Production Of Cesium Formate
Extraction Of Cesium
Caesium is an element traditionally extracted from pollucite ((Cs,Na)2Al2Si4O12.2H2O). This mineral is particularly rich in sodium and aluminium, but also contains caesium or rubidium. This type of ore was discovered in 1846 by August Breithaupt, but it wasn’t until 1864 that a detailed chemical analysis identified the presence of caesium, four years after the discovery of the mineral itself. Although it was originally found in Italy, over 80% of the world’s reserves are located in Bernic Lake in Manitoba, Canada.
Following crushing and grounding, caesium is extracted from the ore usually by one of three methods:
- Acid digestion
- Direct reduction
- Alkaline decomposition
This is the most popular method. In this case, pollucite is dissolved in the presence of strong acids (such as sulphuric acid, hydrochloric acid, hydrofluoric acid or hydrobromic acid). Although possible, hydrofluoric and hydrobromic acids incur many processing difficulties and are not usually used.
When hydrochloric acid is used at high temperatures, caesium precipitates in the form of caesium hexachlorocerate (Cs2(CeCl6)), caesium iodine chloride (Cs2ICl) and caesium antimony chloride (Cs4SbCl3). Following evaporation, the precipitated double salts are decomposed and generate pure caesium chloride (CsCl).
Pollucite can also be digested in the presence of hot sulphuric acid (35 to 45% solution), producing caesium aluminium (CsAl(SO4)2.12H2O), which can be converted to aluminium oxide by roasting with carbon (4% solution), releasing a caesium sulphate (Cs2SO4) solution, which can subsequently be converted to caesium chloride (CsCl).
Direct reduction refers to heating the ore in the presence of potassium, calcium or sodium in vacuum, producing caesium metal. However, because of impurities and technical difficulties, this method is not commercially viable.
This process involves roasting pollucite in the presence of a Na2CO3/NaCl mixture or a CaCO3/CaCl2 mixture, followed by calcination with water and diluted ammonia (NH4OH) to release caesium chloride (CsCl), which can subsequently be converted to caesium aluminium (C2 SO4:Al2(SO4)3:24H2O) or caesium carbonate (Cs2CO3).
Production Of Cesium Formate
Caesium formate (CsHCOO) is obtained from caesium hydroxide (CsOH) and formic acid (HCOO), according to the reaction:
CsOH + HCOO → CsHCOO + H2O
This process was developed in the mid 1990s specifically to be used as drilling fluid, particularly suitable in high-temperature high-pressure oil and gas wells. To supply an increasingly demanding market, in 1996 Cabot Corporation started extracting caesium from pollucite at their Tanco mine (in Manitoba, Canada). Currently, this chemical is transferred to their manufacturing plant in Houston (Texas), which boasts a capacity to generate over 12,000 barrels every year of caesium formate solution. The company also produces caesium nitrate and chloride used for small-scale applications.
Cesium Formate Suppliers
Cesium formate can be purchased from a range of suppliers and distributors both large and small including ReAgent and Cabot Corporation