Green Chemistry and Biofuels

Audience

Middle School / High School (Chemistry)

Time Frame

(3 days)

Day 1 (Introduction Green Chemistry and Catalysis- 40 min)

Set-up:  5 minutes

Focus:  5 minutes

Activity:  15 minutes

Close:  5 minutes

Clean up:  10 minutes

Day 2 (Biofuels - 40 min)

Set-up:  5 minutes

Focus:  5 minutes

Activity:  15 minutes

Close:  5 minutes

Clean up:  10 minutes

Day 3 (Experiment: Heterogeneous Catalysis with a Zeolite – Hydrolysis of sucrose in sugarcane juice - 90 min)

Set-up:  10 minutes

Focus:  5 minutes

Activity:  55 minutes

Close:  10 minutes

Clean up:  10 minutes

Objective(s)

After completing the module, students will be able to:

  1. Identify the goals of green chemistry.
  2. Define sustainability as it relates to Green Chemistry.
  3. State the grand challenges that green chemists must face to make the field of chemistry more sustainable.
  4. Explain that plants must be processed in order to release the energy stored in them and why some biofuel sources are not good choices since they are also food crops.
  5. State that sugar is the energy source we use for our bodies and will be the energy source for new biofuels.
  6. Describe how the thick cell walls of plants must be broken down to release the sugar that is wrapped in lignin and cellulose.
  7. Understand how catalysts increase the reaction rate and the selectivity of chemical reactions.
  8. Explain that catalysis can be classified as either heterogeneous or homogeneous.

National Science Education Standards addressed in this module: 

Content Standard A:  Science as Inquiry

Content Standard B:  Physical Science

 1. Chemical Reactions.

e.  Catalysts accelerate chemical reactions.

Content Standard F: Science in Personal and Social Perspectives.

1. Natural Resources

b.  Human populations use resources in the environment in order to maintain and improve their existence. Natural resources have been and will continue to be used to maintain human populations.

c.  The earth does not have infinite resources; increasing human consumption places severe stress on the natural processes that renew some resources and it depletes those resources that cannot be renewed.

d.  Humans use many natural systems as resources. Natural systems have the capacity to reuse waste, but that capacity is limited. Natural systems can change to an extent that exceeds the limits of organisms to adapt naturally or humans to adapt technologically.

2. Environmental Quality

c.  Many factors influence environmental quality. Factors that students might investigate include population growth, resource use, population distribution, overconsumption, the capacity of technology to solve problems, poverty, the role of economic, political, and religious views, and different ways humans view the earth.

3. Natural and Human-Induced Hazards

b.  Human activities can enhance potential for hazards. Acquisition of resources, urban growth, and waste disposal can accelerate rates of natural change.

d.  Natural and human-induced hazards present the need for humans to assess potential danger and risk. Many changes in the environment designed by humans bring benefits to society, as well as cause risks. Students should understand the costs and trade-offs of various hazards--ranging from those with minor risk to a few people to major catastrophes with major risk to many people. The scale of events and the accuracy with which scientists and engineers can (and cannot) predict events are important considerations.

4. Science and Technology in Local, Global and National Challenges 

b.  Understanding basic concepts and principles of science and technology should precede active debate about the economics, policies, politics, and ethics of various science- and technology-related challenges. However, understanding science alone will not resolve local, national, or global challenges.

Activities Materials:

400 mL beaker

weighing dish

10 mL graduated cylinder

eight 20 × 150 mm test tubes

scale

10 mL volumetric flask

spatula

50-100 ml of 30% hydrogen peroxide (H2O2) solution

saturated potassium iodide (KI) solution

liquid dishwashing detergent

food coloring

500 mL graduated cylinder

0.2g of Zeolite Y- dealuminated

4.0g table sugar

2 mL sugar cane juice

distilled water

test tube rack

hot plate + stirrer

magnetic stirrer

thermometer

1 Gummy Bear 

5 g of Potassium chlorate

1 pyrex test tube (25mm x 200mm)

tongs

test tube clamp

stand

burner

Day 1:  Green Chemistry and Catalysis

Introduction 

Green chemistry is the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product, including its design, manufacture, use, and ultimate disposal. Green chemistry is also known as sustainable chemistry.

Green chemistry provides unique opportunities for innovation via product substitution, new feedstock generation, catalysis in aqueous media, utilization of microwaves, and scope for alternative or natural solvents. Discuss the potential of utilizing waste as a new resource and the development of integrated facilities producing multiple products from biomass. Biofuels are discussed in depth, as they not only provide fuel (energy) but are also a source of feedstock chemicals. In the future, the commercial success of biofuels commensurate with consumer demand will depend on the availability of new green chemical technologies capable of converting waste biomass to fuel in a context of a biorefinery.

Catalysis is one of the fundamental pillars of green chemistry, the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. The design and application of new catalysts and catalytic systems are simultaneously achieving the dual goals of environmental protection and economic benefit.

