March on, Hydrogen! Mild but very efficient: new catalytic process extracts hydrogen from bioalcohols

Enlarge

(PhysOrg.com) -- Over 80% of the worlds energy demands continue to be met with fossil fuels. The environmental problems associated with this, such as global warming, are well-known. The efficient supply of energy based on renewable resources is becoming more pressing. Hydrogen technology, which involves the production of hydrogen from biomass for use in electricity production in fuel cells, is a very promising approach.

In the journal Angewandte Chemie, researchers led by Matthias Beller at the Leibniz Institute for Catalysis in Rostock (Germany) have now introduced a new catalyst that allows for the use of bioalcohols for the production of hydrogen. Their novel process proceeds efficiently under particularly mild conditions.

Ethanol and other alcohols do not willingly give up their hydrogen atoms; this type of reaction requires highly active catalysts. Previous catalytic processes require downright drastic reaction conditions: temperatures above 200 C and the presence of strong bases. The Rostock researchers thus aimed to develop a catalyst that would also work efficiently at significantly milder temperatures.

Martin Nielson, working on Beller’s team thanks to an Alexander von Humboldt scholarship, has now been successful. The new catalyst demonstrates previously unachievable high efficiency in the extraction of hydrogen from alcohols under mild reaction conditions. Says Beller, “This is the first catalytic system that is capable of obtaining hydrogen from readily available ethanol at temperatures under 100 C without the use of bases or other additives.”

After initial successful tests with a relatively easily converted model alcohol (isopropanol), the researchers turned their attention to ethanol, also known as the “alcohol” in alcoholic beverages. Ethanol has taken on increasing importance as a renewable resource but is significantly harder to convert. “Even with ethanol, this new catalyst system demonstrated an unusually good conversion rate under milder conditions (60–80 C),“ says Beller. “In comparison to previous catalyst systems, this one is nearly an order of magnitude higher.”

The active catalyst consists of a ruthenium complex that is formed in situ. The starting point is a central ruthenium atom that is surrounded by a special ligand that grasps it from three sides. The other ligands are a carbon monoxide molecule and two hydrogen atoms. Upon heating, a hydrogen molecule (H2) is released from the complex. When the remaining complex comes into contact with ethanol or isopropanol it grabs two replacement hydrogen atoms, allowing the cycle to begin again.

More information: Matthias Beller, Efficient Hydrogen Production from Alcohols under Mild Reaction Conditions, Angewandte Chemie International Edition 2011, 50, No. 41, 9593–9597, http://dx.doi.org/ … ie.201104722

Provided by Wiley (news : web)

Breaking chemistry's bad rap

Breaking Bad, cable channel AMC's popular series chronicling the dark transformation of Walter White from suburban chemistry high school teacher to crystal meth master chef and criminal mastermind, makes chemistry entertaining for the average person through shocking story developments, including White using his chemistry expertise (poison, noxious gas, and acid) to eliminate rival meth slingers.

But the show is not improving chemistry's tarnished public image says Matthew Hartings, assistant professor of chemistry at American University.

"Breaking Bad is an entertaining and truly fantastic show. And, it's amazing how much actual chemistry they weave into each episode. Unfortunately, though, the show plays into our preconceived notions that chemists are mad scientists and that chemicals are bad for you," Hartings said. "This reinforces some people's belief that chemicals are things to be avoided when, in fact, we eat, breathe, sleep, and work in a world of chemicals."

Hartings and Declan Fahy, an assistant professor of communication at AU, coauthored a recent article in the journal Nature Chemistry outlining why, of all the sciences, chemistry has perhaps the worst public image and how chemists can help turn that around through improved communication.

A timely message as 2011, the International Year of Chemistry, has chemists and the chemical industry ramping up their communication efforts to honor chemistry's history and showcase the countless ways chemistry has improved everyday life.

Chemophobia

Hartings and Fahy say chemistry's bad rap is a result of "chemophobia," a term coined by chemist and popular science writer Pierre Laszlo referring to the terms most people associate with chemistry: poisons, toxins, chemical warfare, alchemy, sorcery, pollution, and mad scientists.

"One of the reasons that Breaking Bad plays so well is because the public is familiar with the mad scientist/wacky chemist narrative," Hartings said. "What we're not familiar with is all of the other places that chemistry is present in our lives."

Chemophobia is why publishers and television/film production companies avoid using the word "chemistry" in the titles of creative works. They fear that potential consumers will shy away from their products—some recalling how difficult chemistry might have been in high school and others thinking, "Aren't chemicals bad for you?"

