US2164292A - Process of producing hydrogen - Google Patents

Description

June 27, 1939. 1.. G. JENNESS PROCESS OF PRODUCING HYDROGEN Filed Jan. 14, 1939 3 m on TM, lea/1e 6f $121265;

fltromw g Patented June 27, 1939 PATENT OFFICE 2,164,292 raocass or raonucme maooan Leslie G. Jennes's, Englewood, N. 1., assignor to Intermetal Corporation, Newark, N. 1., a cor-.

g ration of Delaware Application January 14, 1939, Serial No. 251,041

6 Claims.

This invention relates to a process for produc ing hydrogen and more particularly to a process of producing hydrogen from mixtures oi. steam and hydrocarbons in the presence of a catalyst.

An object of the invention is to provlde a process in which hydrocarbons are substantially completely converted, a high yield of hydrogen is obtained, and the amount of hydrocarbon and carbon monoxide in the resultant gas is maintained relatively small.

Another object is to provide a process of catalytically producing hydrogen from hydrocarbons and steam wherein the temperatures throughout the process are controlled so as to obtain a high conversion of hydrocarbons and a small production of carbon monoxide.

Another object of the invention is to provide a process of catalytically producing hydrogen from hydrocarbons and steam in which a catalyst selective toward the water-gas reaction is employed.

Other objects and advantages of the invention appear in the following description of the pre- 'ferred embodiment of the invention and an apparatus capable of being employed in the practice of this invention, which is shown in the single view of the attached drawing.

In carrying out the invention, a mixture of hydrocarbons and steam is passed through a catalyst ill positioned in a closed reaction chamber or converter II which is provided with heating means shown in the drawing as electric heating. elements l2, l3, l4 and I5. This reaction chamber is preferably provided with hand holes 16 and I! at the upper and lower portions thereof, respectively, to permit inserting and removing the catalyst Ill. The reaction chamber is also preferably provided with heat insulation l8 surrounding the heating elements. A perforated plate I!) is employed at the lower portion of the reaction chamber to support the catalyst and provide for free exit of gas from the catalyst.

Steam is introduced into the upper end of the reaction chamber through a pipe 20 in controlled amounts, as by the valve 2|. A flow meter, such as an apertured plate 2| and manometer 22', may be provided to indicate the rate of flow. The hydrocarbons being treated are introduced into the steam pipe 20 through a pipe 22 in controlled amounts, as by the valve '23, so as to mix with the steam prior to contacting with the catalyst III.

A similar flow meter having apertured plate 23' and'manometer 24' may be provided to indicate the rate of flow of hydrocarbon. The resultant gas is withdrawn from the reaction chamber II at the lower portion thereof through a pipe 24 employed and connected to the valves 2| and 23,

respectively, so as to force the mixture of steam and hydrocarbons through the reaction chamber and condenser.

The catalyst employed must be'capable of promoting the reaction between a hydrocarbon and water vapor to form hydrogen and carbon diox ide. In order to produce a reduced content of methane and carbon monoxide it is important to employ catalysts which are particularly selective toward the water-gas reaction. Nickel is ordinarily employed as the catalyst although other metals, for example, cobalt, will catalyze this reaction. The foraminate nickel catalysts disclosed in my copending application Serial No. 13,972, filed March 30, 1935,particularly when produced in pellet form including a metallic skeleton by mixing with approximately 40 to 60% of copper powder and reducing as disclosed in my copending application Serial No. 49,793, filed November 14, 1935, Patent 2,136,509, November 15, 1938, are particularly suitable. These catalysts are capable of withstanding the temperatures to which they are subjected during the process withoutdisintegrating; are extremely active; are selective toward the water-gas reaction so as to increase the relative rate at which this reaction takes place; and do not objectionably impede passage of the mixture of the gases through the catalytic bed.

To produce low carbon monoxide and methane content, an excess of steam must be employed. Volume ratios of steam to hydrocarbons will range between approximately 10:1 to :1 upon a methane basis. The temperature is maintained relatively high in app ima ly e pp t fourths of the reaction chamber. It is necessary to supply heat to the reaction zone since the major reactions are endothermic, and this can be conveniently accomplished by the heating elements l2, l3 and I4. It is also preferred to use superheated steam since by this procedure the heating can be made more uniform throughout the catalyst bed and less external heat is required. Temperatures of 550 to 600 C. have been found satisfactory for the upper portion of the reaction chamber i I although these temperatures may be increased if the reaction chamber and catalyst selected are capable of operating at the higher temperatures and it is found economical to'supply the necessary additional heat. The temperature in the lower portion of the reaction chamber is caused to drop rapidly so that the exit gases in contact with the catalyst are at a lower temperature than the gases in the upper portion of the reaction chamber. It has been found that a temperature between 400 and 475 C., and preferably approximately 465 C. is desirable for the exit gases. The proper exit temperature will depend upon various factorsincluding the temperature of the upper zone, the relation between the rate of flow, the depth of the upper zone, and the depth of the lower zone.

