Biosynthesis of alkanes/alkenes from fatty acids or derivatives (triacylglycerols or fatty aldehydes).

This review summarizes the most relevant advances in the biological transformation of fatty acids (or derivatives) into hydrocarbons to be used as biofuels (biogasoline, green diesel and jet biofuel). Among the used enzymes, the fatty acid decarboxylase from Jeotgalicoccus sp. ATCC 8456 (OleTJE) stands out as a promising enzyme. OleTJE may be coupled in cascade reactions with metalloenzymes or reductases from the Old Yellow Enzymes (OYE) family to perform the hydrogenation of α-olefins into paraffins. The photodecarboxylase from Chlorella variabilis NC64A (CvFAP) is an example of coupling biocatalysis and photocatalysis to produce alkanes. Besides the (photo)decarboxylation of free fatty acids and/or triacyclglycerols to produce alkanes/alkenes, by enzymes has also been employed. The cyanobacterial aldehyde decarbonylase (cAD) from Nostoc punctiforme is an outstanding example of this kind of enzymes used to produce alkanes. Overall, these kinds of enzymes open up new possibilities to the production of biofuels from renewable sources, even if they have many limitations on the current situation. The possibilities of improving enzymes features via immobilization or coimmobilization, as well as the utilization of whole cells haves been also reviewed.

Representative Pores: An Efficient Method to Characterize Activated Carbons.

We propose a pore size analysis methodology for carbonaceous materials that reduces complexity while maintaining the significant elements of the structure-property relationship. This method chooses a limited number of representative pores, which will constitute a simplified kernel to describe the pore size distribution (PSD) of an activated carbon. In this study we use the representative pore sizes of 7.0, 8.9, 18.5, and 27.9 Å and N2 isotherms at 77.4 K to determine the PSD which is later applied to predict the adsorption equilibrium of other gases. In this study we demonstrate the ability to predict adsorption of different gas molecules on activated carbon from the PSD generated with representative pores (PSDrep). The methodology allows quick solutions for large-scale calculations for carbonaceous materials screening, in addition to make accessible an easily understood and prompt evaluation of the structure-property relationship of activated carbons. In addition to the details of the methodology already tested in different fields of application of carbonaceous materials, we present a new application related to the removal of organic contaminants in dilute aqueous solutions.

Rapid assessment of total and polycyclic aromatic contents in heavy oils.

The monitoring of the content of polycyclic aromatic hydrocarbons (PAHs) is important for evaluating heavy oil products, especially those most likely to cause environmental impacts. In this study, a comparison between samples of heavy petroleum fractions, using different methods, was carried out. The calculation of carbon distribution and polycyclic aromatic contents was compared with other methods using Fourier transform infrared spectroscopy (FTIR). Therefore, it was possible to quickly estimate the aromatic content by the FTIR method, and the results showed consistency with those obtained through traditional methods. A rapid method, using extraction with dimethyl sulfoxide followed by FTIR measurements, was proposed and shown as particularly useful and reliable for a quick quantification of the PAH content, when compared to the traditional IP 346 method. Furthermore, the difference in total aromatic and PAH concentrations may be more clearly established. This rapid method may be used for the evaluation of PAH content in samples obtained from studies for their removal from complex heavy oil fractions.

Unusual adsorption site behavior in PCN-14 metal-organic framework predicted from Monte Carlo simulation.

The adsorption equilibrium of methane in PCN-14 was simulated by the Monte Carlo technique in the grand canonical ensemble. A new force field was proposed for the methane/PCN-14 system, and the temperature dependence of the molecular siting was investigated. A detailed study of the statistics of the center of mass and potential energy showed a surprising site behavior with no energy barriers between weak and strong sites, allowing open metal sites to guide methane molecules to other neighboring sites. Moreover, this study showed that a model assuming weakly adsorbing open metal clusters in PCN-14, densely populated only at low temperatures (below 150 K), can explain published experimental data. These results also explain previously observed discrepancies between neutron diffraction experiments and Monte Carlo simulations.