Marta Puche

High silica zeolites with three-dimensional systems of large pore channels

Abstract Several high silica zeolites with three-dimensional systems of large pore channels have been prepared in aqueous fluoride media: Beta, ITQ-7, ITQ-10 and ITQ-14. Pure silica beta can crystallize using up to 17 organic cations considerably different in size, shape, rigidity and C/N ratios. There are clear differences in the powder X-ray diffraction patterns of calcined beta materials prepared with different cations, suggesting structural differences between them. However, this technique cannot be readily used to get further insights into these differences. 19 F MAS NMR spectroscopy shows the existence of fluoride occluded in double four ring cages in most of the different betas, thus demonstrating for the first time the real occurrence in these intergrown materials of polymorphs different from A and B. Double four ring cages are also present in ITQ-7 and in the new ITQ-10 and ITQ-14 zeolites.

ITQ-12: a new microporous silica polymorph potentially useful for light hydrocarbon separationsElectronic supplementary information (ESI) available: details of the structure solution, Rietveld refinements in space groups C2/m and Cm and energy minimisation calculations in C2/m, Cm and C2. See http://www.rsc.org/suppdata/cc/b3/b306440a/

The new synthetic form of microporous crystalline silica, denoted as ITQ-12, shows a high potential for the separation of propane and propene from its mixtures.

Copper‐ and Vanadium‐Catalyzed Oxidative Cleavage of Lignin using Dioxygen

Transition-metal-containing hydrotalcites (HTc) and V(acac)3 /Cu(NO3 )2 ⋅3 H2 O (acac=acetylacetonate) mixtures were tested for their catalytic activity in the cleavage of the lignin model compound erythro-1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-l,3-propanediol (1) with molecular oxygen as oxidant. Both catalytic systems displayed high activity and good selectivity and afforded veratric acid as the main product. The catalyst behavior was studied by EPR spectroscopy, XRD, and Raman spectroscopy. After the catalysts were established for the model system, lignin depolymerization studies were performed with various organsolv and kraft lignin sources. The oxidative depolymerization and lignin bond cleavage were monitored by gel permeation chromatography (GPC), MALDI MS, and 2D-NMR (HSQC). Irrespective of the lignin pretreatment, both HTc-Cu-V and V(acac)3 /Cu(NO3 )2 ⋅3 H2 O were able to cleave the β-O-4 linkages and the resinol structures to form dimeric and trimeric products.

Visible-light photocatalytic hydrogen generation by using dye-sensitized graphene oxide as a photocatalyst

Dye-sensitized graphene oxide is able to generate hydrogen from water/methanol mixtures (80:20) by using visible or solar light. The most efficient photocatalyst tested contained a tris(2,2-bipyridyl) ruthenium(II) complex incorporated in the interlayer spaces of a few layers of graphene oxide with a moderate degree of oxidation. The graphene oxide-based photocatalyst does not contain noble metals and we have determined that it is two orders of magnitude more active than catalysts based on conventional titania.

Graphene Oxide as Catalyst for the Acetalization of Aldehydes at Room Temperature

Graphene oxide obtained through the standard Hummers oxidation of graphite and subsequent exfoliation promotes acetalization of aldehydes in methanol. It is a highly efficient reusable heterogeneous catalyst because of its advantages of absence of transition metals, sustainable resources, and high activity, large surface area, and accessibility of active sites. Analytical and spectroscopic data suggest that the sulfate groups introduced spontaneously during Hummers oxidation are the sites responsible for catalysis.