Green chemistry and engineering a practical design approach

PREFACE xi1 Green Chemistry and Engineering in the Context of Sustainability 3 1.2 Green Chemistry, Green Engineering, and Sustainability 61.3 Until Death Do Us Part: A Marriage of Disci

A Practical Design Approach

CONCEPCIO´N JIME´NEZ-GONZA´LEZ

DAVID J C CONSTABLE

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.

Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written

permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness

of the contents of this book and specifically disclaim any implied warranties of merchantability or

fitness for a particular purpose No warranty may be created or extended by sales representatives or written sales materials The advice and strategies contained herein may not be suitable for your situation You should consult with a professional where appropriate Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential,

or other damages.

For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.

Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic formats For more information about Wiley products, visit our web site

at www.wiley.com

Library of Congress Cataloging-in-Publication Data:

Jimenez-Gonzalez, Concepcio´n Conchita.

Green chemistry and engineering : a practical design approach / Concepcio´n Conchita

Jimenez-Gonzalez, David J C Constable.

p cm.

Includes index.

ISBN 978-0-470-17087-8 (cloth)

1 Environmental chemistry–Industrial applications 2 Sustainable engineering I.

Constable, David J C., 1958- II Title.

PREFACE xi

1 Green Chemistry and Engineering in the Context of Sustainability 3

1.2 Green Chemistry, Green Engineering, and Sustainability 61.3 Until Death Do Us Part: A Marriage of Disciplines 13

2.4 The San Destin Declaration: Principles of Green Engineering 31

3 Starting with the Basics: Integrating Environment, Health,

v

3.3 Safety Issues of Importance 62

3.5 Integrated Perspective on Environment, Health, and Safety 70

4.1 General Considerations About Green Chemistry and Engineering

PART II THE BEGINNING: DESIGNING GREENER, SAFER

6 Material Selection: Solvents, Catalysts, and Reagents 133

Green Chemistry Impacts 191

8.4 Examples of Products Obtained from Bioprocessing 216

PART III FROM THE FLASK TO THE PLANT: DESIGNING GREENER,

SAFER, MORE SUSTAINABLE MANUFACTURING

9.1 Why We Need Mass Balances, Energy Balances, and Process

12 Process Synthesis 331

12.2 Process Synthesis Approaches and Green Engineering 333

13.1 Process Integration: Synthesis, Analysis,

14.3 Inherent Safety in Route Strategy and Process Design 398

17.1 Life Cycle Management 49317.2 Where Chemical Trees and Supply Chains Come From 495

18.2 Environmental Life Cycle Emissions and Impacts

19.2 Environmental Fate Information: Physical Properties 55019.3 Environmental Fate Information: Transformation and Depletion

19.6 Environmental Life Cycle Impacts of Waste Treatment 565

20.3 Relationship Between Life Cycle Inventory/Assessment and Total

20.6 Total Cost Assessment in a Green Chemistry Context 589

21.3 Bioplastics and Biopolymers 605

24.2 Principles and Concepts of Industrial Ecology and Design 655

25.1 Can Green Chemistry and Green Engineering Enable Sustainability? 670

In the last decade, interest in and understanding of green chemistry and green engineeringhave increased steadily beyond academia and into the business world Industries withindifferent sectors of the economy have made concerted efforts to embed these concepts intheir operations Given our experience with green chemistry and green engineering in thepharmaceutical industry, we were initially approached by the publishers to edit a book ongreen chemistry in the pharmaceutical industry This was a worthy proposal, but we feltthat we had a greater opportunity and worthier endeavor to produce a book that wouldattempt to fully integrate green chemistry and green engineering into the academiccurricula and that at the same time could serve as a practical reference to chemists andengineers in the workplace.

Green chemistry and green engineering are still relatively new areas that have not beencompletely ingrained in traditional chemistry and engineering curricula, but classes andeven majors in these topics are becoming increasingly common However, most classes ingreen chemistry are taught from an environmental chemistry perspective or a syntheticorganic chemistry perspective, with neither approach addressing issues of manufacturing ormanufacturability of products Green engineering classes, on the other hand, tend toemphasize issues related to manufacturing, but do not treat reaction and process chemistrysufficiently, so these disciplines still seem to be disconnected This lack of integrationbetween chemistry, engineering, and other key disciplines has been one of the mainchallenges that we have had within the industrial workplace and in previous academicexperiences

As a consequence of these experiences, we decided to write this book to bridge the greatdivide between bench chemistry, process design, engineering, environment, health, safety,and life cycle considerations We felt that a systems-oriented and integrated approach wasneeded to evolve green chemistry and green engineering as disciplines in the broader context

of sustainability To achieve this, we have organized the book in five main sections

xi

. Part I Green Chemistry and Green Engineering in the Movement Toward ability Chapters 1 to 4 set the broader context of sustainability, highlighting the keyrole that green chemistry and green engineering have in moving society toward theadoption of more sustainable practices in providing key items of commerce.

Sustain-. Part II The Beginning: Designing Greener, Safer Chemical Synthesis Chapters 5 to 8address the key components of chemistry that will contribute to the achievement ofmore sustainable chemical reactions and reaction pathways They also provide anapproach to materials selection that promotes the overall greenness of a chemicalsynthesis without diminishing the efficiency of the chemistry or associated chemicalprocess

. Part III From the Flask to the Plant: Designing Greener, Safer, More SustainableManufacturing Processes Chapters 9 to 15 provide those key engineering conceptsthat support the design of greener, more sustainable chemical processes

. Part IV Expanding the Boundaries: Looking Beyond Our Processes Chapters 16 to

20 introduce a life cycle thinking perspective by providing background and contextfor placing a particular chemical process in the broader chemical enterprise,including its impacts from raw materials extraction to recycle/reuse or end-of-lifeconsiderations

. Part V What Lies Ahead: Beyond the Chemical Processing Technology of Today orDelivering Tomorrow’s Products More Sustainably Finally, Chapters 21 to 25 providesome indication of trends in chemical processing that may lead us toward moresustainable practices

To help provide a practical approach, we have included examples and exercises that willhelp the student or practitioner to understand these concepts as applied to the industrialsetting and to use the material in direct and indirect applications The exercises are intended

to make the book suitable for both self-study or as a textbook, and most exercises are derivedfrom our professional experiences

