JP3421901B2 - Method for producing dimethyl ether - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention
On the method of producing dimethyl ether using
I do. [0002] 2. Description of the Related Art Synthetic gas containing carbon monoxide and hydrogen as main raw materials.
Technology for the direct synthesis of dimethyl ether from
Is a technology for reacting raw gas by passing it through a fixed bed catalyst layer.
Has been developed (Japanese Patent Laid-Open No. 2-280836,
JP-A-3-8446, etc.). [0003] In addition, catalyst fine particles are mixed in a high boiling medium oil.
The raw material gas is passed through the suspended slurry reactor.
Also develops technology to synthesize dimethyl ether with high yield
(JP-A-2-9833, JP-A-3-5
No. 2835, JP-A-3-181453, JP-A-3-181453
JP-A-4-264046, JP-T5-810069
Gazette). By the way, dimethyl ether is synthesized from synthesis gas.
The reactions for synthesizing (DME) are the three reactions of formulas (1) to (3).
It is composed of [0005]     Methanol synthesis reaction: CO + H_Two→ CH_ThreeOH …………… (1)       Dewatering reaction: 2CH_ThreeOH → CH_ThreeOCH_Three+ H_TwoO …… (2)     Shift reaction: CO + H_TwoO → CO_Two+ H_Two……………… (3) [0006] When (1) to (3) are summarized, it is expressed by equation (4).
DME and CO_TwoGenerates equivalents. 3CO + 3H_Two→ CH_ThreeOCH_Three+ CO_Two…… (4) Equation (4) is an equilibrium reaction governed by temperature and pressure.
And the raw materials CO and H_TwoDoes not convert 100%
No. That is, unreacted CO and H
_TwoIs tens of% (reactor inlet CO, H_TwoCriteria) Exists. Usually, this unreacted CO and H_TwoDo not discard, other
Reacts again as part of the raw material gas
Sent to the vessel. For example, DOE / PC / 90018-T
In Fig. 7, dimethyl ether is produced by the process shown in Fig. 3.
are doing. This production equipment is a reactor R, methanol, water
Separator S1, unreacted gas separator S2 and CO_TwoSeparator S3
Is made up of The raw material gas line 2 is located at the bottom of the reactor R.
Is connected to the source gas line 2 and a new source gas is
(Fresh) gas line 1 that supplies
Unreacted CO and H_TwoRecycle gas supply
7 is connected. Reaction generated from the top of reactor R
Reaction gas line 3 for discharging wastes separates methanol and water
Of the methanol and water separator S1
Methanol / water line 4 reacts at methanol / water outlet
A reaction gas line 5 is connected to the product outlet. Anti
The other end of the reactive gas line 5 is at the inlet of the unreacted gas separator S2.
Connected to the unreacted gas outlet of the unreacted gas separator S2
The other end of the recycle gas line 7 is connected
You. In the middle of this recycled gas line 7,
A purge line 10 for extracting a part is connected. Not yet
DME, CO of reaction gas separator S2_TwoDME at the exit
CO_TwoLine 6 is connected, DME, CO_TwoOther than line 6
End is CO_TwoConnected to the separator S3,_TwoC of the separator S3
O_TwoCO at exit_TwoLine 8 has a DME exit at the DME exit
In 9 are connected respectively. In this process,
First, methanol from the reaction gas, methanol in the water separator S1
And water, and then the unreacted C is separated in the unreacted gas separator S2.
