Polydimethylsiloxane (PDMS) polymers are extensively used in a wide range of research and industrial fields, due to their highly versatile chemical, physical, and biological properties. Besides the different two-dimensional PDMS formulations available, three-dimensional PDMS foams have attracted increased attention. However, as-prepared PDMS foams contain residual unreacted low molecular weight species that need to be removed in order to obtain a standard and chemically stable material for use as a scaffold for different decorating agents. We propose a cleaning procedure for PDMS foams obtained using a sugar templating process, based on the use of two different solvents (hexane and ethanol) as cleaning agents. Thermogravimetry coupled with Fourier Transform Infrared Spectroscopy (TG-FTIR) for the analysis of the evolved gasses was used to characterize the thermal stability and decomposition pathway of the PDMS foams, before and after the cleaning procedure. The results were compared with those obtained on non-porous PDMS bulk as a reference. Micro-CT microtomography and scanning electron microscopy (SEM) analyses were employed to study the morphology of the PDMS foam. The thermogravimetric analysis (TGA) revealed a different thermal behaviour and crosslinking pathway between bulk PDMS and porous PDMS foam, which was also influenced by the washing process. This information was not apparent from spectroscopic or morphological studies and it would be very useful for planning the use of such complex and very reactive systems.

Key features of the deep eutectic solvent-microwave assisted simultaneous extraction of polyphenols and delignification pretreatment of chestnut shell waste are presented.

Zeolite Beta, modified with some salts of alkali and alkaline earth metals (K, Zn, Sn), was tested in the hydrothermal heterogeneous catalytic decomposition of microcrystalline cellulose. The reactions were microwave-assisted, where the microwaves were issued by an in situ coaxial applicator. Zeolites were subjected to an ion-exchange process which determines the loss of crystallinity in the following order: Sn-Beta-IE > K-Beta > Zn-Beta > acid form H-Beta. The interaction between zeolites and microwaves was studied by irradiating zeolite powder under constant power and the heating response was in the following order: K-Beta > NH₄-Beta > Sn-Beta-IE ≈ Zn-Beta > H-Beta > alumina. These results show that the nature of the counterion strongly affects the absorption of microwaves. The catalytic activity of the different systems on the cellulose decomposition was studied, and resulted in the following order: H-Beta > K-Beta > Zn-Beta > Sn-Beta-IE > alumina, when the reaction medium contained 5 mM HCl. The most active catalyst was the acid zeolite Beta and the identified product distribution under the investigated conditions was (mol yield %): levulinic acid (22.3), glucose (12.1), lactic acid (4.1), formic acid (6.6), 5-(hydroxymethyl) furfural (14.6), acetic acid (15.2) and furfuraldehyde (3.1). The effect of temperature, time and the heterogeneous catalyst reuse (H-Beta) on the yields of different products was investigated. The use of MW radiation with a coaxial applicator instead of conventional heating gave clear advantages in the decrease of the reaction time (45 min) and in terms of yield enhancement (78.6% under the best conditions).

This paper deals with the concept of process intensification applied to the extraction of essential oil (EO). Microwave hydrodistillation (MWHD) and simultaneous ultrasound MW-assisted hydrodistillation (US-MWHD) were intensified by coupling them with a green tool: ionic liquids (ILs). The yield and chemical composition of the cumin EO obtained by MWHD and US-MWHD were compared with those from conventional hydrodistillation (HD) using water and three mixtures of water with three different ILs synthesized ad hoc, as maceration and extraction media, and analysed by a multivariate statistical analysis approach. The cumin EO was chemically characterized by GC and GC-MS analysis. The interaction of the ILs and ILs–H₂O mixtures with MW was experimentally investigated and discussed, while the ILs dipole moments and optimized geometry in vacuo and in water were calculated at the DFT level. The different approaches were also compared in terms of energy and time savings. All the data clearly showed that the most promising approach was US-MWHD using a 1,3-dimethylimidazolium dimethylphosphate mixture as maceration and extraction medium. A total yield increase was achieved of up to 75% and an energy saving of 46% compared to the classical HD. The proposed technology, using ILs as green solvents, which fits well with the MW and US technology, enabled a continuous-flow and batch extractor to be constructed which would be useful for industrial applications.