Tag Archives: greener process

Shake it up: A greener method for upset tummy medicine.

André, V, A Hardeman, I Halasz, RS Stein, GJ Jackson, DG Reid, MJ Duer, C Curfs, MT Duarte and T Friščić. 2011. Mechanosynthesis of the metallodrug bismuth subsalicylate from Bi2O3 and structure of bismuth salicylate without auxiliary organic ligands. Angewandte Chemie International Edition http://dx.doi.org/10.1002/anie.201103171.

Synopsis by: Audrey Moores and Wendy Hessler, Dec 15, 2011

This sounds like a kitchen recipe: mix A with B, add a few drops of water, a pinch of salt and then shake. Except, researchers followed these simple directions in a laboratory to make the main ingredient in the popular stomach and intestinal remedy sold under the brand name Pepto-Bismol.

To make the drug this new way, they mixed the two main dry ingredients then added the rest and vigorously shook the paste in a special shaker. The breakthrough – an important step forward in the emerging field of mechanochemistry – uses less energy and solvent than the current way the drug is produced. And it creates no harmful by-products.

This discovery is showing that using simpler chemistry methods can improve processes as complex as drug synthesis and also aids understanding of how drugs work.

 

Context

The image of chemistry is intimately linked with the idea of mixing together liquids. But a new field of chemistry – namely mechanochemistry – proposes to make molecules by mixing solids without adding copious amounts of liquid solvents.

In mechanochemistry, the reagents are loaded into a small cylinder with two metal or ceramic balls. This cylinder is shaken very fast to allow proper mixing. The advantages of this technique are multiple. The products are collected pure, the reactions proceed faster than in solution, and less energy is required to perform the mixing compared to what is needed to heat large amount of solvents.

Variations of this method include addition of a few drops of solvent or a very small amount of salts. This permits the use of slower shaking, thus reducing energy use even more.

Pepto-Bismol is a popular stomach and intestinal relief medication. It is composed of a metal called bismuth and aspirine. To be active, bismuth and aspirine have to form chemical bonds together.

Currently, the drug is made by mixing water solutions of these two ingredients. After reacting, the excess water is removed, which costs energy, time and money. Previous efforts to find simpler, less wasteful, mechanical ways to manufacture the compounds have failed.

This bismuth-aspirin drug has been used for more than a century, yet chemists do not know exactly what its chemical structure looks like when the active ingredients combine. This has limited understanding of how the drug functions in the stomach.

 

What did they do?

A group of researchers from Cambridge, United Kingdom, wanted to improve the existing synthesis of a pharmaceutical group of compounds called bismuth salicylates. The most well-known variety is bismuth subsalicylate, the active ingredient in Pepto-Bismol, an over-the-counter medicine used to treat nausea, heartburn, diarrhea and other stomach and intestinal symptoms.

They were looking for a way to make the desired bismuth subsalicylate using a method that was more energy efficient, faster, yielded fewer harmful byproducts and used less solvent than the current way to make the drug.

Instead of first dissolving the two key ingredients – bismuth oxide and aspirine – in liquid solvents and then mixing the two fluids together, the researchers chose a simpler method. They mixed the dry powders in a mechanochemical mill.

It was not the first attempt to produce this drug in such a simple fashion, but past trials were met with little success. This time, the research group added a few drops of water and a pinch of salt. During ingredient shaking, the presence of the water and the salt enabled the formation of the drug in very high yields.

They tested different ratios of bismuth oxide and aspirine, different volumes of water and a variety of salts. After each attempt, they identified the products produced during the reaction.

 

What did they find?

The researchers first added a few drops of water to the bismuth oxide and aspirine powders. This helped the reaction and products did form, but none were the active ingredient bismuth subsalicylate they were looking for.

They redid the experiment adding a little bit of salt with the water to the powders. A series of different salts were tested. They discovered that potassium nitrate and ammonium nitrate were very efficient in promoting the reaction and afforded the desired drug in high yields.

The reason why the addition of water and salt is required is not completely understood, but the researchers believe that it helps the molecules organize and “find their place” in the final molecular architecture.

 

What does it mean?

By testing a new method of mixing ingredients, this group of chemists was able to produce a commercially important drug using less energy and solvent. They also are the first to identify the chemical structure of a compound similar to bismuth subsalicylate.

