scholarly journals Influencing the activity and selectivity of alkylaromatic catalytic transformations by varying the degree of delamination in MWW zeolites

2016 ◽  
Vol 6 (9) ◽  
pp. 3166-3181 ◽  
Author(s):  
Mogahid Osman ◽  
Sulaiman Al-Khattaf ◽  
Urbano Díaz ◽  
Cristina Martínez ◽  
Avelino Corma
Keyword(s):  
Surface Area ◽  
Internal Surface ◽  
Internal Surface Area ◽  
Alkylation Product ◽  
Catalytic Transformations ◽  
Positive Effect

Increasing the degree of delamination of MWW layered precursors has a positive effect regarding selectivity for the alkylation product, as alkylation is favored vs. disproportionation when increasing the ratio of external to internal surface area.

scholarly journals Heat-Up Performance of Catalyst Carriers—A Parameter Study and Thermodynamic Analysis

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 964
Author(s):  
Thomas Steiner ◽  
Daniel Neurauter ◽  
Peer Moewius ◽  
Christoph Pfeifer ◽  
Verena Schallhart ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Surface Area ◽  
Internal Surface ◽  
Installation Space ◽  
Parameter Study ◽  
Thin Wall ◽  
Primary Role ◽  
Internal Surface Area

This study investigates geometric parameters of commercially available or recently published models of catalyst substrates for passenger vehicles and provides a numerical evaluation of their influence on heat-up behavior. Parameters considered to have a significant impact on the thermal economy of a monolith are: internal surface area, heat transfer coefficient, and mass of the converter, as well as its heat capacity. During simulation experiments, it could be determined that the primary role is played by the mass of the monolith and its internal surface area, while the heat transfer coefficient only has a secondary role. Furthermore, an optimization loop was implemented, whereby the internal surface area of a commonly used substrate was chosen as a reference. The lengths of the thin wall and high cell density monoliths investigated were adapted consecutively to obtain the reference internal surface area. The results obtained by this optimization process contribute to improving the heat-up performance while simultaneously reducing the valuable installation space required.

scholarly journals Plasma Catalysis: Distinguishing between Thermal and Chemical Effects

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 185 ◽  
Author(s):  
Guido Giammaria ◽  
Gerard van Rooij ◽  
Leon Lefferts
Keyword(s):  
Gas Phase ◽  
Surface Area ◽  
Thermal Effects ◽  
External Surface ◽  
Plasma Chemistry ◽  
Internal Surface ◽  
Plasma Power ◽  
External Surface Area ◽  
Internal Surface Area ◽  
Chemical Effects

The goal of this study is to develop a method to distinguish between plasma chemistry and thermal effects in a Dielectric Barrier Discharge nonequilibrium plasma containing a packed bed of porous particles. Decomposition of CaCO3 in Ar plasma is used as a model reaction and CaCO3 samples were prepared with different external surface area, via the particle size, as well as with different internal surface area, via pore morphology. Also, the effect of the CO2 in gas phase on the formation of products during plasma enhanced decomposition is measured. The internal surface area is not exposed to plasma and relates to thermal effect only, whereas both plasma and thermal effects occur at the external surface area. Decomposition rates were in our case found to be influenced by internal surface changes only and thermal decomposition is concluded to dominate. This is further supported by the slow response in the CO2 concentration at a timescale of typically 1 minute upon changes in discharge power. The thermal effect is estimated based on the kinetics of the CaCO3 decomposition, resulting in a temperature increase within 80 °C for plasma power from 0 to 6 W. In contrast, CO2 dissociation to CO and O2 is controlled by plasma chemistry as this reaction is thermodynamically impossible without plasma, in agreement with fast response within a few seconds of the CO concentration when changing plasma power. CO forms exclusively via consecutive dissociation of CO2 in the gas phase and not directly from CaCO3. In ongoing work, this methodology is used to distinguish between thermal effects and plasma–chemical effects in more reactive plasma, containing, e.g., H2.

