Paul T. Anastas

Catalysis as a foundational pillar of green chemistry

Abstract Catalysis is one of the fundamental pillars of green chemistry, the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. The design and application of new catalysts and catalytic systems are simultaneously achieving the dual goals of environmental protection and economic benefit. No subject so pervades modern chemistry as that of catalysis. (Ron Breslow, Chemistry Today and Tomorrow: The Central, Useful, and Creative Science ) Green chemistry, the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances, is an overarching approach that is applicable to all aspects of chemistry. From feedstocks to solvents, to synthesis and processing, green chemistry actively seeks ways to produce materials in a way that is more benign to human health and the environment. The current emphasis on green chemistry reflects a shift away from the historic “command-and-control” approach to environmental problems that mandated waste treatment and control and clean up through regulation, and toward preventing pollution at its source. Rather than accepting waste generation and disposal as unavoidable, green chemistry seeks new technologies that are cleaner and economically competitive. Utilizing green chemistry for pollution prevention demonstrates the power and beauty of chemistry: through careful design, society can enjoy the products on which we depend while benefiting the environment. The economic benefits of green chemistry are central drivers in its advancement. Industry is adopting green chemistry methodologies because they improve the corporate bottom line. A wide array of operating costs are decreased through the use of green chemistry. When less waste is generated, environmental compliance costs go down. Treatment and disposal become unnecessary when waste is eliminated. Decreased solvent usage and fewer processing steps lessen the material and energy costs of manufacturing and increase material efficiency. The environmental, human health, and the economic advantages realized through green chemistry are serving as a strong incentive to industry to adopt greener technologies. Developing green chemistry methodologies is a challenge that may be viewed through the framework of the “Twelve Principles of Green Chemistry” [1] . These principles identify catalysis as one of the most important tools for implementing green chemistry. Catalysis offers numerous green chemistry benefits including lower energy requirements, catalytic versus stoichiometric amounts of materials, increased selectivity, and decreased use of processing and separation agents, and allows for the use of less toxic materials. Heterogeneous catalysis, in particular, addresses the goals of green chemistry by providing the ease of separation of product and catalyst, thereby eliminating the need for separation through distillation or extraction. In addition, environmentally benign catalysts such as clays and zeolites, may replace more hazardous catalysts currently in use. This paper highlights a variety of ways in which catalysis may be used as a pollution prevention tool in green chemistry reactions. The benefits to human health, environment, and the economic goals realized through the use of catalysis in manufacturing and processing are illustrated by focusing on the catalyst design and catalyst applications.

The role of catalysis in the design, development, and implementation of green chemistry

Abstract Green chemistry is the design of chemical products and processes which reduce or eliminate the use and generation of hazardous substances. In the last decade, green chemistry has been recognized as a new approach to scientifically based environmental protection. Catalysis has manifested its role as a fundamental tool in pollution prevention. While catalysis has long been utilized in increasing efficiency, yield, and selectivity, it is now also recognized as accomplishing a wide range of green chemistry goals.

Green Chemistry and the Role of Analytical Methodology Development

Green Chemistry has emerged in the 1990s as a way that the skills, knowledge, and talents of chemists can be used avoid threats to human health and the environment in all types of chemical processes. One of the most active areas of Green Chemistry research and development is in analytical methodology development. New methods and techniques that reduce and eliminate the use and generation of hazardous substances through all aspects of the chemical analysis lifecycle are the manifestations of the recent interest in Green Analytical Chemistry.

Life cycle assessment and green chemistry: the yin and yang of industrial ecology

The practice of life cycle assessment has been well documented as a tool for comparing products and processes or comparing various components within a life cycle. This paper addresses the question of how changes can be made once an assessment has been completed, such as identifying the improvements that can be made to address environmental problems and to decrease impacts on human health and the environment. Green chemistry, a fairly recent approach that addresses environmental concerns at a fundamental level, has already demonstrated examples of what we call ‘life cycle innovation’, that is, improvements at all stages of the product or process life cycle. This paper explores various applications of green chemistry methodologies to all stages of a product or process life cycle.

Depolymerization of organosolv lignin to aromatic compounds over Cu-doped porous metal oxides

Isolated, solvent-extracted lignin from candlenut (Aleurites moluccana) biomass was subjected to catalytic depolymerization in methanol with an added pressure of H2, using a porous metal oxide catalyst (PMO) derived from a Cu-doped hydrotalcite-like precursor. The Cu-PMO was effective in converting low-molecular weight lignin into simple mixtures of aromatic products in high yield, without char formation. Gel permeation chromatography was used to track changes in molecular weight as a result of the catalytic treatments and product mixtures were characterized by 1H and 13C NMR spectroscopy. In the temperature range 140–220 °C, unusual C9 catechols were obtained with high selectivity. Lignin conversion of >90% and recovery of methanol-soluble products in yields of was >70% was seen at 180 °C with optimized catalyst and biomass loadings. At 140 °C, 4-(3-hydroxypropyl)-catechol was the major product and could be isolated in high purity.