The discovery of this new synthetic method is important because it opens the way toward more energy efficient and less polluting drug fabrication. The chemists only had to mix two essential ingredients with tiny amounts of water and nitrate salts – less than 5 percent. Interestingly, these salts do not seem to mix with the final product, which allows for easy separation in the end. Also, this new process generates only water as a by-product. It is thus compatible with drug synthesis.

The secondary discovery of the compound’s chemical structure may seem surprising. Although it has been known for more than a century that the ingredient in Pepto-Bismol is active, the actual way it works is still unclear. In fact, no chemist had isolated and identified the three-dimension chemical structure of any bismuth salicylates. It is a little bit as if engineers were trying to understand the way an engine works without having the knowledge of the shape of its mechanical pieces.

In this study, the researchers were able to decipher the structure of a compound very close to the ingredient bismuth subsalicylate found in over-the-counter medicine. This is a vital step towards understanding the biological activity of this much-used drug. This discovery was possible because the method afforded an unusually pure product, another common advantage of mechanochemistry.

The use of mechanochemistry at a production scale has been demonstrated, for example, on the synthesis of an anti-inflammatory drug/carrier composite. This new discovery may thus lead to a more optimal production of Pepto-Bismol and other medicines. Read more science at Environmental Health News.

IMGP5615

Polymer Clay Jewelry Chemistry

This interview was inspired by my latest infatuation with my etsy shop. My inspiration for starting an ‘store’ on etsy was Inedible Jewelry. They are a polymer clay jewelry business in the lovely city of Charlottesville, making replicas of everyday foods with PVC. The ladies of Inedible Jewelry, Jessica and Susan Partain, are at our local farmer’s market every weekend selling their latest miniature creations.  Taking the opportunity to see their studio and learn more about the chemistry behind polymer clay, I set up an interview with Jessica Partain in her workshop (see picture to left).

I interrupted her in the middle of placing holiday orders, in her studio filled with doll-house sized desserts, drinks, fruits, vegetables, etc. The main material used to make these bit-sized creations is PVC.  I started the interview asking about the chemical concerns with PVC over the past decade. Jessica explained: “While the formulation of PVC itself has not changed, both of the polymer clays that I work with (97% Premo, 3% Sculpey, both manufactured by polyform products) were reformulated in 2008 to be phthalate-free and lead-free.” Phthalates, which are also endocrine disruptors, used to be a concern for the sculptors before the reform because baking the clay would release them, consequently allowing them to be  inhaled by the artist. Jessica also explained: The clay she uses is also ASTM certified, making the product safe. “They’ve run it past medical experts and biochemists looking specifically for potentially harmful interactions between the material and the artist.” This made me proud of my fellow medical experts and biochemists, doing good in the world.

Jessica and Susan have also always used a separate toaster in a well-ventilated room for their polymer baking, making creations such as the cupcake earrings to the right. They use a separate toaster to ensure that they would not combine their cooking with their polymer. One concern that still remains is when the clay is burnt, from baking for too long or from baking at too high a temperature – releasing toxic HCl gas.

As a loyal customer, I asked her: “What do you do with annoying customers like myself, who also ask all these difficult chemistry questions before a purchase.” She answered: “Well, you are one of two people asking me these questions in past 22 years; and the other person who asked did not have much basis for her questioning.” I felt like a major nerd at that moment – 8 years of intense science back ground can do that to you.

Although most customers do not ask about the chemistry behind polymer clay, many worry about the metals used in the jewelry. I then asked “Is this because they are worried about the toxic chemicals in metals?” That was strike two for Nerd Mana. The real reason is because many people are allergic to certain metals. To combat this problem, Inedible Jewelry uses 925 Sterling Silver for their necklaces.925 indicates the silver is 92.5% silver, and 7.5% copper. Jessica explained that the copper allows for 925 Sterling Silver to hold its shape because 100% silver is too malleable. All her metals are nickel free to avoid allergic reactions that lead to inflammation.

AGC loves the work of Inedible Jewelry and is impressed with their knowledge of chemistry and toxicology as it applies to their work. We all have a necklace with a polymer clay pendant. So far our collection includes: a peppermint, a gingerbread man, and a rainbow cake (mine!). The equally festive peach pies are pictures to the left where each miniature peach slice is crafted by hand.

