DE1123074B - Steam reforming process for hydrocarbons - Google Patents

Description

The invention relates to the steam reforming of hydrocarbons.

At elevated temperatures, at atmospheric or higher pressure and in the presence of a catalyst Hydrocarbons react with water vapor to form one of hydrogen, carbon oxides and methane existing gas, the composition of the gas depending on the conditions depends under which the implementation is carried out. Such a process takes place in industry many applications, for example the production of methanol synthesis gas from a petroleum distillation fraction, and is commonly known as steam reforming of hydrocarbons. The procedure is usually carried out above 600 ° C, with nickel being a suitable catalyst.

All hydrocarbons derived from petroleum contain sulphurous impurities. The use of such impure hydrocarbons in a steam reforming process would poison the catalyst; therefore, petroleum fractions are used before they are used substantially completely desulfurized for steam reforming.

The relationships between the water vapor and the constituents of the reformed steam Mixture of carbon dioxide, carbon monoxide, hydrogen and produced by hydrocarbons Methane are determined according to the chemical equilibria between them; H. the shift of the water gas equilibrium

Steam reforming process
for hydrocarbons

Applicant:

Imperial Chemical Industries Limited,
London

Representative: Dr.-Ing. H. Fincke,

Berlin-Lichterfelde, Drakestr. 51,

Dipl.-Ing. H. Bohr and Dipl.-Ing. S. Staeger,

Munich 5, patent attorneys

Claimed priority:
Great Britain August 27, 1959 and July 21, 1960

Thomas James Perret Pearce,

Norton-on-Tees, Durham (Great Britain),

has been named as the inventor

CO

CO ₂ + H ₂

and the methane water vapor equilibrium

CH ₄

H ₂ O = ^ CO + 3H ₂

The supported nickel catalysts commonly used for steam reforming can react closely following these two equilibria.

If the amount of water vapor present is low enough, the reaction can turn into two more Approximate equilibria, viz

2CO = * = CO ₂ + C
CH ₄ ^ 2H ₂ + C

These two reactions lead to the formation of carbon. The presence of carbon is there Not only is it undesirable in the gas produced, but its deposition causes a throttling the catalyst tubes in which the steam reforming is carried out. From thermodynamics of the system it can be calculated that carbon is not an equilibrium product if that Water vapor ratio 2 or more molecules per atom of carbon in the reacting hydrocarbon amounts to. Nevertheless, in practice, carbon deposition occurs when the water vapor ratio is significantly greater than 2 molecules of vapor per atom of carbon; and it was found that To prevent carbon deposition, the water vapor ratio should be at least 6.

"Light distillate" (including a simply distilled petroleum distillation fraction with the final boiling point is understood under 200 ° C) contains such an amount of sulfur that when used in a steam reforming process the reforming catalyst would soon be poisoned. Therefore, light distillate has always been substantially completely desulfurized before the steam reforming; a water vapor ratio of 6 to 7 molecules of vapor per atom of carbon in general must be used can be used to prevent carbon deposition.

U.S. Patent 2,711,419 suggests its use a hydrocarbon feedstock with 0.05 weight percent sulfur content for the Production of carbon monoxide and hydrogen using a steam reforming process. However, apart from the further

209 507/157

possible catalyst poisoning, difficulties due to carbon deposition on the condenser and not prevented by the resulting business interruptions.

The surprising discovery has now been made that if only a small amount of sulfur - as explained below - is present in the light distillate, the steam reforming process at a vapor ratio well below 6 can be carried out without carbon deposition entry.

According to the present invention, therefore, there is provided a steam reforming process for hydrocarbons proposed which consists of the reaction between a hydrocarbon or a mixture of hydrocarbons and water vapor at elevated temperature, at atmospheric or higher pressure and in the presence of a suitable catalyst marked that in a sulfur-containing impurity in the reacting hydrocarbon or hydrocarbon mixture is present to such an extent that the reactant is between about 0.0001 and 0.001 weight percent Contains sulfur.

The steam reforming process is practiced at a temperature between 600 and 1000 ° C (preferably between 700 and 900 ° C) and a pressure between 1 and 20 atmospheres, preferably carried out between 10 and 15 atmospheres absolute. A particularly suitable catalyst is on Nickel applied to a carrier, for example aluminum oxide. The catalyst is preferred essentially free of silica.

The reacting hydrocarbon is preferably light distillate.

Preferably the reacting hydrocarbon should be between 0.0001 and 0.0005 percent by weight Contain sulfur. A particularly preferred sulfur concentration is about 0.0002 percent by weight. Above 0.0008 weight percent sulfur it becomes necessary to keep the working temperature to increase quite considerably, which is an economic disadvantage.

In order to obtain a reactant with the required sulfur content, the initial Desulfurization to which the impure hydrocarbon must be subjected under such conditions be carried out so that the appropriate amount of sulfur can be removed. Alternatively a material containing a suitable amount of sulfur, for example an unpurified hydrocarbon, added to an amount of substantially completely desulfurized hydrocarbon will.

