JPS58180459A - Method for producing nitrobenzene - Google Patents

Abstract

PURPOSE:To prepare nitrobenzene, in high yield, by the vapor-phase nitration of benzene with a nitrating agent using a catalyst comprising a solidified acid obtained by impregnating sulfuric acid in a solid carrier and calcining the product. CONSTITUTION:The objective nitrobenzene is prepared by the vapor-phase nitration of benzene with a nitrating agent selected from NO2 and N2O4, using a catalyst comprising a solidified acid obtained by impregnating sulfuric acid in a solid carrier (e.g. silica.alumina) in an amount of 5-50wt%, and calcining the impregnated product at 100-400 deg.C. The vapor-phase nitration reaction is preferably carried out at 100-300 deg.C, using 0.1-3 moles of the nitrating agent per 1 mole of benzene, and using an inert gas such as nitrogen as a diluent. The catalyst exhibits extremely high catalytic activity compared with the conventional silica gel catalyst and a phosphate-type catalyst, and scarcely yields the by-products such as dinitrobenzene.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for gas-phase nitration of benzene, and more particularly, to a method for converting benzene into NO! Or, it relates to a gas phase synthesis method for nitrobenzene, which is characterized in that a solid carrier is impregnated with sulfuric acid and a solidified acid obtained by sintering is used as a catalyst, in which N2O4 is used in the gas phase. be.

Nitrobenzene is used in large quantities as a raw material for aniline and as an intermediate for organic industrial chemicals, and is an important key industrial chemical. The method for producing nitrobenzene was first introduced in 1834.
Since the first nitration of benzene was carried out at the Mitscherlich Nyo-+, the principle has not changed to this day.

That is, this is a method of nitration in a liquid phase using a mixed acid that is a mixture of nitric acid and concentrated sulfuric acid. Although this process has progressed from the initial batch process to the current continuous process, the problems associated with the liquid phase process of waste sulfuric acid and wastewater treatment remain unsolved.

On the other hand, the gas phase sealing method using NOx is being considered because it is expected to have advantages such as the simplicity of the process, no waste sulfuric acid, and the ability to use nitrogen oxides, which are cheaper than concentrated nitric acid. However, unfortunately, it is not as good as the liquid phase method in terms of high yield and catalytic activity, and so far it has not been commercialized. Until now, there are only the following two descriptions of the gas phase nitration method for benzene.

l) U.S. Patent No. 2,109,8788 and Industry and Engineering Chemistry-June
, 1986, p. 662' R:1. to t:z
There is a description that the gas phase nitration of <Se> with N01I is carried out using silica gel as a catalyst. According to the description, silica gel with a particularly high surface area is highly active, but even in that case, the reaction temperature is as high as 810°C, and No. /benzene molar ratio = 2, Wtisv of benzene (
z delivery room speed) = 0.0206~(1,165Ks+
/ to 9-catalyst hr toy at extremely slow feed rate,
Space-time yield -0,0145 to 0.0518 Kz/Kt ・
Catalyst/HR performance is low.-C.

According to the description in the same document, only silica gel has catalytic activity, and bauxite, activated alumina, Ti□+-pumice, etc. are said to be ineffective for gas phase nitration of benzene.

It is also estimated that the reaction follows the following equation.

2) British Patent No. 586.782 describes benzene HNO
There is a description that gas phase nitration using a or NO2 is carried out using a phosphoric acid salt or a calcined product of phosphoric acid supported on a solid absorbent as a catalyst. According to that example, nitrobenzene was obtained by using calcium metaphosphate as a catalyst and choking benzene with KNOs, but the molar ratio of 08/benzene = 0.864, mK = 175°C, WH8V' =
Space-time yield of nitrobenzene under conditions of 0.1761'l//l-M[・hr -0,074Ky/l・catalyst・h
The result has been as low as r.

Note that this document does not include any specific example of gas phase nitration using N(h+).

