CS251990B1 - Process for producing 2-alkoxypropenes - Google Patents

Abstract

2-Alkoxypropenes with 1 to 5 carbon atoms in the alkoxy group are prepared by the reaction of the pyrolysis Cs fraction containing min. 5% by mass methylacetylene and allene with alcohol with 1 to 5 carbon atoms under the catalysis of basic substances (10 to 40% solution of hydroxide, or sodium or potassium alkoxide in alcohol with 1 to 5 carbon atoms J. The reaction takes place at a temperature of 150 to 270 °C and a pressure of 1.0 to 5.0 MPa, while the molar ratio of methylacetylene and allene to alcohol ' is 1:1 to 1:3.

Description

2S1990

The present invention relates to a process for the preparation of 2-alkoxypropenes from a pyrolysis C3-fraction containing methylacetylene and alene. 2-Alkoxypropenes (alkylisopr openyl ethers) are compounds with versatile potential use. They are potentially monomers and monomers in special types of coatings, some as 2-methoxypropene being the desired raw material in organic synthesis (synthesis of vitamins A, E and fragrances).

Conventionally, low-temperature acid is produced from acetone and the corresponding alcohol by catalytic condensation, wherein the alkyloxypropane formed is pyrolyzed in 2-alkoxypropam. The process is two-stage, energy-intensive and the second stage is not too selective. In the discontinuous process, the synthesis of 2-methoxypropene from the enriched methyl acetylene fraction is known [Agre B. A. et al., Chim. Farm. FROM. 17, No. 3, 330 (1983)]. The reaction was also carried out in a gaseous phase on an icointactic catalyst (NaOH in charcoal) [Agre B. A. Neftepererab.Neftechim. 1982, (9) 34). However, the reaction in the gas phase is sensitive to the service life of the heterogeneous catalyst, which is sealed by the polymer surface with the polymeric materials formed by the polymerization of the monomer contained in the pyrolysis C3.

According to the present invention, the preparation of 2-alkoxypropenes is carried out by reacting the pyrolysis Cs-fraction containing methylacetylene and the alene with an alcohol having a carbon number of 1 to 5 by catalysis of the base at a temperature of 150 to 270 ° C, preferably 165 ° C. up to 190 ° C and a pressure of 1.0 to 5.0 MPa, preferably 2.5 to 4.5 MPa, wherein the molar ratio of methylacetylene to alene to alcohol

The synthesis of 2-methoxypropene according to the invention is carried out in a continuous pressure apparatus. The alcohol is metered through pre-heating into a pressure reactor. The liquid C3 fraction fits into the alcohol stream. The two feedstocks are fed to the bottom of the pressurized reactor, which is up to 2/3 to 3/4 of the volume of the catalytic solution, which is a 10-40% solution of alkali hydroxide or alcoholate in the alumina used. kohole. The solution is homogeneous, but there is no problem if part of the hydroxide or alcoholate is precipitated out of the solution. The amount of catalysis solution is a function of the temperature, the pressure of the spray of the respective alcohol and the catalytic mixture. The level is controlled by a drop or appropriate adjustment of the temperature of the deflector fluid. Reaction product vapors containing 10 to 40 ° C of 2-alkoxypropene, the respective alcohol, and C3 vapor fraction are passed through a de-phagemaker which returns a portion of the alcohol to the reactor through the condenser and further to the pressure reservoir. The condensate proceeds further from the pressure reservoir to the separating time.

In addition to the pure methylacetylene and the alene, the pyrolysis Cs-fraction, which contains 20 to 40 wt. % of methylacetylene and propadiene; % propane, 10 to 20 wt. % propylene, about 0.3 wt. % isobutenes, 0.6 wt. butadiene. The composition of the C5-fraction fluctuating according to the type of pyrolysis can be used without any modification. It is possible to use a whole liquor, the condition being that the reaction time is liquid (forming the reaction medium) to dissolve the catalyst, the reacting hydrocarbons (methylacetylene alene) and to have sufficient volatility of the natural conditions. In general, the higher the alcohol used, the lower the pressure.

As a catalyst, 10 to 40% by weight, preferably 25 to 35% by weight of KOH, NaOH, potassium and sodium alcoholates, which are added directly to the alcohol, or the catalytic solution can be added by addition of alkaline metal to the appropriate catalyst. alcohol.

When using alcoholic liquor solutions (which are the cheapest catalysts), it is preferred to add 1 to 5% by weight to the catalyst solution. the alcoholate of the respective metal or other very strong base as the catalyst (diazobicyclooctene, trialkylbenzylammonium hydroxide and other very basic substances). Optimal conversion of the methylacetylene and the alene and the yield of 2-alkoxypropene is not achieved in the flow system until after 8-12 h without the addition of these catalysts. Addition of these substances removes this undesired initial charging time.

The reaction temperature depends on the alcohol used. The lower limit is about 150 ° C, the upper limit being the reactivity of the alcohol and its volatility. Typically, a temperature of 150 ° C to 270 ° C is used, a temperature of 165 ° C to 220 ° C, preferably 165 ° C to 190 ° C, is applicable for the use of methanol.

The reaction pressure also depends on the alcohol used, its volatility and the solubility of hydrocarbons (methylacetylene and alene therein). A pressure of 1.0 to 5.0 MPa is used, and the transfer of methanol is 2.5 to 4.5 MPa.

