Production of mixtures of methylenedianiline and its higher homologues using calcined metal oxide-silica catalysts
The present disclosure relates to compositions, systems, and methods of forming an amine (e.g., methylenedianiline (MDA)) using an acid catalyst including, for example, a metal oxide-silica catalyst calcined at temperature(s) of about ≧500° C. to form a solid acid silica-metal oxide catalyst. A metal oxide of a solid acid silica-metal oxide catalyst may comprise alumina. A process for making a solid acid silica-metal oxide catalyst may comprise calcining an amorphous alumina-silica material at temperature(s) of about ≧500° C. and/or under an anhydrous and/or inert atmosphere. A rearrangement reaction of the condensation product of aniline and formaldehyde in the presence of a solid acid silica-metal oxide catalyst may yield more MDA and/or more desirable isomer(s) of MDA than reactions performed with a corresponding catalyst calcined at temperature(s) of less than 500° C.
1. A process for producing a methylenedianiline or a mixture of methylenedianiline and its higher homologues, said process comprising:
contacting aniline and formaldehyde under conditions that permit formation of an aminal;
contacting a catalyst composition with the aminal to form the methylenedianiline, wherein the catalyst composition comprises an anhydrous solid acid silica-metal oxide catalyst.
2. A process according to claim 1 , wherein the mole ratio of metal oxide to silica is from about 0.01 to about 0.5.
3. A process according to claim 1 , wherein the metal oxide is selected from the group consisting of Al 2 O 3 , TiO 2 , GeO 2 , SnO 2 , ZrO 2 , B 2 O 3 , Nb 2 O 5 , Ta 2 O 5 , V 2 O 5 , MoO 3 , WO 3 , and combinations thereof.
4. A process according to claim 1 , wherein (a) the metal oxide is Al 2 O 3 and (b) the solid acid silica-metal oxide catalyst (i) is substantially free of a binding agent and (ii) has an Al 2 O 3 /SiO 2 weight ratio of from about 0 to about 1.
5. A process according to claim 4 , wherein the solid acid silica-metal oxide catalyst has an Al 2 O 3 /SiO 2 weight ratio of from about 0.1 to about 0.5.
6. A process according to claim 1 , wherein the catalyst composition further comprises a binding agent.
7. A process according to claim 6 , wherein the solid acid silica-metal oxide catalyst comprises from about 5 wt % to about 60 wt % Al 2 O 3 .
8. A process according to claim 1 , wherein the methylenedianiline formed comprises at least about 40 weight percent 4,4′-methylenedianiline.
9. A process according to claim 1 , wherein the conditions (ii) to rearrange the aminal to form the methylenedianiline comprise a temperature of from about 60° to about 120° C.
10. A process according to claim 1 , wherein the conditions (ii) to rearrange the aminal to form the methylenedianiline comprise a catalyst loading of from about 2 wt % to about 15 wt % for a slurry process.
11. A process according to claim 1 , wherein the contacting aniline and formaldehyde comprises contacting aniline and formaldehyde at a molar ratio of aniline to formaldehyde of from about 2/1 to about 5/1.
12. A process according to claim 1 , wherein the contacting the aminal and the catalyst comprises contacting the aminal and the catalyst in multiple temperature zones, using either multiple fixed bed reactors or a fixed bed reactor or reactors with multiple temperature zones.
13. A process according to claim 12 , wherein the multiple temperature zones comprise a first zone having a temperature of 40-80° C. and a second zone having a temperature range of 80-150° C.
14. A process according to claim 13 , wherein the multiple temperature zones further comprise a third temperature zone of 100-150° C.