Effect of nitrogen compounds on deactivation of hydrotreating catalysts by coke

Differentiation of Seven Isomeric n-Pentylquinoline Radical Cations Based on Energy-Resolved Medium-Energy Collision-Activated Dissociation

Asphaltenes, a major and undesirable component of heavy crude oil, contain many different types of large aromatic compounds. These compounds include nitrogen-containing heteroaromatic compounds that are thought to be the main culprit in the deactivation of catalysts in crude oil refinery processes. Unfortunately, prevention of this is challenging as the structures and properties of the nitrogen-containing heteroaromatic compounds are poorly understood. To facilitate their structural characterization, an approach based on ion-trap collision-activated dissociation (ITCAD) tandem mass spectrometry followed by energy-resolved medium-energy collision-activated dissociation (ER-MCAD) was developed for the differentiation of seven isomeric molecular radical cations of n-pentylquinoline. The fragmentation of each isomer was found to be distinctly different and depended largely on the site of the alkyl side chain in the quinoline ring. In order to better understand the observed fragmentation pathways, mechanisms for the formation of several fragment ions were delineated based on quantum chemical calculations. The fast benzylic α-bond cleavage that dominates the fragmentation of analogous nonheteroaromatic alkylbenzenes was only observed for the 3-isomer as the major pathway due to the lack of favorable low-energy rearrangement reactions. All the other isomeric ions underwent substantially lower-energy rearrangement reactions as their alkyl chains were found to interact mostly via 6-membered transition states either with the quinoline nitrogen (2- and 8-isomers) or the adjacent carbon atom in the quinoline core (4-, 5-, 6-, and 7-isomers), which lowered the activation energies of the fragmentation reactions. The presented analytical approach will facilitate the structural characterization of nitrogen-containing heteroaromatic compounds in asphaltenes.

Adsorption of heterocyclic sulfur and nitrogen compounds in liquid hydrocarbons on activated carbons modified by oxidation: capacity, selectivity and mechanism

Careful design and modification of carbon adsorbents was performed to selectively remove undesired compounds from liquid hydrocarbons.

Sequential hydrothermal fractionation of yeast Cryptococcus curvatus biomass

A sequential hydrothermal liquefaction (SEQHTL) process was evaluated in this work for fractionating different component of yeast biomass. Sugar and protein were separated first at a lower temperature, and the remaining biomass was then converted to bio-oil at a higher temperature. The separated aqueous products were investigated to be recycled as a carbon and nitrogen sources for the yeast culture. In the first step of SEQHTL, the temperature effect on the yield of sugar/protein and inhibitory compounds (acetic acid and 5-hydroxymethyl furfural (5HMF)) was investigated. The highest yields of sugar and protein and a minimal level of inhibitory compounds were obtained at 180°C. At the second step of SEQHTL, the highest bio-oil yield was achieved at 240°C. In comparison to the one-step hydrothermal liquefaction process, SEQHTL produced a higher quality bio-oil with higher fatty acid and lower nitrogen contents.