Marco Martino

Convenient regioselective functionalization at the upper-rim of p-tert-butylcalix[8]arene through a protection–deprotection procedure

Abstract A viable method to obtain calix[8]arenes selectively functionalized at the upper rim of 1,5-aromatic rings is reported. The procedure relies on protected, readily accessible 1,5-xylylene-bridged derivatives, which are easily deprotected by hydrogenolysis. The method allowed the synthesis of the first examples of calix[8]arenes partially substituted with p-nitro, p-amino, quinone and hydroquinone functionalities.

Regioselective intramolecular bridging of p-tert-butylcalix[7]arene

The first examples of doubly bridged calix[7]arenes 2a–h have been obtained by base-promoted O-alkylation of p-tert-butylcalix[7]arene 1 or 1,4-tetramethylene-bridged calix[7]arene 3a with a variety of bis-electrophiles including BrCH2Cl, oligoethylene glycol ditosylates, and 1,2-bis(bromomethyl)benzene. In the presence of Cs2CO3 as the base, in acetone, the syn-1,4:2,3-bis-bridged regioisomer was obtained in yields up to 76%. Assignment of bridging pattern was based on chemical shift of OH groups in conjunction with chemical correlations with known compounds. Stereochemical and conformational features were investigated with the aid of 2D and Dynamic NMR studies and MM3 calculations.

Thermal stability of ammonium salts as compatibilizers in polymer/layered silicate nanocomposites

Abstract Thermal stability of alkyl and arylalkyl quaternary ammonium cation (onium) in starting chloride salt, in organoclay obtained after exchange with montmorillonite (MMT) and after mixing of the organoclay with isoprene rubber was examined using conventional TGA and by mass spectrometry pyrolysis/GC-MS. Degradation was observed to occur at T ≥ 170 °C for organoclays and the main volatile compounds were identified as tertiary amines, chloroalkanes and alkenes. Mechanisms for their formation are proposed and the role of residual onium chloride and basic centers of layered silicate is discussed.

Catalysts for the Intensification of the Water Gas Shift Process

Nowadays the Water Gas Shift process (WGS) is performed in two stages, a first step at high temperature (HTS), carried out at 623–873 K, and a low temperature step (LTS) at 423–573 K, to reach a favorable thermodynamic equilibrium condition. This kind of configuration is expensive and requires complex operative conditions, so to make preferable process intensification. This could be achieved through the development of new structured catalytic formulations, characterized by enhanced thermal transfer properties, able to improve the heat distribution along the catalytic bed. For this purpose the most promising catalytic systems are precious metal based supported on open cells metallic foam carriers. In this paper we report a preliminary study on the preparation and the evaluation of differently-supported Pt-based catalysts, as promising precursors in the preparation of structured catalysts for the process intensification of WGS reaction.

Comparative studies of low temperature water gas shift reaction over platinum based catalysts

Water gas shift reaction (WGS) is normally performed in a two-stage process, a first stage at high temperature (HTS) conventionally carried out at 623 873 K on Fe/Cr-based catalyst, to take advantage from a fast reaction, and a second stage at low temperature (LTS) at 423 573 K on Cu/Zn-based catalysts, to reach a favourable thermodynamic equilibrium condition. A single-stage process involves at the same time a cost reduction in plant setup as well as operative conditions; however at the moment, due to the lack of efficient catalytic systems the one-stage WGS systems is not widely diffused. Noble metals arise today as a promising solution in this direction, so in this work great attention was focused on the preparation and testing of differently-supported Platinum-based catalysts.

Pt-re based catalysts for the realization of a single stage water gas shift process

The excellent performance of the Pt/Re/CeZrO4 catalyst, for the CO Water Gas Shift reaction, is presented. A preliminary comparative study, on the activity of some bimetallic catalysts, Platinum-based (PtM/CeZrO4, M=Re,La,Rh), highlighted the great ability of the Rhenium to enhance the activity and stability of the catalyst, even at very low temperatures. The effect of the preparation method, in terms of sequence of impregnation of the two active metals, was evaluated, showing a low impact on the performance of the final catalyst. The reported results indicate that the Platinum-Rhenium system represent a concrete possibility for the realization of a single stage WGS process.

High Thermal Conductivity Structured Carriers for Catalytic Processes Intensification

Process intensification is conceived as a way to optimize fixed and operating costs in an industrial plant. It is not only related to a reduction of the size of equipments, but also to the change of the production method, by enhancing both chemical that physical aspects of the process. In particular, when there has to deal with exothermic equilibrium reactions, such as the Water Gas Shift, the main problem is that the conversion is limited by the kinetics at the inlet of a catalyst bed, because temperature is low, and is thermodynamically limited at the outlet, because in the adiabatic reactor temperature raises, lowering the equilibrium value. A good solution would be the use of a high conductive carrier, able to redistribute the heat of reaction along the catalyst bed. The aim of this work was to study the heat transfer phenomenon on structured carriers such as open cell foams, by estimating also the thermal properties by a mathematical model elaborated for the heat transfer system.

Supercritical Antisolvent Process to Produce Cerium Oxide Nanoparticles as a Support for High-activity Platinum Catalysts

Cerium acetylacetonate (Ce(acac)3) was precipitated from methanol (MeOH) using supercritical antisolvent process (SAS). The precursor was, then, calcined obtaining the cerium oxide (CeO2). Platinum (Pt) supported on cerium oxide is active for the water gas shift reaction, showing higher activity if compared with platinum supported on other oxides. The catalyst based on platinum supported on cerium oxide obtained using SAS process is more active than the Pt/CeO2 catalyst obtained in a conventional manner. The precursor nanoparticles were precipitated at different pressures and concentrations of the Ce(acac)3/MeOH solution. At the best operating conditions, nanoparticles with a diameter in the range 40-65 nm were obtained. The catalytic activity and the selectivity of two different samples was studied and compared. The catalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, infrared spectroscopy, nitrogen adsorption and desorption at 77 K, and mercury porosimetry.

Methane steam reforming intensification: Experimental and numerical investigations on monolithic catalysts

Methane steam reforming is still the most economical route for hydrogen production. It generates hydrogen for refining processes, food industry, and recently for fuel cell applications. Recent studies focused on the application of structured catalysts in mass transfer limited-reactions indicated that there are potentially several advantages for monolithic reactor as compared to the packed reactors such as, especially in terms of lower pressure drop and better mass and heat transfer performances. So highly thermal conductive honeycomb structures were proposed as catalyst supports to enhance the heat and material transfer properties of the final catalysts. This work focuses on the experimental testing of the methane steam reforming reaction performed on a Ni-loaded SiC monolith packaged into an externally heated tube. In particular, the two flow configurations of Flow Through and Wall Flow were investigated and compared, the effect of a washcoat deposition was evaluated. The experimental tests indicate that the Wall Flow configuration may overcome the fixed-bed reactor problems, yielding a more uniform temperature distribution and more effective mass transport.

State of the Art of Conventional Reactors for Methanol Production

Abstract Because it is involved in the production of a wide range of added-value chemicals, methanol is one of the most important compounds in the industrial chemistry field. The significant thermodynamic limitations related to methanol synthesis via syngas conversion has intensified interest in this process. Starting with the development of the BASF process at the beginning of the 20th century and the ICI process, introduced in the 1960s, many schemes have been proposed for the overall optimization of the process. This chapter aims to explore the methanol synthesis process and the most relevant technologies available in the methanol industry.