Chemistry of inorganic compounds – Oxygen or compound thereof – Metal containing
Reexamination Certificate
1997-07-03
2001-03-27
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Oxygen or compound thereof
Metal containing
Reexamination Certificate
active
06207131
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing titanium dioxide by reacting titanium tetrachloride vapors with oxygen and to an improved reactor for use in such a system. The process and reactor of the present invention provides the ability to control properties, such as particle size, of the titanium dioxide product.
It is well-known that titanium tetrachloride reacts with oxygen in the vapor phase to form titanium dioxide and that this reaction is initiated by heating the reactants to a suitable temperature. However hot titanium tetrachloride is highly corrosive and therefore many useful materials of construction for heat exchangers used to heat titanium tetrachloride are rapidly corroded. In practice this generally imposes an upper limit of about 400° C. (752° F.) on the temperature to which titanium tetrachloride can be heated by conventional heat exchangers.
A suitable temperature for the reactants (oxygen and titanium tetrachloride) is about 950° C. (1742° F.) and, in order to achieve this temperature in known processes, the oxygen feed must be heated sufficiently to compensate for the above-mentioned relatively low titanium tetrachloride temperature. Frequently, oxygen is heated directly or heated by an electrical discharge to temperatures of about 1427-1871° C. (2600-3400° F.) as oxygen is introduced into the oxidation reactor in combination with an auxiliary fuel. The use of these methods introduce unwanted impurities such as, for example, carbonaceous residues from the fuel or metallic impurities from the electrodes used for the electrical discharge.
SUMMARY OF THE INVENTION
According to the invention a process for the production of titanium dioxide comprises reacting titanium tetrachloride with oxygen at a pressure above atmospheric pressure and at a reaction temperature of at least about 700° C. (1292° F.) in an oxidation reactor, the oxygen being introduced into the reactor at a first inlet point and at least one further inlet point. Optionally, the titanium tetrachloride may be introduced as a mixture with aluminum chloride and heated to a temperature of at least about 350° C. (662° F.), the aluminum chloride being formed by reaction of aluminum and chlorine and the heat generated by this reaction being used to heat the titanium tetrachloride. The aluminum chloride may also be added by dissolving the aluminum chloride in the titanium tetrachloride.
According to the present invention, a reactor for producing titanium dioxide by reacting titanium tetrachloride vapors with oxygen comprises a means for forming a first reaction zone and an oxidizing gas introduction assembly for receiving oxygen at a predetermined temperature level and passing oxygen into the first reaction zone. The oxidizing gas introduction assembly comprises a conduit having an upstream and a downstream end and an opening extending therethrough intersecting the upstream and the downstream ends where oxygen is passable through the opening in the conduit for passing into the first reaction zone. The reactor further comprises a first titanium tetrachloride introduction assembly for receiving titanium tetrachloride vapors at a first predetermined temperature and passing titanium tetrachloride vapors into the first reaciton zone for reacting with oxygen to produce a mixture including titanium dioxide. Still further, the reactor comprises a means for passing the titanium tetrachloride vapor at the predetermined temperature into the first reaction zone and an including means for forming a second reaction zone spaced a distance downstream from the first reaction zone. The reactor also comprises a second oxidizing gas introduction assembly for receiving oxygen at a second predetermined temperature and passing the oxygen at the second temperature into the second reaction zone for reaction with titanium tetrachloride in the mixture from the first reaction zone to produce a mixture including titanium dioxide, the reaction of oxygen at the second temperature with the mixture passed from the first reaction zone reducing the volume of oxygen at the first temperature level required for a given volume of titanium dioxide produced and a means for passing the oxygen at the second temperature into the second reaction zone. Still further, the reactor comprises an aluminum chloride generator for heating the titanium tetrachloride vapors to a first predetermined temperature and a flowline for passing titanium tetrachloride from the aluminum chloride generator to the titanium tetrachloride introduction assembly.
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Magyar John C.
Morris Alan J.
Wootten Glenn D.
Yuill William A.
Bos Steven
Dougherty, Jr. C. Clark
Kerr-McGee Chemical LLC
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