Homogeneous Catalysis Demonstration:  Elephant Toothpaste

(from chemistry.about.com)

The elephant toothpaste chemistry demonstration is a dramatic demo which produces copious amounts of steaming foam that sort of looks like the toothpaste an elephant might use. Here's how to set up this catalysis demonstration and a look at the reaction behind it.

Materials:

50-100 ml of 30% hydrogen peroxide (H2O2) solution

saturated potassium iodide (KI) solution

liquid dishwashing detergent

food coloring

500 mL graduated cylinder

paper towels

Methodology:

  1. Put on gloves and safety glasses. The iodine from the reaction may stain surfaces so you might want to cover your workspace with an open garbage bag or a in a demonstration tray.
  2. Pour 50 mL of 30% hydrogen peroxide solution into the graduated cylinder.
  3. Squirt in a little dishwashing detergent and swirl it around.
  4. You can place 5-10 drops of food coloring along the wall of the cylinder to make the foam resemble striped toothpaste.
  5. Add 10 mL of potassium iodide solution. Do not lean over the cylinder when you do this, as the reaction is very vigorous and you may get splashed or possibly burned by steam.

The overall equation for this reaction is:

2 H2O2(aq) → 2 H2O(l) + O2(g)

However, the decomposition of the hydrogen peroxide into water and oxygen is catalyzed by the iodide ion.

H2O2(aq) + I-(aq) → OI-(aq) + H2O(l)
H2O2(aq) + OI-(aq) → I-(aq) + H2O(l) + O2(g)

The dishwashing detergent captures the oxygen as bubbles. Food coloring can color the foam. The heat from this exothermic reaction is such that the foam may steam. If the demonstration is performed using a plastic bottle, you can expect slight distortion of the bottle from the heat.

Day 2:  Biofuels

Introduction

Biofuels are energy sources made from living things, or the waste that living things produce. Supporters of biofuels argue that their use could significantly reduce greenhouse gas emissions; while burning the fuels produces carbon dioxide, growing the plants or biomass removes carbon dioxide from the atmosphere. Detractors claim that biofuel production poses a major threat to global food systems and the natural environment.

Biofuels can come from a wide variety of sources and can be roughly divided into four categories or "generations:"

  • First generation biofuels are made from sugars, starches, oil, and animal fats that are converted into fuel using already-known processes or technologies. These fuels include biodiesel, bioalcohols, ethanol, and biogasses, like methane captured from landfill decomposition.
  • Second generation biofuels are made from non-food crops or agricultural waste, especially ligno-cellulosic biomass like switch-grass, willow, or wood chips.
  • Third generation biofuels are made from algae or other quickly growing biomass sources.
  • Fourth generation biofuels are made from specially engineered plants or biomass that may have higher energy yields or lower barriers to cellulosic breakdown or are able to be grown on non-agricultural land or bodies of water.

(Video: Sugar Cane Bagasse - Puerto Rico’s possible feedstock)

Energy in Sugar Demonstration:  Oxidation of Sugar (Gummy Bear) with Potassium Chlorate 

(from lecturedemos.chem.umass.edu/chemReactions5_5.html)

Sugar is, extremely easy to oxidize, and is a good source of energy, as you know if you've ever eaten a candy bar. Potassium chlorate, KClO3, is a white, crystalline or powdery solid that is a very good oxidizing agent that is used in explosives, fireworks, matches, etc.  When it decomposes under heating (especially in the presence of a manganese catalyst), it releases molecular oxygen, O2:

2KClO3(s) —heat—> 2KCl(s) + 3O2(g)

Materials:

1 Gummy Bear 

5 g of Potassium chlorate

Pyrex test tube (25mm x 200mm)

Tongs

Test tube clamp

Stand

Burner

Methodology:

  1. Use proper safety precautions, including safety goggles and a lab coat. Be advised, the reaction is vigorous enough that the test tube may shatter.
  2. Place a small amount (~5g) of potassium chlorate in the test tube.
  3. Securely clamp the test tube with opening pointed in safe direction.
  4. Heat the potassium chlorate with the burner until molten.
  5. Remove heat source and turn off.
  6. With tongs, add a Gummy Bear to the molten KClO3
  7. Stand back. The reaction will be immediate.

Day 3:  Experiment:  Heterogeneous Catalysis with a Zeolite – Hydrolysis of sucrose in sugarcane juice

Experiment:  Heterogeneous Catalysis with a Zeolite – Hydrolysis of sucrose in sugarcane juice

Introduction

This experiment was designed to show the effect of a catalyst during the hydrolysis reaction of sucrose and how Benedict's reagent is used in a test commonly used for the presence of reducing sugars. It is a simple experimental process where students will have the opportunity to practice some principles of green chemistry and recover the solid catalyst that can be reused.

This activity also reinforce the necessity to develop sustainable alternatives like processing of plants in order to release the energy stored in them and the production of biofuels if they do not compete with food crops. Students can open a debate of the potential of utilizing waste as a new resource and the development of integrated facilities producing multiple products from biomass.

