CA1174031A - Conversion of methanol into hydrogen and carbon monoxide - Google Patents

Abstract

Abstract of the Disclosure A gas stream containing methanol is contacted with a catalyst including nickel and potassium supported on an alumina carrier, whereby the methanol is converted into hydrogen and carbon monoxide.

Description

~1740`31 sac~;ground of the Invention This invention relates to a process for the catalytic conver-sion of methanol into hydrogen and carbon monoxide.
There are increasing demands for hydrogen and carbon monoxide in many fields and methanol is now an important starting material therefor in that it can give hydrogen and carbon monoxide through catalytic decomposition. In an internal combustion engine, the waste heat generated therefrom can be utilized for the catalytic conversion of methanol into hydrogen and carbon monoxide, the mixed gas product being introduced into the engine as at least a part of the fuel. This method is advantages not only from an economic point of view but also from the standpoint of preventive pollution since the discharge of nitrogen oxides and carbon monoxid l may be significantly reduced.
Catalytic conversion of methanol is also utili2ed in a fuel icell, in which an oxygen-containing gas is supplied to the anode and a fuel, ?referably hydrogen,is supplied to the cathode. The reaction between the anode and cathode can produce an electrical energy. The hydrogen may be produced by methanol. Thus, methanol is catalytically converted into hydrogen and carbon monoxide, the latter being further reacted with water to yield hydrogen and carbon dioxide by water gas reaction. The hydrogen obtained in the two-stage process is separated from carbon dioxide for the intro-duction to the cathode.
In addition, hydrogen and carbon monoxide are used in a wide variety of chemical plants. For example, hydrogen is utilized for hydrogenation of organic compounds, hydrotreatment of heavy hydrocarbon oils, etc.and carbon monoxide is utilized for the production of carbonyl group-containing organic compounds.

~17403~

There is, therefore, a great demand for an effec-tive process capable of converting methanol into hydrogen and carbon monoxide. A process is proposed in which a catalyst containing nickel, l~mthanum and ruthenium supported on silica gel is used. Although the catalyst can exhibit a relatively high activity for the decomposi~
tion of methanol at an initial stage r the catalytic activity is gradually lowered as the reaction at about 300 C proceeds and the catalyst is considerably deteriorated after about several hours. A process is also known wherein a catalyst having copper and~or nickel supported on silica gel is used. This catalyst, however, is poor in resistance to heat and7 moreover~ is defective because with its undesirable by-products such as water and methane are formed at about 400C or more. The term "for`mation of ''~y-productsll herein and hereinafter means the case where compounds other th m methanol, hydrogen and carbon monoxide are contained in the reaction product in an amount of 10 ~-vol % or more. The formation of by~products requires an , additional step for the removal thereof and is not accept-able in practice.

gummary of tXe Invention It is, therefore, an object of an aspect of the present invention to provide a process which is devoid of the drawbacks of the prior art process.
An object of an aspect of the present invention is to provide an effective process by which methanol may be 1174~31 decomposed into hydrogen and carbon monoxide while mini-mizing the formation of undesirable by-products such as dimethyl ether, methane, water, carbon dioxide and methyl formaldehyde.
An object of an aspect of the present invention is to provide a process in which the catalytic conversion of methanol can be performed in a stable manner for a long period of process time.
In accomplishing the foregoing objects, there is provided in accordance with the present invention a process of decomposing methanol for the production of hydrogen and carbon monoxide, which comprises contacting a gas stream containing methanol with a catalyst including a carrier material of alumina, and nickel and potassium supported on the carrier material. The content of Ni is in the range of about 1-12 mg-atom per one gram of the carrier and the content of K is n the range of about 1-12 mg-atom per one gram of the carrier.
Other objectsJ features and advantages of the present invention will become apparent from the detailed description of the invention to follow.
Detailed Description of the Invention The process of this invention includes contacting a methanol-containing gas with a catalyst comprised of alumina as a carrier material and nickel and potassium carried on the carrier material.
Any activated alumina may be suitably ~sed as the carrier material. Illustrative of such activated alumina ~L174~31 -4a- .

are y (gamma)-alumina, ~ ~kappa)-alumina, ~ (delta)-alumina, ~eta)-alumina, B ltheata)-alumina, p (rho)-alumina and lchai)-alumina. The alumina carrier preferably has a specific surface area of about 150 - 300 m2/g.
Supported on the alumina carrier are nickel and po-tassium. The content of the nickel in the catalyst should fall within the ~? '', 1~74C13~

