Changes in the Physicochemical and Catalytic Properties of Iron–Potassium Catalysts under Operation in a Reactor of Ethylbenzene Dehydrogenation to Styrene at Nizhnekamskneftekhim

A study of original iron–potassium catalysts of ethylbenzene (EB) dehydrogenation to styrene and industrially used catalysts: Cat-1 (imported), Cat-2 and Cat-3 (domestic) is performed. Initial samples are multiphase systems consisting of potassium ferrites, hematite, and cerianite (CeO₂). The phase composition of the catalysts after two years of operation consists mainly of magnetite and cerianite, while the amount of potassium (K⁺) in Cat-1, Cat-2, and Cat-3 samples falls by 40, 20, and 26%, respectively. At the same time, K⁺ for the Cat-2 sample is distributed uniformly in granules of the waste catalyst. XRD data indicate the CSR size of its CeO₂ crystals does not change appreciably. The CSR size of CeO₂ crystals in the Cat-3 sample falls from 302 to 110 Å, while it grows from 284 to 419 Å in the Cat-1 sample. After two years of operation, the greatest conversion of EB (72.1%) was observed for the Cat-2 sample, and it fell from 72.3 to 57.4% on the Cat-3 sample. There is a 600–1100% drop in the waste samples’ resistance to crushing, making them unsuitable for further use.