Cristina Della Pina

A green approach to chemical building blocks. The case of 3-hydroxypropanoic acid

3-Hydroxypropionic acid (3-HP) is considered as a potential building block either for organic synthesis or high performance polymers. However no large scale process is presently available despite many efforts following biological and chemical routes. In this paper we present recent advances in eco-sustainable processes leading to 3-hydroxypropanoic acid highlighting, in particular, the potential of the catalytic chemical methods.

Industrial Applications of Gold Catalysis

Gold catalysis has recently found its first large-scale applications in the chemical industry. This Minireview provides a critical analysis of the success factors and of the main obstacles that had to be overcome on the long way from the discovery to the commercialization of gold catalysts. The insights should be useful to researchers in both academia and industry working on the development of tomorrows gold catalysts to tackle significant environmental and economic issues.

Catalytic performance of gold catalysts in the total oxidation of VOCs

Catalysts for the oxidation of volatile organic compounds (VOCs) were prepared by supporting 1% gold on cerium and zirconium oxides (CeO2, Ce0.5Zr0.5O2, ZrO2) using a simple impregnation method followed by reduction of gold in the presence or absence of ammonia (N). The catalysts were tested in model reactions, namely the total oxidation of benzene, hexane and chlorobenzene, using a micro flow reactor at atmospheric pressure in the temperature range 100–500°C and their activity was compared to that of Au/TiO2 and Au/Fe2O3 reference catalysts supplied by the World Gold Council (WGC). Benefits on the light-off temperatures were observed by adding gold to cerium-containing oxides: 100% conversion of hexane was obtained with Au/Ce0.5Zr0.5O2 at the lowest temperature (300°C). Full conversion of benzene was reached at only 250°C with Au/CeO2 (N), at 290°C with Au/Fe2O3 (WGC) and at 300°C with Au/Ce0.5Zr0.5O2. In the case of chlorobenzene oxidation, the addition of gold was of even greater relevance because of a drop in the light-off temperature of over 100°C for Au/Ce0.5Zr0.5O2 and Au/CeO2, with respect to the gold-free oxide supports; but in this case rapid deactivation took place.

Gold-catalyzed oxidation in organic synthesis: a promise kept

An overview of Prof. Michele Rossis recent research and related scientific context is presented, dealing with liquid and gas phase oxidation of some organic compounds by gold catalysis. The application of mono- and bimetallic gold nanoparticles as an aid for organic synthesis has been mainly devoted to the aerobic oxidation of alcohols and aldehydes, as well as to the new synthesis of conducting polymers, thus demonstrating the superior performance of gold in terms of activity, selectivity and durability in comparison with traditional Pd and Pt catalysts. Starting from the observation that oxygen activation towards organic compounds occurs mainly in the presence of nanometric gold clusters, the outstanding properties of colloidal “naked” particles are also discussed. Thorough kinetic studies suggest models for interpreting the aerobic oxidation of glucose, thereby shedding light on the molecular mechanism, whilst the perspective for industrial applications of supported gold catalysts shows how the “yellow metal” is more than a promise.

Oxidation of Allyl Alcohol in the Presence of a Gold Catalyst: A Route to 3-Hydroxypropionic Acid

