JPS6012905B2 - Methanation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nickel catalyst suitable for use in a process for producing methane-rich gas by reacting hydrogen with carbon oxide.

In recent years, such methanation processes have been used extensively for various purposes.

The methanation process is an important step for the production of gaseous fuels, especially from solid as well as liquid fuels. In this process, carbon and petroleum products can be converted to natural gas substitutes by a gasification process followed by a methanation process. In the methanation process, methane formation is carried out according to the following reaction formula: [1) 3 days 20 CO → CH4 10 days 20'2} 4 days 20 CO2 → C ratio + 2 days 20 above {
Both reactions 1) and [2} are highly exothermic reactions,
In the presence of a suitable catalyst it usually proceeds to equilibrium.

The equilibrium composition of the product gas and the corresponding adiabatic temperature rise depend on the composition and temperature of the introduced gas and on the operating pressure. Typically this temperature increase is between 200 and 400 degrees. According to reaction equations [1] and (1), high operating pressures and low outlet temperatures are favorable for methane formation.

However, these operational variables cannot be selected independently or arbitrarily. The operating pressure is usually selected relative to the pressure that can be applied to the methane synthesis gas or the pressure at which the methanation product is used. For a given operating pressure, the outlet temperature can be adjusted by adjusting the temperature and composition of the inlet gas. Adjustment of the composition can be carried out, for example, by recycling the product gas and/or by adding steam. The temperature of the introduced gas is usually selected to be at least a minimum temperature for the catalyst to have a reasonably high activity. From the above description, it can be seen that a suitable methanation catalyst has good activity at the low temperature indicated at the inlet end of the catalyst bed and good activity at the high temperature indicated at the outlet end of the catalyst bed. It will be understood that the material must be highly resistant.

But there is another important requirement. Even after being exposed to high temperatures during long-term operation, the catalyst must still have reasonably good activity at relatively low temperatures. This is because most of the reaction in the methanation reactor takes place in a narrow zone in the catalyst bed.
This narrow band gradually moves through the catalyst bed due to the unavoidable catalyst deactivation due to poisoning by the dawn and in particular by sulfur and the like. This means that a cross-section of the catalyst bed at a distance from the inlet, approximately corresponding to the length of the reaction zone, is initially operated at a temperature close to the high temperature exhibited at the outlet end of the catalyst bed. It means to do something.

In this situation, all remaining portions of the catalyst bed following the reaction zone are exposed to this elevated temperature, but virtually no reaction is occurring in these portions. but,
After a certain time, the active zone in which the methanation reaction takes place moves forward in the catalyst bed due to gradual deactivation; as a result, the catalyst, which was initially operated at high temperature, moves forward in the catalyst bed. The section must then be operated at a relatively low temperature; in other words, a good catalyst for the methanation process is It must have a high degree of activity and good stability at the high temperatures encountered at the outlet end of the catalyst bed.

These properties allow the catalyst to operate at lower temperatures after being exposed to elevated temperatures for extended periods of time. One way to obtain improved stability at high temperatures is to use an improved catalyst as described in Japanese Patent Application No. 50-80577 (Japanese Patent Publication No. 58-43141).

According to the above, it consists essentially of nickel and a porous support, the content of nickel being between 15 and 40% by weight, calculated as nickel oxide, relative to the total weight of the catalyst, and the support material being 0.05% by weight. A catalyst consisting of zirconia and alumina in a weight ratio of 1:1 and 2:1 is used. However, the inventors have now discovered that a catalyst having a composition as defined below has even better stability and increases the usable life of the catalyst. The present invention has an increased pressure and an inlet temperature of 230-27000, 580-610
At an outlet temperature of 0.25-15% by weight
The present invention provides a method for reacting hydrogen with carbon oxide to form methane in the presence of a catalyst.

The active component of the methanation catalyst is metallic nickel, which is usually obtained by reduction of nickel oxide.

The term catalyst is used herein for those in which nickel is present as a metal or as an oxide. For practical reasons, the chemical compositions given here relate to the catalyst in its oxidized state. In the methanation catalyst, the nickel oxide can be chosen among the oxides of aluminum, zirconium, magnesium, titanium, silicon, chromium or mixtures or formulations of these oxides for the catalyst according to the invention. distributed on an oxide support material. Nickel can be deposited on such carrier materials in various ways, for example by impregnating the nickel compound onto a preformed carrier material, or by co-precipitating the nickel compound with the carrier material and then tableting or applying suitable catalyst particles. It may be distributed or incorporated by shaping by any other method for shaping. Irrespective of the manner in which the catalyst is prepared, the oxidic material mentioned above may be considered as a support material or support material which provides the physical structure to support the main component involved in catalysis, namely nickel or nickel oxide, and as such. Function.

