Supporting Cubane’s Renaissance: Metathesis reactions on 4-iodo-1-vinylcubane and Stetter reaction on 1-iodocubane-4-carboxaldehyde

Cubane is a peculiar cube-shaped alkane molecule with a rigid, regular structure. This makes it a good scaffold, i.e. a molecular platform to which the substituents are arranged in a specific and fixed orientation. Moreover, cubane has a body diagonal of 2.72 Å, very similar to the distance across the benzene ring, i.e. 2.79 Å. Thus, it would be possible to use cubane as a scaffold in medicinal and material chemistry as a benzene isostere 1,2. This could lead to advantages in terms of solubility and toxicity and could provide novel properties. For this purpose, the possibility of performing “modern organic chemistry” on the cubane scaffold has to be studied. This project was entirely carried out in the framework of the Erasmus+ mobility programme at the Trinity College (Dublin, IRL) under the supervision of prof. M. O. Senge. The main goal of this project was to widen the knowledge on cubane chemistry. In particular, it was decided to test reactions that were never applied to the scaffold before, such as metathesis of 4-iodo-1-vinylcubane and Stetter reaction of 1-iodocubane-4-carboxaldehyde. These two molecules were synthesized in 10 and 9 steps respectively from commercially available cyclopentanone, following a known procedure. Unfortunately, metathesis with different olefins, such as styrene, α,β unsaturated compounds and linear α-olefins failed under different conditions, highlighting cubane behaves as a Type IV, challenging olefin under metathesis conditions. Even the employment of a specific catalyst for hindered olefins failed in the cross-coupling with linear α-olefins. On the other hand, two new molecules were synthesized via Stetter reaction and benzoin condensation respectively. Even if the majority of the reactions were not successful, this work can be seen as an inspiration for further investigation on cubane chemistry, as new questions were raised and new opportunities were envisioned

Layered-double hydroxides and derived oxide as CRM-free highly active catalysts for the reduction of 4-nitrophenol

The present study investigates the possibility to abate 4-nitrophenol (4NP), a well-known persistent contaminant in wastewaters, using Layered-Double Hydroxides (LDH) based catalysts, non-noble metals-based and Critical Raw Materials-free materials used for 4NP reduction with NaBH4. It is reported the study of the effects of several parameters on the overall reaction kinetic by in situ monitoring of the 4NP reduction through UV-Vis Spec-troscopy, as: (i) LDH's trivalent and divalent cation nature, (ii) LDH thermal treatment, (iii) substrate/catalyst ratio, and (iv) stirring rate. The reasons that led to increased activity were identified and correlated with cat-alyst's structure characterization. The results pointed out that LDH enhance synergic effect of nickel and copper by increasing reducibility which is further raised when defective mixed oxide by calcination is obtained. This resulted in enhanced 4NP reduction which could be further increased by calcination providing a highly reducible mixed oxide

H2 Production by Methane Oxy-Reforming: Effect of Catalyst Pretreatment on the Properties and Activity of Rh-Ce0.5Zr0.5O2 Synthetized by Microemulsion

Green hydrogen introduction in hard-to-abate processes is held back by the cost of substituting steam reforming plants with electrolyzers. However, green hydrogen can be integrated in properly modified reforming processes. The process proposed here involves the substitution of steam reforming with oxy-reforming, which is the coupling of the former with catalytic partial oxidation (CPO), exploiting the pure oxygen coproduced during electrolysis to feed CPO, which allows for better heat exchange thanks to its exothermic nature. With the aim of developing tailored catalysts for the oxy-reforming process, Ce0.5Zr0.5O2 was synthetized by microemulsion and impregnated with Rh. The Ce-based supports were calcined at different temperatures (750 and 900 degrees C) and the catalysts were reduced at 750 degrees C or 500 degrees C. Tuning the calcination temperature allowed for an increase in the support surface area, resulting in well-dispersed Rh species that provided a high reducibility for both the metal active phase and the Ce-based support. This allowed for an increase in methane conversion under different conditions of contact time and pressure and the outperformance of the other catalysts. The higher activity was related to well-dispersed Rh species interacting with the support that provided a high concentration of surface OH* on the Ce-based support and increased methane dissociation. This anticipated the occurrence and the extent of steam reforming over the catalytic bed, producing a smoother thermal profile

Evaluation of the Catalytic Activity of Metal Phosphates and Related Oxides in the Ketonization of Propionic Acid

