:9. The combined process combines reaction and separation, promotes the rightward reaction, enables preparation of isobutylene by means of tert-butyl alcohol dehydration and synthesis of MTBE in "one-pot process", greatly simplifies the operation procedure, lowers the process cost and facilitates implementation, and improves the raw material conversion rate overall.

Description

Combined method for preparing methyl tert-butyl ether and isobutylene from tert-butanol and methanol

This application claims the patent application No. 201810403251.2 submitted to the State Intellectual Property Office of China on April 28, 2018. The invention is entitled "A Combined Method for Preparation of Methyl Tert-Butyl Ether and Isobutene from Tert-Butyl Alcohol and Methanol". priority. The entire contents of this prior application are incorporated herein by reference.

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 isobutylene by using t-butanol and methanol.

Background technique

Methyl tert-butyl ether and isobutylene are important C ₄ raw materials, mainly separated and reacted from refinery, pyrolysis of ethylene and mixed carbon 4 produced by coal to olefins.

After mixing C _{4 to} extract the butadiene, the boiling point of isobutylene and butene-1 is only 0.6 ° C in the remaining mixture, which is difficult to separate by rectification. Usually, methanol is added to make isobutylene to form methyl unterminated. Separation of the butyl ether method. Methyl tert-butyl ether is liquid at normal temperature and pressure, and is convenient to transport. Most of it is used for oil adjustment. A small part of it is cracked in situ to form isobutylene for the synthesis of butyl rubber, polyisobutylene and methacrylate. Raw materials and fine chemicals.

In order to obtain high-purity isobutylene for the synthesis of products such as butyl rubber, it is usually prepared by two methods: methyl t-butyl ether cleavage or t-butanol dehydration. For example, CN201410670660.0 discloses a method for preparing high-purity isobutylene by dehydration of t-butanol.

No. 5,741,953 describes a process for the synthesis of methyl tert-butyl ether by the reaction of t-butanol with methanol. The process uses water as the extractant. The process consists of two reactors in series and one catalytic distillation column. Since the azeotropy of t-butanol and water is not considered, the total conversion of t-butanol can only reach 84. %.

No. 5,744, 652 discloses a process for the preparation of methyl tert-butyl ether from the reaction of tert-butanol with 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 step by step, not only because the azeotropy problem affects the total conversion of t-butanol, but also increases the reaction process and increases the economic cost.

CN201310257316.4 describes a process for the complete conversion of tert-butanol and methanol to methyl tert-butyl ether. The process uses ethylene glycol or octanol as an extractant to avoid azeotropy of tert-butanol and water. However, an extraction tower and two extractant recovery towers have been added to the process, and the equipment is complicated and the investment cost is large.

In the disclosed art, an excess of methanol is reacted with t-butanol to produce methyl tert-butyl ether, which requires methanol recycle, and multiple reactors are required to consume excess methanol, thereby increasing energy consumption.

Therefore, a new production process is needed to reduce the energy load caused by excess methanol, increase the reaction conversion efficiency and significantly reduce the organic matter content of the wastewater.

Summary of the invention

The object of the present invention is to provide a combined method for preparing methyl tert-butyl ether and isobutylene by using t-butanol and methanol with simple operation flow, low energy consumption and high conversion rate.

The present invention achieves the above objects by the following technical solutions:

A combined process for the preparation of methyl tert-butyl ether and isobutylene from tert-butanol and methanol, the process being carried out in a plant comprising a catalytic rectification column comprising a catalytic reaction zone in the middle, tert-butanol (TBA) enters the catalytic rectification column from the catalytic reaction section, and methanol and water enter the catalytic rectification column from the top of the column;

In the catalytic reaction section, a part of t-butanol is dehydrated to form isobutylene, and another part of t-butanol and the isobutylene are respectively reacted with methanol fed from the top to form methyl tert-butyl ether (MTBE);

Wherein the tert-butanol is pretreated, and the molar ratio of tert-butanol to methanol is from 10:1 to 10:9.

In an embodiment of the invention, the feed molar ratio of tert-butanol to methanol is from 10:1 to 10:5, preferably from 10:1 to 10:2.

In an embodiment of the invention, the weight ratio of water to t-butanol added at the top of the column is 1: (10-40), preferably 1: (20-30), for example 1:20, 1:22, 1 : 24, 1:26, 1:28, 1:30.