O and H_TwoIs separated and recycled to the reactor R,
The aim is to improve the usage efficiency of fees. [0009] The above-mentioned unreacted gas separation
In the process, tens of kg / cm^Two-20 ℃ under G pressure
Unreacted CO and H in the reaction gas_Two
And CO_TwoAnd product DME. But
However, CO in this way_TwoSeparation efficiency is as low as about 20%
And recycled gas (unreacted CO, H_Two) Is 15% or more
At high concentrations of CO_TwoWill be accompanied. We have 2
80 ° C, 30kg / cm^TwoA reaction experiment was performed under the condition of G,
CO in source gas_TwoInvestigate the relationship between concentration and CO conversion
Was. As a result, as shown in Table 1, CO 2_TwoWith increasing concentration
It was evident that the CO conversion significantly decreased. [0010] [Table 1] The source gas is made up of recycled gas
CO in addition to gas (fresh gas)_TwoThe concentration is
However, since the CO conversion rate still falls,
Purging the recycle gas by about 20%
By doing so, CO in the source gas_TwoAbout 13% concentration
I am holding it down. However, this method does make-up gas
20-30% CO in (fresh gas) and 1
0-15% H_TwoWill be discarded unused.
CO, H_TwoCould not be fully utilized. [0012] Means for Solving the Problems The present inventors have a high CO conversion.
To maintain the conversion rate and increase the efficiency of using the raw material gas
CO in recycled gas_TwoLow concentration, in other words
If the reaction gas is CO_TwoConsider removing enough
did. As this removing means, CO 2_TwoContaining high levels of
Pass the reaction gas through an alkaline solution such as an aqueous sodium hydroxide solution.
And CO_TwoCan be removed by reaction absorption
You. However, this method requires complicated processes and
High cost, operation to recover and reuse alkali
This was not a good idea because of the high cost. There
Thus, the present inventors have determined that CO _TwoDissolution and absorption
We focused on and examined. As a result, CO_TwoDME separated from
Is returned to the unreacted gas separation step (S2) again,
_TwoFrom the reaction gas by utilizing CO as an absorbent_Two
Was found to be able to be efficiently removed. That is, the present invention relates to at least carbon monoxide.
Catalytic reaction of raw material gas containing nitrogen and hydrogen
The monoacid remaining in the reaction product to form ether
To recycle carbonized and hydrogen as raw materials
In this circulated carbon monoxide and hydrogen
A liquid dye that separates carbon dioxide from the reaction product
Contact with tyl ether to absorb and remove it
Related to a method for producing dimethyl ether, characterized by the following:
It is. Mixing of hydrogen and carbon monoxide in source gas
The proportion is H_Two/ CO molar ratio of 0.1 to 20, preferably
Those having a mixing ratio of 0.2 to 5 can be used. Such a field
Examples of coal gas include coal gasification gas and natural gas
Syngas can be mentioned. The dimethyl ether synthesis catalyst includes methanol
Mixed catalyst and methanol dehydration catalyst
And optionally additional water gas shift catalyst.
You. These are used in a mixed state,
The catalyst can be cut off to form a two-stage reaction. Departure
Light is applicable to any of these catalysts. As a methanol synthesis catalyst, there are usually industrial
Copper oxide-zinc oxide used for methanol synthesis, oxidation
Zinc-chromium oxide, copper oxide-zinc oxide / chromium oxide, acid
Copper oxide-zinc oxide / alumina. Methanol dehydration
As the medium, acid-base catalysts such as γ-alumina, silica, silica
Rica-alumina, zeolite and the like. Zeolite
Alkali such as sodium and potassium as metal oxide components
Potassium metal oxides, calcium, magnesium, etc.
Potassium earth oxides and the like. As a water gas shift catalyst
Is copper oxide-zinc oxide, copper oxide-chromium oxide-zinc oxide,
Examples include iron oxide-chromium oxide. Methanol synthesis catalyst
Water gas shift catalyst with strong shift catalytic activity
Can double. Methanol dehydration catalyst and water gas
Alumina-supported copper oxide catalyst also serving as shift catalyst
Can be used. The above-mentioned methanol synthesis catalyst, methanol removal
The mixing ratio of water catalyst and water gas shift catalyst is particularly limited.
Depending on the type of each component or reaction conditions, etc.