~range of about 1-12 mg-atom (i.e. 58.7 - 704.4 mg) per 1 g of the ¦alumina carrier. An amount of Ni below 1 mg-atom is insufficient ¦to impart practically acceptable activity to the catalyst and, I moreover, causes a danger of the formation of by-products. Above ¦ 12 mg-atom Ni, the catalytlc activity is considerably lowered.
The Ni content is preferably about 2 - 8 mg-atom. The content of ¦ the potassium in the catalyst should also fall within the range of about 1-12 mg-atom li.e. 39.1 - 469.2 mg) per 1 g of the alumina l carrier. An amount of K below 1 mg-atom causes the formation of ¦ by-products. Above 12 mg-atom K, the catalyst becomes poor in activity. The K content is preferably about 2-8 mg-atom~
The catalyst of this invention may be prepared in any known ¦manner. For example, a water soluble nickel salt such as nickel ¦nitrate is dissolved in water, with which an alumina carrier lS Imaterial is impregnated. The impregnated material is then dried ¦and calcined in tne atmosphere of oxygen. The calcination is ¦preferably conducted while elevating the tem~erature stepwise from ¦100 to 500C. The carrier material thus loaded with nickel is ~then impregnated with a solution containing a potassium compound such as potassium nitrate. ~he resulting impregnated material is ¦subsequently dried and calcined in the same manner as described ¦above to obtain a catalyst containing nickel and potassium carried on the carrier material. The catalyst may also be prepared by impregnating a carrier material with a solution containing both nickel and potassium compounds, followed by drying and calcination.
In order to stabilize the catalytic performance, it is preferred that the thus obtained catalyst be subjected to a pre-treatment with a reducing gas. The pretreatment, which may be .
performed either just after the calcinatiOn step or before conduct-ing the methanol conversion process, includes heating the catalyst ~1~4C13~
at a temperature of 200 - 500C, preferably 300 - 400C, for 1 - 15 hours in the atmosphere of a reducing gas such as hydrogen or methanol.
The step of contacting a methanol-containing gas stream with S the catal~st is carried out at a temperature of 200 - 600C, preferably 250 - 500C for 0.1 - 12 sec, preferably 1 - 10 sec.
The content of the methanol in the gas stream can be 100 ~. The gas stream may contain an inert gas such as argon or nitrogen, however.
The following examples will further illustrate the present invention.

Example 1 Nickel nitrate was dissolved in water to obtain an aqueous solution having a Ni content of 1 g/Q. ~ith the solution was impregnated a y-alumina carrier to obtain nickel-impregnated alumina. The impregnated alumina was dried and calcined at 500C
for 4 hours whereby to obtain a nickel-carrying alumina having a Ni content of 2 mg-atom per one gram of the alumina carrier. The nickel-carrying alumina was then impregnated with an aqueous solution containing potassium nitrate and having a K content of 1 g/Q to obtain an impregnated material. The impregnated material was then dried and calcined in the same manner as above thereby to obtain a nickel and potassium-carrying alumina catalyst having a Ni content of 2 mg-atom and a K content of 2 mg-atom per 1 g of the carrier.
0.5 g of the thus obtained catalyst were packed in a reac~ion tube having an inner diameter of 9 mm, through which was streamed first a hydrogen gas at 500C for 2 hours and then a mixed gas containing methanol vapor (partlal pressure: 0.8 atm.) and argon . .

1~74C~31 (partial pressure: 0.2 atm.) at a flow rate of 12.4 mQ/hour in ter~s of liquid methanol at 300 - 350C for 15 hours to stabilize the catalyst performance- After this pretreatment, a feed gas con~aining methanol vapor (0.5 atm.) and argon ~0.5 atm.) was introduced into the reaction tube for contact with the packed catalyst layer at 350C for 12 sec. The effluent gas was sampled for analyzing the conversion ~decomposition~ rate and the composi-tion thereof. The results of the analysis are shown in Table 1.

Comparative Example 1 Thirteen types of catalysts were prepared using nitrates of the metal components shown in Table 1 in the same manner as that in Example 1. The content of each of the catalyst metal components was 2 mg-atom per one gram of the alumina carrier. However, rhodium was contained in an amount of 0.05 mg-atom per one gram of the alumina carrier ~Experiment No. 14~ and no catalyst metal component was contained in the catalyst of Experiment No. 2. Each catalyst was subjected to pretreatment conditions in the same manner as that in Example 1 and, with the use of the pretreated catalyst, methanol was decomposed in the same manner as that in Example 1. The results were as shown in Table 1.

