Improvement the Activity and Selectivity of Fenton System in the Oxidation of Alcohols

Table 3

Oxidation of benzyl alcohol with different catalyst systems at 25°C^a.

Entry	Catalyst	Amount^b (mol%)	Conv. (%)	Sel.^c (%)
1	FeSO4/NHPI	2.5%/2.5%	36.7	99.1 (94 : 6)
2		2.5%/1.25%	36.0	98.2 (92 : 8)
3		2.5%/5.0%	31.8	95.9 (90 : 10)
4	FeSO4/TEMPO	2.5%/2.5%	20.5	98.9 (96 : 4)
5	FeSO4/4-OH-TEMPO	2.5%/2.5%	13.9	99.6 (99 : 1)
6	Fe2(SO4)3/NHPI	2.5%/2.5%	32.1	95.2 (87 : 13)
7	Fe(NO3)3/NHPI	2.5%/2.5%	59.9	94.2 (82 : 18)
8	FeCl3/NHPI	2.5%/2.5%	43.3	87.6 (84 : 16)

a20 mmol of benzyl alcohol, 2.2 equiv. of H₂O₂ (30 wt% in water), reaction time: 0.5 h. H₂O₂ was added with a syringe pump by 0.2 mL/min speed. ^bAmount of catalyst. ^cTotal selectivity to benzaldehyde and benzoic acid. Value in parentheses means the ratio of benzaldehyde/benzoic acid.