Joe Gautney

The formation of isocyanate on preoxidized Ru/Al2O3

Abstract The reaction of CO and NH 3 over preoxidized Ru/Al 2 O 3 has been investigated using infrared spectroscopy. An isocyanate (NCO) surface intermediate providing an infrared band in the range 2246–2256 cm −1 was detected. The NCO species formed on Ru and then migrated to the A1 2 O 3 support. The species was detected in the temperature ranges 298–340 K and 383–500 K, but disappeared between 340 and 383 K, indicating that two different mechanisms of formation were operable. Studies of the decomposition of formamide over preoxidized Ru/Al 2 O 3 indicated that the low temperature formation of NCO in the CO/NH 3 reaction probably involved an amide intermediate.

Mode of migration of isocyanate from palladium to silica

The reaction of CO and NH3 over preoxidized PdSiO2 has been studied using infrared spectroscopy to identify surface species. An isocyanate (NCO) surface intermediate on Pd providing an infrared band at 2168 cm−1 was detected after heating to 500 K and subsequent cooling to ambient temperature. No migration of NCO from Pd to the SiO2 support was observed. However, the decomposition of formamide over preoxidized PdSiO2 at ambient temperature did produce an NCO species which migrated to the SiO2 via the formation of HNCO gas. It was concluded that an amide species is not an intermediate in the CONH3 reaction over preoxidized PdSiO2, although it may be for the reaction over preoxidized PdAl2O3.

The nature of the surface site for isocyanate produced in the reaction of ammonia and carbon monoxide over supported catalysts

Abstract The reaction of CO and NH 3 was performed over M/X (M=Rh, Ru, Pd; X=Al 2 O 3 , SiO 2 , TiO 2 ) films. Infrared spectroscopy was used to monitor the formation of surface intermediates. Isocyanate (NCO) was detected for all of the metals when the support was Al 2 O 3 or SiO 2 , but not for TiO 2 . The NCO resided on the Al 2 O 3 support for all M/Al 2 O 3 catalysts, but on the metal when the support was SiO 2 . It was concluded that the formation and location of the NCO was dependent upon the extent of NH 4 + formation on the various supports.

Melamine: A Regenerative S02 Absorbent

A new regenerative SO2 abatement process using melamine has been developed. In this process a gas stream containing SO2 is contacted with an aqueous slurry of melamine to produce solid melamine sulfite. The solids are separated and thermally decomposed at 100°–200°C. Statistically designed laboratory scrubbing tests using simulated stack gas were performed at 50°C to determine the relative effects of slurry concentration, SO2 concentration, CO2, O2, NO, fly ash, antioxidant, and prescrubber on the melamine scrubbing process. Average SO2 removal for these tests with 2000 and 4000 ppm SO2 was 95.5%, and each mole of melamine absorbed 0.5 mole of SO2. Carbon dioxide (12%) and NO (600 ppm) did not reduce the scrubbing efficiency or capacity of the melamine, and the addition of an antioxidant (0 .1% paraphenylenediamine) effectively minimized oxidation. The melamine scrubbing process looks promising and offers the advantages of high SO2 removal and low energy requirement regeneration.

Melamine a regenerative sulfur di oxide absorbent

A new regenerative SO2 abatement process using melamine has been developed. In this process a gas stream containing SO2 is contacted with an aqueous slurry of melamine to produce solid melamine sulfite. The solids are separated and thermally decomposed at 100°–200°C. Statistically designed laboratory scrubbing tests using simulated stack gas were performed at 50°C to determine the relative effects of slurry concentration, SO2 concentration, CO2, O2, NO, fly ash, antioxidant, and prescrubber on the melamine scrubbing process. Average SO2 removal for these tests with 2000 and 4000 ppm SO2 was 95.5%, and each mole of melamine absorbed 0.5 mole of SO2. Carbon dioxide (12%) and NO (600 ppm) did not reduce the scrubbing efficiency or capacity of the melamine, and the addition of an antioxidant (0 .1% paraphenylenediamine) effectively minimized oxidation. The melamine scrubbing process looks promising and offers the advantages of high SO2 removal and low energy requirement regeneration.