The book is an outgrowth of our experience in applied and fundamental research,consulting, teaching, and corporate work on the areas of green chemistry, green engineering,and sustainability It is intended primarily for graduate and senior-level courses in chemistryand chemical engineering, although we believe that chemists and engineers working inmanufacturing, research, and development, especially in the fine-chemical and pharmaceu-tical areas, will find the book to be a useful reference for process design and reengineering.Our aim is to provide a balance between academic needs and practical industrial applications

of an integrated approach to green chemistry and green engineering in the context ofsustainability

Acknowledgments

We thank all our colleagues who have contributed directly or indirectly to our journeytoward sustainability, and whose ideas and collaborations throughout the years havecontributed to our own experience in the areas of green chemistry and green engineering

We also express our gratitude to GlaxoSmithKline, in general, and to James R Hagan, inparticular, for their support and encouragement

Aided Process-Product Engineering Center, Department of Chemical and BiochemicalEngineering at the Technical University of Denmark, for their comments, reviews, andcontributions to Chapter 12; to Mariana Pierobon and BASF for their helpful comments andfor allowing us to use one of BASF’s eco-efficiency assessments as an example in the lifecycle chapters; to Sara Conradt for allowing us to use a sample of her masters thesis as anexample of LCA outputs; and to Tom Roper and John Hayler at GSK for their feedback ongreen chemistry throughout the years Finally, we want to thank Chemical Engineeringmagazine, the American Chemical Society, Springer Science and Business Media, Elsevier,John Wiley & Sons, the Royal Society of Chemistry, and Wiley-VCH for permission toreproduce some printed material.

CONCEPCIO ´ NJIM ENEZ-GONZ  ALEZ

DAVIDJ C CONSTABLE

December 2009

GREEN CHEMISTRY AND GREEN

ENGINEERING IN THE MOVEMENT

TOWARD SUSTAINABILITY

1

GREEN CHEMISTRY AND ENGINEERING

IN THE CONTEXT OF SUSTAINABILITY

What This Chapter Is About Green chemistry and green engineering need to be seen as anintegral part of the wider context of sustainability In this chapter we explore green chemistryand green engineering as tools to drive sustainability from a triple-bottom-line perspectivewith influences on the social and economic aspects of sustainability

Learning Objectives At the end of this chapter, the student will be able to:

. Understand the need for the development of greener chemistries and chemicalprocesses

. Identify sustainability principles and associate standard chemical processes with thethree areas of sustainability: social, economic, and environmental

. Identify green chemistry and green engineering as part of the tools used to drivesustainability through innovation

. Understand the need for an integrated approach to green chemistry and engineering

1.1 WHY GREEN CHEMISTRY?

If industrial chemical reactions were that straightforward, chemists and engineers wouldhave significantly more time on their hands and significantly less excitement and fewer longhours at work Chemists know that this hypothetical reaction is not the case in real life, as theyhave less-than-perfect chemical conversions, competing reactions to avoid, hazardousmaterials to manage, impurities in raw materials, and the final product to reduce Engineersknow that in addition to conquering chemistry, there are by-products to separate, waste totreat, energy transfer to optimize, solvent to purify and recover, and hazardous reactionconditions to control At the end of this first reality check, we see that our initial reaction is amuch more complicated network of inputs and outputs, something that looks more likeFigure 1.1.

Green chemistry and green engineering are, in a very simplified way, the tools andprinciples that we use to ensure that our processes and chemical reactions are more efficient,safer, cleaner, and produce less waste by design In other words, green chemistry and greenengineering assist us in first thinking about and then designing synthetic routes and processesthat are more similar to the hypothetical reaction depicted in equation (1.1) than to the moreaccurate reflection of current reality shown in, Figure 1.1

What are the drivers in the search for greener chemistries and processes? Engineers andscientists have in their capable hands the possibility of transforming the world bymodifying the materials and the processes that we use every day to manufacture theproducts we buy and the way we conduct business However, innovation and progressneed to be set in the context of their implications beyond the laboratory or themanufacturing plant With the ability to effect change comes the responsibility to ensurethat the new materials, processes, and designs have a minimum (or positive) overallenvironmental impact In addition, common sense suggests that there is a strong businesscase for green chemistry and engineering: linked primarily to higher efficiencies, betterutilization of resources, use of less hazardous chemicals, lower waste treatment costs, andfewer accidents

Need to control exposure, separate,

recovery, not in salable product Energy expenditure, potential for safety issues

Creation of competing reactions reactant

nonvaluable by-products = waste

disposal Toxic?

FIGURE 1.1 Simplified vision of some of the challenges and realities of designing a chemicalsynthesis and process

chloride brine,1as illustrated by the following net reaction:

2KClþ 2H2O! 2KOH þ Cl2þ H2How is this simple inorganic reaction different from the more complex challenges of the realworld? Identify some of the green chemistry/green engineering challenges

Solution The electrolysis reaction can be carried out in diaphragm, membrane, or mercurycell processes The complexity of the reactions depend on the process that is used Let’sexplore the mercury cell process, which has, historically, been the most commonly usedmethod to produce chlorine.1,2In this case, potassium chloride is converted to a mercuryamalgam in a mercury cell evolving chlorine gas The depleted brine is recycled to dissolvethe input KCl The mercury amalgam passes from the mercury cell to the denuder In thedenuder, fresh water is added for the reaction and as a solvent for the KOH Hydrogen gas isevolved from the reaction and mercury is recycled to the electrolysis cell:

Mercury cell: KCl

potassium chloride

þ Hgmercury! K  Hg

potassium mercury amalgam

þ 0:5Cl2 chlorine

Denuder: K  Hg

potassium mercury amalgam

þ H2Owater ! KOHpotassium hydroxide

þ 0:5H2 hydrogenþ Hg

mercury

Our simple net reaction has become a bit more complex, but it does not end there We’venot talked about a key input— energy Electricity is required to drive the reaction forward;

it represents the major part of the energy requirement for these types of reactions, and there is

a need to optimize it As a matter of fact, as of 2006 the chlor-alkali sector was the largest user

of electricity in the chemical industry.2

But energy is not the only thing that we need to worry about In addition to energy inputs,there is a need to eliminate impurities To do that, the brine can be treated with potassiumcarbonate3to precipitate magnesium and heavy metals, and barium carbonate is often used toprecipitate sulfates.4Also, hydrochloric acid needs to be added, as an acidic pH is required todrive the reaction to produce the desired chlorine gas, which can then be recovered from thesolution, as shown in the following equilibrium reaction:

Hþþ OClþ HCl > H2Oþ Cl2Besides using a large quantity of electricity, we have to worry about potential emissions fromthe reaction Mercury is present in the reaction cell and the purged brine Mercury emissionsfrom the cell and the brine have long been a target for significant reduction The purged brine

is typically treated with sodium hydrosulfide to precipitate mercury sulfide, and the containing solid wastes need to be sent for mercury recovery Other emission concernsinclude management of the environmental, health, and safety (EHS) challenges related to thegases in the reactions Both the chlorine and hydrogen gas streams must be processed further.Chlorine is cooled and scrubbed with sulfuric acid to remove water, followed by compressionand refrigeration The hydrogen gas is cooled to remove water, impurities, and mercury,

mercury-followed by further cooling or treatment with activated carbon for more complete mercuryremoval.5In addition, hydrogen is often burned as fuel at chlor-alkali plants.

