Study of new Catalysts for the Selective Oxidation of n-Butane to Maleic Anhydride: The Role of Catalysts Thermal Treatment

Maleic anhydride (MA) is a very versatile molecule, indeed, with three functional groups (two carbonyl groups and one double bond C=C) it is an excellent joining and cross-linking material. It is obtained via selective oxidation of n-butane, using vanadyl pyrophosphate as a catalyst. The catalytic system has been largely studied over the years and it is normally used in the industrial production of MA, but the main open problem is to completely control its preparation. This thesis reports the effect of different preparation parameters employed during the calcination procedure for the transformation of precursor into the active catalyst. The thermal treatment is already known to be favoured in the presence of water, hence the first study was on the role of different amount of water co-fed with air, leading to obtain catalysts with an higher crystallinity. This is not the only parameter to control: the molar ratio of oxygen has also an important role, to obtain an active and selective catalyst. Some tests decreasing the “oxidizing power” of the mixture were carried out and it was observed a progressive development of VPP phase instead of oxidized V/P/O systems. Established the role of water and oxygen, the optimal conditions have been found when a mixture composed of air, water and nitrogen was used for the calcination, in the molar ratio of 30:10:60% respectively. Also at the lower temperature tested, i.e. 400°C, the catalyst presents the higher conversion of n-butane and MA yield compared to all other samples. The important conclusion we have reached is that not higher amount of water is necessary to obtain the most performing catalyst, thus leading to economic savings. Performing the same experiments on two different precursors, give catalysts with different activity but the mixture previously descripted is always the one that leads to the best performance.

Study of the absorption of organic compounds on biopolymers

This work has been conducted in order to determine the solubility and diffusion coefficients of different aromatic substances in two different grades of polylactic acid (PLA), Amorphous (PDLLA) and Crystalline (PLLA); in particular the focus is on the following terpenes: Linalool, α-Pinene, β-Citronellol and L-Linalool. Moreover, further analyses have been carried out with the aim to verify if the use of neat crystalline PLA, (PLLA), a chiral substrate, may lead to an enantioenrichment of absorbed species in order to use it as membrane in enantioselective processes. The other possible applications of PLA, which has aroused interest in carry out the above-mentioned work, concerns its use in food packaging. Therefore, it is interesting and also very important, to evaluate the barrier properties of PLA, focusing in particular on the transport and absorption of terpenes, by the packaging and, hence, by the PLA. PLA films/slabs of one-millimeter thickness and with square shape, were prepared through the Injection Molding process. On the resulting PLA films heat pretreatment processes of normalizing were then performed to enhance the properties of the material. In order to evaluate solubility and diffusion coefficient of the different penetrating species, the absorption kinetics of various terpenes, in the two different types of PLA, were determined by gravimetric methods. Subsequently, the absorbed liquid was extracted with methanol (MeOH), non- solvent for PLA, and the extract analyzed by the use of High Performance Liquid Chromatography (HPLC), in order to evaluate its possible enantiomeric excess. Moreover, PLA films used were subjected to differential scanning calorimetry (DSC) which allowed to measure the glass transition temperature (Tg) and to determine the degree of crystallinity of the polymer (Xc).

Biopolyester fibers for sustainable and biocompatible applications

The rising of concerns around the scarcity of non-renewable resources has raised curiosity around new frontiers in the polymer science field. Biopolymers is a general term describing different kind of polymers that are linked with the biological world because of either monomer derivation, end of life degradation or both. The current work is aimed at studying one example of both biopolymers types. Polyhydroxibutyrate (P3HB) is a biodegradable microbial-produced polymer which holds massive potentiality as a substitute of polyolefins such as polypropylene. Though, its highly crystalline nature and stereoregularity of structure make it difficult to work with. The project P3HB-Mono take advantage of polarized Raman spectroscopy to see how annealing of chains with different weights influence the crystallinity and molecular structure of the polymer, eventually reflecting on its mechanical properties. The technique employed is also optimal in order to see how mesophase, a particular conformation of chains different from crystalline and amorphous phase, develops in the polymer structure and changes depending on temperature and mechanical stress applied to the fiber. Polycaprolactone (PCL) on the other hand is a biodegradable fossil-fuel polymer which has biocompatibility and bio-resorbability features. As a consequence this material is very appealing for medical industry and can be used for different applications in this field. One interesting option is to produce narrow and long liquid filled fibers for drug delivery inside human body, using a traditional technique in an innovative way. The project BioLiCoF investigates the feasability of producing liquid filled fibers using melt-spinning techniques and will examine the role that melt-spinning parameters and liquids employed as a core solution have on the final fiber. The physical analysis of the fibers is also interpreted and idea on future developments of the trials are suggested.