JPH0355466B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved process for the production of mercaptans starting from olefinic compounds by reaction of the olefinic compounds with hydrogen sulfide. More particularly, the present invention relates to a novel class of initiators which allow the reaction to proceed under ultraviolet radiation. Since various mercaptans have many industrial uses, much research has been conducted on methods for producing these mercaptans. One method of production which yields industrially interesting results consists in the direct action of ethylene-based compounds with hydrogen sulfide under ultraviolet radiation. In carrying out this process, promoters are usually present in the reaction medium, especially as described in US Pat.
Phosphite organic ester is added as described in 3052452. By utilizing short wavelength ultraviolet radiation
SH radicals are generated photochemically, resulting in the addition of H ₂ S to the double bonds of ethylene-based compounds, but some drawbacks also occur. That is, in practice it is necessary to use particularly pure and transparent reactants and solvents, whereas hydrogen sulfide has weak light transmission in the reactor due to its extremely high molecular extinction coefficient, and The mercaptan itself absorbs ultraviolet radiation, with the result that the reaction is significantly delayed and proceeds only to a small extent, and sulfur is formed by addition of the mercaptan itself to the double bond of the ethylene compound. Several proposals have been made to improve this production method, and photoinitiators or photosensitizers that can be excited in a longer wavelength range have been discovered. That is,
In the method described in US Pat. No. 4,052,283, organic photosensitizers containing one or two carbonyl substituents are used. On the other hand, US Pat. No. 4,140,604 describes a reaction activator composed of an acetophenone derivative. An even more important advance has been made with the method described in French Patent No. 2,424,907. That is, this method provides a better yield and allows use of a wider wavelength range. In this method, an organic derivative of an element of group V _A of the periodic table is added as a promoter to the usual reaction medium, and at the same time benzophenone and/or thiobenzophenone,
Alternatively, an initiator consisting of one or more derivatives of these aryl ketones is used. These ketones can be used alone as photochemical accelerators and give better results than other known additives. As a result, as described in U.S. Pat. No. 3,050,452, it has become possible to advantageously produce mercaptans that could not be obtained using, for example, trialkyl phosphites or triaryl phosphites alone. Ta. Also, according to this US patent, it was necessary to use ultraviolet light with a wavelength shorter than 300 mm, but it became possible to use wavelengths longer than 300 mm by using benzo or thiobenzophenone. Thus, by using benzophenones and/or thiobenzophenones together with phosphites or other organic derivatives of Group V _A elements of the periodic table, the results were significantly improved. The present invention provides a significant improvement over all these known production methods and significantly increases the yield of mercaptan production starting from olefinic compounds. The invention has the advantage that it can be practiced without or in solvents such as organic sulfides, hydrocarbons, or ethers. When an organic sulfide is used, there is a particularly significant advantage in that the sulfide obtained as a by-product of the reaction itself can be used. The novel method for the production of mercaptans according to the invention consists in the production of unsaturated compounds and _H2S under the influence of ultraviolet radiation.
It is characterized in that it contains in the reaction medium a derivative of the xanthene type which acts as an initiator for the production of mercaptans starting from. The xanthenes according to the invention are >C=O or >C
It corresponds to the following formula () composed of a compound consisting of two benzene rings connected by a =S bridge. However, in formula (), Y is O or S, and
are O, _S , _-CH2- , _-CH2CH2- , CO.
The preferred wavelength range is 300-400 mm. The conversion rate of olefinic compounds to mercaptans is determined by the periodic table _V
If an organic compound of a group element is added, the value will further increase. A small amount of the disclosing agent is sufficient, and the xanthene derivative exhibits a cooperative effect with the Group V _A organic compound. While alkyl or aryl phosphites and phosphines, in particular, are currently commonly used due to their commercial availability, xanthene type additives according to the present invention are suitable for bismuth,
It is possible to use corresponding organic compounds of arsenic or antimony, such as alkyl arsenites, aryl arsenites, or alkylardines or arylardines being suitable as additives. These xanthene-type derivatives enhance the initiator effect of known initiators, especially the phosphites mentioned above, and reduce the inhibitory effect that sulfides formed by secondary reactions have on the formation of the desired mercaptan. Restrict. This latter effect allows the present invention to simultaneously produce mercaptans and sulfides, which is extremely useful in some cases. The proportion of xanthene derivatives added to the reaction medium according to the invention depends on various factors, in particular the properties of the reactants to be treated, their concentration in the medium, the presence or absence of a solvent, etc. These proportions are most often of the order of 0.0001-0.10 mol/reaction medium, especially 0.0003-0.10 mol/reaction medium.
A range of 0.001 mol/reaction medium is preferred. Chapter V _A
The proportions of compounds of group elements are of similar magnitude. When it comes to operating conditions, especially temperature and
The H ₂ S/olefin ratio is the same as in the corresponding technology already known from known publications. Therefore, although they will not be described in detail here, the preferred H ₂ S/olefin molar ratio is about 2 to
It should only be noted that at 10, the temperature is kept between -10°C and +20°C. -10℃～-5℃
A temperature range of +20°C to +35°C is usable but not convenient. Although the reaction can be carried out at atmospheric pressure, 3-
Preferably it is carried out under a gage pressure of 30 bar. Regarding the properties of olefins whose conversion to mercaptans is improved by the process of the invention, reference may be made to the following non-limiting examples. Ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene,
1-hexene, 1-heptene, 1-octene, 1
-decene, 1-undecene, 1-dodecene, 1-
Tetradecene, 1-hexadecene, 1-octadecene, 1-icosene, 1-isopentene, 4-
Methyl-1-pentene, 3,6-dimethyl-1-
Heptene, 4-methyl-5-butyl-4-decene, 1,4-diphenyl-2-butene, 3-cyclohexyl-6-icosene, 4-methyl-2-
Pentene, 2,4,4-trimethyl-2-pentene, cyclopentene, 2,5-diethylcyclopentene, cyclohexene, 3-ethylcyclohexene, cycloheptene, cyclooctene, 4-vinylcyclohexene, acrylic acid, methacrylic acid, crotonic acid, allyl Alkyl esters such as acetic acid (pentenoic acid), octenoic acid, undecenoic acid, dodecenoic acid, and octadecenoic acid. The ester here specifically comprises _C1 - _C30 alkyl, more particularly _C1 - _C8 alkyl. The olefin compound can contain multiple double bonds, such as butadiene and 2,4-hexadiene. The process of the invention applies equally to unsaturated compounds bearing substituents such as halides, hydroxyl, alkoxy, carboxyl groups, etc., allyl chloride, allyl alcohol, alkyl or aryl esters of maleic or fumaric acid and similar compounds. It can also be applied to compounds such as. Unsaturated triple bond compounds can also be used in the process of the invention, particularly in the case of alkynes such as acetylene, resulting in vinyl mercaptans. Particularly useful compounds according to the invention include compounds in which the positions of X and Y in formula () are as follows:

Reference may be made to the benzene ring derivatives of these compounds, especially the alkyl, alkoxyl or halogen derivatives. As mentioned above, the central ring of _the xanthene ring contains 6 or 7 elements, the latter corresponding when X is _-CH2CH2- . If Y here is oxygen, the compound is dibenzosuberone, which is produced in liquid form and is therefore easy to handle and readily available. Similarly, Y is sulfur and X is -
This also applies to thiodibenzosuberone in CH ₂ CH ₂ −. A notable advantage of the initiator according to the invention is that, if necessary, it can be used under atmospheric pressure. Under such conditions, the rate of conversion of olefins and the formation of mercaptans per hour are inferior compared to under pressure of several bars, but compared to known organic phosphorous esters alone or acetophenones used under the same conditions. is clearly more effective than the initiator. The absence of secondary products other than the corresponding sulfides facilitates the separation of the mercaptans formed and the recycling of olefins and hydrogen sulfide. The invention will be illustrated based on the following non-limiting examples. Examples 1, 2 and Comparative Examples 1-3 Reactions were carried out in a cylindrical 245 ml stainless steel reactor coaxially equipped with a quartz tube containing an ultraviolet lamp. The maximum UV emission of this lamp is
It corresponded to a wavelength of 350mm. Cooling and stirring of the reaction medium was carried out by an external circuit consisting of a circulation pump and an exchanger, maintaining the temperature of the reaction medium at approximately 10°C. A series of tests were conducted while keeping the following parameters constant. Hydrogen sulfide feed rate: 240/h, 1-dodecene feed rate: 336 g/h, pressure: 12 bar The detailed conditions of each test and the results obtained are shown in Table 1 below.