 

Written by Mana Sassanpour

 

3838_web

Green Chemistry at Virginia Tech Part I

Being a recent graduate of the University of Virginia, it is a little hard for me to write this article on all the innovation and leadership that is happening at Virginia Tech in the field of Green Chemistry (note: the two schools are notorious rivals). However, this is one topic on which I must concede: Tech just does it better.

To begin my series of Green Chemistry interviews with faculty and staff at Virginia Polytechnic Institute and State University (also known as Virginia Tech, VTech, and Tech), I interviewed Dr. Timothy Long. Dr. Long’s dedication to greener chemistry can be seen in both his teaching and in his research. I had the privileged opportunity to discuss his background, career at Tech, and plans for the future.

After receiving his PhD in chemistry, Dr. Long spent nine years in the chemical industry, where his passion for greener processes developed. He described: “they (industry) were very aware of green chemistry, motivated by economics and affordability.” Once exposed to this mentality, Dr. Long got passionate and wanted to see how to apply this mentality to his research and teaching. When he came to VTech twelve years ago he wanted a more sustainable way of doing things. He described: “I want to weave the principles of green chemistry into my teachings and research.”

A major contribution from Dr. Long’s lab is the more sustainable production of PSA (pressure sensitive adhesive used in many forms of tape and sticky notes). Previously, these compounds used petroleum-derived precursors that had terminal ester bonds. Dr. Long’s polyesters have that same ester bond but in the middle of the polymer. This structural change allows the compound to be made without solvent, while also allowing biodegradability. Killing two green chemistry birds with one stone.

Virginia Tech offers a course in green chemistry taught alternatively by Dr. Long and Dr. Etzkorn. It is a 4000 level class for undergraduates which caters to mainly to chemistry, biology, and business majors. Each semester the course has 45 students. The course takes an interdisciplinary approach to green chemistry as it integrates the science and concepts with society. It seeks to understand how chemistry is perceived in the wider community. While there is no green chemistry minor at Tech, the engineering school has a green engineering minor. Dr. Long also wants to make the green chemistry course mandatory for chemistry graduates. Currently he is submitting a proposal for a nanoscience degree at the University that would incorporate fundamentals of toxicology, essential for our upcoming chemists.

Dr. Long described the passion of Tech’s students to be more sustainable, commenting on their successful Earth Week each year and the increasing amounts of activity on campus. Tech is also hosting the World Polymer Conference next year – which is geared to making a more sustainable, healthy, and safer world.

AGC wishes Dr. Long success in all these ventures and applauds his success thus far.

Interview by: Mana Sassanpour, AGC

Pie Chart

Analysis of Green Chemistry publications over the past four years.

This figure is taken from Green chemistry: state of the art through an analysis of the literature by V. Dichiarante, D. Ravelli and A. Albini. Green Chemistry Letter and Reviews Vol. 3, No. 2, June 2010, 105-113.

 

As the label indicates, the pie chart shows a distribution of green chemistry topics as analyzed by articles produced in the year 2008. The majority of the pie chart (about 50%) is attributed to catalysis – or starting a reaction, under more favorable conditions that require less resources, whether those resources are heat, energy, reagents etc. Specifically, metal catalysts were the most cited catalysts used in many different reactions, specifically in those involving enzymes. Acids are also seen in this category, and according to the article, are used mainly in condensation reactions. The next largest section of the pie (about 40%) is attributed to media, or where/in what the reaction takes place. Many reactions require some liquid for a reaction to take place. Many of these liquids, especially in organic chemistry, are volatile or toxic compounds. As a result, most of the research done with green chemistry and the media of reactions use either no solvent, which allows for most reduction of waste. Water has also gained a prominent role in green chemistry literature as it is our universal solvent and usually can be recycled in a reaction. Ionic liquids are the third major media hit; they are liquids that have charged compounds in the solution to help guide a reaction. Ionic liquids are usually not volatile and are stored more easily compared to their organic counterparts. Finally, the last 10% of the pie chart goes to ‘new methods,’ or novel ways to do old reactions. Using microwaves to start and maintain a reaction is the most prominent method, followed by some research advances in photochemistry and ultrasounds, using light or sound respectively in reactions.

Making plastic: Use plants, not petroleum.