The membrane process was introduced in the 1970s and it is more energy efficient andmore environmentally sustainable, which is making it the technology of choice However, atypical mercury-based plant can contain up to 100 cells and has an economic life span of 40 to

60 years A long phase-out is required to convert an existing mercury plant For example, as

of 2005, 48% of the European chlor-alkali capacity was mercury cell–based.2

Additional Point to Ponder Chemistries and processes described in most textbooksnormally don’t give you all the information you need to consider the mass and energyinputs and outputs associated with a given reaction In reality you won’t always have the datayou need and will have to use estimations to generate data, run experiments, perhaps use

“nearest neighbor” approaches and/or make assumptions based on your experience.Sometimes, you will just have to use “simple” common sense

1.2 GREEN CHEMISTRY, GREEN ENGINEERING, AND SUSTAINABILITY

The modern understanding of sustainability began with the United Nations World mission on Environment and Development’s report Our Common Future,6also known as theBrundtland Report The Brundtland Commission described sustainable development as

Com-“development that meets the needs of the present without compromising the ability of futuregenerations to meet their own needs.” What does this actually mean? This definition doesn’tgive us many clues or supply much practical guidance as to how to implement sustainabledevelopment or move toward more sustainable activities, but it does provide us with apowerful aspiration It has been up to society collectively and up to us as individuals todevelop guidance and tools that will help us to design systems and processes that have thepotential to achieve the type of development described in the definition

The first thing to remember is that sustainability or sustainable development is a complexconcept with which many people are still attempting to come to terms In 1998, JohnElkington, one of the early innovators of sustainable development, coined the phrase triplebottom line.7

Elkington did this in an attempt to make sustainable development moreunderstandable and palatable to business people, to encourage them to see it as a logicalextension of the traditional business focus on economic performance By using this term,Elkington was trying to highlight the need to consider the intricate nterrelationships amongenvironmental, social, and economic aspects of human society and the world In a way,sustainability can be seen as a very delicate balancing act among these three factors, and notalways with a strong one-to-one relationship Table 1.1 provides a summary of severalapproaches to sustainable development principles It should be noted that the Carnoulesstatement includes an organizational principle framework, in addition to the overarchingsocial aspects widely recognized to be an integral part of sustainability This organizationalprinciple is useful when relating the operational aspects of sustainability within the sphere ofcontrols defined by company culture and policy

When talking about sustainability, one cannot focus on only a single aspect, as thisnecessarily limits and biases one’s view For a system to be sustainable, there is the need tobalance, insofar as possible, social, economic, and environmental aspects, ideally havingeach area “in the black,” that is, with no single aspect optimized to the detriment of the others

to establish policies, programs, and practices for conducting operations

in an environmentally sound manner.

Integrated management:

To integrate these policies, programs, and practices fully into each business as

an essential element of management in all its functions.

Process of improvement:

To continue to improve corporate policies, programs, and environmental performance, taking into account technical developments, scientific understanding, consumer needs, and community expectations, with legal regulations as a starting point; and to apply the same environmental criteria internationally.

Responsible Care Policy: We will have a health, safety, and Environmental (HS&E) policy that will reflect our commitment and

be an integral part of our overall business policy.

Employee involvement: We recognize that the involvement and commitment of our employees and associates will be essential to the achievement of our objectives We will adopt communication and training programs aimed at achieving that involvement and commitment.

Experience sharing: In addition to ensuring that our activities meet the relevant statutory obligations, we will share experience with our industry colleagues and seek to learn from and incorporate best practice into our own activities.

Legislators and regulators:

We will seek to work in cooperation with legislators and regulators.

Environmental Principles Protect ecosystems’ functions and evolution.

Enhance (genetic, species, and ecosystem) biodiversity.

Reduce anthropogenic resource throughput and degradation of land and sea.

Minimize the burden for the environment: Improve resource productivity (mass, energy, land).

Minimize the impacts on health and environment:

minimize the outputs of known (eco)toxics.

Minimize damage for the economy: reduce costs related to environmental degradation (damage costs, compliance costs, administrative costs, avoidance costs, etc.).

Social Principles Social cohesion and social security.

Insist on rights of humanity and nature to coexist in a healthy, supportive, diverse, and sustainable condition.

Recognize interdependence The elements of human design interact with and depend on the natural world, with broad and diverse implications at every scale Expand design considerations to recognize even distant effects.

Respect relationships between spirit and matter Consider all aspects of human settlement, including community, dwelling, industry, and trade in terms of existing and evolving connections between spiritual and material

consciousness.

System condition 1:

Substances from the Earth’s crust must not increase in nature systematically In a sustainable society, natural resources should not be extracted

at a faster pace than their re-deposit into the ground.

System condition 2:

Substances produced

by society must not increase in nature systematically.

In a sustainable society, man-made substances should not be produced

at a faster pace than they can be naturally degraded or re-deposited into the ground.

System condition 3: The physical basis for the productivity and diversity of nature must not be diminished systematically.

To support and respect the protection of internationally proclaimed human rights.

To avoid complicity in human rights abuses.

To uphold freedom of association and the effective recognition of the right to collective bargaining.

To eliminate all forms of forced and compulsory labor.

To effectively abolish child labor.

To eliminate discrimination with respect to employment and occupation.

To support a precautionary approach to environmental challenges.

To promote greater environmental responsibility.

environmentally responsible manner.

Prior assessment: To assess environmental impacts before starting a new activity or project and before decommissioning a facility or leaving a site.

Products and services: To develop and provide products or services that have no undue environmental impact and are safe in their intended use, that are efficient in their consumption of energy and natural resources, and that can be recycled, reused, or disposed of safely.

Customer advice: To advise and, where relevant, educate customers, distributors, and the public

in the safe use, transportation, storage, and disposal of products provided; and to apply similar considerations to the provision of services.

Process safety: We will assess and manage the risks associated with our processes.