On the other hand, gas phase nitration has been studied for the purpose of controlling the isomer ratio (para/ortho ratio) of nitrochlorobenzene produced during nitration of chlorobenzene. When chlorobenzene is gas-phase nitrated with NOx in the presence of a molecular sieve catalyst (zeolite catalyst) according to JP-A-54-9552, (5) nitrochlorobenzene with a para/ortho ratio controlled over a wide range can be obtained. There is a description of. In this case, examples of specific zeolites and catalysts include [Zeolon-900J,
AW-500 Sheave”, “Zeoron 800 j”, “18
"X Molecular Sieve" is listed. As for the reaction results, for example, [When Zeolon 900-1-IJ is used as a catalyst, reaction temperature is 200°C, NOs/chlorobenzene molar ratio = 2.87, chlorhene-V (DM/'EfSV = 0.289 Kf/t・
At a feed rate of catalyst -hr (but diluted with 80 times nitrogen gas), space-time yield (STY) = o, 098
Although the results of Kf/l-catalyst-br are insufficient for rice, the activity is insufficient.

Note that this document does not mention that gas phase nitration of benzene is performed using the zeolite catalyst.

Furthermore, a series of patents are known which aim to control the P2O ratio in the nitration of helobenzene. That is, JP-A-50-121284, JP-A-50-126626, JP-A-50-(6) 126627, JP-A-51-6981, and JP-A-5.
No. 1-19784. Although these are related to the gas phase nitration of thremohalobenzene, judging from the contents of the specification and examples, the embodiments of the invention are substantially limited to methods using nitric acid as the nitration agent. It is something that The above patent specification mentions NO as a nitrating agent.
Is there also a statement that 2 is also used? There are no specific examples in the Examples to support this. Furthermore, the oxidation numbers of N in nitric acid and NO2 are pentavalent and tetravalent, respectively, and they are clearly different chemical species. Therefore, embodiments in which nitric acid is the nitrating agent and embodiments in which NO2 is the nitrating agent should be considered to be different systems of technology.

Note that all of these are only descriptions regarding the nitration of halobenzene, and there is no description at all about the method for producing nitrobenzene by nitration of benzene, which is the object of the present invention.

As mentioned at the beginning, tenitrobenzene is a key industrial chemical, and its production volume far exceeds that of halonitrobenzene. Therefore, if an excellent new process is developed, the benefits are expected to be enormous. .

In view of the possibility that gas phase nitration of benzene using NOx has the various advantages described above, the present inventors have arrived at the present invention as a result of diligently searching for a catalyst active in gas phase nitration. This is what I did.

The present invention is a method for nitrating benzene in a gas phase using a nitrating agent such as NO2, in which a solidified acid obtained by impregnating a solid carrier with sulfuric acid and calcining the catalyst is used. The present invention relates to a characteristic gas phase nitration method of benzene.

According to the method of the present invention, the gas phase of the conventionally known benzene 21.
Extremely high catalytic activity can be obtained compared to the silica gel catalyst or phosphate-based catalyst used in the blocking method, and good reaction selectivity with almost no by-products such as dinitrobenzene can be obtained.

By the way, the filtrate-liquid phase nitration by kneading nitric acid and sulfuric acid is explained by the ionic mechanism, which is expressed by the -domain equations (2) to (4), and the tail is (Kirk -OthmerI Enc
cyclopedia of Cbemical 'l'
ecuolt)gy/r 2nd, Ed.

Vol, 18 785-788)
10klF30a (2) There are various theories regarding gas phase nitration, and there is no consensus among the US.

In other words, according to pages 790 to 795 of the cited document, it is explained by a free radical mechanism (formulas (5) to (7)) (% formula % (5) (6) (7) ) to 7) aromatic cation radical. Equations (8) to (9), etc.) estimating the reaction mechanism between
6n6: (06H6)su・-(8)(C,H,)-'
;-10NO2-→0,1(,,NO2+ 0aHa-
(9) On the other hand, Aus 1 (108, P et al.
Internal, 1onalJournal of
0hea+1cal Kin@tios // 1
978 (IQ) 657-667) Estimating the machine list.

