manufacture of ethanol by passing steam over phosp
A mixture of ethene and steam is passed over phosphoric acid catalyst at a temperature of 300 degrees c and 60-70 atm of pressure.
C2H4(G) + H20(g) GOES TO C2H5OH(g)
Ethanol is condensed as a liquid.Ethene required for this reaction is obtained by crude oil.
manufacrure of ethanol by fermentation
Dissolve sugar and starch in water and add yeast.
Leave mixture to ferment at 25-40 degrees C for several days in absence of air.
Filter off the excess yeast to obtain a dilute solution of ethanol.
If the ethanol content in the mixture rises to around 15% , yeast is killed(only if more concentrated solution ; the mixture is fractionally distilled.
C6H12O6(AQ)GOES TO 2C2H5OH(AQ) + 2CO2(G)
Factors relevant to the fermentation of ethane
- Raw materials= renewable resources e.g. sugar cane.
- Type of process= batch process.
- Rate of reaction = very slow, takes several days for each batch.
- quality of product=produces a dilute solution of ethanol that needs further processing (if pure ethanol is required)
- reaction conditions-low temperatures required.
Dyhydration of ethanol to ethene using aluminium o
Pass ethanol vapour over hot aluminium oxide, this acts as a catalyst for the reaction.
This reaction can be used to maufacture ethene for the production of poly(ethene).
c2h5oh(g) goes to c2h4(g) + h2o(g)
Factors relevant to the dehydration of ethene
- Raw materials= non-renewable resources,crude oil will run out.
- type of process = continous process
- rate of reaction = fast
- quality of product= produces pure ethanol.
- Reaction conditions= high temperatures and pressure required , this increases cost.
How are long chain alkanes converterted to shorter
By catalytic cracking , silica or alumina catalyst and 600 -700 degrees C is ised to turn long hydrocarbons inro short chain hyrdorcarbons.
During this a mixture of alkenes and alkanes are fromed during catalytic cracking.
alkEnes and alkAnes
general formula =Cnh2n
Have carbon caron double bonds.
- ethene= c2h4
- propene c3h6
When bromine is shaken with ethene , ethene will be decolourised.
general formula cnh2n+2
don't have carbon carbon double bonds