Impact of composition and structural parameters on the catalytic activity of MFI type titanosilicalitesстатья
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Аннотация:Titanosilicalite of the MFI type was obtained by the hydrothermal method. Its initial and annealedat 75oC (TS-1P(75)) and 500oC (TS-1P(500)) forms were studied by X-ray powder diffraction(XRPD), X-ray absorption spectroscopy (XAS-method), IR spectroscopy (FT-IR), differentialscanning calorimetry (DSC), temperature-programmed ammonia desorption (TPD NH3), pyridineadsorption (Py). The full-profile Rietveld method allowed to find the presence of the organictemplate tetrapropylammonium hydroxide (TPAOH) in the framework voids, as well as todetermine the silicate module (Si/Ti = 73.5) and the distribution of Ti4+ ions over the MFI-typePage 1 of 31 Dalton TransactionsDalton Transactions Accepted ManuscriptPublished on 31 January 2022. Downloaded on 2/4/2022 8:43:58 AM.View Article OnlineDOI: 10.1039/D1DT04131B2structure sites (Ti atoms replace Si ones in two positions: T1 and T6). The coordination numbers oftitanium (CNTi=4.6 for TS-1P and TS-1P(75), CNTi=3.8 for TS-1P(500)) were established byXAS-method. The catalytic activity of titanosilicalites was found in the reactions of nitrous oxidedecomposition (maximal decomposition rate is demonstrated for the TS-1P(75) sample), allylchloride epoxidation to epichlorohydrin (the best combination of all indicators exhibited for the TS-1P sample) and propane conversion (maximum propane conversion, butadiene and propyleneselectivity were observed in both TS-1P(75) and TS-1P(500) samples). The mechanisms of thecatalytic processes were proposed. The relationship between the catalytic properties and thecomposition (Si/Ti), Ti4+ ions distribution over the MFI-type structure sites, the titanium ions localenvironment, and the number of acid sites in the titanosilicalites was discussed.