Carbon dioxide recycling? 'Diagonal' approach for reductive functionalization of carbon dioxide

“Carbon dioxide is a nontoxic, abundant C1 building block,” says Cantat. “Only a handful of processes using this starting material have been developed, because carbon dioxide is a very stable molecule that can not easily be made to react.” To date, there have been two different approaches for the use of carbon dioxide. According to Cantat, “In the ‘vertical’ approach, the carbon dioxide is reduced, which means that the oxidation state of the carbon atom is reduced by the formal replacement of oxygen with hydrogen. This results in molecules such as methanol or formic acid, which can be converted into fuels.” These products have a higher energy content than carbon dioxide, but only a handful of chemicals can be produced this way.

“In the ‘horizontal’ approach, the carbon atom is functionalized, which means that it forms new bonds to oxygen, nitrogen, or other carbon atoms”, continues Cantat. “The oxidation state stays the same, the energy content is not increased.” This does not produce fuels, but chemicals that are useful building blocks for chemical syntheses, such as urea.

The French team thus tried a compromise approach, a combination of both methods to make a “diagonal” approach. By their method, the carbon dioxide is both reduced and functionalized in one step. This allows the synthesis of a much greater number of chemicals, directly from CO2.

This reaction requires three things: a reducing agent (e.g. a silane), an organic molecule to be attached to the carbon atom of the carbon dioxide (e.g. an amine), and a special catalyst that catalyzes both the reduction and the functionalization. The successful catalyst is a special organic base consisting of a nitrogen-containing ring system. “Variation of the reaction partners should allow us to make a whole series of chemical compounds that are normally obtained from petrochemical feedstocks,” says Cantat, “for example, formamide derivatives, which are important intermediates for both chemical and pharmaceutical industries.”

More information: Thibault Cantat, A Diagonal Approach to Chemical Recycling of Carbon Dioxide: Organocatalytic Transformation for the Reductive Functionalization of CO2, Angewandte Chemie International Edition, http://dx.doi.org/ … ie.201105516

Provided by Wiley (news : web)

Recycling thermal cash register receipts contaminates paper products with BPA

Kurunthachalam Kannan and Chunyang Liao explain that manufacturers produce more than 8 billion pounds of BPA worldwide every year. Research links BPA with a variety of harmful health effects. BPA has been used in plastic water bottles, the lining of food cans and a variety of other products. But how much do non-food sources contribute to humans' daily BPA exposure? BPA coats the surfaces of thermal receipts, where it acts as a developer for the printing dye. To see whether this source of BPA was a concern, the researchers analyzed hundreds of samples of thermal cash register receipts and 14 other types of paper products from the U.S., Japan, Korea and Vietnam.

They found BPA on 94 percent of the receipts. The only receipts with that were BPA-free were those from Japan, which phased out this use of BPA in 2001. BPA was in most of the other types of paper products, with tickets, newspapers and flyers having the highest concentrations. But these levels still paled in comparison to BPA on receipts, which the study said are responsible for more than 98 percent of consumer exposure to BPA from paper. The researchers estimate that receipts contribute about 33.5 tons of BPA to the environment every year in the U.S. and Canada. They note that handling of paper products can contribute up to 2 percent of the total daily BPA exposures in the general population, and that fraction can be much higher in occupationally exposed individuals.

More information: Widespread Occurrence of Bisphenol A in Paper and Paper Products: Implications for Human Exposure, Environ. Sci. Technol., Article ASAP. DOI: 10.1021/es202507f

Abstract
Bisphenol A (BPA) is used in a variety of consumer products, including some paper products, particularly thermal receipt papers, for which it is used as a color developer. Nevertheless, little is known about the magnitude of BPA contamination or human exposure to BPA as a result of contact with paper and paper products. In this study, concentrations of BPA were determined in 15 types of paper products (n = 202), including thermal receipts, flyers, magazines, tickets, mailing envelopes, newspapers, food contact papers, food cartons, airplane boarding passes, luggage tags, printing papers, business cards, napkins, paper towels, and toilet paper, collected from several cities in the USA. Thermal receipt papers also were collected from Japan, Korea, and Vietnam. BPA was found in 94% of thermal receipt papers (n = 103) at concentrations ranging from below the limit of quantitation (LOQ, 1 ng/g) to 13.9 mg/g (geometric mean: 0.211 mg/g). The majority (81%) of other paper products (n = 99) contained BPA at concentrations ranging from below the LOQ to 14.4 µg/g (geometric mean: 0.016 µg/g). Whereas thermal receipt papers contained the highest concentrations of BPA (milligram-per-gram), some paper products, including napkins and toilet paper, made from recycled papers contained microgram-per-gram concentrations of BPA. Contamination during the paper recycling process is a source of BPA in paper products. Daily intake (DI) of BPA through dermal absorption was estimated based on the measured BPA concentrations and handling frequency of paper products. The daily intake of BPA (calculated from median concentrations) through dermal absorption from handling of papers was 17.5 and 1300 ng/day for the general population and occupationally exposed individuals, respectively; these values are minor compared with exposure through diet. Among paper products, thermal receipt papers contributed to the majority (>98%) of the exposures.

