Perugia - habu-bremen.de · Perugia & Bremen Green Chemistry 1 Comenius 2011-2013 The bilateral...

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Green Chemistry Comenius 2011-2013 1

The bilateral Comenius project „Green Chemistry“ has started in August 2011. This handbook is one of the results of this project. Students of the Istituto Tecnico Tecnologico Statale "A. Volta" in Perugia (Italy) and the Gymnasium an der Hamburger Straße in Bremen (Germany) have worked on Green Chemistry topics. Working in binational teams and using English as working language was a very valuable experience for all participants. During the two exchanges the students and teachers also had the chance to become acquainted with a different culture by living with a foreign family. We would like to thank the European Union for the financial support, the parents of both schools for their hospitality, the teachers for their engagement and the students for their great work. Sonja Schwarze Dr. Axel Herzig

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Contents: Page

Principles of Green Chemistry 3

A Timeline of Green Chemistry 4

Supercritical CO2 as a Solvent Media 5

Alternative Chemical Synthetic Pathways 6

Nanomaterials 7

Biodiesel 8

Catalysis 11

Local Industry 13

Impressions 15

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Principles of Green Chemistry In general the term “Green Chemistry” summarizes the process of reducing the use of dangerous substances in industrial chemistry. The goal is to reduce the pollution of the environment and to develop a field of chemistry that can replace those technologies, e.g. with the use of sustainable alternatives. Green Chemistry is based on 12 principals which help to carry out its idea and to avoid problems to the environment. The principals are: 1. It is better to prevent waste than to treat or clean up waste after it is formed.

2. Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.

3. Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment.

4. Chemical products should be designed to preserve efficacy of function while reducing toxicity.

5. The use of auxiliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used.

6. Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure.

7. A raw material or feedstock should be renewable rather than depleting wherever technically and economically practicable.

8. Reduction of derivatives should be avoided whenever possible.

9. Increase of the energy efficiency with the help of catalysts to reduce the by-products.

10. Elimination of products which are dangerous for the environment.

11. Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.

12. Substances and the form of a substance used in a chemical process should be chosen to minimize potential for chemical accidents, including releases, explosions, and fires.

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A Timeline of Green Chemistry

1962 - Rachel Carson, writer, biologist and environmental conservation icon, publishes the first of three installments of “Silent Spring,”—literature that is historically tied to the launch of the environmental movement. The publication helped spread public awareness of the hazards of environmental pollution and pesticides to the environment.

1969 - President Richard Nixon establishes the Citizen’s Advisory Committee on Environmental Quality and a Cabinet-level Environmental Quality Council. Later that year, Nixon expanded his environmental efforts by appointing the White House Committee to determine whether an environmental agency should be developed.

1970 -The Environmental Protection Agency (EPA) is born.

1980s/1988 - Shift from end-of-pipeline control to pollution prevention is recognized, leading to the Office of Pollution Prevention and Toxics in 1988.

1990 - The Pollution Prevention Act under the George H.W. Bush Administration is passed.

1993 -The EPA implements the Green Chemistry Program, which serves as a precedent for the design and processing of chemicals that lessen the negative environmental impact.

1995 & 1996 - In 1995, President Bill Clinton established the Presidential Green Chemical Challenge Awards, which served to encourage those involved with the manufacture and processes of chemicals to incorporate environmentally sustainable design and processes in their practices. The following year, the first recipient receives the award, the only award issued by the president that honors work in chemistry.

1997 - The Green Chemistry Institute is launched. Its vision is “…to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and its people.

1998 - “Twelve Principles of Green Chemistry” is published by Paul Anastas (of the EPA) and John Warner.

2000s-Present - In the past decade, some major green chemistry achievements include the California Green Chemistry Initiative.Governor Arnold Schwarzenegger signed the bills to in 2008, which serve to develop policy options for green chemistry. One year later, President Obama nominated Paul Anastas (of Yale) as head of Research and Development at the EPA.

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Supercritical CO2 as a Solvent Media

Environmentally Benign Chemical Synthesis and Catalysis in Liquid and Supercritical Carbon Dioxide (SC-CO2)

A large number of industrial chemical reactions occur in organic solvents which include chlorofluorocarbons, benzene, and carbon tetrachloride-all of which have such environmental downside such as toxicity or damage to the stratosphere ozone layer. Many of these solvents are among the ten most released chemicals to the environment. Supercritical carbon dioxide (SC-CO2) has been identified as a promising environmentally benign solvent. It is an energy conserving, selective and waste reducing alternative to organic solvents. Fast and sensitive organic synthesis can be achieved with high levels of functionality, controllability and energy efficiency. Product separation and fractionation may accompany the reaction, reducing the number of process steps.

