Notícias

• Seminário

Título: “Catalysts for a sustainable chemistry”.
Dr. Rhett Kempe, Anorganische Chemie II – Catalyst Design, Universität Bayreuth, Germany.

Dia: 27 de fevereiro
Horário: 10h30
Auditório "Inés Joekes", Instituto de Química - Unicamp

Abstract: Dwindling reserves of crude oil and the resulting price increase of this and other fossil carbon sources combined with environmental concerns have resulted in a call for the use of alternative, preferably renewable, resources. Aside from fuel, ultimately a wide variety of chemical feedstocks are derived from fossil sources. Renewable lignocellulosic materials are indigestible and therefore not useful as food products and can be processed to give alcohols and polyols. These rather highly oxidized hydrocarbons differ drastically in their chemical nature from the cracking products of crude oil. Thus, there is a high demand for new reactions that utilize alcohols and convert them into key chemicals.[1] Recently, our group introduced the concept of acceptorless dehydrogenative condensations (ADC) for the catalytic synthesis of N-aromatic compounds like pyrroles and pyridines.[1] In such ADC reactions differently substituted alcohols become selectively connected via C-C and C-N bond formation steps. The deoxygenation of alcohols takes place via condensation steps and the aromatization via dehydrogenation steps. In the talk, the development of ADC reactions and the design of catalyst systems that mediate these reactions are discussed.
[1] a) S. Michlik, R. Kempe Nature Chem. 2013, 5, 140.

Docente responsável: Daniela Zanchet

• Seminário

Título: "Synthesis of Dimethyl Ether by Zeolitic Catalysts".
Dr. Girolamo Giordano, University of Calabria, Italy.

Abstract: The effect of zeolite topology over the performance in the methanol-to-DME (dimethylether) reaction was investigated. Three different zeolites structure with different channel system (3D, 2D, 1D) and size, were compared in terms of catalytic activity and duration over time-on-stream. Catalytic tests revealed that large pore structures (either 1-D or 3-D) resulted on a very reactive catalyst at moderate temperatures showing a significant drop in conversion above 220°C. Time-on-stream tests performed on mordenite, MOR, and beta, BEA, revealed that the absence of interconnections (MOR) increases the deactivation rate (in terms on reactant conversion) even though the selectivity toward dimethylether remains close to one. On the contrary, in presence of 3-D structure (BEA) the deactivation process is slowed down but a wider range of products (from olefins to gasoline cut) is observed and their presence could be correlated to the different samples acidity and to the effect of interconnection more than to the channel size (the same in MOR and BEA).

Docente responsável: Heloise de Oliveira Pastore.  

• Seminário

Título: “Hydrothermal synthesis of Ti(III)AlPO-5 materials and their catalytic performance in the selective oxidation of olefins”.
Dr. Joaquín Pérez-Pariente, Instituto de Catálisis y Petroleoquímica, CSIC, Spain.

​Data: 04 de março.
Horário: 15h00
Local: Auditório "Inés Joekes", IQ. 

Summary: The ability of Ti-substituted molecular sieves to catalyze the selective oxidation of organic compounds in liquid phase under mild conditions is very much dependent upon the chemical environment of the Ti centers. In contrast with the good performance exhibited by Ti-containing silicon-based materials as zeolites and ordered mesoporous solids, that of Ti-subsituted AlPO4 microporous materials is  rather poor. By analyzing the main differences existing between Ti-zeolites and TAPOs regarding their physicochemical properties, we have designed a new synthesis route toward active and selective TAPO catalysts which involves the incorporation in the framework of Ti ions in low oxidation state, namely Ti(III), instead of Ti(IV) used to prepared conventional TAPOs materials. Several physicochemical techniques used to characterize the Ti(III)-containing materials prepared by hydrothermal synthesis shows that the Ti(III) cations have been indeed incorporated in the framework by isomorphous substitution. Under appropriate conditions, the activity of these TAPO catalysts is quite close to that of zeolites, but it has been found that the allylic oxidation of cyclohexene is strongly promoted, in contrast with the double-bond epoxidation pathway commonly observed for Ti-zeolites.
 
Docente responsável: Heloise de Oliveira Pastore