FTIR spectroscopy is used for the investigation of hydrogen bonding of the Bronsted hydroxyls in H-ZSM-5 zeolite with a number of weak bases (Ar, H2,02, N2, CH4, C2H6, CsHs, CO, C2H4). The following correlation for the increase in intensity of the hydroxyl band, due to its shift resulting from perturbation, is observed: M I A 0 = 0.018Auo~. Applying this correlation to the HF-LF pair in the infrared spectra of H-Y, H-EMT, and H-EM0 zeolites, it is shown that the distribution of Bronsted hydroxyls between super and @cages is approximately 1: 1 whereas in SAPO-37 samples this ratio is close to 3: 1. This is in agreement with results for the deconvolution of the hydroxyl region of the lH MAS N M R spectra. The estimated values of the extinction coefficients for the HF and LF band in H-Y zeolite (Si/Al = 2.7) are 3.2 and 8.5 cmpmol-l, respectively.

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Silicoaluminophosphate molecular sieves of SAPO-5 type are synthesized with variable Si/(AI + P + Si) mole ratios using triethylamine as the organic additive. The crystalline products are characterized by several physico-chemical methods. Incorporation of silicon into the framework of SAPO-5 is demonstrated by the variation in the unit-cell volume with silicon mole fraction, chemical analysis and magic-angle-spinning nuclear magnetic resonance. When Si/(AI + P + Si) < 0.077, silicon substitutes predominantly for phosphorus. For compositions where Si/(AI + P + Si) > 0.077, it appears that a combination of mechanisms, substitution of one silicon for one phosphorus and substitution of two silicons for aluminium-phosphorus pairs, takes place. Surface analysis using depth profiling shows an inhomogeneous distribution of silicon at higher silicon content. Preliminary catalytic results in 0 -and rn-xylene isomerization are discussed. The aluminophosphate-based molecular sieves are an important relatively new class of adsorbents and catalytic material^.'^^ Microporous materials containing framework silicon are denoted by the acronym SAP0.2,3 The generation of SAPOs is considered to follow a mechanism by which silicon substitutes into the corresponding AlPO, framew o r k ~. ~ This substitution3 can involve (1) replacement of one aluminium by one silicon (SM1); (2) replacement of one phosphorus by one silicon (SM2) or (3) replacement of aluminium-phosphorus pairs by two silicons [SM3 Ho (Ho = homogene~us)].~ The substitution of silicon for phosphorus leads to the formation of Brnnsted-acid sites of medium acid strength. Increasing the amount of silicon in the framework of these SAPO materials can lead to high activity in certain acid-catalysed reactions. It is therefore very important to synthesize SAPOs with high silicon content. Additionally, it is highly desirable to control the synthesis so as to aim at SAPO catalysts with silicon content optimized to produce the maximum number of Brnnsted-acid sites of medium strength acidity.Recent papers have appeared on the synthesis and/or characterization of SAPO-55-'2 and a few exist on the incorporation of silicon into the AIPO, framework. Mertens et aL5 studied the incorporation of silicon into a series of SAPO-5 materials with silicon mole fraction, x = 0.01, 0.15, 0.28 and 0.36. These authors suggest silicon substitution by SM2 when x = 0.01 and substitution by combined SM2 and SM3 He (He = heterogeneous) processes when x 3 0.15. It is of interest to know the value of x corresponding to the change in mechanism which occurs when x is increased from 0.01 to 0.15. Moreover, it is important to know whether the build-up of siliceous regions results in composition gradients in the crystals. These questions are addressed in the present work by considering SAPO-5 synthesized to have a silicon mole fraction in the range 0.05-0.17. These materials are characterized using several physical methods and a preliminary catalytic evaluation is made. Simple cluster M O calculations are used t...

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Background This study investigates university students’ digital health literacy and web-based information-seeking behaviours during the early stages of the COVID-19 pandemic in England. It compares undergraduate and postgraduate students in non-health related subjects with health care students, many of whom were preparing for, or working in, frontline roles. The survey was conducted as part of a wider study by the COVID-HL research consortium. Methods A cross-sectional study was conducted among n = 691 university students aged ≥18 years from 25 universities across England using an adapted digital survey developed by COVID-HL. Data were collected regarding sociodemographic characteristics and specific measures drawn from the Future Anxiety Scale and the Digital Health Literacy Instrument (DHLI). These had been adapted for use in an English setting and to the specific context of the COVID-19 pandemic. Other data collected included students’ anxiety or worries about the future using the Dark Future Scale as well as behaviours in online information-seeking. Data were analysed using correlations to test for relationships between constructs and also between group comparisons to test for differences between students studying health and non-health related subjects. Results Across digital health literacy dimensions, there was no significant difference between students studying health-related subjects and other students. Health care students did report greater difficulties in relation to how to behave online. They also relied less on public body sources for information about the pandemic. A significant difference was found between the two student populations in relation to their anxiety about the future with health care students reporting fewer fears about the future. Conclusions Although digital health literacy is well developed in university students, a significant proportion of students still face difficulties with evaluating online information which may frustrate public health efforts. This could be addressed by ensuring health students’ curriculum in particular encompasses digital health literacy.