Catalyst modeling/simulation product

Industrially relevant consecutive-competitive reaction schemes on metal catalysts were considered hydrogenation of citral, xylose and lactose. The first case study is relevant for perfumery industry, while the latter ones are used for the production of sweeteners. The catalysts deactivate during the process. The yields of the desired products are steered by mass transfer conditions and the concentration fronts move inside the particles due to catalyst deactivation. The reaction-deactivation-diffusion model was solved and the model was used to predict the behaviours of semi-batch reactors. Depending on the hydrogen concentration level on the catalyst surface, the product distribution can be steered towards isomerization or hydrogenation products. The tool developed in this work can be used for simulation and optimization of stirred tanks in laboratory and industrial scale. 

They focus on the ID simulation of an urea SCR system. The system includes a model for N02 production on a DOC, a model for urea injection, urea decomposition and hydrolysis catalyst, a model for a vanadium-type SCR catalyst and a model for NH3 decomposition on a clean-up catalyst. The catalyst models consist of a ID monolith model with global kinetic reactions on the washcoat surface, kinetic parameters have been taken from literature or adjusted to experimental data from literature. The complete model was implemented in AVL BOOST (2006). AVL BOOST is an engine cycle and gas exchange simulation software tool, which allows for the building of a model of the entire engine. 

Diffiisional restrictions increase the effectiveness of olefin interception sites placed within catalyst pellets. Very high olefin hydrogenation turnover rates or site densities within pellets prevent olefin readsorption and lead to Flory distributions of lighter and more paraffinic hydrocarbons. Identical results can be obtained by introducing a double-bond isomerization function into FT catalyst pellets because internal olefins, like paraffins, are much less reactive than a-olefins in chain initiation reactions. However, light paraffins and internal olefins are not particularly useful end-products in many applications of FT synthesis. Yet, similar concepts can be used to intercept reactive olefins and convert them into more useful products (e.g., alcohols) and to shift the carbon number distribution into a more useful range. In the next section, olefin readsorption model simulations are used to explore these options in the control of FT synthesis selectivity. 

Figure 17 CO oxidation on Pd/alumina model catalysts. Top CO2 production versus time from a pulsed CO beam and a constant O2 beam. Xco is the equivalent CO pressure divided by the sum of the CO and O2 pressures. Down Simulation of the experimental data (on top) with a kinetic model. The inset is an enlargement of part of the figure showing the presence of a small dip after closing of the CO beam. (From J. Libuda et al. [203].)... 

Hydrogenation of crotonaldehyde was studied in liquid phase using Pd/C catalyst. The only product formed was n-but)iraldehyde under the reaction conditions of the present work. The concentration-time profiles were obtained under various operating conditions. The rate constants were evaluated by simulating the concentration-time plots. The model predictions and the experimental data were found to be in good agreement. 

Kinetic data were collected according both to steady-state and transient test protocols. A wide range of operating conditions were covered in terms of temperature (150-550 °C T-window) and feed compositions (NOX/NH3 = 0—1 with NO2/NOX between 0 and 1). As an example. Fig. 18.8a, b compare experimental results (thin lines) and predictive model simulations (thick lines) for NH3 conversion and product concentrations obtained during a NH3 oxidation run (Fig. 18.8a) and an NH3 oxidation test run in the presence of NO (Fig. 18.8b). Focusing on the ammonia oxidation experimental data (Fig. 18.8a, thin lines), it can be noticed that, in line with what we saw over the powdered catalyst (Fig. 18.8a), NH3 conversion started above 160-175 °C and rapidly increased up to 80 % already at 200 °C, before approaching 100 % at 350 °C. NH3 conversion is associated with production of N2 (not detected by the analyzers), N2O and NOx,... 

The present economic and environmental incentives for the development of a viable one-step process for MIBK production provide an excellent opportunity for the application of catalytic distillation (CD) technology. Here, the use of CD technology for the synthesis of MIBK from acetone is described and recent progress on this process development is reported. Specifically, the results of a study on the liquid phase kinetics of the liquid phase hydrogenation of mesityl oxide (MO) in acetone are presented. Our preliminary spectroscopic results suggest that MO exists as a diadsorbed species with both the carbonyl and olefin groups coordinated to the catalyst. An empirical kinetic model was developed which will be incorporated into our three-phase non-equilibrium rate-based model for the simulation of yield and selectivity for the one step synthesis of MIBK via CD. 

Scanning electron microscopy and other experimental methods indicate that the void spaces in a typical catalyst particle are not uniform in size, shape, or length. Moreover, they are often highly interconnected. Because of the complexities of most common pore structures, detailed mathematical descriptions of the void structure are not available. Moreover, because of other uncertainties involved in the design of catalytic reactors, the use of elaborate quantitative models of catalyst pore structures is not warranted. What is required, however, is a model that allows one to take into account the rates of diffusion of reactant and product species through the void spaces. Many of the models in common use simulate the void regions as cylindrical pores for such models a knowledge of the distribution of pore radii and the volumes associated therewith is required. 

Further analysis of plug flow has been given by Destoop and Russell (1995) with a simulated computer model for catalyst and polymer materials. The model was developed based on piston-like flow of plugs separated by plugs of gas. The model has been employed taking into account the product grade, temperature, flow rates and line configuration. 

From the presented data there may be a correlation between the catalyst surface and the observed selectivity changes over time. These changes may be explained by a two-alpha model, where different products are produced on two different sites. Figure 13.15 shows how a product spectrum can be simulated with a change in ratio between the amounts of products produced on each of the two assumed types of sites. For this simulation the values of a and a2 were kept constant and only... 

According to Lutz et al. [65], the mixed aggregate XY is assumed to promote the product with opposite configuration to that of the chiral catalyst X alone, i.e., in the present example the S product. The kinetic steps denoted in Scheme 9, together with the minimal or alternative kinetic model, can give rise to a simulation of the experimentally observed enantioselectivity reversal. 

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