Application of molecular sieves in the fractionation of lemongrass oil from high-pressure carbon dioxide extraction

The aim of this work was to study the feasibility of simultaneous process of high-pressure extraction and fractionation of lemongrass essential oil using molecular sieves. For this purpose, a high-pressure laboratory-scale extraction unit coupled with a column with four different stationary phases for fractionation: ZSM5 zeolite, MCM-41 mesoporous material, alumina and silica was employed. Additionally, the effect of carbon dioxide extraction variables on the global yield and chemical composition of the essential oil was also studied in a temperature range of 293 to 313 K and a pressure range of 100 to 200 bar. The volatile organic compounds of the extracts were identified by a gas chromatograph coupled with a mass spectrometer detector (GC/MS). The results indicated that the extraction process variables and the stationary phase exerted an effect on both the extraction yield and the chemical composition of the extracts

Modification of Activated Carbon for the Adsorption of Humic Acid

Commercial activated carbon treated with sulphuric and phosphoric acids was used to remove humic acids (HAs) from water. To achieve this goal, the iodine indices of treated and untreated materials were characterized by X-ray diffraction and nitrogen physisorption. Adsorption assays for HAs evaluated the quantities adsorbed after a fixed time. Temporal evolution of HA adsorption was determined from the adsorption kinetics. Experimental results indicated that the sulphuric acid treatment was more efficient and had a higher HA adsorption at each time point evaluated. Evaluating the specific area helped to verify this fact, reflecting the number of mesopores in the used material

Towards the design of efficient metal free ORR catalysts based on Zeolite Templated Carbons

International audienceCarbon and carbon/nitrogen Zeolite Templated Carbons (C-ZTC and CN-ZTC) were synthesized from pure ethylene and acetonitrile precursors and thoroughly characterized by nitrogen physisorption at 77 K, SEM, XRD, TGA, Raman spectroscopy and XPS. The CN-ZTC presented high nitrogen content (C/N = 12.5) and a less condensed skeleton compared to C-ZTC. Reduced micropore volume of CN-ZTC was observed due to the formation of extra-ZTC graphene-like species on the external surface, leading to high electron conductivity. The preparation of CN-ZTC based catalysts allowed for achieving conspicuously high ORR activity, featuring a half-wave potential of 0.81 V vs. RHE and high hydroxyl selectivity