Environmentally friendly rockets

Many rockets, satellites, and spacecraft are driven by hydrazine, sometimes with an oxidizing agent like nitric acid or dinitrogen tetroxide. When filling tanks with these highly toxic substances, technicians must wear full protective clothing—and a failed launch can lead to significant environmental damage. Researchers are thus looking for alternatives that are more environmentally friendly and less toxic, but just as powerful—requirements that are hard to meet in a single material.

Stefan Schneider and his co-workers at the Air Force Laboratory (Edwards Air Force Base, USA) have now introduced a new approach in the journal Angewandte Chemie: special hydrogen-rich ionic liquids that self-ignite in the presence of hydrogen peroxide.

Despite the potential danger, hydrazine is used as a rocket fuel because it delivers high performance, can be stored for a relatively long time, and spontaneously ignites upon contact with an oxidizing agent or a suitable catalyst. The oxidizing agents used as rocket fuels are also dangerous. Dinitrogen tetroxide is less corrosive than nitric acid, but it is toxic and highly volatile. Hydrogen peroxide is a promising alternative because it is less corrosive and leads to much less toxic gas at room temperature. Its decomposition produces only water and oxygen.

As an alternative to hydrazine as a fuel component, Schneider and his co-workers propose an ionic liquid. Ionic liquids are compounds that consist of ions, namely positive and negatively charged particles, like a salt. However, they are not crystalline; they remain “molten” as a liquid at room temperature. Ionic liquids essentially do not vaporize, which prevents the formation of toxic vapors. It has previously not been possible to produce an ionic liquid that is flammable when partnered with hydrogen peroxide.

Schneider and his team have now overcome this barrier. The positively charged ion of their ionic liquid is a phosphorus atom bound to four hydrocarbon chains. At the core, however, lies the negatively charged ion made from one aluminum, four boron, and sixteen hydrogen atoms. The hydrogen-rich composition raises the power of the fuel component. “This aluminum borohydride ion can be viewed as a densified form of hydrogen stabilized by metal atoms. In fact, for a given tank size, liquids with this ion contain even more hydrogen than pure liquid hydrogen, without the difficult cooling requirements,” according to Schneider.

In order to test the ignitibility, the researchers applied drops of the novel ionic liquid onto various oxidizing agents. Upon contact with hydrogen peroxide, ignition was nearly instant; with fuming nitric acid it exploded. Says Schneider: “It is thus interesting as a potential component for greener high-performance fuels.”

More information: Stefan Schneider, Green Bipropellants: Hydrogen-Rich Ionic Liquids that Are Hypergolic with Hydrogen Peroxide, Angewandte Chemie International Edition, http://dx.doi.org/ … ie.201101752

Provided by Wiley (news : web)

Enzymes turn vegetable oils into fuel through a flexible two-step process

Biodiesel is a promising future fuel, particularly because it can be made from a wide variety of renewable sources such as crude vegetable oils and waste fats produced by commercial kitchens. Conventional chemical processes for producing biodiesel, however, require pure and refined feedstock oils, thus negating any potential advantages. To get around this problem, Md. Mahabubur Rahman Talukder and co-workers at the A*STAR Institute of Chemical and Engineering Sciences have developed a two-step biocatalytic process that works well on all sorts of oils -- whether they are refined or not.

Making biodiesel involves breaking down vegetable oils through a reaction with methanol. Although some researchers have tried to use enzymes to catalyze this reaction, their efforts have seen little success because enzymes are deactivated when exposed to droplets of methanol. Various strategies have been developed to overcome this problem -- such as the gradual addition of methanol over time -- but none have proven suitable for industrial production.

Talukder’s approach involves splitting the process of biodiesel production into two separate steps. The first step involves hydrolyzing the oil, for which the researchers use a lipase enzyme called Candida rugosa. Vegetable oils consist of branched molecules known as triglycerides, which have three separate arms. Hydrolysis involves splitting off the arms so that each triglyceride is converted into three molecules of fatty acid.

The second step involves reacting the fatty acids with methanol to produce biodiesel. This step requires Novozym 435, an enzyme that is normally deactivated by methanol droplets. However, because methanol is much more soluble in fatty acids than in the triglyceride, all methanol added at this stage is dissolved in the fatty acids. Thus, because no methanol droplets form, the enzyme remains active.

“Avoiding enzyme deactivation is not the only advantage of our technique. The reaction between methanol and fatty acid progresses faster than the methanolysis of triglycerides,” says Talukder. “However, the key advantage is the feedstock flexibility.” In conventional chemical biodiesel production, impurities reduce the yield. This new approach, however, can accept feedstocks with any percentage of free fatty acids and water.

