SYNTHESIS OF ISOPROPYL, ISOAMYL ALCOHOLS BASED ON NATURAL GAS PROCESSING PRODUCTS

ABSTRACT

The article describes the method of obtaining isopropyl and isoamyl alcohol from ethylene on the base of telomerization reaction. The composition of the obtained product was determined by liquid chromatography.

АННОТАЦИЯ

В статье описан способ получения изопропилового и изоамилового спирта из этилена на основе реакции теломеризации. Состав полученного продукта определяли жидкостной хроматографией.

Keywords: methyl alcohol, ethylene, isopropanol, isoamyl alcohol, temperature, pressure, catalyst, telomerization reaction.

Ключевые слова: метиловый спирт, этилен, изопропанол, изоамилового спирт, температура, давление, катализатор, реакция теломеризации.

Introduction. Synthesis of ethylene-based aliphatic alcohols is important. The fact that the starting materials used are derived from local raw materials increases the cost-effectiveness of the process. Alcohols are used as solvents raw materials in the manufacture of medicines and in the production of esters. Isoamyl acetate is used in the chemical industry as a solvent for nitrocellulose varnishes, bee pheromone, to test the performance of respirators. Other esters of isoamyl alcohol are also widely used in industry, as a plasticizers in the production of polyvinyl chloride and acetylcellulose.

Methods. There are various methods of synthesis of aliphatic alcohols, and acidic hydration of alkenes is one of the first classical methods for the production of alcohols. The general mechanism of the process is given below [1]:

The regrouping of carbocations in the reactions of secondary alkenes often leads to formation of a mixture of products, what makes it difficult to produce secondary alcohols from them:

In laboratory practice the method of acid hydration is limited by relative difficulty of separating the product mixture, as well as low yield. Most often, this method is used in the production of tertiary alcohols, but even in this case, the yield usually does not exceed 40-45% [2]:

In addition to the liquid phase hydration method of alkenes, the direct gas phase hydration method is also used in industry. Phosphoric acid is used as a catalyst on a solid carrier process has been carried out at 200-300 ° C and pressure 2-8 MPa, and at this the yield of alcohols reaches 95% [3, 4, 5].

Study method. Homogeneous-catalytic methods, gas treatment methods, liquid chromatography, IR-spectroscopy, physicochemical methods were used in the research. The production of isopropyl and isoamyl alcohols as a result of the telomerization reaction of ethylene in the presence of methanol was studied. The process was mainly carried out at 60⁰C, pressure of 1.0 - 5.0 MPa and a duration of 4 h [6, 7].

The discussion of the results

The production of isopropyl and isoamyl alcohols during of the telomerization of ethylene in the presence of methanol was studied. The process was mainly carried out at temperature of 60⁰C, pressure of 1.0 - 5.0 MPa and reaction duration of 4 h. The telomerization reaction takes place in the presence of methanol and ethylene on the basis of the following steps:

CH₃−OH + CH₂=CH₂→ C₃H₇OH  C₅H₁₁OH

The method of synthesis involves the telomerization of ethylene with methanol in the presence of a radical initiator at high temperature and pressure [8, 9, 10].

The process was then stopped and the reaction mixture was cooled to room temperature using an aqueous cooling system. The resulting product mixture was purified by the driving method, the structure of the synthesized substances was proved using IR and chromato-mass spectral analyzes, some their physical constants were determined.

In the IR spectrum of the synthesized propanol-2, the broad and intense valence vibration signal of the hydroxyl group characteristic of hydrogen bonds is in the 3334 sm^-1 region, while the deformation vibration signal of the carbon-bonded hydroxyl group (С-OH) is in the 950 sm^-1 region, methyl (CH₃). asymmetric valence oscillation of the group with high intensity in the area of ​​2969 sm^-1, asymmetric deformation vibration signal in the area of ​​1466 sm^-1, asymmetric deformation vibration of carbon with hydrogen in the area of ​​high intensity in the area of ​​1466 sm^-1, symmetrical deformation vibration signal in the area of ​​1378 sm^-1, carbon the asymmetric valence oscillation of hydrogen showed absorption in the 2932-2960 sm^-1 area with high intensity, while the symmetrical valence oscillation signal showed an absorption in the 2883 sm^-1 area, 1160 sm^-1 and 816 sm^-1 for the -C(CH₃)₂ group. The presence of C-O group-specific absorption lines was observed at 1128 and 668 sm^-1. 

Figure 1. IR spectrum of propanol-2

In the chromato-mass spectrum of propanol-2 the formation of ion corresponding to its molecular mass and the mass of fragmented ions formed from its decomposition were determined (Fig. 2).

Figure 2. Chromato-mass spectrum of propanol-2

Through 1,806 min in the spectrum a molecular ion of propanol-2 was formed, which is 60.0 . In turn, the release of 45 ions from the propanol-2 ion in 1,806 minutes from the release of the -C₂H₅-O radical, 27 ions from the C₂H₃ radical, 29 ions from the C₂H₅ radical, 31 ions from the CH₂OH radical, the separation of 43 ions from the C₃H₇ radical and 59 ions from the C₃H₇O radical has been observed.

Figure 3. Raman spectrum of propanol-2

Figure 4. IR spectrum of isoamyl alcohol

Figure 5.  Raman spectrum of isoamyl alcohol

Figure 6. Chromato-mass spectrum of isoamyl alcohol

The synthesis process was carried out in a high-pressure resistant hermetic reactor. The composition of the reaction mixture was determined by liquid chromatography (Fig 7.).

Figure 7. Liquid chromatogram of ethylene telomeration reaction products in the presence of methanol

Table 1.

The composition and amount of the reaction product

Conclusion. The analysis of the results has shown that the main products of the telomeration reaction of ethylene in the presence of methanol are isopropyl and isoamyl alcohols, as well as acetaldehyde, methylacetate, ethyl acetate, butanol, isobutanol, propanols.

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