Selective synthesis of MeCHO by C2H4–(O2+NO) cell system

Abstract

Fig. 2 Effects of some oxidants of the C 2 H 4 -oxidant cell with graphite/ PTFE cathode on the Wacker oxidation. C 2 H 4 (39 kPa), H 2 O (13 kPa), anode ¡ aq. H 3 PO 4 in silica wool ¡ cathode, oxidants. Oxidants: NO 2 (5 kPa), NO (20 kPa), O 2 (50 kPa), NO (50 kPa) + O 2 (51 kPa), and NO (6 kPa) + O 2 (51 kPa). T = 353 K.

Electrochemical Studies of the Alkene-NO[sub x] Fuel Cell for Organic Synthesis

“…The reactor and the principle of the cell system were already described. [1][2][3]6,7 The gases at the cathode and anode are separated with a silica wool disk ͑thickness, 1 mm͒ holding aqueous H 3 PO 4 ͑85 wt %͒ as an electrolyte ͑Fig. 2a͒.…”

“…Selective partial oxidation of alkenes in the gas phase using alkene-(O 2 ϩ NO) cell systems has been reported. [1][2][3] The cell consisted of ͓alkene͉Pd anode͉H 3 PO 4 ͉cathode͉O 2 ϩ NO]. The advantages of the gas-cell system have been described to compare with the current Wacker process in aqueous HCl with PdCl 2 and CuCl 2 as catalysts.…”

“…The advantages of the gas-cell system have been described to compare with the current Wacker process in aqueous HCl with PdCl 2 and CuCl 2 as catalysts. [1][2][3][4][5] For example, ͑i͒ products can be easily separated from the catalytic system, (ii) the cell system requires no chlorides, therefore, by-products containing chlorine are not formed, (iii) the danger of explosion is reduced because alkenes and oxidants are separated, and (iv) the cell can cogenerate electricity and chemicals. [1][2][3] When C 2 H 4 was supplied to the gas-cell system, C 2 H 4 was oxidized with H 2 O to MeCHO over the Pd anode.…”

“…[1][2][3][4][5] For example, ͑i͒ products can be easily separated from the catalytic system, (ii) the cell system requires no chlorides, therefore, by-products containing chlorine are not formed, (iii) the danger of explosion is reduced because alkenes and oxidants are separated, and (iv) the cell can cogenerate electricity and chemicals. [1][2][3] When C 2 H 4 was supplied to the gas-cell system, C 2 H 4 was oxidized with H 2 O to MeCHO over the Pd anode. Protons and electrons were, respectively, conduced through a lead wire and electrolyte to the cathode, and oxidized with oxidant ͓O 2 ϩ NO͔.…”

“…[4][5][6][7][8][9] These facts led us to speculate that the oxidation state of the Pd anode may change from Pd 0 to Pd 2ϩ by the addition of NO into the O 2 stream at the cathode. We have already proposed a primitive mechanistic model by which a strong oxidant such as NO 2 , produced from O 2 and NO at the cathode, accelerated the oxidation of Pd 0 to Pd 2ϩ that oxidized C 2 H 4 to MeCHO on the anode through the Wacker oxidation mechanism, [1][2][3] but no direct evidence for the redox properties of Pd on the anode and NO x on the cathode were obtained. Therefore, we have investigated the redox properties of Pd and C 2 H 4 , and the mixture of O 2 and NO by cyclic voltammetry in this work.…”