Part I - Heterogeneous Catalysis with Zeolite

(a)  Half fill a beaker with tap water and place it on a hot plate with stirrer at medium rpm. While waiting for the water to reach 80°C, carry on with instructions (b) to (d).

(b)  Label four test-tubes 1-4.

                                             Water into tube 1

                                             40% sucrose solution into tube 2 

(c)  Put 10 mL of            

                                             10% sugarcane solution into tube 3

                                             10% sugarcane + 0.1g of zeolite into tube 4

(d)  Put a magnetic stirrer into all tubes.

(e)  Place the test-tubes in the beaker of hot water and adjust the temperature to keep the water at 80°C.

(f)  After 30 minutes, remove the test tubes from the hot plate and put them in an ice water bath until get room temperature. Place the four tubes in a test-tube rack. 

(g)  Centrifuge tube 4 at 2000 rpm X 15 min OR proceed with a vacuum filtration of the sample with nitrocellulose 0.22μm filter.

(h)  After finishing step (g), keep the supernatant or the filtered solution for the part II of the experiment.

Part II. Benedict’s test for reducing sugars

Safety precautions:  

  • Wear eye protection, lab coat, and goggles and use the smallest possible amounts of chemicals.
  • Use Benedict’s solution and heat test tubes with a water bath.

(a) Keep the beaker with hot water on a hot plate. Continue with the stirrer at medium rpm and be sure that the water is at 80°C. Continue with instructions (b) to (d).

(b) Label four test tubes 1-4.

(Samples from Part I of the experiment)

                              Water into tube 1

                             40% sucrose solution into tube 2

(c) Put 2 mL of    

                            10% sugarcane solution into tube 3

                             Supernatant or filtered solution of 10% sugarcane + zeolite into tube 4

(d) Add to each tube about 10 drops of Benedict's solution.

(e) Place the test tubes in the beaker of hot water and adjust the temperature to keep the water at 80°C and then copy the table below into your notebook.

(f) After about 10 minutes, remove the test tubes from the hot plate and put them in the ice water bath. Place the four tubes in a test-tube rack and compare the colors. Record the results in the form of a table in your notebook.

Sample

Color change on heating with Benedict’s reagent

1

Water

2

40% sucrose

3

10% sugarcane solution

4

 Supernatant of 10% sugarcane + zeolite


Post-Lab Discussion

  1. What did the Benedict's solution test for?
  2. How did the presence of a reducing sugar affect the Benedict's solution?
  3. What color will the Benedict's solution display if there is no reducing sugar in the solution?
  4. What color will the Benedict's solution display if it tested a table sugar (sucrose) solution?
  5. Did the sugarcane juice contain reducing sugars? How could you tell?
  6. Which solution underwent the most dramatic color shift?  Why?
  7. Why was water included in the test?
  8. The results show differences between sugarcane solutions? Why?
  9. What do you think is the effect of the zeolite on the solution of sugarcane juice?


Background

  • Prior Knowledge

Biomass

Sugars

Concentration

Solutions

Heterogeneous

Homogeneous

Carbohydrates

Chemical reaction

Catalysis

Supplemental Materials

  • PowerPoint Presentation
  • Lab sheet for students
  • Video:  Sugar Cane Bagasse - Puerto Rico’s possible feedstock
  • Centrifuge protocol
  • Post-Lab Discussion Sheet
  • How to Calibrate your Dropper
  • MSDS Potassium Chlorate
  • MSDS Potassium Iodide
  • MSDS Benedict Reagent

References

  • Anastas, P. and Zimmerman, J. "Design Through the 12 Principles of Green Engineering," Environmental Science and Technology. March 1, 2003, ACS Publishing
  • http://www.cebc.ku.edu/about/green.html – Lists the tenets of green chemistry and green engineering.
  • http://chemistry.about.com/od/chemistrydemonstrations/a/elephanttooth.htm
  • https://cebc.ku.edu/sites/cebc.drupal.ku.edu/files/docs/10-31-07-biodieselmodule.pdf
  • lecturedemos.chem.umass.edu/chemReactions5_5.html
  • http://pathology.ubc.ca/files/2012/06/CentrifugeInstructions.pdf
  • http://www.dartmouth.edu/~chemlab/techniques/vfiltration.html


Authors

RET Fellow: Diana Rodríguez Pérez

RET Leadership Team: Nelson Cardona Martínez, Chemical Engineering Ph.D. – PI and Wi(PR)2EM Director

Ph.D. Candidate in Chemical Engineering - Mentor: Christian Rivera Goyco

Ph.D. Candidate in Chemical Engineering - Collaborator: Darlene Galloza Lorenzo

Ungraduated Student - Collaborator:  Michelle Marrero Vázquez 





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are a product of the

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University of Wisconsin – Madison

Funding provided by the National Science Foundation