Calcium formate

The reaction of formate salts with mineral acids such as sulfuric acid is the oldest iadustrial process for the production of formic acid, and it stiU has importance ia the 1990s. Sodium formate [141-53-7] and calcium formate [544-17-2] are available iadustriaHy from the production of pentaerythritol and other polyhydric alcohols and of disodium dithionite (23). The acidolysis is technically straightforward, but the unavoidable production of sodium sulfate is a clear disadvantage of this route. 

A diagram for one implementation of this process (61,62) is shown in Eigure 11. Recovered potassium sulfate is converted to potassium formate [590-29 ] by reaction with calcium formate [544-17-2] which is made by reacting hydrated lime, Ca(OH)2, and carbon monoxide. The potassium formate (mp 167°C), in hquid form, is recycled to the combustor at about 170°C. Sulfur is removed as soHd calcium sulfate by filtration and then disposed of (see... 

The above series of alcohols are exceedingly difficult to manufacture, hence their expense. The general method of their preparation would theoretically be by distilling the calcium salts of the corresponding fatty acid with calcium formate, in vacuo. This would yield the corresponding aldehyde, which on reduction would yield the corresponding alcohol. In practice, however, many technical difficulties arise, and special processes have to be used which are kept carefully as trade secrets. 

Citral can also be obtained in a pure state by distilling a mixture of the calcium salt of geranic acid with calcium formate, according to the usual method tor the production of aldehydes. 

Isothermal a—time curves were sigmoid [1024] for the anhydrous Ca and Ba salts and also for Sr formate, providing that nucleation during dehydration was prevented by refluxing in 100% formic acid. From the observed obedience to the Avrami—Erofe ev equation [eqn. (6), n = 4], the values of E calculated were 199, 228 and 270 kJ mole"1 for the Ca, Sr and Ba salts, respectively. The value for calcium formate is in good agreement with that obtained [292] for the decomposition of this solid dispersed in a pressed KBr disc. Under the latter conditions, concentrations of both reactant (HCOJ) and product (CO3") were determined by infrared measurements and their variation followed first-order kinetics. 

Precipitation Heavy metals Sodium or calcium Formation of insoluble metal precipitate,... 

Calcium carbide, 32, 70 Calcium carbonate, 32, 81 Calcium formate, 31,102 CAPROIC ACID, e-AMINO, 32, 13 e-Caprolactam, 31, 72 32, 15 e-CAPROLACTIM, O-METHYL-, 31, 72 CAPRONITRILE, a-ETHYL, 32, 6S Caproyl chloride, 31, 71 CARBANILINONITRILE, O-CHLORO, 31, 19... 

In the production of formic acid, a slimy of calcium formate in 50% aqueous formic acid containing urea is acidified with strong nitric acid to convert the calcium salt to free acid, and interaction of formic acid (reducant) with nitric acid (oxidant) is inhibited by the urea. When only 10% of the required amount of urea had been added (unwittingly, because of a blocked hopper), addition of the nitric acid caused a thermal runaway (redox) reaction to occur which burst the (vented) vessel. A small-scale repeat indicated that a pressure of 150-200 bar may have been attained. A mathematical model was developed which closely matched experimental data. 

Investigation of the above reaction by Levi Piva dicates that the chemical change takes place in two iges, in the first of which calcium formate is produced, lile in the second it is decomposed with the evolution hydrogen and carbon monoxide as is shown in the [lowing equations.—... 

When heated with carbon monoxide under pressure, the product is calcium formate, Ca(HCOO)2 ... 

In view of the known deleterious effect of admixtures containing calcium chloride and the possibility of the same effect being found with calcium formate, it is suggested that accelerating water-reducing admixtures should not be used in those areas where sulfate resistance is of importance. 

This category of admixture is based mainly on the major raw materials, calcium chloride, calcium nitrate, calcium formate [2] and calcium thiocyanate, with minor amounts of other materials occasionally being included in the formulations, such as calcium thiosulfate [3] and triethanolamine (TEA). TEA is not normally used alone but because it is sometimes used in other categories of admixture to compensate for retarding influences it will be included in this section. 

The reactions occurring with calcium formate, nitrate and thiosulfate have not been widely studied, although it seems likely that calcium formate and thiosulfate [6] react with C3 A in a similar manner to calcium chloride to... 

The way in which salts such as calcium chloride and calcium formate operate is not fully understood, but it is clear that the mechanism involves an acceleration of the C2S and C3S hydration. It has been proposed [23] that... 

The heat evolution of concrete mixes containing no admixture, 1.5% calcium chloride and 3.0% calcium formate is shown in Fig. 5.18. The heat evolution of calcium chloride and calcium formate are approximately equal at 24 h, which is reflected in similar compressive strengths at this age of 10.0 and 12.5 N mm i. 

The initial and final setting times are also reduced at lower temperatures, as shown in Fig. 5.19 for a calcium-formate-based material [7]. The relationship between temperature and setting time for calcium chloride and a nonchloride... 

Table 5.4 Influence of calcium formate on the compressive strength of concrete ...

Fig. 5.32 Potential-time curves for plain concretes and concretes containing calcium-chloride and calcium-formate-based accelerators (McCurrich).

There is very limited information available on the effect of calcium formate and nitrate but certainly the passive layer at the concrete/steel... 

Table 5.6 Drying shrinkage of concretes containing calcium chloride, triethanolamine and calcium formate...

There are only limited data available on the effect of other accelerating admixtures, although one comparative study [46] suggests that calcium formate... 

Admixture formulations containing two or more compounds (multicomponent) in which each component plays a specific role or compliments the corrosion resistance capacities of the other are also used. For example, a mixture of calcium nitrite and calcium formate is used to both accelerate strength of the concrete and inhibit corrosion of the steel during steam curing. 

Calcium formate is usually sold as a powder and used at a dosage of 1-2% by weight of cement. Due to its very low solubility in water (16 g/100 g H2O), the material is not commercially available in liquid form. The... 

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