A principled stance

In Chinese, chemistry is the ‘mixing science’, whereas in Dutch, it’s the ‘separation art’. But whatever their nationality, academic chemists often do not know in detail how the chemicals they use are made, or how their chemistry affects the biosphere. They view industrial chemistry as meat-eaters view the slaughterhouse — the gory details are glossed over and the fate of the waste is ignored. On the other hand, much of the general public recoils at the mere mention of ‘chemicals’, yet we are all clothed, fed, washed and transported by the products of the chemical and pharmaceutical industries. While we benefit from increased quality and length of life thanks to chemicals, the industry that makes them is frequently accused of degrading the Earth. Society relies on chemicals. Like a good cook, the industrial chemist recycles waste. Yet many types of waste are dangerous, leaving no option but costly disposal. With the global population rising and standards of living increasing, current methods of chemical production are unsustainable. As production rises to meet demand, waste levels will soar and landfill sites will be exhausted. Manufacturers will be increasingly restricted by environmental legislation; enforcement agencies will become increasingly overloaded; and costs of waste treatment will stifle innovation. A new approach is needed to remould attitudes constructively, and to attract young people to the field of chemistry. Step forward ‘green chemistry’, which aims to create products that are as harmless as possible and therefore require less regulation. The concept is enshrined in a set of 12 principles, ranging from minimizing waste to avoiding accidents. Individually, these principles are not new; what is potentially revolutionary is grouping them together so that chemists can focus on using classical chemistry to design products with less environmental impact. For example, non-toxic carbon dioxide is now used to make lighter, stronger building materials and to replace chlorinated organic solvents in chemical reactions and dry-cleaning. Integrating energy, waste and toxicity issues when thinking about new processes and reactions has proved to be very effective. Although some industrial processes are efficient, others are extremely wasteful, requiring costly handling and disposal of chemicals. The more stages a chemical process involves, the more potential it has for creating waste. So green chemistry inspires a kind of chemical ‘golf match’, in which fewer steps represent a better environmental ‘score’ — and the best result is, of course, a hole in one. For example, a new process for producing the anti-inflammatory drug ibuprofen halves the number of steps, makes them all catalytic and more than doubles the atom efficiency of the process. Green chemistry not only leads to cleaner and more efficient processes, but can increase profitability by eliminating many of the traditional costs of treatment, disposal, liability and regulatory compliance. Green chemistry involves more than just tidying up existing processes — if it were that simple, process economics would already be driving manufacturers in that direction. Rather, it identifies a need to design new, safer molecules. Often, the toxicity and the usefulness of a compound arise from different parts of the molecule; for example, a couple of strategically placed methyl groups added to a dye molecule makes it much less toxic but leaves its dyeing properties intact. Similar minor structural modifications can increase the biodegradability of molecules and reduce their environmental impact. Linking structure and toxicity gives synthetic chemists a new perspective, allowing them to design new pesticides that are toxic only to target organisms, with a fraction of the usual dose, and which do not persist in the environment. Green chemistry has captured the imagination of many chemists. But some industrial chemists believe that their very successful efforts at cleaning up have been overlooked, and some academics fear that green chemistry is ‘soft’ science. Although understandable in historical contexts, neither view is correct. Green chemistry is a new partnership, bringing together the efforts of industrial and academic research and building rapidly on the past successes of both. New solvents, feedstocks, catalysts and processes, producing everything from new, biologically derived, renewable plastics to lead-free automotive paint, are being developed throughout the world. Many challenges remain. How can chemical production shift from unsustainable petroleum feedstocks to renewable biomass? Can some of the vast quantities of carbon dioxide vented into the atmosphere be converted into useful chemicals? Can the environmental impact of agrochemicals be reduced while increasing food production? Green chemistry will attract the new generation of chemists needed to solve these problems. Already, young people are beginning to see chemistry as a key to saving our environment rather than a tool for its destruction. Will green chemistry take over all of chemistry? Far from it — the revolution of one generation becomes the orthodoxy of the next. The 12 principles are so obvious that chemists of the future will wonder why it took so long to integrate them into the mainstream. After all, why make chemicals wastefully and expensively, when they can be produced cheaply and cleanly? ■ Martyn Poliakoff is a research professor and Paul Anastas is a special professor at the School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK.

