Comprehensive two-dimensional gas chromatography for the analysis of Fischer–Tropsch oil products

Production efficiency and safety assessment of the solid waste-derived liquid hydrocarbons

Global fossil resource utilisation remains a concern. Organic fuels and chemicals produced through catalytic synthesis out of biomass/waste feedstock can help reduce the share of fossil resource utilisation. In this study, a solid waste-derived producer gas from the cross/updraft sliding bed gasification process was applied in a fixed bed catalytic reactor with the goal of producing rich hydrocarbon chains. The specific producer gas with CO = 10%vol., H2 = 9%vol. and CH4 = 4%vol. was applied into the catalytic reactor along with catalysts Cat-Co or Cat-CoMnK at 15 bar pressure. Both catalysts were investigated in temperature regimes of 250, 280 and 310 °C, and the liquefaction number and hydrocarbon production were determined. The liquid products were qualitatively analysed afterwards, and the safety assessment, comprising the autoignition test, was performed. The obtained results defined an optimal operating temperature close to 280 °C a value for both catalysts. The individual hydrocarbon compounds were defined mostly by alkanes and alkenes of C10-C14 hydrocarbon groups in the case of both applied catalysts. The application of MnK-promoted catalyst resulted in the production of a significant amount of C6 hydrocarbon groups as well. The results point out a wide range of compounds utilisable in many different applications throughout the production sphere and suggest the possibility of autothermal air gasification of solid recovered fuel with the goal of producing gas for catalytic synthesis with reduced operation costs. From the safety point of view, the temperature of 227.7 °C was defined as the lowest value when autoignition occurs. This lowest temperature is relevant to the Cat-Co 280 °C synthesis scenario.

Mechanistic Study on the Possibility of Converting Dissociated Oxygen into Formic Acid on χ-Fe5C2(510) for Resource Recovery in Fischer-Tropsch Synthesis

During Fischer-Tropsch synthesis, O atoms are dissociated on the surface of Fe-based catalysts. However, most of the dissociated O would be removed as H2O or CO2, which results in a low atom economy. Hence, a comprehensive study of the O removal pathway as formic acid has been investigated using the combination of density functional theory (DFT) and kinetic Monte Carlo (kMC) to improve the economics of Fischer-Tropsch synthesis on Fe-based catalysts. The results show that the optimal pathway for the removal of dissociated O as formic acid is the OH pathway, of which the effective barrier energy (0.936 eV) is close to that of the CO activation pathway (0.730 eV), meaning that the removal of dissociated O as formic acid is possible. The main factor in an inability to form formic acid is the competition between the formic acid formation pathway and other oxygenated compound formation pathways (H2O, CO2, methanol-formaldehyde); the details are as follows: 1. If the CO is hydrogenated first, then the subsequent reaction would be impossible due to its high effective Gibbs barrier energy. 2. If CO reacts first with O to become CO2, it is difficult for it to be hydrogenated further to become HCOOH because of the low adsorption energy of CO2. 3. When the CO + OH pathway is considered, OH would react easily with H atoms to form H2O due to the hydrogen coverage effect. Finally, the removal of dissociated O to formic acid is proposed via improving the catalyst to increase the CO2 adsorption energy or CO coverage.

Inlet hydrogenation gas chromatography to predict mass % linear paraffin content

The light condensate fraction obtained from the low temperature Fischer-Tropsch (LT-FT) process is very complex and it is processed further by hydrotreating to produce hydrocarbon products that can be sold as final products. The mass% linear paraffins in some of the final paraffin products is listed as a required specification. Usually gas chromatography equipped with a flame ionisation detector (GC-FID) is used for the analysis of the condensate feeds to estimate the mass% linear paraffins that can be expected in the final products after commercial hydrogenation. This is an important parameter used in the blending of suitable condensate feeds. Due to the complexity of the condensate feeds, significant peak overlap occurs in the GC-FID analysis, making it difficult to accurately estimate the mass% linear paraffin content that will be obtained in the hydrogenated products. Inlet hydrogenation GC-FID analysis simplifies the prediction of the mass% linear content that can be expected in the paraffin product fractions from the analysis of a plant feed since the feed is hydrogenated in the GC inlet before GC-FID analysis. The results from this study showed that sufficient hydrogenation without significant peak tailing can be obtained in the GC inlet when using the appropriate mass and particle size Pd/Al₂O₃ catalyst with the optimum bed height. Inlet hydrogenation GC-FID analysis simplifies the prediction of the mass% linear content that can be expected in the paraffin product fractions. The method can be implemented on routine GC-FID instrumentation by simply installing an inlet liner containing an appropriate catalyst, that could be re-used at least 20 times, and avoids the purchasing of additional instrumentation and complex data processing and is suitable for commercial process control.

