Petroleomics A barrel load of compounds As the world’s petroleum supply dries up, Phillip Broadwith goes hunting for oil armed with a mass spectrometer, a chromatography column and state-of-the-art data-mining software THINKSTOCK

46 | Chemistry World | May 2010 www.chemistryworld.org Petroleum, or crude oil, is one by 0.0005Da – about the mass of an biggest FT-ICR spectrometer In short of the most complex naturally electron. has a 14.5 Tesla superconducting occurring chemical mixtures on Rodgers explains why FT-ICR  Oil companies are magnet, but they are expecting a the planet. Each drop can contain MS has the upper hand when it looking to oil shale and 21T machine to come online later hundreds of thousands of different comes to resolution: it’s down to tar sands, as supplies of this year. To put that in perspective, types of molecules, from simple the magnets. The magnet separates lightweight oils run low a fridge magnet has a field of hydrocarbons to highly structurally ions of different masses within the  Oil is a very complex about 0.1T and a 500MHz NMR diverse carboxylic acids, sulfur and spectrometer – charged particles mixture of molecules, spectrometer’s magnet comes in at nitrogen heterocycles and metal in electromagnetic fields start to and mass spectrometry is just under 12T. ‘What we’ve found salts. whirl around, and the frequency of used to reveal these and is that you can never have enough Some of these compounds this spinning depends on both the assess the suitability of resolution,’ says Rodgers. ‘As you go – like the hydrocarbons – are mass of the ion and the strength of new oil supplies higher and higher you can see more relatively chemically benign, but the magnetic field. Heavy ions have  Environmental and more detail. We’re continually others can react or contribute to lower frequencies than lighter ones. concerns of oil processing surprised as we push the technique physicochemical behaviour of the Being able to tell the difference are also being looked at to higher and higher performance – oil causing headaches for chemists between one ion and another using mass spectrometry it just keeps giving and we get more and engineers trying to extract them depends on how confidently you and more information.’ from the ground or refine them into can measure its frequency, which But how does all this resolving the myriad fuel and petrochemical depends on how stable the field power help? It comes down to the products upon which the modern is. ‘Our magnetic fields only vary old saying – knowledge is power. world relies. And as we begin to by about 2 parts per billion per For the oil industry, knowing what run out of low-sulfur, lightweight hour,’ says Rodgers. ‘In other mass they’re dealing with means they oils and have to start considering spectrometers that use electric can maximise profits by getting heavier, dirtier sources such as oil fields, the integrity can be more like the most out of every molecule. shale and tar sands, knowing what parts per million, so they’re 1000 This applies right through the makes up ‘black gold’ becomes ever times less stable.’ whole process, from finding the oil, more valuable. Getting good resolution also extracting it from the ground, to But identifying all the takes time. To confidently measure it appearing in our lives as fuel or components of a sample of oil is no the mass of an ion, the team will plastic. easy task, and has given birth to the typically take a reading over several science of petroleomics. Like other million cycles of the ion around the Drilling for oil ‘-omic’ techniques, petroleomics magnet. Increasing the magnetic A significant part of the oil industry’s refers to the characterisation field strength increases the budget is spent working out where and quantification of all the frequency, meaning the ions cycle and how to extract oil. Drew possible constituents of a complex faster, and the mass can be obtained Pomerantz, a Cambridge, US-based system. Where genomics seeks faster. Increasing the field strength petroleomics expert for oilfield every possible protein-coding also increases the difference in service provider Schlumberger, gene hidden in a DNA sequence, frequencies of different ions, explains that the oil’s constituents petroleomics aims to fathom the further boosting resolving power. are crucial to those decisions; since chemical diversity of oil. And when This is why the Magnet lab team they dictate how easy it will be to it comes to unravelling molecular is constantly building bigger and Marshall was an early extract, and whether it’s financially complexity, mass spectrometry is better magnets. Currently their pioneer of petroleomics viable to do so. king.

