Process for in-situ formation of chlorides in the preparation of titanium dioxide

1. A process for producing titanium dioxide, comprising:

a) reacting an ahoy comprising a metal selected from the group consisting of aluminum, titanium and mixtures thereof, wherein either aluminum or titanium is a major component of the alloy, and an element selected from the group consisting of Li, Be, B, Na, Mg, Al, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Ph, and Bi, with chlorine gas, in the presence of titanium tetrachloride, to form chlorides of aluminum, titanium or mixtures thereof and a chlorides of the element selected from the group consisting of Li, Be, B, Na, Mg, Al, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, and Bi, at or above the boiling point of the chloride of the major component of the alloy; with the proviso that the element does not comprise Ti when the metal is Ti and does not comprise Al when the metal is Al;

(b) adding titanium tetrachloride to the chlorides formed in step (a);

(c) oxidizing the chlorides formed in step (a), and titanium tetrachloride added in step (b); and

(d) forming titanium dioxide.

2. The process of claim 1 wherein the element is selected from the group consisting of Li, B, Na, Mg, Al, P, S, K, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Ge, Se, Rh, Zr, Nb, Mo, Ag, in, Sn, Sb, Cs, Ba, La, Ce, Ta, W, Pt and Au.

3. The process of claim 2 wherein the element is selected from the group consisting of B, Mg, Al, P, K, Ti, Zn, Ge, Pb, Zr, Nb, Cs, and W.

4. The process of claim 1 wherein alloy comprises about 0.1% to about 40% of the element, based on the total weight of the alloy.

5. The process of claim 4 wherein alloy comprises about 0.5% to about 20% of the element, based on the total weight of the alloy.

6. The process of claim 5 wherein alloy comprises about 1.0% to about 15% of the element, based on the total weight of the alloy.

7. The process of claim 1 wherein the reaction in step (a) occurs in a reactor selected from the group consisting of a fluidized bed reactor, spouting bed reactor, packed had reactor, and a plug flow reactor.

8. The process of claim 7 wherein the reactor comprises materials selected from the group consisting of silica sand, glass beads, ceramic beads, and TiO 2 particles.

9. The process of claim 7 wherein the reaction in step (a) occurs in the presence of nucleating salts.

10. The process of claim 9 wherein the nucleating salts are selected from the group consisting of potassium chloride, rubidium chloride, and cesium chloride.

11. The process of claim 1 wherein the amount of chlorine is about 0.4% to about 20% by weight, based on the total amount of all reactants in steps (A and (b).

12. The process of claim 11 wherein the amount of chlorine is about 2% to about 5% by weight, based on the total amount of all reactants in steps (a) and (b).

13. The process of claim 1 wherein the amount of titanium tetrachloride is about 75% to about 99.5% by weight, based on the total amount of all reactants in steps (a) and (b).

14. The process of claim 13 wherein the amount of titanium tetrachloride is about 93% to about 98% by weight, based on the total amount of all reactants in steps (a) and (b).

15. The process of claim 1 wherein the titanium tetrachloride is present in a major amount in step (c).