Methods of Preparing a Catalyst with Low HRVOC Emissions

A method of preparing a hydrolyzed pre-catalyst comprising:

• a) drying a silica support by heating the silica support to a temperature in a range of from about 150° C. to about 250° C. and maintaining the temperature of the silica support in the range of from about 150° C. to about 250° C. for a time period of from about 1 hour to about 24 hours to form a dried support;
• b) contacting the dried support and a titanium(IV) alkoxide to form a titanated support;
• c) heating the titanated support to a temperature in a range of from about 50° C. to about 200° C. and maintaining the temperature in the range of from about 50° C. to about 200° C. while contacting the titanated support and an alkaline material for a time period of from about 2 hours to about 48 hours;
• d) ceasing contacting of the titanated support and the alkaline material to provide a hydrolyzed support having a temperature in a range of from about 50° C. to about 200° C.;
• and
• e) maintaining the temperature of the hydrolyzed support in the range of from about 50° C. to about 200° C. for a time period of from about 30 minutes to about 6 hours to form the hydrolyzed pre-catalyst.

A method of preparing a catalyst comprising:

• a) drying a silica support by heating the silica support to a temperature in a range of from about 150° C. to about 250° C. and maintaining the temperature of the silica support in the range of from about 150° C. to about 250° C. for a time period of from about 1 hour to about 24 hours to form a dried support;
• b) contacting the dried support and a titanium(IV) alkoxide to form a titanated support;
• c) drying the titanated support by heating the titanated support to a temperature in a range of from about 50° C. to about 200° C. and maintaining the temperature of the titanated support in the range of from about 50° C. to about 200° C. for a time period of from about 30 minutes to about 6 hours to form a dried titanated support;
• d) contacting the dried titanated support and an aqueous alkaline solution comprising from about 3 wt. % to about 20 wt. % of a nitrogen-containing compound for a time period of from about 10 minutes to about 6 hours to form a mixture comprising a hydrolyzed titanated support wherein a weight ratio of the amount of aqueous alkaline solution to the amount of titanium(IV) alkoxide in the dried titanated support is from about 30:1 to about 3:1;
• e) removing the hydrolyzed titanated support from the mixture comprising the hydrolyzed titanated support and drying the hydrolyzed titanated support by heating the hydrolyzed titanated support to a temperature in a range of from about 50° C. to about 200° C. and maintaining the temperature of the hydrolyzed titanated support in the range of from about 50° C. to about 200° C. for a time period of from about 30 minutes to about 6 hours to form a hydrolyzed pre-catalyst;
• f) contacting, to form a pre-catalyst, a chromium-containing compound and at least one material selected from the group consisting of the silica support, the dried support, the titanated support, the dried titanated support, the mixture comprising the hydrolyzed titanated support, and the hydrolyzed pre-catalyst;
• and
• g) calcining the pre-catalyst by heating the pre-catalyst to a temperature in a range of from about 400° C. to about 1000° C. and maintaining the temperature of the pre-catalyst in the range of from about 400° C. to about 1000° C. for a time period of from about 1 minute to about 24 hours to form the catalyst.