DE1230013B - Process for the production of vinyl acetate - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C07c

C07b

German KL: 12 o -19/03

Number: 1230 013

File number: K 41580IV b / 12 ο

Filing date: August 30, 1960

Opening day: December 8, 1966

In the synthesis of vinyl acetate and vinyl chloride in the gas phase is in the reaction zone as a result of Heat of reaction the temperature not constant.

Such reactions are carried out with a fixed catalyst or with a fluidized bed catalyst worked.

The devices with a fixed catalyst have a tube bundle or box shape, arranged to fill the granular catalysts and to achieve one Heat exchange between the reaction zones in order to maintain a certain reaction temperature, a heat exchanger in the between the Reaction zones formed spaces is arranged. The characteristic feature of these devices consists in the fact that the heat conducting surface per unit quantity of catalyst is achieved by using the tube bundle design increased and by simply keeping the temperature of the heat exchanger constant a sufficient one Stability of the reaction temperature is achieved. Such devices have the disadvantage that the temperature distribution inside the reaction zone is not uniform.

In the case of the devices with a fluidized bed catalyst, the heat conducting medium is around the reaction zone a heating jacket is provided around it. For example, in the manufacture of vinyl acetate, it is sufficient to derive it the heat of reaction of the heat exchangers in the heating jacket is not all, as the heat-conducting surface depends Unit of quantity of the catalyst for the normal size of the device except for a small size is less than that of a device with a fixed catalyst, so that even though a uniform reaction temperature can be achieved locally in the interior of the reaction zone and the Temperature in the zone can also be controlled temporarily by having one sufficiently provides a large difference between the temperature of the heat exchanger and the reaction temperature, difficult is the temperature with increasing the dimensions of the device exclusively with Help to keep the heat exchanger in the heating jacket constant. It is also provided that the generated Amount of heat is large and the device is enlarged, required the difference between To increase the reaction temperature and that of the heat exchanger accordingly, however, is practical a limit, accordingly means for rapid control of the reaction temperature are suggested been brought in such a way that small heat pipes are provided in the flow zone for the supply of the Heat exchanger that has a temperature difference Process for the production of vinyl acetate

Applicant:

Kurashiki Rayon Company Limited,
Kurashiki (Japan)

Representative:

Dipl.-Ing. R. Müller-Borner
ίο and Dipl.-Ing. H.-H. Wey, patent attorneys,
Berlin 33, Podbielskiallee 68

Named as inventor:
Jun Adachi, Ashiya;

Shogo Fujita, Okayama;
Keigo Kimura, Toyama;
Akio Naganuma, Tamashima (Japan)

Claimed priority:

Japan September 4, 1959 (28153)

from several tens to several hundred degrees from the reaction temperature, but its effect is not yet entirely satisfactory.
For example, a process for producing vinyl esters by passing acetylene and acid vapor over heated catalysts is known, in which the reaction temperature is to be kept constant. In this known process, this is achieved in that the gas mixture leaving the reaction space is divided into two parts, that the reaction product is separated from one part by cooling, that both parts are combined and passed over the catalyst again, the quantitative ratio of the two Proportions is controlled so that the reaction temperature should be kept constant. However, since part of the vinyl ester obtained is repeatedly returned to the reaction cycle, it undergoes partial thermal decomposition in the reaction space, so that the vinyl ester obtained has a comparatively high content of impurities. In the course of the following description, the technical progress that can be achieved with the method according to the invention compared to this known method is demonstrated by means of a comparative experiment.

The invention is based on the fact that the control of the reaction temperature, in contrast to the previous

609 730/423

3 4

previous method most effective and cheap - In contrast, fluctuated after the method Most can be carried out by, the invention, the temperature of the inflowing as determined by various studies, the gas is strongly between 121 and 135 ° C, while the was, the temperature of the starting material at the temperature of the heating medium constant at 163 ° C and Input of the device according to the changes - the reaction temperature was constant at 183 ° C, tion of the reaction temperature regulated, whereby one in the known method were based on the heat generated in the device for converted acetic acid, 93 mole percent vinyl acetate warm the introduced at low temperature and, based on the converted acetylene, 90 Molpro-gases used on the reaction temperature. cent vinyl acetate, while the process -

The inventive method for producing io ren according to the invention, based on converted vinyl acetate by reacting acetylene with acetic acid, 99 mol percent vinyl acetate and, based on acetic acid in the presence of a catalyst at reacted acetylene, 95 mol percent vinyl elevated temperature, with one with HiMe Heat acetate could be obtained,
exchanger is kept largely constant, is characterized in that the reaction gases in 15 examples
divides two parts, one part by a heat ex- It shows

exchanger leads, the ratio of the two parts Fi g. 1 an example with a small capacity of the pre

depending on the temperature of the reaction direction and

zone is regulated automatically. Fig. 2 shows an example with a relatively large ca

Heat conducting surfaces and heat exchangers are not the capacity of the device :. ·
especially necessary, since the heat of reaction without In Fig. 1 denotes a small device into which the kör-disruption of the temperature distribution in the reaction _n i _ger catalyst is filled, with a jacket around the pre-zone for preheating the one under the reaction direction. 2 is provided for the circulating temperature of the inflowing oil. The catalyst used is and is used with zinc, the gas mixture soaked and dried granular activated charcoal bed directly into the lower section of the flowing acetate. The grain size must be selected so that the reaction temperature by regulating the temperature, that the temperature of the gas flowing into the device, determined by the reaction conditions, can be kept at the same flow rate as the gas flow rate. · Condition is met. From a blower and

