JPS6261640A - Sulfur resistant methanation catalyst - Google Patents

Abstract

PURPOSE:To enhance methanating reaction activity and to prolong the life of a catalyst, by forming a sulfur resistant methanation catalyst by supporting a specific amount of Ni and Co by a carrier consisting of a specific amount of Al2O3, SiO2 and alkali metal oxide. CONSTITUTION:A sulfur resistant methanation catalyst is prepared by supporting 8-25wt% of a catalyst carrier of Ni and 20-65wt% of Ni of Co by the catalyst carrier consisting of 55-89wt% of Al2O3, 8-30wt% of SiO2 and 3-15wt% of alkali metal oxide. Further, the sulfur resistant methanation catalyst can be also prepared by supporting 8-25wt% of the carrier of Ni and 5-40wt% of Ni of Mo by the catalyst carrier consisting of 55-89wt% of Al2O3, 8-30wt% of SiO2 and 3-15wt% of alkali metal oxide.

Description

[Detailed description of the invention]

Field of application in the C1t industry] Undeveloped IJI is related to methanation catalysts with excellent sulfur resistance. Specifically, it is used for methanation of Co, CO2, and H2 mixed gases that contain trace amounts of sulfur compounds, such as coal gas and coke oven gas. The present invention relates to a methanation catalyst with excellent sulfur resistance used in the production of methanation. [Prior Art] The methanation reaction in which the catalyst of the present invention is used refers to a reaction in which a mixed gas containing CO1C02 and H2, such as coal gas or coke oven gas, is converted into methane by the following reaction. It has been widely put into practical use as a method to increase the calorific value of gas. CO+3H2→CH4+H20 CO2+41(2→CH,+2H20 By the way, N is used as a catalyst to promote the methanation reaction.
i is the most commonly used, and is usually put into practical use in the form of pellets or granules in which Ni is supported on a catalyst carrier such as alumina. However, the Ni catalyst has the problem that it is easily poisoned and deactivated by sulfur compounds, which is a factor that increases the cost required for the catalyst. In other words, coal, which is the raw rk and source of coal gas and coke oven gas, contains a large amount of sulfur compounds, so the above-mentioned gases made from coal also contain H2S, CO3, C32, mercaptan, It contains sulfur compounds such as sulfides and thiophenes, and desulfurization treatment is performed in the pretreatment process during the methanation reaction, but it is extremely difficult to completely remove sulfur compounds in the pretreatment process. Due to the sulfur compounds that could not be completely removed, the methanation activity of the Ni catalyst gradually decreases and eventually becomes deactivated. Therefore, in order to put the methanation reaction into practical use, it is very important to improve the sulfur resistance of the Ni-based catalyst and extend its life. Under these circumstances, various studies have been conducted on measures to improve the sulfur resistance of Ni-based catalysts.
9 (1979) proposes a technique for improving sulfur resistance by adding Mo or Co to a Ni catalyst. Furthermore, Japanese Patent Application Laid-open Nos. 51-10803 and 51-147491 disclose techniques for using Mo or Co as a methanation catalyst in combination with Ni. As mentioned above, it is used by supporting it on a carrier, and the most common carrier is alumina.

[Problems to be solved by the invention]

