KR810000535B1 - Catalysts for steam reforming - Google Patents

Abstract

A catalyst comprises 10-30 wt.% Ni or NiO, 20-60 wt.% Ca or CaO, 10-70 wt.% Al or Al2O3 contg. less than 1 wt.% SiO2. The catalyst is prepd. by mixing and kneading. The starting material soaked in water, is molded and kept with catalyst compn. under a high humid atmosphere at a temp. 5≰-35≰C for >=1 day for hydrating and hardening the cement andsintering at a temp. of 550≰-1200≰C thereafter.

Description

Method for preparing hydrocarbon vapor material catalyst

FIG. 1 shows the case where the catalyst of the present invention is used for steam reforming with the calcium oxide content in the catalyst fixed at 40%, the content of nickel oxide fine particles varying from 5% to 30%, and the reaction temperature set at 950 ° C. A change in the methane content of the product gas produced.

2 shows a catalyst in which the NiO fine particle content in the catalyst of the present invention is adjusted to 15% and CaO to 40%, and NiO 18%, CaO 12%, SiO ₂ 15%, MgO 12%, and Al ₂ O ₃ 20%. Comparison of the precipitation rates of carbon when the water vapor / carbon (molar ratio) was used at 800 and 900 ° C. at reaction temperatures of commercially available catalysts.

3 shows the change in the compressive fracture strength of catalyst granules when the nickel oxide fine particle content in the catalyst of the present invention is fixed at 15% and the calcium oxide content is changed.

An object of the present invention is to provide a catalyst which is useful for producing a gaseous mixture containing, as a main component, raw material hydrocarbons as a steam material.

The steam reforming method using the catalyst of the present invention, of course, can be used conventionally used light hydrocarbons such as natural gas, ethane, propane, butane or direct-current nattha as a raw material, but conventionally Even heavier hydrocarbons, such as kerosene or diesel, can be steam reformed over a long period of time and can be converted into a hydrogen-rich gaseous mixture by use of the catalyst. It is well known that a nickel catalyst is widely used as a catalyst for steam reforming, and this nickel catalyst has a sudden deactivation due to the flow rate in hydrocarbons, and thus the transposition of a high degree of desulfurization treatment of raw hydrocarbons is indispensable. Usually, the permissible sulfur content is a low value of 0.2 ppm.

In addition, depending on the type of raw hydrocarbon or the reaction conditions, the thermal decomposition of the hydrocarbon proceeds excessively due to the high activity of nickel, and the carbon produced thereby precipitates and adheres to the surface of the catalyst to block the catalyst and reactants. It inhibits the progress of the steam reforming reaction and the reaction zone becomes a state that can be said to be a non-catalytic state. Only pyrolysis of hydrocarbon proceeds and precipitated carbon accumulates rapidly in the reaction zone, and within a short time, the reaction zone space precipitates. It is filled with carbon.

The necessity of advanced desulfurization treatment of the raw hydrocarbons, however, precipitated deposition of precipitated carbon on the catalyst surface is a fatal obstacle in the continuous catalytic gasification method. Therefore, as a means of preventing precipitation adhesion of precipitated carbon on the surface of nickel catalyst, it is devised to reduce the activity of nickel, and it is practiced to add potassium or other metal compounds to the catalyst component. It is effective in the case, but is ineffective for heavy hydrocarbon raw materials.

Improvement by addition of potassium and other catalysts of nickel catalysts may cause problems such as deterioration of the catalyst due to oxidative action of additives in addition to irrationality that lowers the activity of nickel, or adhesion of transpiration materials to low temperature parts in the apparatus. There is.

The inventors of Japanese Patent Application No. 51-5356 first provide a method for producing a non-nickel-based catalyst effective for steam reforming, catalytic partial oxidation and catalytic pyrolysis.

The catalyst of Japanese Patent Application No. 51-5356 is a catalyst containing no nickel, which is a sintered product made of an alkylide metal oxide and aluminum oxide by a specific method, and has a remarkable performance in sulfur resistance and carbon precipitation preventing ability. It is a catalyst without problems due to the transpiration of the components.

