Unreactive

Achieving complete conversion of FEED to PRODUCT in the reactor usually requires an extremely long residence time, which is normally uneconomic (at least in continuous processes). Thus, if there is no byproduct formation, the initial reactor conversion is set to be around 95 percent, as discussed in Chap. 2. The reactor effluent thus contains unreacted FEED and PRODUCT (Fig. 4.1a). 

Because we require a pure product, a separator is needed. The unreacted FEED is usually too valuable to be disposed of and is therefore recycled to the reactor inlet via a pump or compressor (see Fig. 4.16). In addition, disposal of unreacted FEED rather than recycling creates an environmental problem. 

An additional separator is now required (Fig. 4.2a). Again, the unreacted FEED is normally recycled, but the BYPRODUCT must be removed to maintain the overall material balance. An additional complication now arises with two separators because the separation sequence can be changed (see Fig. 4.26). We shall consider separation sequencing in detail in the next chapter. 

Incomplete conversion in the reactor requires a recycle for unreacted feed... 

In practice, there is likely to be a trace of decane in the reactor eflfluent. However, this should not be a problem, since it can either be recycled with the unreacted chlorine or leave with the product, monochlorodecane (providing it can still meet product specifications). 

Again, in practice, there is likely to be a trace of chlorine in the reactor effluent. This can be recycled to the reactor with the unreacted decane or allowed to leave with the hydrogen chloride byproduct (providing this meets with the byproduct specification). 

The effluent from the reactor contains both PRODUCT and unreacted FEED which must be separated in a distillation column. Unreacted FEED is recycled to the reactor via a pump if the recycle is liquid or a compressor if the recycle is vapor. 

Detonation. In a detonation, the flame front travels as a shock wave, followed closely by a combustion wave, which releases the energy to sustain the shock wave. The detonation front travels with a velocity greater than the speed of sound in the unreacted medium. 

If it is not possible for some reason to recycle unreacted feed... 

If the separation and recycle of unreacted feed material is not a problem, then we don t need to worry too much about trying to squeeze extra conversion from the reactor. 

Some small amount of byproduct formation occurs. The principal byproduct is di-isopropyl ether. The reactor product is cooled, and a phase separation of the resulting vapor-liquid mixture produces a vapor containing predominantly propylene and propane and a liquid containing predominantly the other components. Unreacted propylene is recycled to the reactor, and a purge prevents the buildup of propane. The first distillation in Fig. 10.3a (column Cl) removes... 

Increasing reactor conversion when separation and recycle of unreacted feed is difficult. 

Although benzene contains three carbon-carbon double bonds, it has a unique arrangement of its electrons (the extra pairs of electrons are part of the overall ring structure rather than being attached to a particular pair of carbon atoms) which allow benzene to be relatively unreactive. Benzene is, however, known to be a cancer-inducing compound. 

MMVB is a hybrid force field, which uses MM to treat the unreactive molecular framework, combined with a valence bond (VB) approach to treat the reactive part. The MM part uses the MM2 force field [58], which is well adapted for organic molecules. The VB part uses a parametrized Heisenberg spin Hamiltonian, which can be illustrated by considering a two orbital, two electron description of a sigma bond described by the VB determinants... 

Krypton is found to be an extremely unreactive element indicating that it has a stable electronic configuration despite the fact that the n = 4 quantum le el can accommodate 24 more electrons in the d and / orbitals. 

The electrode potential of aluminium would lead us to expect attack by water. The inertness to water is due to the formation of an unreactive layer of oxide on the metal surface. In the presence of mercury, aluminium readily forms an amalgam (destroying the original surface) which is. therefore, rapidly attacked by water. Since mercury can be readily displaced from its soluble salts by aluminium, contact with such salts must be avoided if rapid corrosion and weakening of aluminium structures is to be prevented. 

Boron nitride is chemically unreactive, and can be melted at 3000 K by heating under pressure. It is a covalent compound, but the lack of volatility is due to the formation of giant molecules as in graphite or diamond (p. 163). The bond B—N is isoelectronic with C—C. 

It is slightly soluble in water, giving a neutral solution. It is chemically unreactive and is not easily oxidised or reduced and at room temperature it does not react with hydrogen, halogens, ozone or alkali metals. However, it decomposes into its elements on heating, the decomposition being exothermic ... 

Concentrated nitric acid renders the metal passive , i.e. chemically unreactive, due to formation of a thin oxide surface film (which can be removed by scratching or heating in hydrogen). 

A halogen atom directly attached to a benzene ring is usually unreactive, unless it is activated by the nature and position of certain other substituent groups. It has been show n by Ullmann, however, that halogen atoms normally of low reactivity will condense with aromatic amines in the presence of an alkali carbonate (to absorb the hydrogen halide formed) and a trace of copper powder or oxide to act as a catalyst. This reaction, known as the Ullmant Condensation, is frequently used to prepare substituted diphenylamines it is exemplified... 

The aliphatic hydrocarbons are extremely unreactive and do not respond to any of the following tests for aromatic hydrocarbons. 

Acetaldehyde, b.p. 21°, undergoes rapid pol5unerisation under the influence of a little sulphuric acid as catalyst to give the trimeride paraldehyde, a liquid b.p. 124°, which is sparingly soluble in water. The reaction is reversible, but attains equilibrium when the conversion is about 95 per cent, complete the unreacted acetaldehyde and the acid catalyst may be removed by washing with water ... 

Pinacol possesses the unusual property of forming a crystalline hexahydrate, m.p. 45°, and the pinacol is separated in this form from the unreacted acetone and the tsopropyl alcohol. The magnciaium is conveniently amalgamated by dissolving mercuric chloride in a portion of the acetone mercury is then liberated by the reaction ... 

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