Tapio Salmi

Modeling and simulation of a small-scale trickle bed reactor for sugar hydrogenation

Abstract Laboratory-scale trickle bed reactor was modeled and simulated, taking into account axial dispersion, gas–liquid, liquid–solid and internal mass transfer as well as catalyst deactivation under isothermal conditions. For catalyst particles dynamic and steady state models were developed, including both mass and heat balances. Catalyst deactivation was included in the model by using the final activity concept for the catalyst particles. A well-working numerical algorithm (method of lines) was applied for solving the reactor model with Matlab 7.1 and the results followed experimental trends very well. The steady-state reactor model was based on simultaneous solution of mass balances. The aim was to illustrate how these parabolic partial differential equations could be solved with a step-by-step calculation for a selected geometry. The final model verification was done against experimental data from the hydrogenation of arabinose to arabitol on a ruthenium catalyst.

Chapter 3:Catalytic Hydrogenation of Sugars

Heterogeneous catalytic hydrogenation of various sugars over a range of catalysts was historically done mainly using sponge nickel catalysts, while more recently ruthenium based catalysts started to be applied since Ru affords good activity and excellent selectivity in addition to being void of the toxic properties of Ni. The chapter covers various aspects of catalytic sugar hydrogenations, such as catalyst selection, reaction kinetics, sugar structure influence, structure sensitivity and reactor design.

Kinetics of Catalytic Reactions With Multiple/Multifunctional Catalysts

Various cases of one-pot/tandem or domino/cascade-type processes are discussed, including combined catalytic and noncatalytic reactions and multiple catalysts of the same (heterogeneous; homogeneous; enzymatic) and different types (homogeneous and heterogeneous; homogeneous and organocatalysis; homogeneous and enzymatic; heterogeneous and organocatalysis; heterogeneous and enzymatic; homogeneous, heterogeneous, and enzymatic catalysts in one pot).

Homogeneous Catalytic Kinetics

Kinetics of homogeneous reactions is presented for acid-base and organocatalysis, catalysis by metal ions and transition metals, as well as polymerization reactions. Linear reaction mechanisms with different number of steps are considered. Catalyst systems with ligand-deficient catalysts are described. Kinetic expressions are presented for mechanisms with several reaction routes.

Mass Transfer and Catalytic Reactions

In any catalytic system, not only should chemical reactions be considered, but also mass and heat transfer effects. For example, mass and heat transfer effects are present inside the solid porous catalyst particles, as well as in the surrounding fluid films. This chapter treats simultaneous reaction and diffusion in fluid films and in porous materials, as well as liquid-liquid diffusion and phase-transfer catalysis. Particular attention is given to the combination of chemical reactions and diffusion inside a catalyst particle. Isothermal and nonisothermal cases of reactions with different kinetics are discussed. Similar analysis is provided for immobilized enzymes with Michaelis-Menten kinetics. In addition to catalytic activity, selectivity can also be influenced by mass transfer phenomenon. A few very basic reaction types are analyzed. Impact of deactivation in the case of internal diffusion limitations is discussed. Examples of elucidation the influence of mass transfer by calculating the mass transfer coefficients and catalyst effectiveness factors are provided. Approaches applied to elucidate the impact of heat and mass transfer based on various experimental criteria are presented.

CHAPTER 12:Reactor Technology and Modeling Aspects for the Hydrogenation of Components from Biomass

Catalyst concepts, reaction kinetics, transport phenomena, and reactor technology for hydrogenation of monosaccharides to sugar alcohols are addressed. The chapter highlights the pathway paved from green chemistry towards green process technology. Typically, the catalyst development and screening in addition to kinetic experiments are carried out in batch and semibatch reactors. However, the final goal of a sustainable process is associated with the performance characteristics of fixed-bed reactors. As such, the continuous reactor technology plays a fundamental role in establishing selective and efficient processes for the production of useful molecules from renewable sources. This chapter gives an overview of the important issues that should be considered during scaling up of monosaccharides hydrogenation from batch to continuous mode.