CA1171432A

CA1171432A - Process for the preparation of hydrocarbons

Info

Publication number: CA1171432A
Application number: CA000388575A
Authority: CA
Inventors: Martin F.M. Post; Swan T. Sie
Original assignee: Shell Canada Ltd
Current assignee: Shell Canada Ltd
Priority date: 1980-11-28
Filing date: 1981-10-23
Publication date: 1984-07-24
Also published as: NZ199086A; FR2495134B1; DE3146927A1; IT8125301A0; BE890996A; BR8107699A; GB2088407A; IN157810B; NL8006484A; AU7789881A; DE3146927C2; GB2088407B; AU542034B2; FR2495134A1; IT1140495B; JPS57118524A; ZA818222B

Abstract

ABSTRACT

Two stage process for the preparation of hydrocarbons from syngas with a H2/CO mol. ratio between 1.0 and 2.0 in which the syngas is contacted in a first stage with a Fe-comprising catalyst composition having Fischer-Tropsch as well as CO-shift activity followed by contacting at least the H2and CO separated from the first stage product in a second stage with a mono- or bifunctional catalyst comprising a Ni, Co or Ru Fischer-Tropsch function.

Description

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A PROCESS ~OR THE PREPARATION OF HYDROCARBONS

The invention relates to a process for the prepa-ration of a hydrocarbon mixture from a mixture of carbon monoxide and hydrogen w:ith an H2/CO molar ratio of less than 2.0, using an iron-containing bifunctional catalyst or catalyst combination which, in addition to having activity for the conversion of an /CO mixture into substantially hydrocarbons, has activity for the conversion of an H20/CO mixture into an H2/C02 mixture.

An investigation by the Applicant concerning this process has shown that the use of high space velocities has certain drawbacks. When the process is used for the conversion of H2/CO mixtures with an H2/CO molar ratio of less than 1.0, the stability of the bifunctional catalyst or catalyst combination is poor. When the process is used for the conversion of H2/CO mixtures with an H2/CO molar ratio between 1.0 and 2.0, a low conversion is obtained. Further investigation by the Applicant concerning this process has shown that these drawbacks can be overcome by contacting carbon monoxide and hydrogen present in the reaction product, if desired together with other components from the reaction product, in a second step with a nickel, cobalt or ruthenium-containing monofunctional catalyst, which has activity for the ~' .. . . . . ..

:

43t;2 conversion o~ an H2/C0 mixture into substantially hydrocarbons, on the understanding that i.f the feed for the second step has an H2/C0 molar ratio of less than 1.5, water is added to this feed, and that in the second step a nickel, cobalt or ruthenium-containing bifunctional catalyst or catalyst combination is used which, in addition to having activity for the conversion of an H2/C0 mixture into substantially hydrocarbons, has activity for the conversion of an H20/C0 mixture into an H2/C02 mixture.
The present invention therefore relates to a process for the preparation of a hydrocarbon mixture, in which process a mixture of carbon monoxide and hydrogen with an H2/C0 molar ratio of less than 2.0 is contacted in a first step with an iron-containing bifunctional catalyst or catalyst combination as defined above, and in which process carbon monoxide and hydrogen present in the reaction product from the first step if desired, together with other components of this reaction product, are contacted in a second step with a nickel, cobalt or ruthenium-containing monofunctional catalyst as defined above, on the understanding that if the feed for the second step has an H2/C0 molar ratio of less than 1.5, water is added to this feed, and that in the second step use is made of a nickel, cobalt or ruthenium-containing bifunctional catalyst or catalyst combination as defined above.

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The Dutch patent application No. 8003215, ~iled on 3 June 1980, relates to a process for the preparation of a hydrocarbon midxture, in which process a mixture of carbon monoxide and hydrogen with an H2/C0 molar ratio of less than 1.0 is contacted in a first step with an iron containing bifunctional catalyst or oatalyst combination as defined above, and in which process carbon monoxide and hydrogen present in the reaction product from the first skep, if desired together with other components of this reaction product, are contacted in a second step with a cobalt or ruthenium-containing monofunctional catalyst as defined above, on the understanding that if the feed for the second step has an H2/C0 molar ratio of less than 1.5, water is added to this feed, and that in the second step a cobalt or ruthenium-containing bifunctional catalyst or catalyst combination as defined above is used.
The present patent application therefore relates to a process for the preparation of a hydrocarbon mixture, in which process a mixture of carbon monoxide and hydrogen with an H2/C0 molar ratio of 1.0-2.0 is contacted in a first step with an iron-containing bifunctional catalyst or catalyst combination as defined above, and in which process carbon monoxide and hydrogen present in the reaction product from the first step, if desired together with other components of this ~ 3~