Talukder aims to make the process cheaper so that it can compete with chemical biodiesel production. “The lipase cost is one of the biggest challenges for the commercialization of the two-step process,” he says. “A low-cost lipase preparation technique is under consideration to improve the economic value of the process.” If successful, the technology could greatly help the environment and reduce the cost of fuel.

More information: Talukder, Md. M. R., et al. Two-step lipase catalysis for production of biodiesel. Biochemical Engineering Journal 49, 207–212 (2010) http://dx.doi.org/ … .2009.12.015

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

New synchrotron technique could see hidden building blocks of life

Scientists from Finland and France have developed a new synchrotron X-ray technique that may revolutionize the chemical analysis of rare materials like meteoric rock samples or fossils. The results have been published on 29 May 2011 in Nature Materials as an advance online publication.

Life, as we know it, is based on the chemistry of carbon and oxygen. The three-dimensional distribution of their abundance and chemical bonds has been difficult to study up to now in samples where these elements were embedded deep inside other materials. Examples are tiny inclusions of possible water or other chemicals inside martian rock samples, fossils buried inside a lava rock, or minerals and chemical compounds within meteorites.

X-ray tomography, which is widely used in medicine and material science, is sensitive to the shape and texture of a given sample but cannot reveal chemical states at the macroscopic scale. For instance graphite and diamond both consist of pure carbon, but they differ in the chemical bond between the carbon atoms. This is why their properties are so radically different. Imaging the variations in atomic bonding has been surprisingly difficult, and techniques for imaging of chemical bonds are highly desirable in many fields like engineering and research in physics, chemistry, biology, and geology.

Now an international team of scientists from the University of Helsinki, Finland, and the European Synchrotron Radiation Facility (ESRF), Grenoble, France, has developed a novel technique that is suitable exactly for this purpose. The researchers use extremely bright X-rays from a synchrotron light source to form images of the chemical bond distribution of different carbon forms embedded deep in an opaque material; an achievement previously thought to be impossible without destroying the sample.

"Now I would love to try this on Martian or moon rocks. Our new technique can see not only which elements are present in any inclusions but also what kind of molecule or crystal they belong to. If the inclusion contains oxygen, we can tell whether the oxygen belongs to a water molecule. If it contains carbon, we can tell whether it is graphite, diamond-like, or some other carbon form. Just imagine finding tiny inclusions of water or diamond inside martian rock samples hidden deep inside the rock," says Simo Huotari from the University of Helsinki.

The newly developed method will give insights into the molecular level structure of many other interesting materials ranging, for example, from novel functional nanomaterials to fuel cells and new types of batteries.

The research was funded by the European Synchrotron Radiation Facility (ESRF), the Academy of Finland, and the University of Helsinki.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by European Synchrotron Radiation Facility.

Journal Reference:

Simo Huotari, Tuomas Pylkkänen, Roberto Verbeni, Giulio Monaco, Keijo Hämäläinen. Direct tomography with chemical-bond contrast. Nature Materials, 2011; DOI: 10.1038/NMAT3031

Better viewing through fluorescent nanotubes when peering into innards of a mouse

ScienceDaily (May 28, 2011) — Developing drugs to combat or cure human disease often involves a phase of testing with mice, so being able to peer clearly into a living mouse's innards has real value.

But with the fluorescent dyes currently used to image the interior of laboratory mice, the view becomes so murky several millimeters under the skin that researchers might have more success divining the future from the rodent's entrails than they do extracting usable data.

Now Stanford researchers have developed an improved imaging method using fluorescent carbon nanotubes that allows them to see centimeters deep into a mouse with far more clarity than conventional dyes provide. For a creature the size of a mouse, a few centimeters makes a great difference.

"We have already used similar carbon nanotubes to deliver drugs to treat cancer in laboratory testing in mice, but you would like to know where your delivery went, right?" said Hongjie Dai, a professor of chemistry. "With the fluorescent nanotubes, we can do drug delivery and imaging simultaneously -- in real time -- to evaluate the accuracy of a drug in hitting its target."

Researchers inject the single-walled carbon nanotubes into a mouse and can watch as the tubes are delivered to internal organs by the bloodstream.

The nanotubes fluoresce brightly in response to the light of a laser directed at the mouse, while a camera attuned to the nanotubes' near infrared wavelengths records the images.

By attaching the nanotubes to a medication, researchers can see how the drug is progressing through the mouse's body.

Dai is the one of the authors of a paper describing the research published online this month in Proceedings of the National Academy of Sciences.

