Search results for "Process"
showing 10 items of 22310 documents
Adsorption and diffusion of linear and dibranched C6 paraffins in a ZSM-5 zeolite
2002
The adsorption of n-hexane and 2,2-dimethylbutane on a commercial ZSM-5 zeolite is studied under isothermal and isobaric conditions. ZSM-5 exhibits two different behaviours with linear and dibranched alkanes. A substep at 4 molec.uc−1 is observed on the adsorption isotherm of n-hexane at 348 K. A singular adsorption-desorption process is evidenced on the adsorption isobar at 5.5 kPa with 2,2-dimethylbutane at a temperature close to 343 K when the sample is activated at 298 K under vacuum. The diffusivities have been determined by fitting directly the uptake curves with a numerical resolution of second Fick's law based on finite difference method. Microporous diffusion seems to be rate limit…
Catalytic cracking of alkanes on MCM-22 zeolite. Comparison with ZSM-5 and beta zeolite and its possibility as an FCC cracking additive
1995
Abstract N-heptane cracking has been carried out on MCM-22, and its kinetic and decay behaviour is compared with that of ZSM-5 and Beta zeolites. In the case of MCM-22 cracking occurs in the 10-member ring channel system, as well as in the large cavities formed by 12-member rings. Product selectivities show that MCM-22, while presenting features which indicate structural similarities with ZSM-5, it also presents characteristics corresponding to pores or cavities larger than ZSM-5. The selectivities to the individual products together with C1 + C2/iC4, C3/C4, C5/C2, iC4/total C4, and alkane/alkene ratios indicate that MCM-22 has good properties to be used as an FCC octane booster additive sp…
Deep oxidation of volatile organic compounds using ordered cobalt oxides prepared by a nanocasting route
2010
Ordered Co3O4 with high surface area (until 173 m2/g) has been successfully obtained through a nanocasting route using mesoporous KIT-6 silica as a hard template and tested in the deep oxidation of a series of representative volatile organic compounds (VOCs): propane as a model of short chain alkane and toluene as a model of monoaromatic hydrocarbon. It has been demonstrated that the catalytic activity for VOC deep oxidation is very elevated and its catalytic stability at moderate temperatures very good. However, the role of the ordered structure in the catalytic performance does not seem to be beneficial. The enhanced catalytic activity has been explained in terms of both the high surface …
Theoretical characterization of iron and manganese porphyrins for catalyzed saturated alkane hydroxylations
1997
Abstract The theoretical characterization of porphin (H2Por), iron and manganese porphyrins MIII(Por) and their chlorine derivatives MIII(Por)Cl has been carried out. This work represents a first step for modelling catalyzed saturated alkane hydroxylations. The chlorine atom is responsible for the existence of a dipole moment of 1.2–2.0 D in the MIII(Por)Cl molecules and for a negative value of the mean quadrupole moment (−16–(−14)DA). The charge of the metal atom (1.8–2.2 e) is rather varied (to 2.1–2.6 e) and the effective polarizability (2.8–2.9 A3) is increased (to 3.5–3.6 A3) by the addition of the chlorine atom. Starting from the porphin molecule, the presence of the metal atom decrea…
Finite-Size and Illumination Conditions Effects in All-Dielectric Metasurfaces
2022
Dielectric metasurfaces have emerged as a promising alternative to their plasmonic counterparts due to lower ohmic losses, which hinder sensing applications and nonlinear frequency conversion, and their larger flexibility to shape the emission pattern in the visible regime. To date, the computational cost of full-wave numerical simulations has forced the exploitation of the Floquet theorem, which implies infinitely periodic structures, in designing such devices. In this work, we show the potential pitfalls of this approach when considering finite-size metasurfaces and beam-like illumination conditions, in contrast to the typical infinite plane-wave illumination compatible with the Floquet t…
Application prospects of silica core side-glowing optical fibers
2005
The side-emitting optical fibers are specially designed to stimulate leakage of the core-transmitted radiation via their side surfaces, so creating the effect of glowing tiny wires. The basic design concepts for this kind of optical fibers are discussed, as well as some of the present and potential future applications.
Rapid automatized naming in early literacy
2019
Esta comunicación se encuentra disponible en la siguiente URL: http://www.infad.eu/RevistaINFAD/OJS/index.php/IJODAEP/article/view/1465/1274 Este número está dedicado a la "Psicología de la Educación y Saberes Originarios". Although the relation between Rapid Automatized Naming (RAN) and Reading is clear, there is no a standardized test to measure the speed of naming in early literacy. The aim is to explore and confirm the factorial structure of the RAN test developed by Wolf and Denkla (2003) in children. RAN test was administred to 442 children aged 4-5 years. Results highlighted two factors: a “nonalphanumeric components” factor which includes “RAN colors” and “RAN images” and an “alphan…
A marching-on in time meshless kernel based solver for full-wave electromagnetic simulation
2012
A meshless particle method based on an unconditionally stable time domain numerical scheme, oriented to electromagnetic transient simulations, is presented. The proposed scheme improves the smoothed particle electromagnetics method, already developed by the authors. The time stepping is approached by using the alternating directions implicit finite difference scheme, in a leapfrog way. The proposed formulation is used in order to efficiently overcome the stability relation constraint of explicit schemes. In fact, due to this constraint, large time steps cannot be used with small space steps and vice-versa. The same stability relation holds when the meshless formulation is applied together w…
The feasibility of pulsed light processing in the meat industry
2019
Abstract Today, the increasing demand for minimally processed foods that are nutritious, sensorially acceptable, and free from microbial, chemical and physical hazards, challenges research and development to establish alternative methods to reduce the level of bacterial contamination. As one of the newly developing non-thermal methods, pulsed light is a technology for the fast, mild, and residue-free surface decontamination of meat and meat contact materials in the meat processing environment. This review provides specific information on pulsed light technology and the feasibility of its application for unpackaged and packaged meat and meat products as well as meat contact materials. The ad…
GRASP with exterior path-relinking and restricted local search for the multidimensional two-way number partitioning problem
2017
In this work, we tackle multidimensional two-way number partitioning (MDTWNP) problem by combining GRASP with Exterior Path Relinking. In the last few years, the combination of GRASP with path relinking (PR) has emerged as a highly effective tool for finding high-quality solutions for several difficult problems in reasonable computational time. However, in most of the cases, this hybridisation is limited to the variant known as interior PR. Here, we couple GRASP with the "exterior form" of path relinking and perform extensive experimentation to evaluate this variant. In addition, we enhance our GRASP with PR method with a novel local search method specially designed for the MDTWNP problem. …