Advanced Biofuels Based on Fischer-Tropsch Synthesis for Applications in Diesel Engines

This paper focuses on the evaluation of the fuel properties of Fischer-Tropsch diesel blends with conventional diesel. Incorporating this advanced fuel into conventional diesel production will enable the use of waste materials and non-food materials as resources, while contributing to a reduction in dependence on crude oil. To evaluate the suitability of using Fischer-Tropsch diesel, cetane number, cetane index, CFPP, density, flash point, heat of combustion, lubricity, viscosity, distillation curve, and fuel composition ratios using multidimensional GC × GC-TOFMS for different blends were measured. It was found that the fuel properties of the blended fuel are comparable to conventional diesel and even outperform conventional fuel in some parameters. All measurements were performed according to current standards, thus ensuring the repeatability of measurements for other research groups or the private sector.

Quantitative carbon distribution analysis of hydrocarbons, alcohols and carboxylic acids in a Fischer-Tropsch product from a Co/TiO2 catalyst during gas phase pilot plant operation

Comprehensive two-dimensional gas chromatography (GCxGC) analysis for 1-alcohols and gas chromatography–mass spectrometry (GC-MS) analysis for carboxylic acids, derivatised as their methyl esters, have been applied to liquid and wax Fischer-Tropsch (FT) hydrocarbon products. These methods in combination with conventional one-dimensional gas chromatography (GC) analysis of the aqueous, gaseous, liquid hydrocarbon and wax products plus conventional high-performance liquid chromatography (HPLC) analysis of the aqueous phase has allowed a quantitative distribution analysis of FT hydrocarbon and oxygenated products to be demonstrated for a Co/TiO2 catalyst operating in a fixed bed gas phase pilot plant utilising CANSTM catalyst carrier devices. The GC-MS method used is, to the best of our knowledge, the first application of this derivatisation route for the quantification of individual carboxylic acids in FT hydrocarbon product streams.

Whilst the hydrocarbons and oxygenates that were identified are known compounds formed during the low temperature, Co catalysed, FT process the combination of the multiple analysis techniques used has allowed a level of detail to be gained on the product composition that is seldom reported.

Additionally, 1H nuclear magnetic resonance spectroscopy (NMR) and 13C NMR analyses were used to quantify the average concentration of 1-olefin, cis- and trans-2-olefins, 1-alcohol and aldehyde as appropriate for the technique used. Comparison of GCxGC versus 1H NMR and GC-MS versus a KOH titration confirmed the applicability of the chromatographic methods for the quantitative analysis of FT oxygenated compounds. Long-chain 1-alcohols and carboxylic acids, ≥ C3, were found to be present at levels of 1/10th and 1/1000th that of hydrocarbons of equivalent carbon chain length respectively. The 1-olefin:n-paraffin ratio in the hydrocarbon liquid and wax products was found to decrease significantly with increasing carbon chain length and much more so than those of the 2-olefin or 1-alcohol.

Advantages of comprehensive two-dimensional gas chromatography for comprehensive analysis of potential migrants from food contact materials

All substances migrating from food contact materials (FCMs), such as packagings, into food must be safe. This presupposes comprehensive analysis of all constituents potentially reaching a concentration in food that may be of toxicological concern. There is no single technique meeting this task and usually several need to be combined. In many cases, comprehensive two-dimensional gas chromatography (GCxGC) is the best technique available to start with. It provides high resolution and an overview in well-structured plots, grouping similar substances in a manner facilitating identifications. Further, flame ionization detection (FID) enables approximate quantitation without standards, and electron impact (EI) fragmentation in mass spectrometry (MS) provides access to large libraries for identification. GC is limited in amenable molecular mass, but the characterization of the lower mass constituents is usually helpful also for the identification of higher mass ones by techniques like HPLC-MS. The scope of this paper is to advocate the use of GCxGC for comprehensive migrate analysis, based on advantages illustrated by examples.

Accumulation of mineral oil saturated hydrocarbons (MOSH) in female Fischer 344 rats: Comparison with human data and consequences for risk assessment

