Ferrous sulfate catalyst activator

As to catalytic reactions in homogeneous media, Moritz Traube found in his studies of the oxidation of hydrogen iodide by hydrogen peroxide in aqueous solution, that the catalyst ferrous sulfate is activated by copper sulfate (5). As to the magnitude of such effects, Price stated in 1898 (6) that the simultaneous action of iron and of copper compounds on the reaction between persulfate and hydrogen iodide causes an unexpected acceleration of the reaction, which is more than twice as great as the acceleration calculated as an additive effect of the two single catalysts. However, effects were also observed of the opposite kind,... 

Chromium compounds increase the activity of platinum catalysts by increasing the electron densities of the active sites. jhe addition of ferrous sulfate, which promotes the hydrogenation of carbonyl groups, and zinc acetate, which inhibits the hydrogenation of double bonds, to platinum gives a catalyst system capable of effecting the selective hydrogenation of an unsaturated aldehyde to an unsaturated alcohoP - (Eqn. 11.12). ... 

In vinyl compound polymerization of vinyl acetate, alcohol, bromide, chloride, or carbonate, ascorbic acid can be a component of the polymerization mixture (733-749). Activators for the polymerization have been acriflavine (734), other photosensitive dye compounds (737,738), hydrogen peroxides (740,741,742), potassium peroxydisulfate (743), ferrous sulfate, and acyl sulfonyl peroxides (747). Nagabhooshanam and Santappa (748) reported on dye sensitized photopolymerization of vinyl monomers in the presence of ascorbic acid-sodium hydrogen orthophosphate complex. Another combination is vinyl chloride with cyclo-hexanesulfonyl acetyl peroxide with ascorbic acid, iron sulfate, and an alcohol (749). Use of low temperature conditions in emulsion polymerization, with ascorbic acid, is mentioned (750,751). Clarity of color is important and impact-resistant, clear, moldable polyvinyl chloride can be prepared with ascorbic acid as an acid catalyst (752) in the formulation. 

In the reduction of Ni(II) ion with hydrogen catalysts such as platinic chloride, ferrous sulfate, palladium chloride, and silver sulfate, the number of active sites can significantly increase, resulting in a finer subgrain size [7]. The subgrains were spherical or blocklike indicating a uniform growth rate in all directions. 

Accelerators have sometimes been employed in aqueous polymerization. Water-soluble metal salts of sulfates, nitrates, phosphates, and chlorides were among the effective accelerators. Specific compounds of this class include cuprous sulfate, ferrous sulfate, and silver nitrate. The amount of accelerator used in the reaction mixture was between 0.05 and 0.5 part per hundred parts of total monomers. When an activator such as sodium metabisulfite and an accelerator such as a ferrous sulfate are selected, the catalyst/initiator system is called a rec/ov system. The peroxides recommended by worked best in a redox catalyst system. 

In the original German process acetylene is injected into an aqueous solution of mercuric sulfate acidified with sulfuric acid at 90-95°C and about 1-2 atm. As a result of side reactions, the catalytically active mercury(II) ions are reduced to mercury. To prevent this process ferric sulfate is continuously added to the reactor. Since ferric ions are reduced to ferrous ions, the catalyst solution requires reactivation, which is accomplished by hot nitric acid and air. Excess acetylene and acetaldehyde formed are removed, cooled, absorbed in water, and then separated by distillation. Excess acetylene is recycled. Conversion per pass is bout 55%. The Montecatini process89 operates at 85°C and provides 95% overall yield. A modification developed by Chisso90 allows lower operating temperature (70°C) without excess acetylene. Since side reactions are less important under these conditions, higher yields may be achieved. 

A belief sometimes expressed by catalysis chemists is that this particular catalyst is not active unless there is present some chromium in a higher oxidation state. The presence of such oxidized chromium is readily detected by extraction of the sample with water, followed by titration of the extract with ferrous ammonium sulfate solution, followed by back titration with standard dichromate. All such tests on the catalyst samples prepared as described above were negative. Chromium in a higher oxidation state is, however, always present if the final step of reduction in hydrogen is omitted. 

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