The inventors intended to further improve the activity of the catalyst of Japanese Patent Application No. 51-5356 again to further improve the activity. The present inventors examined the catalytic text to be added, experimented with the addition of various third components, and measured the effect. .

As a result, the desired high activation is achieved if the nickel oxide fine particles drawn up by a specific composition method are present in the catalyst structure of Japanese Patent Application No. 51-5356 with a content within a certain range. It has been found that even if a raw material containing a large amount of sulfur is used as an impurity, its high activity can be sustained for a long time.

High activation results in lower temperatures in the steam reforming zone or increased reaction vessel capacity and other good results, and long-term sustainability of high activity enables the use of inexpensive, low quality hydrocarbon raw materials.

The catalyst of the present invention is a raw material of the nickel component to be contained, and the nickel oxide fine particles obtained by heating a nickel compound which is changed into nickel hydroxide without impurities by heating in the presence of oxygen at a temperature within the range of 400 ° C to 800 ° C As a raw material of the calcium component to be used, a powder of a calcium compound which is decomposed and changed into calcium oxide or pure oxide without impurities by heating is used, and high purity alumina cement is used as a raw material of the aluminum component to be contained. It is combined, hydrolyzed and molded, and is cured by being held in a high humidity atmosphere at a temperature within a range of 5 ° to 35 ° C., preferably 10 ° to 25 ° C. for at least one day after molding, and curing at 550 ° after curing. At a temperature in the range of ˜1200 ° C., sintered and manufactured, the nickel component is 1 as nickel oxide based on the total weight of the catalyst. The content of silicon oxide contained in an amount in the range of 0 to 30%, the calcium component as calcium oxide in the range of 20 to 60%, and the aluminum component as aluminum oxide in the range of 10 to 70%, in particular present as an impurity The catalyst is 1% or less, preferably 0.5% or less. The active component of this catalyst is a cationic component of a calcium component and a nickel component, and these cationic components contain an aluminum component as a refractory binder for fixed bonding.

Appropriate content of the added nickel component is 10 to 30% as nickel oxide. By carrying out nickel content in this range, a catalyst acquires high activity, and by use of this catalyst, methane content in a steam reforming product gas can be kept at a low level, and a required reaction temperature can also be reduced.

The change in the methane content in the steam reforming reaction product gas when the calcium oxide content is fixed at 40% and the nickel component flow rate is changed from 5% to 30% is shown in FIG.

In this case, the test conditions include 85.9% by weight of carbon, 13.64% by weight of hydrogen, and 0.41% by weight of sulfur. The reaction conditions are 950 ° C., H ₂ O / C (molar ratio) 2.99, and a residence time of 0.06 seconds in the reaction zone. to be.

In the composition of this catalyst, when the nickel component amount is 17% or less, the residual hydrocarbon content other than methane also increases.

The fuel for imparting a nickel component to this catalyst is specially formulated separately prior to mixing with other raw materials, but this is dehydrated by heating the nickel compound of the nickel oxide raw material at a temperature in the range of 400 to 800 ° C in the presence of oxygen. Nickel oxide fine particles formed by the breakdown action that occurs during physical and chemical changes in the process of thermal decomposition and oxidation.

Even at a heating temperature of 400 ° C. or lower, most of those compounds that are nickel compounds and suitable for use as raw materials are decomposed to nickel oxide. However, at 400 ° C. or lower, conversion to nickel oxide is also insufficient, and binding of the raw material used The state remains, and elements other than nickel containing raw material remain rather than pure nickel oxide qualitatively.

On the other hand, the heating at 800 ° C or higher causes the independent existence state of the produced nickel oxide fine fine particles to be lost, and the nodule of the fine particles gradually progresses, and the raw material as a precursor is used. The use of the material in particular makes the significance of pyrolyzing it lose its significance.

