Reliable Elemental Analysis for Nitrogen, Sulfur, and Chlorine in Biofuels

Mon 1 Nov, 2021

Reliable Elemental Analysis for Nitrogen, Sulfur, and Chlorine in Biofuels

First-generation biofuels are already widespread and well established. These are manufactured  using processes such as the fermentation of sugar and starch and the hydrocracking of vegetable oils and animal fats. Hydrocracking is a catalytic, hydrogen-based cracking process for producing hydrocarbons of higher molecular weight. Innovative technologies that can extract biofuels from cellulosic biomass and waste also exist. 

These biogenic materials contain high volumes of harmful hydrocarbons containing nitrogen, sulfur, and chlorine, which must be stringently monitored using analytical processes. This helps to not only ensure compliance with legal limits, but also to prevent negative impacts on the production process, product quality, and the environment. Correct elemental analysis requires the quantitative combustion of all sample components. This was once a time-consuming task for laboratories since an optimized method had to be specially developed for every matrix. Maintenance and repeat measurements were also often necessary due to the formation of soot and pyrolysis deposits in the analyzer. Even the slightest changes in the process, different matrix compositions, and varying sample volumes can affect the quality and accuracy of the results. 

Analytik Jena has therefore developed a flame sensor technology for elemental analysis that automatically optimizes the combustion process in line with the specific requirements of each matrix type, volume, and composition, and effectively prevents the formation of soot. The flame sensor technology thus accelerates analyses, ensures more precise results, and reduces the amount of maintenance necessary.

Finding the Right Elemental Analyzer for Biofuels

Many factors play a role when it comes to choosing the analyzer. Most importantly, users should ensure that the devices used are flexible, meaning they can easily be configured for different sample matrices. Oil and hydrocarbon samples in particular often feature complex matrices, which can have a negative effect on the results. The right analyzer should be able to compensate for this. But flexibility also means expandability, so that accessories such as autosamplers can be added to the device quickly and easily. Because space in the laboratory is usually limited, a multielement analyzer that can detect all the necessary elements should be chosen. Using a different device for each element requires not only a great deal of space but also extensive maintenance and more consumables. Cost-effectiveness, robust methodology, and easy usage are additional points that can be decisive: Today, an elemental analyzer must be able to operate on its own, 24/7. The analytical methods need to deliver fast, reproducible, and reliable results, even with different and difficult sample matrices. Lastly, people other than trained personnel should be able to operate the devices.

Developed for the analysis of biofuels and their precursors, the multi EA 5100 elemental analyzer can measure all relevant elements – nitrogen, sulfur, and chlorine. In addition, thanks to its special HiPerSens detection system, it can cover a wide linear operating range, from a few parts per billion (ppb) to several weight percent. In the horizontal operating mode, the multi EA 5100 features unique flame sensor technology, which enables direct sample analysis with flexible sample weights. This does not require pretreatment or previous knowledge of the sample’s characteristics. The flame sensor creates the ideal digestion conditions for each organic sample matrix and ensures optimal combustion of each sample. A single method for solids or liquids is sufficient for analysis of the entire spectrum of matrices, regardless of their viscosity, volatility, or combustibility. The analyzer’s performance will be demonstrated here, based on an example measurement of six samples.

Reliable Sulfur, Nitrogen, and Chlorine Detection with the Flame Sensor

Raw materials and intermediate and end products were analyzed to represent the sample matrices of the entire process chain of biofuel production. Samples one, two, and four are starting materials and process intermediates with high viscosity and high element contents. Samples three, five, and six are end products of biofuel production. They are slightly volatile, have low viscosity, and contain only traces of nitrogen, sulfur, and chlorine as undesired impurities.

Standard solutions based on 2,4,6-trichlorophenol (Cl), dibenzothiophene (S), and pyridine (N) in isooctane are used to calibrate the analyzer in the corresponding concentration ranges. A multi EA 5100 was used in horizontal operating mode, equipped with HiPerSens detectors, UVFD for sulfur detection, chemiluminescence detection (CLD) for nitrogen, and coulometry for chlorine. For automated sampling and the transfer of the samples and standards to the analyzer, the system was equipped with an automatic boat drive (ABD), including a flame sensor and a multi-matrix sampler. The flame sensor ensures optimized combustion of the different sample materials and adapts to the special requirements of each matrix component on its own.

Sample volumes of 100 μL were used to detect chlorine, and volumes of 40 μL were used to detect nitrogen and sulfur. The samples were digested by means of efficient, catalyst-free high-temperature combustion in a quartz tube, a fully automated process that takes place in the multi EA 5100.

The analysis process is divided into two phases: In the first process phase, the volatile sample components are vaporized in an inert gas stream, followed by combustion of the gaseous products formed in an atmosphere rich in oxygen. In the second phase, the heavy, nonvolatile sample components and resulting pyrolysis products undergo quantitative oxidization in pure oxygen. The flame sensor ensures consistent evaporation based specifically on the sample volume, which can be fully oxidized through the amount of oxygen available. The resulting combustion flame is also monitored in real time. Based on the registered flame values, the analyzer calculates the optimal digestion process for each matrix, including the optimal number of waiting points. This minimizes waiting times and increases the speed of analysis.

The dried, gaseous reaction products are transferred to the corresponding detection systems. The integrated Auto-Protection System with its particle and aerosol trap guarantees maximum operational safety. 

multi EA 5100 for Analysis of Sulfur, Nitrogen, and Chlorine in Biofuels

The multi EA 5100, with Analytik Jena’s proprietary flame sensor technology, enables time and matrix-optimized sample combustion. The elemental analyzer provides users with a fast and reliable analysis of demanding matrices such as pure biofuels and their precursors. This eliminates the effort needed to develop a specific method for each sample, which maximizes analysis efficiency and minimizes maintenance. The HiPerSens detection systems used for nitrogen, sulfur, and chlorine enable sample analysis in a wide range of concentrations without time-consuming sample preparation, thereby significantly reducing operating time

Customer Voice from Germany About the use of the multi EA 5100

“We save a lot of time thanks to the flame sensor."

“Each sample is fully combusted and residue-free. That is the best foundation for reliable measurement results. We also save a lot of time in method development since, thanks to the flame sensor, each sample can be oxidized quickly and easily in a variety of quantities without precise knowledge of its combustion characteristics.”

Peter Frenzel, Head of Analytics and Quality Manager at The Dow Chemical Company


TechNote Multi EA 5100 Flame Sensor (EN)

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Determination of Total Sulfur in Light Hydrocarbons, Spark Ignition Engine Fuel and Diesel Engine Fuel according to ASTM D5453 (EN)

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TN Determination in Bio-based Fuels According to ASTM D4629 (EN)

Application Note

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Oil & Gas

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