JPS62116556A - Production of alkyl mercaptan - Google Patents

Abstract

PURPOSE:To obtain a compound useful as an odorant for town gas in good yield in a process for providing continuous reaction for a long period at a low equipment cost, by reacting an olefin with hydrogen sulfide in the presence of a high-performance catalyst by a moving bed method. CONSTITUTION:An olefin, e.g. isobutene, is reacted with hydrogen sulfide in a moving bed of an alumina catalyst obtained by preparing spherical gel from a basic sol of aluminum hydroxide, heat-treating the gel at 500-700 deg.C and removing sulfate radicals, etc., and having >=95% alumina content and >=0.8meq/g acidity to afford the aimed substance. If the yield is to be maximized, the reaction is carried out under the following conditions: Blowing gas composition; 20:60:40 nitrogen gas:hydrogen sulfide:isobutene, 80 deg.C temperature and 120hr<-1> space velocity (SV).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing alkyl mercaptans, and more particularly to a method for producing alkyl mercaptans from olefins and hydrogen sulfide using a high-performance alumina catalyst. In particular, it is a simple and useful method for producing tert-butyl mercaptan, which is used as an odorant for city gas.

[Prior Art] As a method for producing alkyl mercaptan, particularly tertiary-butyl mercaptan, Japanese Patent Application Laid-Open No. 51-4860.6 discloses a method for producing tertiary mercaptan by reacting tertiary alcohol and hydrogen sulfide in a liquid phase containing sulfuric acid. Are listed. For example, 0.1 mole of t-butanol and 0 hydrogen sulfide
．． 13 mol under pressure of 1 to 40 Kg/crA, 600
When reacted at 0 to 120°C for 10 to 120 minutes, alcohol conversion rate was 98%, selectivity to mercaptan was 74%,
The selectivity to sulfide was 26%. Furthermore, when isobutene and hydrogen sulfide were reacted under pressure using sulfur-silica-alumina as a catalyst, tert-butyl mercaptan was obtained, but the yield was low.

Japanese Patent Publication No. 53-141209 discloses that a synthetic zeolite catalyst is used to pressurize olefin and hydrogen sulfide (20 to 10
00Psig), a method for producing tertiary mercaptans having 4 to 18 carbon atoms by reaction at a temperature of 50° to 150°C is described.

Special Publication No. 25109 No. N Niha AtFs -B
(, As (7)) It is described that a higher alkyl mercaptan can be obtained in high yield by reacting carbon number 8-18 carbon atoms with hydrogen sulfide in the presence of a mixed catalyst.

JP-A No. 55-9087 discloses that an acetophenone derivative having the following structure is used as a catalyst, and under ultraviolet irradiation, the sulfide core 00R1 R+, Rs; Al Rz; 7 X =-/lz group is alkoxyl. group R
A method is described in which mercaptans are synthesized by reacting hydrogen of an alkyl group of '-n = 1 to 4 with an olefin such as 1 tylene, propylene, isobutene, etc. under pressure (250 to 600 Psig) at a temperature varying from 0 to 700C.

Others R, F, Noyler: J, Chern, 8oc
, 1532 (1947) using sulfur as a catalyst 45a
A method for synthesizing mercaptans is described in which isobutene or cyclohexene is reacted with hydrogen sulfide at 150°C. Also 8.0゜JonesslE, F, Ro
id; J, Chem, 8oc, 2456 (1938)
Then, ethylene, propylene, or isobutene and hydrogen sulfide were sealed in a cylinder using sulfur as a catalyst, and the mixture was heated to 180°C under pressure.
A method for synthesizing mercaptan by reacting with 'O is also described in Landa 8. Weisser; J, Co11ect
ion 0zeck.

OhemCommum 2197 (1957)E 1 gat+n of ethylene or cyclohexane and hydrogen sulfide using molybdenum sulfide or tungsten sulfide as a catalyst
A method for synthesizing mercaptans by reacting at 200° to 250°C is described.

[Problems to be Solved by the Invention] It is known that mercaptans can be obtained as Markawnikoff-type addition products of olefins and hydrogen sulfide. Metal oxides, concentrated sulfuric acid, sulfur, etc. are known as catalysts, but strongly acidic silica-alumina and concentrated sulfuric acid have shown high activity. However, since these reactions are usually carried out under severe conditions under pressure, there are many by-products and the yield is not very high.

Therefore, in order to produce it industrially efficiently, the first challenge is to have a high active vA that can be used at normal pressure and low temperature, and a carbon number of 2.
This is a search for catalysts that can be applied to a wide range of reactions between ~12 olefins and hydrogen sulfide.

Secondly, it is necessary to develop a catalyst preparation method and a regeneration method to further increase the conversion rate and selectivity, and thirdly, it is necessary to establish a continuous production process using such a catalyst.

