Ana L. Magalhães

Universal model for accurate calculation of tracer diffusion coefficients in gas, liquid and supercritical systems

In this work it is presented a new model for accurate calculation of binary diffusivities (D12) of solutes infinitely diluted in gas, liquid and supercritical solvents. It is based on a Lennard-Jones (LJ) model, and contains two parameters: the molecular diameter of the solvent and a diffusion activation energy. The model is universal since it is applicable to polar, weakly polar, and non-polar solutes and/or solvents, over wide ranges of temperature and density. Its validation was accomplished with the largest database ever compiled, namely 487 systems with 8293 points totally, covering polar (180 systems/2335 points) and non-polar or weakly polar (307 systems/5958 points) mixtures, for which the average errors were 2.65% and 2.97%, respectively. With regard to the physical states of the systems, the average deviations achieved were 1.56% for gaseous (73 systems/1036 points), 2.90% for supercritical (173 systems/4398 points), and 2.92% for liquid (241 systems/2859 points). Furthermore, the model exhibited excellent prediction ability. Ten expressions from the literature were adopted for comparison, but provided worse results or were not applicable to polar systems. A spreadsheet for D12 calculation is provided online for users in Supplementary Data.

MFI Acid Catalysts with Different Crystal Sizes and Porosity for the Conversion of Furanic Compounds in Alcohol Media

Solid acid catalysts possessing MFI topology and different crystal sizes and porosities were explored for the conversion of carbohydrate‐biomass‐derived α‐angelica lactone and 5‐(hydroxymethyl)furfural, in 1‐butanol at T=120–170 °C, to give levulinate esters and furanic ethers. Micro/mesoporous microcrystalline catalysts were prepared by post‐synthesis base/acid treatments of ZSM‐5 zeolite; the influence of the desilication (base) conditions on the material properties was investigated. A nanocrystalline ZSM‐5 sample was synthesised by using hydrothermal, dynamic conditions and used as a reference material. A comparison of the catalytic performances of materials featuring different morphological, textural, and acid properties highlights a complex interplay between the acid and textural properties. The best‐performing catalyst (MZS0.6) was obtained by post‐synthesis‐treatment; fairly good catalytic stability was confirmed by catalyst recycling, contact tests, and characterisation of the spent catalyst. MZS0.6 was compared with the macrorecticular ion‐exchange resin Amberlyst‐15, chosen as a benchmark solid acid catalyst, in the two reaction systems.