Tandem reactor process

Fig. 7.5. Tandem reactor concept for single-stage, high-conversion Claus process with integrated elutive regeneration.

Table 4.14 Comparative properties of bimodal HMW-HDPE prepared in a single reactor and tandem slurry process.

Single Reactor (Ti/Zr Catalyst) Tandem Slurry Process Ti-based Catalyst... 

Several polymerization processes use only one reactor, but two or more reactors can also be operated in series (tandem reactor technology) to produce polyolefins with more complex microstructures [5]. Each reactor in the series is maintained under different operating conditions to produce products that are sometimes called reactor blends . Although, in principle, the post-reactor blending of different resins could lead to the same product, in reactor blends the chains are mixed on the molecular scale, permitting better contact between the polymer chains made in different reactors at a lower energy cost. 

Another example of the retention of volatile DA reagents is that of cyclopentadiene in a tandem retro-DA/DA prime reaction [15, 16, 38], This reaction type is the thermal decomposition of a DA adduct (A) and the generation of a diene (generally the initial diene) which is trapped in situ by a dienophile leading to a new adduct (B) [39]. Cyclopentadiene (22) (b.p. 42 °C) is generated by thermolysis of its dimer at approximately 160 °C [40]. An equimolar mixture of commercial crude dicyclopenta-diene (21) and dimethyl maleate was irradiated in accordance with the GS/MW process, in an open reactor, under 60 W incident power, for 4 min (8 x 30 s). The expected adduct 23 was isolated in 40% yield (Scheme 7.1). The isomeric composition of 23 (endo-endoIexo-exo = 65/35) was identical with that obtained under classical conditions from 22 and methyl maleate [41]. The overall yield of this tandem reaction can be increased from pure dimer 21 (61%) and the same tandem reaction has also been reported using ethyl maleate as dienophile [31]. 

The use of two or more different catalysts in the same reactor, sometimes known as in situ reactor blending or tandem catalysis, has been widely employed industrially as means of controlling the properties of a polyolefin (e.g. molecular weight and the molecular weight distribution). Recent years have seen a variety of reports emerge on the use of bis(imino)pyridine iron/cobalt systems as one component of the process [169, 170, 171, 172, 173, 174, 175, 176, 177,178, 179],... 

The general concept of the facility was developed based on experience gained from commercialisation of a two-stage steam-oxygen conversion process with TANDEM scheme, as well as on experience in developing the process with VG-400 high-temperature helium reactor (Kostin, 2005 Mitenkov, 2004 Ponamarev-Stepnoi, 2008 Stolyarevsky, 1988). 

The final concern we have about the control structure in Fig. 5.16 is how to start up and turn down the plant. For example, how would we start up the columns without running the furnace and the reactor Also, how could we turn off the heat to any of the reboilers when the reactor and the furnace are running The bypass valves may not be designed to take the full gas stream when fully opened. This implies that we need two control valves working in tandem around each reboiler or a three-way valve. Neither of those options is particularly attractive. See Jones and Wilson (1997) for further discussions on process flexibility related to heat integrated designs. 

Qmdntpole Ion Trap with an External Thermionic Source By the use of mass-selective instabihty experiments, the ion trap mass spectrometer serves as both a reactor in which ion/molecule reactions occur, and a mass analyzer for the products of these reactions. The analytical use of ion trap mass spectrometers relies upon the method of ramping the radio frequency (RF) drive potential. The capabilities of ion traps to perform attachment reactions with alkali cations using classical scanning sequences have been exploited. Kinetic studies have shown that, the attachment efficiency is very high, near-collision efficiency, and illustrate how the present method is particularly well suited for ion trap mass spectrometers. Control of the attachment process may be readily performed by the use of a classical ionization sequence in some aspects similar to a tandem MS/MS scanning sequence. 

The oldest example of this procedure is the manufacture of high-impact polypropylene, as already described (see Section 8.1.2). Other applications have become more popular lately, especially for the production of bimodal resins. Figure 8.36 illustrates a tandem process using two gas-phase vertical stirred-tank reactors. Several other reactor combinations are used industrially [65]. For heterogeneous processes, the first reactor(s) in the series can be either slurry or gas-phase, but commonly the second reactor (or set of reactors) is a gas-phase reactor. This is especially important when the production of polymers with lower crystallinity... 

The Tandem process developed in Russia also makes use of two reactors, a feature that allows it to more efficiently combine the processes of steam reforming and partial oxidation [320]. The Syntroleum has developed a process of ATR of natural gas with oxidation by air as a cheaper method of producing syngas at medium-capacity plants with a production capacity in GTL-products beginning from 2000 bbl/day. 

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