DE1168878B - Process for the purification of methanol, which is contaminated with higher acetylenes and aromatic compounds - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C 07 c

Number:
File number:
Registration date:
Display day:

German class: 12 ο-5/01

M 55160 IVb / 12 ο December 17, 1962 April 30, 1964

The present invention relates to a process for the purification of methanol contaminated with higher acetylenes and aromatic compounds. The impurities mentioned are absorbed by methanol when it is used as a cold-resistant medium or as a solvent for the treatment of acetylenic gases produced from liquid or gaseous hydrocarbons by any cracking process. Processes of this type are, for example, those of the "partial combustion" of the hydrocarbon with O ₂ under atmospheric or superatmospheric pressure; then "regeneration" type processes; furthermore, the methods of the electric type and methods of the "hot smoke" type.

It is known that in the processes mentioned, higher acetylenes, diolefins, aromatic compounds are always formed as highly undesirable by-products, in addition to relatively large amounts of other gases (for example H ₂ , CO, CH ₄ ).

Is the production of acetylene from the said mixture of gases (acetylenic gases) or the final purification of the acetylene already separated from the acetylenic gases by means of Solvents carried out at temperatures below 0 ° C, it is necessary in most cases that a cold-resistant liquid is injected into the gaseous streams to be cooled. The said Liquid is generally a water-mixing process for purifying methanol, which is contaminated with higher acetylenes and aromatic compounds

Applicant:

Montecatini Societa Generale per l'Industria Mineraria e Chimica, Milan (Italy) Representative:

Dipl.-Ing. Dipl.-Chem. Dr. phil. Dr. techn. J. Reitstötter and Dr.-Ing. W. Bunte, patent attorneys, Munich 15, Haydnstr. 5

Named as inventor:

Vittore Boem,

Walter BiUi, Milan (Italy)

Claimed priority:

Italy of December 22, 1961 (23 110)

and higher acetylenes), the mixing is carried out in the stream of the extracting gas.

Any combustible gas or an inert gas (such as N ₂ , CO ₂ ) usable solvent, which can be used in the application, can be used as the extracting gas. In some cases it is advantageous not to freeze temperatures and the gases do not use the same gaseous hydrocarbon, react; for example, methanol, ethanol, which is used to obtain acetylene from cracking, acetone, etc., is specially supplied for the stated purpose. The extracting gas must not be suitable. Oxygen (maximum 1%) or strong in water or

Apart from the fact that methanol _{absorbs the gases (such as NH 3} ) or substances, gases which are generally soluble in methanol, it is absorbed by some with acetylene compounds or with others

Contaminants (such as CS ₂ ) can react. A combustible gas is used when the acetylenes or aromatic compounds obtained are to be used as fuel; an inert gas is used when the whole is vented to the atmosphere. The methanol to be purified is mixed with water in such a ratio that afterwards a mixture mixing with water and direct introduction will hold in 45, which does not purify a water component from a gas stream in the atomized state. less than 50 percent by weight, preferably about 65%, the addition of water promotes the entire removal. Before mixing, the water is used to wash the higher acetylenes and aromatic compounds of the extracting gas from the higher fertilizers, which in this way pass quickly from the liquid acetylenes and to obtain the methanol state into the gaseous phase, without any vapor. Polymerize the scheme of FIG. To bring the oily layer to a minimum is an embodiment of the present VerMinimum (formed by driving aromatics.

409 587/488

higher acetylenes, diolefins, aromatic compounds are saturated and must be recovered and reuse in the process are subjected to purification.

The same need exists when using methanol as a solvent for higher acetylenes and aromatic compounds is used.

