Patent ID: 7569614
Filing Date: 2009-08-04
Classification: B01J,B82Y,C01F,C01P,Y02P,Y10S

Abstract:
1. A process for producing a stable acidic aqueous alumina sol containing columnar secondary particles having a length of 50 to 400 nm which are formed by face-to-face coagulation of rectangular plate-like primary particles having a length of one side of 10 to 40 nm and a thickness of 2.5 to 10 nm when observed through an electron microscope, the process comprising the steps (A), (B) and (C) of: (A) adding liquid or gaseous carbon dioxide to an aqueous alkali aluminate solution at a solution temperature of 5 to 35° C. to produce a reaction mixture having a pH of 10.5 to 11.2; (B) subjecting the reaction mixture obtained in the step (A) to a hydrothermal treatment at a temperature of 110 to 250° C. to produce an aqueous suspension containing an alumina hydrate having a boehmite structure; and (C) desalting the aqueous suspension obtained in the step (B) by adding water and an acid by ultrafiltration to form an acidic aqueous alumina sol having a pH of 3 to 7.