"When Deborah Blum wrote The Poisoner's Handbook, a 2010 book that describes the evolution of forensic science in 1920s America, she suggested the subtitle A True Story of Chemistry, Murder and Jazz Age New York," said Hartings. "But the book's subtitle ended up being Murder and the Birth of Forensic Medicine in Jazz Age New York because the publisher told Blum putting the word 'chemistry' on the book's cover would sink sales."

Five Steps to Improve Chemistry Communication

In their Nature Chemistry article, Hartings and Fahy outline five communication strategies to help chemists increase public engagement with chemistry and improve the field's public image.

• Practice research-driven communication. Focus groups, surveys, and interviews can help chemists identify various publics (their attitudes, values, and beliefs) and understand how they get information and form their opinions about chemistry.

• Understand the audience. Because chemistry is a broad field, it can be relevant to numerous topics (a few examples include pharmaceuticals, renewable energy, and cooking and nutrition) and have numerous audiences.

• Participate in the new communication landscape. More chemists should use social media, blogs, and online videos to communicate with their peers as well as nonchemists/nonscientists.

• Tie chemistry to society. Relate chemistry to social issues or broader themes that touch the lives of everyday people.

• Frame key messages to prompt engagement. Because chemistry is a broad, complex field and can appeal to numerous publics, chemists need to learn frame their messages to encourage public engagement (present a specific issue in a way that shows people the issue's relevancy and application to their lives).

Provided by American University

Hydrogen released to fuel cell more quickly when stored in metal nanoparticles

Researchers from TU Delft and VU University Amsterdam in the Netherlands have demonstrated that the size of a metal alloy nanoparticle influences the speed with which hydrogen gas is released when stored in a metal hydride. The smaller the size of the nanoparticle, the greater the speed at which the hydrogen gas makes its way to the fuel cell. The researchers publish their findings in the October issue of the scientific journal Advanced Energy Materials.

On 27 September Dutch Minister of Infrastructure and the Environment, Ms Schultz van Haegen, announced she will earmark 5 million Euros to stimulate hydrogen transport in the Netherlands. According to the Minister the Netherlands and neighbouring countries have all it takes to become a 'hydrogen heaven'. In July 2011, the German car manufacturer Daimler announced its intention to build twenty new hydrogen fuelling stations along Germany's motorways. Hydrogen is back on the agenda. Hydrogen gas is currently stored in a vehicle fuel tank at 700 bar pressure. Fuelling stations thus require high-pressure pumps to fill these tanks and these systems consume a lot of energy.

There are thus good reasons for finding alternative hydrogen storage techniques. Hydrogen can be absorbed in high densities in metals such as magnesium, without the need for high pressure. However, the disadvantage is that releasing the hydrogen again is a very difficult and very slow process. One way of speeding up the release of the hydrogen is to use magnesium nanoparticles that are fixed in a matrix to prevent them from aggregating.

Professor of Materials for Energy Conversion and Storage, Bernard Dam, and his colleagues at TU Delft and VU University Amsterdam have demonstrated experimentally that the interaction between the nanoparticles and the matrix can cause the hydrogen gas to be released faster. Using models consisting of thin layers of magnesium and titanium, they show how the pressure of the hydrogen being released from the magnesium increases as the layers become thinner. This means that it indeed makes sense to store hydrogen in nanoparticles in a matrix. The choice of matrix determines to what extent the hydrogen desorption pressure increases. The researchers published their findings in the October 2011 edition of the scientific journal Advanced Energy Materials.

Efficient and affordable hydrogen storage techniques can play an important role in the large-scale adoption of hydrogen fuel cells. Bernard Dam foresees the development of hybrid vehicles that use batteries for short distances but switch to hydrogen for long distances: 'Your electric motor will be powered by batteries inside the city, and by hydrogen when you go further afield.'

Provided by Delft University of Technology (news : web)

Making manufacturing ultrapure hydrogen gas easier than ever

Pure hydrogen (H2) is an important chemical widely used in the chemical industry, many semiconductor fabrication processes, as well as in Polymer Electrolyte Membrane (PEM) fuel cells. Almost all of the hydrogen (H2) gas generated today comes from the steam reforming of natural gas at oil refineries. However, this process also produces trace amounts of carbon monoxide (CO) byproduct, which limits the application of H2 and can ‘poison’ or destroy the delicate catalysts used in the manufacture of semiconductor and state-of-the-art fuel cells. Researchers led by Ziyi Zhong and Jizhong Luo from the A*STAR Institute of Chemical and Engineering Sciences in Singapore have now developed a material that purifies H2 gas by catalytically converting CO to carbon dioxide (CO2) while simultaneously removing excess CO2—an approach that enables CO removal down to the parts-per-million (ppm) level.

