JPS63246343A - Purification of higher alcohol - Google Patents

Abstract

PURPOSE:To suppress formation of by-products and purify a higher alcohol, by washing a crude >=6C alcohol with an aqueous solution of an acid and distilling the alcohol optionally in the presence of an acid in purifying the alcohol by distillation. CONSTITUTION:A crude >=6C alcohol, especially 9-20C alcohol is purified by distillation. In the process, the alcohol is washed with an aqueous solution of an acid (particularly aqueous solution of an inorganic acid at pH 3-5, such as sulfuric acid or hydrochloric acid, or aqueous solution of an organic acid having 2-5pKa, such as acetic acid or malic acid) and distilled or the alcohol is distilled in the presence of a high-boiling acid (high-boiling acid without distilling together with the raw material alcohol to contaminate products and corroding metallic materials of distillation stills) to purify the higher alcohol. Higher alcohols obtained by subjecting an alpha-olefin prepared by low polymerization using a Ziegler process or decomposing a wax to hydroformylation and hydrogenation reaction, etc., are preferred as the raw material alcohol.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for purifying higher alcohols.

Specifically, the present invention relates to a method for suppressing the production of by-products when distilling and purifying crude alcohols having 6 or more carbon atoms.

[Conventional technology]

Higher alcohols used as raw materials for plasticizers, detergents, etc. are industrially produced mainly by three methods: the Ziegler method, the oxo method, and the paraffin oxidation method. Among these higher alcohols, those having less than io carbon atoms are mainly used as plasticizer raw materials, and those having more than io carbon atoms are mainly used as detergent raw materials. In the production process of these higher alcohols, separation and purification by distillation is usually performed.

For example, in the case of oxine process alcohols, linear and branched types are separated at the oxo reaction stage depending on the reaction conditions, but usually /:0. It is produced at a ratio in the range of I-/. Although it depends on the application, the linear type is usually in greater demand, so it is common practice to separate the linear type and the branched type by vacuum distillation.

In addition to the above, in the Guerbet process for obtaining branched trimerized alcohols by dehydration condensation of primary alcohols, the produced alcohol is washed with water and then distilled under reduced pressure to separate and obtain the trimerized alcohols. .

[Problem that the invention seeks to solve]

When distilling and refining the above-mentioned Okin method alcohol or trimerized alcohol, etc., especially in the case of higher alcohols having 6 or more carbon atoms, the higher alcohols undergo side reactions during distillation, resulting in by-products such as aldehydes, olefins, and high-boiling point alcohols. There is a problem in that the production of by-products and the like increases significantly, which not only causes a decrease in the purity of the product alcohol, but also significantly reduces the yield.

[Means for Solving the Problems] The present inventors have made extensive studies to solve the problems during distillation of higher alcohols, and have found that the side reactions during distillation are due to trace amounts of impurities in higher alcohols. By bringing the raw material higher alcohol into contact with acid in a specific manner and purifying it by distillation, the effects of the above impurities can be effectively suppressed, and the amount of by-products produced during distillation can be significantly reduced. They discovered this and completed the present invention.

That is, the gist of the present invention is to provide a method for purifying higher alcohols, which is characterized in that, in purifying crude alcohols having a carbon number or more by distillation, the alcohols are washed with an aqueous acid solution or distilled in the presence of an acid; exists in

The present invention will be explained in detail below.

Higher alcohols (hereinafter referred to as
The raw material alcohol) is an alcohol having 6 or more carbon atoms, preferably an alcohol having 3 to 30 carbon atoms, and more preferably an alcohol having 7 to 20 carbon atoms. The origin (manufacturing method) of the raw material alcohol is not particularly limited, and any of Ziegler process alcohol, oxo process alcohol, paraffin oxidation process alcohol, or Guerbet process alcohol can be used. Practically, in particular, alpha-olefins obtained by Ziegler method ethylene low polymerization, or alpha-olefins obtained by wax decomposition, are hydroformylated and hydrogenated to produce oxo-method alcohols, or primary alcohols are treated with alkali or It is suitable to apply the method of the present invention to Guerbet process alcohols, etc., which are obtained by carrying out a dehydration condensation reaction in the presence of an alkali and a co-catalyst, and washing the resulting branched trimerized alcohol with water to remove the catalyst.

In the method of the present invention, raw alcohol is washed with an aqueous acid solution and then distilled, or distilled in the presence of an acid.