The present inventors have also been conducting research on Ni-based methanation catalysts for some time, but according to recent findings, N
It has been found that the sulfur resistance and methanation reaction activity of the Ni-based catalyst are not determined only by the component composition of the Ni-based catalyst itself, but vary significantly depending on the type of support and the amount of catalyst supported on the support. In other words, in order to efficiently carry out the methanation reaction with an excellent catalyst life, it is necessary to give sufficient consideration not only to the component composition of the catalyst, but also to the type of carrier to be combined with it and the amount of catalyst supported. However, conventional research in this type of field has only focused on the component composition of the catalyst itself, and it must be said that research that takes into consideration the combination with a support is insufficient. I don't get it. The present invention has been made in view of these circumstances, and its purpose is to provide sufficient information regarding the component m of the catalyst, the component composition of the carrier to be combined with it, and the catalyst supporting acid on the carrier. This is an attempt to provide a catalyst with excellent catalyst life and methanation reaction activity. [Means for solving the problem] The sulfur-resistant methanation catalyst according to the present invention is an Al2O3:5
A catalyst carrier consisting of 5 to 89% by weight, SiO2: 8 to 30%, and alkali metal oxide: 3 to 15%, Ni in an amount of 8 to 25% with respect to the carrier, and Co in an amount of 20 to 65% with respect to the Ni.
Alternatively, the gist is that Mo is supported in an amount of 5 to 40% relative to Ni. [Function] The present invention is characterized in that the component composition of the catalyst carrier is specified as described above, and the amounts of each of Ni, Co, and Mo supported are specified, and the reasons for these settings will be explained below. First, the A1203 that constitutes the carrier is made from, for example, aluminum hydroxide [A1(OH)3] or hydrated alumina, and when fired at 500 to 800°C, it changes to γ-A1203! Mushi. It not only acts as a carrier matrix for Ni-based catalysts, but also acts to activate the Ni-based catalysts and contributes to improving the methanation reaction rate. It must be composed of Al2O3, but if it exceeds 89%, the absolute amount of SiO2 and alkali metal oxide, which will be described later, will be insufficient, resulting in poor strength as a carrier, and it will gradually powder during use, resulting in poor breathability. becomes worse, and the progress of the methanation reaction is significantly suppressed. Moreover, when the catalyst of the present invention is used, for example, as a tube wall type catalyst (details will be described later), the carrier coating tends to fall off due to insufficient strength, making it difficult to withstand long-term use. Furthermore, SiO2 is blended as wood glass, silica gel, etc. used as a fixing agent, but if the blended amount is less than 8%, the strength of the support becomes poor and it may powder during use or may not be used as a tube wall type catalyst. If the carrier coating is removed, the carrier coating will easily fall off. However, S
If the amount of iO2 exceeds 30%, uniform dispersion during carrier preparation becomes difficult, and a phenomenon occurs in which unevenly distributed moisture evaporates in a bumping manner during the calcination process, making the catalyst support layer fragile regardless of whether it is in the form of pellets or tube walls. This reduces the lifespan. Alkali metal oxides include Na2O from water glass, which is used as a fixing agent. It is a component blended as K2O or Li2O, etc., and PXI4 with a content of 3% in the carrier has poor strength as a carrier and is likely to powder or peel off from the tube wall during use. If it exceeds 15%, the catalyst activity tends to deteriorate during long-term use and the methanation reaction rate decreases. In the present invention, as mentioned above, it is essential to contain Al2O3, SiO2, and alkali metal oxides in appropriate ranges, and if any one of the above components is omitted, or even if any one of the above components is If the content is outside the range, the intended purpose cannot be achieved. Next, Ni to be supported on the above carrier is the main component of the methanation reaction catalyst, and in order to ensure a satisfactory methanation reaction rate, Ni should be supported at 10% or more with respect to the recombination of the above carrier. However, it is extremely difficult to support more than 25% of nickel in terms of the solubility of nickel nitrate used as a Ni source in the supporting process and the water content of the carrier. Supported Ni
Phenomena such as components eluting backwards or Ni depositing in powder form on the surface of the carrier during the drying/calcination process occur, so it is not a good idea from an economic point of view or from a catalytic activity point of view. , Co or MO are indispensable elements for preventing Ni from being poisoned by sulfur compounds, and their supported amounts should be determined based on the supported amount of Ni. That is, C
An upward life extension effect cannot be obtained unless O is supported at least 20% (relative to Ni) and Mo is supported at least 5% (relative to Ni). However, if M is supported relative to the amount of Ni supported,
If o exceeds 40%, the methanation reaction rate itself tends to decrease, which is not preferable. The method for supporting Ni and Co or Mo on the carrier is not particularly limited, but the most common method is as follows. That is, (a) a support consisting of A I203, S i02 and an alkali metal oxide is mixed with Ni or CO nitrate [
Ni (NO3)2 *6H20, Co (NO3)2
・6H201 or ammonium paramolybdate [(N
It is immersed in an aqueous solution such as H4)6 Mot 02s* 4H203, heated and evaporated, and then dried under normal pressure or reduced pressure. (b) The support containing the metal salt is then heated in air to convert the metal salt to an oxide, and (c) heated in an H2''R atmosphere to reduce it to the active metal. Alternatively, (b- 2) Directly heat the carrier containing metal salts in an H2 atmosphere to decompose and decompose the metal salts.
