Reactive entrainer

Fig. 3.2 shows the flow diagram of such a reactive-separation process [1]. An isobutene-containing stream, for example raffinate I, is fed to a standard MTBE synthesis plant, where the reactive component isobutene is converted to the intermediate MTBE while the inert C4 components are separated as distillate. Pure MTBE enters a second RD column and is decomposed. Isobutene, as the low-boiling component, is recovered at the top, while the bottom product methanol, acting as a reactive entrainer, is recycled to MTBE synthesis. 

There are two distinct categories of reactive separations. In one category, the reaction aids separation and in the other separation aids the reaction. In the former, decreasing or eliminating the mass-transfer resistance on the liquid side by allowing the solute to react with a non-volatile non-diffusing component as in the absorption of CO2 into an amine solution enhances the mass-transfer rate. Absorption with reaction has been practised for the removal of CO2 and H2S over the past several decades, and an extensive literature is available. Similarly, in distillation, reactive entrainers are used to separate close boiling or azeotropic mixtures [19]). 

Jiir-entraining cements produce concretes that protect the concrete from frost damage. They are commonly used for concrete pavements subjected to wet and freezing conditions. Cement of low alkah content may be used with certain concrete aggregates containing reactive siUca to prevent deleterious expansions. 

Catalysts developed in the titanium-aluminum alkyl family are highly reactive and stereoselective. Very small amounts of the catalyst are needed to achieve polymerization (one gram catalyst/300,000 grams polymer). Consequently, the catalyst entrained in the polymer is very small, and the catalyst removal step is eliminated in many new processes. Amoco has introduced a new gas-phase process called absolute gas-phase in which polymerization of olefins (ethylene, propylene) occurs in the total absence of inert solvents such as liquefied propylene in the reactor. Titanium residues resulting from the catalyst are less than 1 ppm, and aluminum residues are less than those from previous catalysts used in this application. 

Certain halides, notably fluorides, are comparatively inert under these reaction conditions. In such cases the entrainment method, can be used, and reduction can be accomplished in the presence of a reactive halide such as 1-bromonaphthalene or 1-bromobutane. Also with certain halides, such as chlorocyclo-hexane, the tendency for dehydrohalogenation is diminished by the use of such entraining agents. 

The anion of nitromethane is particularly reactive in S l reactions. Various kinds of tertiary nitro groups are replaced by a nitromethyl group on treatment with the anion of nitromethane (Section 7.1).49 2-Iodoadamantane reacts with the anion of nitromethane in the presence of acetone enolate (entrainment reaction) under irradiation of a 400-W UV lamp to give 2-ni-tromethyladamantane in 68% yield, (see Eq. 5.32).50a 1-Iodoadamantane also reacts with the anion of nitromethane in a similar way.50b... 

A potential source of particulates is char formed when the biomass feedstock is incompletely gasified. These particles undergo devolatilization and subsequent reactions at gasification temperatures that leave them less reactive than fresh biomass feedstock. They can pass through the gasifier before they are completely gasified, particularly in those configurations with turbulent beds. Char entrained in the product gas also represents unconverted biomass that contributes to lower conversion efficiencies. 

The residence time rCd = rH/aCd and the limiting concentration CinCd/aCd are divided by a factor of 30 relative to a non-reactive case, e.g., chlorine. Entrainment by sediments flushes the excess Cd 30 times faster and decreases Cd steady-state concentration 30 times relative to a sediment-free lake. [Pg.351]

One important feature of ion-radical organic reactions consists of a possibility to nudge them by the introduction of active reactants. Thus, in the reaction of an electron acceptor with electron donors (nucleophiles), the addition of a tiny amount of a nucleophile, which is more active at initiation of the one-electron transfer allows the less reactive nucleophile to start its own chain propagation. A method called entrainment is widely used in chemical practice as a recent example (see Schmidt et al. 2007). 

We have modified the SNCR reaction mechanism from the previous problem to include the simple mixing description (SNCRmix.mec). Here the entrainment of the reactive components of the flue gas (NO and O2) into the NH3/carrier jet (inverse mixing) is described by the two pseudo reactions,... 

Reformatsky reactions have a bad reputation as being difficult to entrain. To the authors experience, however, the reactive donors such as alkyl bromo-acetates do not pose particular problems even under rather conventional conditions. Commercial zinc dust activated by pre-treatment with either iodine of preferentially with cuprous chloride (i.e. Zn(Cu)) readily inserts into these halocarbonyl compound with formation of the corresponding zinc enolates. Protocols 1 and 2 describe prototype examples for Reformatsky reaction in the conventional two-step or Barbier-type set-up, respectively. 

Hydrolytic cocondensation is carried out in enameled hydrolyser 7 with a water vapour jacket and an agitator. The hydrolyser is filled with a required amount of water then, under the water layer, the reactive mixture is sent through a siphon from batch box 6. The temperature during hydrolytic cocondensation should not exceed 50-55 °C. Most of the released hydrogen chloride dissolves in the water in the apparatus, and the excess of HC1 passes through backflow condenser 8 and enters tower 9, where is absorbed by water. The vapours of water and reaction products, which are entrained by hydrogen chloride and condensed in the backflow condenser,... 

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