Can be selected appropriately, but usually methanol
0.1 to 5 methanol dehydration catalysts per 1 synthesis catalyst
Degree, preferably about 0.2 to 2 and water gas shift
G catalyst is about 0.2-5, preferably about 0.5-3
Is often appropriate. Methanol synthesis catalyst
When the water gas shift catalyst is also used,
The amount of gas shift catalyst is added to the amount of methanol synthesis catalyst.
It is. The catalyst may be a fixed bed type, a fluidized bed type, a slurry
-It can be used for any reaction type
You. In particular, in a slurry bed type reaction, the temperature inside the reactor is uniform.
Low generation of by-products. Below, the slurry bed type reaction is described.
It will be described in detail. In the case of the slurry bed type reaction, the catalyst is in a powder state.
Used, the average particle size is 300 μm or less, preferably 1 to
About 200 μm, particularly preferably about 10 to 150 μm
Is appropriate. For this purpose, pulverize as necessary.
Can be. The medium oil exhibits a liquid state under the reaction conditions.
Any of these can be used. example
Aliphatic, aromatic and alicyclic hydrocarbons, alcohols
, Ethers, esters, ketones and halides,
A mixture of these compounds and the like can be used. In addition, sulfur content
Oil, vacuum gas oil, and hydrotreated coulter
High boiling fraction, Fischer-Tropsch synthetic oil, high boiling
Spotted oils and the like can also be used. The amount of catalyst to be present in the solvent is
It is determined as appropriate depending on the type of solvent, reaction conditions, etc.,
Usually, it is 1 to 50% by weight to the solvent, and 2 to 30% by weight.
% Is preferable. As reaction conditions in a slurry bed reactor
The reaction temperature is preferably 150 to 400 ° C., particularly 25
A range from 0 to 350C is preferred. Reaction temperature is 150 ° C
Lower, or higher than 400 ° C.
Conversion rate decreases. Reaction pressure is 10 to 300 kg / c
m^Two, More preferably 15 to 150 kg / cm^TwoEspecially good
Preferably 20-70kg / cm^TwoIs appropriate. Reaction pressure
Force is 10kg / cm^TwoIf lower, the conversion of carbon monoxide
Low and 300kg / cm^TwoHigher makes the reactor special
And a large amount of energy is
It is important and not economical. Space velocity (per kg of catalyst)
Supply rate of the mixed gas in the standard state of
50,000 l / kg · h is preferred, especially 500 to 30
000 l / kg · h. Space velocity of 50,000 l /
If the pressure is greater than kg · h, the conversion rate of carbon monoxide decreases,
If it is smaller than 100 l / kg · h, the reactor becomes extremely large.
It is not economical. The reaction gas thus obtained contains dimethyl
Ether, carbon dioxide, carbon monoxide, hydrogen, water
And methanol, and other by-products such as methane
Substances and impurities contained in the source gas.
The composition of the reaction gas is about 1 to 40% of dimethyl ether.
Always about 3 to 25%, carbon dioxide about 1 to 40%, usually 3
About 25%, carbon monoxide about 10 to 70%, usually 20
About 50%, hydrogen about 10 to 70%, usually 20 to 50
%, Methanol about 0.2-5%, usually 0.5-3%
Degree, water about 0.05-0.8%, usually 0.1-0.5
%, And about 0-5%. Dimethyl ether is separated from this reaction gas.
Use any difference in condensation temperature or boiling point
Is preferred. When utilizing the condensation temperature difference, the reaction
As the gas cools, methanol and water condense first.
You. This condensate may be used for other purposes, such as water and methanol.
And the methanol may be recycled to the reactor.
Upon further cooling, dimethyl ether condenses,
Unreacted carbon monoxide and hydrogen, which are dissolved carbon oxides
Remains in the gas phase. Minutes of carbon dioxide from dimethyl ether
Separation can be performed by distillation. In the method of the present invention, the above-mentioned unreacted gas is used.
