JPS6025188B2 - Fixed catalyst catalytic reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixed catalyst catalytic reaction apparatus, and more particularly to a fixed catalyst catalytic reaction apparatus equipped with a catalyst bed having a curved structure.

Fixed catalyst catalytic reactors are widely used on a large scale as industrial reactors.

The catalyst bed in a conventional fixed catalyst catalytic reaction apparatus is a flat plate type, and in such a catalyst bed, the catalyst layer on the catalyst bed undergoes thermal expansion or contraction due to sintering during the reaction.
Furthermore, temperature changes in the catalyst bed and other factors often cause deformation of the catalyst bed itself, resulting in cracks in the catalyst bed or gaps around the catalyst bed. For this reason, if continuous operation is performed for a long period of time, the yield etc. gradually decrease, and stable long-term operation is not possible. For example, the most typical example is
There is a formaldehyde synthesis reaction from methanol and air using a dehydrogenation method (methanol excess method). Although this reaction will be explained as an example, the present invention is not limited to this reaction. The dehydrogenation method uses crystalline silver particles as a catalyst and operates at a reaction temperature of 600 to 70 psi, but if it is operated continuously, cracks in the catalyst layer or gaps will occur around the catalyst layer. Of course, raw material methanol passes through these as is, and oxygen in the air passes through unreacted, producing formic acid through the side reaction shown in the following reaction formula with the high-temperature reaction product gas, resulting in a decrease in yield. cause

As a way to solve these drawbacks, the Special Publication No. 47-379
25 and US Pat. No. 2,745,722, there is a method of supplying a catalyst during the reaction to fill the cracks and gaps, but such a method not only requires a special catalyst supply device, but also It has the disadvantage of being complicated to operate.

Furthermore, since the flat catalyst bed as described above has low mechanical strength, it requires a reinforcing material to support the catalyst bed, which is not economical.

As a result of intensive studies to solve these drawbacks, the present inventors successfully solved these drawbacks by installing a catalyst bed having a curved structure in place of a flat catalyst bed in a fixed catalyst catalytic reaction apparatus. The present invention was completed by improving the yield and enabling stable long-term continuous operation. The present invention
A fixed catalyst catalytic reaction apparatus equipped with a catalyst bed having a curved structure is provided, and the structure of the catalyst bed of the present invention will be described in detail below.

The basic structure of the reactor of the present invention is that the catalyst bed 2 has a curved structure as shown in FIG. FIG. 1 is a longitudinal cross-sectional view of the fixed catalyst catalytic reaction apparatus of the present invention, in which 1 is a raw material gas inlet, 2 is a catalyst bed having a curved structure, 3 is a reaction gas outlet, and 4 is a catalyst layer.

The term "catalyst bed having a curved structure" as used in the present invention means a structure having a curved portion in the vertical cross-sectional view of the catalyst bed in contact with the catalyst layer, for example, as is clear from the vertical cross-sectional views shown in FIGS. 3a to 3f. , structure a curved in a circular shape, structure b curved in an elliptical shape, structure c whose peripheral part is curved in a circular or elliptical shape but the base part is a flat plate, and the peripheral part is conical and the base part is circular. These include a structure having a shape d to an elliptical shape e, a curved structure f having a plurality of different curved surface radii, and the like.

As is clear from the vertical cross-sectional views shown in FIGS. 3a to 3f, for example, a circularly curved structure a [e.g.
43-1975, page 80, c in Figure 5, 1 has a full hemispherical shape], elliptical curved structure b, [for example, JIS
B8243-1975, page 80, Fig. 5, 1 (b) has a semi-ellipsoidal shape], the periphery is curved in a circular or elliptical shape, but the base is a flat plate (c), and the periphery is conical. A structure in which the base part has a circular shape d to an elliptical shape e, a curved structure f consisting of a plurality of different curved surface radii [for example, J
ISB8243-197 Hair, page 80, figure 5, 1 a-sara] etc. The degree of curvature is not particularly limited and may be determined based on the diameter of the catalyst layer, the type of catalyst, etc., but when the shape of the curvature is a circularly curved structure a, the radius R of the curved surface and the catalyst The ratio with floor flea D is R:
D=1:0.5-2 is preferable, R:D=1:0.75
~1. Ridges are particularly preferred.

