Ethanol Production

Question 1

Alcohols are produced by HYDRATION of …

Answer 1

ALKENES

Question 2

How do you produce alcohol from an alkene?

Answer 2

The standard industrial method for producing alcohols is to HYDRATE an ALKENE using STEAM in the presence of an ACID CATALYST. Equation:

CnH2n +H2O (equilibrium arrows H+) CnH2n+1OH

Question 3

Description of the general mechanism (more in the book)

Answer 3

A pair of electrons from the double bond bonds to the H+ from the acid.

A lone pair of electrons from a water molecule bonds to the carbocation.

The water loses an H+

And the alcohol is formed.

Question 4

How would you go about producing ethanol?

Answer 4

Ethanol can be produced by the HYDRATION of ETHENE by STEAM at 300 degrees and a pressure of 60atm.

It needs a solid PHOSPHORIC (V) ACID CATALYST.

Question 5

Ethanol can be produced industrially by …

Answer 5

FERMENTATION

Question 6

The ethene comes from …

Answer 6

cracking heavy fractions of crude oil.

Question 7

Name an industrial production of ethanol which uses a renewable raw material.

Answer 7

Industrial production of ethanol by fermentation of glucose

Question 8

How is fermentation carried out?

Answer 8

Fermentation is an EXOTHERMIC process, carried out by YEAST in ANAEROBIC CONDITIONS(without oxygen).
Equation: 30-40 degrees
C6H12O6 ————————> 2C2H5OH +2CO2
yeast

Question 9

Why is Yeast used in this reaction?

Answer 9

Yeast produces an ENZYME which converts sugars, such as glucose, into ETHANOL and CARBON DIOXIDE

Question 10

What is the ideal temperate for the yeast to function?

Answer 10

The enzyme works at an OPTIMUM (ideal) temperature of 30-40 degrees.

If it’s too cold the reaction is SLOW- if it’s too hot, the enzyme is DENATURED (damaged).

Question 11

How is ethanol separated?

Answer 11

Once formed, Ethanol is SEPARATED from the rest of the mixture by FRACTIONAL DISTILLATION.

Question 12

Why is fractional distillation an important step in fermentation?

Answer 12

Fermentation is LOW-TECH. It uses cheap equipment and RENEWABLE RESOURCES.

But the fractional distillation step that is needed to PURIFY the ethanol produced using this method takes extra time and money.

Question 13

Ethanol is what type of fuel?

Answer 13

BIOFUEL

Question 14

Give an example of a country which uses ethanol as fuel?

Answer 14

For example, in Brazil, SUGARS from sugar cane is fermented to produce alcohol, which is added to petrol.

Ethanol made in this way is a BIOFUEL (and sometimes called bioethanol)

Question 15

What is biofuel?

Answer 15

A biofuel is a fuel that’s made from biological materials that have recently died

Question 16

Biofuels have some advantages over fossil fuels (coal, oil and gas) and some potential drawbacks.

Advantage: Renewable

Answer 16

Biofuels are RENEWABLE energy sources. Unlike fossil fuels, biofuels won’t run out, so they’re more SUSTAINABLE.

Question 17

Biofuels have some advantages over fossil fuels (coal, oil and gas) and some potential drawbacks.

Advantage: Biofuels are carbon neutral

Answer 17

Biofuels do produce CO2 when they’re burnt, but its CO2 that the plants absorbed, so BIOFUELS are usually still classed as CARBON NEUTRAL.

Question 18

Biofuels have some advantages over fossil fuels (coal, oil and gas) and some potential drawbacks.

Disadvantage: Car engines have to be modified

Answer 18

One problem from switching from fossil fuels to biofuels in transport is that PETROL CAR ENGINES would have to be MODIFIED to use fuels with high ethanol concentrations.

Question 19

Biofuels have some advantages over fossil fuels (coal, oil and gas) and some potential drawbacks.

Disadvantage: Insufficient space

Answer 19

Also, when you use the land to grow crops for fuel, that land cant be used to grow FOOD.

If countries start using land to grow biofuel crops instead of food, they may be unable to feed everyone in the country.

Question 20

Bioethanol production is almost carbon neutral but not quite, why?

Answer 20

Just like burning the hydrocarbons from fossil fuels, burning ethanol produces CARBON DIOXIDE (CO2). Carbon dioxide is a GREENHOUSE GAS -it contributes to GLOBAL WARMING.

Question 21

Bioethanol production is almost carbon neutral but not quite, why? A reason for against.

Answer 21

But the plants that are grown to produce bioethanol TAKE IN CARBON DIOXIDE from the ATMOSPHERE when they’re growing.

As they grow, they take in the same amount of carbon dioxide as burning the bioethanol.

So it could be argued that burning ethanol as a fuel is CARBON NEUTRAL.

Question 22

Chemical equations to support the argument that biofuels are carbon neutral.

Answer 22

Plants take in CARBON DIOXIDE from the atmosphere to produce GLUCOSE by PHOTOSYNTHESIS.

6CO2 + 6H2O —> C6H12O6 + 6O2
(6 MOLES of CARBON DIOXIDE are TAKEN from the atmosphere to produce 1 MOLE of GLUCOSE)

in the FERMENTATION process, GLUCOSE is converted into ETHANOL:

C6H12O6 —> 2C2H5OH + 2CO2
(2MOLES of CARBON DIOXIDE are RELEASED into the atmosphere when 1 MOLE of GLUCOSE is converted into 2 moles of ETHANOL)

When ETHANOL is BURNED, CARBON DIOXIDE and water are produced:

2C2H5OH + 6O2 —> 4CO2 + 6H2O
( 4moles of carbon dioxide are released into the atmosphere when 2 moles of ethanol are burned completely)

If you COMBINE all three equations, you’ll find exactly 6 MOLES OF CO2 is taken in and exactly 6 moles are given out.

Question 23

Bioethanol production is almost carbon neutral but not quite, why? reason for agree

Answer 23

However, FOSSIL FUELS will need to be burned to power machinery to make FERTILISERS for the crops, HARVEST THE CROPS and refine and TRANSPORT the bioethanol.

Burning the fuel to power the machinery produces carbon dioxide. So bioethanol made by fermentation ISNT COMPLETLY CARBON NEUTRAL.