chem unit 4

What is green fuel

Fuel produces from renewable sources that have lower environmental impact (i.e. lower greenhouse gas emission and/or no harmful residue left after combustion)as compared to traditional fossil fuels

Give examples of green fuel

Hydrogen fuel, Biofuel, wind power, solar power, geothermal energy, synthetic fuel(ex synthetic methane produced from CO2 and H2)

Write environmental benefit of green fuel

1. no emission of greenhouse gases

2. no emission of pollutants

3. derived from renewable sources

4. limit global warming

write economic benefits of green fuel

1. new jobs created in field of production ,R&D and manufacturing of renewable energy(estimated 11 millions jobs in 2018, rising year by year)

2. development of green fuels demands technological innovation that benefits other fields, which improves overall economy and technological capabilities of a country

3. diversification of energy portfolio, eliminating dependency on one type of fuel

4. cleaner transportation options, reducing traffic congestion and improving air quality

what are types of hydrogen based on how it is produced

grey, brown, green, blue

define grey hydrogen and by-product during it’s manufacture

1. derived from hydrocarbon

2. CO2 is by-product

3. emission of CO2 makes it a significant greenhouse gas emitter

define brown hydrogen

1. also called black hydrogen

2. derived from coal

3. process cause high pollution

4. CO2 and CO produced as by-product

define blue hydrogen

1. derived from hydrocarbons(natural gas)

2. emissions generated can be captured and stored underground by industrial carbon capture and storage (CCS)

3. cleaner then grey hydrogen, but still relies on natural gas for it’s production
   

define green hydrogen

1. generated from renewable sources (wind and solar)

2. electricity splits water into H₂ and O₂

3. cleanest way to make the cleanest fuel

4. only byproducts is water, it is a zero carbon emission process

write two methods to split water

photo-catalytic water splitting and photo-electro-chemical water splitting

Write three fundamental steps of photo-catalytic water splitting

1. Photocatalyst absorbs photons having energy more than the bandgap, creating electron-hole pairs in the( e^- in the conduction band and hole in the valence band)

2. these electron hole pairs migrate from the bulk to the active sites on the surface where redox reaction can occur

3. redox reaction occurs producing H2 and O2

Write reactions involved in photo-catalytic water splitting and give example of catalyst used

write the steps of photo-electro-chemical water splitting

1. photon of sufficient energy strikes the surface of semiconductor photo-electrode(anode), generating electron hole pair

2. electron migrates to cathode by means of external circuit(external circuit is biased)(anode connected to positive terminal and cathode connected to negative terminal)

3. oxidation of water molecule by hole at anode producing O₂ and H⁺

4. H⁺ migrate to cathode thru electrolyte where it is reduced by electron to produce H₂ gas.

Note- anode is made of semiconductor material, whereas cathode is made of inert material such as Pt

write reactions involved in photo-electro-chemical water splitting and type of semi conductor used

Draw diagram of hydrogen fuel cell and explain it’s working

1. hydrogen is fed to anode, and air is fed to cathode

2. at anode H₂ gas breaks down to H⁺ and e^-

3. H⁺ travels to cathode via electrolyte and e^- travels to cathode via external circuit

4. at cathode, H⁺ and e^- combine with oxygen to produce water and heat

Write production of biodiesel from Jatropha

1. Name of reaction is transesterification

2. Mix an alcohol(usually methanol) with NaOH( or KOH), creating sodium methoxide(catalyst)

3. add this to jatropha oil(contains triglyceride), glycerin and biodiesel are obtained

4. glycerin settles to the bottom, biodiesel(methyl ester) floats on top

5. biodiesel is washed and filtered

what is biopolymer made from and what are it’s applications

• derived from biobased materials

• biodegradable
  
  usage →

• biopolymers that degrade to harmless products in the body can be used in medical devices and drug delivery

• greener than traditional plastics

give examples of non/biodegradable x renewable/petrochemical materials

Name two biodegradable polymers(in syllabus)

Polylactic acid(PLA) and polyvinyl alcohol(PVA)

write the two methods of synthesis of lactic acid

write three methods for synthesis of PLA from Lactic acid

write properties of PLA

1. excellent shaping and molding properties, sheet extrusion, film blowing and fiber spinning

2. bio-compatible

3. bio-reabsorbable

4. transparency, high elastic modulus and high melting point

write applications of PLA

1. fixation of fractured bones in the forms of plates/pins/screws

2. drug delivery- microspheres, microcapsules, RNA/DNA delivery

3. 3D electrospun fibrous scaffolds for bone regeneration

4. sutures in dermatology

what is polyvinyl alcohol produced from

polyvinyl acetate

write structure of vinyl alcohol and why PVA is not produced by polymerizing vinyl alcohol

vinyl alcohol is thermodynamically unstable and tautomarized to aldehyde

write reaction for synthesis of polyvinyl alcohol

We polymerize vinyl acetate to get polyvinyl acetate
we convert PVAc into PVA through base-catalyzed transesterification

Properties of PVA

1. high flexibility and tensile strength, ductile

2. miscible in water

3. immiscible in organic solvents (except for slightly soluble in ethanol

Applications of PVA

1. Manufacturing of adhesives

2. food packaging materials

3. controlled release drug tablets/capsules

4. used as surface sizing agent to improve paper’s surface strength and printability