Second catalyst bed

For the integrated, two-zone, reactor design with differing catalyst compositions. Figure 2 illustrates the unit set-up. Here the first and second catalyst beds (A and B) are of different composition. 

DIPE yields of up to ca. 36% were achieved in example 10 using a 32% nickel-copper on 60% (i-zeolite/40% aliunina as the second catalyst bed, at 146°C. Unfortunately, in this case, there is also a 9.2% coproduction of light (C-1 plus C-2) gases (see column six), and if the etherification temperatures are raised still further (> 150 C), there is a deleterious effect on the combined IPA + DIPE yields (to < 80%) through the formation of additional undesired lights coproduct. 

The optimum temperature of the second catalyst bed was determined with the first catalyst bed operating at 430°C but with 7% rather than 3% water vapor. The effect of the second reactor temperature on the sulfurous content of the final exhaust gases is shown in Figure 7, curves a and b. The results indicate that this second catalyst is more... 

As an example of an ammonia synthesis converter, the Haldor Topsoe S-300 converter is illustrated in Figure 5. The ammonia synthesis converter consists of a pressure shell and a basket. The basket consists of three catalyst beds and two interbed heat exchangers placed in the centre of the first and second catalyst bed respectively. 

From the shell side of the first interbed heat exchanger, the gas is transferred to the second catalyst bed through the panels around the bed. The effluent from the second catalyst bed passes the shell side of the second interbed heat exchanger for cooling to the proper inlet temperature to the third catalyst bed by heat exchange with gas introduced to the tube side of the second interbed heat exchanger through the bottom inlet as described above. 

Several multicomponent metal oxide catalysts, developed for this process, have achieved excellent product selectivity with a high conversion of propene Mo-Bi-Fe-Co-M-K-O (M = V or W) used for the first step can attain >90% acrolein yields [6,7] while for the second step Mo-V-Cu-based oxides can lead to >97% acrylic acid yields [8,9], giving, in theory, an overall acrylic acid yield from propene of 87%. In addition to the compositional differences in fhe catalysis for the two-step process, there is also a difference in the optimal reaction temperatures 320-330°C for the first step and 210-255°C for the second step. One has to keep in mind that propene and oxygen can form an explosive mixture and therefore, certain limitations in the feed composition (propene oxygen (air) steam) exist. In addition, the acrylic acid easily dimerises at temperatures above 90 C, meaning that the reactor effluent should be quickly quenched after the second catalyst bed to temperatures below this critical value. 

First (feed gas) catalyst bed Second catalyst bed Third catalyst bed... 

This chapter describes gas cooling between first and second catalyst beds (Fig. 13.1). It sets the stage for Chapter 14 s examination of second catalyst bed SO2 oxidation. The objectives of this chapter are to ... 

Figure 13.1 Schematic of first and second catalyst beds with gas cooling between the beds. The cooling system cools first catalyst bed exit gas in preparation for more catalytic SO2 oxidation in a second catalyst bed. Industrial catalyst bed arrangements are discussed in Chapters 7 and 8. Gas cooling is discussed in Chapter 21.

Figure 13.2 First catalyst bed heatup path, equilibrium curve, and intercept point (Fig. 12.1). The first catalyst bed s exit gas is its intercept gas (Section 12.12). It is cooled and fed to a second catalyst bed for more SO2 oxidation.

Figure 13.3 Cooldown path added to Fig. 13.2. It is a horizontal line at the first catalyst bed intercept % SO2 oxidized level—between the first catalyst bed intercept temperature and the specified second catalyst bed gas input temperature. Gas composition and % SO2 oxidized do not change in the gas cooling equipment.

Cooldown target temperature s specified second catalyst bed gas input temperature 700 69.2 (unchanged during cooling without catalyst)... 

SO2 and O2 concentrations in the second catalyst bed input gas are lower than in the first catalyst bed feed gas (Section 12.2). SO3 concentration is higher. Both of these tend to slow SO2 oxidation in the second catalyst bed. 

This slowing effect is offset industrially by feeding slightly warmer input gas into the second catalyst bed (Fig. 13.1). 700 K is quite common (Table 7.2). It is also offset by using a slightly thicker second catalyst bed. 

Gas cooling between first and second catalyst beds is represented graphically by a... 

This chapter examines oxidation of the SO2 in cooled first catalyst bed exit gas—in a second catalyst bed. 

Figure 14.3 shows a second catalyst bed heatup path. It is similar to a first catalyst bed heatup path but it starts at Fig. 13.3 s ... 

Second catalyst bed heatup path points are calculated much like first catalyst bed heatup points. The steps are ... 

A significant difference between second catalyst bed input gas and first catalyst bed... 

Figure 14.1 Sketch of second catalyst bed showing a temperature measured part way down the bed. Compositions and temperatures are assumed to be uniform horizontally at all levels.

Figure 14.2 Sketch defining Section 14.4 s second catalyst bed heatup path problem.

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