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

Table 1

Effect of additives for the oxidation of benzyl alcohol to benzaldehyde at 70°C^a.

Entry	Catalyst	Amount^b (mol%)	Conv. (%)	Sel.^c (%)
1	FeSO4/NaBF4	2.5%/1%	66.6	94.5 (89 : 11)
2		2.5%/10%	71.0	94.3 (88 : 12)
3	FeSO4/NaH2PO4	2.5%/1%	74.7	96.0 (87 : 13)
4		2.5%/5%	2.0	96.5 (87 : 13)
5		2.5%/10%	1.6	93.3 (93 : 7)
6	FeSO4/KH2PO4	2.5%/1%	64.1	95.9 (90 : 10)
7		2.5%/2.5%	4.4	95.1 (92 : 8)
8		2.5%/5%	1.9	89.2 (88 : 12)
9	FeSO4/KHP^d	2.5%/1%	51.3	94.7 (82 : 18)
10		2.5%/2.5%	32.8	86.7 (92 : 8)

a20 mmol of benzyl alcohol (2.16 g), 2.2 equiv. of H₂O₂ (44 mmol, 4.5 mL, 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. ^dKHP: potassium hydrogen phthalate.