Both chemical looping processes and oxygen permeable ceramic membranes require gas-solid surface reaction to occur in order to function; the two approaches have much in common at a fundamental level. Both approaches, through either dynamic operation in the case of looping or membrane operation, allow a degree of process intensification through simultaneous reaction and separation. Here the use of chemical looping and oxygen permeable ceramic membranes for hydrogen production is reviewed. Hydrogen production from water with various reducing gases is covered, as is synthesis gas production from hydrocarbons with various oxidants (this requiring 10 further hydrogen separation from the synthesis gas). The two approaches are compared and contrasted.

Adsorption of 13CH3OH, CH3OD, CD3OH, and CD3OD on well characterized H-ZSM-5, H-M, H-SAPO-5, FAU type H-Y, and EMT type H-Y microporous materials at various coverages has been studied by using 1H and 13C MASNMR. At low methanol coverages the more acidic molecular sieves are able to protonate methanol molecules producing adsorbed methoxonium ions. In less acidic materials hydrogen bonding occurs involving the Brønsted acid site. As the coverage increases methanol clusters form and the bonding within these clusters weakens as demonstrated by the 1H MASNMR chemical shift trends. This bond weakening gives rise to an increase in mobility of methanol molecules adsorbed within H-ZSM-5 channels and is confirmed by 2H static wide-line spectra of CH3OD adsorbed on D-ZSM-5.

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The synthesis and structural characterization of synthetic analogues of the microporous zirconium silicate minerals petarasite (AV-3), gaidonnayite (AV-4), and umbite (AM-2) are reported. AM-2 materials have been synthesized with different levels of titanium substitution (Zr/Ti molar ratios of ∞,1.9, 0.5, and 0) indicating the existence of a continuous solid solution. All materials have been characterized by several techniques, viz., SEM, powder XRD, single- and triple-quantum 23Na and 29Si MAS NMR, water adsorption measurements, and TGA analysis. As a common structural feature, all these solids possess corner-sharing [ZrO6] octahedra and [SiO4] tetrahedra forming a three-dimensional framework. Unlike framework microporous titanosilicates where Ti−O−Ti−O chains are usually present, petarasite, gaidonnayite, umbite, and their synthetic analogues display structures where the [ZrO6] octahedra are isolated from each other by [SiO4] tetrahedra and, hence, Zr−O−Zr−O chains do not occur. All these materials are thermally stable up to, at least, 550 °C. The hydration−dehydration processes seem to be reversible.

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