The necessity of oxygen presence in the thermal decomposition treatment is based on nickel compounds, especially organic nickel compounds, which are heated in a reducing atmosphere under oxygen deficiency to produce metal nickel, crystals grow, nodules and organic nickel compounds. It is for preventing carbon in it from remaining and adhering to and coating the nodular nickel nodules in a semi-melted state.

Since adhesion to nickel fine particles prevents the formation of relatively stable carbon even at high temperatures, it is assumed that the nickel oxide raw material is brought into contact with an oxygen-containing gas such as air from the beginning of heating.

The nickel oxide fine particles thus prepared carefully have a melting point of about 1990 ° C., and the diameters of the fine particles in an isolated state are usually 1 micron or less and most are 0.5 micron or less.

The diameter of the nickel oxide fine particles in the catalyst of the present invention is 10 microns or less. The raw material of the nickel oxide fine particles is a substance which can be thermally decomposed in the presence of oxygen and converted into nickel oxide without generating and remaining impurities, and may be any compound, for example, inorganic nickel compounds such as nickel hydroxide, nickel nitrate, nickel sulfide, Organic nickel compounds such as nickel foreign acid, nickel acetate, nickel oxalate and the like can be used.

Calcium oxide, the most important component of this catalyst, promotes the steam reforming reaction, has an excellent effect on preventing carbon deposition, and no detoxification by sulfur in the raw hydrocarbons is seen.

Therefore, in this catalyst, the calcium oxide is not a small amount that is mixed with the carrier manufacturing material as one component of the carrier as in a conventional catalyst, but in an amount in the range of 20 to 60% based on the total weight of the catalyst. It is contained.

The relationship between calcium oxide content and carbon precipitation amount is shown in FIG. The catalyst given the measured value in FIG. 2 contains 15% of nickel oxide and 18% of nickel oxide. In the case of the reaction temperature of 800 ° C and 900 ° C, the raw material hydrocarbon is the same diesel oil as in the case of FIG.

In the case of calcium oxide content 30% and H ₂ O / C (molar ratio) 3.0, carbon precipitation is not seen, and in calcium oxide content 50% or more, carbon precipitation disappears even when H ₂ O / C (molar ratio) 1.5.

3 shows the change in the compressive fracture strength of the sintering catalyst when the nickel oxide content is fixed at 15% and the calcium oxide content is changed. It is the strongest in the case of 20% of calcium oxide content.

The raw material for the calcium oxide in the catalyst may be a calcium compound that is thermally decomposed by high temperature during the final sintering during the catalyst manufacturing process so that no powder is formed and is converted into calcium hydroxide. At high temperatures, nickel oxide and aluminum oxide are easily combined to form nickel aluminate, but this is a low-active component for steam reforming, which is produced during catalyst buildup during use of catalysts that have been placed at elevated temperatures for a long time, and the amount gradually increases. Although it increases, it significantly lowers the activity of the catalyst, but since the catalyst of the present invention is already firmly bound to a large amount of calcium oxide as described above, the binding of nickel oxide and aluminum oxide is suppressed, and the activity of this catalyst is not lowered. Do not.

For this reason, it is necessary to contain 20% or more of calcium oxide in the catalyst.

Aluminum oxide is used to impart the required mechanical strength as a shaping catalyst granulation, but it is introduced into the catalyst as high purity alumina cement. Alumina cement is used at least 8% by weight of the combination. It is generally noted that the presence of silicon oxide in the composition of high strength refractory is effective. However, when silicon oxide is contained in this catalyst, the ability to reject precipitated deposition of precipitated carbon on the surface of the catalyst is significantly reduced.

Therefore, the alumina cement used as a raw material of this catalyst consists only of aluminum oxide and calcium oxide, and selects and uses the thing with the low impurity especially silicon oxide content.

The inclusion of silicon oxide not only causes a decrease in precipitated carbon rejection ability, but also generates nickel silicate, nickel aminosilicate, nickel calcium silicate, and the like which are low-active components in the catalyst.

The allowable value of silicon oxide content in this catalyst is at most 1%, preferably 0.5%.

