DD15 PANDEY SHESHANKSHEKHAR BINOD DD16 PARAMAR SATISHBHAI RAJUBHAI DD17 PATEL BHARTKUMAR SUBHSHBHAI DD18 PATEL BHUMIKABEN JESANBHAI DD19 PATEL RAHULKUMAR HASMUKHBHAI DD20 RABARI RAHUL GOVINDBHAI DD21 RANA AMITKUMAR RAJNIKANT DD22 RANA VISHALKUMAR PUNAMBHAI GUID BY : PROF. ANJALI PRAJAJPATI

Material Balances Involving Reactive Processes

DEFINATION AND TERMINOLOGY  Chemical reaction equations: Chemical reactions do not create, destroy, or convert atoms. Therefore, the quantities of each type of atom on the two sides of a chemical reaction equation must be the same. In other words, chemical reaction equations must be stoichiometrically balanced.  Stoichiometric coefficient: of a reacting species is the numeric prefactor of the species in the chemical reaction equation.

 Stoichiometric ratio: is the ratio of the stoichiometric coefficients of two species involved in a chemical reaction. This ratio is useful for calculating how much of a reactant (or product) is consumed (or produced) relative to the consumption or production of the other species.  Stoichiometric proportion: Two chemical species participating in the same chemical reaction are in stoichiometric proportion if their actual amounts present are in the same proportion as their stoichiometric coefficients. In the case that all reactants are present in stoichiometric proportion, if the reaction proceeds to full conversion there will be no reactant molecules (of any type) left.

 Limiting reactant : Usually reactants are not present in stoichiometric proportion. In that case, if the reaction proceeds sufficiently far, one of the reactants will be the first to be used up. That reactant is the limiting reactant. The other reactants are excess reactants.  Stoichiometric requirement: The amount of an excess reactant that would be needed to completely react with the limiting reactant  Fractional conversion: the fraction of reactant that has reacted. Fractional conversion =(moles reactant reacted)/(moles reactant fed in)

 Percentage conversion: (fractional conversion) × 100 consider the chemical reaction: A + B C now, %conversion of A = {(mol of A reacted)/(mol of A fed)}* 100  Yield: Reactions, in general, do not go to 100% conversion of the reactant into the desired product. This is because of side reactions taking place as well as thermodynamic limitations (see below). “Yield” is used to measure how effective a reaction is in converting reactant to the desired product. It has several possible definitions, so it is important to always note which one is being used consider the reaction: A + B C and C + B D Yield of C = {(mol of A reacted to produce C)/(mol of A totally reacted)}100

 Selectivity: Selectivity measures how effective a reaction is in producing the desired product relative to undesired products that result from side reactions. Consider the reaction: A C and A D selectivity of C relative to D= moles of C formed/moles of d formed where, C is desire product and D is undesire product

Material balances on processes involving chemical reactions may be solved by applying: 1. Molecular Species Balance - a material balance equation is applied to each chemical compound appearing in the process. 2. Atomic Species Balance - the balance is applied to each element appearing in the process. 3. Extent of Reaction - expressions for each reactive species is written involving the extent of reaction.

For steady-state reactive processes, Input + Generation = Output + Consumption The generation and consumption terms in the molecular balance equation is usually obtained from chemical stoichiometry. But for an atomic balance, for all cases Input = Output

Dehydrogenation of Ethane Consider the dehydrogenation of ethane in a steady-state continuous reactor,

Dehydrogenation of Ethane Total Balance: Molecular Species Balance: C2H6:C2H6: C2H4:C2H4: H2:H2: Input = Output Input - Consumed = Output Generated = Output Generated = Output Atomic (Elemental) Species Balance: C-Balance: H-Balance:Input = Output

Example :- Production of Ethyl Bromide The reaction between ethylene and hydrogen bromide to form ethyl bromide is carried out in a continuous reactor. C 2 H 4 + HBr =====> C 2 H 5 Br The product stream is analyzed and found to contain 51.7 mole% C2H5Br and 17.3% HBr. The feed to the reactor contains only ethylene and hydrogen bromide. Calculate the fractional conversion of the limiting reactant and the percentage by which the other reactant is in excess. If the molar flow rate of the feed stream is 165 mol/s, what is the extent of reaction?