In recent years, the upgrading of lignocellulose bio-oils from fast-pyrolysis by means of ketonization has emerged as a frontier research domain to produce a new generation of biofuels. Propionic acid (PA) ketonization is extensively investigated as a model reaction over metal oxides, but the activity of other materials, such as metal phosphates, is mostly unknown. Therefore, PA ketonization was preliminarily investigated in the gas phase over both phosphates and oxides of Al, Zr, and La. Their catalytic activity was correlated to the physicochemical properties of the materials characterized by means of XRD, XRF, BET N2 porosimetry, and CO2- and NH3-TPD. Noteworthy, monoclinic ZrO2 proved to be the most promising candidate for the target reaction, leading to a 3-pentanone productivity as high as 5.6 h 121 in the optimized conditions. This value is higher than most of those reported for the same reaction in both the academic and patent literature

Hydrogen from Renewables: A Case Study of Glycerol Reforming

Biomass is an interesting candidate raw material for the production of renewable hydrogen. The conversion of biomass into hydrogen can be achieved by several processes. In particular, this short review focuses on the recent advances in glycerol reforming to hydrogen, highlighting the development of new and active catalysts, the optimization of reaction conditions, and the use of non-innocent supports as advanced materials for supported catalysts. Different processes for hydrogen production from glycerol, especially aqueous phase reforming (APR) and steam reforming (SR), are described in brief. Thermodynamic analyses, which enable comparison with experimental studies, are also considered. In addition, research advances in terms of life cycle perspective applied to support R&D activities in the synthesis of renewable H2 from biomass are presented. Lastly, also featured is an evaluation of the studies published, as evidence of the increased interest of both academic research and the industrial community in biomass conversion to energy sources

Highly Active Catalysts Based on the Rh4(CO)12 Cluster Supported on Ce0.5Zr0.5 and Zr Oxides for Low-Temperature Methane Steam Reforming

Syngas and Hydrogen productions from methane are industrially carried out at high temperatures (900 °C). Nevertheless, low-temperature steam reforming can be an alternative for small-scale plants. In these conditions, the process can also be coupled with systems that increase the overall efficiency such as hydrogen purification with membranes, microreactors or enhanced reforming with CO2 capture. However, at low temperature, in order to get conversion values close to the equilibrium ones, very active catalysts are needed. For this purpose, the Rh4(CO)12 cluster was synthetized and deposited over Ce0.5Zr0.5O2 and ZrO2 supports, prepared by microemulsion, and tested in low-temperature steam methane reforming reactions under different conditions. The catalysts were active at 750 °C at low Rh loadings (0.05%) and outperformed an analogous Rh-impregnated catalyst. At higher Rh concentrations (0.6%), the Rh cluster deposited on Ce0.5Zr0.5 oxide reached conversions close to the equilibrium values and good stability over long reaction time, demonstrating that active phases derived from Rh carbonyl clusters can be used to catalyze steam reforming reactions. Conversely, the same catalyst suffered from a fast deactivation at 500 °C, likely related to the oxidation of the Rh phase due to the oxygen-mobility properties of Ce. Indeed, at 500 °C the Rh-based ZrO2-supported catalyst was able to provide stable results with higher conversions. The effects of different pretreatments were also investigated: at 500 °C, the catalysts subjected to thermal treatment, both under N2 and H2, proved to be more active than those without the H2 treatment. In general, this work highlights the possibility of using Rh carbonyl-cluster-derived supported catalysts in methane reforming reactions and, at low temperature, it showed deactivation phenomena related to the presence of reducible supports

Hydrogen production by enhanced methane reforming with membrane reactors or with CO2 capture materials

Pure hydrogen production from methane is a multi-step process run on a large scale for economic reasons. However, hydrogen can be produced in a one-pot continuous process for small scale applications, namely Low Temperature Steam Reforming. Here, Steam Reforming is carried out in a reactor whose walls are composed by a membrane selective toward hydrogen. Pd is the most used membrane material due to its high permeability and selectivity. However, Pd deteriorates at temperatures higher than 500°C, thus the operative temperature of the reaction has to be lowered. However, the employment of a membrane reactor may allow to give high yields thanks to hydrogen removal, which shifts the reaction toward the products. Moreover, pure hydrogen is produced. This work is concentrated on the synthesis of a catalytic system and the investigation of its performances in different processes, namely oxy-reforming, steam reforming and water gas shift, to find appropriate conditions for hydrogen production in a catalytic membrane reactor. The catalyst supports were CeZr and Zr oxides synthesized by microemulsion, impregnated with different noble metals. Pt, Rh and PtRh based catalysts were tested in the oxy reforming process at 500°C, where Rh on CeZr gave the most interesting results. On the opposite, the best performances in low temperature steam reforming were obtained with Rh impregnated on Zr oxide. This catalyst was selected to perform low temperature steam reforming in a Pd membrane reactor. The hydrogen removal given by the membrane allowed to increase the methane conversion over the equilibrium of a classical fixed bed reactor thanks to an equilibrium shift effect. High hydrogen production and recoveries were also obtained, and no other compound permeated through the membrane which proved to be hydrogen selective