Provided by American Chemical Society (news : web)

No need for old tyres to be an environmental hazard thanks to new recycling technology

A new recycling process could be the answer to alleviating the environmental burden of old tyres.

Researchers with Deakin University’s Institute for Technology Research and Innovation worked with industry partner VR TEK Global to develop a new cost-effective and environmentally friendly solution for turning old tyres into high quality ingredients for the manufacture of new rubber products.

“What we have developed is a significant breakthrough in tyre recycling that is superior to the current practices of shredding and burying tyres in landfill, burning tyres or recycling them into low quality materials of limited use,” explained Deakin research engineer Chris Skourtis.

“Our process does not rely on chemicals and uses less power—making it more environmentally friendly. It also results in high quality ingredients that can replace virgin and synthetic rubbers in the manufacture of products such as new tyres, car parts, insulation materials, conveyor belts and ashphalt additive for roads.”

Each year more than 20 million tyres in Australia, and one billion world-wide, reach the end of their working lives. Only a small percentage of these tyres are recycled with most making their way into landfill; placing a burden on the environment and human health.

“There is a world-wide need to address the issue of disposing of end-of-life tyres in a responsible, environmentally friendly manner,” Mr Skourtis said.

“Tyres simply dumped or placed in landfill are known to leach harmful chemicals into the environment; cause fires; and provide a perfect breeding ground for pests like mosquitoes and rats.

“We have come up with a way of giving new life to old tyres that should eliminate the need for them to end up in landfill.”

The Deakin researchers, led by Professor Qipeng Guo, developed a small scale facility at the University’s Waurn Ponds Campus to test and refine the recycling technology developed and patented by VR TEK Global.

“We now have a technology that is far better than any other tyre recycling processes,” Mr Skourtis explained.

“First, the tyres are segmented in a way that allows for each part to be treated differently which eliminates impurities and results in a higher quality end product. For example, the steel reinforcement in the tyre is separated without fragmenting, which is not common in current tyre recycling.
“We have then created an efficient means of devulcanising and activating the tyres into rubber powders for recycling into rubber products.

“Devulcanisation essentially reverses the chemical process used to create the tyres. This is normally done using environmentally harmful chemicals. We have developed a mechanical method that requires no chemicals.

“We have also developed a way of using ozone gas to activate the rubber powder which makes it more compatible with other materials. This extends the usability of the powder for producing a wider range of rubber and plastic products than currently possible.”

Provided by Deakin University

Deep recycling in the Earth faster than thought

 The recycling of the Earth's crust in volcanoes happens much faster than scientists have previously assumed. Rock of the oceanic crust, which sinks deep into the earth due to the movement of tectonic plates, reemerges through volcanic eruptions after around 500 million years. Researchers from the Max Planck Institute for Chemistry in Mainz obtained this result using volcanic rock samples. Previously, geologists thought this process would take about two billion years.

Virtually all of the ocean islands are volcanoes. Several of them, such as Hawaii, originate from the lowest part of the mantle. This geological process is similar to the movement of coloured liquids in a lava lamp: hot rock rises in cylindrical columns, the so-called mantle plumes, from a depth of nearly 3,000 kilometers. Near the surface, it melts, because the pressure is reduced, and forms volcanoes. The plume originates from former ocean crust which early in the Earth's history sank to the bottom of the mantle. Previously, scientists had assumed that this recycling took about two billion years.

The chemical analysis of tiny glassy inclusions in olivine crystals from basaltic lava on Mauna Loa volcano in Hawaii has now surprised geologists: the entire recycling process requires at most half a billion years, four times faster than previously thought.