Product stewardship: We will assess the risks associated with our products and seek

to ensure that these risks are properly managed throughout the supply chain through stewardship programs involving our customers, suppliers, and distributors.

Resource conservation: We will work to conserve resources and reduce waste

in all our activities.

Stakeholder engagement: We will monitor our HS&E performance and report progress to stakeholders;

we will listen to the appropriate communities and engage them in dialogue about our activities and our products.

Healthy and secure shelter.

Readjusted demand for resource consumption, and the environmental impact

of household consumption.

Secure environmental quality for the health of human beings.

Economic Principles Sufficient supply and goods and services

Efficient wealth creation Economic system’s evolution and competitiveness Enhance the distributional justice (equity principle) Efforts (paid and unpaid) should be devoted fairly to generate sustainable incomes.

Provide opportunities for paid labor to all willing and able

to work.

Increase knowledge intensity.

Refocus innovation and adapt its speed to societal

Accept responsibility for the consequences of design decisions on human well-being, the health of natural systems, and their right

to coexist.

Create safe objects of long-term value Do not burden future generations with requirements for maintenance or vigilant administration

of potential danger due

to the careless creation

of products, processes,

or standards.

Eliminate the concept of waste Evaluate and optimize the full life cycle of products and processes to approach the state of natural systems in which there

is no waste.

Rely on natural energy flows Human designs should, like the living world, derive their creative forces from perpetual solar income.

Incorporate this energy efficiently and safely

In a sustainable society, nature’s productivity should not be diminished in either quality or quantity, nor should more be harvested than can be recreated.

System condition 4:

We must be fair and efficient in meeting basic human needs.

In a sustainable society, basic human needs must be met with the most resource-efficient methods possible, including the just distribution of resources.

To encourage the development and diffusion of environmentally friendly technologies.

into consideration the efficient use of energy and materials, the sustainable use of renewable resources, the minimization of adverse environmental impact and waste generation, and the safe and responsible disposal of residual wastes.

Research: To conduct or support research on the environmental impacts of raw materials, products, processes, emissions, and wastes associated with the enterprise and on the means

of minimizing such adverse impacts.

Precautionary approach: To modify the manufacture, marketing, or use of products or services or the conduct of activities, consistent with scientific and technical understanding, to prevent serious or irreversible environmental degradation.

the principles of responsible care and which will be subject to a formal verification procedure.

Past, present, and future:

Our responsible care management systems will address the impact of both current and past activities.

Social Principles Ethical trade: to ensure that all business, wherever companies trade, is conducted to the highest global ethical standards.

Public understanding: to play their part in helping people understand and appreciate relevant science and technology.

Part of the community: to play

an active role in their communities by interacting with schools, local government, and other bodies.

development.

Improve societal interchange, communication, and intercultural learning.

Protect cultural diversity Achieve distributional fairness and justice, equity and sufficiency.

Develop anticipatory capacities for the democratic process.

solve all problems.

Those who create and plan should practice humility in the face of nature Treat nature as

a model and mentor, not as an inconvenience to be evaded or controlled.

Seek constant improvement by the sharing of knowledge.

Encourage direct and open communication among colleagues, patrons, manufacturers, and users to link long-term sustainable considerations with ethical responsibility, and reestablish the integral relationship between natural processes and human activity.

(continued )

Alcoa 8

International Chamber

Contractors and suppliers: To promote the adoption of these principles by contractors acting on behalf

of the enterprise, encouraging and, where appropriate, requiring improvements in their practices to make them consistent with those of the enterprise; and to encourage the wider adoption of these principles

by suppliers.

Emergency preparedness: To develop and maintain, where significant hazards exist, emergency preparedness plans in conjunction with the emergency services, relevant authorities, and the local community, recognizing potential transboundary impacts.

Transfer of technology: To contribute to the transfer of environmentally sound technology and management methods throughout the industrial and public sectors.

Employability: to ensure that all employees have access to training and development opportunities to enable them to fulfill their role in the organization and to keep them up to date with the labor market.

Equality of treatment and opportunity: to ensure that all employees are free from discrimination and have the opportunity to develop their careers and themselves, subject only to business needs and personal ability.

Participation: to ensure that all employees have access to the information needed for them to do their job, be consulted about matters that affect them, and have the opportunity to participate, to the appropriate level, in the management of their company.

Balance between work and life:

to provide all employees with the opportunity to balance the requirements of their work and their life outside work so as to enhance work effectiveness and personal well-being.

governmental and intergovernmental programs, and educational initiatives that will enhance environmental awareness and protection.

Openness to concerns: To foster openness and dialogue with employees and the public, anticipating and responding to their concerns about the potential hazards and impacts of operations, products, wastes, or services, including those of transboundary or global significance.

Compliance and reporting:

To measure environmental performance; to conduct regular environmental audits and assessments of compliance with company requirements, legal requirements, and these principles; and periodically

to provide appropriate information to the board of directors, shareholders, employees, the authorities and the public.

shareholders’ expectations and to invest in the future through R&D, capital expenditure, and employee development.

Competitiveness: achieving long-term competitiveness through the spread of international best practice,

in a climate of fair competition Innovation: continuing to research, develop, and market innovative products that help improve economic well-being and quality of life.

Wealth generation: generating wealth, thereby sustaining employment, improving the UK’s trade balance, and contributing to government revenue to fund public expenditure Economic growth: continuing their key role in supporting sustained UK economic growth throughout the entire manufacturing supply chain Resource efficiency: making the most efficient use of resources, whether they be land, water, raw materials, or energy.

One of the most puzzling, challenging, and exciting characteristics in the study ofsustainability is the inherent complexity of the concept There are synergies, trade-offs,

a variety of shared values of what constitutes a sustainable practice, and so on Figure 1.2displays those interrelations graphically

Green chemistry and green engineering represent some of the many concepts, tools,and disciplines that come into play in helping to move society toward more sustainablepractices They do this by focusing scientists and engineers on how to design moreenvironmentally friendly, more efficient, and inherently safer chemistries and manufactur-ing processes However, some might suggest that when talking about green chemistry andgreen engineering in the context of sustainable development, we can honestly say simplythat the primary focus area is what has come to be known as environmental sustainability

Is this really true? Whereas green chemistry and green engineering may be seen as beingrelated primarily to the environmental aspects of sustainability, they also have strong ties

to the eco-environmental (or eco-efficiency) sub-area of sustainability by virtue of the factthat they include resource conservation and efficiency By the same token, green chemistryand green engineering are related to the social aspects of sustainability becausethey promote the design of manufacturing processes that are inherently safer, therebyensuring that workers and residential neighborhoods close to manufacturing sites areprotected

Example 1.2 Explain how reaction (1.1) relates to the three aspects of sustainability

Solution Several of the issues related to green chemistry and green engineering werehighlighted in the solution to Example 1.1 Table 1.2 provides examples of how they relate tothe three aspects of sustainability

Sustainability Vision

FIGURE 1.2 Spheres of action of sustainability

Additional Point to Ponder Most textbook examples and problems have only one correctanswer, although many examples have several possible answers In real-world manufacturingprocesses, it is common to have difficulties in defining what the true problem is—and whenthis is defined, several “not-quite-optimal” answers may be found When this happens, adecision must be made that accounts for or balances all the important factors and, hopefully,leads to the optimal or “best” answer.

