Reaction temperature profiles during

Cutting GR, Tabner BJ. Radical concentrations and reaction temperature profiles during the (batch) core—shell emulsion polymerization of methyl methacrylate and butyl acrylate, studied by electron spin resonance spectroscopy. Eur Polym J 1997 33 213-217. 

Figure 5 shows the axial gas and solid temperature profiles during start-up operation. Notice that the hot spot in the reactor moves down the bed as the heat of reaction increases the temperature of the catalyst particles. Also note the significant temperature difference between the catalyst and gas in the early part of the reactor, where conversion is rapid due to the heat of reaction being generated on the catalyst surface. These differences are even more pronounced (over 20 K) near the center of the bed and near the outer wall.11... 

Choi et al. (2006) studied the intra-channel evolution of concentration and temperature profiles during regeneration of monolithic Pt/K/Al203 NSRC by CO in the presence of C02 and H20 and they observed two regeneration phases. The first one was related to the consumption of spare oxygen and evolution of corresponding exotherms caused by C0 + 02 and CO + NOx reactions, with N2 as major product of NOx reduction. The second one was characterized by the production of H2 (water gas shift) and NH3 as major product of NOx reduction. 

In this paper we will discuss the application of a general batch reactor model that considers the reaction kinetics, heats of reaction, heat transfer properties of the reactor, physical properties of the reactants and the products, to predict 1) The concentration profile of the products, thus enabling process optimization 2) Temperature profile during the reaction, which provides a way to avoid conditions that lead to a thermal runaway 3) Temperature profile of the jacket fluid while maintaining a preset reactor temperature 4) Total pressure in the reactor, gas flow rates and partial pressure of different components. The model would also allow continuous addition of materials of different composition at different rates of addition. 

Figure 5. Temperature profiles during the ignition of the C3H8-O2 reaction over 3% RI1/AI2O3. ycsns =0-02, yo2 =0.12, u= 3.3 cm/s.

The fee y-phase of Fe (austenite) is stable above 727°C but there is a euctectoid reaction at 0.76 wt% C, where the austenite transforms into bcc a-ferrite and FesC cementite. The lamellar structure of alternating layers of ferrite and cementite is called pearlite. Hypoeu-tectoid steels (steels with lower carbon content than the eutectoid composition) are called low carbon steels and are weaker but more ductile than the high carbon hypereutectoid steels. The strength and ductility of steels ako depends on the lamellar spacing of the pearlite, which can be controlled by time and temperature profiles during cooling. 

Recently, such a temperature oscillation was also observed by Zhang et al (27,28) with nickel foils. Furthermore, Basile et al (29) used IR thermography to monitor the surface temperature of the nickel foil during the methane partial oxidation reaction by following its changes with the residence time and reactant concentration. Their results demonstrate that the surface temperature profile was strongly dependent on the catalyst composition and the tendency of nickel to be oxidized. Simulations of the kinetics (30) indicated that the effective thermal conductivity of the catalyst bed influences the hot-spot temperature. 

Scheme 2.29 depicts two of the first examples of microwave-assisted carbonylation reactions7. In these reactions, the temperature controls the rate of the CO release. Thus, during heating at 150°C in sealed vessels, carbon monoxide was smoothly emitted from the molybdenum carbonyl complex into the reaction mixture (Fig. 2.1, Profile A). As a result, aryl iodides and bromides underwent efficient amino carbonylation with non-hindered, aliphatic, primary and secondary amines in only 15 min, using Herrmann s palladacycle as pre-catalyst7 (Scheme 2.29). In contrast, at a reaction temperature of 210°C, carbon monoxide was liberated almost instantaneously (Fig. 2.1, Profile B).

Since the methanation reaction is strongly exothermic, a sharp temperature rise can be measured across the reaction zone in the catalyst bed. Most methanation reactors are designed with a number of thermocouples that monitor the position of the exotherm. A strong indicator of the amount and rate of methanation catalyst deactivation is the position of the temperature profile in the catalyst bed and its rate of movement over time. A record of the temperature profile should be kept to detect any movement during the first one to two years of operation. An estimate of future life can then be made. ... 

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