R. Baur

• Shell Global

Entropies for alkane isomers longer than C10 are computed using our recently developed linear regression model for thermochemical properties which is based on second-order group contributions. The computed entropies show excellent agreement with experimental data and data from Scott’s tables which are obtained from a statistical mechanics-based cor...

Linear regression (LR) is used to predict thermochemical properties of alkanes at temperatures (0–1000) K to study chemical reaction equilibria inside zeolites. The thermochemical properties of C1 until C10 isomers reported by Scott are used as training data sets in the LR model which is used to predict these properties for alkanes longer than C10...

We study important aspects of shape selectivity effects of zeolites for hydroisomerization of linear alkanes, which produces a myriad of isomers, particularly for long chain hydrocarbons. To investigate the conditions for achieving an optimal yield of branched hydrocarbons, it is important to understand the role of chemical equilibrium in these rev...

We present the RUPTURA code (https://github.com/iraspa/ruptura) as a free and open-source software package (MIT license) for (1) the simulation of gas adsorption breakthrough curves, (2) mixture prediction using methods like the Ideal Adsorption Solution Theory (IAST), segregated-IAST and explicit isotherm models, and (3) fitting of isotherm models...

Ideal Adsorbed Solution Theory (IAST) is a common method for modelling mixture adsorption isotherms based on pure component isotherms. When the adsorbent has distinct adsorption sites, the segregated version of IAST (SIAST) provides improved adsorbed loadings compared to IAST. We have adopted the concept of SIAST and applied it to an explicit isoth...

The Ideal Adsorbed Solution Theory (IAST) is widely used for the estimation of the mixture adsorption equilibrium, and for quantitative modeling of separations using microporous adsorbents and membranes. With the aid of Configurational-Bias Monte Carlo (CBMC) simulations, the accuracy of the IAST estimations of the component loadings for mixture ad...

The combined phenomena of intra-crystalline adsorption, diffusion and reversible chemical reactions inside microporous crystalline zeolite catalyst particles are described by combining the Langmuir–Hinshelwood kinetics with the Maxwell–Stefan (M–S) diffusion formulation. Simulations of transient diffusion and reaction inside catalyst crystallites a...

In-house refinery models are widely used within Shell for a variety of applications, including product predictions for design and revamp, performance monitoring and plant/refinery wide optimization. These models can be accessed uniformly and efficiently via a proprietary interface that is similar to CAPE-OPEN. A link between the Shell proprietary i...

CAPE-OPEN (CO) is an industry standard that allows the Plug-and-Play interoperability of simulation components, such as unit operations and thermodynamic models, inside chemical process model simulators like Aspen Plus and PRO/II (for a description of CAPE-OPEN see NPT Procestechnologie, February, 2005, pp. 11-13). At the annual CO meeting in Canne...

The Langmuir–Hinshelwood (LH) rate expression is often used to describe the kinetics of heterogeneously catalyzed reactions using zeolites. A factor θV≡[1−i∑θi] in the LH expression allows for the reduction of the reaction rate with increased fractional occupancies θi of the individual species on the surface. Most commonly in practice the multi-com...

We consider the isomerization of 2-methylpentane (2MP) to the di-branched isomer 2,2 dimethylbutane (22DMB) and examine various strategies for improving the conversion of 2MP, exceeding the limitation imposed by reaction equilibrium. Firstly, we examine the conventional reactor-followed-by-separation strategy. We show that a properly optimized true...

The influence is considered of mass transfer on distillation column design. The column design equations incorporating mass-transfer effects are similar to the conventional design equations and are as easy to solve numerically. Mass-transfer effects do not influence pinch-point curves and pitchfork distillation boundaries. Mass transfer does, howeve...

The Langmuir–Hinshelwood (LH) rate expression is often used to describe the kinetics of heterogeneously catalysed reactions using zeolites. A factor in the LH expression allows for the reduction of the reaction rate with increased fractional occupancies θi of the individual species involved in an n-molecular reaction on the catalyst surface. Most c...

The Maxwell–Stefan (M–S), or corrected, diffusivity, in zeolites shows a variety of dependencies on the molecular loading or occupancies. This loading dependence is caused by a variety of factors, including zeolite topology, connectivity, and molecule–molecule interactions, that lead to a decrease or increase in the energy barrier for diffusion. Us...

The relationship is explored between residue curves and composition trajectories in tray and packed distillation columns. The standard model for residue curves as described by, for example, Doherty and Malone is completely consistent, and that published attempts to modify this model to take into account mass transfer effects are flawed. The packed...

A nonequilibrium (NEQ) model for a complete three-phase distillation in tray columns is described. The model consists of a set of mass and energy balances for each of the three possible phases present. Mass and heat transfer between these phases is modeled using the Maxwell–Stefan equations. Equilibrium is only assumed at the phase boundary between...

We analyze the influence of diffusion on the reversible isomerization reaction A1↔A2, occurring within a zeolite catalyst, of spherical, cylindrical, and slab geometries. The intra-crystalline diffusion process is described by the Maxwell–Stefan (M–S) equations. Two different guest–host confinement scenarios are examined. For strongly confined gues...

The hardware design of reactive distillation (RD) columns pose severe challenges with respect to the choice and design of the hardware; the requirements of reaction (i.e. high liquid or catalyst holdup) is not in consonance with the requirement of separation (high interfacial area). In this paper, we examine an alternative to the RD concept, namely...

