GPA STD 2177

Abstract

This method is intended for the analysis of demethanized liquid hydrocarbon streams containing nitrogen/air and carbon dioxide, and purity products such as an ethane/propane mix that fall within the compositional ranges listed in Table 1. This method is limited to mixtures containing less than 5 mol percent of heptanes and heavier fractions (20 mol percent of hexanes and heavier fractions). <br>The heptanes and heavier fraction if present in the sample is analyzed by either (1) use of a pre-cut column to elute heptanes and heavier first as a single peak or (2) reverse flow of carrier gas after n-hexane, and peak grouping of the heptanes plus fraction. For purity mixes without heptanes and heavier, no reverse of carrier flow is required. <br><em>Note&#160;1 This method can be used for a hexanes plus analysis by adjusting the timing of the backflush event to occur following the elution of n-pentane.</em> <br><em>Note 2 - CAUTION- In the case of unknown samples with a relatively large C₆⁺ or C₇⁺ fraction and where precise results are important, it is desirable to determine the molecular weight (or other pertinent physical properties) of these fractions. Since this method makes no provision for determining physical Properties, the physical properties needed must be determined by extended analysis or agreed to by the contracting parties. The extended analysis will be made according to GPA Publication 2186.</em> <br><em>Note 3 - At this writing, GPA is developing a method for the analysis of samples containing more than 5 mol percent of heptanes and heavier fractions (20 mol percent of hexanes and heavier fractions).</em>