JPH0243952A - Catalyst for steam modification - Google Patents

Abstract

PURPOSE:To obtain a catalyst for steam modification whose activity is not lowered even under a condition exposed to high temp. by immersing an alpha-alumina porous body having specific properties in a nickel-containing aqueous solution and subsequently drying the impregnated porous body naturally before baking the same. CONSTITUTION:As a carrier of a catalyst for performing the steam modification of hydrocarbon to prepare a hydrogen/carbon monoxide-containing gaseous mixture, an aluminum oxide porous body wherein a pore volume of a pore size of 0.1-0.5mum is 0.2ml/g or more, a pore volume of a pore size of 0.5mum or more is 0.05ml/g or more and purity after ignition drying is 98wt.% or more is used. This porous body is impregnated with a nickel-containing solution to be dried and baked. Nickel is contained in an amount of 3-30% by wt. or the whole of the catalyst as nickel oxide. The catalyst thus obtained is stable to heat and not lowered in its activity even under a condition exposed to high temp. of a certain degree or more.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a catalyst used for steam reforming hydrocarbons and the like to produce a mixed gas containing hydrogen and carbon oxide.

[Conventional technology and its issues]

It is already known to use a heat-resistant carrier such as alumina or silica for steam reforming of hydrocarbons and the like, and to use a catalyst containing nickel as a main component for catalytic activity. However, these catalysts, which are active at low temperatures, are very unstable with respect to heat, and have the disadvantage that their activity decreases when exposed to high temperatures above a certain level.

[Means to solve the problem]

As a catalyst to solve these drawbacks, the applicants previously proposed in Japanese Patent Publication No. 57-50533 that nickel oxide was supported on an active alumina porous material mainly made of T-alumina obtained by firing boehmite gel. proposed a steam reforming catalyst for the production of fuel gas containing methane as the main component, but later on this type of catalyst was developed for the production of hydrocarbon and lower alcohol steam reforming catalysts for the production of gas containing hydrogen and carbon monoxide as the main components. We considered its use in reforming.

That is, various catalysts were prepared by changing the porous properties of this activated alumina porous material, and experiments were conducted to precisely compare the catalytic activities. The properties of the porous material were changed by changing the heat treatment temperature of the activated alumina porous material.

As a result, a high-purity aluminum oxide porous body is obtained using boehmite alumina as a starting material, which becomes α-alumina through T-alumina and δ-alumina through heat treatment, and has an apparent porosity of 50 to 80%, preferably 50 to 80%. 70% porous structure, the pore volume within the range of pore diameters of 0.1 to 0.5 m is 0.2 mZ/g or more, and the pore volume of pore diameters of 0.5- or more is 0.05 m/g The above, α-alumina containing 98% by weight or more of aluminum oxide as an active component, 3 to 20% by weight, preferably 5 to 15% by weight of nickel based on the total weight of the catalyst, in terms of nickel oxide, It has been found that a catalyst containing preferably 5 to 10% by weight has excellent performance in the steam reforming of hydrocarbons and the like, which is the object of the present invention. The conversion temperature to α-alumina is said to be about 1150 to 1200°C,
The heat treatment temperature for obtaining the catalyst carrier used in the examples below was 1.
The temperature was about 40°C. This heat treatment is preferably 1
200-1380°C, more preferably 1250-135
It is done at a temperature of 0°C. Generally, at temperatures lower than this, the carrier has many small pores and a large surface area, and conversely, at temperatures higher than this, the number of small pores decreases and the surface area becomes small, making it difficult to obtain a carrier suitable for the present invention. The heat treatment for converting into α-alumina is performed in an oxidizing atmosphere such as air.

The conversion treatment is carried out for a sufficient period of time, usually 3 to 5 hours, preferably 2 to 4 hours, by giving appropriate temperature raising and cooling times before and after.

Also, the upper limit of the pore volume within the range of pore diameter 0.1 to 0.5,
There is no particular upper limit for the pore volume with a pore diameter of 0.5- or more, but it is 0.5 m1. /g or less and 0.3 ml/g or less is preferable in order to keep the apparent porosity within the above-mentioned preferred range and to make the compressive strength of the carrier and thus the catalyst of the present invention suitable for practical use.

