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Abstract: Six industrial clinker samples, produced using petroleum coke as kiln fuel, were analysed using high resolution synchrotron XRPD data, one sample (HM) presenting predominantly M1 C3S polymorph. Refinement of data collected on this sample was used to revise the M1 structural model, improving the Rwp and RB of the original model (from Rwp = 9.25 and RB = 5.517 in the original model to Rwp = 8.07 and RB = 2.965). The revised model was validated through bond length and Bond Valence Sum (BVS) distribution. Using the BVS method, two preferential substitutional calcium sites were identified for Mg2+ and two silicon sites for Al3+, while two interstitial sites were identified for S6+ and Fe3+. Using the revised model for refinement of the six industrial clinker samples showed improvement in the Rwp and GoF indices. The amount of M1 and M3 polymorph present was found to be significantly different using the revised M1 C3S model.

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Abstract: The efficient removal of alkyne impurities for the production of polymer-grade lower olefins remains an important and challenging goal for many industries. We report a strategy to control the pore interior of faujasite (FAU) zeolites by the confinement of isolated open nickel(II) sites in their six-membered rings. Under ambient conditions, Ni@FAU showed remarkable adsorption of alkynes and efficient separations of acetylene/ethylene, propyne/propylene, and butyne/1,3-butadiene mixtures, with unprecedented dynamic separation selectivities of 100, 92, and 83, respectively. In situ neutron diffraction and inelastic neutron scattering revealed that confined nickel(II) sites enabled chemoselective and reversible binding to acetylene through the formation of metastable [Ni(II)(C2H2)3] complexes. Control of the chemistry of pore interiors of easily scalable zeolites has unlocked their potential in challenging industrial separations.

Open Access

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Abstract: This paper describes the synthesis, crystal structure, and NH3 sorption properties of Mg1-xMnx(NH3)6Cl2 (x = 0–1) mixed metal halide ammines, with reversible NH3 storage capacity in the temperature range 20–350 °C. The stoichiometry (x) dependent NH3 desorption temperatures were monitored using in situ synchrotron radiation powder X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. The thermal analyses reveal that the NH3 release temperatures decrease in the mixed metal halide ammines in comparison to pure Mg(NH3)6Cl2, approaching the values of Mn(NH3)6Cl2. Desorption occurs in three steps of four, one and one NH3 moles, with the corresponding activation energies of 54.8 kJ⋅mol-1, 73.2 kJ⋅mol-1 and 91.0 kJ⋅mol-1 in Mg0.5Mn0.5(NH3)6Cl2, which is significantly lower than the NH3 release activation energies of Mg(NH3)6Cl2 (Ea = 60.8 kJ⋅mol-1, 74.8 kJ⋅mol-1 and 91.8 kJ⋅mol-1). This work shows that Mg1-xMnx(NH3)yCl2 (x = 0 to 1, y = 0 to 6) is stable within the investigated temperature range (20–350 °C) and also upon NH3 cycling.

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Abstract: Heating of the K2ZrF6 room temperature monoclinic form-I reveals a complex polymorphism investigated by synchrotron powder temperature-dependent diffraction. The first thermal event at 240 °C corresponds to the quasi-simultaneous apparition of four different phases (noted II to V) of which only three could be indexed and two completely characterized structurally. Form-II (structure unrefined) is very probably hexagonal (a = 6.4473(1) Å, c = 3.8606(1) Å at 264 °C, Z = 1). Form-III is cubic (space group Fm3 ̅m, a = 9.0804(1) Å at 264 °C, Z = 4), related to K3ZrF7. Form-IV remains unindexed, presenting broad diffraction peaks. Form-V is present as a weak impurity at this stage, increasing in proportion after the second thermal event at 288 °C where a new form-VI is built. Form-V is tetragonal (space group P4/nmm, a = 6.3281(1) Å, c = 9.3671(2) Å at 295 °C, Z = 2) and form-VI is orthorhombic (space group Cmcm, a = 6.40840(5) Å, b = 20.7697(2) Å, c = 19.9888(2) Å, at 295 °C, Z = 16). At 317 °C, form-VI transforms into form-V. At 449 °C, a different orthorhombic form-VII is disclosed (space group Pnma, a = 10.3084(1) Å, b = 6.0291(1) Å, c = 23.8023(2) Å, at 495 °C, Z = 8), coexisting with the cubic form-III. On cooling, form VII of which an approach of the crystal structure is provided, returns to form V at 411 °C which looks stable down to 139 °C giving form I back. Isolated ZrF6 octahedra are present in forms-III, -V, -VI, -VII. Form-VI contains also dimeric entities Zr2F12 built from a ZrF7 monocapped trigonal prism sharing a corner with a ZrF6 octahedron. Form-VII structure is related to form-V by quadrupling the tetragonal a parameter, the reversible VVII transition is very probably topotactic. The coexistence of several phases at each temperature above the first transition at 240 °C was observed. Peak multi-splitting is observed at many temperatures that suggests the occurrence of coexisting micro-phases. The parallel existence of several phases was observed also by 19F MAS NMR spectroscopy measured from 250 oC → 410 oC → RT.

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Abstract: The adsorbate interactions of furans as probe molecules in H-ZSM-5 and H-USY with and without metal ion modification have been revealed by synchrotron X-ray powder diffraction (SXRD). The Rietveld refinements give both qualitatively and quantitatively the spatial arrangements and adsorption geometries of furan and 2,5-dimethylfuran (DMF) on the Brønsted acid sites (BAS) and metal Lewis acid sites (LAS). The bonding information between the adsorbate-framework can also be correlated with thermogravimetric findings. The use of probe molecule-SXRD can be used as a new characterisation tool which can spatially interrogate the acidity of crystalline porous catalysts, leading to molecular engineering of new catalytic systems.