Steam reforming
A process for the steam reforming of hydrocarbons comprises partially oxidizing a feedgas comprising a hydrocarbon feedstock with an oxygen-containing gas in the presence of steam to form a partially oxidized hydrocarbon gas mixture at a temperature >1200° C. and passing the resultant partially oxidized hydrocarbon gas mixture through a bed of steam reforming catalyst, wherein the bed comprises a first layer and a second layer, each layer comprising a catalytically active metal on an oxidic support wherein the oxidic support for the first layer is a zirconia.
1. A process for the steam reforming of hydrocarbons comprising;
(i) partially combusting a feedgas comprising a hydrocarbon feedstock with an oxygen-containing gas in the presence of steam at a steam:carbon ratio between 0.5 and 2, in a combustion zone using a burner apparatus to form a partially combusted hydrocarbon gas mixture and
(ii) feeding a gas consisting of the resultant partially combusted hydrocarbon gas mixture at a temperature in the range of 1200-1500° C. from the combustion zone to a steam reforming process by passing it adiabatically through a bed of steam reforming catalyst, the bed comprising a first layer and a second layer, each layer comprising a catalytically active metal on an oxidic support wherein the catalytically active metal in the first layer is rhodium, the oxidic support for the first layer is a zirconia, the catalytically active metal in the second layer is nickel and the oxidic support for the second layer is a refractory support selected from the group consisting of zirconia, alumina, calcium aluminate, magnesium aluminate, titania, magnesia and a mixture thereof
wherein the bed of steam reforming catalyst is disposed below the burner apparatus.
2. The process of claim 1 , wherein at least one of the first layer and the second layer reforming catalysts are particulate, or comprise one or more monolithic supports.
3. The process of claim 1 , wherein the oxidic support for the second layer is alumina or a calcium- or magnesium-aluminate.
4. The process of claim 1 , wherein the first layer of steam reforming catalyst has a higher geometric surface area than the second layer of steam reforming catalyst.
5. The process of claim 1 further comprising a layer of zirconia balls, pellets or tiles placed on top of the first layer of reforming catalyst.
6. The process of claim 1 , wherein the second layer comprises two or more successive layers of a steam reforming catalyst including a third and a further layer, the third or the further layer having a lower catalytic activity than that preceding it.
7. The process of claim 1 , wherein the thickness of the bed of steam reforming catalyst is in the range 3-5 meters.
8. The process of claim 1 , wherein the first layer comprises between 3 and 25% of the thickness of the bed.
9. The process of claim 1 , wherein the first layer comprises between 5 and 15% of the thickness of the bed.
10. The process of claim 1 , wherein the first layer comprises rhodium on a zirconia and the second layer comprises nickel on an alumina or magnesium- or calcium-aluminate.
11. The process of claim 1 , wherein the thickness of the bed of steam reforming catalyst is in the range 1-10 meters.
12. The process of claim 1 , wherein the first layer comprises between 1 and 50% of the thickness of the bed.
13. The process of claim 1 , wherein steam is present at a steam:carbon ratio between 0.5-1.5.
14. The process of claim 1 , wherein steam is present at a steam:carbon ratio between 0.5-1.
15. The process of claim 1 , wherein the steam reforming catalyst in the first layer comprises 0.01-1.00%, Rh by weight.
16. The process of claim 1 , wherein the steam reforming catalyst in the first layer comprises 0.05 to 0.5%, Rh by weight.