α-Alumina is fused alumina or bayerite,
It can also be obtained by firing alumina trihydrate such as gibbsite, but since the alumina obtained in this way generally cannot have the pore structure specified above, it is difficult to obtain the desired activity using these as a carrier. I can't.

The catalyst of the present invention is suitable for reforming lower hydrocarbons such as methane and lower alcohols such as methanol, and is particularly suitable for lower hydrocarbons.

The means for adding the nickel component to the α-alumina porous material used as a support is not particularly limited, but nickel or nickel oxide can be added to α-alumina with as large a surface area as possible.
It is necessary that the alumina be uniformly distributed in the structure of the porous alumina material, and a well-known method of immersion in a nickel salt solution is suitable.

For example, α-alumina having the above properties is immersed in an aqueous solution of nickel nitrate, and after the aqueous solution penetrates into the center of the porous material, it is naturally dried, and then forced drying at about 100 to 130°C by a conventional method, and then further The catalyst of the present invention can be obtained by heat treatment (calcination).

Here, the firing temperature is preferably 730 to 950°C, and 80°C to 950°C.
The temperature is more preferably 0 to 920°C, most preferably 850 to 900°C. If it is too low or too high from this range, the activity of the catalyst will decrease.

A suitable firing time is 1 to 10 hours. The more nickel supported, the lower the firing temperature, the longer the firing time. Usually, 2.
Firing may be performed for about 5 to 4 hours.

Firing is performed in an oxidizing atmosphere such as air.

However, if this is not sufficient, this calcination may, if circumstances permit, be carried out at least partially prior to the use of the catalyst, for example in a reactor in which the catalyst is used.

The catalyst of the present invention is similar to that of the previous Japanese Patent Publication No. 57-50533,
Since nickel is uniformly dispersed in a carrier having limited pores, the amount of carbon deposited is extremely small compared to conventional commercially available products without the addition of alkali metal elements or the like.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to these.

Example 1 Pore volume with pore diameter of 0.1 to 0.57 μm is 0.22”/
g.

An α-alumina porous body with an average particle size of 5 mm and having a pore structure with a pore size of 0.5- or more and a pore volume of 0.07I117/g was prepared using nickel nitrate (Nl (NO3) 2.6H20).
After dissolving 1.3 kg in water and immersing it in a solution with a total volume of 11, it was naturally dried day and night, and then heated to 6
After drying for an hour, it is further heated to 850°C over 5 to 6 hours.
The temperature was raised to 900° C., maintained at this temperature for 3 hours, and fired to obtain the catalyst of the present invention.

This catalyst contains 8% by weight of nickel converted to nickel oxide.
Contains. This is abbreviated as catalyst A.

Catalyst A with the same nickel content was obtained in the same manner as Catalyst A, except that the heating time, calcination temperature, and calcination time were respectively 5 hours and 690 to 710°C for 10 hours in the production of the above catalyst. It is abbreviated as -1.

Further, in the production of Catalyst A, a catalyst with the same nickel content was prepared in the same manner as Catalyst A, except that the heating time, calcination temperature, and calcination time were 6 hours and 990 to 1010°C for 3 hours, respectively. It is abbreviated as -2.

In addition, the following catalysts B and C were prepared.

Catalyst B: pore size 0.1 to 0.5 μm, pore volume 0.05ffi
/ /g, and the pore volume with a pore diameter of 0.5n or more is 0.2
A catalyst containing 8.6% by weight of nickel in terms of nickel oxide, obtained by subjecting an α-alumina porous material having a pore structure of +al/g and an average particle size of 5+t++n to the same treatment as in Example 1.

Catalyst C: pore size 0.1 to 0.5 μm, pore volume 0.21 m1
/g, and the pore volume with a pore diameter of 0.5 or more is 0m17g
A catalyst containing 8.6% by weight of nickel in terms of nickel oxide, obtained by subjecting an α-alumina porous material having a pore structure of 5 mm and an average particle size to the same treatment as in Example 1.