Transforming resolution Alan Marshall and Ryan Rodgers at the US National High Magnetic Field Laboratory (better known as the Magnet lab) in Florida have been working on petroleomics techniques for years. In 1973, Marshall was part of the Canadian team that invented Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), which provides some of the highest mass resolution available LABORATORY to chemists today – crucial when there might be more than 100 compounds with the same nominal molecular weight in a sample. For example, C28H44NS, C32H28N and C30H36NO all have nominal masses of 426 Daltons and at low resolution they all appear as a single averaged signal in the mass spectrum. FT-ICR MS, however, can pick out individual compounds whose

accurate molecular weights differ FIELD MAGNETIC HIGH NATIONAL US / MARSALL ALAN www.chemistryworld.org Chemistry World | May 2010 | 47 Petroleomics

Multiple factors affect oil’s cause these phase changes. If two molecular composition during its oils with different compositions geological journey, including the mix together, that can also cause type of organisms from which it the waxes or asphaltenes to crash DREW POMERANTZ DREW originated, the rocks it encounters out of solution. ‘Not all crude oils and the depth – and hence the are miscible with other crude temperature and pressure – to oils,’ says Pomerantz, ‘for example which it is exposed. The most asphaltenes are only poorly soluble important factors are contact with in light hydrocarbons.’ Knowing bacteria and contact with water. the distribution of different types of ‘Bacteria will consume petroleum,’ oil within a reservoir helps prevent says Pomerantz, ‘and they change these issues. the composition in quite a Once the oil is extracted, repeatable and predictable way, identifying problematic so by looking at oil from different components allows refiners to parts of a reservoir that might have use simple, inexpensive chemical had different amounts of exposure reactions to remove or modify those to these microbes, we can assess molecules – a process known as how much the composition has ‘upgrading’. For example, nitrogen, been altered by them.’ Bacteria oxygen and sulfur can be excised tend to eat the lighter parts of the from compounds, raising the value oil, leaving behind the heavier tar of the oil. And knowing whether compounds, making the oil less the sulfur is present as sulfides and valuable and less likely to flow easily thiols or as aromatic thiophenes when pumped out of the ground. influences the chemistry needed to Contact with groundwater remove it. has the biggest impact on acidic Part of the aim of Rodgers’ compounds, since they are the most research is to make that whole water soluble, along with light process more efficient. ‘If you can aromatic molecules like benzene How the oil will flow once a well Oils collected from completely characterise the oil and toluene. ‘The solubility of some is drilled, depends drastically on different places in the and understand its properties,’ he of these compounds in water might composition: petroleum usually same reservoir vary in says, ‘then the amount of waste only be a few parts per million,’ has some dissolved gases, waxes colour and composition generated from processing these Pomerantz says, ‘but if you flow and asphaltenes – the viscous black materials would go drastically tremendous amounts of water stuff that eventually ends up on down.’ through a reservoir over geological our roads. As the temperature and A particular problem in refining timescales, these components will be pressure drop, components that is corrosion caused by carboxylic selectively removed.’ So a thorough were liquids may become gases at acid compounds. Rodgers explains analysis of the oil composition can the surface, and dissolved waxes that acid-laden oils will typically be help companies like Schlumberger and asphaltenes can solidify. ‘If a mixed with less acidic ones to bring work out whether an oil deposit has solid deposit forms in a pipeline, the total amount of acids down been subjected to this kind of water it can be cleaned out,’ says and reduce corrosion. ‘But that ‘washing’ or similar processes with Pomerantz, ‘but if it forms in the doesn’t always work,’ he adds, it’s natural gas flows, which deplete reservoir that’s really an issue.’ much more efficient to find out the different molecules from the It’s not just changes of distribution of size and type of acids mixture. temperature or pressure that can present. From that it is possible to Data mining for molecules Instrument companies are now both in industry and academia, producing off-the-shelf FT-ICR to make sense of petroleomic

LABORATORY spectrometers with sufficiently mass spectra. It builds on the

strong magnets to resolve extensive libraries of data petroleum samples. While these and processing techniques machines are pretty expensive, developed at the Magnet lab and operating them requires to help researchers analyse, specialised skills to push the sort and visualise their data to instruments to the required level extract meaningful information. of performance, it has opened up Stranz describes how the field

US NATIONAL HIGH MAGNETIC FIELD MAGNETIC HIGH NATIONAL US the technique to more users. is beginning to shift away from a However, according to David highly specialised service-based Stranz from California, US-based model into more mainstream software company Sierra Data-mining software aids the interpretation of complex spectra analysis. ‘A lot of current or Analytics, the standard software former clients of the Magnet supplied with such instruments useful information about teamed up with the Magnet lab are now buying their own often can’t assign and interpret an oil sample’s origin or lab researchers to develop spectrometers and doing some spectra in sufficient detail to behaviour. Composer – a commercial of their analysis in house,’ translate the tide of data into Three years ago, Sierra package that allows researchers, he says.

