Dehydrogenation process

Claim 2

A process for dehydrogenation of alkanes which comprises contacting at least one alkane under dehydrogenation conditions with a supported platinum-group metal catalyst wherein said platinum-group metal is deposited substantially toward the surface of said support and prepared by the process which comprises: (a) impregnating a porous support with an aqueous solution of a platinum-group metal sulfite and a rhenium compound wherein said platinum-group metal is at least one of platinum, iridium, osmium, palladium, rhodium, and ruthenium, (b) drying the thus-prepared composite, and (c) heating the thus-dried composite at a temperature sufficient to decompose said sulfite, thereby producing said supported platinum-group metal catalyst.

Claim 3

A process according to claim 1 wherein said platinum-group metal sulfite is represented by the formula A 6 M(SO 3 ) 4 wherein A is ammonium or a member of Group IA of the Periodic Table, and M is a said platinum-group metal.

Claim 4

A process according to claim 2 wherein said (a) impregnating step is conducted by treating said support with an aqueous solution of said platinum-group metal sulfite at temperatures of about 10° C. to 50° C., for a time of about 1 to 1000 seconds, employing a concentration of aqueous solution of said platinum-group metal sulfite sufficient to achieve about 0.0001 to 10 weight percent total of said platinum-group metal and rhenium in the resulting supported platinium-group metal catalyst; said (b) drying step is conducted at a temperature of about 50° C. to 125° C.; and said (c) decomposition step is conducted at a temperature of about 200° C. to 600° C.

Claim 5

A process according to claim 3 wherein the resulting catalyst contains about 0.1 to 1 weight percent total of platinum-group metal and rhenium.

Claim 6

A process according to claim 3 wherein said aqueous solution of said platinum-group metal sulfite contains about 0.001 molar to saturated relative to platinum-group metal sulfite.

Claim 7

A process according to claim 3 wherein said porous support is selected from the aluminas, titania, zirconia, magnesia, thoria, chromia, zinc titanate, zinc aluminate, and SnO/ZnAl 2 O 4 .

Claim 8

A process according to claim 6 wherein said support is SnO/ZnAl 2 O 4 , said platinum-group metal is platinum, and said platinum-group metal sulfite is hexammonium platinum tetrasulfite.

Claim 9

A process according to claim 1, comprising the preliminary step of prewetting with water said porous support effective to substantially saturate with water the pores of said porous support and thereafter (a) contacting with said aqueous solution of said platinum metal sulfite and rhenium compound.

Claim 10

A process according to claim 5 wherein said (c) decomposition step is conducted in an oxygen-containing atmosphere and the resulting supported platinum-group metal catalyst is (d) subsequently treated with hydrogen at elevated temperatures.

Claim 11

A process according to claim 1 wherein said alkane is an alkane of C 3 to C 10 , wherein said catalyst contains about 0.0001 to 10 weight percent total platinum-group metal and rhenium, and said support is selected from the group consisting of aluminas, titania, zirconia, magnesia, thoria, chromia, zinc titanate, zinc aluminate, and SnO/ZnAl 2 O 4 .

Claim 12

A process of claim 10 wherein said supported platinum-group metal catalyst contains said rhenium up to an amount equal to one-half the total amount of platinum-group metal and rhenium present.

Claim 13

A process of claim 11 wherein in said supported platinum-group metal catalyst said platinum-group metal and rhenium content is in the range of about 0.1 to 1 weight percent.

Claim 14

A process according to claim 10 further comprising pre-soaking said porous support in water, methanol, isopropanol, ethylene glycol, or mixture thereof, prior to contacting said platinum-group metal sulfite and rhenium compound solution.

Claim 15

A process of claim 10 wherein said alkane is a C 4 or C 5 alkane.

Claim 16

A process according to claim 10 wherein said alkane is n-butane and said dehydrogenation conditions include contacting said n-butane with said supported platinum-group metal catalyst at temperatures in the range of about 480° C. to 650° C., pressures in the range of about 0 to 300 psig, hydrocarbon feed rates of about 100 to 10,000 GHSV gaseous feed per volume of catalyst per hour, and steam at a steam:hydrocarbon mole ratio of about 2:30.

Claim 17

A process according to claim 15 wherein said supported noble platinum-group metal is platinum.

