Catalyst for a process for obtaining hydrogen through reforming hydrocarbons with steam, process for preparing the catalyst and use thereof in the process
The present invention relates to a catalyst for producing gaseous hydrogen current or hydrogen-rich currents through hydrocarbon reforming with water vapor. Said catalyst comprises at least one support, an active phase and at least two promoting agents, and is characterized in that it is a metal-type-supported solid in which the active phase comprises at least one transition metal chosen from group VIII, and at least one promoting agent chosen from the alkaline-earth or transition metals; and the support comprises at least one mixed oxide with a basic nature, and at least one promoting agent chosen from among the lanthanides group. The invention also has as an object the process for preparing the catalyst, as well as its use in the process for obtaining the hydrogen or hydrogen-rich gas from hydrocarbons, in different operating conditions and using various types of hydrocarbons. The catalyst to which this invention pertains has elevated activity and selectivity toward the gasification of hydrocarbons, as well as a high resistance to various deactivation mechanisms which the catalyst undergoes during the reforming process with water vapor.
1. A catalyst for obtaining hydrogen or a hydrogen-rich gas through aliphatic hydrocarbon reforming with steam, comprising:
a support which comprises
at least one mixed oxide having a basic character comprising Mg and Al in a molar proportion of Al/(Al+Mg) of 0.25, and
a promoting agent of the support consisting of cerium oxide in a proportion of 1% to 20% in weight; and
an active phase, which is 1% to 15% in weight of the catalyst, comprising
a transition metal consisting of nickel in a proportion of 1% to 15% in weight,
a first promoting agent consisting of cobalt in a proportion of 1% to 20% in weight, and
a second promoting agent selected from rhenium,
wherein said catalyst contains small crystals of 3 to 10 nm highly dispersed within a matrix with an elevated superficial area (BET) from 200 to 300 m 2 /g, and is obtained by a process comprising:
preparing a precursor of the catalyst in a synthesis stage, wherein the precursor is a double layered hydroxide with a hydrotalcite-type structure which contains a transition metal consisting of nickel, a promoting agent consisting of cobalt, a promoting agent of the support consisting of cerium oxide, Mg and Al;
forming a mixed oxide by calcination of the precursor prepared in the synthesis stage in a thermal decomposing stage
impregnating the mixed oxide obtained in the decomposing stage with rhenium in an impregnation stage before subjecting it to an activation stage; and
reducing the mixed oxide of the decomposing stage to obtain the catalyst in the activation stage.
2. The catalyst according to claim 1 , wherein the catalyst comprises
from 3% to 10% in weight of the active phase, and
from 5% to 15% in weight of each of the promoting agents.
3. The catalyst according to claim 1 , wherein the mixed oxide of the support is magnesium and aluminum.
4. The catalyst according to claim 1 , wherein the catalyst comprises
nickel, in a proportion from 3% to 10% in weight,
cobalt, in a proportion from 5% to 15% in weight, and
cerium oxide, in a proportion from 5% to 15% in weight.
5. The catalyst according to claim 1 , wherein the catalyst comprises
nickel, in a proportion from 5% to 7% in weight,
cobalt, in a proportion from 6% to 9% in weight, and
cerium oxide, in a proportion from 7% to 10% in weight.
6. The catalyst according to claim 1 , wherein the content of rhenium is 0.1% to 2% in weight.
7. The catalyst according to claim 1 , wherein it has an X-ray pattern which contains the peaks (degrees) and relative intensities (I/I0):
2Θ (degrees) ± 0.5
Relative Intensity (I/I 0 )
37.74
M
43.70
F
44.58
MF
51.84
M
62.78
M
where
I 0 is the intensity of the strongest peak to which a value of 100 has been assigned;
d is a weak relative intensity of 0 to 20%;
m is a medium relative intensity of 20% to 40%;
f is a strong relative intensity of 40% to 60%;
mf is a very strong relative intensity of 60% to 100%.
8. The catalyst according to claim 1 , wherein the catalyst has an X-ray pattern which contains at least two peaks (degrees) and relative intensities (I/I 0 ):
2Θ (degrees) ± 0.5
Relative Intensity (I/I 0 )
37.74
M
43.70
M
44.58
MF
51.84
D
62.78
M
wherein
I 0 is an intensity of the strongest peak to which a value of 100 has been assigned;
d is a weak relative intensity of 0 to 20%;
m is a medium relative intensity of 20% to 40%;
f is a strong relative intensity of 40% to 60%; and
mf is a very strong relative intensity of 60% to 100%.
9. The process according to claim 1 , wherein:
the synthesis stage further comprises:
preparing two solutions, a first solution containing a metal of interest and a second solution containing a precipitating base to the metal of interest,
co-adding the first and second solutions to obtain a gel,
aging the gel to crystallize a hydrotalcite phase,
washing the gel with the hydrotalcite phase to obtain a neutral pH, and
drying the gel with the hydrotalcite phase of a neutral pH,
wherein the thermal decomposing stage comprises the calcination process in an air atmosphere at a temperature of from 723K to 1273K, and
wherein the activation stage comprises reducing in a hydrogen atmosphere up to a temperature from 873K to 1173K.