GREEN CHEMISTRY
The 2016 Presidential Green Chemistry Challenge Awards Annual awards recognize chemical innovations that prevent pollution and promote sustainability STEPHEN K. RITTER, C&EN WASHINGTON
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ew people could argue that using vegetable oil instead of crude oil, replacing platinum catalysts with iron, or potentially avoiding the use of billions of liters of toxic and corrosive acids in petrochemical plants isn’t a good deal. These are the benefits of some of the innovations that have been recognized with this year’s Presidential Green Chemistry Challenge Awards. The award winners were unveiled on June 13 at a ceremony held in Portland, Ore., in conjunction with the 20th annual Green Chemistry & Engineering Conference. The Green Chemistry Awards are administered by the Environmental Protection Agency and supported by the American Chemical Society and its Green Chemistry Institute, which select an independent panel to judge the nominations and determine the award winners.
▸ Zeolite catalyst offers a better future for gasoline
As its name suggests, the awards program challenges chemists, chemical engineers, and the chemical industry and academic community to do better and recognizes their successes in developing innovative technologies with demonstrable human health and environmental benefits.
industry researchers have spent decades looking for a better option. The leading candidates are solid catalysts such as zeolites, which are porous aluminosilicate materials with acidic reactive sites. Efforts so far have failed in most cases because of poor selectivity for the preferred alkane When it comes to oil refining and petroproducts or rapid catalyst deactivation, chemical production, the words “environJudzis explains. And there’s also no good mentally friendly” usually don’t come to way to regenerate the catalyst. mind. Yet industrial technology firm CB&I In developing AlkyClean, Albemarle reand specialty chemical company Albemarle searchers invented a platinum-containing have teamed up to make them part of the alumina zeolite with optimized pore vocabulary by inventing AlkyClean, sizes and acidic sites that selectively a cleaner and safer process for promakes high-octane trimethylpenducing alkylate, a key ingredient used + Olefin Trimethylpentane tanes over lower octane dimethylin formulating gasoline. For their efhexanes. As a bonus, the catalyst has forts, the companies shared the 2016 Hydrogen transfer Alkylation Greener Synthetic Pathways Award. a low susceptibility to fouling and Alkylate is an ideal gasoline feedproduces minimal by-products. CB&I + stock mainly made up of C8 branched engineers designed and built a conalkanes that are free from olefins and tinuous-flow alkylate reactor system Isobutane aromatics, low in sulfur, and high in optimized for using the catalyst. It octane rating. Manufacturers typical- Albemarle and CB&I teamed up to develop a solidallows continuous regeneration of ly make it by acid-catalyzed coupling acid zeolite catalyst to replace environmentally the catalyst by cycling from olefin adof an olefin with isobutane at a global problematic liquid hydrofluoric and sulfuric dition (alkylation) to hydrogen addirate of 115 billion L per year. acid catalysts used in the production of tion (regeneration) without changing But there are downsides to this trimethylpentane, the key component of the fuelreactor conditions. tried-and-true approach. Convenblending ingredient known as alkylate. “Our AlkyClean technology pro-
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tional alkylate production requires the use of billions of liters of hydrofluoric acid or sulfuric acid, according to CB&I’s Arvids Judzis Jr. These liquid acid catalysts are toxic and corrosive, Judzis says, presenting health and safety challenges for local communities and for refinery workers who handle them. And once used, the spent acids must be regenerated or sent for disposal, which takes additional energy and further generates waste and pollution. Refinery, catalyst, and petrochemical
These benefits include reducing toxicity of chemical products, reducing the use or generation of hazardous substances, introducing renewable feedstocks, saving water or energy, and reducing waste even if it’s not hazardous. Preventing pollution and promoting sustainability is not enough, however. The technologies are also judged on their ability to match or improve the performance of existing products and processes and be economically viable. “This year’s awardees clearly demonstrate that science and technology innovation can not only address complex global issues, but do so in a sustainable and safe manner,” said ACS President-elect Allison A. Campbell, who was on hand to help present the awards. This year’s winners include Albemarle, CB&I, Dow Agrosciences, Newlight Technologies, Verdezyne, and Princeton University’s Paul J. Chirik. The following vignettes tell their stories.
vides customers in the gasoline alkylation market a solution to produce higher octane alkylate with less environmental impact,” says Philip K. Asherman, CB&I’s president and chief executive. “We are really inspired by the potential of this technology to power a greener and more sustainable world,” adds Silvio Ghyoot, Albemarle’s president of refinery solutions. AlkyClean is the first solid-acid catalyst to reach commercial-scale production. The companies announced the successful startup of a plant making about 155 million L of alkylate per year in August 2015 at Zibo Haiyi Fine Chemical in China’s Shandong province.