In this process, the following reactions probably occur and must be considered:

These reactions have been given on a methane basis merely by way of example, and similar reactions will hold for any hydrocarbon. All of these reactions are reversible and will approach equilibrium if sumcient time is allowed under given conditions of temperature and ratios of methane to steam. It will be seen that increased amounts of steam will tend to force all of these reactions toward the right in accordance with the law of mass action. This" will result in an increased conversion of methane as shown by the first two reactions and a decreased amount of carbon monoxide as shown by the last reaction. It is, therefore, desirable to use large excesses of steam and the more steam employed the better is the resultant gas. However, there is a practical limit to the excess of steam, since an extremely large amount of steam requires an excessive amount of heat for production thereof and also, by increasing the total volume of gas per volume of methane, decreases the volume of methane which may be passed over a given catalyst bed.

The first two reactions are endothermic, and

- an increase in temperature not only speeds up the rate of these reactions, but also shifts their equilibrium points by forcing the reactions toward the right so as to result in a greater methane conversion. The third reaction is exothermic and increase in temperature shifts this reaction to the left resulting in an increase in carbon monoxide in the resultant gas. Since all of these reactions are reversible, a decrease in temperature will shift the reactions in the opposite direction. By maintaining the reaction temperature in the entrance portion of the converter relatively high and continuing this temperature through a considerable portion of the reaction chamber and in the presence of an active catalyst, the gas may be made to approach the equilibrium condition at this temperature for a given steam methane ratio. The gas resulting from the high temperature operation is extremely low in methane but is relatively high in carbon monoxide.

If this temperature is rapidly dropped while the gases are in contact with the catalyst, and the gases are promptly withdrawn from contact with the catalyst, it'has been found that the carbon monoxide content is decreased without objectionably increasing the methane content. That is, the lower temperature causes the third reaction to take placeioward the right and tends to cause the first two reactions to go toward the left, but the third reaction proceeds at a faster rate than the first two reactions. If the gases wereallowed to remain for a considerable length of time in contact with the catalyst at the lower temperature, equilibrium conditions would again be reached and the methane content increased stantially equilibrium conditions are reached at 15 the higher temperature, but are not reached at the lower temperature, resultant gases containing less than 1% methane, 1% or less carbon monoxide, approximately 23% carbon dioxide and the remainder hydrogen, have been produced. At equilibrium at the upper temperature, the carbon monoxide con-tent is considerably above 1% and at equilibrium conditions at the lower temperature the methane content is considerably above 1%. Thus the present process results in a product having higher methane conversion and lower carbon monoxide content than is possible even under equilibrium conditions in other processes.

As a specific example of the present process, a converter or reaction chamber I i having an over all length of 14 feet and an inside diameter of 15 inches was charged with 1520 pounds of catalyst pellets so as to substantially completely fill the converter up to the upper hand hole. This catalyst was prepared by forming a precipitate in a solution of a nickel compound and a chromium compound .as disclosed in my copending application, Serial No. 13,972, above mentioned. As further disclosed in said application, nickel sulphate and sodium dichromate were dissolved in water and the precipitate formed by addingcaustic soda. This precipitate was filtered from the solution and dried. The pH of the precipitating solution, the temperature thereof and the relative concentrations of the materials dissolved in the solution were adjusted to produce a. dried aggregate having a ratio of nickel oxide to chromium trioxide of approximately 6:1, as expressed by the formula 6NiO:CrO3. This precipitate was crushed such that 98 to 99% would pass through a 200-mesh screen and was then leached with approximately 10% caustic soda solution to render the chromium oxide soluble and substantially remove it from the aggregate. After leaching, this product was again dried and passed through a pulverizer to separate the particles thereof. 1

As disclosed in my copending application, Serial No. 49,793, also above mentioned, this aggregate was mixed with an equal amount, by weight, of 100 to 150 mesh metallic copper, and compressed into circular pellets about inch in diameter and V inch in thickness by a Stokes pellet machine. In the particular example chosen, the catalyst was reduced after being charged through the converter in order to form the metallic, skeleton referred to in my said copending application, Serial No. 49,793. This reduction was carried on for approximately two hours with a very low gas flow. The temperature of the conplete the reduction. At this temperature throughout the converter, the resultant gas showed the presence of approximately 1.37% carbon monoxide and .3% methane by volume.

