Carl T. Lira

Butyric acid esterification kinetics over Amberlyst solid acid catalysts: the effect of alcohol carbon chain length.

The liquid phase esterification of butyric acid with a series of linear and branched alcohols is examined. Four strong cation exchange resins, Amberlyst™ 15, Amberlyst™ 36, Amberlyst™ BD 20, and Amberlyst™ 70, were used along with para-toluenesulfonic acid as a homogeneous catalyst. The effect of increasing alcohol carbon chain length and branching on esterification rate at 60°C is presented. For all catalysts, the decrease in turnover frequency (TOF) with increasing carbon chain length of the alcohol is described in terms of steric hindrance, alcohol polarity, and hydroxyl group concentration. The kinetics of butyric acid esterification with 2-ethylhexanol using Amberlyst™ 70 catalyst is described with an activity-based, pseudo-homogeneous kinetic model that includes autocatalysis by butyric acid.

A novel process for recovery of fermentation-derived succinic acid: Process design and economic analysis

Recovery and purification of organic acids produced in fermentation constitutes a significant fraction of total production cost. In this paper, the design and economic analysis of a process to recover succinic acid (SA) via dissolution and acidification of succinate salts in ethanol, followed by reactive distillation to form succinate esters, is presented. Process simulation was performed for a range of plant capacities (13-55 million kg/yr SA) and SA fermentation titers (50-100 kg/m(3)). Economics were evaluated for a recovery system installed within an existing fermentation facility producing succinate salts at a cost of

Production of aerogels

0.66/kg SA. For a SA processing capacity of 54.9 million kg/yr and a titer of 100 kg/m(3) SA, the model predicts a capital investment of

A kinetic model of the Amberlyst-15 catalyzed transesterification of methyl stearate with n-butanol

75 million and a net processing cost of

Optical Properties of Free-Standing Ultrahigh Porosity Silicon Films Prepared by Supercritical Drying

1.85 per kg SA. Required selling price of diethyl succinate for a 30% annual return on investment is

Multiphase behavior of carbon dioxide with solid aromatics

1.57 per kg.

Interpretation of Aerogel Shrinkage During Drying.

Abstract Critical point drying of gels with carbon dioxide is used in the preparation of highly porous silica monoliths. In this work, silica with a reproducible density of 0.2 g/cc is obtained. Shrinkage during drying is observed using a high pressure view cell. Shrinkage is found to occur primarily during depressurization. A process has been developed to permit drying in less than 12 hours.

The effect of aging on acid-catalyzed aerogels

An attractive approach to improving cold flow properties of biodiesel is to transesterify fatty acid methyl esters with higher alcohols such as n-butanol or with branched alcohols such as isopropanol. In this study, the reaction kinetics of Amberlyst-15 catalyzed transesterification of methyl stearate, a model biodiesel compound, with n-butanol have been examined. After identifying conditions to minimize both internal and external mass transfer resistances, the effects of catalyst loading, temperature, and the mole ratio of n-butanol to methyl stearate in the transesterification reaction were investigated. Experimental data were fit to a pseudo-homogeneous, activity-based kinetic model with inclusion of etherification reactions to appropriately characterize the transesterification system.

Adsorption equilibrium of benzaldehyde and benzyl alcohol onto polymeric resin from supercritical CO2

Highly luminescent free-standing porous silicon thin films of excellent optical quality have been manufactured by using electrochemical etching and lift-off steps combined with supercritical drying. One to 50 μm thick free-standing layers made from highly (p + ) and moderately (p) Boron doped single crystal silicon (c-Si) substrates have been produced with porosities (P) up to 95 %. The Fabry-Perot fringes observed in the transmission and photoluminescence (PL) spectra are used to determine the refractive index. At the highest P the index of refraction is below 1.2 from the IR to 2 eV. The absorption coefficients follow a nearly exponential behavior in the energy range from 1.2 eV and 4 eV. The porosity corrected absorption spectra of free-standing films made from p type c-Si substrates are blue shifted with respect to those prepared from p + substrates. For P > 70 % a blue shift is also observed in PL. At equal porosities the luminescence intensities of porous silicon films made from p + and p type c-Si are different by one order of magnitude.

An Engineering Model for Adsorption of Gases onto Various Media

Abstract White G.L. and Lira C.T., 1992. Multiphase behavior of carbon dioxide with solid aromatics. Fluid Phase Equilibria , 78: 269-284. Experimental measurements are presented for the melting behavior of naphthalene, acenaphthene, biphenyl and anthracene in mixtures with carbon dioxide. The emphasis of the work is on the determination of the SSLV line in ternary systems, and composition measurements at SLV conditions in binary and ternary systems. The carbon dioxide-rich phase in the system carbon dioxide + naphthalene + biphenyl is shown to undergo a phase transition at temperatures up to 315 K near 7.3 MPa.