Methane reacts with chlorine to produce methyl choride and hydrogen chloride. On
ID: 485143 • Letter: M
Question
Methane reacts with chlorine to produce methyl choride and hydrogen chloride. Once formed, the methyl chloride (CH3Cl) may undergo further chlorination to form methylene chloride (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4). A methyl chloride production process consists of a reactor, an condenser, a distillation column, and an absorption column. A gas stream containing 75.0 mole% methane and the balance chlorine is fed to the reactor. In the reactor, a single-pass chlorine conversion of essentially 100% is attained, the mole ratio of methyl chloride to methylene chloride in the product is 3.00:1.00, and negligible amounts of chloroform and carbon tetrachloride are formed. The product stream flows to the condenser. Two streams emerge from the condenser: the liquid condensate, which contains esstentially all of the methyl chloride and methylene chloride in the reactor effluent, and a gas containing the methane and hydrogen chloride. The condensate goes to the distillation column in which the two component species are separated. The gas leaving the condenser flows to the absorption column where it contacts an aqueous solution. The solution absorbs essentially all of the HCl and none of the CH4 in the feed. The liquid leaving the absorber is pumped elsewhere in the plant for further processing, and the methane is recycled to join the fresh feed to the process (a mixture of methane and chlorine). The combined stream is the feed to the reactor.
For a basis of 100.0 moles of reactor feed, calculate the following:
moles of fresh feed to the process:
mole fraction of Cl2 in the fresh feed:
moles of HCl removed from the absorber:
moles of methyl chloride produced:
moles in the recycle stream:
Explanation / Answer
For a basis of 100.0 moles of reactor feed, calculate the following:
CH4+Cl2 ---------àCH3Cl +HCl
CH3Cl+ Cl2--------àCH2Cl2+ HCl
Reactor feed contains 75 moles of CH4 and 25 moles of Cl2. Limiting reactant is Cl2. Hence all the Cl2 got consumed. Let x= moles of Cl2 consumed for producing CH3Cl.
25-x= moles of Cl2 used for producing CH2Cl2.
Hence moles of CH3Cl and HCl formed= x and moles of CH2Cl2 formed= 25-x
x/(25-x)= 3 hence x= 75-3x, 4x= 75 and x= 18.75
Products (Moles): CH3Cl = 18.75, CH2Cl2= 25-18.75= 6.25, CH4= 75-25= 50 moles/hr
HCl = 25
The feed is used to produce CH3Cl and CH2Cl2 hence moles of CH4 and Cl2 in fresh feed= 25 moles CH4 and 25 moles of Cl2.
Mole fraction of Cl2 in fresh feed= 25/(25+25)= 0.5
Feed entering the absorber= 50 moles CH4 and 25 moles HCl. Mole fraction of HCl = 25/(25+50)=0.333
Moles of CH4 in the recycle = 50