reaction product, are contacted in a second step with a nickel, cobalt or ruthenium containing monofunctional catalyst as defined above, on the understanding that, if the feed for the second step has an H2/C0 molar ratio of less than 1.5, water is added to this feed, and that in the second step use is made of a nickel, cobalt or ruthenium-containing bifunctional catalyst or catalyst combination as defined above.
In the process according to the invention the starting material is an H2/C0 mixture with an H2/C0 molar ratio of less than 2Ø Such H2/C0 mixtures can very suitably be prepared by steam gasification of a carbon-containing material. Examples of such materials are brown coal, anthracite, coke, crude mineral oil and fractions thereof and oils produced from tar sand and bituminous shale. The steam gasification is preferably carried out at a temperature of 900-1500C and a pressure of 10-100 bar. In the process according to the invention the preferred starting material is an H2/C0 mixture with an H2/C0 molar ratio of more than 0.25.
The iron-containing bifunctional catalysts or catalyst combinations that are suitable for use in the first step in the process according to the invention should in addition to having activity for the conversion of an H2/C0 mixture into substantially hydrocarbons, have activity for the conversion of an H20/C0 mixture into an H2/C02 mixture. It is preferred to use in 5 ~ ~7~ 3~

the first step of the process a bifunctional catalyst prepared by imprenation and containing iron on a carrier. Examples of such catalysts are:
(a) Catalysts which contain 30-75 pbw iron and 5-40 pbw magnesiu~ per 100 pbw alumina and which have been prepared by impregnating an alumina carrier with one or more aqueous solutions of salts of iron and magnesium, followed by drying the composite, calcining at a temperature of 700 1200C and reducing. Particularly preferred catalysts are those containing in addition to 40-60 pbw iron and 7.5-30 pbw magnesium, 0.5-5 pbw copper as reduction promotor and 1-5 pbw potassium as selectivity promotor per 100 pbw alumina, and which have been calcined at 750-850C and reduced at 250-350C.
(b) Catalysts which contain 10-40 pbw iron and 0.25-10 pbw chromium per 100 pbw silica and which have been prepared by impregnating a silica carrier with one or more aqueous solutions of salts of iron and chromium, followed by drying the composite, calcining and reducing at a temperature of 350-750C.
Particularly preferred catalysts are those which contain in addition to 20-35 pbw iron and 0.5-5 pbw chromium, 1-5 pbw potassium as selectivity promotor per 100 pbw silica, and which have been calcined at 350-700C and reduced at 350-500C.
The first step of the process according to the ` ' invention can very suitably be carried out by conducting the feed in upward or downward direction through a vertically mounted reactor in which a fixed or a moving bed of the iron-containing bifunctional catalyst or catalyst combination is present. The first step may, for instance, be carried out in fixed-bed operation, bunkerflow operation, ebullient-bed operation or fluidized-bed operation. The first step of the process is preferably carried out under the following conditions:
a temperature of 200-350C and in particular of 250-350C, a pressure of 10-70 bar and in particular of 20-50 bar and a space velocity of 500-5000 and in particular of 500-2500 Nl gas/l catalyst/h.
In the process according to the invention carbon monoxide and hydrogen present in the reaction product from the first step are used as the feed for the second step. In addition to carbon monoxide and hydrogen, the feed for the second step may contain other components of the reaction product from the first step. For instance, it is possible to use as the feed for the second step the C2- fraction or C~~ fraction of the reaction product from the first step, and it is even possible to use the total reaction product from the first step as the feed for the second step. In the second step of the process according to the invention the intention is to convert as much as possible of the carbon monoxide ` '' ' .
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present in the feed for the second step into substanti-ally hydrocarbons over a monofunctional nickel, cobalt or ru~henium-containing catalyst with activity for this reaction. To this end the H2/C0 molar ratio in the feed for the second step should be at least 1.5 and preferably 1.75-2.25. When an H2/C0 mixture with a high H2/C0 molar ratio is used as the feed for the first step, the process according to the invention can yield a reaction product from the first step that has an H2/C0 molar ratio of at least 1.5 and that is suitable as such for conversion over the said catalyst in the second step.
If in the process according to the invention the first step yields a reaction product with an H2/C0 molar ratio of less than 1.5, water should be added to the feed for the second step, and in the second step a nickel, cobalt or ruthenium-containing bifunctional catalyst or catalyst combination should be used which, in addition to having activity for the conversion of an H2/C0 mixture into substantially hydrocarbons, has activity for the conversion of an H20/C0 mixture into an H2/C02 mixture.
If in the process according to the invention the feed for the second step has an H2/C0 molar ratio of less than 1.5, it is preferred to use in the second step a bifunctional catalyst combination composed of two separate catalysts, which, for the ~'7~