The environmental advantages of using SC-CO2 in a closed loop system, are counterbalanced by efforts and expenses associated with the use of high pressure installations. The operational economics of the process and related environmental impact for the use of supercritical fluids as a reaction/separation medium for heterogeneous reactions is being analyzed.

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Alternative Chemical Synthetic Pathways

Organic reactions under solvent-free conditions are advantageous because of enhanced selectivity and efficiency, easy of manipulation and because toxic and often volatile solvents are avoided. Solvent-free approaches involve mechanochemical mixing (grinding), microwave (MW) irradiation of neat reactants (undiluted), or catalysis by the surfaces of inexpensive and recyclable mineral supports, such as alumina, silica, clay, or ‘doped’ surfaces. These approaches are applicable to a wide range of cleavage, condensation, cyclization, oxidation, and reduction reactions, including convergent one-pot assembly of heterocyclic compounds from in situ generated reactive intermediates such as α-tosyloxyketones and enamines. The strategy is adaptable to multi-component reactions for high-speed parallel synthesis of a library of biologically active molecules. Recent results for the MW-expedited approach include the synthesis of a wide variety of industrially significant compounds and intermediates.

MW irradiation, an unconventional energy source, has been used for a variety of organic transformations wherein chemical reactions are accelerated because of selective absorption of MW energy by polar molecules; non-polar molecules are inert to the MW dielectric loss. The MW application under solventless conditions enables rapid synthetic transformations at ambient pressure, thus providing unique chemical processes with special attributes such as ease of manipulation, enhanced reaction rates, and higher yields. The distinct advantage of this strategy, that reduces or prevents pollution ‘at-source,’ has been exemplified by efficient functional group transformations involving non-metallic hypervalent iodine oxidants and substitution of conventional reducing agents.

The development of efficient and selective greener methods has become a major focus of researchers worldwide and selection of appropriate alternate eco-friendly reaction media has become an integral part of this paradigm shift. Microwave (MW) irradiation as an alternative energy source in conjunction with water as reaction medium has proven to be a successful ‘greener’ chemical approach. Recent examples include the aqueous N-alkylation of amines by alkyl halides that proceed expeditiously in the presence of aqueous sodium hydroxide to deliver tertiary amines. The synthesis of Ν-azacycloalkanes, an important class of building blocks in natural products and pharmaceuticals, can be achieved by a simple, efficient, and environmentally friendlier alternative using MW protocol.

The MW-assisted reaction proceeds in aqueous potassium carbonate and leads to the formation of a variety of five-membered heterocycles by condensation of amines or hydrazines with alkyl 1,3-dihalides or -ditosylates. Similarly, classical nucleophilic substitution reactions can be revisited in aqueous medium by reacting alkyl halides or tosylates with alkali azides to provide azides and thiocyanides in the absence of a phase transfer catalyst. The protocol can be extended to preparation of sulfones from sulfinate salts in aqueous medium.

These MW-assisted ‘greener’ and expeditious chemical transformations circumvent the need for multi-step processes that use expensive metal catalysts and accommodate reactive functional groups because of mild reaction conditions, thus minimizing or eliminating the formation of byproducts.

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Nanomaterials

The heavy investment in the development and deployment of products containing nanomaterials is now a worldwide phenomenon. The unique physical and chemical properties of nanomaterials, such as different conductivity, optical sensitivity, and reactivity, originate mainly from factors such as small size, surface structure, chemical composition, shape, solubility, or aggregation. These varied properties are attractive for application in a variety of technology areas. Consequently, nanomaterials are becoming widely used in varied applications from cosmetics to semiconductors. Nanotechnology development and production presents a unique opportunity to offer a more sustainable approach to protect public health and the environment and prevent future environmental liability.

The greener preparation of these materials renders the materials less mobile in the environment and reduces or eliminates the use and generation of hazardous substances, such as the hydrazine and borohydride reducing agents normally used in nanomaterials production. Three areas of opportunity are being exploited to engage green chemistry: choice of solvent, the reducing agent employed, and the capping agent (or dispersing agent). The synthesis of nanometal/nanometal oxide/nanostructured polymers and their stabilization (through dispersant, biodegradable polymer) will involve the use of natural renewable resources such plant material extract, biodegradable polymers, and sugars, and finally microwave (MW) irradiation as an efficient and selective mode of activation.

