Development of catalytic hydrogenation reactors for the fine chemicals industry

A survey is given of the problems to be solved before catalytic hydrogenation reactors can be applied in a multiproduct plant in which selectivity problems are experienced. Some results are reported on work done on the reaction kinetics of two multistep model reactions and on mathematical modelling and experimental verification of the models. Since hydrogenation reactions are often very exothermic, cooling by solvent evaporation has been applied where appropriate. Sufficient information has been collected and correlated to enable operation of multiproduct catalytic reactors of the slurry or packed bubble column type; interdependence of operating variables is so complex that a mathematical model is indispensable

Three-phase packed bed reactor with an evaporating solvent—II. Modelling of the reactor

In this paper two models are presented for a three-phase catalytic packed bed reactor in which in evaporating solvent is used to absorb and remove most of the reaction heat. A plug flow model and a model comprising mass and heat dispersion in the reactor are discussed. The results of both models are compared to each other and to experimental data obtained in a miniplant on the hydrogenation of 2,4,6-trinitrotoluene to triaminotoluene described in Part I. The influence of reactor pressure, feed temperature and the molar ratio of hydrogen to the reactant in the feed are discussed. It is concluded that both models can well describe the influence of the operating variables on the reactor behaviour and that a large part of the reaction heat can be removed by evaporation of the solvent. From a comparison with the experimental results it is concluded that the dispersion model can well describe the experimental data for a fresh catalyst. The agreement between the model and the experimental data for a deactivated catalyst is not good. As long as no quantitative description of the local deactivation in the packed bed is available, any model will fail to predict local concentrations in the reactor. Despite this drawback recommendations can be given how to use this reactor type of optimize the selectivity in producing an intermediate product

Three-phase packed bed reactor with an evaporating solvent—I. Experimental: the hydrogenation of 2,4,6-trinitrotoluene in methanol

In this paper we present experimental data on the three-phase hydrogenation of 2,4,6-trinitrotoluene (TNT) to triaminotoluene. The experiments are performed in a cocurrent upflow packed bed reactor. Methanol is used as an evaporating solvent. The influence of the main operating parameters, the reactor pressure, the feed temperature and the molar ratio of hydrogen to TNT in the feed, are investigated experimentally. A rapid deactivation of the catalyst was observed. The rate of deactivation was investigated by performing experiments at standardized conditions at regular time intervals and by continuous operation of the reactor. Several experiments were done to find out if the catalyst could be regenerated in situ. This regeneration proved successful: the catalyst activity was practically equal to the initial one

Catalytic hydrogenation reactors for the fine chemicals industries: Their design and operation

Design and operation of reactors for catalytic hydrogenation in the fine chemical industries are discussed. The requirements for a good multiproduct catalytic hydrogenation unit as well as the choice of the reactor type are considered. Packed bed bubble column reactors operated without hydrogen recycle are recommended as the best choice to obtain a flexible reactor with good selectivities. The results of an experimental study of the catalytic hydrogenation of 2,4-dinitrotoluene (DNT) in a miniplant installation are presented to prove that the maximum yield in such a reactor can be achieved without a hydrogen recycle and with a hydrogen supply somewhat higher than the stoichiometric amount. Some characteristic properties of the reactor system and the influence of the reactor pressure and the hydrogen supply ratio are elucidated

Virtual Reality as a Tool for Cognitive Behavioural Therapy: A Review.

This chapter describes the deployment of Virtual Reality (VR) for Cognitive Behavioral Therapy (CBT) to treat anxiety and other psychological disorders. Regarding anxiety, the most common technique is constituted of Exposure Therapy that, transposed to Virtual Reality, allows the patient to face a digital version of the feared object or situation, instead of a real or imaginal one. Virtual Reality Exposure Therapy (VRET) has proved effective in the treatment of anxiety disorders such as social phobia, Post-Traumatic Stress Disorder (PTSD), and panic disorder with agoraphobia and has shown an efficacy comparable to traditional in-vivo exposure with various specific phobias such as arachnophobia, acrophobia, and fear of flying. Thanks to its versatility, VR has also found an employment within the CBT framework with other psychological disorders, such as substance abuse, eating disorders, and in inducing non-pharmacological analgesia in patients undergoing painful medical procedures. Even when VR-based therapy does not lead to better results than traditional CBT in terms of efficacy, there are several reasons for preferring it over in-vivo exposure, including patient\u2019s comfort and safety, as well as the possibility to create complex or delicate scenarios (e.g. PTSD scenarios). In addition, VRET can be employed to facilitate the transition toward fearful objects in the real world in patients who would otherwise refuse to face real stimuli