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Sammichele di Bari, Italy

Aresta M.,National University of Singapore | Aresta M.,University of Bari | Dibenedetto A.,CIRCC | Dibenedetto A.,University of Bari | And 2 more authors.
Journal of Catalysis

The need to reduce the emission of carbon dioxide into the atmosphere is pushing toward the use of "renewable carbon", so to avoid as much as possible burning "fossil carbon". It would be possible to complement the natural "carbon cycle" by developing man-made industrial processes for "carbon recycling", converting, thus, "spent carbon" as CO2 into "working carbon", as that present in valuable chemicals or fuels. Such practice would fall into the utilization of "renewable carbon", as the man-made process would perfectly mimic the natural process. An order of complexity higher would be represented by the integration of biotechnology and catalysis for an effective CO2 conversion, using selective catalysts such as enzymes, or even whole microorganisms, coupled to chemical technologies for energy supply to enzymes, using perennial sources as sun or wind or geothermal as primary energy.These days all the above approaches are under investigation with an interesting complementarity of public-private investment in research. This paper aimed at making the state of the art in CO2 conversion and giving a perspective on the potential of such technology. Each atom of C we can recycle is an atom of fossil carbon left in the underground for next generations that will not reach the atmosphere today. © 2016 Elsevier Inc. Source

Angelini A.,University of Bari | Dibenedetto A.,University of Bari | Fasciano S.,CIRCC | Aresta M.,National University of Singapore
Catalysis Today

The synthesis of di-n-butyl carbonate has been studied starting from n-butanol and either CO2 or urea. A comparison of the two synthetic routes is reported. Several mixed oxides have been synthesized and tested with the aim of finding a catalyst active in mild conditions (T, t), recoverable and reusable. Different strategies to push the reaction toward the formation of the target product (di-n-butylcarbonate) have been applied and adapted to each case. The pervaporation membrane and chemical water traps are compared as techniques for water elimination and equilibrium shift in the direct carboxylation. Among the tested catalysts, 0.03Nb2O5/CeO2 is the best in the case of the direct carboxylation of butanol, whereas 0.5MgO/ZnO results the best in terms of activity and robustness for the alcoholysis of urea. © 2016 Elsevier B.V. Source

Dibenedetto A.,University of Bari | Dibenedetto A.,CNR Water Research Institute | Aresta M.,CIRCC | Aresta M.,National University of Singapore | And 2 more authors.

We describe a process for the selective conversion of C6-polyols into 5-hydroxymethylfurfural (5-HMF) in biphasic systems of organic carbonate/water (OC/W), with cerium(IV) phosphates as catalysts. Different reaction parameters such as the OC/W ratio, catalyst loading, reaction time, and temperature, were investigated for the dehydration of fructose. Under the best reaction conditions, a yield of 67.7 % with a selectivity of 93.2 % was achieved at 423 K after 6 h of reaction using [(Ce(PO4)1.5(H2O)(H3O)0.5(H2O)0.5)] as the catalyst. A maximum yield of 70 % with the same selectivity was achieved after 12 h. At the end of the reaction, the catalyst was removed by centrifugation, the organic phase was separated from water and evaporated in vacuo (with solvent recovery), and solid 5-HMF was isolated (purity >99 %). The recovery and reuse of the catalyst and the relationship between the structure of the OC and the efficiency of the extraction are discussed. The OC/W system influences the lifetime of the catalysts positively compared to only water. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Aresta M.,National University of Singapore | Dibenedetto A.,CIRCC | Dibenedetto A.,University of Bari | Di Bitonto L.,CIRCC
RSC Advances

Multifunctional monomers based on glycerol carbonate are employed in the chemical industry for the production of polyurethanes and polycarbonates. To avoid the use of toxic phosgene as carboxylating reagent, eco-friendly routes have been developed using alternative agents. In this paper, a series of binary and ternary oxides have been tested as catalysts in the synthesis of diglycerolether dicarbonate (DGDC) and diglycerol tricarbonate (DGTC) using dimethyl carbonate (DMC) and urea as carboxylating agents. The recovery and reuse of the catalysts are discussed. In the best reaction conditions, using mixed oxides La:Ca = 1:1 as catalysts, the yields of DGDC and DGTC were >90 (pure isolated compounds) and 19.9%, respectively. © The Royal Society of Chemistry 2015. Source

Ventura M.,CIRCC | Aresta M.,National University of Singapore | Aresta M.,University of Bath | Dibenedetto A.,CIRCC | Dibenedetto A.,University of Bari

A simple, cheap, and selective catalyst based on copper/cerium oxides is described for the oxidation of 5-(hydroxymethyl)furfural (5-HMF) in water. An almost quantitative conversion (99 %) with excellent (90 %) selectivity towards the formation of 5-formyl-2-furancarboxylic acid, a platform molecule for other high value chemicals, is observed. The catalyst does not require any pretreatment or additives, such as bases, to obtain high yield and selectivity in water as solvent and using oxygen as oxidant. When a physical mixture of the oxides is used, low conversion and selectivity are observed. Air can be used instead of oxygen, but a lower conversion rate is observed if the same overall pressure is used, and the selectivity remains high. The catalyst can be recovered almost quantitatively and reused. Deactivation of the catalyst, observed in repeated runs, is due to the deposition of humins on its surface. Upon calcination the catalyst almost completely recovers its activity and selectivity, proving that the catalyst is robust. Aerobic workout: A mixed oxide of copper and cerium (CuOCeO2) is prepared by a milling method. The catalyst shows high activity towards the selective conversion of 5-(hydroxymethyl)furfural (5-HMF) in water, using O2 as oxidant and without any external additives. Deposition of humins during reaction causes deactivation, but upon calcination the original activity is mostly restored. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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