The microscopically small inclusions in the volcanic rock contain trace elements originally dissolved in seawater, and this allows the recycling process to be dated. Before the old ocean crust sinks into the mantle, it soaks up seawater, which leaves tell-tale trace elements in the rock. The age is revealed by the isotopic ratio of strontium which changes with time. Strontium is a chemical element, which occurs in trace amounts in sea water. The isotopes of chemical elements have the same number of protons but different numbers of neutrons. Mainz scientists developed a special laser mass spectrometry method which allowed the detection of isotopes of strontium in extremely small quantities.

To their surprise, the Max Planck researchers found residues of sea water with an unexpected strontium isotope ratio in the samples, which suggested an age of less than 500 million years for the inclusions. Therefore the rock material forming the Hawaiian basalts must be younger.

"Apparently strontium from sea water has reached deep in the Earth's mantle, and reemerged after only half a billion years, in Hawaiian volcano lavas," says Klaus Peter Jochum, co-author of the publication. "This discovery was a huge surprise for us."

Another surprise for the scientists was the tremendous variation of strontium isotope ratios found in the melt inclusions in olivine from the single lava sample. “This variation is much larger than the known range for all Hawaiian lavas”, says Alexander Sobolev. “This finding suggests that the mantle is far more chemically heterogeneous on a small spatial scale than we thought before.” This heterogeneity is preserved only by melt inclusions but is completely obliterated in the lavas because of their complete mixing.

Sobolev, Jochum and their colleagues expect to obtain similar results for other volcanoes and therefore be able to determine the recycling age the ocean crust more precisely.

Original publication:
Alexander V. Sobolev, Albrecht W. Hofmann, Klaus Peter Jochum, Dmitry V. Kuzmin & Brigitte Stoll; A young source for the Hawaiian plume; Nature, 10. August 2011

Recycling of Alzheimer's proteins could be key to new treatments

The formation of abnormal strands of protein called amyloid fibrils -- associated with two dozen diseases ranging from Alzheimer's to type-2 diabetes -- may not be permanent and irreversible as previously thought, scientists are reporting in the Journal of the American Chemical Society. Rather, protein molecules are constantly attaching and detaching from the fibrils, in a recycling process that could be manipulated to yield new treatments for Alzheimer's and other diseases.

In a study that focused on the fibrils associated with Alzheimer's disease (AD), Natalia Carulla and colleagues explain that scientists once believed that the fibrils themselves caused the memory loss and other symptoms of AD. During the last 10 years, however, suspicion has fallen on some toxic intermediate of the process through which those fibrils form in the brain. This study suggests that fibrils could be a source of those toxic intermediates.

The new study used laboratory techniques to detail molecular recycling within fibrils formed by two proteins, Aß40 and Aß42, which is most associated with AD. After monitoring recycling for 40 days, they found that both Aß40 and Aß42 molecules recycle within the fibril population, although to different extents. After 40 days, 80 percent of the molecules making up Aß40 fibrils underwent recycling while only 30 percent did so in Aß42 fibrils. These observations imply that Aß42 recycles more slowly.

"In the context of AD, demonstrating that recycling occurs in the fibrils is a step forward but it is also crucial to identify the recycling species involved; whether they are individual Aß units or small aggregates made of several units," explains Carulla. "It will be important to address if differences in the recycling species within Aß40 and Aß42 fibrils are relevant in the development of Alzheimer's disease. We are now working towards this aim. Once we have this information, we will be in a position to devise new therapeutic strategies that can modulate recycling."

More information: Aß40 and Aß42 Amyloid Fibrils Exhibit Distinct Molecular Recycling Properties, J. Am. Chem. Soc., 2011, 133 (17), pp 6505–6508. DOI: 10.1021/ja1117123

Abstract
A critical aspect to understanding the molecular basis of Alzheimer’s disease (AD) is the characterization of the kinetics of interconversion between the different species present during amyloid-ß protein (Aß) aggregation. By monitoring hydrogen/deuterium exchange in Aß fibrils using electrospray ionization mass spectrometry, we demonstrate that the Aß molecules comprising the fibril continuously dissociate and reassociate, resulting in molecular recycling within the fibril population. Investigations on Aß40 and Aß42 amyloid fibrils reveal that molecules making up Aß40 fibrils recycle to a much greater extent than those of Aß42. By examining factors that could influence molecular recycling and by running simulations, we show that the rate constant for dissociation of molecules from the fibril (koff) is much greater for Aß40 than that for Aß42. Importantly, the koff values obtained for Aß40 and Aß42 reveal that recycling occurs on biologically relevant time scales. These results have implications for understanding the role of Aß fibrils in neurotoxicity and for designing therapeutic strategies against AD.

