Aromatics Oligomers By- products Figure I. General mechanism for the aromatizati

Question

Aromatics Oligomers By- products Figure I. General mechanism for the aromatization of alkanes While the general mechanism of this process is well-known, only three stoichiometric equations of the conversion of ethane to benzene, toluene and xylene could be found'. Otherwise, no information could be found on the exact stoichiometry or the kinetics of the steps. Table 2 shows the chemical equations that have been proposed for the project and the components of the reactor effluent were assumed to be the same as the results provided in US Patent 209,795' and US Patent 324,778 Table 2. Reaction network and heat of reaction per mass of C2 or C3 hydrocarbon consumed. Note that the reactions tric equations of the in which ethane and are consumed areendotherm AH BTU/lb of C2 or C3 consumed -3.8 8.04 5,76 0.905 5.92 4,60 4.61 7.56 13,3 2.56 8,03 2.38 3,87 3.86 0,543 3.08 2.21 1.70 4.86 Reaction Number Stoichiometric Reaction 10 14 16 17 18 19 20 21 1.07 0.104 23 24 1,97

Explanation / Answer

Enthalpy of the given transformation i.e. chemical reaction is given as,

H = Hf0(products) - Hf0(reactants).

Where, Hf0 is standard enthalpy of formation of that particular compound from constituent elements. Hf0 values for various compounds one can find in thermodynamic tables generally given in any Thermodynamics book.

e.g. Reaction -1 C2H6(g) + H2(g) --------> 2CH4 (g)

For this reaction, Hrxn = ?

Formula,

Hrxn = Hf0(products) - Hf0(reactants)

Hrxn = [2 x H0f(CH4)] – [Hf0(H2) + Hf0(C2H6)]. ……… (1)

H0f(CH4) = -74.87 kJ/mol

Hf0(C2H6) = -83.7 kJ/mol

Hf0(H2) = 0.0 kJ/mol

Let us put these values in eq.(1) and calculate Hrxn

Hrxn =[2 x (-74.87)] – [0+ (-83.7)]

Hrxn = -149.74 + 83.7

Hrxn = -66.04 kJ/mol

Convert it to BTU/Ib unit.

Hrxn = -3.81 BTU/Ib.

In similar way one can find out Hrxn for rest reactions.

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