That is, even when the catalyst components are prepared by coprecipitation, it is correct to consider these oxide materials as carriers for Nj and/or Ni○. After the catalyst particles are formed,
Nickel compounds are converted into oxides by baking.

In fact, all the conventional methods used for catalyst production are suitable for introducing the nickel compound and converting it to nickel oxide. The concentration of nickel oxide in the catalyst according to the invention is essentially the same as that of conventional methanation catalysts.

To obtain adequate activity, its concentration is usually at least 1
% by weight, preferably at least 2% by weight. On the other hand, its maximum concentration is approximately 4% by weight for economic reasons.
, preferably at most 35% by weight. The molybdenum present in the catalyst according to the invention can be introduced in various ways.

It is suitably introduced into conventional catalysts by immersion in a solution containing the dissolved molybdenum compound. Molybdenum compounds suitable for use in the immersion solution are the various ammonium molybdate classes that are readily soluble in water. After soaking and drying, the catalyst must be subjected to a reduction treatment before it can be used in the methanation process.

Also, if the catalyst is immersed in a reduced state, it must be reduced after immersion in order to convert the volatile molybdenum compounds to non-volatile molybdenum. Whether the molybdenum compound is completely reduced to the metal and present in that form in the catalyst, or dissolved in or combined with nickel, or partially reduced and lower It is not known whether molybdenum in the form of molybdenum oxide is bound to an oxide support. It has been found that low concentrations of molybdenum have a beneficial effect on the stability of the catalyst, even at molybdenum concentrations of 0.3% cloud cover.

The concentration for this is a minimum of 0.25% by weight. As the concentration of molybdenum increases, the stability increases progressively. On the other hand, increasing the amount of molybdenum appears to reduce the initial activity of the catalyst. In order to select the best concentration, the specific external conditions under which the catalyst is used must be considered. However, for reasons set forth in Example 5 below, the concentration of molybdenum must be below 15% by weight. The concentration of molybdenum is advantageously between 1 and 8% by weight, in particular from 2 to 6% by weight, such as from 3 to 5% and very preferably 4% by weight, calculated as metal relative to the total weight of the catalyst. It turned out to be. A particularly suitable catalyst according to the invention is obtained by soaking the catalyst composition described in Japanese Patent Application No. 58-143141 in an aqueous solution of ammonium molybdate. The preparation of such catalysts is illustrated in Examples 1 and 2 below. However, the present invention is not limited to the catalyst compositions and methods for producing them described in these examples. Example 1 A nickel catalyst used for comparison and designated Catalyst E was prepared without molybdenum as follows: 14.5% in concentrated nitric acid (62% by weight) in a customer precipitation tank. and 100% deionized water.

The suspension is heated to 50°C and strained for 2 hours.
Then add another 2500 g of deionized water. In a separate container, add 95.6k9 aqueous carbon zirconyl paste (47% Z2) to 82.0% concentrated nitric acid (62% by weight).
dissolve in

The obtained zirconyl solution was mixed with 222k9 nickel nitrate N.
i(N03)2.Add to the above alumina suspension together with 20. After the nickel nitrate is completely dissolved, ammonium bicarbonate 267×9 is added slowly to precipitate the carbonate of the metal ion. Finally, fill the sedimentation tank with deionized water and soak for 2 hours. The precipitated metal carbonate and alumina hydrate were separated, dried and 400q.
The corresponding oxide is obtained by annealing at o.

The resulting powder is mixed with 3% by weight of graphite and 2% by weight of cellulose powder and then compressed into tablets having nominal dimensions of 4.5 feet high and 4.5 sides diameter. These tablets are calcined at 960qC for 3 to 4 hours. The resulting catalyst E has approximately the following chemical composition: Nj03
2% by weight, AI20342% by weight, and Zr0226% by weight.

A small amount of this catalyst E was reduced for about 2 hours at 800 qo in a stream of hydrogen passed through the catalyst at a space velocity of 1000 N/s (catalyst)/hr. This sample of reduced catalyst E is
Used in the methanation tests described in Example 3. The remainder of Catalyst E was used to prepare Catalysts F, G and Day as described in Example 2. Example 2 A series of catalysts designated as Catalysts F, G and Day were prepared in accordance with the present invention as follows: soaking solutions of various molybdate concentrations were mixed with ammonium molybdate (N ratio) 6Mo702
It was prepared by dissolving 4.4 Day 20 in water.

A sample of Catalyst E (Example 1) was soaked in this solution for approximately 2 hours. The soaked catalyst sample was taken out of the solution and
It was dried at zero temperature and then reduced as described for Catalyst E in Example 1. After cooling in hydrogen,
The reduced catalyst samples were analyzed for molybdenum.

