iron nitrate solution is a non-flammable chemical compound with the molecular formula FeN3O9. It appears as a violet crystalline solid and is completely soluble in water, alcohol, and acetone, but slightly soluble in cold concentrated nitric acid. It is an important reagent in analytical chemistry and is used by metalsmiths and jewellers to etch silver and silver alloys. It is also used as a mordant in dyeing, weighting silks, tanning and for inhibiting corrosion of metals. It is also an important ingredient of fertilizers and medicines.
The invention provides methods for stabilizing a mixture of ferrous and/or ferric nitrate solutions in order to produce stable iron-based Fischer-Tropsch catalysts. The stabilized mixed nitrate solution allows for efficient production of a desired catalyst ratio and avoids constant re-mixing in the precipitation step of the manufacturing process. The stability of the mixed nitrate solution can be improved further by using an acid addition technique that is less likely to cause volume loss, and/or by stirring the mixture for longer before adding the acid.
In one embodiment, the solution is stirred for a period of time prior to acid addition in order to promote more complete dissociation of the iron metal. Furthermore, the solution is filtered prior to acid addition to eliminate any undissolved particles of iron metal. The acid addition is performed at a temperature of greater than about 30 C, and the solution is stirred for a period time (e.g., at least 45 minutes) after acid addition in order to facilitate more rapid dissociation of the iron metal.