In an embodiment of the invention, an excess of tert-butanol and methanol form isobutene and methyl tert-butyl ether under the action of a catalyst.

According to the present invention, the overhead product comprises isobutene which is not reacted with methanol, the resulting methyl tert-butyl ether and unreacted tert-butanol, methanol and a small amount of water; the bottoms are substantially water. Preferably, the overhead product is separated to provide isobutylene and methyl tert-butyl ether.

Preferably, the composition of the overhead product and the weight percent of the components include: 15-65% by weight of isobutylene, 30-70% by weight of MTBE, and 5-15% by weight of methanol.

In some preferred embodiments, the overhead product can be further separated and purified to obtain polymerized grade isobutylene in a weight percentage of not less than 99.9% and methyl tert-butyl group in an amount of not less than 98% by weight. ether.

Preferably, the overhead product further comprises some light impurity components, such as acetone.

In some preferred embodiments, the overhead product obtained by further separation and purification is returned to the catalytic rectification column as water, methanol, tert-butanol or any mixture thereof.

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

In some embodiments of the invention, the temperature of the catalytic reaction zone of the catalytic rectification column is from 90 to 120 ° C, preferably from 100 to 110 ° C; and the pressure is from 300 to 310 kPa.

Applicant's research has found that when preparing methyl tert-butyl ether in the prior art, the tert-butyl alcohol as a raw material is mostly an upstream reaction product without further purification, which contains a large amount of organic impurities, some of which are organic with water. It is easy to form azeotrope. The use of such tert-butyl alcohol to prepare methyl tert-butyl ether tends to produce a large amount of sewage with a high chemical oxygen demand (COD) value, and direct discharge seriously affects the ecological environment; if the sewage is treated, the treatment procedure is complicated and increases. Economic costs. Thus in some embodiments of the invention, the starting tert-butanol may be pretreated prior to feeding. For example, the tert-butanol is purified. The pre-feeding tert-butanol can be purified, such as extractive rectification, etc., using purification methods conventionally used in the art. In some preferred embodiments of the present invention, the pre-feeding tert-butanol is purified by a rectification column to obtain a purified tert-butyl alcohol having a weight percentage of not less than 95.5%, which can form an azeotrope with water. The weight percentage of organic impurities is not more than 0.1%.

In some embodiments of the present invention, the purified t-butanol is used for the subsequent reaction, that is, the reaction of the purified tert-butanol and methanol is used to prepare methyl tert-butyl ether and isobutylene, and the water produced by the bottom of the distillation column is the highest. More than 2000 mg/L, preferably less than 1000 mg/L.

Moreover, the inventors have found through experiments that the COD produced by the bottom of the column does not exceed 15000 mg/L or even more than 20,000 mg/L unless it is purified before the reaction.

To increase separation efficiency, in some embodiments of the invention, water is added to the top of the catalytic rectification column. The make-up water may be newly introduced water or recycled water collected after the reaction. After adding water from the top of the column, 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, depending on the downstream product requirements.

In the combined process of the present invention, the catalytic rectification column can use a catalytic rectification column conventionally used in the art, such as CN202342929, which describes the specific configuration and features of some conventional catalytic rectification columns.

In some preferred embodiments of the invention, the catalytic rectification column of the present invention includes, in addition to the catalytic reaction section, a rectifying section and a stripping section, respectively located at an upper portion and a lower portion of the catalytic reaction section. Wherein, the rectifying section and the stripping section may adopt a packed tower structure or a plate tower structure, and the present invention preferably adopts a plate type tower structure. More preferably, the theoretical number of plates is about 15-17 blocks. If the number of theoretical plates is too low, the separation effect may be poor. On the one hand, the COD of the sewage in the tower is exceeded, and the amount of tert-butyl alcohol is wasted on the other hand, resulting in high single consumption. If the number of theoretical boards is too high, investment and energy consumption will be too high.

According to the invention, in the catalytic rectification column, the catalytic reaction section is a central portion packed with a catalyst.

The catalytic reaction section has from 4 to 10 (preferably 6) beds, and the feed port has 5 to 11 (preferably 7), respectively on each bed and on the first tray. The lower the feed position, the lower the reaction bed temperature. The current feed position is preferably at the penultimate feed port.

In some embodiments of the invention, the catalyst may be the catalyst of patent US 4,144,138. For example, it is a cationic resin catalyst.

