Reactor temperature catalyst profile

Catalytic reactors can roughly be classified as random and structured reactors. In random reactors, catalyst particles are located in a chaotic way in the reaction zone, no matter how carefully they are packed. It is not surprising that this results in a nonuniform fiow over the cross-section of the reaction zone, leading to a nonuniform access of reactants to the outer catalyst surface and, as a consequence, undesired concentration and temperature profiles. Not surprisingly, this leads, in general, to lower yield and selectivity. In structured reactors, the catalyst is of a well-defined spatial structure, which can be designed in more detail. The hydrodynamics can be simplified to essentially laminar, well-behaved uniform fiow, enabling full access of reactants to the catalytic surface at a low pressure drop. 

Figure 16 Simulated temperature profiles along a reactor with and without "desorptive" cooling at various times for the oxidation of CO on a Pt catalyst with water vapor desorption from 3A zeolite in a fixed bed comprising equal proportions of catalyst and adsorbent. The solid curves give the simple regenerative behavior and the dotted curves describe the desorptively cooled case. Initial reactor temperature is 125°C, initial adsorbent loading 0.12 kg/kg, inlet CO-concentration 0.2 mol/l, gas loading 6000 h-1.

Exploration for an acceptable or optimum design for a new reactor may require consideration of several feed and product specifications, reactor types, catalysts, operating conditions, and economic evaluations. Modifications to an existing process likewise may need to consider many cases. Commercial software may be used to facilitate examination of options. A typical package can handle a number of reactions in various ideal reactors under isothermal, adiabatic, or heat-transfer conditions in one or two phases. Outputs can provide profiles of composition, pressure, and temperature as well as vessel size. 

Figure 25. Equivalence of operation with periodical flow re versa and countercurrent heat exchange A) Fixed-bed reactor with periodic flow reversal, B) Temperature profiles with rapid flow reversal, C) Countercurrent reactor with catalyst at the wall D) Schematic concentration and temperature profiles m both reactors [141...

Using equilibrium catalyst from commercial FCC units, we modified the MAT reactor conditions in order to meet the simulation criteria. This work was complemented with ARGO pilot riser plant tests, exploring the influence of the main process parameters such as residence time, mixing, reactor temperature and temperture profile. 

The reactor is modeled in 10 sections in the axial direction. The reactor temperature profile is shown in Fig. 11.26. The flowsheet design conditions are for a new catalyst with an activity of 1. However, the... 

Description A single jacketed fixed-bed reactor removes the heat of the reaction by producing high-pressure steam. The process is carried out with a large ethylene excess. The flexibility of catalyst staging, reactor temperature profiles, and feed flowrates with EVC s single reactor system, produces maximum throughput with minimal byproducts. After condensation and separation of the reaction products (EDC and water), excess ethylene is compressed and recirculated. 

Total conversion yields of the temperature range 345-460 C at 6 MPa hydrogen are summarized in Figure 1. Absolute conversions are lower than for work with 1 liter autoclaves and the continuous reactor unit because of different reactor temperature profiles and residence time however, the qualitative conclusions are consistent. The effect of increasing the reaction temperature was to increase the total conversion of all reactions irrespective of the catalyst system. 

Figure 3.4. Typical temperature profile of a CPO reactor with concentration profiles of fuel and 02 along a CPO catalyst bed.

A gas-phase exothermic reaction is carried out in a multitube reactor with the catalyst in 1-in. tubes and boiling water in the jacket. The feed temperature and the jacket temperature are 240°C. The average reactor temperature rises to 250°C a short distance from the inlet and then gradually decreases to 241°C at the reactor exit. The resistance to heat transfer is about equally divided between the bed and the film at the wall. If the tube diameter were increased to 1.5 in. with the same catalyst, what should the jacket temperature be to keep the peak reactor temperature at 250°C Sketch the temperature profiles for the two cases. What pressure steam would be generated for the two cases ... 

In the laboratory tests, two gas mixtures at two space velocities were used. Each gas mixture contained 1% CO, 250 ppm (molar) hydrocarbon, 2.5% 02, and 10% H20 the remainder was N2. The hydrocarbon was propane or propylene. The flow rate was 5000 cm3/min at standard temperature and pressure (STP). With a catalyst bed of 20 cm3 (% X 2 in.), the gas hourly space volume (GHSV) at STP was 15,000/hr with a bed of 2 cm3 (7/s X in.), it was 150,000/hr. The test consisted of lining out the system at 538°C inlet, and following the temperature-conversion profiles while the reactor cooled until the conversions of both HC and CO were below 25%. Lined-out conversions were then obtained at 288°C and 538°C. 

In a fixed-bed reactor the catalyst pellets are held in place and do not move with respect to a fixed reference frame. Material and energy balances are required for both the fluid, which occupies the interstitial region between catalyst particles, and the catalyst particles, in which the reactions occur. For heterogeneously catalyzed reactions, the effects of intraparticle transport on the rate of reaction must be considered. Catalytic systems operate somewhere between two extremes kinetic control, in which mass and energy transfer are very rapid and intra-partide transport control, in which the reaction is very rapid. Separate material and energy balances are needed to describe the concentration and temperature profile inside the catalyst pellet. The concentrations... 

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