A careful approach to the use of natural resources suggests that the renewable feedstocks chosen for industrial transformations should be derived from the biological cycle. Accordingly, a biorefining industry should support the petrochemical industry by developing a set of versatile chemicals such as 2hydroxypropionic acid (lactic acid) and butanedioic acid (succinic acid), which are advantageously produced by fermentation. Moreover, the importance of 3-hydroxypropionic acid as a new building block has been outlined. At the present time, 3-hydroxypropionic acid is a rare and costly chemical which is commercialized as an aqueous solution by only a few suppliers. For its preparation, besides traditional stoichiometric reactions, also catalytic methods have been reported mainly in the patent literature. Thus, Henkel claims a process for the preparation of 3-hydroxypropionic acid salts by oxidation of 1,3-propanediol in alkaline solution using oxygen in the presence of a palladium catalyst. Note that a convenient synthesis of 1,3propanediol has been itself a worldwide important challenge up to the recent industrial application. More interestingly, 3-hydroxypropionic acid has been prepared by the hydration of acrylic acid in the presence of a solid catalyst. Biological oxidation of polyols and sugars through genetically modified bacteria seems to be a winning route, and Cargill has proposed this derivate as a new platform intermediate to be produced from glucose. However, despite all the efforts, none of the proposed new processes is effectively operating to our knowledge. Herein, we describe a new, unexplored route to 3-hydroxypropionic acid based on the aerobic oxidation of allyl alcohol. Allyl alcohol (2-propene1-ol) is a large-scale chemical (over 50 000 tons per year production) derived from the petrochemical industry via propene and propene oxide as intermediates. Gold catalysis is a powerful tool for the aerobic oxidation of many hydroxylated molecules, in particular alcohols, under mild conditions. Therefore, the favorable transformation of allyl alcohol to 3-hydroxypropionic acid with a gold catalyst was explored. Upon reacting allyl alcohol in aqueous alkali solutions, a slow oxidation takes place which produces 3-hydroxypropionate besides acrylate and glycerate. The oxidation could be controlled by varying the amount of alkali used and the temperature as reported in Table 1. A high selectivity at full conversion to the desired 3-hydroxypropionic acid can be obtained by using an excess of NaOH (3:1) and a mild temperature (50 8C). The products were identified and quantified by comparison with authentic samples by using HPLC, H NMR and C NMR spectroscopy, and H-H COSY and H-C HMQC techniques. Analytical data were reproducible within a 3 % deviation. To compare the homemade 0.3 % Au/C catalyst with the reference 1.5 % Au/TiO2 catalyst provided by World Gold Council, further experiments were carried out with the latter catalyst under the same conditions (Table 2). The reference Au/TiO2 catalyst is less effective and less selective in converting allyl alcohol, with the highest yield of 3-hydroxypropionic acid obtained being only 53 %, much lower than the 79 % yield obtained with our Au/C catalyst.

Investigation of glycerol polymerization in the clinker grinding process

Concrete production is a large scale process that involves high energy consumption. In order to increase the sustainability of this process, the reduction of energy input is necessary. Bio-glycerol was demonstrated to be a highly efficient renewable-based additive in the grinding process for concrete production and helped reduce energy costs and improve the quality of the resulting product. In order to understand its excellent aiding properties, the interaction of glycerol with cement clinkers was investigated; both chemical and physical interactions were taken into account. The results of this investigation points to surface tension modification of the clinker particles as one of the main effects of bio-glycerol addition during the grinding process.

Catalytic Transformation of Ethanol with Silicalite-1: Influence of Pretreatments and Conditions on Activity and Selectivity

Silicalite‐1 undergoes a reversible cycle of acid activation and base deactivation when employed as a catalyst for the vapor‐phase dehydration of ethanol at 230–300 °C. In particular, a pretreatment with aqueous HCl strongly promotes the production of diethyl ether at lower temperatures (230–270 °C) or ethene at higher temperature (300 °C). The activated catalyst becomes completely inactive upon addition of aqueous potassium acetate, whereas the catalytic effect is restored by repeating the acid treatment. Moreover, the reversible exchange of H+ with K+, introduced as KCl salt, in HCl‐activated silicalite causes the suppression of the catalytic activity. Several analytical techniques, as the acidic sites characterization, surface area‐porosity determination and electron microscopy images were unable to display surface modifications responsible for the important catalytic effect induced by HCl treatment. It is proposed that HCl treatment allows the formation of protonated and neutral chemical groups, such as SiOSi surface bridges, behaving as active sites for ethanol dehydration. On the surface of the catalyst, K+ competes with H+ and strongly inhibits alcohol dehydration.

Gold Nanomaterials: From Preparation to Pharmaceutical Design and Application.

The present mini review offers a brief overview on the preparation and modification of gold nanomaterials (AuNMs) designed for biomedical applications, including biosensors, bioimaging, phototherapy and importantly gene/drug delivery. As biocompatibility is a prerequisite for safe pharmaceutical application, the potential risk of AuNMs to biological systems is also assessed.

Gold catalysis in organic synthesis and material science

One of the most exciting and unforeseen developments of the chemical research has been the recent application of gold in catalysis. In fact, this metal has become an important tool in organic synthesis several years after the first reports on ethyne hydrochlorination and CO oxidation and now it is w...

Towards “Green” Smart Materials for Force and Strain Sensors: The Case of Polyaniline

Stress/strain sensors constitute a class of devices with a global ever-growing market thanks to their use in many fields of modern life. As an alternative to the traditional compounds, that exhibit low inherent resistivity and limited flexibility, in the present work we will show the advantages to employ a smart material, polyaniline (PANI), prepared by an innovative green route, for force/strain sensor applications, wherein simple processing, environmental friendliness and sensitivity are particularly required.