Evaluation of Nisin-Coated Cellulose Casings for the Control of Listeria monocytogenes Inoculated onto the Surface of Commercially Prepared Frankfurters†‡

2004 ◽  
Vol 67 (5) ◽  
pp. 1017-1021 ◽  
Author(s):  
JOHN B. LUCHANSKY ◽  
JEFFREY E. CALL
Keyword(s):  
Listeria Monocytogenes ◽  
Surface Area ◽  
Internal Surface ◽  
Refrigerated Storage ◽  
Internal Surface Area ◽  
Appreciable Increase ◽  
Potassium Lactate ◽  
Selective Agar ◽  
Peptone Water ◽  
Sodium Diacetate

Commercially prepared frankfurters were formulated with and without ~1.4% potassium lactate and 0.1% sodium diacetate and were subsequently processed in cellulose casings coated with and without nisin (~50,000 IU per square inch of internal surface area) to control the outgrowth of Listeria monocytogenes during refrigerated storage. The frankfurters were inoculated with ~5 log CFU per package of a five-strain mixture of L. monocytogenes and then vacuum sealed before being stored at 4° C for 60 to 90 days. Surviving organisms were recovered and enumerated by rinsing each package with 18 ml of sterile 0.1% peptone water and plating onto MOX selective agar. The data for each of two trials were averaged. In packages that contained frankfurters formulated with potassium lactate and sodium diacetate and prepared in nisin-coated casings, L. monocytogenes levels decreased by 1.15 log CFU per package after 90 days of storage. L. monocytogenes levels decreased by 0.95 log CFU per package in frankfurters that were prepared in casings that were not coated with nisin. In packages of frankfurters that were formulated without potassium lactate and sodium diacetate and prepared in nisin-coated casings, L. monocytogenes levels decreased by 0.88 log CFU per package after 15 days of storage but then increased appreciablythereafter over a 60-day period of refrigerated storage. There was also an appreciable increase in pathogen numbers during 60 days of storage in otherwise similar frankfurters formulated without potassium lactate and sodium diacetate prepared in casings that were not coated with nisin. These data confirm that potassium lactate and sodium diacetate display listeriostatic activity as an ingredient of commercial frankfurters. These data also establish that cellulose casings coated with nisin display only moderate antilisterial activity in vacuum-sealed packages of commercially prepared frankfurters during storage at 4° C.

Calorimetry by immersion into liquid nitrogen and liquid argon: a better way to determine the internal surface area of micropores

2004 ◽  
Vol 277 (2) ◽  
pp. 383-386 ◽  
Author(s):  
Ricardo Navarrete ◽  
Philip Llewellyn ◽  
Françoise Rouquerol ◽  
Renaud Denoyel ◽  
Jean Rouquerol
Keyword(s):  
Surface Area ◽  
Liquid Nitrogen ◽  
Internal Surface ◽  
Liquid Argon ◽  
Internal Surface Area

APPARENT DENSITIES AND INTERNAL SURFACE AREAS OF SELECTED CARBON BLACKS

1962 ◽  
Vol 40 (2) ◽  
pp. 184-188 ◽  
Author(s):  
P. L. Walker Jr. ◽  
W. V. Kotlensky
Keyword(s):  
Surface Area ◽  
Pore Diameter ◽  
Internal Surface ◽  
Nitrogen Adsorption ◽  
Roughness Factor ◽  
Internal Surface Area ◽  
Average Pore ◽  
Carbon Blacks ◽  
Surface Areas ◽  
Nitrogen Adsorption Isotherms

It is shown that the open pore volume within carbon blacks can be calculated from nitrogen adsorption isotherms (77°K) on the blacks. From this volume and a helium density, the apparent density of a black can be calculated. Other properties of the blacks which then can be calculated are free surface area, internal surface area, surface roughness factor, and the average pore diameter of the internal surface. These data are presented for five selected carbon blacks.