[Means for Solving the Problems] The reactivity of isobutene and hydrogen sulfide was extensively investigated using activated alumina and silica-alumina catalysts, which are easy to handle, among high-performance catalysts. As a result, when high-purity spherical alumina particles obtained by a specific method are heat-treated at a specific temperature, normal pressure,
We have arrived at the present invention by discovering that even at low temperatures, it shows a very high conversion rate and selectivity to tert-butyl mercaptan.

That is, a spherical gel is prepared from a basic sol of aluminum hydroxide, and heat-treated to synthesize an alkyl mercaptan from an olefin and hydrogen sulfide characterized by having an alumina content of 95% or more and an acidity of 0.81 Q/. A method for preparing the alumina catalyst used, and a method for producing alkyl mercaptan, which is characterized by passing an olefin and hydrogen sulfide through a moving bed of the alumina catalyst thus obtained. The present invention will be explained in detail below.

The basic sol of aluminum hydroxide used in the present invention is, for example, when a base such as sodium hydroxide or sodium carbonate is added to an aqueous solution of aluminum sulfate to make it neutral or alkaline, aluminum hydroxide is generated and the sol is It refers to a liquid that has become a liquid. Furthermore, in order to make particles of a desired shape as a catalyst, for example, a hexamethylenetetramine solution is used.

In addition, it is dropped into water-insoluble oil such as light oil to form spherical particles, which are then separated and dried. It does not include single mechanically formed pieces of aluminum hydroxide or aluminum oxide.

When dried and molded as is by the method described above, it exhibits extremely high catalytic activity, whereas when molded mechanically, no method has been found to impart high activity.

Here, spherical shape does not mean only a geometrically perfect spherical shape (it also includes shapes other than spherical, such as a disk shape, an oblate spheroid, an oval shape, and a crushed sphere shape.

The dried particles then need to be heat treated at a temperature of 5000-7000C. Also, if it contains sulfate roots, remove it by washing with water. Catalyst activity is at a temperature of 800C18V; 120hr-
'Gas composition Nz;:az8;isobutene=20;50
:50 gas was passed through the same reaction tube filled with catalyst to determine the conversion rate and selectivity. As a result, both the conversion rate and the selectivity showed a fairly significant peak in the heat treatment temperature range of 500° to 700°, and the conversion rate in particular showed a sensitive criticality. Looking at the relationship between heat treatment temperature, particle surface area, and average diameter of micropores formed on the surface, particle surface area and catalytic activity show a strong correlation, but the average diameter of micropores hardly changes at treatment temperatures below 7000C. , there is a tendency for it to increase rapidly if the value exceeds that value. In addition, the acidity of the catalyst due to heat treatment is 0 in the range of 500° to 700°C.
．． It shows an extremely high value of 83 to 0.94 field 9/2, and decreases rapidly at lower and higher temperatures. Acidity o, s
The conversion rate is approximately constant within the range of rrJI3q/. Therefore, the catalyst needs to have an acidity of o, s rneq or higher.

Here, the specific surface area was measured using an 8orptomatic 1800 manufactured by Carlo Erbaf (Italy).
The amount of nitrogen adsorption was measured at -196°C. Further, the pore distribution was measured in a radius range of 40 to 360× using a mercury borosiemeter manufactured by Carlo Erba. Acidity was determined by dobutylamine titration.

When the catalyst is prepared by the method described above, the isobutene conversion rate, mercaptan selectivity, and the amount of mercaptan produced per 8T of catalyst used are reduced due to the reduction of the alumina content.
Both Y decreases. As a result of studying systems containing components such as silica in addition to alumina, it was found that when the alumina content becomes 95% or less, the conversion rate gradually decreases, whereas the selectivity decreases rapidly. Therefore, since STY also decreases rapidly when the content is below 95%, the catalyst composition should be 95% alumina.
This is necessary.

When mercaptans are synthesized by reacting olefins with hydrogen sulfide using the catalyst prepared by the method described above,
If the number of carbon atoms is 2 to 6, it will be a gas phase reaction, and if the number of carbon atoms is 7 to 12
In the case of olefins, it is a liquid phase reaction.

In the case of the ultimate phase reaction, a catalytic reaction is carried out by using an inert gas, such as nitrogen gas, as a carrier gas under normal pressure. The carrier gas may be any inert gas, but nitrogen gas is preferred in practice.
% range is suitable.

The appropriate ratio of hydrogen sulfide to olefin is 1.0 to 1.5 when the olefin has 2 to 4 carbon atoms, and about 3rd position when the olefin has 5 or 6 carbon atoms. Under normal pressure, 8V120hr
The optimum temperature under the reaction conditions varies depending on the type of olefin, but a range of 800 to 200'C is suitable. The olefin conversion rate is the lowest for ethylene, at 7-8%, and for propylene, 2-butene, and 1-hexene at 30-50%, but for other olefins with 2-6 carbon atoms, it is 97-100%.
% has been reached.