It has been found that light distillate with a content of about 0.0002 percent by weight sulfur for the production of gas for the methanol synthesis without carbon deposition of the steam reforming can be subjected when the steam ratio used in the process is as low as 2.5 molecules of vapor per carbon atom.

It must be noted that the composition of the gas produced by the process on the reaction conditions, such as temperature and nature of the catalyst, depends.

The main advantage of the present invention is that the method using a relatively low water vapor ratio can be carried out. Don't just do this the process more economical, but the use of less steam leads to the fact that the produced gas richer in carbon monoxide and therefore for use in methanol synthesis is more suitable.

example 1

40 1 light distillate with the boiling point range from 40 to 170 ° C were with the equimolecular amount

ίο mixed hydrogen and the resulting mixture at a pressure of 21 kg / cm ² through a zinc oxide layer, then through one which consisted of a mixture of aluminum oxide precipitated cobalt and molybdenum oxides, and finally passed through a zinc oxide layer, with all three layers on 380 to 400 ° C were heated.

The product obtained, which was essentially completely desulfurized, was mixed with 108 kg of steam to which 250 ecm of unpurified light distillate with a content of 0.03 percent by weight of organically bound sulfur had been added. The mixture produced contained about 0.00019 percent by weight sulfur and the water vapor ratio was about 3 molecules of water vapor per carbon atom. This mixture was passed at a pressure of 12.6 kg / cm ² through a tube filled with a reforming catalyst which contained 18% by weight of nickel. The wall of the pipe, which had a diameter of 101.6 mm and a length of 6.1 m, was kept at 860 ° C. by a surrounding furnace.

There was no increase in the pressure drop in the pipe over a period of 5 days and no carbon was deposited on the catalyst during this time, none Carbon particles carried through the pipe with the produced gas and was not an apparent one The catalytic converter has deteriorated.

The same experiment was carried out using essentially completely desulfurized Made light distillate to which no sulfur had been added. The carbon deposition was continuously, and after less than 24 hours complete blockage of the tube had occurred.

Example 2

A second distillate was prepared in exactly the same way as described in the second paragraph of Example 1, with the exception that the mixture of purified and unpurified light distillate was made to contain about 0.0004 weight percent sulfur. After 5 days of work no carbon formation had occurred and the activity of the catalyst was in no way whatsoever decreased. When the sulfur concentration is reduced to 0.0008 percent by weight under the same conditions was increased, no carbon formation was detectable; but there was a visible loss of the catalytic Effectiveness because it became necessary to increase the working temperature by 20 ° C in order to to achieve the same degree of conversion.

Claims (11)

PATENT CLAIMS: 1. Steam reforming process for hydrocarbons, which results from the reaction between a hydrocarbon or a carbon 10 Hydrogen mixture and water vapor at elevated temperature, at atmospheric or higher pressure and in the presence of a suitable catalyst, characterized in that a sulfur-containing impurity or impurities in a total concentration corresponding to 0.0001 to 0.001 percent by weight, in particular 0.0001, in the reacting hydrocarbon or hydrocarbon mixture up to 0.0005 weight percent sulfur is present. 2. The method according to claim 1, characterized in that said concentration at is about 0.0002 weight percent. 3. The method according to claim 1 or 2, characterized in that the hydrocarbon "light distillate" serves. 4. The method according to any one of claims 1 to 3, characterized in that the steam reforming catalyst a nickel type catalyst, preferably one essentially of silica free catalyst, is used. 5. The method according to claim 4, characterized in that the catalyst is made of aluminum oxide is composed of precipitated nickel. 6. The method according to any one of claims 1 to 5, characterized in that the steam reforming process is carried out at 600 to 1000 ° C. 7. The method according to any one of claims 1 to 6, characterized in that a pressure of 1 to 20 atmospheres, preferably 10 to 15 atmospheres, is used. 8. The method according to any one of claims 1 to 7, characterized in that the water vapor ratio is less than 6 and at least 2.5 moles per carbon atom. 9. The method according to any one of claims 1 to 8, characterized in that the concentration the sulfur-containing impurity in the hydrocarbon reaction medium by introducing it a regulated amount of the sulfur-containing impurity in the initially a lower one as the hydrocarbon reaction medium containing the required concentration desired range is set. 10. The method according to claim 9, characterized in that the regulated amount of the sulfur-containing Contamination from mixing a hydrocarbon with a much higher one Concentration of sulfur-containing impurities with a hydrocarbon that is essentially no or less than the desired concentration of sulfur-containing impurity contains, is introduced. 11. The method according to any one of claims 1 to 10, characterized in that the hydrocarbon reaction mixture is produced by desulfurizing an impure hydrocarbon under such conditions that the required Amount of sulfur remains. Considered publications:
U.S. Patent No. 2,711,419. O 209 507/157 1.