Reaction scheme and kinetic modelling for the MTO process over a SAPO-18 catalyst

A kinetic model for simulation of the MTO process over SAPO-18 catalyst in a wide range of operating conditions has been proposed. The kinetic model predicts the experimental evolution of reaction products with time on stream, which follows three consecutive periods: initiation (where olefin production increases), a period of maximum olefin production and a period in which this production decreases. The kinetic scheme takes into account these three steps that evolve with time on stream: formation of active intermediate compounds, an step where olefins are formed by reaction of oxygenates (methanol/DME) with these intermediates and deactivation of intermediates by degradation to coke. The presence of water in the reaction medium attenuates the reaction rate of these steps. Discrimination of kinetic equations and calculation of the parameters of best fit have been carried out by solving the mass conservation equations of the individual components of the kinetic scheme together with the kinetic equation for deactivation and taking into account the effect of water on the kinetics of each step.     

Study of operating variables in the transformation of aqueous ethanol into hydrocarbons on an HZSM‐5 zeolite

With the aim of determining the possibilities of directly upgrading the liquid obtained from carbohydrate fermentation, the effect of operating conditions (temperature, space time, water content in the feed) has been studied in the catalytic transformation of aqueous ethanol into hydrocarbons on an HZSM‐5 zeolite in an isothermal fixed bed reactor. Special attention has been paid to the effect of water content on the yield, product distribution and catalyst deactivation. Although deactivation by coke decreases as the water content is increased, this content must be limited at 450 °C and higher temperatures in order to avoid irreversible deactivation of the catalyst by dealumination. © 2002 Society of Chemical Industry     

Impact of lossy compression on mapping crop areas from remote sensing

This study measures the effect of lossy image compression (JPEG 2000 and JPG) on the digital classification of crop areas. The results provide new insights into the influence of compression on the quality of the cartography produced. Both a multitemporal and a single-date classification approach were analysed. With the multitemporal approach, it is possible to use high compression ratios (CRs), up to 20:1 or even 100:1, and the overall accuracy of the classification is similar to that obtained with the original images. Moreover, the classified area is similar or even greater (fewer pixels are uncertain). For a single-date approach, it is only advisable to use 3D-JPEG 2000 at CRs up to 20:1. The optimum CR is also affected by landscape fragmentation (fragmented images tolerate less compression) and the classification method (hybrid classifiers are affected less than the maximum likelihood and minimum distance classifiers). Finally, classifications from compressed images have less ‘salt and pepper’ effect than those obtained from the originals, especially when JPEG 2000 (3D or not) is used.     

Regional Differences in the Price Elasticity of Residential Water Demand in Spain

This paper explores the influence of regional climate variability on the elasticity of price for residential water demand in Spain. The data comes from the Spanish Survey of Family Budget (INE 2012), a national based survey of household living conditions including more than 15,000 observations. The econometric analysis included other determinants of residential water demand in Spain such as income and household characteristics. In line with the broad literature, the demand for water in Spain is found to be inelastic, although price elasticity differs notably when accounting for different climatic regions in the territory. The results have noteworthy policy implications as water pricing is considered an efficient means of long term sustainable planning of water resources management. The results imply that policy makers may have reasons to explore differentiating the impacts of water efficiency measures by region.     

Undesired components in the transformation of biomass pyrolysis oil into hydrocarbons on an HZSM‐5 zeolite catalyst

The results of the catalytic transformation on HZSM‐5 zeolite of mixtures of components of biomass pyrolysis oil in the 673–723 K temperature range are evidence of the need for previously separating certain components (aldehydes, oxyphenols and furfural) that undergo severe thermal degradation by forming carbonaceous deposits at the reactor inlet ducts and on the catalyst itself. The deactivation of the catalyst is a consequence of the deposition of two different types of coke: one of catalytic origin (similar to that generated in the transformation of methanol and bioethanol) and the other of thermal origin, which is produced by the aforementioned degradation. The remaining oxygenate components react to each other with synergistic effect, which means that their reactivity is higher than that of the pure components. The results show that the aqueous fraction of biomass pyrolysis oil may be transformed into hydrocarbons on acid catalysts similarly to the more familiar transformation of methanol and bioethanol. Copyright © 2005 Society of Chemical Industry     

Aging and flexible remembering: Contributions of conceptual span, fluid intelligence, and frontal functioning.