Give back. However, in the present invention, the method of supporting Ni, Co, and Mo is not particularly limited, so it is of course possible to support them by other methods. Although the catalyst of the present invention can of course be used in the form of ordinary pellets, it is also possible to form a catalyst coating layer on the inner or outer surface of a heat exchange tube, and to conduct the mixed gas through the inner or outer surface of a chain tube. It also exhibits an extremely excellent effect as a so-called tube wall type catalyst, which is used in a method where the methanation reaction is advanced by heating from the outside or inside of the chain pipe to further increase the speed of the methanation reaction. It's something you get. [Example] Example 1 (Determination of carrier component composition-1) A stainless steel pipe (StJS316,
Using a pipe with an outer diameter of 16 mm', a coating material prepared by adding and kneading water glass and silica gel as adhesion agents to aluminum hydroxide was applied to the outer periphery of the pipe to a dry thickness of 1.0 ml, After baking this at 650℃, the coating material (
The presence or absence of falling off of the carrier (carrier) and shape defects was investigated. The results are shown in Table m1. In Table 1, S-t to S-4 show conventional examples, and T-1 to T-5 show examples of the present invention. Note that in Table 1, the O mark indicates that there is no falling off or shape defect, and the X mark indicates that there is falling off or shape defect. Table 1! The following is understood from the R1 table. S-1 is SiO
2 is outside the scope of the present invention, and S-2 has an alkali metal oxide outside the scope of the present invention, so in both cases, the strength of the coating material was insufficient and the coating material fell off. Further, in S-3, since SiO2 is outside the scope of the present invention, shape defects occur on the surface of the coating material. Furthermore, in S-4, SiO2 and alkali metal oxides are outside the scope of the present invention, resulting in drop-offs and shape defects. On the other hand, in T-1 to T-5, the compounding ratio of each compound is within the specified range of the present invention, so the coating has sufficient strength and does not fall off, and no shape defects are observed on the surface. I can't do it. Example 2 (Determination of carrier component composition-2) Effect of alkali metal oxide, which is one of the essential components in the carrier used in the present invention, on the catalytic activity (Ni alone)! was investigated for the methane production reaction. That is, after preparing a coating agent by mixing and kneading various amounts of water glass as a fixing agent with aluminum hydroxide, the coating agent was applied to a stainless steel pipe (SUS31 B, outer diameter 12 l-) and heated at 650°C. It was fired in After Ni was supported as a catalyst on the obtained support layer by the method described above, a methane production reaction was carried out under the following conditions, and the methane production rate was measured. The results are shown in Figure 1. (Conditions for methane production reaction) Gas composition: H55%, CH430% balance C01CO2, N2 Reaction temperature: 300-500°C Gas flow N 21. OXm' /hr As understood from FIG. 1, as the blending ratio of alkali metal oxide increases, the methane production rate decreases, and there is a tendency for the methane production rate to decrease as time passes. In particular, when the alkali metal oxide content is 16%, 15%
After 0 hours, the methane production rate is 0.4%, which is not much different from the thermal spraying method, and the significance of the present invention is no longer recognized. For this reason, in the present invention, the upper limit of the blending ratio of the alkali metal compound is set at 15% by weight. Example 3 (Determination of carrier component composition-3) Furthermore, the present inventors conducted an experiment to clarify the relationship between the content of Al2O3 in the carrier layer and the methane production rate. The conditions for packing and firing were basically the same as in Example 2, and several types of tube wall catalyst supporting layers with different amounts of Al2O3 were formed, and after supporting each of them a single Ni catalyst in the same manner as above, methane production was performed. The reaction was carried out. Figure 2 is a graph showing the results, which was obtained by IF after 5000 hours, and it is found that if Al2O3 is less than 60%, the methane production rate cannot be significantly increased, and the purpose of the present invention cannot be achieved. In other words, it is an essential requirement for increasing the catalyst activity that the Al2O3 content in the coating material be 60% by weight or more. Example 4 (Comparison with general alumina) Neobed C-4 (A
l203: 99.8%, 5t02: 0.2% granular 3m-, BET surface area 139m2/g) and a carrier that meets the requirements of the present invention (A1203: 80%. 5L02: 15%, Na2O: 551 cylindrical 2amφX
5 mm, BET surface area 69 s 27 g), each carrier was loaded with 10% Ni according to a conventional method, and then a methanation reaction was carried out under the following conditions to produce each methane*(
(vs. equilibrium carbon equivalent). Methanation reaction conditions Temperature: 400°C Reaction gas: N2/C0=3.0, 241/h
As a result, the methane production rate when using a commercially available alumina-based carrier was 72%, whereas the methane production rate when using a carrier that met the requirements of the present invention was 100%. That is, when a carrier having the component composition specified in the present invention is used, a very high methane production rate is obtained even though the BET surface area is about the same as that of a commercially available carrier. It can be seen that the carrier can effectively enhance the methanation reaction activity of the NE catalyst. Example 5 (Influence of the amount of Ni supported on the carrier) An A1203-S i02-Na20 carrier layer having the same composition as that used in Example 4 was applied to the surface of a SUS 304 pipe material having an outer diameter of 61 mm by approximately 0.51 mm. The carrier coating layer was made to carry Ni in the amount shown in Table 2, and a methanation reaction was carried out under the following conditions. The length of the catalyst layer adopted in each experiment and the obtained methane production rate are summarized in Table 2. Reaction conditions> Reaction gas set ffl: H2 = 53%, CH4 = 31%, C