Aspects of comparative lung growth

1952 ◽  
Vol 140 (900) ◽  
pp. 432-441 ◽  
Keyword(s):  
Surface Area ◽  
Lung Volume ◽  
Unit Volume ◽  
Structural Complexity ◽  
Internal Surface ◽  
The Other ◽  
Lung Growth ◽  
Normal Numbers ◽  
Elastic Fibres ◽  
Internal Surface Area

In this paper, the general principles of lung growth already worked out in the rabbit (Short 1950) have been examined in the human lung. Using the same methods, a similar series of measurements have been made in embryonic and post-natal human lungs. Structural complexity has been measured in terms of internal surface area per unit volume of lung. Further support has been found for believing that the structural complexity of the lung is the result of tension in elastic fibres. At all stages of development a linear relationship similar to that found in the rabbit has been demonstrated between structural complexity of the lung on the one hand and a factor representing tension in elastic fibres (lung volume/interstitial volume) on the other. During the period of embryonic development, the structural complexity of the lungs of man and the rabbit is in very close agreement. It has also been found that the structural complexity per unit volume of the lungs at term in the mouse, rat, rabbit and man is the same. This suggests that the range of growth, between lung bud and term (responsible for the physical forces acting on elastic fibres and thus increasing the structural complexity), is the same in these four species. In man and the rabbit there are grounds for believing that the range of growth is indeed the same. Direct measurement of the volume of the lung rudiment at a stage when the tracheal bud has divided into two lumina in these two species shows them to be of the same order of size. Since the unit volumes at term are equal, the range of growth is equal in both species; a circumstance which accounts satisfactorily for the fact that the structural complexity at term is also the same in man and the rabbit. Calculation has also been made of the age at which formation of septa stops. In the two small species, the mouse and rat, the complexity of lung architecture probably increases throughout the post-natal period of growth. In the rabbit, differentiation is certainly complete by the third month of life, and in man is probably completed during the second year of life. Thereafter, continued growth of lung volume is accompanied by simple distension of the existing architecture. Further evidence bearing on growth and differentiation has been obtained from grossly hypoplastic lungs. In three cases of diaphragmatic hernia involving reduction of lung volume to one-sixth or less of normal size, structural complexity was found to be normal. Moreover, lobular size was also normal. Had the normal numbers of lobules been formed, their size must necessarily have been reduced. Therefore, reduction in total number of lobules and in total lung volume is not accompanied by structural hypoplasia of those lobules which are formed. The estimate of internal surface area per unit volume of lung in the adult mouse, rat, rabbit and man has been shown to increase as the smaller species are approached. On the other hand, the ratio of total internal surface area of the lung to body weight of these four species is probably to be regarded as a constant.

scholarly journals Preparation of Fiber Reinforced Silica Aerogel Block

2021 ◽  
Vol 353 ◽  
pp. 01016
Author(s):  
Shuning Zhai ◽  
Chi Cao ◽  
Yang Liu ◽  
Chen Gui ◽  
Kai Yuan ◽  
...  
Keyword(s):  
Surface Area ◽  
Silica Aerogel ◽  
Internal Surface ◽  
Fiber Reinforced ◽  
Internal Surface Area ◽  
Composite Aerogel ◽  
Compression Performance ◽  
Polyethylene Fiber ◽  
Wide Range ◽  
Insulation Block

Silica aerogels are lightweight, highly porous nanomaterial with extremely large internal surface area but fragile and brittleness. To enhance the applicability of aerogels, fiber reinforced silica aerogel insulation blocks are prepared by frothing method. Polyurethane emulsion acts as binder whereas polyethylene (PE) fiber and polyurethane (PU) fiber is used as reinforcing phase. The effect of polyethylene fiber and polyurethane fiber on the performance of composites were characterized by material's chemical microscopic morphology, compression performance, recovery performance, surface area, thermal conductivity and hydrophobicity. The research results show that the prepared PU fiber reinforced silica aerogel insulation block has excellent comprehensive performance. The water absorption rate of decreased from 19.35% (0 phr, PU fiber) to 6% (20 phr, PU fiber), and comprehensive rebound rate was increased by 97.83% at 20 phr PU fiber compared with pure insulation block (83.88%). Meanwhile, the dimensional stability of the composite aerogel block is above 96%. PU fiber reinforced silica aerogel insulation block has light weight, good hydrophobicity and good thermal and mechanical properties, so it has a wide range of application prospects in the field of insulation.

Sign in / Sign up

Export Citation Format

Share Document