Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Reexamination Certificate
1999-01-13
2001-05-29
Langel, Wayne (Department: 1754)
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
C252S373000, C423S652000, C423S653000, C423S654000
Reexamination Certificate
active
06238816
ABSTRACT:
TECHNICAL FIELD
This invention relates to steam reforming of gaseous or liquid hydrocarbons, and more particularly to steam reforming of sulfur bearing hydrocarbons using a sulfur tolerant steam reforming catalyst.
BACKGROUND OF THE INVENTION
The present invention is directed to catalytic steam reforming of hydrocarbons. More particularly, the present invention is directed to a method for steam reforming of hydrocarbons, especially sulfur-containing hydrocarbons, using a sulfur-tolerant catalyst, and an apparatus therefor.
Steam reforming is a process whereby a hydrocarbon is reacted with high temperature steam to form hydrogen, carbon monoxide, and carbon dioxide. The product gas can be reacted as a fuel or used in chemical processing.
Hydrocarbons which can be reacted according to the present invention include methane, natural gas (including landfill gas) and heavier hydrocarbons (including diesel and jet fuel).
Potential hydrocarbon feeds for the reforming process often contain large quantities of sulfur. Gas oil, for example, may contain as much as 1500 ppm sulfur. As described in greater detail below, reforming of sulfur-containing hydrocarbons can lead to increased expense.
Typically, catalytic steam reforming of natural gas or heavier hydrocarbon feeds is achieved by using a nickel catalyst. However, due to the extreme sensitivity of nickel metal to sulfur-containing compounds, which are a severe poison to the nickel catalyst, the hydrocarbon feed must generally be purified of sulfur, to less than 1 ppm, prior to steam reforming. This requirement results in additional expense for the hydrocarbon steam reforming process. Furthermore, whereas light fractions may be amenable to hydrodesulfurization, desulfurization of heavy fractions is extremely difficult.
An alternative is to use the nickel catalyst for hydrocarbon steam reforming and allow it to be poisoned by the sulfur, but to operate at higher temperatures and with higher volumes of catalyst to counteract the loss of catalyst activity due to poisoning. This alternative also results in additional cost and weight to the process.
A second alternative is to use noble metal catalysts, such as platinum, palladium, or rhodium in place of nickel. While the noble metal catalysts are very active for steam reforming and are somewhat tolerant of sulfur-containing feeds, they are very impractical because of their high cost.
Therefore, a clear need exists for a steam reforming apparatus containing a catalyst which is highly tolerant of sulfur, and which does not add significantly to the cost of using nickel catalysts.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved process for steam reforming of sulfur-containing hydrocarbons.
A further object of this invention is to provide a process for steam reforming of hydrocarbons in which sulfur-containing hydrocarbons are available as raw materials without being desulfurized in advance.
Another object of this invention is to provide a process for steam reforming of sulfur-containing hydrocarbons using a catalyst that gives stable performance, substantially without coking, and with substantially complete conversion of heavy hydrocarbon feeds.
A still further object of this invention is to provide an apparatus for the practice of the above steam reforming processes.
We have found a sulfur-tolerant catalyst, useful in the steam reforming of hydrocarbons, comprising an active phase and a support phase, and optionally a promoter, which provides substantially complete conversion of the hydrocarbon to a mixture of hydrogen, carbon monoxide, and carbon dioxide.
