Dealumination of NH(4)-Y zeolite during steaming to 873 K was investigated with in situ, time-dependent, synchrotron radiation XRPD and in situ Al K-edge XAS. Water desorption is complete at 450 K, and ammonium decomposition occurs between 500 and 550 K. Only a small fraction of Al(3+) species (5%) leaves the framework during heating from 710 to 873 K; these species occupy site I' inside the sodalite cage. This fraction increases up to 8% in the first 50 min at 873 K and remains constant for the following 70 min isotherm and during the high-temperature part of the cooling experiment. During cooling from 500 to 450 K, the electron density at site I' increases suddenly, corresponding to a fraction of 30-35% of the total Al, confirmed by ex situ (27)Al MAS solid-state NMR. At that temperature, in situ Al K-edge XAS indicates a change in Al coordination of a large fraction of Al, and thermogravimetric (TG) data show the first water molecules start to repopulate the pores. Such molecules drive the dislodgment of most of the Al from the zeolitic framework. Our data indicate that considerable structural collapse caused by steaming does not occur at the highest temperature; however, defects form, which lead to significant migration of framework Al(3+) to extraframework positions, which occurs only as water is able to enter the pores again, that is, at much lower temperature. Contrary to general opinion, these results demonstrate that zeolite dealumination is not primarily a high-temperature process. The standard Rietveld refinement approach failed to identify extraframework Al species. These new results were obtained by adopting the innovative parametric refinement [J. Appl. Crystallogr. 2007, 40, 87]. Treating all of the XRPD patterns collected during the evolution of temperature as one unique data set significantly reduces the overall number of optimized variables and, thus, their relative correlation, and finally results in a more reliable estimate of the optimized parameters. Our results contribute to a better understanding of the phenomena involved on the atomic scale in the preparation of ultrastable Y zeolites (USY). USY are employed in fluid catalytic cracking (FCC), which is the most important conversion process in petroleum refineries to convert the high-boiling hydrocarbon fractions of petroleum crude oils to more valuable products like gasoline and olefinic gases.

The structure of [Fe(Htrz) 2 (trz)]BF 4 (1, Htrz )1,2,4-4-H-triazole, trz ) 1,2,4-triazolate) at the low-spin (LS) and high-spin (HS) states and structural transitions between the two states were investigated by in situ highresolution synchrotron X-ray powder diffraction (XRPD) combined with Raman spectroscopy using a modulation-enhanced technique. The crystal structures of the LS and HS states were determined. A 1D chain structure of 1 at both LS and HS states was proven, and the lattice expansion upon LS-HS transition was mainly caused by the elongation of the chain. The differences in the behavior of the spin transition observed by XRPD and Raman spectroscopy were explained by the local sensitivity of the two different techniques and also by the spatial propagation of spin crossover phase transition within the crystallite and the body of the grain. Moreover, we demonstrated that the two-dimensional correlation analyses facilitate (i) understanding the data obtained by combined techniques, (ii) clarifying correlation between the signals gained by the different probes, and (iii) extracting information on temporal evolution of transformation processes.

The high X-ray flux available at the European Synchrotron Radiation Facility (ESRF), combined with the use of a suitably designed area detector setup, allowed us to follow in real time the structural changes occurring during the template burning processes inside TS-1 and Fe-silicalite MFI zeolites with a X-ray powder diffraction technique (XRPD). Rietveld analysis of the XRPD patterns collected in the 350-1000 K interval, integrated each 15 K, yields to the determination of the template overall occupancy factor versus T with an accuracy comparable with that obtained by thermogravimetric measurements, routinely employed for this purpose. The evolution of the structural parameters (V, a, b, c, site occupancy factor of the template molecule) vs T has been obtained. These data allow us to have, for the first time, a complete view of the structural rearrangements induced by the template burning process on the zeolitic framework. The differences caused by the different heteroatom inserted in the MFI lattice (Ti or Fe) are discussed. For both TS-1 and Fe-MFI, the kinetics of the reaction were investigated, to obtain the activation energy of the calcinations process employing the nonisothermal data according to the theory recently proposed by Kennedy and Clark [Thermochim. Acta, 1997, 307, 27-35]. For TS-1 only, the time-resolved template burning experiment has been repeated in isothermal conditions at four different temperatures, to obtain the activation energy from isothermal data, according to the standard procedure. Comparison between Arrhenius plots obtained from isothermal and nonisothermal data demonstrates that the Kennedy and Clark method can be also applied to complex materials such as the MFI zeolites. This approach, when applied to time-resolved XRPD studies, is much less time consuming (requesting, in principle, one single nonisothermal run) with respect to the classic approach, which requests at least three isothermal runs. Moreover, it allows a remarkably lower associated error (151 +/- 11 versus 146 +/- 30 kJ mol(-)(1)) due to the much higher number of experimental points employed to perform the linear fit.