Table 2. Elemental Surface and Bulk Concentrations of CrMnO_x Catalysts.

	surface concentrationa (atm. %)
catalyst	Mn	Cr	O	surface Cr ratio	bulk Cr ratio	carbon concentrationc (wt %)
300-1	17.64	13.95	68.41	0.44	0.40b (0.41)	0.37 ± 0.07
300-5	18.12	13.57	68.31	0.43	0.40 (0.40)	0.24 ± 0.05
300-10	17.94	13.50	67.56	0.45	0.40 (0.40)	0.25 ± 0.05
400-1	18.02	13.76	68.22	0.43	0.40 (0.42)	0.24 ± 0.05
400-10	19.69	12.65	67.66	0.39	0.39 (0.39)	0.27 ± 0.05

^aCalculated from Cr 2p, Mn 2p, and O 1s signals from XPS survey scans.

^bDetermined by ICP-AES; brackets denote values determined via EDX.

^cAveraged from three replicants, instrumental detection limit is 0.20 wt %.