The temperature of the exit gases was then dropped to 465 C. by decreasing the power supplied to the lower heating element I5 after which the resultant gas showed a content of 1.0% carbon monoxide and 0.3% methane with 22.9% carbon dioxide, and 75.8% hydrogen. This represents a hydrocarbon conversion of 98.7% on a methane basis. It will be noted that the combined methane and carbon monoxide content was 1.3%.

The flow was increased up to 13 pounds of propane per hour, still maintaining a steampropane ratio of approximately 14 without materially changing the results given. Since 12 pounds of propane under these conditions will produce approximately 1000 cubic feet of gas, this was at the rate of approximately 26,000 cubic feetof hydrogen produced per day. By employing superheated steam at 600 C. the capacity of the converter may be increased to approximately 40,000 cubic feet of hydrogen per day with results substantially the same as given above.

The selectivity of the catalyst employed toward the third reaction in preference of the re verse of the first andsecond reactions above given is of importance in producing a low combined methane and, carbon monoxide content. The catalyst made from the 6 NiOzCrOa aggregate as above described gave the best selectivity under the conditions of the above example. A

catalyst made from an aggregate containing 13 NiozAlzOa also gave good results but not as good as the catalyst made from the 6 NiOzGrOa aggregate. At the temperatures of the above example these ratios of nickel oxide to other oxide for the catalysts made from the nickel-chromium aggregate and the nickel aluminum oxide produced the lowest combined methane and carbon monoxide content. For other temperatures, other ratios of nickel oxide to other oxide produce the most selectivity toward the third reaction and thus give the lowest combined methane and carbon monoxide content. That is to say, for a given temperature of treatment in the exit portion of the catalytic treating zone and a given type of foraminate catalyst there is a ratio of nickel oxide to other oxides in the aggregate from which the catalyst is produced which will be most selective and provide the lowest combined methane and carbon monoxide content.

The two zone operation of the present invention, in which the gases are passed through a high temperature zone in contact with the catalyst for a time sufilcient to reach substantially equilibrium conditions and then through a low temperature zone in contact with the catalyst but are removed from contact with the catalyst before equilibrium is reached, produces a resultant gas which is low in methane as well as carbon dioxide. Since a high temperature is employed in the major portion of the process and the reaction rates are greater at higher temperatures, the total amount of catalyst and time of contact with the gases to produce a given carbon monoxide content is reduced. The two temperature zones can be conveniently positioned in the same-converter. as described above, but it is apparent that the zones may be maintained in different converters at the desired temperatures and the gas delivered from the high temperature converter to the low temperature converter and removed from the latter before equilibrium conditions are reached.

a This application is a continuation in part of my copending application Serial No. 76,655, filed April 27, 1936.

While I have disclosed a preferred embodiment of my invention, and have given in detail a theory of operation thereof, it is understood that I am not to be limited to any theory of operation and that the details of the process may be varied within the scope of the following claims.

I claim:

The process of producing hydrogen which comprises bringing a mixture of gases containing a hydrocarbon and excess steam into contact with a catalyst for the reaction between steam and said hydrocarbon and between steam and carbon monoxide to produce hydrogen, contacting said mixture with said catalyst for sufficient time and at sufficient temperature to produce hydrogen having a relatively low hydrocarbon content and a comparatively high carbon monoxide content, lowering the temperature of the resulting gases, further contacting the same with said catalyst for a time sufficient to materially lower the carbon monoxide content thereof and removing the resulting gases from contact with said catalyst before the hydrocarbon content has been substantially increased, said catalyst being one which is prepared by forming an aggregate of particles having an oxide of a metal which is catalytically active for said reactions chemically fixed to another metal oxide which is capable of being leached from the oxide of the catalytically active metal without shattering said particles, said metal oxides being chemically fixed to each other in substantiaily that proportion which will give the final catalyst the property of promoting said reaction with a greater ratio of reaction between carbon monoxide and steam to the reaction velocity of any other reaction at the temperature of said further contacting than will result when "the catalyst is prepared with any other proportion, leaching said other metal oxide from said aggregate and reducing the catalytically active metal oxide.