Miao, X, R Malacea, C Fischmeister, C Bruneau and PH Dixneuf. 2011. Ruthenium–alkylidene catalysed cross-metathesis of fatty acid derivatives with acrylonitrile and methyl acrylate: a key step toward long-chain bifunctional and amino acid compounds.Green Chemistry http://dx.doi.org/10.1039/c1gc15569e.

Synopsis by Audrey Moores, Dec 02, 2011

 

Researchers greatly improved the use of plant oil – instead of petroleum – as a raw material to produce high-end plastics resins.

Plant oil can be used instead of traditional oil from fossil fuels to produce highly desired specialty plastics called polyamides.

A study in the journal Green Chemistry describes how researchers in France identified the material – a metal called ruthenium – that makes this type of chemical reaction possible. This discovery expands the scope of using plant oil derivatives to make industrially-important molecules, such as those needed as starting materials for producing polyamides. Polyamides are a family of polymers with many useful applications, ranging from fibres – such as nylon – to highly resistant metal coatings. Polymers are large molecules composed of repeating units of a smaller molecule.

The bulk of plastics are made from fossil fuels. As oil supplies dwindle, there is a need to find novel, renewable sources of raw materials that can be used to make everyday products, such as plastics, detergents and drugs. Oil from plants can serve that purpose, and researchers are actively looking to use them.

In the study, researchers from Rennes proposed an improved method to turn plant oil products into high-end polymers, such as resin coatings to protect metal from corrosion. They selected two streams of renewable materials to achieve this discovery. On one end, they selected fatty acids – basically fat molecules – from castor oil gathered from the castor plant seed. On the other, they chose acrylonitrile – a compound easily accessible from glycerol, a waste product of biodiesel production.

The fatty acids and acrylonitrile are combined with an additive containing a metal called ruthenium. The specific reaction fused the acid and the nitrile part of the acrylonitrile together and created the precursors to known and novel types of polyamides. The reaction was highly efficient – much material was made for the amount of energy put in.

This reaction is difficult to perform in the laboratory because acrylonitrile tends to destroy the ruthenium additive. To overcome this obstacle, the chemists screened a large number of additives and reaction conditions – temperature, pressure, time – to find the way that provided high yields.

Researchers also made diester molecules, which are necessary in formulation processes. Formulation is the mixing of ingredients to form stable gels, creams or pastes for the cosmetic or detergent industry. This reaction is a very efficient way to access such molecules from renewable feedstock.

An often discussed problem of using plant oil to make molecules for manufacturing products is the competition between plants for food and plants for chemicals. One way around this dilemma is to reuse frying oil or get it from spent coffee beans. Another idea is to use oil from plants not used for food, such as oil from the castor plant that was used in this study.

This study proved that it is possible to use renewable feedstock to make complex molecules like polyamides. Industrial applications remain to be demonstrated, but the resarchers did optimize their chemical process with this in mind. Read more science at Environmental Health News.

 

Iron unlocks path to hydrogen fuel

Synopsis by Audrey Moores, Nov 21, 2011

Boddien, A, D Mellmann, F Gärtner, R Jackstell, H Junge, PJ Dyson, G Laurenczy, R Ludwig and M Beller. 2011. Efficient dehydrogenation of formic acid using an iron catalyst. Science 333(6050):1733-1736.

Researchers look to nature and use iron – instead of precious metals – to transform formic acid into hydrogen for use as a clean source of energy.

For decades, means of producing hydrogen fuel efficiently and without using traditional fossil fuels have eluded chemists and engineers. Yet some organisms sequester the element to fuel their life processes. Their secret lies in iron-based enzymes.

To mimic a hydrogen-based energy source for people, researchers from Germany and Switzerland successfully proved that iron can be a very efficient agent to generate hydrogen from formic acid. The simple and powerful system may have wide commercial appeal if researchers can determine why the system shuts down after just two-thirds of a day. The group’s results are published in the journal Science.

Hydrogen is a clean source of energy, with water as the sole combustion waste. Yet it provides a great deal of energy considering its low weight. That explains why it is highly attractive as a future source of clean energy. Much research is currently devoted to designing engines that can run on this fuel.

However, hydrogen is currently produced using energy from fossil fuels, which is a major hurdle to its development as a fuel. It can also be generated by splitting water into oxygen and hydrogen. Again, this reaction requires energy from traditional means, such as fossil fuels, nuclear power or hydroelectric power.

