Method for making ultrapure sulfuric acid

A method for producing ultrapure sulfuric acid comprising the steps of:

• providing a sulfuric acid material containing more than about 10 particles of 1 micron and greater size particles per cubic centimeter;
• processing said sulfuric acid material to reduce the particle count to 5 particles or less per cubic centimeter of 1 micron and greater size particles;
• said processing including a distillation operation in which a first vapor component and a first liquid component are formed;
• subjecting said first liquid component to a separate distillation operation to form a second vapor component;
• and,
• condensing said second vapor component to form said ultrapure sulfuric acid.

A method for producing ultrapure sulfuric acid comprising the steps of:

• providing sulfuric acid material containing more than about 10 particles of 1 micron and greater size particles per cubic centimeter;
• processing said sulfuric acid material by distillation to reduce the particle count to 5 particles or less per cubic centimeter of 1 micron and greater size particles;
• wherein said distillation comprises:
• introducing said sulfuric acid containing more than about 10 particles of 1 micron and greater size particles per cubic centimeter into a distillation chamber having walls;
• heating said sulfuric acid contained within said distillation chamber to cause distillation thereof;
• and,
• effecting a smooth convective upward flow of said distilling sulfuric acid liquid and vapor proximate to said walls;
• and,
• effecting a smooth convective downward flow of distilling sulfuric acid liquid substantially centrally of said distillation chamber.

A method for the removal of soluble impurities and insoluble and non-volatile particles of 0.5 micron and greater in size, from sulfuric acid comprising:

• introducing sulfuric acid into a distillation column having walls and a lengthwise central region and including an upper portion for vapor and a lower portion for liquid to be distilled, said lower portion of said distillation column having a plurality of nucleation sites proximate to said walls;
• heating at least a portion of said column containing said liquid sufficient to cause distillation of said liquid;
• and,
• to encourage smooth boiling and provide a smooth convective upward flow of distilling sulfuric acid liquid and vapor along the walls of said distillation column with the liquid sulfuric acid temperatures occurring nearest the walls being higher than the liquid temperatures within the lengthwise central region of said column so that there is provided a smooth convective downward flow of distilling sulfuric acid in the central region of said column with separation of said sulfuric acid material into a substantially particle free vapor and a particle enriched liquid.

A method for reprocessing sulfuric acid material to produce ultrapure sulfuric acid having a particle count of 5 or less per cubic centimeter of 1 micron and greater sized particles and 10 or less per cubic centimeter of 0.5 micron and greater sized particles comprising:

• collecting said sulfuric acid material containing at least 10 particles per cubic centimeter of particulate material;
• introducing said sulfuric acid material into a distillation column having walls and a lengthwise central region and including an upper portion for vapor and a lower portion for liquid to be distilled, said lower portion of said distillation column having a plurality of nucleation sites proximate to said walls;
• heating at least a portion of said column containing said liquid sufficient to cause distillation of said liquid and,
• to encourage smooth boiling and provide a smooth convective upward flow of liquid and vapor along the walls of said distillation column with the liquid temperatures occurring nearest the walls being higher than the liquid temperatures within the lengthwise central region of said column so that there is provided a smooth convective downward flow in the central region of said column, and a separation of distilling liquid into a substantially particle free vapor and a particle enriched liquid.