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The high price of marketing of extra virgin olive oil (EVOO) requires the introduction of cost-effective and sustainable procedures that facilitate its authentication, avoiding fraud in the sector. Contrary to classical techniques (such as chromatography), near-infrared (NIR) spectroscopy does not need derivatization of the sample with proper integration of separated peaks and is more reliable, rapid, and cost-effective. In this work, principal component analysis (PCA) and then redundancy analysis (RDA)─which can be seen as a constrained version of PCA─are used to summarize the high-dimensional NIR spectral information. Then PCA and RDA factors are contemplated as explanatory variables in models to authenticate oils from qualitative or quantitative analysis, in particular, in the prediction of the percentage of EVOO in blended oils or in the classification of EVOO or other vegetable oils (sunflower, hazelnut, corn, or linseed oil) by the use of some machine learning algorithms. As a conclusion, the results highlight the potential of RDA factors in prediction and classification because they appreciably improve the results obtained from PCA factors in calibration and validation.

The integrity of extra virgin olive oil (EVOO) quality markers can be compromised owing to deceptive marketing practices, such as misleading geographical origin claims or counterfeit certification labels, i.e., protected designations of origin (PDO). Therefore, it is imperative to introduce ecofriendly, rapid, and economical analytical methods for authenticating EVOO, such as near-infrared (NIR) spectroscopy. Unlike traditional techniques such as chromatography, NIR spectra contain unresolved bands; hence, chemometric tools such as principal component analysis (PCA) are essential for extracting valuable information from them. Herein, PCA was employed to reduce the high dimensionality of the NIR spectra. The PCA factors were then integrated as explanatory variables in machine-learning classification models, enabling the classification of EVOO based on its geographical origin or PDO. Furthermore, the classification models were improved by incorporating agro-climatic data, resulting in a noticeable improvement in the accuracy and reliability of the results. These results were cross-validated by changing the calibration and validation subsamples in successive iterations and averaging the obtained ratios. The results were robust when the olive varieties differed. Consequently, our findings highlight the potential benefits of incorporating agro-climatic information with NIR spectral data in classification models.

A study of the Knoevenagel condensation of p-substituted benzaldehydes with malononitrile or ethyl cyanoacetate over potassium, calcium and lanthanum modified MgO was carried out under thermal and microwave activation. The catalysts were fully characterized to determine their textural, structural and surface acid–base properties. The whole set of catalysts were essayed in propan-2-ol test reaction in order to gain a better understanding of their acid–base properties. As for the surface basic properties of the catalysts, the modification of MgO with Ca and K led to solids with enhanced basicity while La modification slightly reduced the basicity of bare MgO. Inductive and mesomeric effects of the substituent in p-substituted benzaldehydes were coherent with a reaction mechanism in which a nucleophilic attack to the carbon atom of the carbonyl group takes place. Malononitrile or ethyl cyanoacetate were used as the active methylene reagent and the reaction was faster in the case of malononitrile as compared to ethyl cyanoacetate, indicating that the nucleophile formation (carbanion) on the catalyst basic sites is an important issue in this reaction. As for the catalysts, the overall reactivity order in thermal Knoevenagel condensation was $${\text{MgO}}-{\text{K}}\left( {\text{I}} \right)>{\text{MgO}}-{\text{K}}\left( {\text{II}} \right)>{\text{MgO}}-{\text{Ca}}\left( {\text{I}} \right) \approx {\text{MgO}}{-}{\text{La}}\left( {\text{II}} \right) \approx {\text{MgO}}>{\text{MgO}}{-}{\text{La}}\left( {\text{I}} \right)$$ MgO-KI>MgO-KII>MgO-CaI≈MgO-LaII≈MgO>MgO-LaI , which completely agrees with the catalyst basicity extracted from the propan-2-ol test reaction (yield to acetone). The above correlation confirmed that, in Knoevenagel condensation, the carbanion formation on the surface basic sites of the catalysts is a key step in the reaction mechanism. The microwave-activated Knoevenagel reaction was much faster than the conventional, thermally activated reaction. The results indicate that the nucleophilic character of the Knoevenagel condensation also prevails under microwave activation.

Two ZrO2-based catalysts have been synthesized by thermal treatment of a gel prepared from ZrOCl2· 8H2O. The effect of different preparation parameters on the final properties of the solids was studied. Textural characterization was carried out from nitrogen adsorption/desorption isotherms. XRD and FT-Raman spectroscopy have been used to elucidate the physical state of the catalysts. Their acid–base properties were studied following temperature programmed desorption–mass spectrometry and diffuse reflectance infrared Fourier transform techniques, by using pyridine, 2,6-dimethylpyridine and carbon dioxide as probe molecules. Both solids were tested for the 2-methyl-3-butyn-2-ol reaction by using two different procedures: (a) in a microcatalytic pulse reactor and (b) through isotherm and temperature programmed surface reactions in a flow reactor. In addition, temperature programmed oxidation and temperature programmed desorption experiments revealed that catalyst deactivation was caused by carbon deposition on the catalytic surface. Amphoteric selectivity for both solids, leading to 3-hydroxy-3-methyl-2-butanone and 3-methyl-3-buten-2-one, depends on the reaction temperature; thus, it is 92% at 225°C for a catalyst calcined at 400°C (ZrO2–400VAC).

Different CuO nanoparticles were synthesized and tested in CuO:TiO2physical mixtures for hydrogen production through glycerol photoreforming. CuO alone was inactive whereas its presence in CuO:TiO2mixtures significantly improved the photoactivity of TiO2, with smaller CuO nanoparticles leading to higher hydrogen productions. Results obtained through combination of EPR and CV studies suggested the existence of a Cu(II)-Cu0catalytic cycle. Thus, electrons promoted to the conduction band of titania could be used for CuO reduction to Cu which in turn would enable hydrogen production regenerating Cu2+for a new catalytic cycle. All in all, a hydrogen production of 88mmol·g-1was obtained after 5h on a CuO:TiO2(10% w/w) physical mixture which is comparable to that achieved in a previous study under identical reaction conditions on 1.5%Pt/TiO2.