48 | Chemistry World | May 2010 www.chemistryworld.org predict where the acids will end He explains that hydrogen a complete picture of the contents up throughout the processing, all deficiency can be used as an ‘It takes three of a drop of oil. ‘You only get the of which makes corrosion more indicator of the types of compounds barrels of water mass to charge ratio,’ says Wolfgang predictable and controllable. present in the water – high values Schrader from the Max Planck would indicate molecules with to process one Institute for Coal Research at Environmental concerns complex saturated ring structures or barrel of oil’ Mülheim, Germany. ‘You don’t know Petroleomics is not all about oil some degree of aromaticity, which anything else about the molecule companies, though. Mark Barrow links into their behaviour in the that you have ionised,’ meaning from the University of Warwick, UK, environment and potential toxicity. there is no way of distinguishing does work with the oil industry, but he Classifying the compounds by different isomers with the same also collaborates with Environment size and hydrogen deficiency gives molecular composition. Canada – a government organisation Barrow a molecular profile of the Schrader’s research combines charged with protecting and acids in a water sample. ‘First of all mass spectrometry with a variety enhancing Canada’s environmental we need to know what’s actually in of chromatographic and chemical resources. He explains that dwindling the tailings ponds water,’ he says, separation and derivatisation reserves and consequent high prices ‘and then we can look at whether the techniques to delve deeper into of high quality crude oils, together different compounds may be found oil’s structural complexity. Certain with the desire for countries to be less in the environment and how they functional groups can be identified reliant on imports, has made more are affected by natural processes’. selectively by their reactions to unconventional petroleum sources Knowing what make chemical derivatives, and such as the tar sands of northern Schrader’s group uses special – often Alberta more economically viable. home-made – chromatographic However, tar sands require columns to separate out certain extensive processing to separate components from the mixture. ‘For the oil from the sand, and example, we have a column that tracking where different contains palladium(ii), which components of the can selectively elute different oil eventually end sulfur species at different up is crucial for times,’ says Schrader. This understanding the allows them to separate environmental out the compounds that impact of the contain thiophene extraction ring systems, for process. ‘The example, and then industry uses feed them into the approximately mass spectrometer three barrels to correlate of water to the structural process a information with single barrel their masses. of oil,’ says This kind Barrow. of structural This water technique is stored in would come into large ‘tailings its own when ponds’, and developing better there are processes for concerns that upgrading oil, such components as desulfurisation, of the oil – says Schrader. particularly water Rather than simply soluble acids – might measuring the overall make their way into sulfur content before and the natural environment. after the reaction, a more ‘If they affect the local fish, selective analytical technique then they can get into the could determine what kind of human food chain as well, which compounds remained – ie which is definitely something that merits ones were not reacting well with investigation,’ Barrow adds. the catalyst. This would allow JACK FIELDS / SCIENCE PHOTO LIBRARY PHOTO SCIENCE / FIELDS JACK The high resolving power and researchers to focus their efforts mass accuracy of FT-ICR comes compounds Oil companies want on making the right kinds of new into its own again in the analysis are present could also be important to check the quality of oil catalyst systems. of the water used to process oil in developing methods for before they pump it out of But even these hybrid approaches sands. Barrow’s research focuses remediating any contamination. the ground are only scratching the surface. particularly on naphthenic acids, To truly conquer the molecular which are aliphatic carboxylic acids Delving deeper complexity of the ‘petroleome’ will of the general formula CnH2n+ZO2, FT-ICR MS is an extraordinarily take an even more coordinated where Z is a negative, even integer powerful tool, but mass effort encompassing multiple known as the hydrogen deficiency. spectrometry alone can never give techniques working in harmony.

www.chemistryworld.org Chemistry World | May 2010 | 49