The hardware design of reactive distillation (RD) columns pose severe challenges with respect to the choice and design of the hardware; the requirements of reaction (i.e. high liquid or catalyst holdup) are not in consonance with the requirement of separation (high interfacial area). In this paper we examine an alternative to the RD concept, namely...

We develop an analytic solution of the Maxwell–Stefan equations describing steady-state diffusion of n-component mixtures across a zeolite membrane. In the development of the analytic solution we assume Langmuirian behaviour of the pure components and that the mixture sorption can be calculated from the multicomponent Langmuir isotherm. Explicit ex...

The Maxwell Á/Stefan (M Á/S) formulation is shown to be the most convenient and general way of describing diffusion within zeolite structures. This theory goes a long way to explain the observed various types of dependencies of the Fick diffusivity with sorbate loading. For mixture diffusion within zeolites, the M Á/S theory provides clues for the...

T he overall objective of this work is to examine the in uence of interphase mass transfer on the composition trajectories in heterogeneous azeotropic distillation. Experiments were carried out in a bubble cap distillation column operated at total ree ux with the systems: water–ethanol–cyclohexane and water–acetone–toluene. The experiments were car...

This paper presents a bifurcation analysis for synthesis of tertiary amyl ether (TAME) in a reactive distillation (RD) column. Two different methods for describing the reaction kinetics are explored and compared: (A) pseudo-homogeneous models: here the intra-particle diffusion and reaction is simplified by the use of catalyst effectiveness factors...

This paper examines the influence of mass transfer on the composition trajectories in multicomponent azeotropic distillation. Simulations were carried out for three different ternary systems: methanol–isopropanol–water, water–ethanol–acetone, and water–methanol–methylacetate. Two different models were used to calculate the composition trajectories...

Experiments were carried out in a bubble cap distillation column operated at total reflux with the quaternary mixture: water (l)–ethanol (2)–methanol (3)–acetone (4). This system has a binary minimum-boiling azeotrope for the water–ethanol mixture and the distillation boundary is represented by a surface with its corners at pure acetone, pure metha...

We have carried out a step-by-step design study of a reactive distillation (RD) column for synthesis of tertiary-amyl ether (TAME) in order to investigate the influence of the choice of hardware on column design. Two different types of internals are compared: active Raschig rings and catalytic bales. Firstly, an equilibrium (EQ) stage model is used...

Residue curve maps can be used to predict composition trajectories for packed and trayed distillation columns, provided that vapor and liquid phases are in thermodynamic equilibrium and the column is operating at total reflux. In the case of ternary azeotropic distillations, distillation boundaries divide the composition space into two, or more, re...

The dynamics of a reactive distillation column for the synthesis of tertiary amyl ether (TAME) is analyzed using a rigorous nonequilibrium (NEQ) stage model, employing the Maxwell–Stefan equations for mass transfer between fluid phases. Both pseudo-homogeneous and heterogeneous reaction models show the possibility of multiple steady states. Startin...

In this paper we develop a generic, dynamic, nonequilibrium (NEQ) stage model for reactive distillation (RD) columns. The main features of our model are: (1) use of the Maxwell}Stefan equations for describing mass transfer between #uid phases, (2) solid catalysed reactions are treated using a pseudo-homogeneous liquid phase model with the appropria...

We compare the performance of an MTBE synthesis column using two different hardware configurations: (1) a sieve tray column in which the catalyst particles, encased inside wire gauze envelopes, placed along the liquid flow path; (2) a column filled with catalytically active packing of Raschig ring shape. The columns simulations are performed using...

In this paper we develop a generic, dynamic, nonequilibrium (NEQ) cell model for reactive distillation (RD) tray columns. The features of our model are (1) the use of Maxwell–Stefan equations for describing mass transfer between fluid phases, (2) the reaction is assumed to take place in the liquid phase, both within the diffusion layer and in the b...

In this paper we develop a nonequilibrium (NEQ) cell model to describe the dynamic operation of reactive distillation (RD) tray columns. The features of our model are: (1) use of the Maxwell}Stefan equations for describing mass transfer between #uid phases, (2) chemical reactions are assumed to take place only in the liquid phase, (3) coupling betw...

For modelling reactive distillation columns, two distinctly different approaches are available in the literature: (1) the equilibrium (EQ) stage model, in which the vapour and liquid phases are assumed to be in thermodynamic equilibrium, and (2) the nonequilibrium (NEQ) stage model in which the finite mass transfer rates across the vapour–liquid in...

T his paper examines the in uence of mass transfer on the composition trajectori es during distillatio n of mixtures that exhibit distillatio n boundaries. Simulations for total re ux distillatio n of the system s methanol-iso-propanol-water and benzene-iso-propanol-n-propanol show that composition trajectories originating along the distillatio n b...

Maple is a computer algebra system that has the potential to be the tool of choice for many computational problems in science and engineering. In this article, we show how Maple can be used to develop graphical images of thermodynamic functions. We also describe ThermoView, a standalone program that can display Maple-based images and animations. Th...

Dynamic simulations of a 15 stage MTBE reactive distillation column have been performed with the SPEEDUP flowsheeter. The simulations confirm that the column configuration with fixed bottom outflow rate can display steady-state multiplicity. Changes in the column operation (feed flow rate or composition) can cause a jump from one steady state to an...