0=7%, C02=5%, N2 richness 4% Reaction gas pressure crab 2. Okg/c+s2G reaction gas flow N
: 1.5
If the supported amount is 8% or more, a satisfactory methane production rate can be ensured. However, when the amount of Ni supported is less than 8%, the methane production rate can only be as low as 3% or less. On the other hand, if the amount of Ni supported is more than 25%, as mentioned above, the efficiency during the supporting treatment using Ni nitrate etc. will be significantly reduced, and the supported form will also deteriorate, making it difficult to obtain stable catalytic activity. Considering practicality, the upper limit of the amount of Ni supported is considered to be about 25%. Example 6 (Ni catalyst #j with sulfur compound) Using a granular catalyst (Ni supported 1i:l.%) prepared in the same manner as in Example 4 using a carrier that satisfies the requirements of the present invention, a sulfur compound was used. The catalyst poisoning situation when using H2S was investigated. However, the methanation reaction temperature is 350
℃, raw material gas is N2/C0=3.0 (61
/hr), and the degree of poisoning was investigated from the methane production rate before and after #i exposure to H2S gas. However, in the following examples, the methane production rate was increased by setting the reaction gas flow rate to about 7 x 10-' m/sec and lengthening the residence time in the catalyst layer. The results are shown in Table 3 below, and the methanation residue of the Ni catalyst rapidly decreased by contact with H2S, reaching 0.51.
The methane yield was reduced to about 8% by the addition of H2S at 1, and the recovery rate was drastically reduced to about 0.01% by the addition of H2S at 11. Example 7 (Poisoning Suppression Effect by Co) A granular catalyst was produced in the same manner as in Example 6, except that 10% Ni was supported on the carrier and 5 to 100% Co was supported on the Ni, and the same procedure was carried out. The methane production rate before and after catalyst poisoning with H2S was examined in the same manner as in Example 6. The results are shown in Table 4 and Figure 3, and when an appropriate amount of Co is supported along with Ni, the poisoning of the catalyst is significantly suppressed.
When used in combination, the reduction in methane production rate can be suppressed to 50% or less when H2S = 0.51 contact, and to 90% or less when H2S = 1 ml. Moreover, the initial reaction activity of methanation itself is hardly affected by Cod, and a substantially constant value is obtained. Table 4 Example 8 (Poisoning suppression effect by Mo) 10% Ni to carrier and 5 to 50% M to Ni
The methane production rate before and after the catalyst poisoning with H2S was investigated in the same manner as in Example 7 except that o was supported. The results are shown in Table 5 and Figure 4. Poisoning of the catalyst was significantly suppressed when an appropriate amount of Mo was supported together with Ni, especially when Mo was used in an amount of 5% by weight or more based on the amount of Ni supported. In this case, the decrease in methane production at< after contact with H2S can be significantly suppressed. However, the mutual amount of Mo is N
If it exceeds 40% of the amount of i, the initial methanation activity of the entire catalyst tends to deteriorate significantly, so the amount of Mo supported should be suppressed to 40% or less. Table 5 [Effects of the Invention] The present invention is configured as described above, but the important point is to specify the component composition of the carrier, and also to determine the amount of Ni supported on the carrier and the amount of Co or MO.
By strictly regulating the supported amount of each, it not only shows a high level of initial methanation reaction activity, but also exhibits excellent poisoning resistance against sulfur compounds and maintains high methanation reaction activity. It was possible to provide a catalyst. As explained above, the catalyst of the present invention is particularly suitable as a tube wall type catalyst, but because the structure of the tube wall type catalyst means that the catalyst is fixed inside the reactor, it cannot be replaced. However, it is always difficult. On the other hand, it has the characteristic that the amount of catalyst used per unit volume of the reactor is smaller than that of ordinary granular catalysts, but the present invention suppresses poisoning of the catalyst and extends its life. Since the frequency of replacing the catalyst can be drastically reduced, maintenance efficiency can be greatly improved even when it is put into practical use as a tube wall type catalyst, and its features can be effectively utilized. Regardless of the shape of the catalyst, such as pellets or granules, improving the sulfur resistance of the catalyst can reduce the required capacity of the desulfurization equipment installed before and after the methanation equipment, and in turn, simplify the desulfurization process itself. You can also enjoy benefits such as:

[Brief explanation of the drawing]

Figure 1 shows the case where the amount of alkali metal oxide in the carrier is changed (
Figure 2 is a graph showing the relationship between the Al2O3 content in the carrier and the methane production rate, and Figures 3 and 4 are graphs showing the relationship between the amount of Co or Mo supported and the H2S coverage. It is a graph showing the relationship between poison suppression effects.

Claims (2)

[Claims] (1) Al_2O_3: 55-89% by weight (hereinafter simply %
), SiO_2: 8 to 30%, and alkali metal oxide: 3 to 15%.
A sulfur-resistant methanation catalyst comprising 25% Ni and 20 to 65% Co supported on the Ni. (2) Al_2O_3: 55-89% by weight, SiO_2
: 8 to 30%, alkali metal oxide: 3 to 15%, Ni in an amount of 8 to 25% with respect to the carrier, and the N
A sulfur-resistant methanation catalyst characterized by supporting 5 to 40% of Mo based on i.