In addition, the selectivity for 1-butene is about 42%, but the selectivity for the majority of olefins is as high as 95-100%.

In the case of a liquid-phase reaction, a catalyst is placed in a liquid-phase olefin at normal pressure, and hydrogen sulfide is blown into the olefin while stirring to fluidize the catalyst particles. The amount of catalyst is approximately 38% per 100% of olefin.
2, reaction temperature 500-2000C, hydrogen sulfur) if reaction solution 100tnI! ) for n, 1
The reaction was carried out for 4 hours by blowing at 30"/-. The olefin conversion rate was about 20% in the case of propylene tetramer having 12 carbon atoms, and the selectivity was about 87%.

The activity of the catalyst decreases with the passage of time and the conversion rate decreases, but the spent catalyst can be used for about 2 hours at 500'C in air.
Baking restores the activity and allows repeated reuse.

However, gas-phase reactions using fixed beds have the disadvantage that the yield decreases as the catalyst deteriorates, so we investigated a method that uses a moving bed to maintain constant reaction conditions and production amounts. Here, the moving bed is a system in which the fluid is not violently fluidized, but is moved continuously in a substantially laminar flow. According to the moving bed method, the catalyst can be maintained in a highly active state at all times, so even if 8■ is increased, the olefin conversion rate does not decrease, and 8TY can be increased. In the case of a liquid phase reaction, a moving bed cannot be used.

[Action/Effect] Tertiary-butyl mercaptan, one of the mercaptans most in demand as an odorant for city gas, was synthesized using a moving bed method using isobutene as a raw material, and the following results were obtained. .

(1) For the catalyst, a spherical gel is made from a basic sol of aluminum hydroxide, and after heat treatment at 500° to 700°C,
The one that had been washed with water to remove sulfate roots etc. showed the highest activity. The alumina content of the catalyst thus obtained was over 99%, and the acidity was o, s r! ! Lol! q y y
That was it.

(2) When the reaction conditions are to maximize the yield, the blowing gas composition is nitrogen gas; hydrogen sulfide; isobutene = 20: 60.
: 40, the temperature is 800C, 18v, 120hr, but when considering the amount of generation, 8TY reaches its maximum at 8v, about 960. However, if the Sv is increased further, the conversion rate will drop significantly and by-products will tend to increase slightly, so 8T
On the contrary, Y decreases.

(3) Isobutene conversion rate under optimal conditions is 99.3%
, the selectivity reached 97.5% and the yield 96.8%.

(4) In order to keep the reaction conditions and production constant, a system in which the catalyst is regenerated and circulated as a moving bed is industrially preferred.

When the production amount of tert-butyl mercaptan was increased (sv: 960 hr), the olefin conversion rate was 97.
%, selectivity 92%, yield 89%, STY 1.25'
/me-hr.

Since the reaction is carried out using a moving bed method, the removal, regeneration, and charging of the catalyst are continuous, making long-term continuous operation possible. The reaction conditions are normal pressure and low temperature, and the yield is very high, so the equipment cost is low. Among mercaptans, this method is considered to be particularly useful as an industrial method for producing tertiary-butyl mercaptan, which is in high demand as an odorant for city gas.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited thereby.

[Example 1] A sodium carbonate solution was added to an aluminum sulfate solution to make it alkaline, and a sol of aluminum hydroxide was prepared.
An equal volume of 15% hexamethylenetetramine solution was added and stirred, then dropped into light oil to form a spherical gel, separated and dried, and then heated at various temperatures within the range of 300° to 1100°C for 2 hours. The catalyst was heat-treated, washed with water to remove sulfate groups, and dried to prepare a catalyst having 14 to 32 meshes. In order to examine the catalyst activity, a reaction tube filled with these catalysts was heated at normal pressure and 800C with gas composition: nitrogen gas; hydrogen sulfide; isobutene = 20; 50';
The isobutene conversion rate and tert-butyl mercaptan selectivity were measured. Furthermore, the micropore diameter and acidity on the surface of the catalyst particles were determined. The results are shown in Table 1.

In Table 1, the pore distribution of 40A or more was measured using a mercury porosimeter type 220 manufactured by Carlo Erba (Italy), and the surface area was the same as the pore distribution of 100A or less (0arlo Erba
It was measured using 8ORPTO+NATIC 1800 manufactured by Co., Ltd. Also, the acidity is the solid acid in benzene.
l yellow (P-di*netyl am
ino-azobenzene) as an indicator.
, lN-n-butylamine.

This indicator exhibits a red color when adsorbed onto a solid acid.

