Partial oxidation of alcohols to produce hydrogen and chemicals in millisecond-contact time reactors

We compare the autothermal partial oxidation of 1-propanol and 2-propanol with methanol and ethanol on Rh with several additives in short-contact time reactors. All alcohols could produce H2 at 70-90% selectivity, and Rh-Ce was superior to Rh in producing H2. Methanol produced high conversion and high selectivity to H2 even at high C/O where temperatures fell to <600 °C. 2-Propanol gave lower conversions and less H2 and CO than the other alcohols, but produced the most chemicals. Above C/O = 1.5, ∼70% of 2-propanol was converted into acetone or propylene. Up to 20% propylene was formed at C/O = 1.5. In contrast, 1-propanol gave <8% propylene and <15% propanal at any C/O and produced more ethylene than propylene. Much more oxygenates and olefins were formed on Rh than on Rh-Ce. These results show that different alcohols have very different selectivity in catalytic partial oxidation at short contact times even at high temperatures. Rapid adsorption of alcohols as alkoxy species leads to complete dissociation to H2 and CO. Our results suggest that acetone and olefins likely were produced primarily by homogeneous reactions after all O2 had been consumed in the catalyst. Although alkanes do not form significant oxygenates by partial oxidation at short contact times, alcohols can be made to produce predominantly oxygenates through suitable adjustments of C/O and catalyst.