Search results for "Sieve"
showing 6 items of 76 documents
A novel approach to polymer-template mesoporous molecular sieves
2000
A novel synthesis route was developed to produce spherical silica particles. The synthesis is based on a modified Stoeber method and the room-temperature synthesis of MCM 41S-materials applying tetraethoxysilane, alcohol, water, ammonia and homopolymers as template. The specific surface area, the specific pore volume and the average pore diameter were varied in the following ranges: 5 – 1,000 m2/g; 0.1 – 1.0 cm3/g and 2-50 nm. With respect to catalytic applications hetero-atoms e.g. Al were incorporated into the silica framework.
Determination of the Pore Topology of Zeolite IM-5 by Means of Catalytic Test Reactions and Hydrocarbon Adsorption Measurements
2000
Abstract The pore topology of a recently synthesized zeolite IM-5 has been determined by means of catalytic test reactions, i.e., n -decane hydroisomerization–cracking, m -xylene isomerization–disproportionation, n -hexadecane isodewaxing, and adsorption–microcalorimetry of molecules with different sizes and shapes ( n -hexane, toluene, m -xylene, and 1,3,5 trimethylbenzene). It has been found that the channel network consists of a system of unidirectional 10 MR with lobes or side pockets, or crossing 10 membered ring pores with a pore diameter somewhat smaller than those in ZSM-5. This structure offers interesting shape selectivity features for catalytic reactions.
Synthesis of hyacinth, vanilla, and blossom orange fragrances: the benefit of using zeolites and delaminated zeolites as catalysts
2004
The synthesis of phenylacetaldehyde glycerol acetals, 2-benzyl-4-hydroxymethyl-1,3-dioxolane (1), 2-benzyl-5-hydroxy-1,3-dioxane (2), and vanillin propylene glycol acetal (2-(4-hydroxy-3-methoxyphenyl)-4-methyl-1,3-dioxolane) (3) which are flavoring compounds with hyacinth and vanilla scent fragrances, have been carried out successfully by acetalization of phenylacetaldehyde and vanillin with glycerol and propylene glycol, respectively, using toluene as solvent and zeolite catalysts whose adsorption properties have been optimized. However, in the case of a larger size acetal such as 2-acetonaphthone propylene glycol acetal (4) with blossom orange scent, geometrical constraints make the diff…
Steam-activated FeMFI zeolites. Evolution of iron species and activity in direct N2O decomposition
2003
Abstract In this paper the effect of the composition and steaming conditions of FeMFI catalysts on activity in direct N2O decomposition is investigated. MFI zeolites with different framework compositions (FeAlSi, FeGaSi, and FeSi) and without iron ( 100 mbar H2O in N2) favor the extraction of framework iron, enabling the application of lower activation temperatures. The optimum temperature during steam activation is that at which extraction of framework iron is complete without extensive clustering of extra-framework iron species into oxide particles, as was demonstrated by transmission electron microscopy and electrochemical characterization of the samples. Additional experiments show…
TESTING THE GRAIN-SIZE DISTRIBUTION DETERMINED BY LASER DIFFRACTOMETRY FOR SICILIAN SOILS
2012
In this paper the soil grain-size distribution determined by Laser Diffraction method (LDM) is tested using the Sieve-Hydrometer method (SHM) applied for 747 soil samples representing a different texture classification, sampled in Sicily. 005_Di_Stefano(599)_39 28-12-2011 15:01 Pagina 45 The analysis showed that the sand content measured by SHM can be assumed equal to the one determined by LDM. An underestimation of the clay fraction measured by LDM was obtained with respect to the SHM and a set of equations useful to refer laser diffraction measurements to SHM was calibrated using the measurements carried out for 635 soil samples. Finally, the proposed equations were tested using independe…
Prokrastinācijas un apmierinātības ar dzīvi atšķirības starp sievietēm un vīriešiem
2018
Šī pētījuma mērķis bija atrast atšķirības sieviešu un vīriešu prokrastinācijas un apmierinātības ar dzīvi līmeņos. Kopumā tika aptaujāti 81 respondents, no kuriem 44 sievietes un 37 vīrieši vecumā no 23 līdz 53 gadiem. Vidējais dalībnieku vecums 28,53 gadi (SD= 5,60). Pētījumā tika izmantota Prokrastinācijas aptauja (Procrastination Scale (Lay,1986), kuru Latvijā adaptējusi Renāte Buliņa (Buliņa, 2011) un „Apmierinātības ar dzīvi skalas” (Satisfaction With Life Scale (SWLS); Diener et al., 1985) adaptācija Latvijā tika veikta A. Upmanes promocijas darba ietvaros. Aptauja tika izvietota interneta vidē un respondenti to aizpildīja brīvprātīgi. Pētījumā iegūtie rezultāti uzrādīja, ka pastāv st…