According to the invention, methanol is

The impure methanol coming from the plant, in which it is used as a solvent gas to column 2, depends on the temperature and the pressure with which it works, depends on the temperature and pressure with which it works, as well as on the quality and quantity the impurities also present in to a _t for the recovery of the dissolved C ₂ H _{2 and cleaning methanol therein C., H 4} by means of expansion and extraction 5 gene and from the dimensions of the extraction column 2 with gas b into the column 1. The methanol off. In general, it is advantageous with feeds then through a ₂ into the mixer 6, where there is extracted gas of not less than 0.8 Nm with the _{CH 3} OH to be purified per kilogram coming from the column 3 through d work. Water is intimately mixed. "The column operates under a pressure of 0.4

The mixture is preferably added dropwise in io to 1.5 abs. atm and preferably below atmospheric column 2 introduced through which a gaseous pressure. The working temperature is in the current flowing upwards, which is fed to the column by means of between -20 and + 50 ° C. and preferably to line C ₁ . The mixture leaves at about + 25 ° C.

finally the bottom of column 2 as H ₂ O- The column 3 is preferably a bottom

CH ₃ OH solution, which is free of higher acetylenes 15 column. The columns 2 and 3 can be more advantageous and aromatic compounds and which can be combined into a single apparatus via the line a ₃ by means of the pump 12 and given, as shown in FIG. 2 is indicated. if the filter 11 of the distillation column 7 is pulled the scheme of FIG. 1 can be run through a wash. tower for CH ₃ OH vapors emitted from the

The extraction gas, which is separated from the water by distillation, is entrained by methanol, which is entrained in the column 1, will in turn be completed as a solvent or cold; Durable medium is used for washing. The recirculated part of the water fed to the column 3 is used via d _{1 of} the column 3 or part of the already extracted metha recovery from the extraction gas together with the nol-water solution, depending on the temperature of the higher Acetylenes and aromatic compounds 25 washing gases.

entrained CH ₃ OH vapors supplied. A part In the event that the extraction of the cold content of the

the water is removed when the impure methanol in the circuit is to be carried out, run with the impure methanol α and the extraction can be present in higher amounts of impure methanol and purified methanol through a heat exchange between ionic gases b and c than those which are achieved together with an exchanger arranged directly next to the mixer 6 cleaned methanol A and gases B and C. The said kick. Extraction can take place without the risk of decomposition

The column 1 is preferably empty or is carried out with relatively high acetylenes, if these are used homely Raschig rings or shards, in amounts below 30 percent by weight in methanol around any retention zones of liquid, which means that 35 is present at a heating temperature of + 20 ° C to avoid polymerization being promoted; are.

the said column is usually with an example

Conical atomizer of a commercial type equipped. This column works on the basis of the un- 10 000 Nm ^{3 of} acetylenic gases, produced by the stability of the higher acetylenes with relatively 40 partial combustion of CH ₄ with O ₂ , compressed high temperature and partial pressures preferably to 10 atm and freed _{from CO 2 by washing,} in the cold and under atmospheric pressure. Are from +20 to - cooled 8O ⁰ C for recovery of C ₂ H ₂ and C ₂ H ₄ readily occurs even this temperature, the recovery of the C ₂ H ₂ durchbei low temperatures; moreover leads to feed. During the cooling process, 500 kg of the extracting gas d are injected into the gas due to the high solubility of 45 98% CH _{3 OH.} This difference in strength between the higher acetylenes methanol absorbs water, aromatic compounds (highly soluble) and C ₂ H ₂ , C ₂ H ₄ (less soluble) in fertilizers and a good part of the higher acetylenes methanol and leaves relatively small amounts of high and high methanol The system is in an impure state with ren acetylenes and can therefore be fed to the system -80 ° C for direct purification to acetylene recovery. Turn 50.

The column 2 can be empty, however, the composition of the individual streams is on

to put them in an empty part at the top and in one of the various places in the system is indicated in the table below with broken pieces or ordinary Raschig; to subdivide the listed symrings filled part. The filling will bole refer to Fi g. 1. Chosen in such a way that residence zones of the liquids, 55 The purification begins in the empty column 1, which favor a polymerization, and in which the impure methanol expands on atmospheric retention of the polymers formed in the case of pressure and with 40 Nm ³ "synthesis gas" b abnormal experimental conditions is reduced to a minimum from the plant for treating the acetylenic. Such irregularities gases at the temperature of + 20 ° C could be extracted, for example, in the event of a water shortage 60 will. The degassed acetylene is circulated again at the mixer 6 or at the extraction gas to the column 2 and recovered.