The raw materials are fed to the reactor in a molar ratio of 1: 1 to 1: 3. More preferred only an excess of alcohol. The advantage of the process is the processing of the secondary raw material, which usually returns to pyrolysis. In the separation process, unreacted hydrocarbons are separated by pressure distillation from the alcohol-2-alkoxy-propene reaction mixture and the hydrocarbons are returned to the pyrolyte. A gaseous reaction mixture containing 20 to 40 wt. 2-alkoxypropene in the corresponding alcohol is conducted for further processing. In the case of 2-methoxypropene, this is isolated by extraction rectification, where water (1% NaOH solution, KOH), glycols, monoethanolamines, etc. is used as the extraction solvent. The process operates with 55% to 65% conversion of methylacetylene and al-251990 5 nu at almost 100% selectivity. Addition of alcohol to propylene does not occur under the reaction conditions. In the product, traces of 2,2'-dialkoxypropane and traces of acetone, 2-Alkoxypropenes were found to be pressure sensitive to polymerization and need to be classically stabilized (e.g., by hydroxyquinone, pyrophateehin, alkylphenols, alkyl). or alkylaryl amines). Inhibitors added to the appropriate alcohol entering the synthesis. They are also sensitive to acidity (they break down into alcohol and acetone), and that's why they're stabilizing! with K2CO3, which adds to the final product.

In contrast to the classical two-stage synthesis of inabase acetone, the synthesis of 2-alkoxypropene according to the invention has several advantages. The process is one-stage and substantially less energy-intensive. The feedstock (C3 - fraction) is substantially less expensive than acetone. The process of the present invention is characterized by superior selectivity and lower entrainment requirements since the reaction mixture does not contain acetone.

The process is continualized and has several other advantages over the known process. The catalytic system is very stagnant, short-lived, and can be continuously exchanged during the reaction. Known heterogeneous catalysts, such as NaOH on activated carbon, are characterized by low activity (low order of magnitude). In addition to the loss of alkalinity, the surface of the catalyst is sealed with polymers.

The invention is exemplified without limiting its subject matter. Example 1

490 ml of the catalytic mixture (30% KOH in methanol) is pumped into the continuous pressure apparatus until the reactor overflows. The nitrogen in the apparatus is adjusted to 4.0 MPa. Methanol is added to the reactor at a rate of 93 ml / h [2.33 molar / preheat preheat which is set at 100 ° C. The methanol is heated at 123.5 g / h with pyrolysis Cs-fraction at the inlet of the reactor. [0.096 ml / h] (contains 31% by weight methylacetylene and alene). C-fraction as follows composition in% by weight: propane 47.8 propylene 19.2 acetylene 0.31 i-butene 0.53 propane diene (alene) 13.4 (pdj butadiene 0.90 methylacetylene 17.6 [why.]

Sum of reactive components = pd + labor. = 31 wt.

The raw materials are fed to the bottom of the reactor, where they are sprayed into the catalytic solution by a loop provided with 40 holes of 6 mm in diameter. The reactor is heated to 185 ° C. Vapors are collected in the upper part of the reactor (some of the vapor is condensed in the deflector), condensed in the condenser and trapped in the pressurized container. Both the C3-fraction and the pressure reservoir are mounted on the scales. The arietok temperature stabilization is carried out over a 1.5 hour run-in period. The actual experiment lasts 8 h. Equalize pressure is made from the pressure bottle d-o pressure bottle also placed in the balance by venting the liquid phase. After 8 hours, a sample of gas and liquid was taken from the pressurized reservoir into pressurized samplers. 216 g / h of product are obtained in a composition by weight: 2-methoxypropene 19.3 methanol 38.6 propane 25.7 propylene 10.22 acetylene 0.25 propadiene 1.48 methylacetylene 4.67

After 8 hours of operation, a yield of 60.5% of 2-methoxypropene was obtained for the charged methyl acetylene and the alene for the conversion of methylation of ethylene and the alene of 61.8%. After degassing of the reaction mixture, the content of 2-methoxypropene in methanol is 33% by weight. Example 2

Following the spraying and reaction procedure, as described in Example 1, a catalytic solution of 30% KOH in methanol is added to which 0.1 g of potassium is added. Even after 8 hours of p-feed, the conversion of methyl acetylene and alene 68% and the yield of 2-methoxypropene 66% to methyl acetylene and alene are achieved. Example 3

Following the feed-in procedure, 25% NaOH in methanol at a reaction temperature of 200 DEG C., 4 bar was used as the catalyst solution. After 8 hours of operation, a 54% conversion of methylacetylene and alene was achieved, and a yield of 51% was applied to the charged methylation and alene. Example 4

Following the procedure and reaction conditions of Example 1 (temperature 185 qC, pressure 4.0 MPa, pre-heating temperature 100 CC (the molar ratio of the feedstock changes. Catalytic solution 30% -HCH with 0, 1 g of potassium.

Claims (2)

SUBJECT Process for the preparation of 2-alkoxypropenes having from 1 to 5 carbon atoms in an alkoxy group, characterized in that the pyrolysis C-fraction containing in total at least 5 wt. methylacetylene and alene are reacted in the liquid phase with a C 1 -C 5 alcohol under catalysis with a base selected from a 10-40% solution of sodium or potassium hydroxide or alkoxide in a C 1 -C 5 alcohol at 150 to 40 ° C; 270 ° C, preferably 165-190 ^q C at 1.0 to 5.0 the invention MPa, preferably 2.5 to 4.5 MPa, wherein the molar ratio of the total amount of methylacetylene and alene to the C 1 -C 5 alcohol is 1: 1 to 1: 3 and the desired product is isolated from the reaction mixture. 2. The process of claim 1, wherein the catalyst used is a 10 to 40% solution of sodium or potassium hydroxide in a C1 to 5 alcohol in which 1 to 5 wt. sodium or potassium. Severography, n. p., plant 7, Most Ceaa 2,40 Kčs