Vitamins B1 and B2 or related benign materials can function both as reducing and capping agents and provide an extremely simple, one-pot, greener method to synthesize bulk quantities of nanospheres, nanorods, nanowires, and nanoballs of aligned nanobelts and nanoplates of the metals in water without the need of large amounts of insoluble templates. A facile MW method has been developed that accomplishes cross-linking reaction of poly (vinyl alcohol) (PVA) with metallic and bimetallic systems.

Polyaniline nanofibers can reduce metal salts to generate novel nanocomposites which exhibit high thermal stability with broad decomposition temperatures, which could lead to a myriad of applications, such as energy storage systems, catalysis, fuel cell membranes, and nanodevices.

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Biodiesel

Biodiesel refers to a vegetable oil or animal fat consisting of long-chain alkyl (methyl, ethyl or propyl) esters. Biodiesel is produced by transesterification or alcoholysis, biodiesel production involves reacting vegetable oils or animal fats catalytically with a short-chain aliphatic alcohols.

The major steps requiered to synthesize are as follows: 1. Feedstock pretreatment:

If waste vegetable oil is used, it is filtred to remove dirt, charme food, and other non-oil material often found. Water is removed because the presence causes the triglycerides to hydrolyze, living salts of the fatty instead of undergoing transesterification to give biodiesel.

2. Determination and treatment of free fatty acid: A sample of the celanese feedstock oil is tirated with a standardized base solution in order to determine the concentration of free acids present in the waste vegetable oil sample. These acids are then either esterified into biodiesel, esterified into bound glycerides, or removed, typically through neutralization.

3. Reactions: While adding the base, a slight excess is factored in to provide the catalyst for the transesterifications. The calculated quantity of base is added slowly to the alcohol and it is stirred until it dissolves. Sufficient alcohol is added to make up three full equivalents of the trigliceride, and an excess of usually six parts alcohol to one part triglyceride is added to drive the reaction to completino.

4. Product purification: Products of the reaction include not only biodiesel, but also byproduct, soap, glycerin, excess alcohol, and trace amounts of water. All of these byproduct must be removed, though the order of removla is process-dependent. The density of glycerin is grater than that of biodiesel, and this property difference is exploited to separate the bulk of the glycerin byproduct. Residual methanol is typically removed through distillation and reused, though it can be washed out as a waste. Soaps can be removed or converted into acids. Any residual water must be removed from the fuel.

Alternative method are as follows: • Supercritical process. • Ultrasonic-reactor method. • Microwave method. • Lipase-catalyzed method. • Ultra-high-shea in-line method and batch reactors.

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A variety of oils can be used to produce biodiesel. These include: � Virgin oil feedstock-rapeseed and soybean oils are most commonly used, soybean

oil alone accounting for about ninety percent of all fuel stocks in the US. It also can be obtained from field pennycress and jatropha and other crops such s mustard, jojoba, flax, sunflower, palm oil, coconut, hemp.

� Waste vegetable oil. � Animal fats including tallow, lard, yellow grease chicken fat, and the by-products of

the production of Omega-3 fatty acids from fish oil. � Algae, which can be grown using waste materials such as sewage and without

displacing land currently used for food production. � Oil from halophytes such as Salicornia bigelovi, which can be grown using saltwater

in coastal areas where conventional crop cannot be grown, with yields equal to the yields of soybeans and other oilseeds grown using freshwater irrigation.

The waste vegetable oil is the best source of oil to produce biodiesel, but since the available supplì is drastically less than the amount of petroleum-based fuel that is burned for transportation and home heating in the world, this local solution could not scale the current rate of consumption.

Animal fats are a by-product of meat production. Altough it would not be efficient to raise animals simply for their fat, use of the by-product adds value to the livestock industry. However, producing biodiesel with animal fat that would have otherwise been discorde could replace a small percentage of petroleum diesel usage. Today, multi-feedstock biodiesel facilities are producing high quality animal-fat based biodiesel. Some small-scale biodiesel factories use waste fish oil as feedstock. An EU-funded project suggest that a Vietnamese plant to produce biodiesel from catfish, an output of 13 tons/day of biodiesel can be produced from 81 tons of fish waste. This project utilises the biodiesel to fuel a CHP unit in the fish processing plant, mainly to power the fish freezing plants.

