ABSORPTIVE LOW BULK DENSITY SODIUM CARBONATE MONOHYDRATE AND SODIUM SESQUICARBONATE PRODUCTS

摘要

1469886 Treating sodium sesquicarbonate or sodium carbonate monohydrate ALLIED CHEMICAL CORP 1 May 1974 [2 May 1973(2)] 19183/74 Heading C1A Particles comprising sodium sesquicarbonate or sodium carbonate monohydrate are treated to produce particles of reduced bulk density in the form of randomly oriented microcrystalline needles comprising Wegscheider's Salt by heating the particles in a reaction zone at 70- 105‹ C. (70-100‹ C. for the carbonate monohydrate) in contact with a gas mixture containing 15-85% CO 2 , 15-85% H 2 O vapour (15- 70% for the carbonate monohydrate) and 0- 45% inert gas until the particles contain at least 10% Wegscheider's salt and continuing the reaction at 70-105‹ C. with net production of water until the particles contain at least 20% by weight of Wegscheider's salt and less than 12% of water. The pressure within the reaction zone is preferably between 12 and 25 lb./in.2 absolute, the preferred conditions for the treatment of the carbonate monohydrate particles is a temperature of 85-95‹ C. and a mixture containing 40-65% vol. CO 2 and 20-40% vol. H 2 O vapour and for the sesquicarbonate is a temperature of 90-100‹ C. and a gas mixture containing 45-70% vol. CO 2 and 25-40% vol. H 2 O vapour. The reaction is preferably continued until the particles contain at least 50, preferably at least 85% by weight of Wegscheider's salt. A portion of the water produced in the reaction zone is preferably condensed by cooling and the resulting gas mixture may be recycled to the reaction zone. The process provides a composition in the form of granular particles of sodium carbonate monohydrate having therein randomly oriented micro-needles of Wegscheider's salt, the composition containing at least 20% by weight of the salt, the remainder being sodium carbonate monohydrate, sodium bicarbonate and/or sodium sesquicarbonate and having a bulk density of 12-35 lb./ft.3, a water content of less than 12% by weight and 0À15- 0À44 ml./g. of pores of up to 2 microns in diameter. Such a composition preferably contains at least 50% by weight and preferably more than 85% by weight of Wegscheider's salt. The process also provides a composition in the form of needles of sodium sesquicarbonate having randomly oriented micro-needles of Wegscheider's salt randomly distributed therein in amounts of more than 50% by weight preferably more than 85% by weight. This composition has a bulk density of 12-25 lb./ft.3, a water content of less than 7% by weight and 0À02 to 0À42 ml./g. of pores up to 2 microns in diameter.