As the acid aqueous solution, an inorganic or organic acid aqueous solution is used. As the inorganic acid, strong acids such as sulfuric acid, hydrochloric acid, and nitric acid are usually used. As an inorganic acid aqueous solution, the pH is usually
is 2-6, preferably 3-! are used. The above organic acid usually has a pKa of 1 to 6, preferably λ
~! For example, acetic acid, malic acid, citric acid, etc. are used. It is usually preferable to use an organic acid aqueous solution having a pH in the range of λ to B. If the above pH or pKa is too small, the corrosion of the metal material of the processing equipment will increase, and if it is too large, the acid cleaning effect will be reduced. It may be a continuous type, a semi-continuous type, or a batch type.

The volume ratio of acid aqueous solution/raw alcohol is usually 1), //
The range is 1 to/i, preferably 0.5//P-ra/.

The raw alcohol washed with the acid aqueous solution is then purified by distillation.

In the method of the present invention, the side reactions can be similarly suppressed by distilling the raw alcohol in the presence of an acid. As the nucleic acid, an acid with a high boiling point that does not contaminate the product by distilling out together with the raw alcohol and does not corrode the metal material of the distillation pot can be used.

Distillation is carried out using a distillation column having a number of theoretical plates capable of separating the target components, and by adjusting the degree of vacuum so that the pot temperature is usually 2!0°C or less, preferably 2θ0°C or less.

When the pot temperature is 200° C. or higher, the amount of byproducts (aldehydes, olefins, and high-boiling point byproducts) increases.

〔Example〕

Next, embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Comparative Example / Isostearyl alcohol obtained by dehydration condensation of a linear alcohol with the same number of carbon atoms in the presence of an alkali catalyst was placed in a 300 rttl four-tube flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a sampling port. The water-washed product was charged to /jOrttl, heated to 230'C, and from that point on, sampling was performed successively and changes in the contents of aldehydes, olefins, and high-boiling substances were investigated by gas chromatography analysis.

The results are shown in FIG. 1 as a solid line. Since both increase and decrease exponentially with respect to time, it can be seen that they are linear with respect to the product. In particular, a pattern was shown in which a remarkable increase occurred after r hours of heat treatment, and thereafter it collapsed due to the reaction. In particular, high-boiling substances significantly increase, and it can be seen that the product yield rate decreases if distilled under such conditions.

Example 1 Using the same apparatus as in Comparative Example 1, the same raw material isostearyl alcohol used in Comparative Example 1 was washed with a 0.2% aqueous solution of citric acid at a volume ratio of i/l. The results of an experiment similar to Example 1 are shown in FIG. 1 by broken lines.

It is clear that the production of aldehydes, olefins, and high-boiling substances is suppressed, and the amount of high-boiling substances produced is also small, and the product yield is improved when distillation is carried out under such conditions.

Example 2 Instearyl alcohol synthesized from C, alcohol by Guerbet reaction was washed twice with water to remove the alkali catalyst, and then washed with a citric acid (00S%) aqueous solution at a volume ratio of 1:1. is distilled in a batch distiller equipped with a packed column under the conditions of pressure J (7 WHg).The results of the distillation are shown in Figure 2.
It is in the range of ~210°C.

Comparative Example The results were shown in FIG. 2 under the same conditions as Example 2, but with water washing instead of citric acid washing.

[Effects of the Invention] According to the method of the present invention, higher alcohols can be purified while effectively suppressing the production of byproducts due to side reactions during distillation.

[Brief explanation of drawings]

FIG. 1 shows the results of heat treatment tests in Example 1 and Comparative Example 1. (The impurity concentration on the vertical axis is on a logarithmic scale.) FIG. 2 shows the results of the distillation test in Example C and Comparative Example C. (The impurity concentration on the left vertical axis is on a logarithmic scale.) Patent applicant: Mitsubishi Chemical Industries, Ltd. Agent: Patent attorney: Hase - 1 other person 1 Figure 10 Heat % Rikenma (time) A 2 items ctX, i18 Lee (z)

Claims (4)

[Claims] (1) A method for purifying higher alcohols, which comprises distilling a crude alcohol having 6 or more carbon atoms by washing the alcohol with an aqueous acid solution or in the presence of an acid. (2) A method for purifying a higher alcohol according to claim 1, which comprises washing the alcohol with an aqueous inorganic acid solution having a pH of 2 to 6 and then distilling it. (3) A method for purifying a higher alcohol according to claim 1, characterized in that the alcohol is washed with an aqueous solution of an organic acid having a pKa of 1 to 6 and then distilled. (4) A method for purifying a higher alcohol according to claim 1, which comprises distilling the alcohol in the presence of a high-boiling acid.