CREDIT: COURTESY OF PAUL CHIRIK (CHIRIK GROUP)
▸ Earth-abundant metal catalysts turn the tide on silicones
O +
Si H
O
Fe, Co, Ni catalysts
O
O
Si O
O
Hydrosilylation O
N R N R
N
Ar
R
Fe N
N
O N
N
N Co
N
O
N
Ar
+ Ni(O2CR)2
O R Catalysts
Chirik’s group and its colleagues at Momentive have developed iron, cobalt, and nickel catalysts (shown) to replace platinum in classic hydrosilylation reactions.
a silicon hydride (RSi–H) is added across the double bond of an alkene (C=C), the Catalysis is at the heart of many chemical reaction is critical for making silicones that processes. To make it more cost-effective are ingredients in many chemical products, and sustainable, chemists have set out to re- from car tires and hair conditioner to releasplace precious-metal catalysts such as palla- able adhesive coatings on postage stamps dium, platinum, rhodium, and iridium with and kitchen utensils such as spatulas. more abundant iron, cobalt, and nickel. The new catalysts operate on the prinPaul J. Chirik of Princeton University has ciple of metal-ligand cooperativity, a conprovided a classic example of this trend by cept pioneered by Chirik’s group in which first-row transition metals that typically promote one-electron radical processes can be used in place of traditional second- and third-row transition metals that operate via two-electron redox processes. In collaboration with silicone manufacturer Momentive Performance Materials, Chirik’s group has shown that the iron, cobalt, and nickel catalysts are more stable and selective than platinum and work at room temperature with both terminal and internal alkenes instead of only terminal discovering a new class of Princeton’s Chirik has alkenes. The reaction mixtures hydrosilylation catalysts to led an effort to pioneer also don’t require distillation to make silicone compounds development of firstremove unwanted isomerized and polymers. These iron, row transition-metal side products, as is sometimes a cobalt, and nickel catalysts catalysts that outshine necessity with platinum. are less expensive, easier traditional preciousMomentive engineers have to use, and environmenmetal catalysts estimated that if the Chirik cattally friendlier than the in hydrosilylation alysts were used to replace the platinum catalysts they are reactions to make world’s platinum hydrosilylareplacing, Chirik says. And silicones. tion catalysts—which use some they often offer better per5.6 metric tons of platinum formance. For his team’s work, Chirik has each year, according to industry data—they won the 2016 Academic Award. would reduce energy use by 85 billion Btu Platinum-catalyzed alkene hydrosilylaper year, cut waste by 8.5 million kg per tion is one of chemistry’s understated reacyear, and reduce CO2 emissions by 21.7 miltions. Although it’s a simple process in which lion kg year.
“This recognition highlights the importance of collaboration between academia and industry to produce chemistry that spans the fundamental to the applied,” Chirik says. “Using earth-abundant elements in catalysis is often overlooked as a key component of sustainable chemistry. Hopefully our success will get more people thinking about how to use the elements on the periodic table more responsibly.”
▸ Making every nitrogen count on the farm Chemistry has always been an integral part of agriculture, never more so than today as farming is more dependent on fertilizers and pesticides than ever before. Agrochemicals are now designed to be more selective so they can be applied at lower rates, and they are also designed to be less toxic and less environmentally persistent. One example is Dow AgroSciences’ Instinct, a new technology that makes more efficient use of nitrogen when it’s applied to crops. By encapsulating the ammonium monooxygenase enzyme inhibitor nitrapyrin in polymer microcapsules and applying it to fields with fertilizer or manure, Instinct helps prevent soil microbes from converting fertilizer into a form that is more likely to leach into groundwater and into streams and lakes. According to Dow, Instinct also reduces nitrous oxide emissions from farming operations, a leading source of the greenhouse gas. For its efforts, Dow AgroSciences received the 2016
Greener Reaction Conditions Award. Nitrapyrin, or 2-chloro-6-(trichloromethyl)pyridine, has long been used in agriculture to inhibit nitrification, according to Roberta J. Ressler, a member of the Dow JUNE 20, 2016 | CEN.ACS.ORG | C&EN
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Cl N Cl Cl Cl Nitrapyrin
Instinct (microencapsulated nitrapyrin)
Oil phase
Shear
Cross-linker R
Aqueous phase
NH NH O
NCO
+ OCN
NCO
Oil-soluble polyisocyanate
H2N-R
Crosslinker
Watersoluble amine
R
H N
H N
H N
O
H N
R
O Insoluble polyurea shell
polymerase enzyme couples carbon emissions from landfills, compost digesters, or power plants with oxygen from the air to produce polyhydroxyalkanoate polymers, which the company calls AirCarbon. Although methods to produce this type of sustainable plastic were previously known, including some that have been commercialized, they have been limited by production costs or by polymer performance, explains Mark Herrema, Newlight’s cofounder and chief executive. For example, microbial enzymes used by other methods tend to shut down once polymer is produced, which means a large amount of biocatalyst is needed to meet production goals, making them cost-prohibitive. Newlight’s production process avoids that issue, enabling the company to offer a sustainable plastic with commodity-grade performance that can outcompete petroleum-based thermoplastics such as polyethylene and polypropylene, Herrema
By encapsulating nitrapyrin in a polyurea shell (shown here), Dow AgroSciences’ researchers developed an aqueous formulation of the enzyme inhibitor that helps prevent soil microbes from breaking down fertilizer in the soil. The technology delivers nitrogen efficiently to plants and reduces water pollution and greenhouse gas emissions.
