A method for the preparation of titanium dioxide, the method comprising the steps of subjecting a titanium containing leach residue to a concentrated sulfuric acid digest step; and in turn subjecting that residue to a leach in dilute sulfuric acid, whereby a black liquor is obtained and from which titanium dioxide is in turn obtained.

In an amorphous complex metal oxide and a method for producing the same of the present disclosure, the amorphous complex metal oxide is a three-components metal oxide containing titanium (Ti), cerium (Ce), and zirconium (Zr), wherein the amorphous complex metal oxide is amorphous.

A process for producing a particulate TiO.sub.2 includes supplementing metatitanic acid with an alkali compound in a quantity of 1200 ppm to 2400 ppm of alkali, with a phosphorus compound in a quantity of 0.1 wt.-% to 0.3 wt.-% by weight of P, expressed as phosphorus, and with an aluminum compound in a quantity of 1 ppm to 1000 ppm of Al, expressed as Al, to obtain a mixture. The quantity of the alkali compound, of the phosphorus compound, and of the aluminum compound are with respect to the TiO.sub.2 content. The mixture is calcined at a constant temperature of 940° C. to 1020° C. until a numerical fraction X.sub.50 of TiO.sub.2 has a primary crystallite size of at least 200 nm, to obtain a calcined mixture. The calcined mixture is cooled to obtain a cooled calcined mixture. The cooled calcined mixture is grinded to obtain the particulate TiO.sub.2.

A process for producing a particulate TiO.sub.2 includes supplementing metatitanic acid with an alkali compound in a quantity of 1200 ppm to 2400 ppm of alkali, with a phosphorus compound in a quantity of 0.1 wt.-% to 0.3 wt.-% by weight of P, expressed as phosphorus, and with an aluminum compound in a quantity of 1 ppm to 1000 ppm of Al, expressed as Al, to obtain a mixture. The quantity of the alkali compound, of the phosphorus compound, and of the aluminum compound are with respect to the TiO.sub.2 content. The mixture is calcined at a constant temperature of 940° C. to 1020° C. until a numerical fraction X.sub.50 of TiO.sub.2 has a primary crystallite size of at least 200 nm, to obtain a calcined mixture. The calcined mixture is cooled to obtain a cooled calcined mixture. The cooled calcined mixture is grinded to obtain the particulate TiO.sub.2.

This disclosure describes multi-fluid kits for three-dimensional printing, three-dimensional printing kits, and systems for three-dimensional printing. In one example, a multi-fluid kit for three-dimensional printing can include a fusing agent and a detailing agent. The fusing agent can include water and metal oxide nanoparticles dispersed therein. The metal oxide nanoparticles can be selected from titanium dioxide, zinc oxide, cerium oxide, indium tin oxide, or a combination thereof. The metal oxide nanoparticles can have an average particle size from about 2 nm to about 500 nm. The detailing agent can include a detailing compound.

This disclosure describes multi-fluid kits for three-dimensional printing, three-dimensional printing kits, and systems for three-dimensional printing. In one example, a multi-fluid kit for three-dimensional printing can include a fusing agent and a detailing agent. The fusing agent can include water and metal oxide nanoparticles dispersed therein. The metal oxide nanoparticles can be selected from titanium dioxide, zinc oxide, cerium oxide, indium tin oxide, or a combination thereof. The metal oxide nanoparticles can have an average particle size from about 2 nm to about 500 nm. The detailing agent can include a detailing compound.

Provided is a preparing method of an amide directly from a tertiary amine by using a reduced titanium dioxide (Blue TiO.sub.2), which is formed by mixing a titanium dioxide having an anatase phase and a rutile phase with a reducing agent and selectively reducing any one of the anatase phase and the rutile phase, as a photocatalyst.

Provided is a preparing method of an amide directly from a tertiary amine by using a reduced titanium dioxide (Blue TiO.sub.2), which is formed by mixing a titanium dioxide having an anatase phase and a rutile phase with a reducing agent and selectively reducing any one of the anatase phase and the rutile phase, as a photocatalyst.

Methods of forming non-metal doped metal oxide nanoparticles using a flame spray pyrolysis process are described. The non-metal doped metal oxide nanoparticles exhibit high photocatalytic activity. Specific non-metal doped metal oxides nanoparticles which can be formed by the described processes include nitrogen-doped titanium dioxide and sulfur-doped titanium dioxide.

Methods of forming non-metal doped metal oxide nanoparticles using a flame spray pyrolysis process are described. The non-metal doped metal oxide nanoparticles exhibit high photocatalytic activity. Specific non-metal doped metal oxides nanoparticles which can be formed by the described processes include nitrogen-doped titanium dioxide and sulfur-doped titanium dioxide.