The concentration of the soaking solution and the molybdenum concentration of the reduced catalyst sample are shown in Table 1. Reduced samples of Catalysts F, G, and Day were used in the methanation tests described in Example 3. Example 3 Reduced samples of catalysts E, F, G and Day prepared as described in Examples 1 and 2 were subjected to a deactivation treatment and the methanation activity of the catalysts before and after treatment was determined. .

The conditions selected for the deactivation treatment were more severe than those normally used in methanation processes.

By this method, the rate of catalyst deactivation is greatly increased and significant differences in catalyst stability are quickly and clearly demonstrated. In the deactivation treatment, a sample of the catalyst was heated to 700 oo
10 field hours and 6 hours at a temperature and 3 absolute pressures, respectively.
Treated with gas flow (233% by volume per day, 2067% by volume per day) during 0 field hours.

The temperatures used in this process as well as the partial pressures of the gas streams are higher than normal operating conditions for methanation processes. Both of these elements have a promoting effect on the deactivation of the methane catalyst. The methanation activity of the catalyst samples was determined before and after deactivation treatment by the following standard test method: The catalyst tablets were crushed and
．． Approximately 0.5 fractions of separated particles with a particle size of 3 to 0.5 ribs were collected for testing.

This catalyst fraction is placed in a vertical reaction vessel with an internal diameter of 8 ribs. At normal pressure, a gas flow (Q99 volume % + COI volume %
) to keep the catalyst in a fluid state. The gas stream and catalyst temperatures are maintained at temperatures selected to provide a methane concentration in the gas stream that is easily measurable with good accuracy. Based on such a measurement method and knowledge of the activation energy of the methanation reaction, the standard catalyst activity corresponding to 250 qo can be easily calculated. This standard activity is 25,000 per hour for catalyst 1.
Normal liter of methane produced in (N/C)
It is expressed in units of (ratio/hr/evening). The results of such tests performed on reduced samples of Catalysts E, F, G and Day before and after deactivation are shown in Table 01. As is clear from this result, the addition of molybdenum to the methanation catalyst itself has a slight deactivation effect.

However, after deactivation, molybdenum-containing catalysts have much higher activity than molybdenum-free catalysts. Table I Table 11 For the use of the catalyst compositions according to the invention, preference is given to using them in processes for methanating gases with a high content of carbon oxides and hydrogen.

Gases suitable for such processes can be obtained by gasification of coal or petroleum products, for example by partial oxidation. Another example for obtaining feedstock gases suitable for methanation is the steam reforming of gaseous or liquid hydrocarbons. As already explained above, it is essential that catalysts for the methanation of such gases have a high degree of activity at relatively low temperatures and good stability at high temperatures. be.

This is necessary because the catalyst must still be active at low temperatures even after being exposed to high temperatures for long periods of time. The catalyst according to the invention is particularly suitable for such conditions. This catalyst has 230 and 270
It has a high enough activity to give a reasonably fast reaction at temperatures of 0.00 to 0.00. On the other hand, the stability of the catalyst at high temperatures is also very good. This means spots 0 to 6
Even after long hours of operation at temperatures of 10°C,
This means that it has sufficient activity to operate at temperatures between 230 and 270q0. The suitability of this catalyst is illustrated in pilot plant experiments as described in Example 4. This experiment was conducted so that the improved stability of molybdenum-containing catalysts could be compared to the stability of conventional catalyst compositions that do not contain molybdenum. For this pilot plant experiment, the catalyst was reduced essentially as described in Example 1, but at a hydrogen hourly space velocity of 2000.

This higher space velocity was used because it was found that in order to obtain good activity it was important that the reduction was carried out in a hydrogen stream containing less than about 2% water by volume. . It is possible to keep the concentration of water formed by reduction below this limit by increasing the rate of hydrogen appropriately.

Example 4 Test number no. Pie called 1.

A pilot plant experiment was conducted in a pilot plant that mimics the conditions of an industrial scale adiabatic methanation reactor vessel and with product gas circulation. The circulation of the product gas (together with the steam it contains) is
One method available is to maintain the temperature at the outlet end of the catalyst bed at a value suitably below that at which rapid deactivation of the catalyst occurs. The pilot plant has an inner diameter of 50 mm and an overall length of 2.
It has a tubular reaction vessel made of heat and pressure resistant alloy with 8 skins.

The catalyst bed contained in this reaction vessel has a height of 1.73 mm and its total catalyst volume is 3.5 mm. The reaction vessel is equipped with an electric heating element to compensate for heat loss to the surroundings. By appropriately adjusting the current passing through this heating element, true adiabatic conditions can be approached even further. Test number no. In No. 1, two different catalysts were used.

