TABLE 2.

Elementary steps for the reactions.

Steps	Operating conditions a	Elementary steps for reaction mechanisms	k a (s−1)	W (kWh/kg)
1st step (Glycerol dehydration)	[Gly] = 3.0 mol/L	C3H8O3 + H+ → (C3H9O3)+ → C3H6O2 + H+ + H2O	$\left({\mathrm{k}}_{\mathrm{C}3\mathrm{H}6\mathrm{O}2}\right)$	—
	T = 353 K		k1 = 0.0436 × 10–4
2nd step (Electrocatalytic reduction of glycerol) with H2 formation		C3H8O3 + e− → (C3H9O3)•–	$\left({\mathrm{k}}_{{\left(\mathrm{C}3\mathrm{H}9\mathrm{O}3\right)}^{•-}}\right)$	—
		(C3H9O3)•- + H• + H+ + e− → C3H6O2 + H2O + H2	$\left({\mathrm{k}}_{\mathrm{C}3\mathrm{H}6\mathrm{O}2}\right)$	—
		H+ + e− → ACC-Hads	$\left({\mathrm{k}}_{\mathrm{H}•}\right)$ Volmer	—
		ACC-Hads + H+ + e− → H2 + ACC	$\left({\mathrm{k}}_{\mathrm{H}2}\right)$ Heyrovsky	—
		ACC-Hads + ACC-Hads → H2 + 2ACC	$\left({\mathrm{k}}_{\mathrm{H}2}\right)$ Tafel	—
3rd step (Electrocatalytic hydrogenation of acetol)	[ACTL] = 3.0 mol/L	C3H6O2 + 2H+ + 2e− → C3H8O2	$\left({\mathrm{k}}_{\mathrm{C}3\mathrm{H}8\mathrm{O}2}\right)$	10.17
	T = 353 K
	j = 0.28 A/cm2		k2 = 0.4892 × 10–4
	E = 25.7 V
4th step (Electrocatalytic reduction and hydrogenation of glycerol)		C3H8O3 + e− → (C3H9O3)•–	$\left({\mathrm{k}}_{{\left(\mathrm{C}3\mathrm{H}9\mathrm{O}3\right)}^{•-}}\right)$	—
		(C3H9O3)•- → C2H5O2• + CH2O−	$\left({\mathrm{k}}_{\mathrm{C}2\mathrm{H}5\mathrm{O}2• }\right)$	—
		C2H5O2• + H+ + e− → C2H6O2	$\left({\mathrm{k}}_{\mathrm{C}2\mathrm{H}6\mathrm{O}2}\right)$	—
		CH2O− + H+ → CH3O	$\left({\mathrm{k}}_{\mathrm{CH}3\mathrm{O}}\right)$	—
5th step (Dehydration of ethylene glycol to diethylene glycol)	[EG] = 3.0 mol/L	C2H6O2 + H+ → (C2H7O2)+ + C2H6O2 → C4H10O3 + H+ + H2O	$\left({\mathrm{k}}_{\mathrm{C}4\mathrm{H}10\mathrm{O}3}\right)$	—
	T = 353 K		k3 = 0.0867 × 10–4
6th step (Etherification of glycerol with methanol)		C3H8O3 + CH3OH → C4H10O3 + H2O	$\left({\mathrm{k}}_{\mathrm{C}4\mathrm{H}10\mathrm{O}3}\right)$	—
Overall (Glycerol electro-reduction reaction)	[Gly] = 3.0 mol/L	C3H8O3 + H+ +e− → C3H6O2 + C3H8O2 + C4H10O3	k = 0.3339 × 10–4	5.24
	T = 353 K
	j = 0.21 A/cm2
	E = 21.9 V

^aAt the optimal conditions for targeted compound formation; ACC, active site of 80ACC electrode; k, kinetics rate constant; W, electrical energy or energy consumption.