Mathematical simulation of catalytic dehydrogenation of ethylbenzene to styrene in a composite palladium membrane reactor

Flux-Reducing Tendency of Pd-Based Membranes Employed in Butane Dehydrogenation Processes

We report on the effect of butane and butylene on hydrogen permeation through thin state-of-the-art Pd-Ag alloy membranes. A wide range of operating conditions, such as temperature (200-450 °C) and H2/butylene (or butane) ratio (0.5-3), on the flux-reducing tendency were investigated. In addition, the behavior of membrane performance during prolonged exposure to butylene was evaluated. In the presence of butane, the flux-reducing tendency was found to be limited up to the maximum temperature investigated, 450 °C. Compared to butane, the flux-reducing tendency in the presence of butylene was severe. At 400 °C and 20% butylene, the flux decreases by ~85% after 3 h of exposure but depends on temperature and the H2/butylene ratio. In terms of operating temperature, an optimal performance was found at 250-300 °C with respect to obtaining the highest absolute hydrogen flux in the presence of butylene. At lower temperatures, the competitive adsorption of butylene over hydrogen accounts for a large initial flux penalty.

Energy efficiency analysis of styrene production by adiabatic ethylbenzene dehydrogenation using exergy analysis and heat integration

Styrene is a valuable commodity for polymer industries. The main route for producing styrene by dehydrogenation of ethylbenzene consumes a substantial amount of energy because of the use of high-temperature steam. In this work, the process energy requirements and recovery are studied using Exergy analysis and Heat Integration (HI) based on Pinch design method. The amount of steam plays a key role in the trade-off between Styrene yield and energy savings. Therefore, optimizing the operating conditions for energy reduction is infeasible. Heat integration indicated an insignificant reduction in the net energy demand and exergy losses, but 24% and 34% saving in external heating and cooling duties, respectively. When the required steam is generated by recovering the heat of the hot reactor effluent, a considerable saving in the net energy demand, as well as the heating and cooling utilities, can be achieved. Moreover, around 68% reduction in the exergy destruction is observed.

Evaluation of the Parameters and Conditions of Process in the Ethylbenzene Dehydrogenation with Application of Permselective Membranes to Enhance Styrene Yield

Styrene is an important monomer in the manufacture of thermoplastic. Most of it is produced by the catalytic dehydrogenation of ethylbenzene. In this process that depends on reversible reactions, the yield is usually limited by the establishment of thermodynamic equilibrium in the reactor. The styrene yield can be increased by using a hybrid process, with reaction and separation simultaneously. It is proposed using permselective composite membrane to remove hydrogen and thus suppress the reverse and secondary reactions. This paper describes the simulation of a dehydrogenation process carried out in a tubular fixed-bed reactor wrapped in a permselective composite membrane. A mathematical model was developed, incorporating the various mass transport mechanisms found in each of the membrane layers and in the catalytic fixed bed. The effects of the reactor feed conditions (temperature, steam-to-oil ratio, and the weight hourly space velocity), the fixed-bed geometry (length, diameter, and volume), and the membrane geometry (thickness of the layers) on the styrene yield were analyzed. These variables were used to determine experimental conditions that favour the production of styrene. The simulation showed that an increase of 40.98% in the styrene yield, compared to a conventional fixed-bed process, could be obtained by wrapping the reactor in a permselective composite membrane.

Porous ternary Fe-based catalysts for the oxidative dehydrogenation of ethylbenzene in the presence (absence) of carbon dioxide

Porous ternary Fe-based catalysts were characterized and their catalytic properties through the oxidative dehydrogenation of ethylbenzene in the presence (ODH) or absence (DH) of carbon dioxide were investigated.

A new perspective on catalytic dehydrogenation of ethylbenzene: the influence of side-reactions on catalytic performance

The dehydrogenation of ethylbenzene to styrene over CrOx/Al₂O₃ proceeds via a partially oxidative mechanism due to in situ formation of CO₂. Coke formation also plays a key role in dictating catalytic performance.

Oxydehydrogenation of Ethylbenzene to Styrene: Membrane Reactor Analysis and Design

The preliminary design of shell-and-tubes membrane reactor for oxidative dehydrogenation of ethylbenzene to styrene on a P–O–Ni–Mn/alumina catalyst (on an industrial scale) is presented. A one-dimensional pseudo-homogeneous model is used. The membrane is an inorganic and non-perm-selective one; nevertheless, it enables an oxygen flow high enough to ensure the progress of the reaction. The influence of different disturbances (feed composition, pressure and temperature) on the evolution of conversion of ethylbenzene and selectivity to styrene is analyzed. Membrane reactor allows achieving high selectivity to styrene and moderate conversion of ethylbenzene, keeping a low oxygen concentration on the reaction side. Styrene production overcomes the expected amount to carry out the design.