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“The demand for higher crop-yield agricultural productivity continues to expand,” says Daniel R. Kittle, the company’s vice president of research and development, “and so too does the need for science-based solutions like Instinct that are focused on addressing urgent global challenges such as water quality and greenhouse gas emissions.”
▸ Biocatalytic process stitches greenhouse gases into commodity thermoplastics The sense of urgency that society now feels about tackling climate change has gotten many chemists and entrepreneurs busy trying to figure out what to do with easily captured industrial greenhouse gas emissions. The result is a growing number of clever approaches for converting one-carbon molecules such as carbon monoxide, methane, and carbon dioxide into commodity chemicals such as methanol, formate, and 2,3-butanediol, as well as incorporating them into polymers. Enter Newlight Technologies, winner of the 2016 Designing Greener Chemi-
cals Award and Climate Change Award. Newlight’s biocatalytic process creates thermoplastics from sequestered methane and carbon dioxide. A proprietary bacterial
A chair made with Newlight’s AirCarbon, a thermoplastic derived from recycled methane emissions. contends. Those plastics require multiple production steps using oil or natural gas feedstock and metal catalysts at high temperature and pressure, leading to high capital costs. AirCarbon, on the other hand, is made from carbon emissions in a single reactor under near-ambient conditions. “Our mission is to use greenhouse gases as a resource to replace oil-based plastics and reduce the amount of carbon in the air on a market-driven basis,” Herrema says. “This award is a testament to the extraordinary team at Newlight that has been dedicated to this cause for more than a decade.” Since commercialization in 2013, AirCarbon has been used by Dell and Hewlett-Packard for computer packaging, Virgin and Sprint for cell phone cases, contract manufacturer KI for furniture, and The Body Shop for personal care product containers.
CREDIT: DOW AGROSCIENCES (MICROGRAPH); NEWLIGHT TECHNOLOGIES (CHAIR)
team. Its use was initially spurred by findings that, of the nitrogen applied to fields as urea, ammonia, or manure that is lost, 70% of it is lost through nitrification. In this natural biological process, microbes in the soil oxidize ammonium (NH4+) to nitrite (NO2–), followed by oxidizing nitrite to nitrate (NO3–). In soil, which is loaded with negatively charged particles, ammonium cations tend to stay put in plant root zones. But the nitrate anions are mobile and can leach away or are further broken down by microbes. Nitrapyrin disables the soil microbes, leaving more nitrogen in the ammoniacal form. Dow has been selling nitrapyrin since 1974, Ressler notes, but until now it was only available in a formulation compatible with a “dry” fertilizer: the anhydrous ammonia form of nitrogen. In the new approach, the Dow researchers designed an aqueous nitrapyrin microcapsule suspension that can be used with dry or liquid fertilizers. The team’s formulation involves trapping nitrapyrin in a polyurea shell formed by the reaction between an oil-soluble polyisocyanate and a water-soluble amine. Besides improving on nitrapyrin technology, Instinct offers an alternative to coated slow-release fertilizers, which can be expensive. Dow estimates that Instinct’s nitrogen-retention abilities increased 2014 U.S. corn production by 50 million bushels while cutting U.S. nitrous oxide emissions in half, or by approximately 664,000 metric tons of carbon dioxide equivalents.
