Cristina Lavorato

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.

Preparation of graphene quantum dots from pyrolyzed alginate.

Pyrolysis at 900 °C under an inert atmosphere of alginate, a natural widely available biopolymer, renders a graphitic carbon that upon ablation by exposure to a pulsed 532 nm laser (7 ns, 50 mJ pulse(-1)) in acetonitrile, water, and other solvents leads to the formation of multilayer graphitic quantum dots. The dimensions and the number of layers of these graphitic nanoparticles decrease along the number of laser pulses from 100 to 10 nm average and from multiple layers to few layers graphene (1-1.5 nm thickness), respectively, leading to graphene quantum dots (GQDs). Accordingly, the emission intensity of these GQDs increases appearing at about 500 nm in the visible region along the reduction of the particle size. Transient absorption spectroscopy has allowed detection of a transient signal decaying in the microsecond time scale that has been attributed to the charge separation state.

Review On Reduction And Partial Oxidation of Organics In Photocatalytic (Membrane) Reactors

Traditional processes for making chemicals are unsustainable in terms of resources and environmental impact. The present pa- per is a review of the most recent advances in the application of selective photocatalytic reactions to organic synthesis, which, in the last years, has attracted the interest of the scientific community addressing on development of environmentally benign synthetic processes. Indeed, selective photocatalysis is operated at ambient temperature and pressure, needs no complex equipments, does not use dangerous chemical reagents and solvents, does not release harmful wastes into the environment and can utilize solar light. Reactions discussed in this paper, as a green approach for valuable fine chemical synthesis, are: i) photocatalytic hydrogenation and/or transfer hydrogenation of ketones and nitrocompounds by using both UV and visible light; ii) photocatalytic hydrogenation and selective partial hydrogenation of unsaturated compounds; iii) selective partial oxidation of alkanes, alkenes, alcohols, aliphatic acids, benzene and other aromatic com- pounds by using both UV and visible light. Use of Photocatalytic Membrane Reactors (PMRs) in reductions (e.g. CO2 to fuels) and in se- lective partial oxidations (e.g. benzene to phenol) is reported, evidencing that opening up of a new avenue is expected in organic synthe- ses, thanks to the synergy of heterogeneous photocatalysis and membrane processes. Nevertheless, these studies are still at nascent stady and much work is needed before taking advantage of PMRs potentiality at industrial level in this interdisciplinary area.

Preparation of Pd-Loaded Hierarchical FAU Membranes and Testing in Acetophenone Hydrogenation

Pd-loaded hierarchical FAU (Pd-FAU) membranes, containing an intrinsic secondary non-zeolitic (meso)porosity, were prepared and tested in the catalytic transfer hydrogenation of acetophenone (AP) to produce phenylethanol (PE), an industrially relevant product. The best operating conditions were preliminarily identified by testing different solvents and organic hydrogen donors in a batch hydrogenation process where micron-sized FAU seeds were employed as catalyst support. Water as solvent and formic acid as hydrogen source resulted to be the best choice in terms of conversion for the catalytic hydrogenation of AP, providing the basis for the design of a green and sustainable process. The best experimental conditions were selected and applied to the Pd-loaded FAU membrane finding enhanced catalytic performance such as a five-fold higher productivity than with the unsupported Pd-FAU crystals (11.0 vs. 2.2 mgproduct gcat−1·h−1). The catalytic performance of the membrane on the alumina support was also tested in a tangential flow system obtaining a productivity higher than that of the batch system (22.0 vs. 11.0 mgproduct gcat−1·h−1).

Photocatalytic hydrogenation of organic compounds in membrane reactors

Photocatalytic reduction represents an alternative to conventional catalytic hydrogenation, and it appears a more sustainable method to synthesize organic compounds under mild conditions in the presence of suitable photocatalysts. The present chapter first reviews the basic principles of photocatalysis and of membrane photoreactors as membrane and membrane materials. The chapter then discusses photocatalytic hydrogenation of organic compounds with a wide overview on the recent progress in this field, the latest developments of semiconductors, and some possible application in photocatalytic membrane reactors.