Searching for a catalyst active in gas-phase nitration under such circumstances is extremely difficult, as even establishing a working hypothesis is difficult, but the solidified sulfuric acid catalyst used in the method of the present invention has high activity. What they achieved was a truly astonishing discovery.

The catalyst used in the method of the present invention will be explained.

It is known that solid 1b acid made by impregnating sulfuric acid into silica gel and firing it has catalytic activity for catalytic cracking of petroleum (e.g. M, WTa+nale//
Diso, Faraday 8oa, 8270 (
1960) /') Also, its #ness and acid strength are 11
．． A, as measured by Ban5si (t
t J, Phyi+, Ohem, 61, 970 (
1957)

According to the latter literature, solid sulfuric acid has an acidity function n.

It is said to have a relatively strong acid strength expressed as -5,6>l1iO>-8,2. As mentioned above, there is no established theory as to whether the free a & ionic mechanism of gas phase nitration in the method of the present invention is an ionic mechanism, but considering the fact that the solidified acid in the method of the present invention was effective as a result. Therefore, it is highly likely that the reaction is proceeding through a cationic mechanism.

The sulfuric acid used in the method of the present invention is one with as high a concentration as possible, preferably concentrated sulfuric acid. The amount of sulfuric acid impregnated into the carrier is 1 to 50 wt%, preferably 5 to 80 wt%.
It is.

Examples of the solid carrier impregnated with sulfuric acid include silica-0-alumina, silica gel, diatomaceous earth, and alumina.

Firing treatment after impregnation with sulfuric acid is from 100℃ to 400℃
1 Preferably carried out at a temperature of 150°C to 300°C for several hours.

The nitrating agents in the method of the present invention include NO2 and N
Among them, NO2 is particularly preferred. Furthermore, it is well known that No is readily oxidized to No2 in the presence of oxygen, but in the method of the present invention, NO2 generated in the reaction system is A method using a nitrating agent is also adopted. (11) In the gas phase nitration in the present invention, the reaction temperature is 100°C to 800°C.
It is carried out by continuously feeding a gaseous mixture of benzene and a mouthwash over a bed of solidified sulfuric acid catalyst while maintaining the temperature at 0.degree. C., and separating the formed nitrobenzene from the gaseous mixture. Preferably, the gas phase nitration reaction is carried out in the presence of an inert gas such as nitrogen as a diluent. A specific example of how the reaction occurs in this case is as follows. Benzene is preheated and vaporized, fed into the reactor after mixing with a constant flow of diluent nitrogen gas, and then treated with a nitrating agent (NO) before contacting the heated catalyst bed.
After mixing with the gas phase flow of (2), etc., the mixture is introduced into a heated catalyst bed for a catalytic reaction.

The nitrating agent preferably used in the present invention is NO2, and the molar ratio of NO2 to benzene is generally from 0.1 to
The molar ratio is 8.0, more preferably 08 to 2.5.

Each reaction component and diluting nitrogen gas can be fed into the reactor at any space velocity while maintaining a predetermined composition (12) ratio.

In order to explain the present invention in more detail, specific examples are listed below, in which the activity of the catalyst is compared and studied using two methods. One method is an atmospheric fixed bed flow reaction, which is commonly used in catalyst activity tests, and the other is a micropulse reaction. The first method, atmospheric pressure fixed bed flow reaction data, is often used in patents, literature, etc. as a means of proving catalytic activity, as it indicates so-called steady-state activity, and there is no problem.