Another feature of the invention in addition to the acetylene supplied to an acetic acid vaporizer

The control of the reaction temperature is that gas or acetic acid vapor are

the temperature of the heat exchanger mixed together in the correct mixing ratio

tel comfortably at one of the reaction temperature and flow in from 3 and go through a temperature

can maintain a high temperature. . temperature control system, d. H. by a preheater or

If the method described above is used for a cooler 4, a preheating or cooling branch line 5

Control of the temperature is carried out, so there is and through special flow and return regulating

no limit on the size dimensions valves 6 and 6 'therethrough, are preheated to

the device with a fluidized bed catalyst, and one of the reaction temperature at this time

the method allows a device to operate at a temperature set and flow

device with large capacity, which with the previously loaded 40 through the lower portion of the device 1, Known devices in which the reaction 'taking the reaction at a certain temperature

temperature with the help of the heat exchanger. The vinyl acetate vapor generated in this way flows

is controlled and for larger dimensions the front at the top of 1 together with not for re-

In the same direction, the heat-conducting surface of the heating jacket also acts with acetylene and acetic acid vapor

per unit quantity of catalyst is lower, the 45 off.

Driving makes the heating jacket superfluous, so it leads the mechanism of the temperature control section

to a device of very simple construction. can be varied depending on the operating conditions

The following comparative experiment shows that they can be modified in different ways; he persists

the method according to the invention compared to the example shown from a parallel circle,

the aforementioned known method achievable tech- 50 a preheater or cooler 4 for the circulation of the

frilly progress. During the experiment, fol- heat-carrying oil and a preheating or cooling

The following conditions: secondary line 5, with the special pre- and

Reaction vessel diameter ... 0.4 m Return flow regulating valves 6 and 6 'with the aid of the

• _τ. Reaction temperature change over time

Kataiysatorviel 150 1 _{55 speaking} signal actuated and that through

Catalyst grain size the preheater or cooler 4 flowing outlet

(Sieve mesh size) 48 to 100 _gas with high temperature as well as the

Raw gas throughput 1.29 kg · mol / h heating or cooling branch line 5 flowing off-molar ratio of acetylene and common gas of low temperature before their arrival

Acetic acid 2.48 ^{60 m} ^ er device 1 in a certain flow

Test duration δ'ΐι ratio and at a suitable temperature

"be mixed.

The following results were obtained: Öei Usually such a control device

the known process, the temperature of a large time lag, making it difficult to

inflowing gas constant 130 ° C, while the 65 is control, and especially with low capacity of the

Temperature of the heating medium easily between 157 and device and high efficiency of the heating man-

163 ° C and the reaction temperature is stronger and the heat capacity of the heating jacket is the same

fluctuated irregularly between 170 and 190 ° C. Change in the internal temperature in a certain

start out so that an instrument 7, as shown in FIG. 1, the special flow and return regulating valves 6 and 6 ' actuated directly with the aid of the signal corresponding to the change in the internal temperature α in the reaction vessel 1 is sufficient.

If, on the other hand, the device has large dimensions, the efficiency of the heating jacket is relatively low and it is necessary to use two instruments shown in FIG. and 8 and to use the so-called compound control system, in which the instrument 7 determines the internal temperature α in the reaction vessel 1 and issues a control command to the instrument 8 according to the temperature change, while the instrument 8 determines the temperature b of the output gas and the special flow and return regulating valves 6 and 6 'actuated to adjust the temperature to the control command given by the instrument 7. An example of the results of typical normal operation of devices of different sizes is shown in the table below.

example 1 Example 2 Example 3

Reaction vessel diameter, m

Amount of catalyst, 1

Catalyst grain size, mesh size

Reaction temperature ^{, 0 C}

oil temperature in the heating jacket, ⁰ C

Raw gas throughput, kg · mol / h

Molar ratio of acetylene and acetic acid

Catalyst exchange factor, ° / o day

Vinyl acetate yield, t / day

Average raw gas preheating temperature, ⁰ C

Heat of reaction, kCal / h

Amount of heat required to preheat the raw material, kCal / h

0.4 1.0 2.6 150 1,800 32100 48 to 100 32 to 42 24 to 45 180.5 190 183 180.5 190 142 1.29 13.6 15.5 2.48 2.95 2.41 3.0 2.0 1.2 0.215 2.30 37.0 114.8 116 108 2300 24 600 394,000

2290

24 400

310,000

The point to be considered in carrying out the method according to the invention is that the Acetic acid in the gas portion with a low temperature with a considerable drop in the raw gas temperature, condensation and for this reason the temperature of the starting gas is never unrestricted can be reduced, but must be kept at a value that is to be maintained such a condition is sufficient that condensation of acetic acid in no section of the Gas distribution pipe occurs.

Claims (1)

Claim: Process for the production of vinyl acetate by reacting acetylene with acetic acid in Presence of a catalyst at elevated temperature, with the help of a heat exchanger the temperature is kept largely constant, characterized in that the reaction gases are divided into two parts, a part passes through a heat exchanger, the ratio of the two parts as a function of is automatically regulated by the temperature of the reaction zone. Considered publications:
Austrian patent specification No. 162 578. 1 sheet of drawings 609 730/423 11.66 © Bundesdruckerei Berlin