Q required for red to return to yellow, IN-n-but
Acidity was calculated based on the amount of hylamins added.

From this, it can be seen that high activity is exhibited when heat treatment is performed at an intermediate temperature of 500° to 700°C and the acidity is 0, s 1q/ or more.

[Example 2] A vertical glass tube with a diameter of 20 mm was used as the reactor.

The structure was such that the catalyst could be loaded and taken out continuously, and the inside was kept at a constant temperature by immersing it in an oil bath. The reactor was filled with the mucilage 4 obtained in Example 1 after being replaced with nitrogen.
A catalyst 60- was enclosed.

Olefin and hydrogen sulfide were preheated in a mixed gas preheater and blown into the bottom of the reactor, and the reaction gas exiting the reactor was cooled and collected in a condenser, and its composition was analyzed using a gas chromatograph.

The catalyst was continuously charged and taken out at a rate of 20"/hr. The reaction conditions, olefin conversion rate, and mercaptan selectivity are shown in Table 2.

Table 2 Note) Note) M
ar kawni iof f shows the selectivity of mercaptan obtained by addition reaction.

The above reaction conditions are all under normal pressure, and the reaction temperature is also a mild condition of 100°C or less depending on the type of olefin. Despite this, the olefin conversion rate and mercaptan selectivity vary depending on the carbon number and structure of the olefin, but the olefin conversion rate shows quite high values except for ethylene, and the mercaptan selectivity is extremely high. expensive.

The taken out waste catalyst was regenerated by heat treatment in air for 2 hours, and then the same synthesis test as above was performed using the regenerated catalyst, and it showed substantially the same conversion rate and selectivity.

[Example 3] Propylene tetramer and the catalyst particles obtained in Example 1 and Example 4 were finely pulverized to 150 mesh or less using a 100 mm square flask equipped with a condenser as a reactor.11.
4P is added to keep the temperature constant in the oil path. After keeping the reactor at 10,000 and bubbling hydrogen sulfide at 4 ml for 4 hours to react,
The reaction solution was separated by filtration and analyzed using a gas chromatograph. The results are shown in Table 3.

Table 3 When the number of carbon atoms in an olefin increases, it becomes liquid, so E
Although the reaction pattern is as shown below, the selectivity shows a considerably high value even in the liquid phase reaction.

[Example 4] Using the apparatus and the same catalyst as in Example 2, using isobutene as the olefin, blowing gas composition, reaction temperature, 8
Tertiary butyl mercaptan was synthesized by varying v. The reaction conditions and the results obtained are shown in Table 4.

Tert-butyl mercaptan can be obtained in high yield under a wide range of conditions as shown in Table 4, with very little by-products. When increasing the production amount considering industrial production, 8V960hr, conversion rate 9
7%, selectivity 92.6%, STY Ai, 32, and has considerably high productivity.

[Example 5] Using the catalyst obtained in Example IA4, a mixed gas of nitrogen gas: hydrogen sulfide: isobutene was prepared with a gas composition of 160:
8v960h so that the ratio is 420:380
r-', the reaction temperature was 80°C, and the catalyst was blown into a reaction tube filled with the catalyst. The reaction tube was a vertical tube with a diameter of 20 m and a length of 250 m+, and the inside was filled with 60 liters of catalyst, and 20 fnl of new catalyst was intermittently charged from the upper part every hour, and 20 liters of fresh catalyst was taken out from the lower part for continuous operation. As a result, the isobutene conversion rate was 9
7%, tert-butyl mercaptan selectivity 92%, 8TY
A substantially stable state of 1.25'/m/-hr was maintained. Note that after 20 hours, the regenerated catalyst was used, but the results were the same as in the case of a new catalyst. FIG. 1 shows the temperature at each part of the reaction tube, and FIG. 2 shows the changes in isobutene conversion and selectivity.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the reaction time and the temperature of each part of the reaction tube in Example 5. FIG. 2 shows the relationship between reaction time, conversion of isobutene, and selectivity of tert-butyl mercaptan.

Claims (3)

[Claims] (1) An olefin characterized by making a spherical gel from a basic sol of aluminum hydroxide and heat-treating it to have an alumina content of 95% or more and an acidity of 0.8^m^・^e^q/g or more. and an alumina catalyst used in the synthesis of alkyl mercaptans from hydrogen sulfide. (2) Create a spherical gel from a basic sol of aluminum hydroxide and heat treat it to create a moving bed of alumina catalyst with an alumina content of 95% or more and an acidity of 0.8^m^・^e^q/g or more. A method for producing an alkyl mercaptan characterized by passing an olefin and hydrogen sulfide. (3) The method for producing an alkyl mercaptan according to claim 2, wherein the olefin is isobutene and the alkyl mercaptan is tert-butyl mercaptan.