Vegan Leather

 My local bag shop is now full of bags that proudly state they are made out of "Vegan Leather".

Vegan leather? Surely that is an oxymoron?

    vegan = not consuming/using any animal products

    leather = animal skin that has been tanned or undergone a similar process.

So what is "vegan leather"?

It turns out that the majority or "vegan leather" is just poly(vinyl chloride) (PVC) or poly(urethane) (PU), polymers produced from reagents derived from fossil fuels. Handbags made out of PVC (vinyl bags) have been around for decades, and have been a much, much cheaper option than expensive genuine leather bags.Until now! By re-branding vinyl bags as "Vegan Leather" suppliers can increase the price, capitalizing on the significant consumer trend toward "vegan" products.

I live in a city that is trying to ban the use of single use plastic items including shopping bags and straws etc which end up in landfill and stay there for (not-quite but almost) ever. How do you feel about your new plastic "vegan leather" handbag? When it starts to fall apart (anything from about a month to a year or so depending on use and quality) and you throw it out, do you feel that you have done your bit for the environment?

If you live in a country where there are growing demands to reduce coal-fired power generation, and reduce the use of fossil fuels in cars etc, in order to reduce the community's "carbon footprint",  how do you feel about your fossil fuel based "vegan leather" bag?

It isn't "vegan leather". It is plastic.

vegan leather bag = plastic bag

New Resources at AUS-e-TUTE

New AUS-e-TUTE Resources for All Members:

-Green Chemistry Principles Tutorial: http://www.ausetute.com.au/greenchemistry.html
-Green Chemistry Principles Game
-Green Chemistry Principles Test

-Atom Economy (Atom Utilsation) Tutorial: http://www.ausetute.com.au/atomeconomy.html
-Atom Economy (Atom Utilisation) Game
-Atom Economy (Atom Utilisation) Test

New AUS-e-TUTE Resources for Teachers:
Worksheet Wizards:
-Atom Economy (Atom Utilisation)
Quiz Wizards:
-Atom Economy (Atom Utilisation)

Sweeter Natural Gas

Natural gas extracted from the coal beds and methane-rich geologic features must first be purged of hydrogen sulfide before it can be used as fuel in a process called "sweetening".

Thermal Swing Regeneration, a common industry process used for sweetening natural gas, uses chemical sponges called sorbents to remove toxic and flammable gases, such as rotten-egg smelling hydrogen sulfide from natural gas. The gas must first be treated with a solution of chemical sorbents that are dissolved in water. That solution must then be heated up and boiled to remove the hydrogen sulfide, in order to prepare the sorbent for future use. Once the hydrogen sulfide is boiled off, the sorbent is then cooled and ready for use again. The repeated heating and cooling requires a lot of energy and markedly reduces the efficiency of the process.

A new process called Antisolvent Swing Regeneration takes advantage of hydrogen sulfide's ability to dissolve better in some liquids than others at room temperatures. In this process, the hydrogen sulfide "swings" between different liquids during the processing at nearly room temperature, resulting in its removal, in just a few steps, from liquids that can be reused again and again.

First hydrogen sulfide is dissolved in a substance known as a DMEA which is a recyclable binding organic liquid, a substance that can hold onto hydrogen sulfide without the addition of water. DMEA forms a salt with hydrogen sulfide. The salty DMEA is then mixed with hexane (or hexadecane and a small amount of heat) which returns most of the hydrogen sulfide back to the gaseous state which is then bubbled out of the mixture. Separating the hexane from the DMEA allows these substances to be re-used.

Scientists estimate that the Antisolvent Swing Regeneration method could reduce the amount of energy needed to complete the sweetening process by at least 10%.

Reference
Phillip K. Koech, James E. Rainbolt, Mark D. Bearden, Feng Zheng, David J. Heldebrant. Chemically selective gas sweetening without thermal-swing regeneration. Energy & Environmental Science, 2011; DOI: 10.1039/c0ee00839g

Further Reading:
Writing Ionic Formulae
Naming Straight Chain Alkanes
Intermolecular Forces

Study Questions:

1. Write the chemical formula for each of the following:
   
   • methane
   • hydrogen sulfide
   • hexane
2. In a sample of each of the following pure substances, what type of forces would you expect to attract molecules to each other?
   
   • methane
   • hydrogen sulfide
   • hexane
3. Describe what would happen if each of these pure substances was mixed with water.
4. Describe what would happen if each of these substances were mixed with a petroleum-based oil.
5. Use the description of the Thermal Swing Regeneration process to draw a flow chart for this method of sweetening natural gas.
   
6. Use the description of the Antisolvent Swing Regeneration process to draw a flow chart for this method of sweetening natural gas.
   

Xanthophylls

Plant pigments are an important source of non-toxic compounds for use as food or cosmetic colouring agents. The coloured xanthophylls in capsicum are important sources of pigments that can replace carcinogenic synthetic dyes.


Xanthopylls are very similar to carotenes but often contain hydroxyl groups.
Cryptoxanthin, shown to the right, is an example of a xanthophyll.

β-carotene, shown on the left, is an example of a carotene.

Until now, the common method for extracting red pigments from dried fruit of Capsicum has used hexane as the extraction solvent. Current extraction processes are limiting in that the red pigment can only be recovered from American paprika varieties or other mild cultivars.

A study from the New Mexico State University presents a process for the efficient extraction of these pigments using a "green chemistry" method that generates an oleoresin from dried capsicum fruit with virtually the same xanthophyll composition as the hexane extraction method.

Reference
Richard D. Richins, Laura Hernandez, Barry Dungan, Shane Hambly, F. Omar Holguin, and Mary A. O'Connell. A 'Green' Extraction Protocol to Recover Red Pigments from Hot Capsicum Fruit. HortScience, 2010; 45: 1084-1087

Further Reading
Functional Groups
Empirical and Molecular Formula
Molecular Mass (Formula Weight)
Percentage Composition
Oxidation of Alcohols
Intermolecular Forces

Study Questions

1. Circle the hydroxyl group in cryptoxanthin.
2. Write the molecular formula for cryptoxanthin.
3. What is the empirical formula for cryptoxanthin?
4. What percentage by mass of carbon is present in cryptoxanthin?
5. Write the molecular formula for β-carotene.
6. What is the empirical formula for β-carotene?
7. What percentage by mass of hydrogen is present in β-carotene?
8. Which molecule, β-carotene or cryptoxanthin, would be the most polar? Explain your answer.
9. If you were given a solution that contained either cryptoxanthin or β-carotene, how might you be able to decide which of the compounds is present in the solution? Explain your answer.
10. If cryptoxanthin were to react with a strong oxidizing agent, what product(s) might you expect from the reaction? Explain your answer.