Biomass Research Flashcards
Explain what is meant by a condensation polymer
describe the reaction involved when a condensation polymer is formed
A condensation polymer is formed by monomer molecules condensing out small molecules (such as water) as the polymer chain forms.
For example, when two glucose monomer molecules react through two hydroxy groups -OH, an H-OH molecule is condensed out, leaving an -O- linking the two monomer molecules. The first two glucose molecules to join condense out an H-OH, and every glucose molecule added to the growing chain then condenses out another H-OH.
describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass
Cellulose is a flat, straight and rigid molecule.
Cellulose structure
The bulky -CH2OH groups, represented above as LOH , are on alternate sides of adjoining glucose units.
Many of the hydroxy groups form hydrogen bonds that hold the cellulose chains together.
Cellulose chains
The hydrogen bonding results in long strong cellulose fibres. This accounts for why wood is a strong building material. The reduced availability of hydroxy groups in the cellulose structure, due to their involvement in hydrogen bonding between the chains, makes it insoluble in water and resistant to chemical attack.
Cellulose is a natural condensation polymer. Most dry plant material consists of up to 50% cellulose. Approximately 500 000 000 000 (5 x 1011) tonnes of cellulose are produced each year by land plants.
identify that cellulose contains the basic carbon-chain structures needed to build petrochemicals and discuss its potential as a raw material
A three carbon-chain and a four carbon-chain are present within the structure of a glucose monomer in a cellulose chain. These carbon-chains have attached hydrogen and hydroxy groups.
The carbon-chain sections could be changed to chemicals that, at present, are mostly made from petroleum. If a chemical process can be developed or a micro-organism found that can break the glucose into three carbon-chains and four carbon-chains this would be very useful. Many polymers are made using three carbon monomers (such as polypropylene in Australian ‘paper’ currency) or four carbon monomers (such as those used to make synthetic rubbers). Thus biomass, a renewable resource, could be used instead of fossil fuel, a non-renewable resource, to make polymers (like in money and tyres!).
discuss the need for alternative sources of the compounds presently obtained from the petrochemical industry
Petrochemicals are chemicals made from compounds in petroleum or natural gas. Currently Australia has petroleum reserves that will last about ten years and natural gas reserves that will last about one hundred years. Fossil fuels have taken hundreds of millions of years to accumulate. Over 95% of fossil fuel is burnt as a source of energy and once burnt, fossil fuels are no longer available. Less than 5% of fossil fuel is used to make plastics and only a small percentage of that plastic is recycled. If energy and material needs are to be met in the future, alternative sources will be needed as fossil fuel sources are used up.
