Since 2011 gasoline is blended with bioethanol (5–10 Vol.-%) to comply with the biofuel quota required by law. To examine the influence of the bioethanol additive on the functionality of the fuel vapour restraint systems a suitable test facility is designed. This test facility enables automated long-term tests lasting several weeks. As a result, the adsorption behaviour of the activated carbon filters is examined by the used sensors for multiple ad- and desorption cycles even in case of multicomponent mixtures.
The traditional version of the theory of volume filling of micropores was used for the estimation of the fractal dimension of microporous solids. For this purpose, the Dubinin's integral equation was solved for infinite and limited integration limits. The results were applied to the adsorption of nitrogen (T = 78 K) on coal samples and Davisil F silica and to the adsorption of water (Т = 293 К) on lunar soil sample and on rice starch.
Adsorption hysteresis in the low-pressure range is only rarely described in the literature. To optimise, for example, heat storage technologies, a deeper understanding of the low-pressure hysteresis (LPH) process is necessary. Here, two thermodynamically based approaches are further developed for analysing the LPH within the framework of thermodynamically irreversible processes and fractal geometry. With both methods developed, it is possible to obtain the description of the adsorption and desorption branches with high accuracy. Within the framework of the two thermodynamic models of the hysteresis loop, generalised equations are obtained with the control parameter in the form of the degree of irreversibility. This is done by taking the adsorption of water on alumina as an example. It is shown that the fractal dimension of the adsorption process is larger than the fractal dimension of the desorption branch, meaning that the phase state of the adsorbate is more symmetric during the adsorption step than in the desorption process.
Fuel vapor restraint systems are used in vehicles to avoid discharge of volatile hydrocarbons from fuel tanks. Until 2020 nearly 10% of all fossil fuels shall be replaced by biofuels upon which bioethanol plays an important role. The topic of this article is the proper operation of fuel vapor restraint systems depending on the composition of bioethanol-fuel blends. As a first step, activated carbons commonly used in fuel restraint systems are tested. Received results and measured data serve as input for a mathematical model with the intention to simulate the performance of fuel vapor restraint systems depending on bioethanol-fuel composition
The experiments on the kinetics of molecular desorption from structurally disordered adsorbents clearly demonstrate its non-Debye behavior at “long” times. In due time, when analyzing the desorption of hydrogen molecules from crystalline adsorbents, attempts were made to associate this behavior with the manifestation of second-order effects, when the rate of desorption is limited by the rate of surface diffusion of hydrogen atoms with their subsequent association into molecules. However, the estimates made in the present work show that the dominance of second-order effects should be expected in the region of times significantly exceeding those where the kinetics of H2 desorption have long acquired a non-Debye character. To explain the observed regularities, an approach has been developed according to which frozen fluctuations in the activation energy of desorption play a crucial role in the non-Debye kinetics of the process. The obtained closed expression for the desorption rate has a transparent physical meaning and allows us to give a quantitative interpretation of a number of experiments on the desorption kinetics of molecules not only from crystalline (containing frozen defects) but also from amorphous adsorbents. The ways of further development of the proposed theory and its experimental verification are outlined.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.