Carbon monoxide and hydrogen_TwoSeparator removes carbon dioxide
Contact the dimethyl ether liquid
Dissolve and remove existing carbon dioxide. Used for that
The unreacted gas separator used is reactive gas and dimethyl ether
That can cool and maintain good contact between them
Any format is acceptable. For example, Shell and Chu
Type heat exchanger with liquid reservoir or liquefied
Tank type in which reaction gas is blown into dimethyl ether
This is one example. This contact causes CO_TwoHas liquefied
Dissolved and absorbed in dimethyl ether. Dimethyl ether
Liquefaction occurs at -25 ° C under normal pressure,
The higher the temperature, the lower the temperature
The liquefaction of methyl ether is easy and CO 2_TwoAlso dissolves
Increase. If the separation temperature is low, CO_TwoSeparation efficiency increases
However, the size of the refrigerator has also increased, and equipment costs have increased.
Bulky. Therefore, the temperature in the unreacted gas separator is 0 to-
70 ° C, particularly preferably -20 to -50 ° C. Also the pressure
Is usually equivalent to the reaction pressure. The amount of dimethyl ether to be recycled is
CO in the reaction gas contacted with dimethyl ether_Twoof
It is 1 to 10 times, preferably 2 to 5 times. [0026]   Flow rate of CO gas supplied to the reactor (Nl / min): Fin (CO)   CO gas flow rate (Nl / min) flowing out of the reactor: Fout (CO)   DME gas flow rate (Nl / min) flowing out of the reactor: Fout (DME)   MeOH gas flow rate (Nl / min) flowing out of the reactor: Fout (MeOH)   Methane gas flow rate (Nl / min) flowing out of the reactor: Fout (CH_Four) Then [0027] (Equation 1) [0028] (Equation 2) [0029] (Equation 3) FIG. 1 shows an example of an apparatus in which the method of the present invention is performed.
It is shown in FIG. This device is similar to the device of FIG._TwoSeparator
The unreacted gas separator S is branched from the DME line 9 of S3.
New DME recycling line 11 for recycling to 2
It is something that was just provided. Unreacted gas separator used in the apparatus of FIG.
FIG. 2 shows an enlarged view of S2. This unreacted gas separator S2
Consists of a vessel with a cooling jacket, and the reaction gas
Line 5, DME, CO at bottom_TwoLine 6, DM on top
E recycling line 11, recycled gas line on top
7 are respectively connected by piping. [0032] 【Example】 Example 1 Bubble tower reactor R (inner diameter 90mm, height 2000mm)
A reaction experiment using the reactor of FIG.
° C, pressure 30kg / cm^TwoG. N in the reactor R
5730 g of hexadecane and 860 g of powdered catalyst
Was added to form a suspension. In step S1, the gas in the reactor outlet gas
Tanol and water (methanol, water line 4), DM in S2
E and CO_TwoPart of the gas (DME, CO_TwoLine 6) Separation
Then, the unreacted gas was purified. The purified unreacted gas is Lisa
Recycle to the reactor inlet through the cycle gas line 7
Was. Make up for the consumed CO gas and hydrogen gas and react
CO gas and hydrogen gas flow rate at the vessel inlet are 30Nl /
And make up of CO gas and hydrogen gas
The flow rate of the gas line 1 was adjusted. In addition, recycled gas
Some of the remaining CO separated in S2_TwoContains gas
But CO at the reactor inlet_TwoGas flow rate is 9Nl / min
The purge amount of the recycle gas was adjusted as described above. Into reactor
By keeping the mouth gas composition constant in this way, CO conversion
The conversion was maintained at 42%. S2 is temperature -30 ° C, pressure 3
0kg / cm^TwoControl with G, CO with S3_TwoRemove
Circulated DME (11) to S2 at 0.5 mol / min
Was. At this time, the purge rate of the recycle gas was 3.8.
%, Make-up amount of CO gas and hydrogen gas
Losses were 5.0% and 3.4%, respectively.
