Palladium(II) chemically bonded to silica surface applied to the separation and identification of polycyclic aromatic sulfur heterocycles in heavy oil

Abstract

Separation of polycyclic aromatic sulfur heterocycles among themselves and also from interferents in petrochemical matrices is a challenging task because of their low concentration, matrix complexity, and also due to the presence of polyaromatic hydrocarbons, as they present similar physico-chemical properties. Therefore, the objective of this work was preparation, characterization, and application of a stationary phase for separation of these compounds in a heavy gas oil sample and their identification by comprehensive two-dimensional gas chromatography. The stationary phase was prepared by grafting mercaptopropyltrimethoxisilane onto a silica surface, followed by palladium(II) chloride immobilization. Elemental analysis, thermogravimetry, nitrogen adsorption-desorption isotherms, infrared analysis, and scanning electron microscopy were performed to characterize this solid phase. Sulfur compounds were separated in an open column packed with the stationary phase and analyzed by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometric detection. The number of compounds tentatively identified was 314 and their classes were thiophenes, benzotiophenes, dibenzothiophenes, naphthothiophenes, benzonaphthothiophenes, and dinaphthothiophenes. Separation among sulfur compounds and polyaromatic hydrocarbons was successful, which is a difficult goal to achieve with the traditionally employed solid phases. Some recalcitrant compounds (dibenzothiophenes with substituents of two and four carbons) were fully separated and tentatively identified.

Mesoporous silica xerogel modified with bridged ionic silsesquioxane used to immobilize copper tetrasulfonated phthalocyanine applied to electrochemical determination of dopamine

“…It is possible to observe comparable images for all materials, indicating the supposed erosive process that occurs inside pores does not take place in the micrometric level. Furthermore, the immobilization process by shaking is softer than mechanical or magnetic stirring, which could produce grooves on silica surface [60].…”

Qualitative and Quantitative Evaluation of Sulfur-Containing Compound Types in Heavy Crude Oil and Its Fractions

“…A solution to this problem is offered through a method that has been reported by Andersson and co-workers who employed liquid chromatographic separation by ligand exchange chromatography (LEC) on a Pd­(II) stationary phase. ,− Compared to a gas chromatographic approach, liquid chromatography does offer only a limited separation power and often leads to a group type rather than an isomer separation for complex samples. In the case of the LEC separation presented here, this group selectivity is exploited for the quantification of different types of sulfur-containing species.…”

“…The first fraction (F1) holds mainly sulfur-free hydrocarbons, and the second (F2) consists of condensed thiophenic species (benzothiophenes and above). Though not mentioned in a number of publications, ,, a third fraction (F3) can be gained, which contains sulfidic species. Additionally, reports show noncondensed thiophenes to be eluted into the first (F1) fraction .…”

Atmospheric Solids Analysis Probe (ASAP) and Atmospheric Pressure Gas Chromatography (APGC) coupled to Quadrupole Time of Flight Mass Spectrometry (QTOF-MS) as alternative techniques to trace aromatic markers of mineral oils in food packaging

“…To find the right and useful markers for MOAH is not an easy task, as there are hundreds of aromatic hydrocarbons present in mineral oils [26][27][28]. Due to the complexity of mineral oils, conventional GC-MS technique is not enough to identify all potential markers and other techniques could be used.…”