Petrochemical processes Propylene Crude oil
Refine
Polymerization
Recovery and purification
Polymerization
Recovery and purification
Polyethylene
Recovery and purification
Air Carbon
Polypropylene
Catalytic cracking
Naphtha, propane, n-butane, gas oil
( Ethylene
▸ Dependent on fossil-fuel supply ▸ Multiple capital equipment operations = high capital costs ▸ High pressures and temperatures add cost
(
)n )n
AirCarbon process ▸ Sequestered greenhouse gas carbon as feedstock ▸ Direct feedstock to polymer in a single tank = lower capital costs ▸ Biocatalyst instead of metallic catalyst = near-ambient pressures and temperatures = lower energy cost and carbon emissions
Recovered CH4/CO2
Polymerization
Newlight Technologies’ biocatalytic process offers a sustainable route to commoditygrade thermoplastics that can compete with petroleum-based polymers. Last year, Newlight signed a 20-year contract to supply chemical distributor Vinmar International with more than 8.5 million metric tons of AirCarbon and has licensing agreements with furniture maker Ikea and other firms to produce millions of tons more.
CREDIT: SHUTTERSTOCK (ALL)
▸ Yeast repurposes vegetable oil to make nylon
coatings, and adhesives and as a source of diesters for lubricants and fragrances. Manufacturers currently produce DDDA from fossil-based resources by the trimerization of butadiene followed by hydrogenation and then oxidation with nitric acid, which requires high temperature and pressure. Another DDDA route involves fermentation-based oxidation of dodecane distilled from kerosene. Verdezyne researchers started with a Candida yeast strain originally isolated from petroleum-contaminated soil that uses alkanes as its sole source of carbon, explains Thomas A. Beardslee, the company’s vice president of research and development. The team first sequenced the yeast’s genome. Armed with that information, the scientists made genetic modifications to alter the yeast’s biochemistry, from feeding on alkanes and oxidizing them to produce energy to feeding on lauric acid derived from palm kernel oil or coconut
O
(O
)n
A polyhydroxyalkanoate
oil. The optimized yeast uses a three-step enzyme-mediated fermentation process to oxidize lauric acid to DDDA at a rate of better than 140 g/L. According to Verdezyne’s analysis, its Biolon-brand DDDA has a lower carbon footprint than fossil-fuel-based DDDA. Biolon has higher purity and equivalent or better performance than fossil-fuel-based nylon. Its production occurs under ambient conditions rather than at high temperature and pressure, Beardslee notes, making it safer to produce and more energy-efficient. It also avoids using concentrated nitric acid and generating the greenhouse gas nitrous oxide as a by-product. Verdezyne has demonstrated the technology in a pilot facility and is now building a 9,000-metric-ton-per-year Biolon commercial facility in Malaysia. “Renewable chemicals must be a central part of any broad strategy for combating climate change, and yet far too often they are left out of the discussion entirely,” says Verdezyne’s president and chief executive, E. William Radany. “This award plays a key role in raising awareness of clean chemicals.” ◾
Increasingly, manufacturers are looking to derive their raw materials and feedstocks from renewable sources. Dicarboxylic acids sourced from sugar or vegetable oil are a class of compounds at the top of the list. But getting from a plant-derived sugar or oil to a diacid and then on to a commercial product still takes ingenuity. Verdezyne received the 2016 Small Business Award for engineering a genetically modified yeast and developing an aerobic-ferSoybeans Palm fruit oil mentation-based technology platform to produce adipic acid, sebacic acid, and dodecanedioic acid. These three versatile diacid intermediates and their analogs are the starting materials for an array of consumer goods. For example, dodecVegetable oil Consumer products Coconuts Fermentation anedioic acid, or DDDA, is primarily copolymerized with hexamethylenediamine to make nylon 6,12 O O O O HFD P450 ADH or FAO and nylon 12,12. These types enzyme enzymes enzyme OH O ( ) ( ) ( ) HO ( )5 OH HO HO HO 5 5 5 of nylon are widely used in O engineered plastics in autoLauric acid Dodecanedioic acid mobiles and as filaments for (DDDA) paintbrushes, toothbrushes, Verdezyne scientists adapted yeast to develop a three-step enzymatic process for converting lauric and fishing line. DDDA is acid derived from vegetable oil into diacids such as DDDA, which is used to make nylon and other also used as a cross-linker chemicals that go into manufacturing consumer products. for acrylic-based paints, JUNE 20, 2016 | CEN.ACS.ORG | C&EN
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