Accurate low-pressure kinetics for isobutane oxidation over phosphomolybdic acid and copper(II) phosphomolybdates

✍ Scribed by Shane M. Kendell; Trevor C. Brown; Robert C. Burns

• Book ID: 104009736
• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 450 KB
• Volume: 131
• Category: Article
• ISSN: 0920-5861
• DOI: 10.1016/j.cattod.2007.10.027

✦ Synopsis

A low-pressure steady-state technique has been used to investigate the rates and mechanisms of the oxidation of isobutane over H 3 [PMo 12 O 40 ], CuH 4 [PMo 12 O 40 ] 2 , Cu 2 H 2 [PMo 12 O 40 ] 2 , Cu 2.5 H[PMo 12 O 40 ] 2 , and Cu 3 [PMo 12 O 40 ] 2 . Observed oxidation products over all catalysts are methacrolein, 3-methyl-2-oxetanone, acetic acid, carbon dioxide and water. The most selective catalyst for methacrolein formation at low temperatures (<496 8C) is Cu 2.5 H[PMo 12 O 40 ] 2 , where both Cu(II) reduction and acid sites play a role. The least active catalyst at low temperatures is phosphomolybdic acid followed by Cu 3 [PMo 12 O 40 ] 2 . This activity is reversed at higher temperatures. The 3-methyl-2-oxetanone is a unique product and is likely to be the precursor to methacrylic acid. Acetic acid is also probably a precursor to complete oxidation. Catalyst deactivation or restructuring is significant only over H 3 [PMo 12 O 40 ].