E4.6-3 Yield and Selectivity in a Dehydrogenation The reactions take place in a continuous reactor at steady state. The feed contains 85.0 mole% ethane and the balance inerts (1). The fractional conversion of ethane is 0.501, and the fractional vi) ethylene is 0.471. the to methane production. ethylene e producifnlate the molar composition of the product gas and the selctivity of etnld e Basis: 100 mol Feed 100 mol 0.850 mol C2He/mol 0.150 mol Umo! し ,ri (mol C2H6) ,12 (mol C2H4) n3 (mol H2) n4 (mol CH4) ns (mol )

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E4.6-3 Yield and Selectivity in a Dehydrogenation The reactions take place in a continuous reactor at steady state. The feed contains 85.0 mole% ethane and the balance inerts (1). The fractional conversion of ethane is 0.501, and the fractional vi) ethylene is 0.471. the to methane production. ethylene e producifnlate the molar composition of the product gas and the selctivity of etnld e Basis: 100 mol Feed 100 mol 0.850 mol C2He/mol 0.150 mol Umo! し ,ri (mol C2H6) ,12 (mol C2H4) n3 (mol H2) n4 (mol CH4) ns (mol )

EXPERT ANSWER

given data

feed F=100 mol

mole fraction of ethane in feed xethane = 0.85                 moles of ethane in feed = xethane F =85 mol

moles fraction of inert xi =0.15                               moles of inert in feed=xiF=15mol

fractional convertion of ethane Xe = 0.501   =reacted ethane/total ethane in feed

therefore reacted ethane=0.501*85=42.585mol

unreacted ethane=85-42.585=42.415

fractional Yield of ethylene Yethylene=0.471=ethane reacted to produce ethylene/moles of ethane totally reacted

0.471=ethane reacted to produce ethylene/42.585

ethane reacted to produce ethylene=0.471*42.585=20.057535

each 1 mole of ethane reacted to produce ethylene will produce 1mol of ethylene

therefore ethylene produced=20.057535

remaining moles of reacted ethane will react to produce methane=42.585-20.057535=22.527465

1mol of ethane will produce 2 mols of methane           …… from reaction

therefore methane produced= 2*22.527465 =45.05493

from reaction stoichiometry hydrogen is getting produced and reacted for methane

hydrogen in P stream = hydrogen produce – hydrogen reacted

hydrogen produce=ethylene produce from stoichiometry=20.057535

hydrogen reacted=half the amount methane produced =45.05493/2=22.527465

hydrogen in P stream=20.057535-22.527465=-2.46993

here should be problem in given data as this value comes negative

molar composition of product gas                                                      ans.

componentcomposition of P stream (moles)
n1 ethane42.415    (unreacted)
n2 ethylene20.057535    (produced)
n3   hydrogen-2.46993
n4   methane45.05493       (produced)
n5   inert15          (from feed)

selectivity of ethylene to methane

=moles of ethylene formed/moles of methane formed

=20.057535/45.05493

=0.445179                                                ans.