1.3 UNTIL DEATH DO US PART: A MARRIAGE OF DISCIPLINES

What does it mean to have an integrated perspective between green chemistry and greenengineering? Just imagine the following not-so-hypothetical scenario A chemist works at alarge company and after years of hard work discovers a novel synthesis to produce a valuablematerial At this point, hundreds of engineering questions are formulated and need to beaddressed, such as:

. What is the best design for the reactor? Which material?

. Does the reaction need to be heated? Cooled? How fast are heating and coolingtransferred?

. What types of separation processes are needed?

. How could the desired purity be achieved?

. How fast is the reaction? Is there a risk of an exothermic runaway?

. What can possibly go wrong? How can we prepare for problems?

Mercury emissions from a cell

and in the purged brine

Worker safety issues related tochlorine and hydrogenmanagement

Jobs and wealth created by apotassium chloride plant

Energy consumption Safety and well-being of

communities adjacent tomanufacturing plant

Economic resources needed tooperate the plant in a safeand efficient mannerWater consumption

Emissions released during

energy production

Potential for processaccidents, incidents, andlost-time injuries

Investment that will benecessary to replacemercury cells for analternative technologyFugitive chlorine emissions

Environmental impacts

resulting from mercury

mining

Working conditions inmercury mines to extractthe metal

. Are there inherent hazards in the materials?

. Are there any incompatibilities with materials?

. How much waste is produced? How toxic is it? Can it be avoided?

. Where should the reactants be procured? Is it more efficient to make them or to buythem?

. How much would this process cost?

. What types of preparations and skills would future operators need?

Imagine how difficult it would be to answer these and other questions if the chemistdoesn’t work closely with a chemical engineer How efficient would the final process be? Totruly understand the impacts of this novel chemistry in the real-world manufacturingenvironment, the chemist will need to involve engineers beginning at the earliest stages

of development

Similarly, a chemical engineer working on transforming a laboratory synthesis into ascalable, effective production process will need to collaborate closely with a chemist tounderstand how the chemical synthesis might be changed A myriad of chemically relatedquestions must be answered to design and scale-up a good manufacturing process:

. What function is the solvent performing in the reaction?

. Are there alternative reaction pathways that can be used to:

Avoid uncontrollable exotherms?

Substitute reactant A for B to avoid safety issues?

Eliminate hazardous reagents?

. If we recirculate part or all of the reaction mother liquors, how much of material X can

be tolerated by the reaction system before we are not able to do this?

. Are there any reactivity issues by introducing solvent Y as a mass separating agent?

. What are the potential side reactions?

. Are there any alternative catalytic methods that we might be able to use?

The decisions that are made in the design of synthetic chemistry pathways affect andeither enable or restrict the engineering opportunities, and vice versa Chemists and chemicalengineers should operate in an integrated fashion if the goal is to design an efficient process,

in the widest sense of the term and in the context of green chemistry and engineering.Hopefully, we have made a good case for integrating green chemistry and greenengineering, but our effort to integrate disciplines is not over Carrying on with ouroriginal scenario, the chemist and engineer have successfully identified a chemical theywant to make and the synthetic route or pathway to be used to make it, and have some idea

of the critical process parameters that they need to focus on if they are to optimize theprocess from a green chemistry and green engineering perspective So, is anything missing?What about knowledge of how the various reactants, reagents, catalysts, solvents,by-products, and so on, used in the process affect living organisms and the environment?One might be tempted to ask who really cares about such things, since most of the materialsmay be consumed in the process and the product we are making is a valuable material thatothers need or want

future generations Human beings have and continue to affect the world in very significantways, and it is critical that all chemists and engineers understand how material choices,process designs, energy use, and so on, affect the world Chemists and engineers need todesign and choose synthetic strategies that minimize the potential for causing short-,medium-, and long-term harm not only to humans, but to other environmental organisms

as well To do this correctly, they need to collaborate with toxicologists and environmental,health, and safety professionals to discuss and develop appropriate options for syntheses Inshort, a host of disciplines are required to bring a product to market appropriately andsuccessfully and to ensure that this is done in a sustainable fashion It is no longer acceptablepractice for chemists to isolate themselves in a laboratory and design reactions that arechemically interesting but, because it is expedient to do so, utilize reagents, reactants, andsolvents that are inherently hazardous

PROBLEMS

1.1 How do green chemistry and green engineering differ from chemistry andengineering?

1.2 Examples 1.1 and 1.2 refer to the environmental, health, and safety challenges related

to mercury, chlorine, and hydrogen What are those challenges?

1.3 The primary route for making copper iodide is by reacting potassium iodide withcopper sulfate:

2CuSO4þ 4KI þ 2Na2S2O3! 2CuI þ 2K2SO4þ 2NaI þ Na2S4O6Identify potential green chemistry and green engineering challenges of the reaction.1.4 From a sustainability framework, identify environmental, social, and economicimpacts derived from the chemistry shown in Problem 1.3

1.5 Using reaction system of example (1.1), provide some examples of how the chemistrycan affect decisions made in engineering

1.6 What are some potential barriers for an effective, close collaboration between achemist and an engineer when designing a novel process Provide some ideas on how

to circumvent these obstacles

REFERENCES

1 Schultz, H., G€unter Bauer, G., Schachl, E., Hagedorn, F Schmittinger, P Potassium pounds In Ullmann’s Encyclopedia of Industrial Chemistry Wiley-VCH, New York, 2000

com-2 Chlorine Industry Report: 2005–2006 Euro Chlor, Brussels, Belgium, 2006

3 McKetta, J Potash, caustic In Kirk–Othmer Encyclopedia of Chemical Technology, 2nd ed.Wiley, New York, 1970

4 U.S Environmental Protection Agency Profile of the Inorganic Chemical Industry EPA Office

of Compliance Sector Notebook Project EPA 310-R-95-004 U.S EPA,Washington, DC, 1995

5 European Commission, 2001 Integrated Pollution Prevention and Control (IPPC) Referencedocument on best available techniques in the chlor-alkali manufacturing industry BREF 12.2001.ftp://ftp.jrc.es/pub/eippcb/doc/cak_bref_1201.pdf.