Moreover, when the shape of the curve is structure b, which is curved into an elliptical shape, it is preferable that the short axis:long axis=1:1.5 to 3. In the reactor of the present invention, since the catalyst layer can be arranged in a curved shape using the catalyst bed described above, the internal compressive stress of the catalyst layer acts on the catalyst layer and can prevent the occurrence of cracks on the surface of the catalyst layer. . Therefore, as mentioned above, the catalyst bed of the present invention is excellent not only as a silver catalyst when producing formaldehyde from methanol, but also when the catalyst expands or contracts due to temperature changes or other factors during the reaction, causing cracks or gaps. be effective. Furthermore, it is preferable to provide an escape margin for the catalyst around the periphery of the catalyst layer, since this creates a space that absorbs the expansion of the catalyst layer, thereby further preventing the occurrence of cracks.

In addition, in a flat catalyst bed, for example, even if a large amount of catalyst is placed and stacked in advance around the catalyst layer in order to prevent the formation of gaps around the catalyst layer, the formation of gaps is unavoidable and as mentioned above, unreacted Passage of gas occurs.

This problem becomes more serious as the diameter of the reactor increases, and is especially likely to occur when the diameter of the reactor is 80 mm or more, for example, in the case of silver grain catalysts used in the production of formalin. Furthermore, since the catalyst bed has a curved structure, it has increased structural strength compared to a flat catalyst bed, so the plate thickness can be reduced and no reinforcing material is particularly required. In addition, since the thermal reaction force that causes cracks in the catalyst layer due to temperature changes escapes through the curvature of the catalyst bed, there is no need for special modifications to the catalyst bed to withstand thermal stress, resulting in a very simple structure. Furthermore, the fixed catalyst catalytic reaction apparatus of the present invention can also be applied to a waste heat recovery reaction apparatus in which a heat exchanger is provided at the outlet of the reaction apparatus and the heat held by the reaction product gas can be recovered. In waste heat recovery reactors equipped with a type heat exchanger, the tube plate at the top of the heat exchanger is curved to prevent air bubbles generated in the cooling medium from stagnation, but if the catalyst bed is a flat plate, Considerable space is unavoidable between the tubesheet and the catalyst bed.

The presence of such a space is undesirable because it causes side reactions or thermal decomposition of the reaction product gas, and it is preferable to minimize such a space and cool the reaction product gas as quickly as possible. Samurai Kosho No. 51-12028 is a multi-change waste heat recovery device that solves this problem, but in this, the tube of the heat exchanger protrudes above the upper tube sheet, and there is a space between the upper end of the tube and the tube sheet. The cooling liquid is stored to reduce the space described above, and the reaction product gas can be carried quickly.

However, in the reactor equipped with the waste heat recovery device of the present invention, the catalyst bed is curved as shown in Figure 2, so the catalyst bed can be placed near the tube plate of the heat exchanger, which solves the problem. The space can be greatly reduced, the generated gas can be easily cooled quickly, and there is no need for special work like the above-mentioned Hakama Kosho stock No. 51-112028.

Examples of the present invention are shown below, but the present invention is not limited to the following examples.

EXAMPLE The catalyst bed shown in FIG. 3 f was installed and packed into the reactor of the present invention shown in FIG. 2 so that the silver catalyst bed had a diameter of 1200 mm.

