Reactions of Various Metal Oxides with Hydrogen Chloride and the Reverse Reaction

Abstract

The chloride-formation reaction of metal oxides with HCl gas and the reverse reaction were studied to obtain the basic informations about the corrosion of materials, recovery of waste catalysts, minerals with volatilization of chlorides, and the catalytic mechanism of Deacon reaction or oxychlorination. The experiments were carried out by using a thermanobalance, , X-ray diffraction, and gas analysis under an atmospheric pressure and at 25-500°C. Inlet gases were 0-1.5% HCl-O-21% O^2-0 or 4% H₂0-N2 and etc., and the total gas flow rate was 500 N. ansimin for 80 mg of metal oxides and etc. (avarage diameter 0.16 mm). The metal oxides were mainly prepared by the precipitation reaction of metal salts with NaOH at 70 or 100°C
The following results were obtained:
1) The chloride-formation reactions are brought about by M0+2 HCl, -MCl2+H₂0 for MO (MgO, CaO, NiO, CuO, ZnO, PbO, HgO, etc. and by Mx0y +2 y MCl2+ y H₂0+ (y x) Cl2(Eq. A) for Mx0, , , (V205, Mn$0, Mn2O^2-, Co3O^2-, Pb3O^2-, PbO^2-, etc. ). Also, for Cu0 above ca.300°C, the reaction of CuO + 2 HCl CuCl+1-120+ (1/2) Cl2 occurs and A12O^2-, SiO^2-, Fe208, FesO^2-, ZrO^2-, CeO₂, WO^2- and etc. do not react under the present conditions.
2) The chloride formation reactions (Eq. A) are the combination of MsOy+ 2 x HCl x MCl2+ x H₂0+ (y) /2jO^2- and MCl2+ (y/2 x)°2---- (1/x) V1, 0, -1- Cl2 (Eq. B), which is the decomposition-oxidation reaction of metal chloride (MCI2) with O^2-.
3) The decomposition-oxidation reactions of chlorides in water vapor are given by MCl2+ (Y/x)120-- (1/x)Mx0v+ 2 HCl+ (Y/x) -11112 at lower temperatures and by MCl2+H₂0--M0 +2 HCl at higher temperatures. Also, in the mixtures of O^2- and water vapor, it is shown by MCl2+ (y-x) /2 X1O^2- + H₂0(1/X) MrOy + 2 HCl.
4) The catalytic mechanism of Deacon reaction (4 HCl+O^2-2 Cl2+2 H₂O) was elucidated in terms of the combination of Eqs. A and B.