sake of convenience, will be designated catalyst A and catalyst B. Catalyst A is the nickel, cobalt or ruthenium-containing catalyst with activity for the conversion of an H2/C0 mixture into substantially hydrocarbons, and catalyst B is the catalyst with activity for the conversion of an H20/C0 mixture into an H2~C02 mixture. Both when using a monofunc-tional catalyst and when using a bifunctional catalyst combination in the second step of the process according to the invention, preference is given to a cobalt catalyst and in particular to a catalyst prepared by impregnation containing cobalt on a carrier, as catalyst A. Very suitable for the present purpose are catalysts which contain 10-40 pbw cobalt and 0.25-5 .
pbw zirconium, titanium or chromium, and which have been prepared by impregnating a silica carrier with one or more aqueous solutions of salts of cobalt and zirconium, titanium or chromium, followed by drying the composite, calcining at 350-700C and reducing at 200-350C. Suitable B-catalysts are pre-eminently catalysts which contain copper and zinc and in which the Cu/Zn atomic ratio lies between 0.25 and 4Ø In the nickel, cobalt or ruthenium-containing bifunctional catalyst combinations catalysts A and B
may be present as a physical mixture. When the second step of the process is carried out using a fixed catalyst bed, this bed is preferably built up of two .

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' _9_ or more alternating layers of particles of catalyst B
and catalyst A successively. The addition of water to the feed for the second step together with the use of a bifunctional catalyst combination in the second step can, in the process according to the invention, be effected both in cases where the reaction product from the first step has an H2/C0 molar ratio of less than 1.5, and in cases where the reaction product from the first step already has an H2/C0 molar ratio of at least 1.5, but where it is desirable that the feed which is contacted in the second step with catalyst A should have a higher H2/C0 molar ratio.
If in the process according to the invention an embodiment is chosen in which water is added to the feed for the second step and a bifunctional cata1yst combination is used in the second step, the required amount of water is determined substantiaIly by the H2/C0 molar ratio of the feed for the second step, the activity of the catalyst combination for the conversion of an H20/C0 mixture into an H2/C02 mixture and the desired H2/C0 molar ratio of the product that is contacted with catalyst A.
The second step of the process according to the invention can very suitably be carried out by conducting the feed in upward or downward direction through a vertically mounted reactor in which a fixed bed of the monofunctional catalyst or of the bifunctional catalyst or catalyst combination is present. I'he second step of the process can also be carried out using a suspension of the catalyst or catalyst combination in a hydrocarbon oil. The second step of the process is preferably carried out under the followin~s conditions:
a temperature of 125-350C and in particular of 175-275C and a pressure of 1-150 bar and in particular of 5-100 bar.
The two-step process according to the invention can very suitably be employed as part of a three-step process for the preparation of, inter alia, middle distillates ~rom an H2/C0 mixture. In this case at least the part of the reaction product of the second step whose initial boiling point lies above the final boiling point of the heaviest middle distillate desired as the end product, is subjected in a third step to a catalytic hydrotreatment.
The invention will now be explained with reference to the following example.
Example In the investigation use was made of the following catalysts:

Catalyst 1 A Co/Zr/SiO2 catalyst containing 25 pbw cobalt and 108 pbw zlrconium per 100 pbw silica and prepared ' a.~3z by impregnating a silica carrier with an aqueous solution containing a cobalt salt and a zirconium salt, followed by drying the composite, calcining at 500C and reducing at 2800C.

Catalyst 2 An Fe/Mg/Cu/K/Al203 catalyst containing 50 pbw iron, 20 pbw magnesium, 2.5 pbw copper and 4 pbw potassium per 100 pbw alumina and prepared by impregna-ting an alumina carrier with an aqueous soluti.on containing an iron salt, a magnesium salt, a copper salt and a potassium salt, followed by drying the composite, calcining at 800OC and reducing at 325C.

Catalyst 3 A Cu/Zn/Al203 catalyst with a Cu/Zn atomic ratio of 0.55.

Catalyst mixture I

Catalyst mixture I consisted of a layer of catalyst 3 and a layer of catalyst 1 in a volume ratio of 1:2.
Catalysts 1 and 2 and catalyst mixture I were tested for the preparation in one or two steps of a hydrocarbon mixture from an H2/C0 mixture. The test was carried out in one or two reactors of 50 ml each in which a fixed catalyst bed was present. I'he test consisted of ten experiments. The experiments 1, 3, 6 and 9 were carried out in one step, the other experiments in two steps. In all experiments catalyst 2 was employed in the first step and the temperature was 280C. In all experiments carried out in two steps the temperature in the second step was 230C. In all experiments the pressure was 30 bar and the space velocity based on the total catalyst system was 1000 Nl.l-1.h-1. In the experiments 2, 5, 7, 8 and 10 the total reaction product from the first step was used as the feed for the second step. In experiment 4 the C4- fraction of the product from the first step was used as the feed for the second step. The results of the experiments are listed in the table.