Formic acid is a promising starter material to generate hydrogen, as it is readily available from biomass –  plant or animal material usually collected through agriculture or forestry. Formic acid could also be used to store hydrogen, as it breaks down into hydrogen and carbon dioxide and can be made from these same two molecules. Attempts to harness formic acid have so far fallen short because processing it requires high temperature or additives.

The big problem is how to easily, efficiently and cleanly break apart formic acid to liberate the needed hydrogen. The researchers – inspired by organisms that do this naturally – found that switching out the precious metal catalysts used now with a simple compound based on iron and phosphorus can transform formic acid into hydrogen and carbon dioxide. No other by-products are produced.

The researchers combined formic acid, the iron-based compound and propylene carbonate, a green and non-toxic solvent. They tested the reaction in a realistic set up where the reaction was constantly fed with formic acid.

The reaction worked very well at normal temperatures. It was not affected by the presence of common impurities – such as water and air – typically found in formic acid supplies.

Hydrogen production was remarkably stable over 16 hours. After this time, water accumulated and deactivated the system. This difficulty will have to be overcome before the process can be used commercially.

The discovery means that chemists are a step closer to turning formic acid into hydrogen and carbon dioxide. This reaction would ideally happen inside the engine of a car fed with formic acid to allow the generated hydrogen to burn and power the car. The process will generate carbon dioxide, but since formic acid comes from biomass, the whole cycle would be carbon neutral.

This system is preliminary and will need to be elaborated upon and streamlined to meet commercialization requirements. But the system is very simple and powerful and may lead to humans using hydrogen as other organisms already do. Read more science at Environmental Health News.

 

Oranges to Plastic

Green Chemistry: Oranges to epoxide to polymer to plastic?

Lately we have been reading the green chemistry headlines about turning orange into plastic. But what does this really mean? What is the chemistry behind it? How does my orange peel become plastic? Read more for answers:

 

Step 1: Why oranges? Orange rinds have a ringed compound called limonene that gives citrus fruits their smell.

 

Above is the structure of limonene, courtesy of toxipedia.

 

Step 2: The limonene can be turned into an epoxide with the addition of an oxygen atom.

 

Above is the structure of limonene oxide, with the epoxide structure shown in red. Image courtesy of Santa Cruz Biotechnology.

 

The compound from step 2 is not very unstable since the epoxide structure (as seen in red) has angular strain and potential strain from sterics (having many components of a structure taking up the same space and being too close to one another). The epoxide creates bond angles that are not ideal as they are too small. The small bond angles are unstable and reactive – doing whatever they can to remove that strain.

 

Step 3: This is where carbon dioxide comes in. With the help of a zinc complex as a catalyst, the CO2 reacts with the epoxide structure to relieve the strain, allowing the epoxide to react with other epoxides to produce a polymer structure. This polymer structure is called polylimonene carbonate.

 

Step 4: Now we have a polymer (a compound with repeating units) which can be used to make plastic products through research and design. Currently there are no products on the market using this technology, but we hope to see that change in the near future!

 

Reaction is described as seen in JACS.

 

Brewing bioethanol in a single pot.

Synopsis by Wim Thielemans, Nov 01, 2011

Nakashima, K, K Yamaguchi, N Taniguchi, S Arai, R Yamada, S Katahira, N Ishida, C Ogino and A Kondo. 2011. Direct bioethanol production from cellulose by the combination of cellulase-displaying yeast and ionic liquid pretreatment. Green Chemistry http://dx.doi.org/10.1039/c1gc15688h.

An innovative process promises to produce bioethanol from plants in one step instead of three, but finding an easy way to purify the needed plant cellulose hinders its usefulness.

ShareThis

A more efficient way to produce biofuels from plants is possible by pretreating the woody material with a liquid salt before fermentation, report researchers in Japan who perfected the process in the lab. Yet, coming up with the usable, purified cellulose remains a big hurdle to the industry.

This experimental method is unique because it pairs an enzyme-yeast unit with ionic liquids to convert the plants into the liquid fuel known as bioethanol. The successful trial yielded 90 percent ethanol and 82 percent of the ionic liquid was recovered.

