Ferrocene-containing compounds as combustion catalysts and solid fuel modifiers

Abstract

Low pressure profile and stable burning rate are important and necessary characteristics of high-quality solid fuels. Achieving their optimal values is accomplished by incorporating combustion catalysts. There are several types of combustion catalysts, such as metal nanoparticles, oxides, transition metal chelates, and catalytic mixtures based on them. Among catalysts, ferrocene and its compounds hold a special place. They are widely used in the aerospace industry due to their superior microscopic homogeneity, proper ignitability of rocket fuel, and compatibility with organic binders. However, ferrocene compounds tend to migrate within the composite, leading to matrix degradation, reduced storage life, and shorter operational lifespan of the fuels. Polymeric ferrocene catalysts represent a new generation of catalysts that retain activity while exhibiting reduced migration tendencies. They have a polymeric structure in which the ferrocene group can be placed in the main or side chain. In this study, in addition to reviewing current knowledge on polymeric ferrocene combustion catalysts, synthesis methods and their application results were examined, as well as their migration in fuels compared to other catalysts. The conducted research demonstrated that polymeric ferrocene catalysts are synthesized through free-radical and graft polymerization, resulting in dendrimer-like polymers. Furthermore, the use of a hyperbranched polymeric ferrocene catalyst, compared to a ferrocene catalyst bound to a small molecular group, simultaneously reduced the migration rate by 90%. The iron content in the catalyst, the polymer's molecular weight, the placement of ferrocene in the polymer structure, and the degree of linearity of the polymeric structure are among the most important factors influencing the efficiency of these catalysts.