2. The process of producing hydrogen which comprises bringing a mixture of gases containing a. hydrocarbon and excess steam into contact with a nickel catalyst, contacting said mixture with said catalyst for suflicient time and at suflicient temperature to produce hydrogen having a relatively low hydrocarbon content and a comparatively high carbon monoxide content, lowering the temperature of the resulting gases, further contacting the same with said catalyst for a time sufficient to materially lower the carbon monoxide content thereof and removing the resulting gases from contact with said catalyst before the hydrocarbon content has been substantially increased, said catalyst being one which is prepared by forming an aggregate of particles having nickel oxide chemically fixed to another metal oxide which is capable of being leached from said nickel oxide without shattering said, particles, said metal oxides being chemically fixed to each other in substantially that proportion which will give the final catalyst that property of promoting said reactions with a greater ratio of reaction between carbon monoxide and steam to the reaction velocity of any other reaction at the temperature of said further contacting than will result when the catalyst is prepared with any other proportions, leaching said other oxide from said aggregate and reducing said nickel oxide.

3. The process of producing hydrogen which comprises bringing a mixture of gases containing a hydrocarbon and excess steam into contact with a nickel catalyst, contacting said mixture with said catalyst for suilieient time at a temperature between approximately 550 and 600 C. to produce hydrogen having a relatively low hydrocarbon content and a comparatively high carbon monoxide content, lowering the temperature of the resulting gases to a temperature between approximately 400 and 475 C. further contacting the resulting gases with said catalyst for suilicient time to materially lower the carbon monoxide content and removing the resulting gases from contact with said catalyst before the hydrocarbon content has been substantially increased, said catalyst being one which is prepared by forming an aggregate of particles having nickel oxide chemically fixed to chromium oxide in a ratio of approximately 6 to 1, leaching chromium oxide from said particles and reducing the resulting nickel oxide.

4. The process of producing hydrogen which comprises bringing a mixture of gases containing a hydrocarbon and excess steam into contact with a nickel catalyst, contacting said mixture with said catalyst for suflicient time at a temperature between approximately 550 and 600 C. to produce hydrogen having a relatively low hydrocarbon content and a comparatively high carbon monoxide content, lowering the temperature of the resulting gases to a temperature between approximately 400 and 475 0., further contacting the resulting gases with said catalyst for sufiicient time to materially lower the carbon monoxide content and removing the resulting gases from contact with said catalyst before the hydrocarbon content has been substantially increased, said catalyst being one which is prepared by forming an aggregate of particles having nickel oxide chemically fixed to aluminum oxide in a ratio of approximately 13 to 1, leaching aluminum oxide from said particles and reducing the resulting nickel oxide.

5. The process of producing hydrogen which comprises bringing a mixture of gases containing a hydrocarbon and excess steam into contact with a. nickel catalyst, contacting said mixture with said catalyst for suflicient time at a temperature between approximatetly 550 and 600 C. to produce hydrogen having a relatively low hydrocarbon content and a comparatively high carbon monoxide content, lowering the temperature of the resulting gases to a temperature between approximately 400 and 475 0., further contacting the resulting gases with said catalyst for sumcient time to materially lower the carbon monoxide content and removing the resulting gases from contact with said catalyst before the hydrocarbon content has been substantially increased, said catalyst being one which is prepared by forming an aggregate of particles having nickel oxide chemically fixed to chromium oxide in a ratio of approximately 6 to 1, leaching chromium oxide from said particles, mixing between approximately 40 and of powdered copper with the resulting nickel oxide, compressing the mixture of copper and nickel oxide into pellets and reducing said nickel oxide to form a porous pellet containing metallic copper and nickel.

6. The process of producing hydrogen which comprises bringing a mixture of gases containing a hydrocarbon and excess steam into contact with a nickel catalyst, contacting said mixture with said catalyst for suflicient time at a temperature between approximately 550 and 600 C. to produce hydrogen having a relatively low hydrocarbon content and a comparatively high carbon monoxide content, lowering the temperature of the resulting gases to a temperature between approximately 400 and 475 0., further contacting the resulting gases with said catalyst for suflicient time to materially lower the carbon monoxide content and removing the resulting gases from ly 40 and 60% of powdered copper with the resuiting nickel oxide, compressing the mixture of copper and nickel oxide into pellets and reducing said nickel oxide to form a porous pellet containing metallic copper and nickel.

LESLIE G. JENNESR

Images