The one-step, one-container procedure is outlined in the journal Green Chemistry.

Cellulose is the most abundant renewable material available. Plants, algae and some bacteria produce in excess of 100 billion metric tons per year. The non-food material is an agricultural waste material. The ability to turn the unwanted cellulose into liquid fuel would be an important step toward reducing dependence on crude oil without using food crops.

It takes three steps to convert cellulose into the liquid fuel bioethanol. Step one treats cellulose and turns its rigid and ordered structure into more chemically accessible pieces. In step two, enzymes further break down cellulose into glucose, a sugar. Then, in step three, microorganisms such as yeast ferment the glucose to ethanol.

The new process takes a different approach. The cellulose is broken down with ionic liquids (step 1) then converted into ethanol (steps 2 and 3) with a yeast-enzyme pairing – all in a single pot.

This is a remarkable step forward because the enzyme, yeast and ionic liquid are together but don’t interfere with one another.

Ionic liquids are salts – a designation for chemicals made up of both a positively and a negatively charged component – that are liquid at low temperatures, unlike common salts such as kitchen salt. Bulky positive and negative groups that make up the ionic salts hinder their packing into a solid crystal. Thus, they stay liquid to much lower temperatures – even room temperature. Some ionic liquids have been shown to be good solvents for cellulose, which is otherwise very difficult to dissolve.

In this study, the authors attached cellulase – an enzyme that breaks down cellulose – to the outside of the yeast. By itself, this yeast-cellulase combination is not very effective at tearing apart the rigid and inaccessible cellulose structure. But, a winning recipe was found by combining a small amount of specific ionic liquids with the cellulase-yeast. The ionic liquid disrupts cellulose enough so that ethanol can be produced directly and efficiently from the pieces of cellulose.

This work shows some real promise, but as the authors point out, most cellulose is not pure. To turn biomass directly into bioethanol, this new one-pot process will need to either extract cellulose efficiently or convert the other natural materials that coexist with cellulose in the plants. Read more science at Environmental Health News.

 

Power plant exhaust recycled in the lab.

Synopsis by Wim Thielemans, Oct 25, 2011

Stevens, JG, P Gomez, RA Bourne, TC Drage, MW George and M Poliakoff. 2011. Could the energy cost of using supercritical fluids be mitigated by using CO2 from carbon capture and storage (CCS)Green Chemistry http://dx.doi.org/10.1039/c1gc15503b.

The potential to reuse captured carbon dioxide from power plant exhaust/emissions as a mixer for other chemical reactions is shown in a unique study.

In the future, coal and natural gas fired power plants may be able to provide an abundant supply of liquid carbon dioxide (CO2) – a valuable agent used in chemical reactions in a growing number of industrial applications.

A preliminary study of this unique way to recycle and reuse carbon dioxide finds the main impurities in the power plant CO2 won’t prohibit its commercial use. The results are explained in the journal Green Chemistry.

Carbon dioxide is commonly known as the greenhouse gas formed by burning fossil fuels. Energy producers intend to capture and store the carbon dioxide they produce. To do this, they’ll convert the CO2 gas into its supercritical state – that is, changing the gas into a liquid by using extreme heat and pressure.

Converting carbon dioxide gas into a liquid is one way power plants can meet the anticipated tougher emissions standards in an effort to counteract climate change. As a liquid, carbon dioxide is also a safe solvent in other chemical production processes. It has already found applications in decaffeinating coffee and in dry cleaning.

A main advantage of supercritical carbon dioxide is that it helps produce a purer end product without toxic residue. In a typical chemical reaction with it, lowering the pressure at the end of the reaction turns the supercritical carbon dioxide fluid back into a gas. The chemical product produced during the reaction is immediately recovered. If all starting material is converted to the final product, no further purification of the end product is needed.

The supercritical state is reached by heating and compressing carbon dioxide to above its critical point of 88oF and 1071 pounds per square inch (psi). Supercritical fluids behave as liquids for dissolving chemicals but allow the chemicals to move around at high speeds as they would in gases.

Unfortunately, compressing carbon dioxide to above its critical point is energy-intensive. This makes it usually too costly for industrial-scale reactions.