Membrane Processes for Pure Hydrogen Production from Biomass

This chapter aims to give an outlook on recent results concerning membranes for pure hydrogen separation, their combination with biomass processes for hydrogen production, and membrane reactors. Since hydrogen is emerging as a valuable chemical for fuel and chemical applications, membrane separation will play a critical role in its pure production. The description starts by considering the classical methane process and its extension to biogas, BioSNG and bioethanol, with a focus on the integration of membranes in processes that involve biomass feedstocks, e.g., gasification and aqueous phase reforming. A membrane catalytic reactor configuration is mainly treated to provide further advantages of higher conversions and yields owing to the hydrogen removal provided by the membrane. Some processes related to biofuel and wastewater are also described to evidence further applications. Finally, the possibilities of downsizing such processes and using modular micro-membrane reactors as an emerging technology for hydrogen production are discussed

La storia a portata di mano per ri-costruire la memoria di una comunità/History at your doorstep acknowledging the legacy of a community.

Gavardo è una cittadina situata a est di Brescia in cui i segni naturali e antropici parlano anche di una storia non sempre benevola. La ricerca ha inizialmente identificato le procedure per fornire in maniera facilmente accessibile, ad un vasto numero di utenti, un database progressivamente implementabile in modalità open source, con lo scopo di raccogliere, organizzare, georeferenziare e comunicare comparativamente la totalità di dati eterogenei legati al patrimonio culturale ed architettonico del caso-studio. Un successivo sviluppo prevede una videoricostruzione tridimensionale di una porzione del tessuto urbano storico del paese, andato perduto durante un tragico bombardamento aereo sul finire della seconda guerra mondiale. Questa attività permette di ricostruire virtualmente edifici e spazi urbani scomparsi da decenni, facendo rivivere in chi è rimasto la memoria di persone e di una storia solo apparentemente dimenticata. Il metodo informativo proposto nella ricerca si dimostra quindi sempre più uno strumento efficace nel preservare e trasmettere la memoria di un determinato luogo, non solo per la conoscenza dell’esistente, ma anche per la ricostruzione virtuale di spazi perduti e di aspetti sociali che sembrano non esistere più, ma che possono ancora avere un ruolo di guida nelle scelte future del disegno dei luoghi. Gavardo is a town located east of Brescia where natural and anthropic signs also tell of a history that has not been always benevolent.The research initially identified the procedures to provide a vastly implementable database, easily accessible to a large number of users, with the aim of collecting, organi- zing, geo-referencing and comparatively communicating the totality of heterogeneous data related to the cultural and architectural aspects of the Gavardo case study. A subsequent development involves a three-dimensional video reconstruction of a portion of the historic urban framework of the town, which was lost during a tragic aerial bombing at the end of the Second World War.This activity allows to virtually re-construct buildings and urban spaces that have disappeared for decades, reviving in tho- se who have remained the memory of people and of a history only apparently forgotten. The informative method proposed in the research is therefore increasingly proven to be an effective tool in preserving and transmitting the memory of a certain place, not only for the knowledge of the existing, but also for the virtual re-construction of lost spaces and social aspects that seem to no longer exist, but which can still play a leading role in the future choices of the design of the places

A VIRTUAL ARCHIVE TO UNDERSTAND AND COMMUNICATE PLACES' COMPLEXITY

Gavardo, a small town located east of Brescia, is dense of natural and anthropic signs: a stratified place with different historical layers. The research aims to identify procedures to provide a progressively open source implementable database to collect, organize, georeference and communicate comparatively the totality of heterogeneous data. Anyone who needs to find and to interface documents, both each other and with the evolutive dynamics of the territory or with its cultural heritage, can easily access. Due to the digital transformation the data set, gathered through a research of material-immaterial sources and by virtual-direct surveys, can be now simultaneously available in single spaces: virtual archives. The most meaningful consequences of these tools are accessibility, dissemination and development of cultural heritage for all: the encyclopedic character that apparently could be assumed is surely overcome by the several connections and the multiple possible cross-references