Next, a mixed gas of methanol steam and air, which was a raw material gas, was passed through a catalyst layer maintained at about 650° C. to carry out a formaldehyde synthesis reaction. The high-temperature reaction product gas was introduced into a shell-and-tube heat exchanger attached to the bottom of the catalyst bed, where it was rapidly cooled, and then introduced into an absorption tower where it was absorbed into water. This is 1
The reactor was operated for several months, and Table 1 shows the results of analyzing formaldehyde-absorbed water during this period and the average yield. Furthermore, this 1
No cracks or peripheral voids occurred in the catalyst layer for several months. There was also no adhesion of solid carbon produced by the decomposition of formaldehyde inside the heat exchanger tube.

Note that the formaldehyde yield was calculated using the following formula.

Formaldehyde yield = Formaldehyde produced (number of moles) 10 Recovered methanol (number of moles) XI.

〇% Methanol supplied (number of moles) U Formaldehyde synthesis was carried out in the same manner as in the example using a conventional waste heat recovery reactor having a flat plate type catalyst bed (silver catalyst bed diameter = 120 cm).

One week after the reaction started, cracks appeared in the catalyst layer, and about two weeks later, large gaps appeared around the catalyst layer, so the reaction was stopped. The analysis results and average yields of the formaldehyde-absorbed water during this period are shown in Table 2, and it was found that a large amount of solid carbon adhered to the heat exchanger tubes. Second

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an example of the fixed catalyst catalytic reaction apparatus of the present invention. FIG. 2 is a longitudinal sectional view showing an example of the reaction apparatus of the present invention equipped with a waste heat recovery device. FIG. 3 is a longitudinal sectional view showing an example of a catalyst bed having a curved structure according to the present invention. In Figures 1 and 2, 1 is the raw material gas inlet, 2 is the catalyst bed, 3 is the reaction gas outlet, 4 is the catalyst layer, 5, 6, 7, and 8 are the tube sheets and heat exchanger tubes of the waste heat recovery device, respectively. , indicates the coolant inlet and the coolant outlet. Noo - Ren a / Juice 2 figure ke 3 figure

Claims (1)

[Scope of Claims] 1. A fixed catalyst catalytic reaction apparatus for formaldehyde production equipped with a catalyst bed, characterized in that the catalyst bed has a curved structure. 2. The fixed catalyst catalytic reaction apparatus according to claim 1, wherein the vertical cross section of the catalyst bed having a curved structure is circularly curved. 3. The fixed catalyst catalytic reaction apparatus according to claim 1, wherein the vertical cross section of the catalyst bed having a curved structure is curved in an elliptical shape. 4. The fixed catalyst catalytic reaction device according to claim 1, wherein the vertical cross section of the catalyst bed having a curved structure has a circularly curved peripheral portion and a flat plate bottom portion. 5. Claim 1, in which the vertical cross section of the catalyst bed having a curved structure is curved in an elliptical shape at the peripheral part and flat at the bottom part.
The fixed catalyst catalytic reaction apparatus described in . 6. The fixed catalyst catalytic reaction apparatus according to claim 1, wherein the vertical cross section of the catalyst bed having a curved structure has a conical peripheral portion and a circularly curved bottom portion. 7. The fixed catalyst catalytic reaction apparatus according to claim 1, wherein the vertical cross section of the catalyst bed having a curved structure has a conical peripheral portion and an elliptical curved bottom portion. 8. The fixed catalyst catalytic reaction apparatus according to claim 1, wherein the vertical cross section of the catalyst bed having a curved structure consists of a plurality of different curved surface radii. 9 The degree of curvature is such that the ratio of radius R of the curved surface to catalyst bed diameter D is R:D=1:0.5 to 2, preferably R:D=1:0.
75 to 1.5, the fixed catalyst catalytic reaction device according to claim 2. 10. The fixed catalyst catalytic reaction device according to claim 3, wherein the degree of curvature is shorter axis:longer axis = 1:1.5 to 3. 11. Claim 1, wherein the fixed catalyst catalytic reaction device is a heat recovery type in which a shell-and-tube heat exchanger is provided below the catalyst bed.
Fixed catalyst catalytic reaction apparatus according to item 2, 3, 4, 5, 6, 7, 8, 9 or 10.