In some preferred embodiments, the catalyst is a sulfonic acid resin catalyst such as Amberlyst 15, Amberlyst 35, Amberlyst 70, etc., preferably Amberlyst 15.

In some embodiments of the invention, the rectification section and the stripping section of the catalytic rectification column may be packed with a filler, such as a θ-ring and/or a glass filler.

In some embodiments of the present invention, the filler is encapsulated in a stainless steel mesh by a DNW-II temperature resistant resin catalyst (manufacturer such as Dandong Mingzhu Specialty Resin Co., Ltd.), and then spaced apart from the window-opening corrugated plate. And made.

Preferably, the filler is a structured packing, and the catalyst particles are wrapped in a titanium mesh to form a sheet, and each piece is sandwiched between two pieces of titanium corrugated sheets. Specifically, the description of this is made in the patent CN205340190.

In some embodiments of the present invention, the overhead product is condensed to obtain a gas phase isobutylene, which is separated and purified by a static separation unit comprising a separation unit for separating methyl tert-butyl ether and the remaining overhead product. Oil and water separation tank.

In some embodiments of the invention, the resulting vapor phase isobutylene is present in an amount of not less than 97% by weight.

In some embodiments of the present invention, the main component of the organic layer in the oil-water separation tank is methyl tert-butyl ether; the main components of the water layer in the oil-water separation tank are water, methanol, tert-butanol and methyl tert-butyl ether; Preferably, the aqueous layer is separated and returned to the top of the catalytic distillation column for recycling.

Preferably, the oil-water separation tank is further provided with a rectification apparatus for further purifying the separated methyl tert-butyl ether.

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

The rectification apparatus for further purifying methyl tert-butyl ether after the oil-water separation tank may be a rectification 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 bottom temperature range is from 100 ° C to 120 ° C, preferably 110 ° C, and 2) the column pressure range is 0.1 MPa to 0.3 MPa, preferably 0.2 MPa; the overhead product is methyl tert-butyl ether, and the bottom product may be water, methanol, tert-butanol or any combination thereof. Further preferably, the above water, methanol, tert-butanol or any combination thereof is returned to the top of the catalytic distillation column for recycling.

The beneficial effects of the invention:

1) The combined process of the present invention mainly converts excess t-butanol into isobutylene, and can simultaneously produce isobutylene and methyl tert-butyl ether. In the production, the feed ratio can be conveniently adjusted according to the actual demand of the product. The product can be controlled.

2) The combined process of the present invention combines the reaction with the separation to promote the reaction to the right, dehydrating the t-butanol to prepare the synthesis of isobutylene and MTBE in a "one-pot" process, which greatly simplifies the operation process and reduces the process cost. Easy to implement and overall increase raw material conversion rate.

3) The use of methanol, which is rarely used in the industry, is lower than the amount of t-butanol, so that the amount of unreacted methanol in the process is greatly reduced, the subsequent separation steps and difficulty are reduced, and the energy consumption can be further reduced while further improving. Methanol conversion rate; also overcome the azeotropy of tert-butanol and water.

4) Using the raw material t-butanol pretreatment process, the organic matter capable of forming azeotrope with water is removed in advance, so that the COD value of the process discharge wastewater is significantly reduced, which is in line with the long-term demand for the green production process.

5) The top of the catalytic distillation column is sprayed with water to further improve the separation efficiency and increase the conversion rate.

DRAWINGS

1 is a flow chart showing a joint process for preparing methyl tert-butyl ether and isobutylene from t-butanol and methanol,

Among them, 1 rectification tower, 2 catalytic rectification tower, 3 heat exchangers, 4 oil water separation tanks, 5 rectification equipment, 6 crude t-butanol, 7 light components, 8 heavy components, 9 fine t-butanol, 10 The top of the tower, 11 water, 12 water layer, 13 gas phase partial isobutylene, 14 boutique methyl tert-butyl ether, 15 organic layer, 16 bottom material, 17 methanol, 18 water, 19 reflux.

detailed description

The invention is further illustrated below in conjunction with specific embodiments. It is to be understood that the examples are merely illustrative of the invention and are not intended to limit the scope of the invention. In addition, it is to be understood that various modifications and changes may be made to the present invention without departing from the scope of the invention.

Example 1

The crude t-butanol 6 passes through the rectification column 1, the bottom temperature is 135 ° C, the column pressure is 0.07 MPa, and the light component 7 and the heavy component 8 are removed to obtain a fine t-butanol 9 having a weight percentage of not less than 95.5%. The weight percentage of organic impurities is not more than 0.1%.

