In this interview, AZoCleantech talks to Salvador Alvarado of Thermo Fisher, about the use of Raman spectroscopy in advancing energy production, hydrogen conversion and sustainable aviation fuels.
Please can you tell us about your role and what you do?
My name is Sal Alvarado, and I am a product manager of vibrational spectroscopy at Thermo Fisher Scientific. I have a bachelor's in chemical engineering with a focus on material science and experience in the life sciences, chemical manufacturing, and construction materials industries.
I want to share the potential for leveraging Raman spectroscopy for advancements in energy production and specifically diving into some hydrogen liquefaction conversion and sustainable aviation fuel (SAF) applications.
What is Raman spectroscopy?
Raman spectroscopy measures light-matter interactions, or in other words, the scattering of photons due to bond vibrations in a molecule via a laser and detector. Monochromatic light is directed at a sample.
The laser interacts with the molecules of your sample. In most cases, the light will be elastically scattered or rarely scattered, and there will be no change in energy.
On rare occasions, this laser's energy changes and its wavelength shifts. This is called inelastic scattering or Raman scatter, and we are interested in measuring it with Raman spectroscopy.
The detector will typically have a filter in front of it that filters out the original wavelength and allows the inelastic or the Raman scattered light to pass through into the detector. Once it passes through the detector, we can plot the Raman shift. This is what generates what we call a fingerprint of the molecule.
That inelastic scattering or that Raman scatter is specific to the sample that you are shining the light on. It is interesting to see that every single sample will have its unique fingerprint Raman scatter ID.
Raman is both a qualitative and quantitative means of measurement. You can translate some of the fingerprint information from your original scans into quantitative information by collecting samples at varying concentrations.
You can get a sample at, say, 25%, 50%, 75%, and 100% concentration and take a reference Raman spectrum of each sample to start correlating what they look like. The different concentrations have different effects on the shape and size of the waves coming in the Raman shift.
We can then build a mathematical model that correlates and helps us understand other samples of varying concentrations. We are now ready to use this model in the process environment.
Why would someone use Raman for process monitoring?
Raman is a light-based technique. This means it is a non-destructive and non-invasive means of analysis. Because we are working with light, Raman is known to be very accurate and reproducible.
You can understand the information in real time and get rapid results. There is a unique fingerprint for specific samples, making it easy to identify different and specific molecules.
Raman is both a qualitative and quantitative means of measurement. If you can implement it directly in line with your process, you can reduce downtime by reducing your dependency and offline analytical methods.
Lastly, if you work with aqueous solutions, water has a negligible interference signal within Raman. This means you can get direct results from your protein or your analyte of interest.
Please can you describe the Thermo Scientific™ MarqMetrix™ All-In-One Process Raman Analyzer?
The Thermo Scientific MarqMetrix All-In-One Process Raman Analyzer is a relatively small unit about the size of a chemistry textbook.
Multiple probes can be used with the Process Analyzer. The first is a Thermo Scientific™ MarqMetrix™ BallProbe™, which is used by touching the tip to your sample. By having that contact point, you are able to collect a very accurate and reproducible Raman signal.
If you are unable to touch the probe to the sample, say you are working on a conveyor belt and you want to analyze something that is in movement, we also have proximal probes that work at a distance.
You can keep the probe a fixed distance away from your sample and collect the Raman spectrum of something in motion. The proximal probe can also identify Raman spectra through different materials like glass.
Lastly, we have flow cells that are optimized for flowing samples. Whether you have a slurry with a powder, a liquid, or a gas, these flow cells are optimized to measure the Raman signal of materials in motion.
Raman spectroscopy for real-time analysis & process monitoring control
Video Credit: Thermo Fisher Scientific – Handheld Elemental & Radiation Detection.
Why is hydrogen considered an expanding renewable energy resource?
The first thing to consider is its abundance. It is the most abundant element in the universe, giving it huge potential for use.
