Green Chemistry and Engineering

A Pathway to Sustainability

Anne E. Marteel-Parrish, Martin A. Abraham

• Publisher: Wiley-AIChE
• Year: 2013
• ISBN:
  9781118720264
• Edition: 1
• Topic: Scienze fisiche
• Subtopic: Chimica organica

Promotes a green approach to chemistry and chemical engineering for a sustainable planet

With this text as their guide, students will gain a new outlook on chemistry and engineering. The text fully covers introductory concepts in general, organic, inorganic, and analytical chemistry as well as biochemistry. At the same time, it integrates such concepts as greenhouse gas potential, alternative and renewable energy, solvent selection and recovery, and ecotoxicity. As a result, students learn how to design chemical products and processes that are sustainable and environmentally friendly.

Green Chemistry and Engineering presents the green approach as an essential tool for tackling problems in chemistry. A novel feature of the text is its integration of introductory engineering concepts, making it easier for students to move from fundamental science to applications.

Throughout this text, the authors integrate several features to help students understand and apply basic concepts in general chemistry as well as green chemistry, including:

• Comparisons of the environmental impact of traditional chemistry approaches with green chemistry approaches
• Analyses of chemical processes in the context of life-cycle principles, demonstrating how chemistry fits within the complex supply chain
• Applications of green chemistry that are relevant to students' lives and professional aspirations
• Examples of successful green chemistry endeavors, including Presidential Green Chemistry Challenge winners
• Case studies that encourage students to use their critical thinking skills to devise green chemistry solutions

Upon completing this text, students will come to understand that chemistry is not antithetical to sustainability, but rather, with the application of green principles, chemistry is the means to a sustainable planet.

1

UNDERSTANDING THE ISSUES

1.1 A BRIEF HISTORY OF CHEMISTRY

Chemistry (from Egyptian kēme (chem), meaning “earth”[1]) is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions.

Chemists and chemical engineers have the tools to design essential molecules, and impart particular properties to these molecules so they play their expected role in an efficient and standalone manner. Chemicals are used throughout industry, research laboratories, and also in our own homes. Discoveries and development of fundamental chemical transformations contribute to longer, healthier, and happier lives. We need chemistry and chemicals to live.

However, chemophobia and the unnatural perception that all chemicals are bad have origins in the remote past, but are still in people’s minds today. The following historical background sheds some light on the evolution of the environmental movement.

1.1.1 Fermentation: An Ancient Chemical Process

Fermentation, an original chemical process that was discovered in ancient times, led to the production of wine and beer. With relatively crude techniques, a simple enzyme contained in yeast was found to catalyze the conversion of sugar into alcohol. Control of the ingredients in the fermentation broth would impact the flavor of the alcohol, and the effectiveness of the conversion was controlled by the length of time the fermentation was allowed to proceed and the temperature of the reaction.

Today, ethyl alcohol, acetic acid, and penicillin are produced through fermentation processes. Separation of the product (which is usually a dilute species in an aqueous solvent) and recycle of the enzyme is required to make these processes operate economically.

1.1.2 The Advent of Modern Chemistry

In the 19th century chemistry was viewed as the “central discipline” around which physics and biology gravitated. The medical revolution with the synthesis of drugs and antibiotics coupled with the development of chemicals protecting crops and the expansion of organic chemistry in every aspect of life increased the life expectancy from 47 years in 1900 to 75 years in the 1990s and to over 80 years in 2007.

Chemistry has contributed greatly to improve the quality of human life. For many years, manufacturers took the approach that the world is big and chemical production is relatively small, so chemicals could be absorbed by the environment without effect. The high value of the chemicals produced created an atmosphere in which the manufacturers believed that successful production was the only concern, and control of their waste stream was irrelevant to success. Eventually, the public developed concerns about the impact of chemicals on health and the environment.

1.1.3 Chemistry in the 20th Century: The Growth of Modern Processes

In the 20th century the growth of chemical and allied industries was unprecedented and represented the major source of exports in the most powerful nations in the world. Among some of the major exports were chemicals derived from the petrochemical, agricultural, and pharmaceutical industries.