Green Chemistry: A design framework for sustainability

In this review we will highlight some of the science that exemplifies the principles of Green Chemistry, in particular the efficient use of materials and energy, development of renewable resources, and design for reduced hazard. Examples are drawn from a diverse range of research fields including catalysis, alternative solvents, analytical chemistry, polymer science, and toxicology. While it is impossible for us to be comprehensive, as the worldwide proliferation of Green Chemistry research, industrial application, conferences, networks, and journals has led to a wealth of innovation, the review will attempt to illustrate how progress has been made toward solving the sustainability goals of the 21st century by engaging at the molecular level.

Science in support of the Deepwater Horizon response

This introduction to the Special Feature presents the context for science during the Deepwater Horizon oil spill response, summarizes how scientific knowledge was integrated across disciplines and statutory responsibilities, identifies areas where scientific information was accurate and where it was not, and considers lessons learned and recommendations for future research and response. Scientific information was integrated within and across federal and state agencies, with input from nongovernmental scientists, across a diverse portfolio of needs—stopping the flow of oil, estimating the amount of oil, capturing and recovering the oil, tracking and forecasting surface oil, protecting coastal and oceanic wildlife and habitat, managing fisheries, and protecting the safety of seafood. Disciplines involved included atmospheric, oceanographic, biogeochemical, ecological, health, biological, and chemical sciences, physics, geology, and mechanical and chemical engineering. Platforms ranged from satellites and planes to ships, buoys, gliders, and remotely operated vehicles to laboratories and computer simulations. The unprecedented response effort depended directly on intense and extensive scientific and engineering data, information, and advice. Many valuable lessons were learned that should be applied to future events.

Toward a Comprehensive Molecular Design Framework for Reduced Hazard

The history of chemistry has been one of understanding the properties and transformations of matter. Perhaps the most important aspect of this understanding is the properties that have an impact on human and environmental health and the transformations that take place in our bodies and in the biosphere. Only through a mastery of this understanding will chemistry be able to genuinely design molecules that perform their intended function (e.g., therapeutic or industrial) and are safer for humans and the environment. Knowledge about the nature of toxic effects comes from the field of toxicology. Once primarily a descriptive science, relying to a large extent on whole-animal toxicology studies, the field has developed an extensive understanding of many of the mechanisms by which chemicals can exert toxicity.1 Application of this knowledge has made it possible to develop correlations, equations, and models that relate chemical structure and properties to biological responses. This has led to an increasingly sophisticated in silico predictive aspect of toxicology2 and provides the basis for current work being pursued in the development of a comprehensive design strategy for safer chemicals. While there has been significant work in the field of chemistry in designing for various functions ranging from medicines to materials, there has been a lack of a comprehensive framework for designing molecules to have a reduced impact on human health and the environment. A framework for the design of safer chemicals was originally published by the noted medicinal chemist E. J. Ariens in 1980, titled appropriately Domestication of Chemistry by Design of Safer Chemicals3 and later revised in 1985.4 An ACS Symposium Series book published in 1996 on Designing Safer Chemicals5 puts forth a framework that draws on a variety of sources and contains chapters that illustrate how the framework can be applied. In light of the tremendous advances in toxicology and molecular science in the 25 and 14 years since these prior perspectives were written, this review seeks to incorporate the new knowledge and tools available to today’s chemist. In the final measure, the ultimate success of deeply studying a problem is not simply to admire the problem but rather to solve it. This review provides an overview of the excellent research that has been done in the evolution of the * To whom correspondence should be addressed. E-mail: Paul.Anastas@ yale.edu. † Yale University. ‡ Science Strategies LLC. Chem. Rev. 2010, 110, 5845–5882 5845

Green chemistry: the emergence of a transformative framework

Abstract Since the Twelve Principles of Green Chemistry were formulated in the 1990s, there have been tremendous successes in developing new products and processes to be more compatible with human health, the environment, and sustainability goals. This review gives a sampling of research successes from the last 20years, including advances in synthetic efficiency, application of alternative synthetic methods, use of less hazardous solvents and reagents, and development of renewable resources for chemical feedstocks. The future of green chemistry will depend on innovations that consolidate and integrate these achievements that have been made, using all Twelve Principles as a framework for intentional design. Designing for sustainability and reduced hazard should not be viewed as constraining, but rather as providing the freedom to explore and invent, bridging continents and scientific disciplines to create new solutions.