The second method we used, the micropulse reaction, is a reactor in which a microreactor and a gas chromatograph are directly connected, and the catalytic activity can be measured extremely easily. It is said to indicate. Regarding the micropulse reaction, Murakami et al.
#Catalyst vol. 1.2B (6) pp. 488-487 (19
1981)) and (J Walter T, Re1chl
e (tt Cl1F&l”ECH, Nov, 198
1698-702 #) describes its (18) 1 "requirements and precautions for use in catalyst activity testing. According to it, as mentioned above, the micropulse reaction is an unsteady reaction,
It is stated that because the flow reaction is a stationary reaction, the results of the two may or may not match.
Aside from detailed comparisons of reactions, it is useful for rough activity comparisons such as whether the activity of a certain catalyst is zero or whether there is a large difference in activity between two types of catalysts. Sufficient for use. In fact, there are some examples of using micropulse reactions for comparative studies of catalytic activity in various literature (for example, I 48th Catalyst Symposium Preliminary Results (G) (1981), 19
4 pages, 220 pages, 286 pages, 272 pages, 278 pages, etc. I
) We also used the micropulse reaction method because of its simplicity, but we also collected data for comparison with the normal pressure flow method. As a result, it was confirmed that when the reaction is limited (in the case of the present invention, gas-phase nitration of benzene with NO2), the trend in the magnitude of catalyst activity obtained in the micropulse reaction is consistent with the trend in the normal pressure flow reaction. are doing.

(14) The following examples are part of specific embodiments of the present invention,
The present invention is not limited thereto.

The calculation methods for conversion rate, yield, and selectivity in Examples are as follows.

Example 1 (Part 1) 20 parts of silica/alumina (manufactured by JGC Chemical, N-681 (L), alumina metal = 18 wt%) powder was uniformly impregnated with 10 parts of concentrated sulfuric acid, and then baked at 200°C for 2 hours. .

This was molded under pressure and crushed to obtain a granular catalyst of 24 to 28 meshes.

Example 1 (Part 2) (Catalytic activity test using micropulse reaction) First, the micropulse reaction method will be explained. The reaction apparatus is described in the literature of Murakami et al. (Catalyst V (11, 28 (6), pp. 488-487 (1981)) cited above.
) is described in detail. Inner diameter 4 earthquakes, length 200n
A quartz glass micro-reaction tube is placed in an electric furnace and attached to the front stage of the injection section of a gas chromatograph.

After filling this micro-reaction tube with quartz wool to form a vaporization section, the lower layer is filled with a catalyst of about 50Tn9 to about 200Tn, and the catalyst is first preheated at a predetermined temperature while nitrogen or helium as a carrier gas is flowed at a constant flow rate. Heat treatment.

Next, a mixture of benzene and N2O4 was cooled with water (there is no explosion range data for the benzene/N2O4 mixture system. Because of the potential danger, the mixture was prepared in a very small volume and handled under water cooling) using a microsyringe of about 0.5 to 1 μm. Collect the sample and immediately inject it from the -L part of the micro reaction tube. A mixture of benzene and N204 passes through a quartz wool vaporization section together with a carrier gas (nitrogen or helium) to become benzene vapor and NO2 gas, respectively, and then contacts the catalyst bed and reacts.

This reaction mixture is directly introduced into a gas chromatograph and analyzed.

Experiments were carried out as follows using the micropulse reactor.

The solidified sulfuric acid catalyst synthesized in Example 1 (Part 1) was
Fill a micro reaction tube and preheat at 200°C for 0.5 hour while flowing helium at a flow rate of 48-7 minutes.

Collect 0.5μ of a mixture of benzene and N2O4 (NO2/benzene molar ratio = 2.7) with a water-cooled F microsyringe and quickly inject it from the -L section of the microreaction tube.

The temperature of the catalyst bed (reaction temperature) is 200°C. The analysis conditions for the gas chromatograph were as follows.

Glass column 8ΩX 2 m Column packing material = 5% PEG 2 Q M/Unipo
rtHP (iQ~80 mesh injection part temperature = 250°C (17) The obtained results were that the benzene conversion rate = 99.1% and the nitrobenzene selectivity -97.8%.

Example 2 The NOm/benzene molar ratio was set to 1.76.1.1.0.
Reaction 6 was carried out in exactly the same manner as in Example 1 except that 55 and 0.2 were used.
I did this. The results obtained are shown in Table-1.

