Sodium Bicarbonate (Technical) - China

Brief Overview
Sodium bicarbonate, commonly known as baking soda, is a chemical compound denoted by the formula NaHCO3. It exists in the form of white crystalline or powder and readily dissolves in water or mineral springs. Found naturally as nahcolite or thermokalite, sodium bicarbonate is versatile, exhibiting amphoteric properties by reacting with both acidic and basic compounds. When it encounters acetic acid, it generates sodium acetate; when it meets bases like sodium hydroxide, it forms carbonates. Heating sodium bicarbonate above 149°C causes it to break down into sodium carbonate, water, and carbon dioxide, forming a stable compound.
Manufacturing Process
Sodium bicarbonate can be produced through the Solvay process, pioneered by Ernest Solvay in the 1860s. This method involves the reaction of sodium chloride with carbon dioxide and ammonia in water. The resulting sodium bicarbonate can then be converted into other compounds like soda ash (Na2CO3) or washing soda (Na2CO3.10H2O). The manufacturing process unfolds in the following steps:
1. Creating Sodium Bicarbonate
This initial phase entails the reaction between sodium chloride, carbon dioxide, and ammonia in water. Calcium carbonate serves as the source of carbon dioxide, and the resulting calcium oxide helps separate ammonia from ammonium chloride. Dry ice can also provide an additional source of carbon dioxide. The reaction is as follows:
NaCl(aq) + NH3(aq) + CO2(s) + H2O → NH4Cl(aq) + NaHCO3(s)
2. Separating Sodium Bicarbonate
The outcome of the first step includes sodium bicarbonate and ammonium chloride. Both compounds are soluble at room temperature, but below this temperature, ammonium chloride exhibits higher solubility than sodium bicarbonate, facilitating the extraction of crystals from the solution. Another method involves the reaction of calcium hydroxide with ammonium chloride, yielding ammonia gas, water vapor, and liquid-phase calcium chloride as products.