Provided by American Chemical Society (news : web)

Scientists discover recycling method to advance fuel cell practicality

The use of hydrogen as a practical, widespread alternative fuel to gasoline took another step today as researchers from Los Alamos National Laboratory and The University of Alabama announce a method for recycling a hydrogen fuel source.

The scientists demonstrate that a lightweight material, ammonia borane, can be a feasible material for storing hydrogen on vehicles, according to an article publishing in the March 18 issue of Science. In the upcoming article, researchers describe an efficient method of adding hydrogen back into the material once the alternative fuel is spent.

“This is a critical step if we want to use hydrogen as a fuel for the transportation industry,” said Dr. David Dixon, the Robert Ramsay Chair of Chemistry at The University of Alabama and one of the article’s co-authors.

In this approach, ammonia borane in a fuel tank produces hydrogen which, when combined with oxygen in the vehicle’s fuel cell, releases energy. That energy is then converted to electricity that powers an electric motor. Water is the only emission.

After hydrogen is released from the ammonia borane, a residue, which the researchers refer to as “spent fuel,” remains.

“The spent fuel stays in the car, and we need to add hydrogen back to it in order to use it again,” Dixon says. “What this paper describes is an efficient way to add the hydrogen back to make the ammonia borane again. And it can be done in a single reactor.”

Practical, efficient and affordable storage of hydrogen has been one of the challenges in making the powering of electrical motors via hydrogen fuel cells a viable alternative to traditional gasoline powered engines. Benefits of hydrogen fuel cell technology include cleaner air and less dependence on foreign oil.

Today’s announcement of a successful “fuel regeneration process,” as the scientists call it, overcomes one key hurdle.

The experimental work was done at Los Alamos and the computer modeling work was done in Dixon’s University of Alabama lab. UA co-authors with Dixon are Edward “Ted” B. Garner III, a University graduate student from Florence; J. Pierce Robinson, a UA undergraduate from Atmore; and Dr. Monica Vasiliu, a UA alumna from Romania who is working with Dixon as a post-doctoral researcher.

The article’s lead author is Dr. Andrew D. Sutton of Los Alamos National Laboratory. Other Los Alamos co-authors are Drs. Anthony K. Burrell, John C. Gordon, Tessui Nakagawa and Kevin C. Ott.

While there has been much progress toward making the widespread use of hydrogen fuel cell technology practical, Dixon said other challenges remain.

“The basic three steps – the initial synthesis, the controlled release of hydrogen, and the regeneration of fuel – are actually in pretty good shape. The next piece is to get a cheap source of hydrogen that doesn’t come from coal or fossil fuels.

“The biggest hurdle which we, and everybody else in the world, are looking at is ‘how do I use solar energy efficiently to split water in order to make hydrogen and oxygen.’”

Provided by University of Alabama

Researcher revolutionizes rubber recycling

Scrap rubber has remained little more than, well, scrap -- until now. University of Akron researcher Dr. Avraam Isayev developed an innovative rubber recovery technology expected to cause a major shift in rubber reprocessing for industrial use.

Isayev, a distinguished professor of polymer engineering, and his student research team invented a unique rubber processing method using a novel technique, ultrasonic devulcanization. Isayev’s patented innovation allows for the recovery of rubber materials, which has been difficult, if not impossible, due to rubber’s vulcanized, or crosslinked, nature. Think scrap-tire heap. Isayev's technology enables devulcanization, or breaking, of the sulfur crosslink bonds in the rubber compound, permitting the once scrap material to be reprocessed and reused.

"Extensive experimental and theoretical studies were conducted based on this and otherrelated inventions,” says Isayev, noting that more than 50 articles and book chapters were published during the last 15 years to develop this technology. The National Science Foundation, NASA and a number of industrial companies funded the studies.

Isayev founded Avraam Corp. to develop an industrial ultrasonic extruder to carry out the process of recovering rubber from tires, roofing materials, shoe soles and other industrially significant products. World leading athletic shoe supplier Nike Inc. funded the research.

Isayev’s cutting-edge research is gaining attention. NorTech, a regional nonprofit technology-based economic development organization and catalyst for growing Northeast Ohio’s emerging technology industries, selected the development as a winner of its 2011 Advanced Materials Innovation Award Feb. 24.

Provided by University of Akron