Catalytic method of producing mercaptans from thioethers
The process for preparing a mercaptan from a thioether and hydrogen sulphide is carried out in the presence of hydrogen and a catalyst composition comprising a strong acid, such as a heteropolyacid, and at least one metal belonging to group VIII of the Periodic Table.
1 . Process for preparing a mercaptan comprising contacting a thioether and hydrogen sulphide, in the presence of hydrogen and a catalyst composition comprising a strong acid and at least one metal selected from group VIII of the Periodic Table.
2 . Process according to claim 1 , wherein the strong, acid is selected from the group consisting of:
(a) one or mole heteropolyacids selected from the group H 3 PW 12 O 40 .nH 2 O, H 4 SiW 12 O 40 .nH 2 O or H 6 P 2 W 18 O 62 .nH 2 O, in which n is an integer representing the number of molecules of water of crystallization, and is between 0 and 30, potassium, rubidium, caesium or ammonium salts thereof and mixtures of such salts;
(b) a sulphated zirconium oxide,
(c) a tulngstic zirconium oxide,
(d) a zeolite, and
(e) a cationic resin.
3 . Process according to 1 , wherein the strong acid is selected from the group potassium, rubidium, caesium or ammonium salts or a mixture of such salts of H 3 PW 12 O 40 .nH 2 O, H 4 SiW 12 O 40 .nH 2 O or H 6 P 2 W 18 O 62 .nH 2 O, in which n is an integer representing the number of molecules of water of crystallization, and is between 0 and 30, a sulphated zirconium oxide, a tungstic zirconium oxide, a zeolite, and a cationic resin.
4 . Process according to claim 1 , wherein the catalyst composition comprises:
from 90% to 99.9%, by weight of strong acid, and
from 0.01% to 10%, by weight of at least one metal from group VIII.
5 . Process according to claim 1 , wherein the strong acid is a heteropolyacid selected from the group H 3 PW 12 O 40 .nH 2 O, H 4 SiW 12 O 40 .nH 2 O or H 6 P 2 W 18 O 62 .nH 2 O, in which n is an integer representing the number of molecules of water of crystallization, and is between 0 and 30.
6 . Process according to claim 5 , wherein the catalyst composition comprises:
from 10% to 60%, by weight of strong acid,
from 0.01% to 10%, by weight of at least one metal from group VIII, and
from 30% to 80%, by weight of a support selected fibo silica SiO 2 , alumina Al 2 O 3 , titanium dioxide TiO 2 , zirconium oxide ZrO 2 , and activated carbon.
7 . Process according to claim 6 , wherein the strong acid is 12-phosphotungstic acid.
8 . Process according to one of to claim 1 , wherein the at least one metal is selected from iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum.
9 . Process according to claim 1 , wherein the at least one metal is selected from palladium, ruthenium, and platinum.
10 . Process according to claim 1 , wherein the at least one metal is palladium.
11 . Process according to claim 1 wherein the catalyst composition comprises approximately 40% by weight of 12-phosphotungstic acid, 1% of palladium and 59% of silica.
12 . Process according to claim 1 , wherein the hydrogen is introduced in an amount corresponding to a molar H 2 S/H 2 ratio of between 10 and 200.
13 . Process according to claim 1 , wherein the thioether has the general formula:
R—S—R′ (I)
in which R and R′, which are identical or different, represent a linear or branched alkyl radical of 1 to 20 carbon atoms, or else a cycloalkyl radical of 3 to 7 carbon atoms.
14 . Process according to claim 1 , wherein the hydrogen sulphide is introduced in an amount corresponding to a molar H 2 S/thioether ratio of between 1 and 40.
15 . Process according to claim 1 , wherein the catalyst composition comprises:
from 98.5% to 99.9%, by weight of strong acid, and
from 0.05% to 1.5%, by weight of at least one metal from group VIII.
16 . Process according to claim 5 , wherein the catalyst composition comprises:
from 25 to 50%, by weight of strong acid,
from 0.1% to 2%, by weight of at least one metal from group VIII, and
from 48% to 75%, by weight of a support selected from silica SiO 2 , alumina Al 2 O 3 , titanium dioxide TiO 2 , zirconium oxide ZrO 2 , and activated carbon.
17 . Process according to claim 1 , wherein the hydrogen is introduced in an amount corresponding to a molar H 2 S/H 2 ratio of between 50 and 100.
18 . Process according to claim 1 , wherein the hydrogen sulphide is introduced in an amount corresponding to a molar H 2 S/thioether ratio of between 2 and 30.
19 . Process according to claim 1 , wherein the hydrogen sulphide is introduced in an amount corresponding to a molar H 2 S/thioether ratio of between 2 and 10.
20 . Process according to claim 1 , wherein n is between 6 and 20.
21 . Process according to claim 7 , wherein said 12-phosphotungstic acid is impregnated on silica.
22 . Process according to claim 13 , wherein said linear or branched alkyl radical has 1 to 12 carbon atoms.