Can surface energy measurements predict the impact of catalyst hydrophobicity upon fatty acid esterification over sulfonic acid functionalised periodic mesoporous organosilicas?

Sulfonic acid functionalised periodic mesoporous organosilicas (PrSO3 H-PMOs) with tunable hydrophobicity were synthesised via a surfactant-templating route, and characterised by porosimetry, TEM, XRD, XPS, inverse gas chromatography (IGC) and ammonia pulse chemisorption. IGC reveals that incorporation of ethyl or benzyl moieties into a mesoporous SBA-15 silica framework significantly increases the non-specific dispersive surface energy of adsorption for alkane adsorption, while decreasing the free energy of adsorption of methanol, reflecting increased surface hydrophobicity. The non-specific dispersive surface energy of adsorption of PMO-SO3H materials is strongly correlated with their activity towards palmitic acid esterification with methanol, demonstrating the power of IGC as an analytical tool for identifying promising solid acid catalysts for the esterification of free fatty acids. A new parameter [-ΔGCNP-P], defined as the per carbon difference in Gibbs free energy of adsorption between alkane and polar probe molecules, provides a simple predictor of surface hydrophobicity and corresponding catalyst activity in fatty acid esterification. © 2014 Elsevier B.V.

Hydrothermal saline promoted grafting of periodic mesoporous organic sulfonic acid silicas for sustainable FAME production

Hydrothermal saline promoted grafting of sulfonic acid groups onto SBA-15 and periodic mesoporous organic silica analogues affords solid acid catalysts with high acid site loadings (>2.5 mmol g-1 H+), ordered mesoporosity and tunable hydrophobicity. The resulting catalysts show excellent activity for fatty acid esterification and tripalmitin transesterification to methyl palmitate, with framework phenyl groups promoting fatty acid methyl esters production. (Chemical Equation Presented)

Zr-containing hybrid organic-inorganic mesoporous materials:hydrophobic acid catalysts for biodiesel production

Zirconium-containing periodic mesoporous organosilicas (Zr-PMOs) with varying framework organic content have been synthesized through a direct synthesis method. These materials display the excellent textural properties of the analogous inorganic solid acid Zr-SBA-15 material. However, the substitution of silica by organosilicon species provides a strong hydrophobic character. This substitution leads to meaningful differences in the environment surrounding the zirconium metal sites, leading the modification of the catalytic properties of these materials. Although lower metal incorporation is accomplished in the final materials, leading to a lower population of metal sites, hydrophobisation leads to an impressive beneficial effect on the intrinsic catalytic activity of the zirconium sites in biodiesel production by esterification/transesterification of free fatty acid -containing feedstock. Moreover, the catalytic activity of the highly hybridised materials is hardly affected in presence of large amounts of water, confirming their very good water-tolerance. This makes Zr-PMO materials interesting catalysts for biodiesel production from highly acidic water-containing feedstock. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modelling conditional probability distributions for periodic variables

Most of the common techniques for estimating conditional probability densities are inappropriate for applications involving periodic variables. In this paper we introduce two novel techniques for tackling such problems, and investigate their performance using synthetic data. We then apply these techniques to the problem of extracting the distribution of wind vector directions from radar scatterometer data gathered by a remote-sensing satellite.

Modelling conditional probability distributions for periodic variables

Most of the common techniques for estimating conditional probability densities are inappropriate for applications involving periodic variables. In this paper we apply two novel techniques to the problem of extracting the distribution of wind vector directions from radar catterometer data gathered by a remote-sensing satellite.

Modelling conditional probability distributions for periodic variables

Most conventional techniques for estimating conditional probability densities are inappropriate for applications involving periodic variables. In this paper we introduce three related techniques for tackling such problems, and investigate their performance using synthetic data. We then apply these techniques to the problem of extracting the distribution of wind vector directions from radar scatterometer data gathered by a remote-sensing satellite.

Estimating conditional probability densities for periodic variables

Most of the common techniques for estimating conditional probability densities are inappropriate for applications involving periodic variables. In this paper we introduce three novel techniques for tackling such problems, and investigate their performance using synthetic data. We then apply these techniques to the problem of extracting the distribution of wind vector directions from radar scatterometer data gathered by a remote-sensing satellite.

Towards a semiology of the periodic review of UK regulated utilities

This note explores the regulatory process of UK privatised utilities through the periodic review of prices. It provides a brief history of the privatisation programme in the UK and the theoretical arguments for the price-cap regulation that has been used. It argues that regulatory process appears to involve a covert dialogue and exchange of information between the regulator and regulated and also a second separate review process that consists of an overt dialogue. Using a semiotic analysis the authors suggest that the unfolding of each of these overt reviews follows a very similar pattern that is constantly being re-enacted. It is concluded that further research is required into the relative importance of the two separate review processes in the setting of the price-cap.

Regulation - the movie:a semiotic study of the periodic review of UK regulated industry

This paper explores the regulatory process of UK privatised utilities as manifest in the periodic review of prices. Two separate review processes are identified, operating concurrently - a covert dialogue between the regulator and the regulated and an overt dialogue taking place in the public arena. Using a semiotic analysis of the review the authors argue that the overt event is the real review. Furthermore they argue that the unfolding of each review is so similar that it can be likened to a film script which is constantly re-enacted. The purpose of the review as a legitimating vehicle for the regulator and regulated, who exist in a symbiotic relationship, is explored in terms of the semiotics involved and the myth creation role of legitimation in order to explain the significance of the regulatory process.

Stable propagation of solitons with increased energy through the combined action of dispersion management and periodic saturable absorption

It is shown, through numerical simulations, that by using a combination of dispersion management and periodic saturable absorption it is possible to transmit solitonlike pulses with greatly increased energy near to the zero net dispersion wavelength. This system is shown to support the stable propagation of solitons over transoceanic distances for a wide range of input powers.

Modulational instabilities in fibres with periodic dispersion

We analytically and numerically analyze the occurrence of modulational instability in fibers with periodic changes in the group-velocity dispersion. For small variations, a set of resonances occurs in the gain spectrum. However, large dispersion variations eliminate these resonances and restrict the bandwidth of the fundamental gain spectrum. This research has been motivated by the adoption of dispersion management techniques in long-haul optical communications.

Optical data transmission using periodic in-line all-optical format conversion

We introduce a novel transmission technique of periodic in-line all-optical format conversion between return-to-zero and non-return-to-zero-like aimed at delaying the accumulation of format-specific impairments. A particular realization of this approach using in-line normal dispersion fibre-enhanced nonlinear optical loop mirrors at 40Gbit/s data rate is presented. © 2004 Optical Society of America.

Localized waves in optical systems with periodic dispersion and nonlinearity management

We overview our recent developments in the theory of dispersion-managed (DM) solitons within the context of optical applications. First, we present a class of localized solutions with a period multiple to that of the standard DM soliton in the nonlinear Schrödinger equation with periodic variations of the dispersion. In the framework of a reduced ordinary differential equation-based model, we discuss the key features of these structures, such as a smaller energy compared to traditional DM solitons with the same temporal width. Next, we present new results on dissipative DM solitons, which occur in the context of mode-locked lasers. By means of numerical simulations and a reduced variational model of the complex Ginzburg-Landau equation, we analyze the influence of the different dissipative processes that take place in a laser.