Table 1 Example 3 90 parts of silica gel (manufactured by Menso Kagaku, S = 720 m"/g) was impregnated with 10 parts of concentrated sulfuric acid and fired at 200°C for 2 krrs. After pressure molding, it was crushed to give 24 to 48 mesos. (1 g) of this was packed into a 50 In? micro reaction tube, and the reaction was carried out according to Example 1 (Part 2). The molar ratio of N02/benzene = 1.0. The result is a benzene conversion rate of −8
The selectivity for 0.4% nitrobenzene was 98.6%.

Example 4 Silica gel (manufactured by Onsen Kagaku, 8-=72 On?/9
2) irs at 200℃ after impregnating 20 parts of ) with 10 parts of concentrated sulfuric acid.
, fired. This was molded under pressure and then molded into a granular catalyst having a size of 24 to 48 mesh. A micro reaction tube was filled with 50~ of this catalyst, and a reaction was carried out according to the actual MfAeiIJ1 (Part 2). However, the reaction temperature is 200℃, 150℃ and 100℃.
℃ and 8 points changed. The results obtained are shown in Table-2.

Table 2 Comparative Example 1 501 days of silica gel (0,8,1', No. 2,109,878), which is a known catalyst, was used for gas phase nitration of benzene/N02, and the specified reaction shown in Table 8 was carried out. The reaction was carried out according to Example 1 (Part 2) except for changing the temperature.

The results obtained are shown in Table 8.

Table 8 Comparative Example 2 Same as Example 1 (Part 2) except that 50 rrq of phosphoric acid catalyst (Bri, P, No. 586,782), which is a known catalyst for gas phase nitration from benzene/NO2, was used. The reaction was carried out identically. The results obtained are shown in Table-4.

Table 4 Example 5 Experiments were conducted as follows using a normal atmospheric pressure fixed bed flow reactor. The solidified sulfuric acid catalyst prepared in Example 1 (Part 1) (24 cm
2 g (marks 8,8) of 48 mSO3) were filled and preheated at 200° C. for 2 hours under a N2 stream. Benzene is fed into a molten alumina filling system (21) using a microfeeder and vaporized. On the other hand, N2O4 was fed by an ice-cooled microfeeder and the N2O4 was vaporized.
The Ox is diluted with a diluent N2 carrier and mixed with benzene vapor.

The raw material mixed gas is introduced into a reaction tube and undergoes a catalytic reaction on a catalyst bed maintained at a predetermined temperature. After leaving the reaction tube, the reaction mixture gas was trapped in water cooling, and the exhaust gas was neutralized with alkaline water and then purged. The trapped material was analyzed by gas chromatography. Table 5 shows the reaction results under each reaction condition. However, the abbreviations in the table are as follows.

8■: Gas space velocity (hr) 8'l'Y: Space-time yield (K9/z -0at -hr
, )(22)

Claims (1)

[Claims] (1) A method for nitrating benzene in a gas phase using NO2 or N2O4, characterized in that the reaction is carried out using a solidified acid obtained by impregnating a solid carrier with sulfuric acid and calcining it as a catalyst. A method for gas phase nitration of benzene. (2) The solid carrier is silica/alumina, silica gel,
The method of claim 1, wherein the material is diatomaceous earth or alumina. (8) The method according to claim 1 or 2, wherein the amount of sulfuric acid impregnated is in the range of 5 to 50 wt% of the carrier. (4) The method according to claim 1.2 or 8, wherein the firing is carried out at a temperature range of 100 to 400°C. (5) The method according to claim fJ1.2.8 or 4, wherein the gas phase nitration reaction is carried out at a temperature in the range of 100 to 800°C. (6) The method according to claim 1.2.8.4 or 5, wherein 0.1 to 8 mol of nitration agent is used per 1 mol of benzene in the gas phase nitration reaction. (7) Claims 1.2S and 4.5J in which the K-phase nitration reaction is carried out using an inert gas such as nitrogen as a diluent.
or the method described in Section 6. (8) Claim 1.2.8.4, wherein the product obtained by the gas phase nitration reaction is nitrobenzene.
．． 5. The method described in 6 or 7.