Female Fischer 344 rats were orally exposed to a mixture of mineral oil saturated hydrocarbons (MOSH) of broad molecular mass range at doses of 40, 400 and 4000mg/kg feed. Amounts and compositions of the MOSH were analyzed in liver, spleen, adipose tissue and the carcass after exposure during 30, 60, 90 and 120d as well as after 90d exposure followed by 30d depuration. At 40mg/kg in the feed, after 30d of exposure, 10.9% of the ingested MOSH were recovered from the animal body; after 90d plus 30d depuration it was 3.9%. In liver and spleen, the maximum retention in terms of molecular mass (simulated distillation) was at n-C₂₉; in adipose tissue and carcass it was at n-C_15/16. The differentiation between MOSH below and above n-C₂₅ (Class I versus Class II and III oils), used for present regulation, is not supported by the present data on accumulation; structural characteristics seem more pertinent than molecular mass. Concentrations in the tissues increased far less than proportionally with the dose, rendering linear extrapolation to low doses questionable. No steady state was reached after 120d. In fact, comparing with the concentrations in human tissues at the estimated exposure, extrapolation from animal experiments seems to grossly underestimate human internal exposure. Comprehensive two-dimensional gas chromatography (GCxGC) was used to characterize the MOSH residues in the tissues with the aim of identifying the most strongly accumulated types. In the liver and spleen, the highly branched hydrocarbons dominated, whereas in the adipose tissue it was the n-alkanes and species with main n-alkyl moieties. Strong MOSH accumulation is not of concern per se, but the safety at the high concentrations in human tissues needs to be re-evaluated, possibly taking into account also end points other than granuloma formation.

Mineral oil in human tissues, part II: characterization of the accumulated hydrocarbons by comprehensive two-dimensional gas chromatography

Mineral oil hydrocarbons are by far the largest contaminant in the human body. Their composition differs from that in the mineral oils humans are exposed to, and varies also between different tissues of the same individual. Using the presently best technique for characterizing the composition of mineral oil hydrocarbons, comprehensive two-dimensional gas chromatography (GC×GC), the hydrocarbons in human tissues were compared to those of various mineral oils. This provided information about the strongly accumulated species and might give hints on the flow path through the human body. The selectivity of accumulation is probably also of interest for the risk assessment of synthetic hydrocarbons (polyolefins). GC×GC grouped the MOSH into classes of n-alkanes, paraffins with a low degree of branching, multibranched paraffins and naphthenes (alkylated cyclic hydrocarbons) with 1-4 rings. Metabolic elimination was observed for constituents of all these classes, but was selective within each class. The MOSH in the subcutaneous abdominal fat tissues and the mesenteric lymph nodes (MLN) had almost the same composition and included the distinct signals observed in mineral oil, though in reduced amounts relative to the cloud of unresolved hydrocarbons. The MOSH in the liver and the spleen were different from those in the MLN and fat tissue, but again with largely identical composition for a given individual. Virtually all constituents forming distinct signals were eliminated, leaving an unresolved residue of highly isomerized hydrocarbons.

Comprehensive two-dimensional gas chromatography for characterizing mineral oils in foods and distinguishing them from synthetic hydrocarbons

Many foods are contaminated by hydrocarbons of mineral oil or synthetic origin. High performance liquid chromatography on-line coupled with gas chromatography and flame ionization detection (HPLC-GC-FID) is a powerful tool for the quantitative determination, but it would often be desirable to obtain more information about the type of hydrocarbons in order to identify the source of the contamination and specify pertinent legislation. Comprehensive two-dimensional gas chromatography (GC×GC) is shown to produce plots distinguishing mineral oil saturated hydrocarbons (MOSH) from polymer oligomeric saturated hydrocarbons (POSH) and characterizing the degree of raffination of a mineral oil. The first dimension separation occurred on a phenyl methyl polysiloxane, the second on a dimethyl polysiloxane. Mass spectrometry (MS) was used for identification, FID for quantitative determination. This shows the substantial advances in chromatography to characterize complex hydrocarbon mixtures even as contaminants in food.

Flow-modulated comprehensive two-dimensional gas chromatography with simultaneous flame ionization and quadrupole mass spectrometric detection

Flow-modulated comprehensive two-dimensional gas chromatography with simultaneous monitoring of the separation by flame ionization (GC × GC-FID) and quadrupole mass spectrometric (GC × GC-qMSD) detection was studied for the analysis of gasoline and kerosene samples. The acquisition frequency of the FID was 100 Hz and of the qMSD 18 Hz for the mass range m/z 40-300. The instrumental set-up is such that both one-dimensional (GC-FID and GC-qMSD) and two-dimensional separations using the same working conditions can be performed. Gasoline and kerosene samples were analyzed on the column combination HP-5MS ((1)D)+HP INNOWax ((2)D). Three modulated peaks were obtained for each hydrocarbon present above 0.1% with ca. 300 ms peak width at the base using 6 s modulation times. Modulated peaks in GC × GC-FID were thus characterized by ca. 30 points while those in GC × GC-qMSD method by 6-8 points only. The FID speed is sufficient for reliable quantitative analysis, while the qMSD scan speed is perfectly appropriate for identification purposes. Moreover, in the GC × GC-qMSD method considerably improved quality of uncorrected spectra was obtained, arising from the enhanced separation over one-dimensional GC-MSD analysis. Spectral match qualities of up to 98% were found.