However, coal and natural gas fired power plants provide a cheap source of compressed carbon dioxide. To reduce their carbon dioxide emissions, energy producers intend to capture and store the carbon dioxide they produce. Because large power plants easily produce more than half a ton of carbon dioxide per second, compressing it reduces the required space for storage. It is this compressed carbon dioxide that could be used as a solvent in industrial processes.

Researchers in the United Kingdom investigated the effect of impurities found in carbon dioxide from power plants on a chemical reaction. They tested the supercritical carbon dioxide in a reaction at a modern industrial production facility. The facility does not use supercritical carbon dioxide because the high compression costs proved uneconomical.

In this work, none of the major impurities – nitrogen, water and carbon monoxide – posed insurmountable problems at the concentration likely to be found in power plant exhaust. Water and carbon monoxide did reduce the activity of the catalyst metal used to speed up the reaction. Increasing the temperature restored the catalyst’s activity.

This work is very relevant to industry and is a very promising first step toward reusing captured carbon dioxide. But, as the authors pointed out, it is only preliminary, and only one reaction was studied. Also, many impurities found in power plant carbon dioxide in very small quantities were not investigated.

Read more science at Environmental Health News.

 

Shortcut converts common cellulose into useable parts.

Synopsis by Wim Thielemans, Sep 23, 2011

Long, J, B Guo, X Li, Y Jiang, F Wang, SC Tsang, L Wang and KMK Yu. 2011. One step catalytic conversion of cellulose to sustainable chemicals utilizing cooperative ionic liquid pairs. Green Chemistry http://dx.doi.org/10.1039/c1gc15597k.

A new one-step process blends a pair of specially selected solvents with cellulose, overcoming a big hurdle in the race to use the plant-based material as a reliable source of chemicals and fuels.

Pairing up a unique blend of specialized chemical solvents with plant cellulose has solved a looming problem for chemists grappling to find an efficient method to break apart naturally abundant cellulose.

The one-step process uses two ionic liquids to break cellulose down into its smaller chemical pieces and convert these pieces into useful chemicals. This is an important feat since cellulose is targeted as an alternative source for the chemicals and fuels currently derived from fossil fuels.

The results show for the first time that combinations of ionic liquids can be very useful in guiding more efficient chemical reactions that create less waste and more product. The findings are interesting because they show it is possible to combine several processing steps just by choosing the correct mixture of solvents.

Cellulose is a major part of plant cells and is the most abundant renewable material on Earth. Every year, plants, algae and some bacteria produce in excess of an estimated 100 billion metric tons. Cellulose is not a food and is a waste product of agriculture.

An enormous research effort is underway to understand how to use cellulose as a starting material for biofuel and chemical production in order to replace crude oil. In this process, cellulose – a long chain of identical chemical units – needs to be separated into the individual units.

The key challenge to convert cellulose into chemicals is its poor solubility – that is, it does not break up easily in liquids. Chemical reactions, though, require close contact between all the parts to work well. In 2002, researchers reported that some ionic liquids were very good at dissolving cellulose.

Ionic liquids are salts – a designation for chemicals made up of both a positively and a negatively charged component– that are liquid at low temperatures, unlike common salts such as table salt. Bulky positive and negative groups that make up the ionic salts hinder their packing into a solid crystal. Thus, they stay liquid to much lower temperatures – even room temperature.

In this work, Chinese researchers used a mixture of two ionic liquids. The first was chosen to dissolve cellulose. The second was chosen because it increases cellulose breakdown into its individual units, and further, into useful chemicals.

Under the right conditions, all the cellulose was broken down. The reaction products were also removed from the ionic liquid mixture by simply adding an insoluble solvent such as methanol or hexane. While there were a variety of different reaction products, up to 48.5 percent of the cellulose could be converted to a single product: 2-(diethoxymethyl)furan. This chemical, in turn, can be easily converted into a variety of other products useful for the chemical and pharmaceutical industries.

The choice of the solvent to extract the reaction products from the ionic liquid also allows researchers to select the reaction products that are recovered.

The ionic liquid mixtures were also reused. No real difference in performance and composition was noticed over 10 repeated reactions.

The researchers chose to dissolve cellulose first followed by a reaction to convert cellulose into smaller, more useful products. However, the results suggest the system is versatile and – depending on which ionic liquids are selected – could be extended to several reactions in a row. Ionic liquids will certainly hold some surprises in the future.

Read more science at Environmental Health News.