6 World Commission on Environment and, Development Our Common Future Oxford UniversityPress, Oxford, UK, 1987, p.43

7 Elkington, J Cannibals with Forks: The Triple Bottom Line of 21st Century Business NewSociety Publishers, Gabriola Island, New Brunswick, Canada, 1998, p.416

8 Alcoa 2020 Framework.http://www.alcoa.com/global/en/about_alcoa/sustainability/2020_Framework.asp

9 International Chamber of Commerce The Business Charter for Sustainable Development: 16Principles.http://www.iccwbo.org/policy/environment/id1309/index.html

10 International Council of Chemical Associations Responsible Care Web siblecare.org/page.asp?p¼6341&l¼1, accessed Sept 27, 2009

site.http://www.respon-11 Bartz, P., et al Pignans Set of Indicators Statement: Carnoules Statement on Objectives andIndicators for Sustainable Development Governance for Sustainable Development, Carnoules/Pignans, Provence, France, May 1–4, 2003

12 McDonough and Partners The Hanover Principles McDonough and Partners, Charlottesville,

VA, 1992

13 The Natural Step Web site.http://www.naturalstep.org/, accessed Sept 27, 2009

14 United Nations Global Compact.http://www.unglobalcompact.org/, accessed Sept 27, 2009

“end-we outline the major contributions to the discussion.

Learning Objectives At the end of this chapter, the student will be able to:

. Identify the principles of green chemistry and green engineering

. Understand the interrelationships between the principles of green chemistry and greenengineering

. Contrast the differences between some the principles postulated by Anastas andWarner, Anastas and Zimmerman, Winterton, and the San Destin declaration

. Critique and analyze chemical reactions as related to the principles of green chemistry

2.1 GREEN CHEMISTRY PRINCIPLES

What is a principle, and why do we develop principles? Merriam-Websters, CollegiateDictionary defines a principle as “1a: a comprehensive and fundamental law, doctrine, or

Green Chemistry and Engineering: A Practical Design Approach, By Concepcio´n Jimenez-Gonzalez and David J C Constable

Copyright
2011 John Wiley & Sons, Inc.

17

assumption; b(1): a rule or code of conduct; (2): habitual devotion to right principles

<a man of principle>; c: the laws or facts of nature underlying the working of an artificialdevice.”1 Now that we know what a principle is, why would someone want to haveprinciples for green chemistry and/or green engineering? To answer that question, it may bevaluable to begin by providing just a bit of historical context As the story goes, JohnWarner, formerly on the staff of the research and development department at the PolaroidCorporation, was working on novel chemistries related to dyes used in photographic films.John is not your usual chemist and was aware of many environmental regulations thatmight stand in the way of getting a new product to market (see Figure 2.1) In addition tobeing a great chemist, John is a very creative person, so he began to wonder how he mightdesign novel molecules and chemical synthetic processes to make them in a way that wouldavoid creating and/or using toxic and/or regulated materials along the way With this simplethought in mind, he contacted Paul Anastas, formerly a division head in the Office ofPollution Prevention and Toxics at the U.S Environmental Protection Agency, to discusswhat would now seem to be obvious to many, but at that time, was quite revolutionary:What might the average synthetic chemist do to make molecules that do not harm theenvironment or people? Thus began a continuing dialogue and fruitful collaborationbetween John and Paul that resulted in the publication of the Twelve Principles of GreenChemistry, first published in 1998.2Let’s look at these principles for a moment and thinkabout some of the broader issues and implications that they present We should also askourselves whether or not they promote movement toward more sustainable behaviorsand actions

THE TWELVE PRINCIPLES OF GREEN CHEMISTRY

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 into the finalproduct of all materials used in the process

3 Wherever practicable, synthetic methodologies should be designed to use andgenerate substances that possess little or no toxicity to human health and theenvironment

4 Chemical products should be designed to preserve efficacy of function whilereducing toxicity

5 The use of auxiliary substances (e.g., solvents, separation agents) should be madeunnecessary whenever possible and innocuous when used

6 Energy requirements should be recognized for their environmental and economicimpacts and should be minimized Synthetic methods should be conducted atambient temperature and pressure

7 A raw material feedstock should be renewable rather than depleting whenevertechnically and economically practical

8 Unnecessary derivatization (blocking group, protection–deprotection, temporarymodification of physical/chemical processes) should be avoided whenever possible

9 Catalytic reagents (as selective as possible) are superior to stoichiometric reagents

10 Chemical products should be designed so that at the end of their function they do notpersist in the environment and break down into innocuous degradation products

(continued on page 20)

ARPAA AJA ASBCAA ESAA-AECA FFRAA FEAPRA IRA NWPAA CODRA/NMSPAA FCRPA MMPAA

ANTPA GLCPA ABA CZARA WRDA EDP RECA GCRA GLFWRA HMTUSA NEEA SDWAA SARA BLRA ERDDAA EAWA NOPPA PTSA UMTRCA ESAA QGA NCPA TSCA FLPMA RCRA NFMA CZMAA NEPA EQIA CAA EPA EEA OSHA FAWRAA NPAA

FRRRPA

S OWA DPA

WS RA EA RCFHS A

AQ A

NAWCA

WQA NWPA

MPRS AA ARPA

HMTA

FCMHS A

NHPA WLDA FWCAA FWA AEA

AEPA FIFRA PAA FAWRA MBCA

NPS WA IA NBRA AA RHA YA

TA FWCA BPA

NLRA WPA

AQA FOIA WRPA AFCA FHS A NFMUA

BLBA FWPCA MPRSA CZMA NCA FEPCA PWSA MMPA

ES A TAPA

RCRAA WLDI APA

SWDA CERCLA CZMIA COWLDA FWLCA MPRSAA CAAA CWA SMCRA SDWAA

11 Analytical methodologies need to be further developed to allow for real-timein-process monitoring and control prior to the formation of hazardoussubstances.