Next, the cause of the performance of this catalyst will be considered as follows.

That the content of calcium oxide as the active ingredient is kept high without reducing the mechanical strength of the molded catalyst granules; In the conventional catalyst, since the nickel component, which is an active ingredient, is present as one component of the precursor material which is used as a raw material until the final stage of the catalyst production process, it is necessary to perform the baking at the final stage of catalyst production or at a high temperature at the beginning of the use of the catalyst. As a result, since unnecessary components other than the active ingredient in the precursor material are released out of the catalyst structure, the surrounding tissue of the active ingredient becomes hollow and the fixation state of the active ingredient particles in the catalyst structure becomes poor. In this regard, since nickel oxide fine particles which are stable at a high temperature when a catalyst is used in advance are introduced into the sidewall structure, the degree of porosity of the catalyst structure around the nickel oxide fine particles is low, and the nickel oxide fine particles settle in the structure and are eliminated. Difficult and close to nickel oxide fine particles That there is a calcium oxide particles is the state that exists in a large amount; In the catalyst of the present invention, it is not possible for the catalyst of the present invention that the unnecessary component remains partially on the surface of the catalyst and becomes a nucleus with precipitated carbon when the conventional catalyst is insufficiently released in the precursor material. ; In the catalyst of the present invention, nickel oxide has a high degree of fine granulation and is homogeneously distributed in the catalyst structure by mixing with other catalyst raw materials; And silicon oxide and other harmful impurities are regulated, so that the content of the active ingredient is high; Etc. can be mentioned.

In addition, a coprecipitation method of a precursor material containing an active ingredient and another material, for example, a carrier former material, or a method of immersing a carrier material in a solution of the precursor material, which are frequently used in the preparation method of a conventional catalyst; Likewise, when the blending of the active ingredient is performed by a wet process, precise control of the blending is difficult, and the variation in catalyst quality is large, and the reproducibility of the performance is low. However, in the catalyst of the present invention, the raw material combination has a dry raw material and is precise. Quality control is assured.

It is extremely important in practice that the catalyst has sufficient mechanical strength with its activity, but this catalyst is added with the strength produced by hydration hardening by alumina cement, and is sintered again at a higher temperature than when the catalyst is used. The bonding state between the component particles is strengthened by the hot solid phase reaction of the particles.

It should be noted that the nickel component in this catalyst is not inactivated by sulfur, which is an impurity in hydrocarbon raw materials, and the cause of the investigation should be delayed in the future. It seems to be large by the influence of.

According to the above-mentioned performance, by using the conventional catalyst, even if the reaction conditions are changed, heavy sulfur-containing heavy hydrocarbons are also used by this catalyst, even if a large amount of precipitated carbon is not produced, thereby making it a raw material for steam reforming reaction. It is possible to carry out steam reforming of heavier hydrocarbons at a reaction temperature in the range of 700 ° C to 1000 ° C under normal pressure to pressurization, so that a gaseous mixture mainly composed of hydrogen is produced continuously for a long time.

Next, the manufacturing process of this catalyst is demonstrated concretely.

The nickel oxide fine sand (diameter 10 microns or less), the calcium oxide raw material, and the high purity hydraulic alumina cement which were manufactured under the above consideration are respectively weighed precisely in a dry state, and then mixed and hydrolyzed.

In order to prevent condensation of the raw material particles due to heat generation during the kneading, a suitable kneading apparatus such as a metal brain tracker is used to quickly produce the hydrolyzed raw material combination.

3% of the total weight of the hydrolyzate before the printing is the lower limit.

After kneading, the raw material mixture is quickly formed into a desired shape such as granular, spherical, cylindrical, cylindrical, etc., but the molding method is formed by a rolling method, an extrusion method, a press molding method, an inflow method, or the like. Shall be.

A small amount of a coagulation delay agent, a dispersant, or a caking additive may be appropriately used in order to control the coagulation during kneading or to improve the homogeneity of the kneading material even if the amount of addition during the kneading is reduced.

