Nuclear magnetic resonance spectroscopy (NMR) is a sophisticated analytical tool that can provide detailed information about the structure, dynamics, reaction state, and chemical environment of pure molecules. Additionally, it can also give a lot of information on complex mixtures. Furthermore, since NMR technology relies on the magnetic moment of the nuclear spin, rather than high-energy radiation, it performs the measurements in a high homogeneous superconducting magnet using radio-frequency.
Sonia Cabral de Menezes is a chemical engineer who graduated fromt the Federal University of Rio de Janeiro in Brazil. She has been working for over 40 years at the Research & Development Center of Petrobras, where the first new-generation NMR instrumentation in Brazil was installed. In a recent interview she discussed the value of NMR analysis in the petroleum industry.
Petrobras is a Brazilian oil and gas producer and NMR plays an important role company wide, from exploration to the final products. A range of NMR techniques — high resolution solid-state and liquid-state, and low field NMR — are employed to meet the needs of the various areas, including drilling, production, refining, materials (such as rubbers and catalysts), product quality and biofuels. Sonia explained “We are the only NMR lab for the company so, everyone that needs NMR comes to us to try to solve their problems…for example: Why a certain material is not working in the production line?”.
NMR is used a lot in the petroleum industry to evaluate complex oil mixtures and to monitor developing new processes to produce diesel, gasoline, jet fuel, and lubricants with higher quality. It is also used to compare physical- chemical properties of different oils mixtures and to define the specific characteristics of particular oils, such as viscosity, aromaticity, density. Knowledge of such properties informs decisions regarding the final use of the oil or the best refinery to locate it.
The assessment of production processes for optimal performance on the pilot plant, eg, effectiveness of a new catalyst or treatment protocol, is also facilitated by NMR data. For example, NMR is used to measure the levels and types of aromatic compounds present at different stages of refinement.
Over many years NMR has proved especially valuable in the asphaltene characterization of crude oil. Asphaltene is a group of compounds found in crude oil that can eventually cause some problems of precipitation during production or transportation. They are soluble in aromatic products such as benzene and toluene but are insoluble in lighter paraffins. High-resolution NMR has helped to characterize asphaltenes at the molecular level in order to get relevant information to predict their likelihood for precipitation. Low resolution NMR is can be also used to assess oils at different wells for asphaltene content. The amount of asphalthene versus its average composition can give important information about the quality of crude oils and also cautions one has to have during its production and/or transportation.
It is thus of extreme importance that evaluations are accurate and reliable. If data are not precise, prediction can be not so good and production may be stopped unnecessarily resulting on profit losts. NMR is able to consistently provide the precision needed.
Sonia explained “If an oil production line had some problems because a broken material broke for example, so we analyze those materials and we have to say precisely what they are and if they are meeting the specs originally predicted for the job they were designed for. In this case, NMR is very essential to characterize the molecules that are composing that material with the desired accuracy”.
Similarly, reliability of the NMR instrumentation is of fundamental importance. This is particularly true in areas such as South America that are situated a long way from the vendors of NMR equipment. Consequently, South American companies have to be sure that the instruments they purchase are very reliable, robust, not very expensive, and have technical support in the country.
NMR analyses are needed continually to ensure the quality of petroleum products, for monitoring processes and in the characterization of materials and additives and there is a limited time during which they can be performed. Failure of analytical instrumentation means the necessary data cannot be obtained and answers to operational problems cannot be given in time causing serious and costly consequences for production to the company involved.
Looking forward, Sonia hopes that there will be advances in NMR automation and the possibility of remote analysis. “Maybe I can follow, diverse experiments in NMR from my home… automation is very important to deal with the spectrum you have, then you can transform that into answers. This is very essential for the oil industry and for any industry I think”.