[Table] Example 3 and Comparative Example 4 Using the reactor described in Examples 1 and 2, 120
/h of hydrogen sulfide and 60/h of propylene were fed continuously in gaseous form under a pressure of 8-10 bar, and in liquid form 100 ml of dimethyl ether of diethylene glycol were added. The concentration of the photoinitiator corresponds to an optimum for the intensity of UV radiation absorbed in the reactor. The temperature of the reaction medium was maintained at approximately 0°C. The results of various tests conducted under these conditions are shown in Table 2 below.

Table: Examples 4-6 and Comparative Example 5 Benzophenone or thioxanthone was used with phosphite under the same conditions as in Example 3 and Comparative Example 5. The amount of phosphite used is
The amount of benzophenone was 33× ^{10 −4} mol/h, and the amount of thioxanthone was 1×10 ⁻⁴ mol/h. The test results are shown in Table 3 below.

[Table] Example 7 Using the same apparatus as in Examples 4 to 6, using thioxanthone in the same manner, the apparatus was heated at a temperature of about -3°C and 90°C.
A pressure of ~10 bar was used. Continuously supply 100 ml/h of dipropylsulfide and 10×10 ^-4 mol/h of tributyl phosphite, and similarly in gaseous form.
120/h of hydrogen sulfide and 60/h of propylene were fed. A propylene conversion rate of 74.8% and a yield of n-propyl mercaptan of 70.3 g/h were obtained. In a second test conducted under the same conditions except that the hydrogen sulfide feed rate was 300/h, a propylene conversion rate of 76.9% and an amount of n-propyl mercaptan produced of 93.7 g/h were obtained. Example 8 and Comparative Example 7 Two tests were conducted using the same apparatus as in the previous example and keeping the following parameters constant. Hydrogen sulfide feed rate 275/h 1-octene feed rate 257 g/h Temperature 0°C Pressure 9 bar The detailed conditions of each test and the results obtained are shown in Table 4 below.

Table Comparable results were obtained for other olefins, namely ethylene, 1-butene, 1-hexene and cyclohexene. Example 9 and Comparative Example 8 In a reactor similar to the previous example, 225 cm ³ of methylal, 75 ^{cm 3} of dibutyl maleate, 6×10 ⁻³ mol of bezophenone, and 3.5×10 ⁻³ mol of tributylphosphine, and introduced 80% hydrogen sulfide. After irradiating the mixture for 4 hours, the reaction mixture was analyzed. Next, add benzophenone 2x
A second test was carried out under the same conditions with substitution of 10 ^-4 moles of thioxant. The reaction was carried out in the same manner. Table 5 below shows the conversion of maleic acid and the yield of diptyl mercaptosuccinate formed by the reaction described below.

[Table] Examples 10 to 13 and Comparative Example 9 Using the apparatus and operating conditions of Examples 1 and 2, dibenzosuberone (in the above formula (), X is -
Dodecyltorcaptan was produced using _CH2CH2- , when Y is oxygen) and thiodibenzosuberone (when X is as above and Y is S) as _an initiator. The results are shown in Table 6 below.

[Table] From this Table 6, it can be seen that dibenzosuberone, like all the xanthene derivatives of the previous examples, shows better results than the known initiators despite being added in significantly lower amounts. That is clear. Examples 14-18 and Comparative Examples 10, 11 A photochemical Pyrex reactor with coaxial lamps submerged in the reaction liquid is already known and provides good dispersion of hydrogen sulfide and propylene gas. A glass inlet tube is provided at the bottom to ensure safety. The radial volume is 90ml. The reactor was thermostatted by means of an external double jacket, operated batchwise under atmospheric conditions, and the gas introduction was kept constant throughout the entire experiment. i.e. hydrogen sulfide 30/h and propylene
30/h. The solvent was diethyl ether of diethylene glycol, saturated with hydrogen sulfide and propylene at a temperature of 10°C. The concentration of photosensitizer corresponds to the optimum for the absorbed intensity in the reactor. The light source is a low pressure mercury lamp with an emission center at 350 mm. The power consumption of this lamp was 8 watts. The amount of mercaptan produced and the propylene conversion after 30 minutes are shown in Table 7 below.

Table 7 It is clear from the results in Table 7 that the initiator according to the invention has the advantage of carrying out the reaction under atmospheric pressure and without using an excess of hydrogen sulfide relative to the olefin.

Claims (1)

[Scope of Claims] 1. An improved method for producing mercaptans by a photoinitiation reaction, which comprises photochemically reacting an olefin compound and hydrogen sulfide in the presence of an initiator represented by the following formula (). However, in formula (), Y is O or S, and
are O, _S , _-CH2- , _-CH2CH2- , CO.