Aging attenuates the capacity to adaptively and flexibly use episodic memory at different levels of specificity. Older and younger adults were tested on a picture recognition task that required them to make episodic memory decisions at an item-specific (verbatim) versus category-based (gist-based) level on randomly intermixed trials. Specificity modulation was assessed using a measure of the likelihood that participants retrieved verbatim information in order to reject test items that were categorically related to studied items under item-specific recognition instructions (recollection rejection). We found that this measure positively correlated with conceptual span (an index of short-term semantic memory) and with level of fluid intelligence in older and younger adults. However, when we simultaneously considered each of four possible contributors (age, conceptual span, fluid intelligence, and frontal function), the only significant predictor of recollection rejection was the composite fluid intelligence measure (assessed by the Culture Fair Intelligence Test [Cattell & Cattell, 1960] and the Wechsler Adult Intelligence Scale—Revised Block Design subtest [Wechsler, 1981]). These findings suggest that interventions that facilitate adaptive specificity modulation in episodic memory may enhance the flexibility of thinking, and vice versa, in both older and younger adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of nickel incorporation on the acidity and stability of HZSM-5 zeolite in the MTO process

A study has been carried on the effect of Ni incorporation on the acidity (acid strength distribution and total acidity), on the hydrothermal stability of a HZSM-5 zeolite and on the kinetic performance of this catalyst in the MTO process at high temperature (up to 500 °C, in order to increase selectivity to olefins) and when there is a high water content in the feed (in order to minimise deactivation by coke). The incorporation of Ni in the HZSM-5 zeolite implies a decrease in the total acidity and in the acid strength of the zeolite and, consequently, the activity of the catalyst decreases. Nevertheless, the catalysts with Ni are hydrothermally more stable than the parent zeolite catalyst. A Ni content around 1 wt% is the optimum, as it allows for uninterrupted operation in reaction–regeneration cycles, with water contents higher than 50 wt% in the medium, without irreversible deactivation, whereas a higher Ni content produces an unnecessary loss of initial activity.     

Design and stabilization of block copolymer micelles via phenol-pyridine hydrogen-bonding interactions

A new approach for the preparation of block copolymer micelles in non-selective solvent is introduced. Phenol-pyridine hydrogen-bonding interactions are used for the first time to prepare core-shell micelles in non-selective solvents using block copolymers and bifunctional low-molecular-weight hydrogen-bonding crosslinkers. Poly(styrene-b-4-vinylphenol)/Bis-pyridyl ethane and poly(styrene-b-4-vinylpyridine)/Bisphenol A were investigated as micelle formation due to phenol-pyridine hydrogen bond crosslinking. The influence of several factors such as temperature, concentration, solvent and pH in micellization-demicellization process was analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic light scattering (DLS) and atomic force microscopy (AFM). This method opens new possibilities to the generation of block copolymer micelles in non-selective solvents.     

Regeneration of a catalyst based on a SAPO‐34 used in the transformation of methanol into olefins

The regeneration by coke combustion of a catalyst based on a SAPO‐34 used in the transformation of methanol into olefins (ethene and propene) has been studied. It has been observed that coke combustion kinetics are strongly dependent on the nature of the coke (H/C ratio), which in turn is a consequence of the reaction conditions (especially of the water content in the feed) and of the ageing level of the coke prior to its combustion. A severe ageing treatment is needed in order for combustion kinetics to be reproducible. Combustion is delayed due to the fact that coke is not an inert material but is bound to the acid sites. © 1999 Society of Chemical Industry     

Enhancing network resources utilization and resiliency in multi-domain bandwidth on demand service provisioning using SDN

Telecommunication Systems - This paper presents a solution to increase bandwidth utilization and to reduce the time necessary to recover from network failures in multi-domain bandwidth on demand...