Changes in the physicochemical and catalytic properties of iron-potassium catalysts during their operation in a reactor for ethylbenzene to styrene dehydrogenation at PJSC «Nizhnekamskneftekhim»

Abstract

The paper presents the results of studying the iron-potassium catalysts for dehydrogenation of ethylbenzene (EB) to styrene, both fresh and spent, under industrial conditions: Cat-1 (imported), Cat-2 and Cat-3 (domestic). The initial samples are the multiphase systems consisting of potassium ferrites, hematite and cerianite (CeO2). After two years of operation, the phase composition of the catalysts was represented mostly by magnetite and cerianite, and potassium (K+) content in Cat-1, Cat-2 and Cat-3 samples decreased by 40, 20 and 26 %, respectively. Therewith, the Cat-2 sample retained a uniform K+ distribution in the spent catalyst grain. According to XRD data, the coherent scattering region (CSR) of CeO2 crystals in this sample did not change significantly. In the Cat-3 sample, the CSR size of CeO2 crystals decreased from 302 to 110 Å, while in Cat-1 it increased from 284 to 419 Å. After a two-year operation, the highest EB conversion equal to 72.1 % was observed on the Cat-2 sample, whereas on Cat-3 it decreased from 72.3 to 57.4 %. A 6÷11-fold decrease in the crushing strength was found for the spent samples, which made them unsuitable for further application.