12 Substances and the form of a substance used in a chemical process should be chosen

so as to minimize the potential for chemical accidents, including releases, sions, and fires

explo-Source: Adapted from ref 2

2.1.1 Chemistry and Chemical Technology Innovation

See, for example, green chemistry principles 1, 2, 4, 5, 8, and 9 through 12 It should be notedthat chemistry and chemical technology innovations will be required to foster the aims ofeach principle

The first broad implication is that we cannot achieve the aims of these principles if weare not constantly striving for innovation in chemistry and chemical technology innovation.Innovation is at the end of the day what has given us a wide range of materials and productsthat have made our lives more comfortable, and many of those products derive fromchemistry and engineering innovation (Figure 2.2) There are many in the syntheticchemistry and engineering community who believe green chemistry and/or greenengineering to be a “soft” science: that is, not a hard physical scientific or engineeringdiscipline and not quite worthy of “real” academic consideration In actual fact, success ingreen chemistry and engineering presents more difficult challenges and opportunities forinnovation than does much of synthetic organic chemistry It can be argued that greenchemistry and green engineering are indeed “smart” chemistry and engineering, insofar astheir practitioners attempt to design more mass- and energy-efficient processes and to avoiddesign concerns and problems that have plagued chemical processes for decades

Ibuprophen

Rayon Acrylics

molecule such as an azide or acetylene, where the reaction is overwhelmingly namically and kinetically favorable, using whatever solvent you want, in as dilute a solution

thermody-as you like, when you don’t care how you’ll separate the product from the reaction mixture?This is approximately equivalent to being proud of hitting the ocean when you throw a stoneinto it

In contrast to the above, think for a moment about the green chemistry design challenge.You are being asked to make a complex chemical such as a drug or an advanced liquid crystalwith the following design constraints: Use as little extra chemical material as possible, with

as little energy as possible, using compounds that are nontoxic and safe to handle, that areeither biodegradable or recoverable and reusable; and extract the desired product withoutresorting to a large amount of solvent or energy, all the while causing no long-term impacts topeople and or to the environment as you do it

Green chemistry and green technology therefore require the best and the brightest torethink and challenge existing paradigms and push the limits of our knowledge This requirepeople who understand and embrace different academic disciplines within chemistry,engineering, mathematics, and interrelated sciences (e.g., toxicology, biology, bio-chemistry) Imagine, for example, a synthetic organic chemist who understands thermody-namics and kinetics (largely the domain of the physical chemist), but who knows enoughbiochemistry to use enzymatic transformations while making use of process analyticaltechnologies to develop reaction and process understanding and control But this is notenough Chemists and engineers also need to understand enough about other disciplines,such as biology, toxicology, engineering, and geology, that they are able to use chemistrymore knowledgeably and design products, processes, separation technologies, andmanufacturing plants based on greener, safer principles Above all, it requires intellectualflexibility to provide continual innovation and change on a rapid scale

2.1.2 Mass and Energy Efficiency

See, for example, green chemistry principles 1, 2, 5, 6, 8, and 9

Only fairly recently has society become more aware of its impact on the globalenvironment Although it is true that different societies have become more or less aware oflocal or regional impacts on the environment (it is, after all, somewhat difficult to ignore aburning river, deforestation in parts of the northeastern United States, a large explosion,etc.), society is only beginning to become aware that human beings are engaged in earthsystems engineering on a grand scale.3This has been spurred on, perhaps, by publication

of a report by the UN International Panel on Climate Change, which has amassed sufficientand conclusive evidence for the impact on the climate of the increase in carbon dioxide(and other greenhouse gas) concentrations in Earth’s atmosphere.4

If one thinks on a global scale and begins to ask where materials come from to make theproducts that society uses on a daily basis, it is not difficult to see evidence of our insatiableneed for materials of commerce, such as plastics, electronics, clothing, food, and housing.Producing these materials requires increasingly complex global supply chains to meet theneeds and wants of developed and developing nations Increases in the costs of a variety ofkey materials, including fossil fuels for energy and petrochemical feedstocks, are areflection of the demands being placed on supplying chemicals that are increasingly moredifficult to find and transform into the desired materials In addition, the production ofmaterials is intimately related to emissions and resource depletion; in general, the more

materials are needed to produce a good, the more resources that will be needed alongthe supply chain and the more emissions to the air, water, and land that will need to becontrolled.

It could be argued that these trends are pushing society toward increasing material andenergy efficiencies in relation to the material and energy utilized for every product produced.The consequence of low material and energy efficiencies, is, of course, the production ofwaste Roger Sheldon pointed out the relative waste of different industrial sectors and coinedthe phrase E-factor.5The E-factor is related to the mass intensity (MI) as follows:

in all industrial sectors: for example, decrease the mass intensity by at least an order ofmagnitude, if not more It is interesting to note that in many cases, material and energyintensity are very highly correlated If one thinks about this for a moment, it makes a certainintuitive sense that if I decrease the volume of material I am handling, I should use less energy

to produce, use, reuse, and hopefully, dispose of it

Historically, in response to regulations, industry has focused on waste (E-factor) and itselimination, as opposed to preventing waste generation through innovations in chemistry andchemical technology (principle 1) As the U.S Congress opined in 1986, “the majorobstacles to increased waste reduction are institutional and behavioral rather than technical.”Although this is perhaps understandable, in many respects it is unfortunate because a focus

on end-of-pipe solutions is generally costly and only increases the overall mass and energyintensity associated with the production of any product Looking at mass and energyefficiency instead, we can shift our mindset from a treatment, end-of-pipe viewpoint, to aefficiency-increasing, revenue-generating solution

2.1.3 Toxicity and Persistence

See, for example, green chemistry principles 3, 4, and 10

Although a decrease in the amount of energy and materials used for our products iscritical, it is important to understand that the nature of the materials we use is also critically

TABLE 2.1 Mass Intensity of Various Sectors of the Chemical Industry

would want to use a chemical that might render us sterile or incapacitated while consigning

us at some point in the future to a slow painful death by cancer or some other chronic illness(e.g., emphysema, heart disease) Most of us would, of course, say that this is probably not agood thing, yet this is exactly what is done, and generally done safely, on a daily basis We use

a large number of materials that are extremely toxic and difficult to handle because theyhappen to be extremely useful to us chemically However, one might ask if this is a practicethat we wish to continue if we can devise a way to avoid these inherently hazardouschemicals

Legislation such as the Regulation, Evaluation, and Authorization of Chemicals Act(REACH)6approved by the European Commission suggests that at least some societies areinterested in obtaining a better understanding of the environmental, health, and safety (EHS)hazards associated with existing and new chemicals It may be surprising to many readersthat for a large number of chemicals, despite a long history of use in a range of industries, anunderstanding of the EHS hazards associated with many compounds is not sufficient Thelong-term objective of REACH is to obtain that EHS understanding, and once this betterunderstanding is obtained, it is likely that certain chemicals will be banned if the riskassociated with their use is deemed to be too great