The present invention provides a process for steam reforming a sulfur-containing hydrocarbon feed comprising:
providing a sulfur-tolerant catalyst and contacting the catalyst with a gas stream comprising steam and a sulfur-containing hydrocarbon feed, wherein sulfur species are present in the hydrocarbon feed in an amount of at least 2 ppm;
the sulfur-tolerant catalyst comprising a mixed oxygen ion conducting and electron conducting material having both an active catalytic phase and a catalyst support phase, and optionally a promoter,
a) wherein the active catalytic phase is at least one of:
(I) A metal selected from the group consisting of Ag, Co, Cr, Cu, Fe, Pd, Pt, Ru, Rh, V, and alloys and mixtures thereof;
(II) An oxide of the general formula M
y
M′
1−y
O
x
, wherein at least one M element is different than at least one M′ element, wherein M is selected from Ba, Ce, Nb, Sm, Sr, and mixtures thereof, M′ is selected from Ti, Y, Sm, Nb and mixtures thereof, and wherein 0≦y≦1 and x is a number sufficient to satisfy the valence requirements of the other elements; and
(III) A perovskite of the general formula (A
1−a
A′
a
)(B
b
B′
1−b
)O
3−c
, wherein A is selected from lanthanides, La, Y, Pb and mixtures thereof, A′ is selected from alkaline earth metals such as Ba, Ca, Sr and mixtures thereof, B is selected from transition elements such as Fe, Co, Cr, Ni and mixtures thereof, and B′ is selected from Al, Co, Cr, Mg, Nb, Ti, Zr and mixtures thereof, wherein 0.9≦(A+A′)/(B+B′)≦1.1, preferably 0.99≦(A+A′)/(B+B′)≦1.01; and wherein 0≦a≦1; 0≦b ≦1; and c is a number that renders the composition charge neutral in the absence of an applied potential; and
b) wherein the catalyst support phase and the optional promoter is at least one of:
(IV) An oxide of the general formula Me
z
Me′
1−z
O
x
, wherein at least one Me element is different than at least one Me′ element, wherein Me is selected from Group 2a and 3a (IUPAC) metals, lanthanides, Cr, Fe, In, Nb, Pb, Si, Sn, Ta, Ti, and mixtures thereof, Me′ is selected from Al, Bi, Ce, In, Th, U, Zr and mixtures thereof, and wherein 0≦z≦1 and x is a number sufficient to satisfy the valence requirements of the other elements; and
(V) A perovskite of the general formula (D
1−d
D′
d
)(E
e
E′
1−e
)O
3−f
, wherein D is selected from lanthanides, La, Y, and mixtures thereof, D′ is selected from alkaline earth metals such as Ba, Ca, Sr and mixtures thereof, E is selected from Al, Ce, Co, Mg and mixtures thereof, and E′ is selected from transition elements such as Co, Cr, Cu, Fe, Ni, Zr and mixtures thereof, wherein 0.9≦(D+D′)/(E+E′)≦1.1, preferably 0.99≦(D+D′)/(E+E′)≦1.01; and wherein 0≦d≦1; 0≦e≦1; and f is a number that renders the composition charge neutral in the absence of an applied potential;
(VI) A fluorite structure material of the general formula Ma
(1−g−h)
Ma′
g
Ma″
h
O
2
wherein Ma is Th, Zr, Ce, or a rare earth element, Ma′ is Sc, Ti, Ta or an alkaline earth such as Ca, Sr, Ba, or Mg, Y or a rare earth element different from Ma, wherein
0
<g<0.5, Ma″ is La, Pr, Nd, or Sm, and wherein 0<h<0.2;
(VII) A pyrochlore structure material of the general formula Mb
2
Mb′
(2−k)
Mb″
k
O
7
wherein Mb is Ga, or Gd, a rare earth element such as La, Y, or Sm, Mb′ is Zr, a transition metal element such as Mo, Ti, Fe, an alkaline earth element such as Ca, Sr, Ba or Mg, wherein 0<k<0.5, and wherein Mb″ is a transition metal element different from Mb′, such as Mo, Ti, Zr, or Fe;
(VIII) A Brown-Millerite material of the general formula Mc
2
Mc′
2
O
5
wherein Mc is an alkaline earth element such as Ba or Sr, and Mc′ is Gd, Dy or Ga.
The present invention further provides an apparatus comprising a reaction zone, a catalyst bed contained within the reaction zone, and wherein the above sulfur-tolerant catalyst is included in the catalyst bed. The catalyst bed is preferably a fixed bed.
The present invention therefore also provides a process for steam reforming a sulfur bearing hydrocarbon feed, such as in a steam reforming apparatus containing a bed of the sulfur-tolerant catalyst, including introducing steam and
Brakas Adam B.
Cable Thomas L.
Milliken Christopher E.
Ruhl Robert C.
Langel Wayne
Renner Kenner Greive Bobak Taylor & Weber
Technology Management, Inc.
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