The key to the nanotubes' usefulness is that they shine in a different portion of the near infrared spectrum than most dyes.

Biological tissues -- whether mouse or human -- naturally fluoresce at wavelengths below 900 nanometers, which is in the same range as the available biocompatible organic fluorescent dyes. That results in undesirable background fluorescence, which muddles the images when dyes are used. But the nanotubes used by Dai's group fluoresce at wavelengths between 1,000 and 1,400 nanometers. At those wavelengths there is barely any natural tissue fluorescence, so background "noise" is minimal.

The nanotubes usefulness is further boosted because tissue scatters less light in the longer wavelength region of the near-infrared, reducing image smearing as light moves or travels through the body, another advantage over fluorophores emitting below 900nm.

"The nanotubes fluoresce naturally, but they emit in a very oddball region," Dai said. "There are not many things -- living or inert -- that emit in this region, which is why it has not been explored very much for biological imaging."

By selecting single-walled carbon nanotubes (SWNTS) with different chiralities diameters and other properties, Dai and his team can fine-tune the wavelength at which the nanotubes fluoresce.

The nanotubes are imaged immediately upon injection into the bloodstream of mice.

Dai and graduate students Sarah Sherlock and Kevin Welsher, who are also coauthors of the PNAS paper, observed the fluorescent nanotubes passing through the lungs and kidneys within seconds after injection. The spleen and liver lit up a few seconds later.

The group also did some "post-production" work on digital video footage of the circulating nanotubes to further enhance the image quality using a process called "principal component analysis."

"In the raw imaging, the spleen, pancreas and kidney might appear as one generalized signal," Sherlock said. "But this process picks up the subtleties in signal variation and resolves what at first appears to be one signal into the distinct organs."

"You can really see things that are deep inside or blocked by other organs such as the pancreas," Dai said.

There are some other imaging methods that can produce deep tissue images, such as magnetic resonance imaging (MRI) and computer tomography (CT) scans. But fluorescence imaging is widely used in research and requires simpler machinery.

Dai said that the fluorescent nanotubes are not capable of reaching the depth of CT or MRI scans, but nanotubes are a step forward in broadening the potential uses of fluorescence as an imaging system beyond the surface and near-surface applications it has been restricted to up until now.

Since nanotube fluorescence was discovered about ten years ago, researchers have been trying to make the fluorescence brighter, Dai said. Still, he has been a little surprised at just how well they now work in animals.

"I did not imagine they could really be used in animals to get deep images like these," he said. "When you look at images like this, you get a sense that the body almost has some transparency to it."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Stanford University, via EurekAlert!, a service of AAAS.

Journal Reference:

K. Welsher, S. P. Sherlock, H. Dai. Deep-tissue anatomical imaging of mice using carbon nanotube fluorophores in the second near-infrared window. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1014501108

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Messer consolidates its position in Vietnam

On 25 May, industrial gases specialist Messer signed a 25-year supply contract with Hoa Phat Group. Messer Haiphong, the Vietnamese subsidiary of industrial gases specialist Messer, will thus guarantee the supply of gases to the second phase of Hoa Phat Steel Integrated Complex.

The new air separation unit will produce some 1300 tonnes of air gases such as argon, oxygen and nitrogen per day, increasing Messer Haiphong’s current production capacity by around 250 per cent. Messer is thereby consolidating its position in the industrial gases market in northern Vietnam and strengthening its relationship with Hoa Phat Group. The unit will be integrated in the existing steel complex of Hoa Phat Steel Joint Stock Co. Ltd. in Kinh Mon Town, Hai Duong Province. Messer is investing around 26 million US dollars in the production facility. The unit is due to go into operation in July 2012.

In 2007, Messer had already invested 20 million US dollars in the construction of an air separation unit to meet the gas requirements of Hoa Phat Steel Integrated Complex’s first phase. This unit, which was commissioned by Messer Haiphong in October 2010, is the largest of its kind to date in Vietnam.

Messer Binh Phuoc, another Vietnamese subsidiary of the German Messer Group, is also investing six million US dollars in the construction of a production facility for liquid carbon dioxide in the south of Vietnam. This facility is expected to be completed at the end of 2012 and will meet the demand for liquid carbon dioxide in the southern part of Vietnam.

In China and Vietnam, Messer achieved total sales of 246 million euros.

In Vietnam, Messer almost doubled its sales in 2010 compared with the previous year. A significant contribution to this came from the air separation unit in the north of the country, which was commissioned in October. It also ensures an independent product supply for Messer’s liquid market activities.

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