No abstract

The cubic-plus-association (CPA) equation of state has been extended to modeling mixtures containing amines. Special focus was given to primary and secondary amines, which are known to self-associate, thus forming hydrogen bonds in mixtures with alkanes. Pure-compound parameters have been determined from vapor pressure and liquid density data, but phase equilibrium data were also used as guidance for selecting the optimum sets among those which best represent the pure-compound properties. Diethylamine was modeled as a two-site molecule, whereas the two primary amines considered (methylamine, ethylamine) were modeled using both the two-site and three-site schemes. Both schemes perform overall equally well, when care is exercised in the parameter estimation, by giving more weight on the vapor pressures rather than the liquid densities. Thus, only results using the two-site scheme are shown. Excellent binary vapor-liquid equilibria have been obtained for amine + aliphatic hydrocarbons with a low value of the binary interaction parameter. Satisfactory results are obtained also for crossassociating systems with alcohols but less so with water, using, moreover, a rather high value of the interaction parameter.

The methanol to olefins reaction has been studied in a small scale fluidized bed reactor over a phosphorus modified ZSM-5 catalyst. The product distribution was relatively insensitive to either feed rate or inlet gas composition. It was more sensitive to temperature with a significant increase in light olefins when the temperature was increased from 400 to 550 °C. A model based on the hydrocarbon pool mechanism is proposed in which olefins form through reversible reactions with a high molecular weight hydrocarbon species in catalyst pores and intersections. Agreement between the model and the product distribution of the olefinic species is good throughout the temperature interval investigated. Further experimental work is required to adequately characterize the paraffin and C 6+ fractions.

Methanol dehydration over a ZSM-5 containing catalyst was studied in a fluidized bed reactor. At temperatures ranging from 250 to 325 • C, methanol conversion varied from 30% at a contact times of 0.14 s and approached 100% of the equilibrium conversion at a contact time starting from 10 s. Sequential and parallel reactions were negligible at low temperatures while hydrocarbon formation became appreciable at 325 • C. Online gas analysis by mass spectrometry provided real-time measurements at a frequency of 4.4 Hz that allowed for fast determination of steady-state conditions. Gas phase residence time distribution (RTD) measurements indicated that axial dispersion was essentially negligible at short contact times with a shallow bed of catalyst. With longer residence times, the flow pattern could be approximated by six continuously stirred-tank reactors (CSTR) in series. Both the simple 1D hydrodynamic model and a detailed multi-zone fluidized model were used to interpret the experimental data to derive a kinetic expression for the dehydration of methanol to di-methyl ether (DME). The expression includes the reverse reaction that is most often neglected in the literature. The reaction data were best fit with the kinetics based on the 1D model. The fluidized bed is a viable reactor type for kinetic measurements of highly exothermic reactions where hotspots and radial and axial temperature gradients are problematic in fixed beds.La déshydratation du méthanol sur un catalyseur contenant du ZSM-5étaitétudiée dans un réacteurà lit fluidisé.À des températures allant de 250à 325 • C, la conversion du méthanol variaità partir de 30%à un temps de contact de 0,14 s et approchait de 100% de la conversion de l'équilibreà un temps de contact commençantà partir de 10 s. Les réactions séquentielles et parallèlesétaient négligeablesà des températures basses, alors que la formation d'hydrocarbure devenait appréciableà 325 • C. Une analyse du gaz en ligne par spectroscopie de masse a fourni des mesures en temps réelà une fréquence de 4,4 Hz, ce qui permettait une détermination rapide de conditions d'état permanent. Les mesures de la distribution des temps de séjour (DTS) de la phase gazeuse ont indiqué que la dispersion axialeétait essentiellement négligeableà des temps de contact courts avec un lit peu profond de catalyseur. Avec des temps de séjour plus longs, on pourrait approximer le modèle d'écoulement par six réacteursà cuve agitée en continu en série.À la fois le modèle hydrodynamique 1-D simple et un modèle fluidisé multizones détaillé ontété utilisés pour interpréter les données expérimentales afin de trouver une expression cinétique pour la déshydratation du méthanol en méthoxyméthane. L'expression comprend la réaction inverse qui est très souvent négligée dans la littérature. Les données de réaction concordaient le mieux avec la cinétique fondée sur le modèle 1-D. Le lit fluidisé constitue un type de réacteur viable pour les mesures cinétiques de réactions très exothermiques pour lesquelles des points chauds ainsi que des...