~74~P3i _ h .~
~ ~
_ ._ , _ S o o O O O o o o o o ~1 Ll .. _ _ .__ U ~
~ ~ o ~ I~ ~ o o o o o o ~0 S Il~

o a o _ 8~ E u~ o ~ o o o ~ o o aJ t~ Q
Q ~) O In O ~ o o 1` o o r~
_ d~ . U~ .
u~ O ~`I N ~n o N ~ u~ n o ~S~ u~
r~ E .,~

Z
` 0~
~ ~ ~i ~1 Z ~ O ~ ~ O :~ ~ s ~, ~ 8 z E~

E
~ o ~ o ~ ~ ~ er .
XZ ___ _ _ ~ 8 -~74Q31 As will be appreciated from the results shown in Table 1, whilst a high methanol conversion is attained when alumina is used by itself as catalyst (Experiment No. 23, the majority of the product is dimethyl ether and water and neither hydrogen nor carbon monoxide is yielded. With a catalyst containing potassium alone as catalyst metal component (Experiment No. 3), methanol conversion is significantly lowered and no improvement in selecti-vity is seen as compared with the case of Experiment No. 2. With a catalyst containin$ nickel alone as catalyst metal component (Experiment No~ 4), on the other hand, undesirable by-products are formed in large amounts. In contrast, the catalyst of the present ¦invention containing both nickel and potassium (Experiment No. 1) ¦exhibits both a high methanol conversion and an excellent selecti-¦vity to hydrogen and carbon monoxide. When the nickel is substi-¦tuted with other metals ~Experiments Nos. 5-14), satisfactory ¦con~ersion is not obtained.

Example 2 Methanol decomposition was conducted in the same manner as that in Example 1 except that the pretreatment conditions were varied. Thus, in Experiments Nos. 15 and 16, argon and hydrogen were used, respectively, in place of the hydrogen used in the pretreatment step of Example 1. In Experiment No. 17, the pre-treatment was carried out by feeding a hydrogen gas to the reaction tube at 310 - 350C for 15 hours. In Experiment No. 18, the pretreatment was performed by feeding the same mixed gas as used in Example 1 at 300 - 350C for 15 hours. The results are shown in Table 2 together with those of Experiment No. 1.

~7~ 31 Table 2 I . .
Experiment Treatment Conversion Composition of product ~vol %) of methanol No. gas (%) Hydrogen monoxide By-products . . . ..
1 hydrogen, 52 65 35 0 methanol 79 67 33 0 16 oxygen, 55 67 33 0 17 hydrogen 61 64.5 35.5 0 18 methanol 75 68 32 0 _ .. _ . .

The results in Table 2 indicate that pretreatment conditions have an influence upon the activity of the catalyst. It is seen ¦that when the treatment with methano~l is to be preceded by the high temperature treatment with other gases (Experiment Nos. 1, 15 and 16), the use of argon is preferable.

¦Example 3 .
A catalyst having a Ni content of 4 mg-atom and a-K content of 4 mg-atom per one gram of alumina was prepared in the same manner as described in Example 1. With the use of this catalyst, methanol was decomposed in the same manner as that in Example 1 except that argon was used in place of hydrogen in the pretreatment step and the catalytic conversion was performed at temperatures of 3~0C (Experiment No. 19) and 430~C ~Experiment No. 20). The results are shown in Table 3.

` ~' 10 -1~7~CD3~
Comparative Example 2 Using silica gel as a carrier material, two types of catalysts were prepared in the same manner as that in Example 1. One of the catalysts contained nickel as its catalytic metal component in an amount of 4 mg-atom per one gram of the silica gel carrier~ The other cataly t contained nickel and potassium each in an amount of 4 mg-atom per one gram of the carrier. With the use of these catalysts, methanol was decomposed in the same manner as that in Exam~le 3. The results are summarized in Table 3.

~ 403;~
~ ~ o o o o o o I .~ __ o~ ~
l _I Q X O ~ O O N
I ~ ~ _ l 3 O O _ O N
l ~0 C~ __ l O S o ~n N O U~
I . ,0 ~) l .~ O X 1~ N 1~ o O u~
I ~ ~ao ~ ~1 ~_1 l C~ ~ , l O u~ ~ N un O ~D
l ~ ~ ~ ~D~ I~ ~r Q r--I e E~ U) O^
~ dP ~ O O O N O
O ~- U~ _~ t` ~ _l O ~ .~
~3 o ~ o o o o o o .,, ~ ~, o ~ o ~ o ~o ~. ~ .,. ~ ~ ~
. ,~ ~ 0 .~ .~ ~ ~ ~ ~

~o ~ .~ ~;
~ ~ ~ .,, Z .,, o æ æ .

