Question

Q7. Food companies began using hydrogenated oil to help increase shelf life and save costs. Partially hydrogenated oils can affect heart health because they increase “bad” cholesterol and lower “good” cholesterol. On the other hand, a fully hydrogenated oil does not carry the same health risks as partially hydrogenated oils. Still, food manufacturers continue to use partially hydrogenated oils to save money, extend shelf life, add texture & increase stability. Partially hydrogenated oil is not always easy to spot, but there are ways to spot it and avoid it.

a. Identify the type of reaction taking place during hydrogenation. What are the reaction conditions? (1.5 marks)

b. How hydrogenation was made an economically viable process? (1 mark)

c. What is the role of a catalyst in hydrogenation process? Identify the type of catalysis observed in the above reaction. (1.5 marks)

d. It is observed that the catalyst gets deactivated to some extent during the process of catalysis. Think of a reason and state it. (1 mark)

e. What is the undesirable effect of partial hydrogenation? Is the product formed on complete hydrogenation safer? (1 mark) 11

f. What does the term bad cholesterol and good cholesterol refer to in the above information? (1 mark)

g. How partial hydrogenation leads to change in texture and increased stability of oil? (1 mark)

h. Critically analyze the data that is given below and choose a better catalyst for the process of hydrogenation. Support your answer with the evidence from the given data. (2.5 marks) Basis of comparison Catalyst A Catalyst B

Catalyst requirement (lb of metal/100 lb of oil) 0.1 (1000 ppm) 0.01 (100 ppm)

Support medium — Carbon

Reaction temperature (°C) 140°C 60°C

Reaction pressure (bar) 10 10

Reaction time (min) 10 42

Stearic acid (%) 6.8 12.8

Linoleic acid (%) 1.7 3.0

Trans fatty acid (%) 18.8 8.5

Answer 1

a)h During hydrogenation the unsaturated double bonds in the fatty acids of oil molecules react with hydrogen atoms in the presence of a catalyst .It is essentially reduction of an unsaturated bond into a bond with a lower degree of unsaturation or to a saturated bond .i.e. a triple bond to a double or a single bond depending on the extent of hydrogenation or of a double bond to a single bond . catalysts are required to ease the process. Non catalytic hydrogenation takes place only at high temperatures essentially hydrogenation reduces triple and double bonds in the hydrocarbons .

b)An unhydrogenated oil can go rancid as the unsaturated carbon atoms are free to bond to oxygen atoms from the air forming peroxides which give an off flavour . The catalyst involved will adsorb both the oil and the hydrogen gas on its surface and makes the process more energetically feasible .This allows the reaction to proceed at a fast enough rate to be useful .Raney nickel when finely divided allows for this process to occur in an economically prospective manner .

c) a catalyst lowers the activation energy of a reaction .here specifically,it provides a reaction surface for the reaction mixture to adaorb on ,and thus enabling product formation at a lower temperature. Raney nickel or platinum or palladium (when in finely divided state to produce more surface area for reaction ) can act as a catalyst .

d) the activity of this catalyst is determined by the amount of surface it has free to adsorbtion . Sometimes these sites get clogged up and hence render unreactive .

e) traces of unsaturation left opens up a place for carbon to react with oxygen and go bad .the product goes rancid quicker .Complete hydrogenation will prevent thos fr occuring .