QNRF Newsletter Archive

New discoveries at the nano level could aid natural gas processing and more

Carbon gel samples at different zoom levels
According to an estimate published in the January 1, 2011, edition of Oil and Gas Journal, Qatar sits on top of 14 percent of the world’s natural gas. But natural gas is not simply extracted from the ground and pumped into engines and tanks. Among other processes, it must first be pretreated to remove contaminants. A research team based in Qatar is developing separation systems—based on carbon arrangements at the nanoscale—to effectively filter contaminants from natural gas and other mixed streams, as well as enhance other applications.

“It’s extremely important to optimize the pretreatment operations around natural gas—such as removal of ‘sour gas’ containing carbon dioxide—in the most efficient and economic way,” said Shaheen Al-Muhtaseb, Professor of Chemical Engineering at Qatar University and lead researcher on this activated carbon absorption and nanofiltration research funded by QNRF. “Qatar is becoming a leader in the petrochemical industry, while maintaining an awareness of the wellbeing of our environment”.

“For example, special emphasis is given to the industries that use pure methane, extracted from natural gas, as a raw material. So from one side, our research is important for producing methane in the purest possible manner, and from the other side, it is important to be able to purify liquid and gas effluents from contaminants so that they’re not released into the environment while recovering important and valuable parts of the mixtures. The adsorbents developed in this work can play a pivotal role in all aforementioned separation processes.”

The particular nano-material under study by Prof. Al-Muhtaseb and his co-collaborators is called “resorcinol-formaldehyde activated carbon xerogel.” The team published work to present some first-ever findings around the behavior of this material—it was before only shown to form spherical particles of carbon, but under different conditions, and when mixed according to different ‘recipes,’ it displayed a more dynamic range of behavior that could potentially be very useful in the filtration of particles in gas or liquid.

“The dimensions of nanomaterials—specifically, the space between the molecules—allows for the mimicking of nature's efficient ways of simply yet elegantly managing chemical and physical processes,” Prof. Al-Muhtaseb explained. “Nanoporous materials can be tailored as filters that select for specific molecules to allow for either their passage or attachment to the filter’s surfaces, which results in the separation of these molecules from the bulk of other components.”

The nanoscale is hard to imagine, since it’s so much smaller than things we can track with a microscope. In fact, it would take 100,000 single-walled carbon nanotubes to equal the diameter of a human hair, or a collection of a million nanoparticles to equal the size of an ant. Yet research in this field continues to press forward based on the understanding of chemicals as they interact at this level. The main factor to consider when synthesizing nanoporous gel carbons, Prof. Al-Muhtaseb said, is the ability of chemicals to react with each other—in different ways depending on how they are mixed—to form specific chemical chains and branches that crosslink at the nano level to create matrixes that can serve as sophisticated filtration mechanisms.

“Typically, these gels can be used for separation processes in one of three forms: wet, dry, or activated carbon gel form,” Prof. Al-Muhtaseb explained. In the case of wet gel form, it is relevant when components should be separated from a liquid solution. In this case, the gel can remain wet and has a better chance to stay in its stable configuration since it doesn’t have to go through a drying procedure. However, it can be challenging to transport and store wet gels.

“The dried gels can be used to treat either gas or liquid mixtures. There are several drying methods and if the method is not chosen carefully, it could result in shrinkage of the produced gel structures and narrowing of the pores [holes], especially the wider ones. If the gel must attach to components [beyond simply filtering them out] during filtration, as is the case in this current study, then a carbonization and activation procedure is applied to the dried gels.”

The activated carbon gels are characterized by relatively large surface areas and have pore sizes in the nanometer or even angstrom range, he said. Angstroms are ten times smaller than nanometers and correspond to the gas types in their molecular dimensions. For example, the average sizes of single carbon dioxide, nitrogen and methane molecules are about 3.4, 3.6 and 3.8 Angstroms, respectively.

In addition to serving as filtration media for the separation industries, Prof. Al-Muhtaseb said that carbonized gels may potentially be embedded into other nanostructures to assist in their functions.

“Our research has produced general findings that are breakthroughs in the synthesis of cross-linked gel materials. These could be applied to other materials as well,” he said. “Qatar is becoming a regional leader in producing advanced knowledge and enriching high-quality research. This work represents the cutting edge and will help position Qatar as a key player in the field of nanotechnology.”

This gel-based activated carbon research project is based entirely in Qatar and is being conducted by Prof. Al-Muhtaseb, who is the Lead Principal Investigator (LPI), and his postdoctoral research associate Dr. Ahmed Awadallah, also of Qatar University. It is one of several QNRF-funded projects he has headed in the field of advanced materials and their applications.

“We are thankful for the QNRF support we have received,” he said. “These funds are driving high-impact research and a culture in Qatar, based on state-of-the-art research facilities and transferring advanced knowledge throughout the world.”

NPRP 08-014-2-003
Synthesis and Tailoring of Resorcinol-Formaldehyde Gel-Based Activated Carbon Materials for the Storage or Selective Separation of Natural Gas Components

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