Molybdenum-free catalyst E prepared as described in Example 1
was used for comparison. Catalyst 1 containing molybdenum according to the invention was prepared by soaking unreduced catalyst E in ammonium molybdate solution as described in Example 2.
However, in this case, a high concentration was used, giving the reduced catalyst 1 a molybdenum concentration of 1.8% by weight. Test number no. Test 1 was conducted in two periods,
A portion of the catalyst was replaced between these two periods. During the first period (0-1612 hours of operation) the first layer was catalyst E (no molybdenum), the second layer was catalyst 1 (containing molybdenum) and the third layer was catalyst E (molybdenum-free). ). After the first period of operation, approximately 10
The entire catalyst bed was sectioned and taken out so that the position of each section of the height of the cathedral could be distinguished.

In this way, a small test sample can be taken from a location on the catalyst bed. Each section of catalyst was then refilled in its original position in the methanation reactor vessel, except that catalyst E (containing no molybdenum) from layer 1 was replaced with all unused catalyst 1 (containing no molybdenum). (including). This catalyst arrangement was used during the second period (1612 to 62 hours of operation).
used during. After the second period of operation was completed, the entire catalyst bed was again removed in sections to allow for the location of each reaction layer of about 10 heights, and samples for testing were again taken from one location. .

Details of the operating conditions during these two periods are shown in Table m.

After the first period and after the second period, catalyst samples taken from certain locations on the catalyst bed were subjected to the standard test method described in Example 3. The results of these tests are shown in Table W. Table M Table W In Table W the test results are shown separately for samples obtained after two running periods.

In the first period, all samples were run for 161 hours. In the second period, some samples were operated for both periods, ie 386 bait hours, while one of the samples was operated for only the second period, ie 225 bait hours. The operating temperatures shown in the table are typical during various periods. However, during operation, there are of course some temperature fluctuations. Regarding the initial activity of the samples, the results confirmed that the presence of molybdenum had a tendency to reduce the activity.

The results also show that more favorable reducing conditions result in higher initial activity. This becomes clear by comparison with the results shown in Table 0 for more unfavorable reduction conditions. Regarding activity after operation, these results confirm that molybdenum-containing catalysts have improved stability.

However, it should be noted that comparisons are only valid if results obtained from samples treated essentially the same way are compared. This is probably due to some catalytic capping effect, although it is otherwise affected by other factors for unknown reasons. For example, samples taken from the 160 and 170 skin positions are treated almost the same way.

After both periods of operation, the molybdenum-containing catalyst has an activity that is essentially higher than that of the molybdenum-free catalyst, ie 5 and 3 times higher, respectively. Similarly, samples taken from 5 skin locations showed that the molybdenum-containing catalyst after 225 field hours of operation had an activity that was approximately 3 orders of magnitude higher than the molybdenum-free catalyst after 161 field hours of operation. Indicated.

Example 5 A series of catalysts marked J, K, L, M, N and others marked with O are prepared according to the invention by soaking catalyst E in thickening solutions containing various ammonium molybdates. did.

The catalyst obtained has a molecular weight of 0.25 to 8. with a molybdenum concentration in the range of wt%Mo. These series of catalyst samples were reduced with Catalyst E (for comparison purposes) in a stream of hydrogen as described below.

To obtain optimal reduction conditions, the heating rate and hydrogen space velocity (sp.v.) were controlled as follows: 0-3 hours: heating to 600°C from 20°C, sp. v. 2000
3 to 4 hours: Kano, Sp. from 600 to 850°C. v.
40004-6. Curing period: Stored at 850°C, sp. v.
40006.0-6. Insect time: cooled from 850 to 600oo, sp. v. 20006.5-1q hours: Cooled from 600°C to 20qC in nitrogen. The reduced catalyst sample is Example 3.
The deactivation treatment was carried out under the conditions described, provided that the gas stream treating the sample had the following composition: ratio 31
．． 2%, C03.7%, C025.0%, CH432.
6% and day 2027.5%. The methanation activity of the catalyst samples was determined before and after treatment using the standard test method described in Example 3.

The results of these tests shown in Table V are: 0.25 None, 8%
It has been shown that a molybdenum concentration in the range of . Table V

Claims (1)

[Claims] 1 elevated pressure and inlet temperature of 230-270 °C,
At an outlet temperature of 580-610°C, a catalyst consisting of an oxide support material, nickel and molybdenum, in which the concentration of nickel is 10-40% by weight, calculated as oxide, and the concentration of molybdenum is 10-40% by weight, calculated as oxide. Calculate 0.25
A method of reacting hydrogen with carbon oxide to form methane in the presence of a catalyst of ~15 wt.