Although several methods exist for H2 purification, the preferential oxidation (PROX) reaction is often favored by fuel cell designers because it can be adapted for use in small, on-board reactors. In the PROX system, a mixture of H2, CO and oxygen gases passes over a metal catalyst located on a ceramic support. This sets off a complex series of oxidation reactions that consume CO, which generates various by-products including CO2.

Currently, gold nanoparticles are garnering attention as PROX catalysts because they are active below 100°C; lower temperatures enable more selective CO oxidation and are safer for vehicle applications. One problem with these catalysts, however, is their inability to lower CO concentrations below 100 ppm. Previous studies have suggested that the reason CO2 gradually deactivates these catalysts is because CO2 binds to the catalyst surface as carbonate.

Removing CO2 from the gas mixture with a solid-state sorbent material is one way to enhance PROX reactions and lower CO concentrations to the single ppm levels needed for H2 fuel cells. However, the challenge faced by Zhong and co-workers was that most common inorganic CO2 sorbents are incompatible with gold nanoparticles—their high working temperatures decrease the effectiveness of CO oxidation and destabilize the tiny metallic particles.

The team chose a novel porous material known as APTES/SBA-15 for their sorbent because it has a robust silica structure and contains amine groups that readily react with free CO2 at low temperatures. Further experiments revealed that APTES/SBA-15 sorbents boosted CO removal by an average 10% over unprotected gold PROX nanocatalysts.

Optimizing the layered arrangement of catalysts and sorbents in the reactor lowered the CO levels in H2 gas from 2000 ppm to 25 ppm. Zhong says that he expects even better performance in the future. “There is still plenty of room for development of better CO2 sorbents and catalysts for this process,” he notes.

More information: Ng, J. W., et al. Enhancing preferential oxidation of CO in H2 on Au/?-Fe2O3 catalyst via combination with APTES/SBA-15 CO2-sorbent. International Journal of Hydrogen Energy 35, 12724–12732 (2010).

Provided by Agency for Science, Technology and Research (A*STAR)

Biochemists identify new genetic code repair tool

Clemson University researchers recently reported finding a new class of DNA repair-makers.

Clemson biochemist Weiguo Cao studies how cells repair damaged DNA. The finding from Cao's lab in the Clemson Biosystems Research Complex in collaboration with computational chemist Brian Dominy appeared in the Sept. 9 issue of The Journal of Biological Chemistry: "A new family of deamination repair enzymes in the uracil DNA glycosylase superfamily by Hyun-Wook Lee, Brian N. Dominy and Weiguo Cao."

"DNA is a string of a long molecule composed of four building blocks: A for adenine, T for thymine, G for guanine and C for cytosine. The heredity of all organisms is determined by the pairing of A with T and G with C," said Cao, a professor in the genetics and biochemistry department.

DNA is constantly assaulted by various stresses. A common type of damage is modification of three out of the four building blocks for genetic code, A, G, C by a chemical process called deamination. The genetic consequence of deamination is that it will change the pairing of the genetic code. For example, the deamination of C (cytosine) will generate U (uracil). Instead of pairing with G as C will do, U pairs with A. In so doing, it changes the genetic program inside the cell and may cause dangerous mutations resulting in disease.

To ensure the integrity of the genetic material, cells are equipped with a "molecular toolkit" for repairing DNA damage. The toolkit is comprised of a variety of different molecules — called enzymes — that have evolved to repair different types of DNA damage. One of the DNA repair enzymes the Cao lab studies is called uracil DNA glycosylase (UDG). As it's name indicates, it is traditionally known as an enzyme that removes uracil from DNA. Because deamination of C (cytosine) is a very common type of damage found in DNA, UDG has been found in many organisms and researchers have grouped them into five families in the so-called UDG superfamily.

In their most recent work, Cao and his colleagues discovered a new class of enzymes in that superfamily that lack the ability to repair uracil. A further study showed that this class of enzymes, instead, is engaged in the repair of deamination on the different building block adenine. This caught them by surprise because all known UDG enzymes are capable of uracil repair.

To further understand how this new class of enzymes works as a tool for repair, Cao and Dominy combined computational and biochemical methods to pinpoint the critical part of the repair machine that is responsible.

"What we learned from this work is that DNA repair toolkits have an amazing ability to evolve different repair functions for different kinds of DNA damage," Cao said. "This work also demonstrates how a combination of research approaches from different disciplines makes the discovery possible."

"Collaborative efforts involving computational and experimental investigative methods can greatly enhance the efficiency of scientific discovery, as well as provide more thorough answers to very important scientific questions," Dominy said. "In my opinion, the collaborative efforts between our two groups have demonstrated the substantial value of such interactions."

Provided by Clemson University (news : web)