Second, it is considered a truly clean energy. The only byproducts of hydrogen are electricity, heat, and water, meaning that it has zero carbon emissions at the point of use.
Furthermore, it is very versatile. You can store it in different states and use it in different areas. Hydrogen is also known to be very efficient in comparison with traditional combustion technologies.
However, there are some challenges associated with using hydrogen. Some of the main challenges that the field is facing today are with storage and transportation.
What storage methods are available for hydrogen?
Hydrogen is a gas at room temperature, so the obvious way to store it is through compressed gas. You can compress it and put it inside a compressed or pressurized container like you would see in a chemical lab and store it like this. The downside is that you cannot collect as much hydrogen as you would typically like.
You can further increase the amount of hydrogen you store by cooling the overall system and packing more hydrogen into the compressed area, e.g., cold or cryo compression.
Lastly, you could also have a state of matter change and change hydrogen into a liquid. This is most desirable because it has the highest energy density. Overall, you will have a lower storage volume. It is also the easiest way of transporting hydrogen. However, turning hydrogen into a liquid can be a very difficult process.
How can we turn hydrogen into a liquid?
To understand how to convert hydrogen from a gas to a liquid, we must first understand its spin and temperature equilibria states. Hydrogen is a diatomic molecule, and these hydrogen atoms like to move around and spin. Depending on their spin orientation, you can categorize them into one of two categories: either the ortho-hydrogen spin state or its para-hydrogen spin state.
The para hydrogen spin state is at a lower energy level than the ortho hydrogen spin states. This is important because at room temperature, hydrogen exists in about 75% orthoform and 25% paraform. As you cool it and convert it into a liquid, hydrogen turns into mostly its paraform, being around 99% para and 1% ortho.
Turning hydrogen from its orthoform to its paraform is an exothermic reaction. It releases heat into its surrounding environment, so much heat that this is higher than its enthalpy of vaporization, meaning that the heat released from the transformation of ortho to para is enough heat to vaporize the liquid hydrogen back into a gas.
This causes boil-offs and can lead to over-pressurization of the vessel where this is occurring. The trick to storing hydrogen in its liquid form is to transition it from its ortho to para hydrogen before the liquefaction step.
The other neat and important piece of information to know about this is that the reverse conversion from the para form to the ortho form is an endothermic reaction, meaning that as it turns from para to ortho, the system stays cooler for longer, and you can store the hydrogen for longer periods.
Can you give us an example of an application for the MarqMetrix All-In-One Process Raman Analyzer?
We recently collaborated with the Massachusetts Institute of Technology (MIT), which wanted to monitor the ortho-to-para conversion using Process Raman.
They started with hydrogen at room temperature, which existed in 75% ortho and 25% para. It was cooled with liquid nitrogen down to about 77 Kelvin. It was then passed through a packed bed in the presence of an iron oxide catalyst. Then, they tried to monitor and turn the hydrogen into around 50 % ortho and 50 % paraforms.
They were able to analyze and measure the efficacy of their packed bed and catalyst by using the MarqMetrix All-In-One Process Raman Analyzer together with a flow cell directly in line with their process.
We started with the raw spectrum, which included information about the ambient air and some of the probe materials. It was important that we subtracted that to get the spectra specifically from the hydrogen.
After this, we were able to build a mathematical model to analyze the conversion of ortho to para in real-time directly in line with their process. We were able to leverage the MarqMetrix flow cell directly in line with MIT's process. The flow cell they use is made out of pasteloid and designed for extremely robust conditions, varying temperatures, and pressure.
The flow cell incorporated the BallProbe technology directly within the flow path of the hydrogen, meaning we could get highly reproducible data right in line with their process.
Lastly, because the instrument is so sensitive, we were able to use a small volume specifically for this analysis. The MarqMetrix All-In-One Process Raman Analyzer was also chosen because it is factory-calibrated, and no additional calibration is required after its installation.