Blends of biodiesel and conventional hydrocarbon-based diesel are products most commonly distribuited for use in the retail diesel fuel marketplace. Much of the world uses a system known as the “B” factor to state the amount of biodiesel in any fuel mix:

1. 100% biodiesel and 0% petrodiesel is labeled B100 2. 20% biodiesel and 80% petrodiesel is labeled B20 3. 5% biodiesel and 95% petrodiesel is labeled B5 4. 2% biodiesel and 98% petrodiesel is labeled B2

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Blends of 20% biodiesel and lower can be used in diesel equipment with no, or only minor modifications, although certain manufacturers do not extend warrantly coverage if equipment is damaged by these blends. The B6 to B20 blends are covered by the ASTM D7467 specification. Biodiesel can also be used in pure form, but may require certain engine modifications to avoid maintenance and performance problems. Blending B100 with petroleum diesel may be accomplished by:

� Mixing in tanks at manufacturing point prior to delivery to tanker truck. � Splash mixing in the tanker truck � In-line mixing, two components arrive at tanker truck simultaneously. � Metered pump mixing, petroleum diesel and biodiesel meters are set to X total

volume, transfer pump pulls from two points and mix is complete on leaving pump.

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Catalysis

Catalysis is the change of a chemical reaction with participation of a substance called a catalyst. Unlike other reagents a Catalyst is not consumed by the proceeding of the reaction. The term also employees with chemical catalysis which studies the synthesis, characterization, design and development of molecules to cover the role of catalysts for the improvement of the most varied reactions.

A Catalyst affects the Reaction so, that the Activation Energy is lower.

The catalysis is a chemical phenomenon by which the speed of a reaction changes with the presence of a catalyst which changes the path in order to have a lower activation energy. The kinetic conditions are different, while the thermodynamic conditions remain unchanged.

The general principle of is the variation of the reaction mechanism, and to split the reaction in various “jumps” that the reagents have to take, instead of one larger Activation energy to reach the products. The effect of catalysis is of kinetic nature, and not thermodynamic. The action of the catalyst only modifies the intermediate stages of a reaction, but does not change the final states. This means that the catalysis does not affect whether the reaction has to take place or not. In the most cases the Catalysis changes the increases the speed of the reaction.

There are also cases in which the intervention of a catalyst lower the speed: in this case one speaks of negative catalysis or inhibition (and the catalyst shall be called inhibitor of the reaction then).

According to the condition of the catalyst, there are two types of catalysis:

• homogeneous catalysis: if the catalyst is dissolved in the reaction Medium and they are in the same phase, it is called homogeneous catalysis.

• heterogeneous catalysis: if the catalyst and reagents are not in the same phase (for example, if the catalyst is solid and in a reaction environment fluid).

The synthesis of ammonia (NH3) starting from nitrogen and from hydrogen was done by Fritz Haber. Catalysis made this reaction possible. The decade 70s saw the emergence of the catalyst based on platinum, rhodium and palladium. This era developed an industrial scale of enzymatic catalysis, allowing the development of semisynthetic penicillins and isomerizations of glucose to fructose.

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Bio-catalysis

The bio-catalysis is a conversion and acceleration or steering system of chemical reactions in which enzymes serve as biological catalysts.

Enzymes catalyze metabolism processes in living beings. These types of reactions occur at low temperatures and have a very high efficiency and selectivity.

The mild temperature leads,that for given conditions, only one functional group react and so the separation of the by-products is less problematic.Almost all biocatalysts are proteins or consist of a cofactor ( name of the substances which are necessary for enzymatic reactions.)

Depending on the function of the enzymes, they are divided into 6 classes:

oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases.

Bio-catalysis is a well known and old chemical process that was previously used for brewing beer. Other biocatalytic processes are the production of Vitamin C, the saccharification of starch to glucose syrup and the production of antibiotics.

Green Oxidant Catalyst Development To begin with an inexpensive raw material and chemically transform it into a viable chemical commodity, in a benign catalytic manner, is the emphasis of this research. The design and synthesis of green oxidants for use as alternatives to traditional oxidants can offer an environmental solution to the area of oxidation catalysis. Selective oxidation catalysis has been identified as one of the most environmentally hazardous industrial processes. Low conversions, multiple product waste streams, toxic solvents, stoichiometric oxidants and toxic metal catalysts are all pitfalls for this industry. As a result, oxidation catalysis resides at the top of many workshop lists with respect to areas of the catalytic industry needing the majority of research and development. This research is centered on the synthesis, characterization and use of inorganic complexes that serve as catalytic precursors for molecular catalysis and design. This research is also designed to utilize the aspects of Green and Environmental Chemistry, atom economy as well as a multidisciplinary approach.

