To track dehydration behavior of cavansite, Ca(VO)(Si 4 O 10 )·4H 2 O [space group Pnma, a = 9.6329(2), b = 13.6606(2), c = 9.7949(2) Å, V = 1288.92(4) Å 3 ] single-crystal X-ray diffraction data on a crystal from Wagholi quarry, Poona district (India) were collected up to 400 °C in steps of 25 °C up to 250 °C and in steps of 50 °C between 250 and 400 °C. The structure of cavansite is characterized by layers of silicate tetrahedra connected by V 4+ O 5 square pyramids. This way a porous framework structure is formed with Ca and H 2 O as extraframework occupants. At room temperature, the hydrogen bond system was analyzed. Ca is eightfold coordinated by four bonds to O of the framework structure and four bonds to H 2 O molecules. H 2 O linked to Ca is hydrogen bonded to the framework and also to adjacent H 2 O molecules. The dehydration in cavansite proceeds in four steps. At 75 °C, H 2 O at O9 was completely expelled leading to 3 H 2 O pfu with only minor impact on framework distortion and contraction [V = 1282.73(3) Å 3 ]. The Ca coordination declined from originally eightfold to sevenfold and H 2 O at O7 displayed positional disorder. At 175 °C, the split O7 sites approached the former O9 position. In addition, the sum of the three split positions O7, O7a, and O7b decreased to 50% occupancy yielding 2 H 2 O pfu accompanied by a strong decrease in volume [V = 1206.89(8) Å 3 ]. The Ca coordination was further reduced from sevenfold to sixfold. At 350 °C, H 2 O at O8 was released leading to a formula with 1 H 2 O pfu causing additional structural contraction (V = 1156(11) Å 3 ). At this temperature, Ca adopted fivefold coordination and O7 rearranged to disordered positions closer to the original O9 H 2 O site.At 400 °C, cavansite lost crystallinity but the VO 2+ characteristic blue color was preserved. Stepwise removal of water is discussed on the basis of literature data reporting differential thermal analyses, differential thermo-gravimetry experiments and temperature dependent IR spectra in the range of OH stretching vibrations.

The average and the local structure of phosphorus-treated HZSM-5 zeolites were investigated by means of atom probe tomography, powder X-ray diffraction (at ambient and cryogenic temperatures) and 1H, 29Si, 27Al, and 31P magic angle spinning (MAS) solid state nuclear magnetic resonance (NMR) spectroscopy. Phosphatation to yield a product with P/Al ≤ 1 followed by thermal treatment leads to breaking of the Si-OH-Al bridging groups, and subsequent partial dealumination of the zeolite framework, as shown by the contraction of the orthorhombic unit-cell volume and by the loss of tetrahedral framework Al, as observed in the 27Al Multiple Quantum (MQ) MAS NMR spectrum. Most of the framework Al is present in an electronic environment distorted by the presence of phosphorus and appears not to be involved in classic Si-OH-Al Brønsted acid sites. The 31P MAS NMR signals indicate that phosphorus interacts with the zeolitic framework to locally form silico-aluminophosphate (SAPO) domains and the presence of a new kind of acidic site was confirmed by the resonance at ∼8.6 ppm in the 1H MAS NMR spectra, attributed to P-OH groups. Increasing the phosphorus loading (P/Al ≫ 1) promotes further dealumination of the framework and cross-dehydroxylation between P-OH and Si-OH species, leading to the formation of a crystalline silicon orthophosphate phase. With decreasing Al content, the monoclinic HZSM-5 structure becomes preferred, especially at 85 K where the strain relaxation is higher. However, the presence of a higher amount of silicophosphate impurities hinders the low-temperature strain release of the framework, indicating that some of these species are localized in the zeolite pores and contribute to the strain build up.

Ex situ catalytic biomass pyrolysis was investigated at both laboratory and bench scale by using a zeolite ZSM‐5‐based catalyst for selectively upgrading the bio‐oil vapors. The catalyst consisted of nanocrystalline ZSM‐5, modified by incorporation of ZrO2 and agglomerated with attapulgite (ZrO2/n‐ZSM‐5‐ATP). Characterization of this material by means of different techniques, including CO2 and NH3 temperature‐programmed desorption (TPD), NMR spectroscopy, UV/Vis microspectroscopy, and fluorescence microscopy, showed that it possessed the right combination of accessibility and acid–base properties for promoting the conversion of the bulky molecules formed by lignocellulose pyrolysis and their subsequent deoxygenation to upgraded liquid organic fractions (bio‐oil). The results obtained at the laboratory scale by varying the catalyst‐to‐biomass ratio (C/B) indicated that the ZrO2/n‐ZSM‐5‐ATP catalyst was more efficient for bio‐oil deoxygenation than the parent zeolite n‐ZSM‐5, producing upgraded bio‐oils with better combinations of mass and energy yields with respect to the oxygen content. The excellent performance of the ZrO2/n‐ZSM‐5‐ATP system was confirmed by working with a continuous bench‐scale plant. The scale‐up of the process, even with different raw biomasses as the feedstock, reaction conditions, and operation modes, was in line with the laboratory‐scale results, leading to deoxygenation degrees of approximately 60 % with energy yields of approximately 70 % with respect to those of the thermal bio‐oil.

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The behavior of natural microporous cavansite and pentagonite, orthorhombic dimorphs of Ca(VO)(Si 4 O 10 )•4H 2 O, was studied at high pressure by means of in situ synchrotron X-ray powder diffraction with a diamond anvil cell using two different pressure-transmitting fluids: methanol:ethanol:water = 16:3:1 (m.e.w.) and silicone oil (s.o.). In situ diffraction-data on a cavansite sample were collected up to 8.17(5) GPa in m.e.w, and up to 7.28(5) GPa in s.o.The high-pressure structure evolution was studied on the basis of structural refinements at 1.08(5), 3.27(5) and 6.45(5) GPa. The compressional behavior is strongly anisotropic. When the sample is compressed in s.o. from P amb to 7.28(5) GPa, the volume contraction is 12.2%, whereas a, b and c decrease by 1.6, 10.3 and 0.3%, respectively. The main deformation mechanisms at high-pressure are basically driven by variation of the T-O-T angles. Powder diffraction data on a pentagonite sample were collected up to 8.26(5) GPa in m.e.w and 8.35(5) GPa in s.o. Additional single-crystal X-ray diffraction experiments were 2 performed in m.e.w. up to 2.04(5) GPa. In both cases, pressure-induced over-hydration was observed in m.e.w. at high pressure. The penetration of a new H 2 O molecule leads to a stiffening effect of the whole structure. Moreover, between 2.45(5) and 2.96(5) GPa in m.e.w., a phase transition from an orthorhombic to a triclinic phase was observed. In s.o.pentagonite also transformed to a triclinic phase above 1.71(5) GPa. The overall compressibility of pentagonite and cavansite in s.o. is comparable, with a volume contraction of 11.6% and 12.2%, respectively.