For process environments, this is extremely important. The system does not need to be recalibrated after a certain amount of time. It has an extremely small footprint and can be implemented in multiple industrial or heavily packed areas.
Why is sustainable aviation fuel (SAF) an emerging topic?
Global carbon dioxide emissions from aviation have quadrupled since the 1960s. Today, aviation fuel accounts for roughly 2% of all CO2 emissions globally. There are estimates that if we do not take any action to address this, in a couple of decades, we will reach up to 22% of global CO2 emissions from aviation fuel alone. We need to address this.
Traditional aviation fuel, or Jet A1, comes from a fossil-based feedstock. Sustainable aviation fuel comes from plants, fats, used oils, etc.
These processes are governed by different certificates, such as the International Sustainability and Carbon Certification, which certifies that no additional CO2 emissions are being made and that there is an actual CO2 emission reduction from the life cycle. There are no deforestation or water effects from the overall process, and there are no impacts on biodiversity. Making sure that you comply with certifications is important.
How are sustainable aviation fuels made?
Sustainable aviation fuels can be derived from plants such as sugar cane, corn, or beets. The first part of the process is to prepare the feedstock. To extract the fine sugars from these plants, mechanical grinding, different separation techniques, and even enzymatic hydrolysis are used.
We can then leverage the fermentation process by adding water and yeast and regulating the temperature, pH, and oxygen to convert it into ethanol and other volatile organic compounds.
We can then go into the distillation infiltration process, where these are further separated using heat, time, and different filters to gather your overall sustainable aviation fuel. It is important to note that today, sustainable aviation fuel is mixed with traditional aviation fuel before being used in commercial aircraft.
Where can Process Raman be utilized within this workflow?
Just about every part of this process can benefit from Process Raman.
You can look at the specific material identification of the sugars. You can leverage Process Raman to indicate when your fermentation process is complete or what stages it has gone through. You can also leverage it to characterize different materials in your distillation and filtration process. Before mixing it with traditional aviation fuel, you can use it as a final quality control check.
We have an active collaboration with a leading sustainable aviation fuel company based in the United States. This company was looking for inline glucose, ethanol, and isoprene quantification. They also wanted an understanding of the distribution of the carbon number, as well as an understanding of the physical jet fuel properties.
We accomplished this by leveraging the MarqMetrix All-In-One Process Raman Analyzer and a BallProbe directly inserted into a bioreactor for their fermentation process. We then monitored the indicative levels of glucose, ethanol, and isoprene within this experimental design.
We were also able to understand the distribution of the carbon number and identify and calculate physical jet fuel properties, such as the API, Flashpoint, and Freezepoint.
Process Raman can be used in multiple parts of the sustainable aviation fuel workstream. It can be used for compositional analysis, specification testing, custody transfer, and stability information.
Can you sum up the benefits of Process Raman?
Process Raman has successfully been deployed in hydrogen and sustainable aviation fuel applications through the ortho to para hydrogen liquefaction conversion and multiple different processes with sustainable aviation fuel, such as fermentation and physical property determination.
The sampling optics on the MarqMetrix All-In-One Process Raman Analyzer are optimized to integrate into varying processes with different conditions, such as the ones highlighted within hydrogen and sustainable aviation fuel.
Lastly, Raman has all the necessary attributes for integrating into other parts of the SAF and hydrogen workflows because it is specific, sensitive, stable, quick, and simple.
About Salvador Alvarado-Olivo
Salvador Alvarado-Olivo is a Global Product Manager with Thermo Fisher Scientific, Vibrational Spectroscopy. He has a BS in Chemical Engineering from Worcester Polytechnic Institute, with a concentration in material science. Salvador has experience in life sciences, chemical manufacturing, and construction materials industries.
He enjoys exploring new market opportunities with his colleagues and determining what is needed in terms of technology.
This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific – Process Analytical Technology.
For more information on this source, please visit Thermo Fisher Scientific – MarqMetrix All-In-One Process Raman Analyzer.
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