The catalysts are designed to be simple and are based on enzymes and proteins found in the human body and nature. These bio-mimetic complexes are comprised of two important components, the ligand system and the metal center. The ligand systems are designed to be simple, robust, rigid, tunable, and oxidatively resistant as well as utilizing non-toxic elements: N, O, H, C, S, and P. The metal centers are chosen for their ability to maintain large oxidation potentials, possess multiple oxidation states and have non- or minimal toxicity. When the two portions are combined a robust inorganic catalytic precursor results. Activation of the precursor occurs upon addition of hydrogen peroxide and/or molecular oxygen (clean oxidants) to generate a high valent metal-oxo species. These catalytic metallo-oxidants or green oxidants are able to effectively and selectively oxidize a multitude of organic substrates (e.g. alkanes and alkenes) into their corresponding oxygenates at low temperatures (<100°C) and pressur es (< 2 atm).

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Local Industry Solvay Solvay is an international chemical group with head office in Brussels. It employs 29,000 employees worldwide, 3,000 of which work in the German branch headquartered in Hannover. Its production is located in the German towns of Ahaus, Bad Hönningen, Bad Wimpfen, Bernburg, Frankfurt, Rheinberg and Freiburg. The company can be defined as the sum of three sectors with different main products. The first sector, 'SOLVAY Chemicals', oversees the production of special and basic industrial chemicals, such as fluor, bicarbonate and sodium hydroxide. The second sector, 'SOLVAY Plastics', mainly produces fluoropolymers and vinyl products. 'SOLVAY Rhodia', the third sector, consists of 11 Global Business units, each specialized in a specific product line. These product lines include celluloseacetyl (for cigratte filters and textile fibers), silicon dioxide (for tire and rubber production), sulfuric acid, flourinated compounds, rare aluminumoxides (for high-tech material production), and dephenols and derivatives (used for fragrance and flavor production). Solvay sells its products to a wide range of markets ranging from alternative energies and the food industry to packaging and automotive engineering. The Solvay group claims to take environmental and social responsibility by using sustainable materials and supporting manufacturers in their drive to optimize energy consumption. An example for this effort is the biogas plant in the industrial park Solvay Rheinberg, where an attempt is made to replace the commonly used fossil fuel carbon with clay, made from eastern European grains, which were found to be insufficient for the food industry. Furthermore Solvay reduces process waste by using residues from the sodium carbonate production to synthesize sodium bicarbonate, which can be used in food products, cosmetics and pharmaceuticals. The company also takes part in innovative, climate-friendly projects, such as the production of a solar-cell powered airplane. The goal to meet all health-, security-, and environment-related needs of its employees and the entire society can be found in Solvay's mission statement on its website. Sources: www.solvay.de www.rhodia.com

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Enzymicals Enzymicals produces biocatalysts for fine and specialty chemicals. It was founded as a spin-off of the University Greifswald in 2009. Enzymicals has a lot of research partners in industry, but also cooperates with Hochschulen, and with networks. Also, some companies help to finance Enzymicals. The main idea of the foundation is to provide biocatalysts for the customer and to secure an alternative and economical defined production of chemicals. The main aspects of Enzymicals are enzymes, chemicals, and solutions. Enzymes Enzymicals offers enzymes for production, research and development, and diagnostics, and especially focuses the recombinant pig liver esterases, (R)-selective amine transaminases and Baeyer-Villiger mono- oxygenases to solve problems. Chemicals Enzymicals offers specialty chemicals with a high production capacity and its products include chiral secondary and tertiary alcohols, carboxylic acids, lactones, esters and amines. The development of synthesis and customers preferences are important. First, the catalysts are identified for the production. Next, the protein engineering technology offers the optimizing of enzymes. After all, the production of high-value chemicals is able because of the optimized reaction pathway. Solutions Enzymicals produces and discovers enzymes in the interest of its partners. It includes the identification of enzymes, their functional expression, and protein engineering. To apply biocatalysts in processes synthesis and strategies are developed and customer specific solutions created. Sources: www.enzymicals.com/index.html www.jobvector.de/images/jv_employer/7/6/4/6/logo_image_path/standart/7646_enzymicals1.jpg

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Impressions from the exchange in Bremen

Students working in the laboratory at the University of Bremen

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