1.1.3.1 Petrochemical Processes

In the 19th century, oil was discovered. Originally extracted and refined to produce paraffin for lamps and heating, oil was rapidly adopted as a source of energy in motor cars. Eventually, techniques were developed that allowed oil to be converted to chemicals, and its availability and financial accessibility allowed the petrochemical industry to grow at a tremendous rate. Developments in the modern plastics, rubbers, and fibers industries led to significant demand growth for synthetic materials.

TABLE 1.1. End Products Made from Common Hydrocarbons

Hydrocarbons	Trade Names	Consumer Products
Ethylene (C2H4)	Polyethylene (Polythene)	Plastic bags, wire and cable, packaging containers, plastic kitchen items, toys
Propylene (C3H6)	Polypropylene (Vectra, Herculon)	Carpets, yogurt pots, household cleaners’ bottles, electrical appliances, rope
Butadiene (C4H6)	Copolymers with butadiene named Nipol, Kyrnac, Europrene	Synthetic rubber for automobile tires, footwear, golf balls
Benzene (C6H6)	Polystyrene	Insulation, cups, packaging for carry-out foods
Toluene (C7H8)	Polyurethanes	Furniture, bedding, footwear, varnishes, adhesives
Paraxylene (C8H10)	Polyesters	Clothes, tapes, water and soft drink bottles

Fossil resources, which include oil, natural gas, and coal, are the major sources of chemical products impacting our modern lives. Hydrocarbons, the principal components of fossil resources, can be transformed through a number of refining processes to more valuable products. One of these processes is called cracking, in which the long carbon chains are cracked (broken down) into smaller and more useful fractions. After these fractions are sorted out, they become the building blocks of the petrochemical industry such as olefins (ethylene, propylene, and butadiene) and aromatics (benzene, toluene, and xylenes). These new hydrocarbon products are then transformed into the final consumer products. Table 1.1 gives examples of some end products made from hydrocarbons.

More than 10 million metric tons of oil is used in the world every day. The increasing world population (expected to reach 10 billion people in a few decades) puts increasing pressure on this nonrenewable resource to provide the raw material for a growing consumer demand. Fossil resources also produce 85% of the world’s energy supply, and the growing population and increasing energy consumption puts even greater demand on their use. Because society is increasing its consumption of this nonrenewable resource, identification of alternative, renewable sources of energy and raw materials for chemicals is emerging as one of the biggest challenges for the 21st century.

1.1.3.2 Agriculture and Pesticides

As the rate of population grew in the 20th century, the demand for food increased dramatically. Production kept up with demand through the use of new technologies such as the synthesis of fertilizers, pesticides, new crop varieties, and extensive irrigation [2]. To provide the necessary cropland, forests were destroyed and prairies and similar types of rangelands were converted.

As new lands were made available for farming, it was discovered that most soils lacked sufficient nitrogen to permit maximum plant growth. Through the nitrogen cycle, bacteria convert atmospheric nitrogen to ammonia and nitrates, which are then absorbed by the plants through their roots. In a natural environment, nitrogen-containing compounds are eventually returned to the soil when plants die and decompose. A natural balance is achieved between the amount of nitrogen removed from the soil through plant growth and the amount returned to the soil through decay. In order to boost the amount of nitrogen required for plant growth, synthetic inorganic fertilizers containing ammonia and nitrates were often applied by farmers. The excessive addition of fertilizers led to runoff of the extra nitrogen-containing compounds in the rivers and lakes and damage to the environment.

More damage to the environment and human health resulted from the development of pesticides to control the impact of insects and other pests. Health issues associated with pesticides were substantial, especially in less developed countries where farmers and employees of the pesticide industries did not take adequate precautions when spraying pesticides. The worst insecticide accident happened in 1984 in Bhopal, India (see Highlight 1.4). One well-known pesticide based on inorganic arsenic salts was used extensively to destroy rodents, insects, and fungi. However, arsenic was recognized as a carcinogen, increasing the risk of bladder cancer. Pesticides based on organophosphates (organic compounds containing phosphorus) were also developed but are especially toxic to human health. A further problem arose when some pests and insects developed resistance to pesticides following repeated uses. In order to overcome the resistance, a more potent pesticide would be applied until resistance was gained, and the cycle repeats. The farmers found themselves on a “pesticide treadmill” [3, p. 451].