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Of t;he experiments listed in the table, only the two-step experiments 2, 4, 5, 7, 8 and lO are experiments according to the invention. The one-step experiments l, 3, 6 and 9 are outside the scope of the invention. They have been included in the patent application for comparison. Of the two step experiments

2, 4, 5, 7 8 and 10, only the experiments 7, 8 and 10 are experiments according to the present patent ap-plication. the two-step experiments 2, 4 and 5 are experiments according to Dutch patent application No.
8003215.
The advantages of the two-step process according to the invention as regards conversion of the H2/C0 mixture and stability of the iron-containing bifunctional catalyst are evident when the results of the following experiments are compared:
experiment 2 with experiment 1, experiments 4 and 5 with experiment 3, - experiments 7 and 8 with experiment 6, and experiment 10 with experiment 9.
, ~published January 4, 1982.

B

Claims

1. A process for the preparation of a hydrocarbon mixture, characterized in that a mixture of carbon monoxide and hydrogen with an H2/CO molar ratio of 1.0-2.0 is contacted in a first step with an iron-containing bifunctional catalyst or catalyst combination which, in addition to having activity for the conversion of an H2/C0 mixture into substantially hydrocarbons, has activity for the conversion of an H20/C0 mixture into an H2/C02 mixture, and in that carbon monoxide and hydrogen present in the reaction product from the first step, if desired together with other components of this reaction product, are contacted in a second step with a nickel, cobalt or ruthenium-containing monofunctional catalyst which has activity for the conversion of an H2/C0 mixture into substantially hydrocarbons, on the understanding that, if the feed for the second step has an H2/C0 molar ratio of less than 1.5, water is added to this feed, and that in the second step use is made of a nickel, cobalt or ruthenium-containing bifunctional catalyst or catalyst combination which, in addition to having activity for the conversion of an H2/C0 mixture into substantially hydrocarbons, has activity for the conversion of an H20/C0 mixture into an H2/C02 mixture.

2. A process according to claim 1, characterized in that in the first step use is made of a bifunctional catalyst prepared by impregnation and containing iron on a carrier.

3. A process according to claim 1, characterized in that use is made of a catalyst containing 30-75 pbw iron and 5-40 pbw magnesium per 100 pbw alumina and which has been prepared by impregnating an alumina carrier with one or more aqueous solutions of salts of iron and magnesium, followed by drying the composite calcining at a temperature Or 700-1200°C and reducing.

4. A process according to claim 2~ characterized in that use is made of a catalyst containing 10-40 pbw iron and 0. 25-10 pbw chromium per 100 pbw silica and which has been prepared by impregnating a silica carrier with one or more aqueous solutions of salts of iron and chromium, followed by drying the composite, calcining and reducing at a temperature of 350-750°C.

5. A process according to claim 1, characterized in that the first step is carried out at a temperature o~ 200-350°C, a pressure of 10-70 bar and a space velocity of 500-5000 Nl gas/l catalyst/h.

6. A process according to claim 1, characterized in that as the catalyst with activity for the conversion of an ~2/CO mixture into substantially hydrocarbons, which catalyst is used in the second step of the process, a catalyst is employed which has been prepared by impregnation and contains cobalt on a carrier.

7. A process according to claim 6, characterized in that use is made of a catalyst which contains 10-40 pbw cobalt and 0. 25-5 pbw zirconium, titanium or chromium per 100 pbw silica and which has been prepared by impregnating a silica carrier with one or more aqueous solutions of salts of cobalt and of zirconium, titanium or chromium, followed by drying the composite, calcining at 350-700°C
and reducing at 200-350°C.

8. A process according to claim 1, characterized in that water is added to the feed for the second step and in that in the second step a bifunctional catalyst combination is used which is composed of two separate catalysts A and B, of which catalyst A
has activity for the conversion of an H2/C0 mixture into substant-ially hydrocarbons and catalyst B has activity for the conversion of an H20/CO mixture into an H2/CO2 mixture.

9. A process according to claim 8, characterized in that in the second step use is made of a fixed catalyst bed built up of two or more alternating layers of particles of catalyst B and catalyst A successively.

10. A process according to claim 1, characterized in that the second step is carried out at a temperature of 125-350°C and a pressure of 1-150 bar.