9003-17-2Relevant articles and documents
Impact of composition and structural parameters on the catalytic activity of MFI type titanosilicalites
Bruk, Lev,Chernyshev, Vladimir,Khramov, Evgeny,Kravchenko, Galina,Kustov, Aleksander,Kustov, Leonid,Kuz'Micheva, Galina,Markova, Ekaterina,Pastukhova, Zhanna,Pirutko, Larisa
, p. 3439 - 3451 (2022/03/14)
Titanosilicalite of the MFI type was obtained via a hydrothermal method. Its initial and annealed at 75 °C (TS-1P(75)) and 500 °C (TS-1P(500)) forms were studied by X-ray powder diffraction (PXRD), X-ray absorption spectroscopy (XAS-method), Fourier-transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), temperature-programmed ammonia desorption (TPD NH3), and pyridine adsorption (Py). The full-profile Rietveld method allowed us to observe the presence of the organic template tetrapropylammonium hydroxide (TPAOH) in the framework voids, as well as to determine the silicate module (Si/Ti = 73.5) and the distribution of Ti4+ ions over the MFI-type structure sites (Ti atoms replace Si ones in two positions: T1 and T6). The coordination numbers of titanium (CNTi = 4.6 for TS-1P and TS-1P(75), CNTi = 3.8 for TS-1P(500)) were established by the XAS-method. The catalytic activity of titanosilicalites was found in the reactions of nitrous oxide decomposition (the maximal decomposition rate is demonstrated for the TS-1P(75) sample), allyl chloride epoxidation to epichlorohydrin (the best combination of all indicators was exhibited for the TS-1P sample) and propane conversion (maximum propane conversion, and butadiene and propylene selectivity were observed in both TS-1P(75) and TS-1P(500) samples). Mechanisms for the catalytic processes are proposed. The relationship between the catalytic properties and the composition (Si/Ti), Ti4+ ion distribution over the MFI-type structure sites, the local environment of titanium ions, and the number of acid sites in the titanosilicalites are discussed.
Effect of Steam–Air Treatment of Alumina–Chromia Dehydrogenation Catalysts on Their Physicochemical and Catalytic Characteristics
Nazimov,Klimov,Saiko,Noskov
, p. 1283 - 1291 (2021/12/29)
The effect of calcined alumina–chromia catalyst containing 13 wt.% Cr with additions of Na+ and Zr4+ in an air–water vapor atmosphere (from 0 to 80 vol % water vapor) at 750°С and a pressure of 1 bar on the physicochemical properties of the catalyst and its activity in n-butane dehydrogenation was evaluated. The steam treatment led to a slight decrease in the specific surface area (by up to 10%), partial decomposition of Cr(VI) compounds (up to 60%), and Cr2O3 crystallization. The catalytic activity decreased with an increase in the water vapor:air ratio. Low water vapor concentration (10 vol %) favored a remarkable decrease in the amount of the coke formed (by 60%) without considerably affecting alkene yield. Thus, the introduction of water vapor into the calcination atmosphere allowed control of the Cr(VI) amount and catalyst selectivity.
Understanding Ta as an Efficient Promoter of MgO–SiO2 Catalyst for Conversion of the Ethanol–Acetaldehyde Mixture into 1,3-Butadiene
Gao, Qiang,Jiang, Angjiong,Jiang, Haoxi,Yang, Guochao,wang, Lingtao
, (2021/10/27)
In this work, Ta was firstly reported as an efficient promoter of MgO–SiO2 for the conversion of ethanol and acetaldehyde to 1,3-butadiene. The doping of Ta into MgO–SiO2 forms Ta–O–Si bonds and generates more strong Lewis acid sites, which not only promote the aldol condensation reaction but also significantly facilitate the Meerwein–Ponndorf–Verley reduction, the total conversion around 80% which drops to 65% after 24?h. In addition, the catalyst showed desirable stability in 24?h long-term stability evaluation, the selectivity remained stable at 80%. Graphic Abstract: [Figure not available: see fulltext.]