The purified fine t-butanol 9 enters the catalytic reaction section of the catalytic rectification column 2, the theoretical number of plates of the catalytic rectification column 2 is 16, the bottom temperature is 120 ° C, the column pressure is 0.3 MPa, and the methanol (weight percentage) Not less than 99.8%) 17 enters the top of the catalytic rectification column 2 through the reflux port 19, the molar ratio of t-butanol to methanol is 8:5, and the water 18 enters the top of the catalytic rectification column 2 through the reflux port 19.

Among them, there are 6 beds in the catalytic reaction section and 7 feed ports, respectively on the respective bed layers and on the first tray. The feed position is at the penultimate feed port. Further, the temperature of the catalytic reaction section of the catalytic rectification column is 100 to 110 ° C; and the pressure is 300 to 310 kPa.

The catalyst is Amberlyst 15. A portion of the tert-butanol entering from the autocatalytic reaction zone is dehydrated to form isobutylene, and another portion of the t-butanol and the isobutylene are separately reacted with methanol fed from the top to form methyl tert-butyl ether;

The composition of the overhead product 10 and the weight percent of the components were: isobutylene 44.6 wt%, MTBE 41.6 wt%, water 1.5 wt%, methanol 10.2 wt%, tert-butanol 1.9 wt%, and other 0.2 wt%.

The bottom of the catalytic distillation tower is produced as water 11, and the total content of organic matter in the water is not more than 0.01%, that is, the COD is less than 1000 mg/L.

Wherein, the overhead product 10 is condensed by the heat exchanger 3 to obtain a gas phase component isobutylene 13, and the obtained gas phase isobutylene has a weight percentage of not less than 97%, and is purified to obtain a weight percentage of not less than 99.9%. The polymerization grade isobutylene can be used in the production of butyl rubber.

After being condensed by the heat exchanger 3, the obtained liquid phase component is separated in the oil-water separation tank 4 by oil-water separation, and the organic layer 15 is mainly crude MTBE; the main component and composition of the water layer 12 is 60% of water, 30% of methanol, and uncle Butanol 6% and MTBE 4%, and the aqueous layer 12 is refluxed through the reflux port 19 to the top of the catalytic rectification column 2.

The oil-water separation tank is further provided with a rectification equipment 5 for further purifying the separated MTBE crude product, and the crude MTBE is purified into the rectification equipment 5, the bottom temperature is 110 ° C, the tower pressure is 0.2 MPa, and the top of the tower is produced. The product is a fine methyl tert-butyl ether 14, the content of MTBE produced at the top of the tower is not less than 98%; the composition of the bottom material 16 is water, methanol, tert-butanol, and the material of the bottom is 16 The return port 19 is returned to the top of the catalytic rectification column 2.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

A combined process for the preparation of methyl tert-butyl ether and isobutylene from tert-butanol and methanol, the process being carried out in a plant comprising a catalytic rectification column comprising a catalytic reaction zone in the middle, tert-butanol From the catalytic reaction section into the catalytic rectification column, methanol and water enter the catalytic rectification column from the top of the column;

In the catalytic reaction section, a part of t-butanol is dehydrated to form isobutylene, and another part of t-butanol and the isobutylene are respectively reacted with methanol fed from the top to form methyl tert-butyl ether;

Wherein the tert-butanol is pretreated, and the molar ratio of tert-butanol to methanol is from 10:1 to 10:9.
The method of claim 1 wherein the feed molar ratio of t-butanol to methanol is from 10:1 to 10:5, preferably from 10:1 to 10:2.

Preferably, the weight ratio of water to tert-butanol added at the top is 1: (10-40), preferably 1: (20-30), for example 1:20, 1:22, 1:24, 1 :26, 1:28, 1:30.
The method according to claim 1 or 2, wherein the overhead product comprises isobutylene which is not reacted with methanol, methyl tert-butyl ether formed and unreacted tert-butanol, methanol and a small amount of water; The bottoms are basically water. Preferably, the overhead product is separated to provide isobutylene and methyl tert-butyl ether.

Preferably, the composition of the overhead product and the weight percent of the components include: 15-65 wt% of isobutylene, 30-70 wt% of methyl tert-butyl ether, and 5-15 wt% of methanol.