Claim 18

A process according to claim 16 wherein said support is a tin oxide zinc alumina spinel support.

Claim 19

A process according to claim 15 further comprising pre-soaking said support in water, methanol, isopropanol, ethylene glycol, or mixture thereof, prior to contacting said platinum-group metal sulfite and rhenium compound solution.

Claim 20

A process of alkane dehydrogenation which comprises contacting at least one alkane under dehydrogenation conditions with a supported platinum-group metal catalyst wherein said platinum-group metal is substantially deposited at the surface of said support and said supported catalyst is prepared by the steps which comprise: (a) soaking a porous support in water, methanol, isopropanol, ethylene glycol, or mixture thereof, effective to substantially pre-wet the pores of said porous support; (b) impregnating said pre-wetted porous support with an aqueous solution of a platinum-group metal sulfite, wherein said platinum-group metal is at least one of platinum, iridium, osmium, palladium, rhodium, and ruthenium; (c) drying the thus-prepared composite; and (d) heating the thus-dried composite to a temperature sufficient to decompose said sulfite, thereby preparing said supported platinum-group metal catalyst wherein said platinum-group metal is substantially deposited at the surface of said support.

Claim 21

A process of alkane dehydrogenation which comprises contacting at least one alkane under dehydrogenation conditions with a supported platinum-group metal catalyst wherein said platinum-group metal is substantially deposited at the surface of said support and said supported catalyst is prepared by the steps which comprise: (a) soaking a porous support in water, methanol, isopropanol, ethylene glycol, or mixture thereof, effective to substantially pre-wet the pores of said porous support; (b) impregnating said pre-wetted porous support with an aqueous solution of a platinum-group metal sulfite, wherein said platinum-group metal is at least one of platinum, iridium, osmium, palladium, rhodium, and ruthenium; (c) drying the thus-prepared composite; and (d) heating the thus-dried composite to a temperature sufficient to decompose said sulfite, thereby preparing said supported platinum-group metal catalyst wherein said platinum-group metal is substantially deposited at the surface of said support.

Claim 22

A process according to claim 19 wherein said supported platinum-group metal catalyst further contains a rhenium compound.

Claim 23

A process according to claim 19 wherein said platinum-group metal sulfite is represented by the formula A 6 M(SO 3 ) 4 , A is ammonium or a member of Group IA of the Periodic Table, and M is a said platinum-group metal; said (b) impregnating step is conducted by treating the said pre-wetted porous support with an aqueous solution of said platinum-group metal sulfite and rhenium compound where employed at temperatures in the range of about 10° C. to 50° C., for a time of about 1 to 1000 seconds, employing a concentration of aqueous solution of said platinum-group metal sulfite sufficient to achieve about 0.0001 to 10 weight percent said platinum-group metal including rhenium where employed in the resulting supported platinum-group metal catalyst; said (c) drying is conducted at a temperature in the range of about 50° C. to 125° C.; and said (d) decomposition step is conducted at a temperature of about 200° C. to 600° C.

Claim 24

A process according to claim 21 wherein said catalyst contains about 0.1 to 1 weight percent platinum-group metal including rhenium where employed.

Claim 25

A process according to claim 22 wherein said porous support is selected from the aluminas, titania, zirconia, magnesia, thoria, chromia, zinc titanate, zinc aluminate, and SnO/ZnAl 2 O 4 .

Claim 26

A process according to claim 23 wherein said support is said SnO/ZnAl 2 O 4 , said noble platinum-group metal is platinum, and said platinum-group metal sulfite is hexammonium platinum tetrasulfite.

Claim 27

A process according to claim 21 wherein said (d) decomposition step is conducted in an oxygen-containing atmosphere and the resulting supported platinum-group metal catalyst is subsequently (e) treated with hydrogen at elevated temperatures.

Claim 28

A process according to claim 24 wherein said alkane is butane.

Claim 29

A process according to claim 24 wherein said SnO/ZnAl 2 O 4 supported platinum metal catalyst further contains said rhenium up to an amount equal to one-half the total amount of platinum-group metal and rhenium present.

Claim 30

A process according to claim 26 wherein in said SnO/ZnAl 2 O 4 supported platinum-group metal catalyst the total of said platinum-group metal and rhenium where employed is in the range of about 0.1 to 1 weight percent.