Raman spectroscopy helps create petroleum products from renewable sources

Wood. Crops. Manure. Even most garbage. These are all biomass - plant or animal material. It’s cheap, abundant, renewable, and gets its energy from the sun.

Now, researchers are using Raman spectroscopy to find ways to convert biomass into value-added products. Things like plastics and fuel.

Why? To reduce the environmental impact and high energy requirements of producing plastics and fuel.

Researchers use catalysts, substances that aid chemical reactions, to produce bio-based chemicals and fuels in an economic and efficient manner. Catalysts promote chemical reactions. Catalysts can have high surface areas through pores to help accommodate all the different molecules from the biomass.

By the research-based design of catalytic materials, scientists can convert biomass into useful chemicals, according to Prof. George Tsilomelekis, Ph.D., a chemical engineer at Rutgers University.

 “It can be a solvent, a fuel, or just a fuel additive that can improve the quality of existing fuels,” he said. “It can also be a polymer precursor.”

We get most of these fuels and plastics from petroleum. This usually requires energy-intensive processes. Tsilomelekis and other researchers are trying to find ways to produce all the important compounds that we usually get through petroleum from environmentally friendly renewable materials.

Tsilomelekis is developing catalysts to upgrade ethane and propane - components of natural gas - to ethylene and propylene. The shale gas revolution in this century has made natural gas plentiful and relatively cheap to extract.

To design the correct catalysts, researchers need to know what’s happening inside these chemical reactors. That’s where Raman spectroscopy comes in.

Raman spectroscopy is a non-destructive chemical analysis technique based on the interaction of light with the chemical bonds within a material.

Raman spectroscopy lets the researcher see the fundamental steps during a catalytic reaction, showing the researcher how the reaction works. And with that knowledge, they can modify the catalytic materials to produce better value-added materials. Or design materials with better properties.

Raman acts as a sensor, so researchers can understand individual steps in these chemical processes. It can be as simple as measuring the concentration of a compound in solution, and as complex as understanding the interaction of molecules with surface sites inside pores in a very fast manner. 

Raman spectroscopy and alternatively infrared spectroscopy can yield information about the structural changes of the materials. Researchers measure product distribution with other analytical techniques, like gas chromatography or mass spectrometry.

When combined, scientists can build structure-reactivity relationships, defining how the material changes during a reaction. The goal is whether these changes correlate with better product distribution or better product yields.

Tsilomelekis uses a HORIBA LabRAM HR Evolution, a confocal Raman microscope that lets him observe catalytic reactions quickly by measuring vibrational spectra.

“I can even now get information on how to change the reaction conditions based on this fundamental understanding to avoid catalyst deactivation,” he said. Catalyst deactivation is a loss of catalyst activity and/or selectivity.