Preferably, after further separation and purification, the overhead product can obtain, respectively, polymerized grade isobutylene in a weight percentage of not less than 99.9% and methyl tert-butyl ether in a weight percentage of not less than 98%.

Preferably, the water, methanol, tert-butanol or any mixture thereof obtained by further separation and purification of the overhead product is returned to the catalytic rectification column.
Process according to any one of claims 1-3, characterized in that the bottom temperature of the catalytic rectification column is from 110 to 150 ° C, preferably 120 ° C, and the column pressure is from 0.1 to 0.5 MPa, preferably 0.3 MPa.

Preferably, the temperature of the catalytic reaction section of the catalytic rectification column is from 90 to 120 ° C, preferably from 100 to 110 ° C; and the pressure is from 300 to 310 kPa.
The method according to any one of claims 1 to 4, wherein the pretreatment is purification of the tert-butanol. For example, extractive distillation.

Preferably, the pre-feeding tert-butanol is purified by a rectification column to obtain a purified tert-butyl alcohol having a weight percentage of not less than 95.5%, wherein the weight percentage of organic impurities capable of forming azeotrope with water Not higher than 0.1%.

Preferably, the subsequent reaction is carried out using purified tert-butanol, and the water produced by the bottom of the catalytic distillation column has a COD of not more than 2000 mg/L, preferably less than 1000 mg/L.

Preferably, the water entering the catalytic rectification column from the top of the column may be newly introduced water or recycled water collected after the reaction.
The method according to any one of claims 1 to 5, wherein the catalytic rectification column comprises, in addition to the catalytic reaction section, a rectifying section and a stripping section, respectively located at an upper portion of the catalytic reaction section And the lower part, wherein the rectifying section and the stripping section may adopt a packed tower structure or a plate tower structure, and preferably a plate type tower structure. More preferably, the theoretical number of plates is about 15-17 blocks.

Preferably, the catalytic reaction section is packed with a catalyst.

Preferably, the catalytic reaction zone has from 4 to 10 (preferably 6) beds and the feed ports are from 5 to 11 (preferably seven) on the respective bed layers and on the first tray.

Preferably, the feed location is at the penultimate feed port.

Preferably, the catalyst is a cationic resin catalyst.

Preferably, the catalyst is a sulfonic acid resin catalyst such as Amberlyst 15, Amberlyst 35, Amberlyst 70, preferably Amberlyst 15.
Process according to any of claims 1-6, characterized in that the rectifying section and the stripping section of the catalytic rectification column are filled with a filler, such as a θ-ring and/or a glass filler.

Preferably, the filler is prepared by wrapping a DNW-II temperature-resistant resin catalyst in a stainless steel mesh and then arranging it with a window-opening corrugated plate.

Preferably, the filler is a structured packing, and the catalyst particles are wrapped in a titanium mesh to form a sheet, and each piece is sandwiched between two pieces of titanium corrugated sheets.
The method according to any one of claims 1 to 7, wherein the overhead product is condensed to obtain a gas phase isobutylene, and then separated and purified by a static separation unit, wherein the static separation unit comprises a separation medium for methyl tertidine. An oil-water separation tank for the ether and the remaining overhead product.

Preferably, the obtained gas phase isobutylene has a weight percentage of not less than 97%.

Preferably, the main component of the organic layer in the oil-water separation tank is methyl tert-butyl ether; the main components of the water layer in the oil-water separation tank are water, methanol, tert-butanol and methyl tert-butyl ether;

Preferably, the aqueous layer is separated and returned to the top of the catalytic distillation column for recycling.
The method according to any one of claims 1-8, characterized in that the oil-water separation tank is further provided with a rectification column for further purifying the separated methyl tert-butyl ether.

Preferably, the above organic layer containing methyl tert-butyl ether is separated and sent to a subsequent rectification apparatus for further purification.
The method according to claim 9, wherein the rectification apparatus for purifying methyl tert-butyl ether has the following rectification conditions: 1) the bottom temperature ranges from 100 ° C to 120 ° C, preferably 110 ° C, 2) The column pressure ranges from 0.1 MPa to 0.3 MPa, preferably 0.2 MPa; the overhead product is methyl tert-butyl ether, and the bottom product is water, methanol, tert-butanol or any combination thereof.

Preferably, the bottoms produced water, methanol, tert-butanol or any combination thereof is returned to the top of the catalytic distillation column for recycle.