Process for making tetrahydrofuran and 1,4-butanediol using Pd/Re hydrogenation catalyst

Claim 3

A method according to claim 1 wherein the hydrogenatable precursor is selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, succinic acid, malic acid, the esters corresponding to these acids, γ-butyrolactone and mixtures thereof.

Claim 4

A method according to claim 1 wherein the catalyst comprises about 1% to 6% of palladium and about 3% to 6% of rhenium by total weight.

Claim 5

A method according to claim 3 wherein the hydrogenatable precursor is selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, succinic acid, malic acid, the esters corresponding to these acids, γ-butyrolactone and mixtures thereof.

Claim 6

A method according to claim 3 wherein the catalyst comprises about 3% palladium and about 3% of rhenium by total weight.

Claim 7

A method according to claim 5 wherein the hydrogenatable precursor is selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, succinic acid, malic acid, the esters corresponding to these acids, γ-butyrolactone and mixtures thereof.

Claim 8

A method according to claim 1 wherein the rhenium crystallites have an average size of less than 1.5 nm.

Claim 9

A method according to claim 7 wherein the hydrogenatable precursor is selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, succinic acid, malic acid, the esters corresponding to these acids, γ-butyrolactone and mixtures thereof.

Claim 10

A method according to claim 3 wherein the rhenium crystallites have an average size of less than 1.5 nm.

Claim 11

A method according to claim 9 wherein the hydrogenatable precusor is selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, succinic acid, malic acid, the esters corresponding to these acids, γ-butyrolactone are mixtures thereof.

Claim 12

A method according to claim 5 wherein the rhenium crystallites have an average size of less than 1.5 nm.

Claim 13

A method according to claim 11 wherein the hydrogenatable precursor is selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, succinic acid, malic acid, the esters corresponding to these acids, γ-butyrolactone and mixtures thereof.

Claim 16

A method according to claim 13 wherein the hydrogenatable precursor is selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, succinic acid, malic acid, the esters corresponding to these acids, γ-butyrolactone and mixtures thereof.

Claim 19

A method according to claim 15 wherein the hydrogenatable precursor is selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, succinic acid, malic acid, the esters corresponding to these acids, γ-butyrolactone and mixtures thereof.

Claim 20

A method according to claim 1 carried out at a reaction temperature of about 130° to 285° C., a hydrogen pressure of 2 MPa to 35 MPa, a hydrogen spacetime of about 1 to 10 minutes and a contact time of about 0.5 to 7 hours.

Claim 21

A method according to claim 1 carried out in aqueous solvent medium.

Claim 22

A method according to claim 15 carried out at a reaction temperature of about 130° to 285° C., a hydrogen pressure of 2 MPa to 35 MPa, a hydrogen spacetime of about 1 to 10 minutes and a contact time of about 0.5 to 7 hours

Claim 23

A method according to claim 15 carried out in aqueous solvent medium.

Claim 24

In a method for making tetrahydrofuran, 1,4-butanediol or mixtures thereof from an oxidizable maleic anhydride precursor comprising oxidizing the precursor to form maleic anhydride and reacting the maleic anhydride with hydrogen in the presence of a hydrogenation catalyst, the improvement which comprises: (i) collecting the maleic anhydride from the oxidation step in water to form an aqueous solution of maleic acid, and (ii) reacting the aqueous solution of maleic acid with hydrogen in the presence of a catalyst on a carbon support, said catalyst comprising about 0.5% to 10% of palladium and about 1% to 10% of rhenium by total weight, the palladium being present in the form of crystallites having an average size of about 10 nm to 25 nm and the rhenium being present in the form of a highly dispersed phase of crystallites having an average size of less than about 2.5 nm.

Claim 25

In a method for making tetrahydrofuran, 1,4-butanediol or mixtures thereof from an oxidizable maleic anhydride precursor comprising oxidizing the precursor to form maleic anhydride and reacting the maleic anhydride with hydrogen in the presence of a hydrogenation catalyst, the improvement which comprises: (i) collecting the maleic anhydride from the oxidation step in water to form an aqueous solution of maleic acid, and (ii) reacting the aqueous solution of maleic acid with hydrogen in the presence of a catalyst on a carbon support, said catalyst comprising about 0.5% to 10% of palladium and about 1% to 10% of rhenium by total weight, the palladium being present in the form of crystallites having an average size of about 10 nm to 25 nm and the rhenium being present in the form of a highly dispersed phase of crystallites having an average size of less than about 2.5 nm.

Claim 26

A method according to claim 21 carried out continuously.

Claim 27

In a method for making tetrahydrofuran, 1,4-butanediol or mixtures thereof from an oxidizable maleic anhydride precursor comprising oxidizing the precursor to form maleic anhydride and reacting the maleic anhydride with hydrogen in the presence of a hydrogenation catalyst, the improvement which comprises: (i) collecting the maleic anhydride from the oxidation step in water to form an aqueous solution of maleic acid, and (ii) reacting the aqueous solution of maleic acid with hydrogen in the presence of a catalyst on a carbon support, said catalyst comprising about 0.5% to 10% of palladium and about 1% to 10% of rhenium by total weight, made by the method comprising, in sequence: (a) impregnating the carbon support with a source of palladium, said palladium being in solution, (b) removing the solvent and heating the palladium impregnated carbon at a temperature of about 150° C. to 550° C. under reducing conditions, (c) applying to the palladium impregnated carbon a source of rhenium that is in solution, and (d) removing the solvent.

Claim 28

In a method for making tetrahydrofuran, 1,4-butanediol or mixtures thereof from an oxidizable maleic anhydride precursor comprising oxidizing the precursor to form maleic anhydride and reacting the maleic anhydride with hydrogen in the presence of a hydrogenation catalyst, the improvement which comprises: (i) collecting the maleic anhydride from the oxidation step in water to form an aqueous solution of maleic acid, and (ii) reacting the aqueous solution of maleic acid with hydrogen in the presence of a catalyst on a carbon support, said catalyst comprising about 0.5% to 10% of palladium and about 1% to 10% of rhenium by total weight, made by the method comprising, in sequence: (a) impregnating the carbon support with a source of palladium, said palladium being in solution, (b) removing the solvent and heating the palladium impregnated carbon at a temperature of about 150° C. to 550° C. under reducing conditions, (c) applying to the palladium impregnated carbon a source of rhenium that is in solution, and (d) removing the solvent.

Claim 29

A method according to claim 23 carried out continuously.

Claim 30

A method for making tetrahydrofuran, 1,4-butanediol or mixtures thereof according to claim 23 comprising the additional step of (v) heating the catalyst composite of step (iv) at a temperature of about 150° C. under reducing conditions.

Claim 31

A method according to claim 25 carried out continuously.

Claim 32

A method according to claim 1 characterized by controlling the relative ratio of tetrahydrofuran to 1,4-butanediol by varying one or more variables selected from operating temperature, contact time and hydrogen spacetime.

Claim 33

A method according to claim 15 characterized by controlling the relative ratio of tetrahydrofuran to 1,4-butanediol by varying one or more variables selected from operating temperature, contact time and hydrogen spacetime.

Claim 34

A method according to claim 27 characterized by increasing the relative ratio of tetrahydrofuran to 1,4-butanediol by increasing one or more of the variables selected from operating temperature, contact time, and hydrogen spacetime.

Claim 35

A method according to claim 28 characterized by increasing the relative ratio of tetrahydrofuran to 1,4-butanediol by increasing one or more variables selected from operating temperature, contact time, and hydrogen spacetime.