enter; in such cases, the polymers are the column 1 leaving ^{at - 20 0 C-}

held back by the filter 11, which with normal ethanol is not activated by means of the pump 4, the mixer-decomposition conditions. sprayer 6 fed under a pressure of 2 kg / cm ² . The mixer 6 is a normal mixer-atomizer 65. The pump 5 feeds the same mixer for liquids (for example of the KSM type of 2 kg / cm ² the water d ₂ , which is in column 3 Lechler Co.), which the two Contains methanol absorbed by liquid jets. The two streams combined outside the nozzle. The feed of the extra- are mixed and injected into the colon 2,

which is half empty and half filled with broken glass. In this column, the accomplished gas coming c at a slightly higher than atmospheric pressure, pressure, the total distance the higher acetylenes and aromatic compounds from the methanol from the "fractionation" of the freed from C ₂ H ₂ acetylenic gases This gas is after prior extraction of the CHjOH vapors in column 3 subsequently used as fuel in a steam plant.

A water-methanol solution a _{s flows} from column 2 and is fed to the distillation in column 7; the solution has a proportion of acetylenes below 3 ppm. In the column mentioned, methanol with about 98% purity is obtained from the top of the column and water with 99% purity from the bottom with a steam consumption of 800 kg.

42 kg of water d _x , which was introduced into the process partly with the impure methanol and partly with the extraction gas c, are emptied from the system. The overall yield of the CH ₈ OH recovery is 97.8%. This yield can be increased to ίο 99.4% by also recovering the CH ₃ OH vapors which are carried along with the gas b ₂ by washing, for example with part of the solution a, and which are then carried along with d _{2 of} the Column 2 is fed.

composition

of the currents
(based on Fig. 1)

"1 kg kg «4 H H Nm ' it kg 0.2 kg Nm ' Nm ' Nm » 16.4 0.3 14.0 4.2 0.2 0.3 0.0 0.2 176.0 4.2 0.5 0.0 11.9 12.4 13.0 176.0 0.0 0.0 27.2 27.5 202 13.0 0.1 1.4 0.1 0.2 202 2.1 32 0.4 0.8 33.4 30th 0.6 14.0 30.6 56.5 0.1 7th 57 0.0 0.0 10 16.2 0.1 481.0 489.5 0.8 0.9 10 490.0 28.2 960.0 479.1 6.2 45 1.0 28.2 629.6 1449.5 10.0 450.2 15.0 658.7 489.1 40.0 62.5 459.4

German
kg

C ₂ H ₂

C ₂ H ₄

CO

H ₂

CH ₄

Acetylenes with more than

3 carbon atoms
and all

Acetylenes with more than

4 carbon atoms

Acetylenes with more than
4 carbon atoms

Aromatics

Other gases (NO ₂ + O ₂
etc.)

CH ₃ OH

H ₂ O

Total

Claims (3)

Patent claims: 1. Process for the purification of methanol, which with higher acetylenes and aromatic Compounds is contaminated by mixing with water and extracting the aqueous solution with a stream of inert gas, characterized in that mixing with Water at a temperature between -20 and + 50 ° C, preferably at about 25 ° C, and at a pressure between 0.4 and 1.5 abs. atm, and preferably under atmospheric pressure im Stream of the extracting gas is carried out in order to create a nebulized mixture with a water 45 10.0
908
918.0 content not to be obtained below 50 percent by weight, and that extraction is carried out in countercurrent carried out, removing the higher acetylenes and aromatic compounds. 2. The method according to claim 1, characterized in that an extracting gas combustible, oxygen-free gas is used. 3. The method according to claim 1 and 2, characterized in that as extraction columns, columns, empty or filled with broken glass or ordinary Raschig rings, which are suitable Zones of stagnation of the fluids are to be avoided. 1 sheet of drawings 409 587/488 4.64 © Bundesdruckerei Berlin