Zeolites and related crystalline molecular sieves are utilised in a wide range of reactions and processes due to their regular microporous structure, strong acidity, shape selectivity and ion-exchange properties.

A combination of post-synthesis modifications and ion-exchange aiming to obtain basic cation-rich hierarchical zeolites X and Y was utilised in this work for the preparation of catalysts for biofuel production from vegetable oils. The secondary mesopore system with a narrow pore size distribution in the 4 nm range was introduced by successive acid and base treatments accompanied with surfactant templating. This was followed by ion-exchange with Cs + and K + cations to produce strong basic catalysts. The prepared hierarchical zeolites have been characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption, Fourier transform infrared spectroscopy (FTIR) and solid state NMR. The transesterification reaction over the zeolite catalysts was carried out in a microwave batch-type reactor and the effects of the reaction conditions, basic properties and pore structure of the hierarchical faujasites were studied in details. The conversion of triglycerides increased with increasing concentration of Cs and K in modified zeolites, but declined with decreasing framework aluminium content. The balance between the strength of the basic sites and their accessibility in hierarchical zeolites and its effect on the catalytic performance of these nanostructured materials is discussed.

Zeolites Y, ZSM-5, beta, mordenite and LTL were converted into hierarchical meso-microporous catalysts applying the surfactant templating strategy and the resulting materials were utilised as catalysts for esterification and aldol condensation reactions for the production of the second generation biofuels and platform chemicals from biomass derived molecules. The relationship between the catalytic performance and the accessibility of active sites in zeolites was examined using FTIR spectroscopy of adsorbed pyridine, 2,4,6-trimethylpyridine and 1,3,5triisopropylbenzene. It was found that the esterification of oleic acid can be enhanced by the presence of strong acid sites in zeolites and their improved accessibility. In the aldol condensation reaction, furfural conversion over hierarchical catalysts also increased as compared to the parent zeolites. However, K-forms of the studied zeolites exhibited a higher conversion and selectivity toward the desired reaction products in comparison with their H-forms. Overall, mesostructured zeolites demonstrated an improved catalytic performance as a result of increasing accessibility of the zeolite active sites.

Self-heating of nanocomposite materials based on the joule heating effect is suitable for numerous engineering applications. In this study, a highefficiency self-heating nanocomposite, using high conductive multi-walled carbon nanotubes (MWCNTs)-based phenolic resin, was fabricated with a hot press method. The microstructure and the thermal stability of self-heating nanocomposite were studied by X-ray diffraction, scanning electronic microscopy, and thermogravimetric tests. Electromechanical and thermal performance tests were conducted to investigate their potential as a self-heating application. Results showed that the compressive strength, modulus, and the piezo-resistive behaviour were higher after adding MWCNTs to the phenolic resin, indicating better load transfer and self-damage sensing as well. Moreover, at 4.0 wt% of MWCNTs concentration, the electrical conductivity of a self-heating nanocomposite showed a higher value of 13.26 S/m which was also found to be proportionally increased with the thickness of the samples, it was ≈25.5 and ≈12.8 S/m for 10 and 3 mm, respectively. In addition, a steady-state temperature of ≈110°C could be reached at low applied volts (8 V) as well as its heating performance was significantly dependent on the input power and the thickness of the sample. This is also confirmed by statistical results between the sample with thicknesses of 3 and 10 mm in terms of power consumption with P value ≈ .0001. Furthermore, the influence of Joule heating was estimated analytically based on the one-dimensional heat transfer equation in companying with other previous models. The estimated distributed temperatures values were in good agreement with the experimental results. The selfheating nanocomposite described in this study has the potential to be used in various industrial applications and a wide range of sectors due to its ability to self-damage sensing, easy fabrication, and high heating efficiency at low power consumption.

Sepiolite-based catalysts loaded with potassium hydroxide were prepared via the wet impregnation and ion-exchange methods and evaluated as catalysts in base-assisted reactions, such as transesterification of renewable oils. The structural features of these catalysts were characterised in detail by variable-temperature in situ X-ray diffraction, N 2 adsorption-desorption, scanning electron microscopy with energy-dispersive X-ray analysis and in situ FTIR spectroscopy. Although a high yield of fatty acid methyl esters was achieved in transesterification reactions in the presence of Kcontaining sepiolite, this system showed significant deactivation due to its structural degradation and loss of the active component during the reaction and regeneration cycles. This work demonstrates for the first time how the thermal and structural stability of sepiolite based systems can affect their performance, which is an essential issue that has not been sufficiently addressed in recent research related to the catalytic applications of these materials.

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ETS-10, zeolite A and sepiolite based nano-structured materials were prepared and modified with potassium containing compounds using ion-exchange or impregnation and evaluated as basic catalysts for transesterification of vegetable oils using microwave heating. The structural features of these catalysts were characterised in detail by the variable temperature in situ X-ray diffraction, N 2 adsorption-desorption, scanning electron microscopy with energy dispersive X-ray analysis and in situ FTIR spectroscopy using adsorption-desorption of acetylene as a basic probe in order to evaluate their structure-catalytic performance relationship in the methanolysis of triglycerides. A wide range of parameters were utilised in order to optimise the reaction conditions. Although a high yield of fatty acid methyl esters with almost 100% selectivity can be achieved in transesterification reactions in the presence of K-containing sepiolite, this system shows significant deactivation due to its structural degradation and loss of the active component during the reaction and regeneration cycles. In contrast, zeolite KA and ETS-10, which are thermally stable crystalline materials, demonstrated no decrease in their activity for up to four reaction runs, and therefore can be used as effective solid basic catalysts in this reaction. Here we explore for the first time how the thermal and structural stability of the supported clay can affect its activity, an essential issue which has not been sufficiently studied in the recent research related to the biofuel production over solid catalysts.

Faujasite (FAU), ZSM-5 (MFI), beta (BEA) and mordenite (MOR) zeolites were admitted to a variety of chemical treatments accompanied by surfactant templating strategy, aiming to introduce the intracrystalline mesoporosity effectively. The resulting materials were tested as solid acid catalysts for esterification of the oleic acid as a common model impurities found in bio-oil feedstoks. It was found that the esterification of oleic acid can be enhanced by the presence of strong acid sites in zeolites and their improved accessibility. Overall, mesostructured FAU zeolite demonstrated an improved catalytic performance as a result of increasing accessibility of the zeolite active sites.