After each of the above catalysts was filled into a reaction tube with an inner diameter of 12.3 mm, the temperature of the catalyst layer was raised to 800°C, and the ratio of the number of moles of water vapor to the number of carbon atoms in methane was S/
C=7.0. 20 at space velocity 5Vo=1.000h-
After being exposed to light for several hours, it was used for steam reforming experiments. The reaction conditions are S/C・3.01 reaction pressure P・0.2kg/cm2
-G, 5Vo = 8,000h-', and methane and steam were supplied into the reaction tube.

The reaction product was obtained via a condenser and a gas meter, and analyzed by gas chromatography. This reaction was continued for 500 hours. Table 1 shows the experimental results. Note that the reaction time 0 is the start of the reaction immediately after reduction, and the approach temperature is the difference between the equilibrium temperature calculated from the reaction system composition and the actually measured temperature.

Table 1 The experimental results for Catalyst A showed values close to equilibrium and high activity. Further, almost no decrease in activity was observed.

Catalyst A-1 had high initial activity, but the activity decreased significantly.

Catalyst A-2 had a slightly inferior initial activity and a considerable decrease in activity.

Catalyst B has a pore volume of 0.5 m or more with a pore diameter of 0.5 f1.
Although the weight was 17 g or more, the activity was low because the pore structure satisfied only one condition.

Catalyst C has a pore volume of 0.2 ral/g or more within the pore diameter range of 0.1 to 0.5 n, but because it has a pore structure that only satisfies the first condition, there is a large decrease in activity. It was seen.

Example 2 The steam reforming activity of catalyst A used in Example 1 with respect to n-hexane was measured. The reaction conditions were S/C=3.0.
Reaction pressure P=0.2kg/cm2・G, 5Vo42.
000h-'. Table 2 shows the experimental results. It showed high activity similar to methane.

Table 2 Example 3 Changes in activity of catalyst A used in Example 1 with respect to temperature changes were investigated. The reaction conditions were S/[1:=3.0°P=0
．． 2kg/cm2・G, 5Vo=lO,000h-'
Then, methane and steam were supplied into the reaction tube, and the catalyst layer outlet temperature (reaction temperature) was changed from 650 to 850°C.

The results are shown in Table 3, No. 1.

Table-3

[Brief explanation of the drawing]

FIG. 1 is a graph showing changes in activity of the catalyst of the present invention with respect to changes in temperature. Procedural amendment @ (spontaneous) April 17, 1999 Name of the patented invention filed on April 10, 1999 Person making the amendment to catalyst for steam reforming + Relationship with r cases Patent applicant Fujimi Abrasives Industry Co., Ltd. (1 other person) (1) ``Modification of lower alcohols'' on page 5, line 8, was corrected to ``reformation of lower alcohols with steam.'' (1) ``This...decrease'' on page 6, lines 5-6. " is corrected to "If it is too high than this range, the activity of the catalyst will decrease, while if it is too low, the initial activity will be sufficiently high, but it will gradually decrease as the usage time increases." (1) From the end of page 10. Page 11, line 1: “Slightly inferior…
It was big. " was corrected to "slightly inferior." Nakai Building, 1-3 Nihonbashi Yokoyama-cho, Chuo-ku, Tokyo Contents of the amendment

Claims (1)

[Claims] 1. Pore volume within the pore diameter range of 0.1 to 0.5 μm is 0.
．． 2 ml/g or more, a pore volume of 0.5 μm or more and a pore volume of 0.05 ml/g or more, and a purity after scorching drying of 98% by weight or more,
Steam reforming characterized in that nickel is impregnated with a nickel-containing solution, dried, and then calcined, and the nickel is contained in the range of 3 to 20% by weight in terms of nickel oxide in the total weight of the catalyst. catalyst for. 2. The catalyst according to claim 1, wherein the calcination is carried out at 730-950°C. 3. The catalyst according to claim 2, wherein the firing atmosphere is an oxidizing atmosphere.