Hierarchical aluminophosphates as catalysts for the Beckmann rearrangement
Methods for producing lactams from oximes by performing a Beckmann rearrangement using a hierarchical porous aluminophosphate catalyst having interconnected microporous and mesoporous networks are provided. Exemplary catalysts include a plurality of weak Brønsted acid active sites, including silicon-containing aluminophosphates having the IZA framework code AFI, such as SAPO-5, CHA, such as SAPO-34, and FAU, such as SAPO-37.
1. A method of making a catalyst for a Beckmann rearrangement reaction, wherein the catalyst is a hierarchical porous catalyst with a silicoaluminophosphate framework, a plurality of interconnected micropores, and a plurality of mesopores interconnected with the micropores, the method comprising:
combining an organosilane surfactant, at least one structure directing agent, a metal precursor, a silicon source, phosphoric acid, and water to form a mixture; wherein combining the organosilane surfactant, the structure directing agent, the metal precursor, the silicon source, the phosphoric acid, and the water to form the mixture includes:
mixing the metal precursor and the at least one structure directing agent together;
adding the silicon source to the mixture of the metal precursor and the at least one structure directing agent;
adding the organosilane surfactant to the mixture after adding the silicon source;
adding the water to the mixture after adding the organosilane surfactant; and
adding the phosphoric acid to the mixture after adding the water;
heating the mixture to form a solid; and
calcining the solid to form the catalyst, wherein the organosilane surfactant includes dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride and the metal precursor includes aluminum;
wherein the catalyst is a hierarchical SAPO-34 catalyst.
2. The method of claim 1 , wherein the at least one structure directing agent includes tetramethylammonium hydroxide.
3. The method of claim 1 , wherein the silicon source includes fumed silica.
4. The method of claim 1 , wherein the metal precursor includes aluminum isopropoxide.
5. The method of claim 1 , wherein the mesopores have a pore diameter from 15 Å to 50 Å.
6. The method of claim 1 , wherein the micropores have a pore diameter from 3 Å to 10 Å.
7. A method of making a catalyst for a Beckmann rearrangement reaction, wherein the catalyst is a hierarchical porous catalyst with a silicoaluminophosphate framework, a plurality of interconnected micropores, and a plurality of mesopores interconnected with the micropores, the method comprising:
combining an organosilane surfactant, at least one structure directing agent, a metal precursor, a silicon source, phosphoric acid, and water to form a mixture; wherein combining the organosilane surfactant, the structure directing agent, the metal precursor, the silicon source, the phosphoric acid, and the water to form the mixture includes:
mixing the metal precursor and the phosphoric acid together with a portion of the water to form a first solution;
adding the organosilane surfactant to the at least one structure directing agent to form a second solution;
adding the silicon source to the second solution; and
adding the second solution including the silicon source to the first solution to form the mixture;
heating the mixture to form a solid; and
calcining the solid to form the catalyst, wherein the organosilane surfactant includes dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride and the metal precursor includes aluminum;
wherein the catalyst is a hierarchical SAPO-37 catalyst.
8. The method of claim 7 , wherein the at least one structure directing agent includes tetramethylammonium hydroxide and tetrapropylammonium hydroxide.
9. The method of claim 7 , wherein the silicon source includes fumed silica.
10. The method of claim 7 , wherein the metal precursor includes boehmite.
11. The method of claim 7 , wherein the mesopores have a pore diameter from 15 Å to 50 Å.
12. The method of claim 7 , wherein the micropores have a pore diameter from 3 Å to 10 Å.