Natural gas (methane) is an important energy resource, accounting for 29% of the total energy consumed in 2017. It’s used primarily as fuel to generate electricity and as feed stock for plastic materials.
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As a result of hydraulic fracturing of previously inaccessible shale deposits, the United States has moved from a moderate producer to the highest producer of natural gas, replacing Russia in 2009, and similarly in petroleum hydrocarbons, replacing Saudi Arabia in 2013.
Let’s take a closer look at the different types of natural gas, analytical challenges with measuring natural gas, and how a new analytical method provides an alternative approach to determining alkanolamine solutions.
What’s the difference between natural gas, wet natural gas and sour crude natural gas?
Natural gas, withdrawn from traditional petroleum wells, generally needs limited purification prior to selling it as a natural gas product.
In contrast, wet natural gas withdrawn from wells using hydraulic fracturing requires additional processing to remove the water, C2 to C5 hydrocarbons, and sometimes hydrogen sulfide (H2S) and carbon dioxide (CO2) before it can be sold.
Sour crude natural gas, defined as containing carbon dioxide (CO2) and hydrogen sulfide gases (H2S > 5.7 mg/m3), is very acidic, toxic and highly corrosive, requiring amine gas treatment with amine-rich scrubber solutions to neutralize the CO2 and remove the H2S gas impurities.
What’s the typical method for neutralizing impurities in sour gas?
Amine gas treatment (also named amine scrubbing or gas sweetening) typically uses percent concentrations of alkanolamines, such as ethanolamine (EA), diethanolamine (DEA), triethanolamine (TEA), and methyldiethanolamine (MDEA), to neutralize the sour gas impurities.
What are the challenges with this method?
When the neutralizing capacity is deemed inefficient, the amine solutions are regenerated and stripped of elemental sulfur. Dissolved salts (heat stable amine salts) remain, building up over time and resulting in higher maintenance costs and higher incidents of corrosion.
Determinations of both the amine concentrations and the heat stable amine salts are needed to ensure a pure product and an efficient amine gas treatment process. These determinations can be challenging in the concentrated alkanolamine solutions.
What is the ideal analytical technology to use for amine gas treatment?
For the determination of ionic components, ion chromatography (IC) with suppressed conductivity detection is the analytical method of choice as previously demonstrated for anionic heat stable amine salts, cations and alkanolamines, and with coupling to mass spectrometry. The determinations of the alkanolamines and degradation products are challenging because of the variability in the composition of the neutralizing amine, degradation products, and salts; and therefore, different stationary phase selectivity is often needed.
Is there an improved separation technology for neutralizing amines samples?
Yes. In a recent application note from Thermo Fisher Scientific, concentrated alkanolamine samples were separated and neutralized using the Thermo Scientific Dionex IonPac CS20 cation-exchange column. The Dionex IonPac CS20 column is optimized for hydrophilic amines using three types of cation-exchange functional groups, resulting in unique selectivity. As the ions elute from the column, they are detected by suppressed conductivity within 35 minutes.
What are the advantages of the new method?
This method provides an alternative approach to the determination of alkanolamine solutions with the advantages of different selectivity that provides an elution window for the alkanolamines, and a small volume injection to minimize column overload by injections of 1,000-fold diluted alkanolamines.
Where can I learn more?
To learn more on the alternative method, download the application note.
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