E ._ ,1 0 O~ O _1 ~ ~ ~
X _I N N N N N

, ~ ~
~ - 12 -1 117~031 l As will be seen from Table 3, the nickel-carrying silica gel ¦ca~alyst exhibits outstanding activity at 300C (Experiment No. 21) ¦With this catalyst, however, when ~he reaction temperature is ¦raised so as to increase the conversion, the selectivity to hydro-¦gen and carbon monoxide becomes considerably lowered and the ¦yield o~ by-products increases (Experiment No. 22). This tendency ¦is also observed in the case of the catalyst having both nickel and potassium carried on silica gel ~Experiments Nos. 23 and 24).
I In contrast thereto~ the catalyst of this invention can exhibit l good catalytic activity even at a low temperature (Experiment No.
19) and excellent selectivity to hydrogen and carbon monoxide even at a high temperature ~Experiment No. 20).

Example 4 l Catalysts having the various Ni and K contents indicated in 1 Table 4 were prepared in the same manner as that in Example 1.
Tests of catalytic conversion of methanol were carried out with the,e catalysts in the same manner as described in Example 1 at temperatures of 300, 350, 400 and 450C. The test results were as shown in Table 4.

!
.. ..

~17~31 Table 4 Content of catalytic Conversion of methanol(~) Experiment metal component No. (mg-atom/g-alumlna¦ Reacti )n temperatur~ (C) . Ni K 300 350 400 450 29 4 0.5 24 50 74 99 I . . .. _ _ .... .

¦ It will be appreciated from the results in Table 4 that the ¦catalyst containing potassium alone (Experiment No. 25) fails to .
¦show practically acceptable methanol conversion activity at any ¦temperatures. Moreover, as shown in Table 1, Experiment No. 3, considerably large amounts of by-products are produced. While the catalyst having nickel alone ~Experiment No. 28) can show high ,, . . -, me~anol decomposition activity, the yield of by-products is very hig~ as shown in Table 1~ Experiment No. 4- This is al50 the case wit5 the catalyst having a K content of 0.5 mg-atom (Experiment No.
29l. The other catalysts shown in Table 4 can exhibit practically ac~ptable methanol deco~position activity at suitably selected tem~eratures and can show good selectivity to hydrogen and carbon monoxide. Especially, the catalysts having 2-8 mg-atom each, of Ni and K contents are very advantageous because they can exhibit satisfactory ætivity at a temperature of 350C while substantially preventing the formation of by-products (Experiments Nos. 27, 31-36 and 38-40).

ExaDple 5 The same type of the catalyst as employed in Example 4, Experiment No. 33, was used in this example. The catalyst was subjected to the same pretreatment conditions as those in Example 4 except that the treatment with the mixed gas was continued furthe r 145 hours, i.e. 160 hours in total. Thereafter, a methanol dec~mposition test was performed in the same manner as that in IExa~ple 1 at temperatures of 300, 350 and 400C. The results are Ishown in Table 5 together with those of Experiment No. 33.

¦ Table 5 I ..... .
I . . . ~ .
I . Conversion of methanol~%3 I Experiment Pretreatment tlme _ _ No. (with methanoll 300C 350C 400C

33 15 hours 53 89 98 42 160 hours 50 a4 99 ~ 15 -1 1174(~31 The results in Table 5 show that the catalyst used for 160 hours can still exhibit excellent catalytic performance comparable to the catalyst after 15 hours process time. The analysis of the product revealed that the product consisted of 65 ~ of hydrogen S and 35 ~ of carbon monoxide. These facts indicate that the catalyst of this invention has a sufficiently long catalyst life.

~ 16 ~

Claims (7)

1. A process of decomposing methanol for the production of hydrogen and carbon monoxide, comprising contacting a gas stream containing methanol with a catalyst comprising a carrier material of alumina, and nickel and potassium supported on said carrier, wherein the content of the nickel is in the range of about 1 to 12 mg-atom per one gram of said carrier and the content of the potassium is in the range of about 1 to 12 mg-atom per one gram of said carrier.

2. A process as claimed in claim 1, wherein the content of the nickel is in the range of about 2 to 8 mg-atom and the content of the potassium is in the range of about 2 to 8 mg-atom both per one gram of said carrier.

3. A process as claimed in claim 1, wherein said contact is performed at a temperature of 200 to 600°C for a period of 0.1 to 12 sec.

4. A process as claimed in claim 3, wherein said contact is performed at a temperature of 250 to 500°C for a period of 1 to 10 sec.

5. A process as claimed in claim 1, further comprising pretreating said catalyst with a reducing gas at a temperature of 200 to 500°C for 1 to 15 hours before said contact step.

6. A process as claimed in claim 5, wherein said reducing gas is a methanol- or hydrogen-containing gas.

7. A process as claimed in claim 5, wherein said pretreatment is performed at a temperature of 300 to 400°C.