After kneading, the molded product has mechanical strength gradually by hydration hardening, but in order to prevent heterogeneous hydration hardening of the molded product, the molded product is cured for at least one day in a high humidity atmosphere of 60% or more relative humidity at room temperature, and then 350 ° C. or less. It is dried at a temperature of and then sintered at a temperature of 1200 ° C. or lower and higher than the temperature at which the catalyst is used.

During the sintering process, the calcium compound in the molded product undergoes dehydration and pyrolysis to become calcium oxide, and the hot solid reaction is carried out in a state in which nickel oxide fine particles are dispersed and dispersed between alumina cements having good volume stability at high temperatures. This results in a firm, breathable porous body in which the fine particles of nickel oxide, calcium oxide and aluminum oxide are homogeneously distributed.

The catalyst completed by the sintering treatment is a porous structure having an external porosity of 45 to 75% and a volume specific gravity of 1.0 to 1.8, and has sufficient practical strength against impact or load due to packing deposition in transport or reaction force, and in boiling water. Even if it is immersed for 1 hour or more, it does not collapse, and the hydration increase amount by this immersion is 10 to 30%, but the shape and physique do not change, and no crack occurs.

In order to better understand the present invention, examples of preparation of the catalyst and examples of its use are described below.

EXAMPLE

The basic nickel carbonate was placed in a heat resistant container, heated in an electric furnace at a furnace internal temperature of 800 ° C. for 3 hours, changed into nickel oxide fine particles, and left to cool.

The fine particles of nickel oxide were made of high purity alumina cement having 79.0% of Al ₂ O ₃ , 18.7% of CaO, 0.1% of SiO ₂ , 0.3% of Fe ₂ O ₃ , 0.4% of MgO, 1.5% of burning loss, and 97% of powder of 74 microns or less. The powder was also mixed with precipitated calcium carbonate up to 15 microns with the weight ratios in Table 1.

TABLE 1

To each combination of Table 1, methyl cellulose powder was added as a caking additive to 1 part by weight with respect to 100 parts by weight of the mixture, followed by mixing, and then 26 parts by weight of water was added and kneaded for 3 minutes by a mastitrator. The pellets were immediately molded into water pellets having a diameter of 12.5 mm and a length of 12 mm using a water-cooled extruder.

The molded product was loaded in a sealed container of 10 ° C. and a relative humidity of 80% or more to cure for 2 days, and to proceed with hydration curing.

The cured molding was dried by a preliminary heat treatment at an upper limit of 350 ° C., and then heated up to 1100 ° C. in the furnace, and maintained at this temperature for 3 hours.

The physical properties of the obtained sintered product are shown in Table 2.

TABLE 2

Using these sintered pellets as catalysts, the results of steam reforming under atmospheric pressure with 85.92% carbon, 13.64% hydrogen, and 0.41% sulfur (= 4100 ppm) of steam to carbon molar ratio of 2.99 are shown in Table 3.

TABLE 3

After this steam reforming reaction, there was no precipitation deposition of precipitated carbon on the catalyst surface at all.

Claims (1)

As a raw material of the nickel component to be contained, nickel oxide fine particles obtained by heating a nickel compound which is decomposed and changed into nickel oxide by heating in the presence of oxygen at a temperature within the range of 400 to 800 ° C are used. Calcium oxide or calcium compound which is decomposed and transformed into calcium oxide by heating is used, and high purity alumina cement is used as a raw material of the aluminum component to be contained, and these raw materials are combined, hydrolyzed and molded. After being hydrated and cured in a high humidity atmosphere at a temperature in the range of 5 ° to 35 ° C. for at least 1 day, and sintering at a temperature in the range of 550 ° C. to 1200 ° C. after curing, nickel as nickel oxide relative to its total weight Calcium oxide in the range of 10 to 30% of the component, calcium component in the range of 20 to 60% of the acid, A method for producing a hydrocarbon vapor material catalyst, wherein aluminum sulfide is contained in an amount in the range of 10% to 70%, in particular, silicon oxide in the catalyst is 1% or less.

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