Allylic isomerization of dichlorobutenes catalyzed by iron-containing nanoparticles stabilized in polymeric matrices

Abstract

Iron-containing clusters obtained by the decomposition of iron complexes in a solution--moll of a polymeric matrix exhibit catalytic activity in the isomerization of dichlorobutenes. The activity of the clusters stabilized in the polytetrafluoroeti]ytene and polyethylene matrices depends on the nature of the stabilizing matrix and the content of the metal in it, i.e., on the size and structure of the cluster, and substantially exceeds the activity of supported metals and powders. The clusters in the polytetrafluoroethylene matrix are more active than those in polyethylene. The dependence of the catalytic activity on the metal content has an extreme character, and for the polyethylene matrix it achieves a maximum at a metal content of ~10%. In catalysts with this composition, the particle size increases to 4--5 nm, and the distance between them is shortened, on the average, to 10 nm, which leads to interaction of the cluster particles with each other.Key words: iron, clusters, polymer matrix, particle size, structure, catalysis, isomerization, dichlorobutenes.Clusters and metal panicles immobilized in polymer matrices attract the attention of researchers as promising catalysts of many processes. Reactions in which the catal,,tic properties of the metal depend on the size or structure of particles, 1 in particular, allylic isomerization of dichlorobutenes (DCB), z,3 are of special interest.3,4-DCB 1,4-DCB The rate and selectivity of this process in the presence of palladium nanoparticles immobilized in the polyparaxylilene matrix depend on the character of interaction of the particles, which is defined by the size of nanoparticles and the distance between them. The specific activity of the samples prepared by cry ochemical synthesis is also related to the average distance between the nanoparticles in the polymer and electroconductivity of the sample. When these factors change, the isomeric composition of 1,4-DCB that formed changes: for isolated nanoparticles and metal powder, the trans-to cisisomers ratio in the products is (7--81 : I, and in the case of nanoparticle ensembles, the ratio decreases to 1"2--3): I. 2.3 it was of interest to reveal whether the regularities observed can be extended to other catalysts of the cluster type. In this work, we studied atlylic isomerization of dichlorobutenes in the presence of iron-containing clusters immobilized in polytetrafluoroethylene (PFE) or polyethylene (PE) matrices. Reaction (1) was chosen as the model because it is catalyzed by several metals, in particular, Fe ~ carbonyl complexes, Fe Ill compounds, Cu clusters and polynuclear complexes, 4-9 and Pd. z,3 The activity of the catalysts was assumed to be the ratio of the number of moles of DCB formed during the experiment to the number of g-atoms of iron in a weighed sample of the catalyst and the duration of the experiment in hours (the average catalyst turnover/tool (mol h)-t). ExperimentalIron-containing composites in PFE and PE matrices were prepared by monomolecular decomposition of iron carbonyl Fe(CO) s in a s...

Nanochemistry of metals

“…Isomerisation of dichlorobutanes catalysed by iron-containing nanoparticles stabilised in polymeric matrices was studied. 153 The catalytic activity was shown to depend on the nature of the matrix and the metal content.…”