20
Analytical Instrumentation
Take Advantage of Better PIONA Analysis
Hans van den Heuvel and Paul van den Engel, Bruker Chemical & Applied Markets Division Goes, The Netherlands
Email:
hans.van.den.heuvel@
bruker.com
Changes in quality standards and environmental law over the last decade has meant that engine fuel producers now have to comply with much higher quality specifications and more stringent environmental regulations than ever before. As a result a balance is required between maintaining the fuel performance by adding RON/MON improving components like iso-octanes and (bio-based) oxygenates and reducing environmentally harmful components such as benzene and toluene. Optimisation of this process results in a concerted move toward instrumentation and methodology capable of characterising petroleum fractions, including intermediates and finished products, providing their molecular composition in specific detail.
It is traditional in refineries that gas chromatography (GC) is routinely used to characterise crude oil and its derivatives, each with hundreds or even thousands of compounds. It is essential to extract as much relevant information as possible about the concentrations of these compounds to properly characterise raw materials, intermediates and finished products. This article examines the PIONA methodology, which is the standard test method under the jurisdiction of ASTM International Committee on Petroleum Products and Lubricants.
Analysing Fuel Mixtures
The method of choice for specifying the composition of spark-ignition engine fuels and its precursors has predominantly been O-PIONA group type reporting (Oxygenates, Paraffin, Iso- paraffin, Olefins, Naphthenes and Aromatics) conducted using either single column or multi-dimensional gas chromatography. Due to the complex nature of high olefin samples and the additions of oxygenates, multi-dimensional gas chromatography is the most qualified technique as outlined in ASTM D6839 – 02 ‘Standard Test Method for Hydrocarbon Types, Oxygenated Compounds and Benzene in Spark-Ignition Engine Fuels by Gas Chromatography’[1].
The methodology, using an O-PIONA analyser or multi-dimensional GC system, allows the single sample injection of a complex mixture of hydrocarbons. These are separated by a combination of highly selective multiple GC columns in series, individual temperature controls provide a specific resolved chromatogram of the components.
The advantages of O-PIONA methods are that they:
• provide a detailed analysis of naphtha fractions and finished products by carbon number, % weight and % volume from C1 to C14 compounds (i.e. olefins, paraffin’s and aromatics and optionally oxygenates);
• provide sample properties including RON/MON value, C/H, TBP;
• use multiple high selective columns and traps to provide an optimal summation of components, especially the olefins within a single group type and a high resolution between the different group types per carbon number;
• provide individual data for specific components, including benzene, toluene, ethanol, MTBE and other oxygenates;
• provide an ASTM recognised method of providing hydrocarbon analysis on complex samples within a short timescale using a single instrument; and
• offer flexibility by including only those columns in the analysis to tailor make the separation per sample stream type, including FCC naphtha, reformate, alkylate and gasoline. This is achieved by selecting the right mode of operation; PIONA, PONA, PNA and oxygenated fuel additives (i.e. O-PIONA, O-PONA).
Fuel Analysis Case Study
The PIONA+ Analyser from Bruker is the perfect solution for characterising the complete hydrocarbon and oxygenates composition of a spark- ignition fuel sample. The five groups of hydrocarbon types (PIONA) and optionally oxygenated additives have different properties and occur in varying proportions in different products. The instrument performs a single injection, total eluting analysis using the universal flame ionisation detection (FID). The sample undergoes separation into its component groups (O-PIONA) according to carbon number, through the use of multiple columns and highly selective traps. The analyser itself is a GC system supplemented with a series of interlinked switching valves, columns, two oxygenated component traps, an olefin trap, two molecular sieve traps and a hydrogenation catalyst, operating at independent controlled temperatures. The system switches the valves at pre- determined times to direct the fractions of the sample by back flushing or forward flow to the appropriate columns and traps. Time based by-passing together with temperature control of a column allows trapping and reinjection of a group at a required time. As the analysis proceeds, the columns separate these sample portions sequentially into their component groups of different hydrocarbon that elute to the FID.
Figure 2a and 2b: The effect of breakthrough of normal paraffins
The universal detection properties of FID for hydrocarbons allows peak area conversion to weight and volume factions. Since a 100% elution occurs, normalisation done by the PIONA+ software results in a matrix report in weight and volume %. Additional sample properties are also calculated from this matrix report.
Figure 1: The PIONA+ Analyser is a multi-dimensional GC and trap system providing an accurate compositional analysis (% weight or % volume) of spark-ignition engine fuels and its pre-blending fractions
April / May 2012 •
www.petro-online.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