A third factor contributing to the increase of grain production was the development of new varieties of crop plants. To produce high-yielding crops, selective cross-breeding was introduced into India, South America, Africa, and other developing countries. Genetically engineered crops started to appear on grocery store shelves in the late 20th century. Through enzymatic transformations, the structure of DNA in living organisms can be modified. Molecular biologists are able to incorporate wanted genes into the DNA of living organisms. For example, in 1994, the first genetically engineered tomato was marketed. Tomatoes are known to be sensitive to frost. To postpone the ripening process, scientists incorporated the “antifreeze” gene of a flounder into a tomato. However, the sales were not profitable so the first genetically engineered tomato was removed from the market. Today, the U.S. Food and Drug Administration (FDA) approves the sale of genetically modified canola, corn, flax, cotton, soybeans, squash, and sugar beet, just to name a few.

Likewise, irrigation systems have been put in place all over the world to make use of arid lands. In hot and humid climates and in the absence of rain, this practice created an accumulation of salts on the soil surface due to the high evaporation rate of water from the soil. The only way to remove excess salts on the surface is to irrigate more. The increase in the salinity of the irrigation water, often recycled through many irrigation cycles, led to a decrease in the productivity of crops, especially beans, carrots, and onions [3, p. 236].

Meeting the food demand of the 21st century is an increasingly difficult challenge, since these new technologies have already been exploited to their maximum potentials, especially in developed countries. Food shortages are expected due to grain productivity decline and growth in the world demand for food.

1.1.3.3 Pharmaceuticals

The modern pharmaceutical industry was born in the 20th century with the mass production of new medicines. The fast growing field of biotechnology and biocatalysis provided the ability to explore new technological applications through a vital drug discovery process. Among the highlights of the pharmaceutical sector in the 20th century were the discovery and development of insulin, new antibiotics to fight a greater range of diseases, and the development of new drugs for cancer treatment.

The discovery of insulin, a hormone that regulates blood sugar, changed the lives of diabetic patients whose malfunctioning pancreas leads to an inability to produce the required hormone. In 1921, Canadian physician Frederick Banting first isolated the hormone. In the laboratories of Eli Lilly, now the 10th largest pharmaceutical company in the world, the process was developed to extract, purify, and mass produce insulin. Insulin was introduced commercially in 1923.

The second famous discovery happened in 1928 when Dr. Alexander Fleming, a bacteriologist at London’s Saint Mary’s Hospital, found that a “magic mold” resisted the action of bacteria. He named the mold penicillin. It was not until 1940 that penicillin was developed into a therapeutic agent by Oxford University scientists Howard Florey and Ernest Chain. Unfortunately, an insufficient supply of penicillin existed until the beginning of World War II, when several U.S.-based companies purified and mass produced penicillin to treat the wounds of U.S. soldiers on the battlefield. A long series of new antibiotics followed in the 1950s, known as the “decade of antibiotics.”

Substantial progress in the fight against cancer also occurred during the 20th century. Named karkinos by Hippocrates, a Greek physician and the father of medicine, cancer found its origin as early as 1500 BCE. Although typically grouped together, there are a wide variety of cancerous diseases. When cells in our organs continue to multiply without any need for them, a mass or growth called tumor appears. These masses of cells can either be benign (noncancerous, not life threatening, and easily removed) or malignant (cancerous, spread to tissue and organs). Malignant cells can be identified by magnetic resonance imaging (MRI) used in radiology to distinguish pathologic tissue such as a brain tumor from normal tissue. The fight against cancer was pursued with assiduity in the 20th century when chemotherapy and radiation therapy were discovered. The first chemotherapy agent for cancer was actually mustard gas used in World War I. However, the gas killed both healthy and cancerous cells. Since then, many antimetabolites (“any substance that interferes with growth of an organism by competing with or substituting for an essential nutrient in an enzymatic process” [4]) have been developed and deaths from all cancers combined declined.

John E. Niederhuber, M.D., the 13th director of the National Cancer Institute, opined on the growth of biotechnology and its impact on human health. “The continued decline in overall cancer rates documents the success we have had with our aggressive efforts to reduce risk in large populations, to provide for early detection, and to develop new therapies that have been ...