Ion Mobility Spectrometry Photo Ionization Detector Application Note Gas Chromatography Ammonia impurities in hydrocarbon streams Ammonia impurities in Ethylene or Propylene fluid streams

Ammonia (NH3) is a well-known, widely spread Ammonia is a serious contamination in Ethylene air pollutant, which is present almost everywhe- and Propylene because it acts as poison for the re in low ppm/ppb concentrations. Ammonia can catalysts in the Polyethylene (PE) and Polypro- be found in various processes, where gases are pylene (PP) production. In order to increase the the basic media, such as steam crackers produ- performance of the polymerization process for cing gaseous hydrocarbons for further producti- their production the sensitivity of the used on steps like polymerization. Gases like these are for example Ethylene, Propylene and even catalyst has to be increased. Therefore the so called cracker gas, which is mostly a mixture purity of Ethylene and Propylene is an important of above mentioned gases as well as Water and topic especially the contamination with Ammo- Hydrogen. The gases of interest are separated nia impurities. and afterwards fed into a pipeline which is serving other chemical plants, producing for Large quantities of Ethylene and Propylene are example Polyethylene. Ethylene and Propylene transported via pipe lines with lengths of several are widely used in industry chemistry and they hundreds of km. Companies producing Ethyle- are one of the most important compounds used. ne or Propylene will lead in their products at different point into the pipe line for the transpor- tation to the final users. The purity of Ethylene and Propylene especially the contamination

Compound other names Sum CAS-No. Structure with Ammonia at the point of lead in and extracti- formula on of the pipe line but also in the production Ammonia • Hydrogen nitride NH 7664-41-7 H process is important. There are growing con- • Trihydrogen nitride 3 N • Nitro-Sil H H cerns over the management of Ammonia impuri- ties. Ethylene • Ethene C2H4 74-85-1 H H C C H H With the IMS-Analyzer, IUT Medical offers a Propylene • Propene C3H6 115-07-1 H H • Methylethylene H C high sensitive, reliable, and easy to operate C C H H H analyzer. The IMS-Analyzer allows for the continuous, long-term direct measurement of low ppb of Ammonia in such streams (see IMS- Analyzer data sheet). Application Note

Ammonia impurities in Ethylene or Propylene fluid streams

NH3 in processes like these can be a problem in The IMS-Analyzer bases on the proven techno- terms of process efficiency, quality control and logy of ion mobility spectrometry (IMS) and also avoidance of damages, which cause the need to GC-IMS, which operates with atmospheric replace very expensive equipment such as pressure conditions, highly selective and sensi- catalysts. The fast, accurate and quantitative tive to Ammonia. Typical detection limits for measurement of NH3 in Hydrocarbon streams is Ammonia in such streams are less than 50 ppb a growing need in plastics manufacturing. An without prior enrichment. amount of NH3 which is higher than 5 ppm can poison catalysts and impairs the quality of the IMS is an atmospheric pressure, time of flight produced polymers in an unacceptable way. detection technique. The sensitivity, selectivity and speed of response make the technique Solution superior in many aspects to other monitoring methods. Unlike electrochemical devices, the The IMS-Analyzer is capable of detecting and IMS units are impervious to extreme temperatu- re or humidity conditions. In addition, in contrast quantifying NH3 directly from f.i. Ethylene or even in the process step of steam cracking to paper tape detection methods, the IMS units beforehand to avoid technical problems as well are designed for long term, continuous measu- as ensuring the quality and efficiency. The rements with little or no maintenance and few outstanding sensitivity and resolution as well as consumables. The electronics are completely the almost immediate response to concentration solid-state without moving parts or optics to changes make the IMS-Analyzer to one of the require alignment. most suitable process monitoring techniques available. Compared to other methods used in Advantages: that field like process gas chromatographs, IMS is relatively cheap. • Unique combination of GC column with IMS to a GC-IMS The following table provides information of the performance of IMS-Analyzer measuring • Real-time analysis of Ammonia Ammonia in hydrocarbon fluid streams: • High sensitivity in the lower ppb range without enrichment

Compound Standard MDC Resolution • Superior selectivity and cross sensitivity range rejection Ammonia 0 - 5 ppm < 50 ppb 0.1% • Automatic operation with of maximum Multi Point Sampler system (MPS) • As stationary and mobile devices available • Available in various protection classes (From general purpose to IP 55 and NEMA 4X) • Also in explosion-proof design available

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