In addition to legislative restriction, to operate processes safely with chemicals that arehighly toxic, the appropriate controls should be in place, and the more toxic a material is,the cost to design, set, validate, and maintain the appropriate controls normally increases.Thus, eliminating, substituting, or reducing the amounts of toxic chemicals is also tied toeconomic engineering and the economic bottom line of processes

Green chemistry principles 3, 4, and 10 anticipated chemicals legislation and challengechemists to design molecules and their basic building blocks in such a way that toxicity iseliminated or reduced sufficiently to eliminate high risk These principles are arguablyamong the most difficult for chemists to address, for two reasons First, synthetic chemistsgenerally lack any understanding of toxicity, and for the most part, the relationship ofmolecular structure to toxicity is not well known for many chemicals represented by themyriad of potential combinations of the usual elements (i.e., C, H, O, N, S, Cl) A secondthorny issue is that the efficacy of a molecule, as in pesticides, herbicides, and drugsubstances, among others, is related directly to their ability to exert a toxic effect on atarget organism Indeed, it is a tall order just to find and then make a compound of interest thatworks as intended without adding additional design constraints related to reducing potentialtoxicity!

Finally, after discovering an efficacious molecule of interest with no or minimalassociated toxicity hazards, it must be designed either for reuse or for biodegradation.Implicit in any consideration of biodegradation is an aspect of risk management that isoften poorly understood: chemical fate Chemical fate concerns itself with where amolecule ends up once it is released to the environment, either in air, water, or on land,and will have a different degradation pathway depending on where it is distributed to, as isshown in Figure 2.3 for a household detergent If the compound is chemically degradable

or biodegradable, the degradation by-products must themselves be nontoxic All of thisemphasis on fate and toxicity should drive anyone who wants to introduce a new chemical,

to EHS hazard testing on a very large scale unless the science to model fate andenvironmental effects, explosivity, flammability, and so on, in silico improves dramati-cally For the time being, however, EHS hazard testing is generally the only way that wecan adequately assess potential risks, and this will necessarily increase the cost and

complexity of bringing new products to society Fate and effects are covered in more detail

in Chapter 3

2.1.4 Renewability of Feedstocks

See, for example, green chemistry principles 7 and 10

One of the most exciting areas to think about is how to change the way we make and usethe items we need and want in such a way that all Earth’s species can continue to live at asgood or at a better standard of living Although very exciting for some to think about, this isstill largely simply a nice thought In actual fact, we are living in ways that are notsustainable Human beings are depleting raw materials at an alarming rate or are having

to expend more energy and to inflict greater environmental damage to obtain many of the keyminerals, raw materials, and energy that we require to maintain a Western standard of living.Stated differently, that is a high standard of living for only about one-fourth of Earth’spopulation What about the rest of the human world and of all species that live in what arearguably less than ideal conditions?

In a sense, principle 7 draws a line in the sand and asks chemists and engineers to find,develop, and provide the materials and energy that we need and want in ways that reversecurrent trends This is a very tall order Think about the petrochemical industry for a moment;

it did not start out being a highly efficient industry, but has developed and evolved over thecourse of more than 100 years Chemists have to replicate for a biologically derived supplychain what took 100 years (not counting a few hundred millions of years to form) to optimizeusing a completely different type of feedstock And they must do this in a shorter time frameand without major environmental damage if we are to preserve Earth’s biodiversity andability to maintain large human and nonhuman populations

Some surprise might be registered by seeing that principle 10 is included here, and onemay think that it does not belong in a category about renewability, so some explanation iswarranted This principle is, after all, about biodegradability or persistence Some haveargued, most notably Bill McDonough and Michael Braumgartner in their book Cradle to

Groundwater

Wastewater Treatment plant

Water bodies (river, sea, etc) Agricultural

Soil

Septic system

Municipal system

Direct discharge

Treated discharge

Irrigation Irrigation

Sludge

Air emissions Air emissions

Air emissions

Detergent Detergent

Detergent

FIGURE 2.3 Fate and effects of a common household detergent

nutrients By technical nutrients they mean materials that are used for a certain period

of time, then after a given service life can be collected and returned to their original stateand formed into new products An example they give is replacing paper with apolymeric substance that can be reused repeatedly without a considerable amount of energy

or loss

The point here is that persistence is sometimes a useful characteristic if it is possible tohave a closed-loop recycling system The problem is, of course, that it is very likely that therewill never be a completely closed loop, so some of this material will end up in theenvironment In that case, such materials would have to be either biodegradable orcompletely nontoxic to all organisms In either case, there is still a need to develop materialsthat are renewable and which do not cause environmental degradation A lot of work needs

to be done

Example 2.1 Dimethyl carbonate can be produced by the following reaction8

:2CH3OHþ COCl2! 2NaOH þ CH3OCOOCH3þ 2NaCl þ H2O

Describe which of the green chemistry principles postulated by Anastas and Warner youcould apply to this reaction to improve its greenness given the information provided

Solution

Principle 1 It is better to prevent waste than to treat it or clean up after it is formed In thereaction above, looking at the stoichiometry, there will be an aqueous waste streamwith sodium hydroxide and sodium chloride in significant concentrations The sodiumhydroxide being formed is corrosive and will need to be neutralized and treated Isthere a way to produce the desired carbonate while avoiding the generation of thiswaste stream? How about separating and purifying the final product and the relatedwaste? Is there a way to obtain a final product that is close to being pure?

Principle 2 Synthetic methods should be designed to maximize the incorporation intothe final product of all materials used in the process This is the concept of atomeconomy In reactions with 100% atom economy, all the materials added to thechemistry are incorporated into the final product Can we design an addition reactionthat can produce the carbonate with no by-products?

Principle 3 Wherever practicable, synthetic methodologies should be designed to useand generate substances that possess little or no toxicity to human health and theenvironment This reaction requires phosgene, a highly acute toxicant Can we devise

a different synthetic pathway that avoids the use of phosgene and doesn’t replace itwith another toxic material?

Principle 9 Catalytic reagents (as selective as possible) are superior to stoichiometricreagents This reaction is stoichiometric Is there a way that this chemical can beproduced by catalytic means?

Principle 12 Substances and the form of a substance used in a chemical process should

be chosen so as to minimize the potential for chemical accidents, including releases,explosions, and fires