Was. Comparative Example 1 CO at S3_TwoWithout recycling the DME from which
Was performed. At this time, the purge rate of the recycled gas
Is 29.7%, which means that CO gas and hydrogen gas
The losses to the amount of cleanup were 29.1% and 21.
5%. Embodiment 2 Test from line 3 on the container with cooling jacket shown in Fig. 2
Gas (CO_Two: DME: CO: H_Two= 10: 10: 40:
40) at 50 mmol / min and DME from line 11
Introduced at 5 mmol / min. At the same time exhaust gas from line 7
From the line 6 to keep the amount of liquefied DME in the container constant.
The DME was extracted to keep it. Pressure is 50kg / cm
^TwoG. The temperature inside the container was -30 ° C. Recover gas volume
The composition is measured using a gas chromatograph (detection
(TCD). CO in exhaust gas_TwoIs 1.9m
mol / min and CO_TwoThe separation efficiency was 38%. Embodiment 3 The amount of DME introduced from line 11 was 10 mmol / min.
Except for this, the same experiment as in Example 2 was performed. CO in exhaust gas
_TwoIs 2.6 mmol / min and CO 2_Two52% separation efficiency
Met. Embodiment 4 The amount of DME introduced from line 11 is 20 mmol / min.
The same experiment as in Example 2 was performed except for the above. C in exhaust gas
O_TwoIs 4.1 mmol / min and CO 2_TwoThe separation efficiency is 82
%Met. Comparative Example 2 Experiment similar to Example 2 without introducing DME from line 11
Was done. CO in exhaust gas_TwoIs 1.0 mmol / min
, CO_TwoThe separation efficiency was 20%. Embodiment 5 Same as Example 3 except that the inside temperature of the container was set to −40 ° C.
An experiment was performed. CO in exhaust gas_TwoIs 3.1 mmol / min
And CO_TwoThe separation efficiency was 62%. Embodiment 6 Same as Example 3 except that the inside temperature of the container was set to −25 ° C.
An experiment was performed. CO in exhaust gas_TwoIs 2.4 mmol / min
And CO_TwoThe separation efficiency was 48%. [0041] According to the method of the present invention, the recycled gas
CO_TwoConcentration is kept low and CO in the DME synthesis reaction
High conversion can be maintained. Also, the recycling gas par
Requires minimal or no purging
No, CO, H_TwoCan be used effectively. Further, C
O_TwoUsing easily separated product DME as absorbent
And the process is simple.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow sheet of an example of a DME manufacturing apparatus in which a method of the present invention is performed. FIG. 2 is an enlarged view showing a pipe connection position of the unreacted gas separator of FIG. FIG. 3 is a flow sheet of an example of a conventional DME manufacturing apparatus. [Description of Signs] 1 Make-up (fresh) gas line 2 Raw material gas line 3 Reactant gas line 4 Methanol and water line 5 Reactant gas (including DME, CO ₂ ) line 6 DME and CO ₂ line 7 ... recycle gas line 8 ... CO ₂ line 9 ... DME line 10 ... purge line 11 ... DME recycle line R ... reactor S1 ... methanol, water separator S2 ... unreacted gas separator S3 ... CO ₂ separator

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tsutomu Shibata 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-3-181435 (JP, A) JP-A-2 -9833 (JP, A) JP-A-3-52835 (JP, A) JP-A-4-264046 (JP, A) JP-A-57-156041 (JP, A) (58) Fields investigated (Int. . ^7, DB name) C07C 41/01 C07C 41/09 C07C 43/04

Claims (1)

(57) [Claim 1] A dimethyl ether is produced by a catalytic reaction of a raw material gas containing at least carbon monoxide and hydrogen, and carbon monoxide and hydrogen remaining in the reaction product are removed. In a method of circulating and recycling as a raw material, it is required that carbon dioxide entrained in the circulated carbon monoxide and hydrogen is brought into contact with liquid dimethyl ether separated from the reaction product and absorbed and removed therefrom. Characteristic method for producing dimethyl ether