Component continuous catalyst regeneration

The process consists of a reactor section, continuous catalyst regeneration unit (CCR), and product recovery section. Stacked radial-flow reactors are used to minimize pressure drop and to facilitate catalyst recirculation to and from the CCR. The reactor feed consists solely of LPG plus the recycle of unconverted feed components no hydrogen is recycled. The liquid product contains about 92 wt% benzene, toluene, and xylenes (BTX) (Figure 6-7), with a balance of Cg aromatics and a low nonaromatic content. Therefore, the product could be used directly for the recovery of benzene by fractional distillation (without the extraction step needed in catalytic reforming). 

Dehydrogenation of /i-Butane. Dehydrogenation of / -butane [106-97-8] via the Houdry process is carried out under partial vacuum, 35—75 kPa (5—11 psi), at about 535—650°C with a fixed-bed catalyst. The catalyst consists of aluminum oxide and chromium oxide as the principal components. The reaction is endothermic and the cycle life of the catalyst is about 10 minutes because of coke buildup. Several parallel reactors are needed in the plant to allow for continuous operation with catalyst regeneration. Thermodynamics limits the conversion to about 30—40% and the ultimate yield is 60—65 wt % (233). 

RTCP involves a reversible chain transfer (RT) process with a catalyst (Scheme 4a) that improves the dispersity control, as well as the mentioned small contribution of DT (Scheme Id). The catalyst can be, e.g., Af-iodosuccinimide (NIS) (Scheme 4a) [31], and works as a deactivator. Polymer (which is originally supplied by the conventional radical initiator) reacts with NIS to produce N-succinimide radical (NS ). NS works as an activator of Polymer-I to generate Polymer and NIS again. This cycle allows for frequent reversible activation of Polymer-I. This process is a reversible chain transfer of NIS that catalytically activates Polymer-I. Therefore, the polymerization was termed reversible chain transfer catalyzed polymerization (RTCP). Regarding the components used, RTCP is similar to initiators for continuous activator regeneration (ICAR)-ATRP [65]. Both systems use a monomer, a dormant species (alkyl iodide or alkyl bromide), a conventional radical initiator, and a deactivator [NIS or copper (II)] to regenerate a highly reactive activator [NS or copper (I)]. 

A lean NOx trap (LNT) (or NOx adsorber) is similar to a three-way catalyst. However, part of the catalyst contains some sorbent components which can store NOx. Unlike catalysts, which involve continuous conversion, a trap stores NO and (primarily) N02 under lean exhaust conditions and releases and catalytically reduces them to nitrogen under rich conditions. The shift from lean to rich combustion, and vice versa, is achieved by a dedicated fuel control strategy. Typical sorbents include barium and rare earth metals (e.g. yttrium). An LNT does not require a separate reagent (urea) for NOx reduction and hence has an advantage over SCR. However, the urea infrastructure has now developed in Europe and USA, and SCR has become the system of choice for diesel vehicles because of its easier control and better long-term performance compared with LNT. NOx adsorbers have, however, found application in GDI engines where lower NOx-reduction efficiencies are required, and the switch between the lean and rich modes for regeneration is easier to achieve. 

A schematic of a monolith catalyst is shown in Fig. 19-18a. In cases where pressure drop is limiting, such as for CO oxidation in cogeneration power plant exhausts, monolith catalyst panels may be stacked to form a thin (3- to 4-in-thick) wall. The other dimensions of the wall can be on the order of 35 x 40 ft. CO conversion is over 90 percent with a pressure drop across the catalyst of 1.5 in of water. Alternatively, the monolith may be used as a catalyst and filter, as is the case for a diesel particulate filter. In this case, monolith channels are blocked and the exhaust gases from a diesel truck are forced through the walls (Fig. 19-18b). The filter is a critical component in a continuous regenerable trap. NO in the exhaust... 

In addition, FBC [21] technology provides constant and continuously fresh ceria-based catalyst to the soot layer. This explains why, unlike many other catalyst-based DPF-regeneration technologies, the ceria-based fuel-borne catalyst is relatively insensitive to fuel-sulfur levels and is able to function with fuel containing over 2,500ppm of sulfur, as demonstrated in marine and stationary applications. However, in the presently described automotive application, the permissible level of sulfur is limited by the sulfur-sensitivity of other components of the complete DPF system. 

Figure 4-6 Three catalytic reactors in series. This unit is used for the continuous catalytic reforming of petroleum naphthas, a key element in the process of producing gasoline for automobiles. The catalyst is comprised of platinum and another metallic component on an acidic support The catalyst slowly moves downward through the reactors and is regenerated after it leaves reactor 3 at the bottom of the picture. The reactors themselves are radial-flow reactors, as discussed in Chapter 3. (Copyright 2004 UOP LLC. All lights reserved. Used with permission.)...

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