16 research outputs found
PLS models for determination of SARA analysis of Colombian vacuum residues and molecular distillation fractions using MIR-ATR
Modelos PLS para determinación del Análisis SARA en residuos de vacío y fracciones de destilación molecular usando MIR-ATR PLS modelos para determinação da análise SARA em resíduos de vácuo e frações de destilação molecular utilizando MIR-ATR Abstract In this work, prediction models of Saturates, Aromatics, Resins and Asphaltenes fractions (SARA) from thirty-seven vacuum residues of representative Colombian crudes and eighteen fractions of molecular distillation process were obtained. Mid-Infrared (MIR) Attenuated Total Reflection (ATR) spectroscopy in combination with partial least squares (PLS) regression analysis was used to estimate accurately SARA analysis in these kind of samples. Calibration coefficients of prediction models were for saturates, aromatics, resins and asphaltenes fractions, 0.99, 0.96, 0.97 and 0.99, respectively. This methodology permits to control the molecular distillation process since small differences in chemical composition can be detected. Total time elapsed to give the SARA analysis per sample is 10 minutes. Keywords: MIR-ATR, PLS, SARA analysis, molecular distillation, vacuum residue. Resumen En este trabajo se obtuvieron modelos predictivos para la determinación de la fracción de saturados, aromáticos, resinas y asfáltenos (SARA) en fondos de vacío y sus fracciones, a partir del análisis de treinta siete muestras de dichos fondos. Se utilizó espectroscopia infrarroja en el modo de reflectancia total atenuada en combinación con regresión de mínimos cuadrados parciales para predecir de manera relativamente exacta el análisis SARA. Los coeficientes de regresión para la calibración fueron de 0,99, 0,96, 0,97 y 0,99 para los modelos predictivos de saturados, aromáticos, resinas y asfáltenos, respectivamente. El tiempo requerido para el análisis SARA por muestra fue de 10 minutos. Palabras claves: MIR-ATR, PLS, análisis SARA, destilación molecular, fondos de vacío. Resumo Neste trabalho, os modelos preditivos para determinar a fração de saturados, aromáticos, resinas e asfaltenos (SARA) em fundos de vácuo e suas frações foram obtidas a partir da análise de trinta e sete amostras de fundos. A espectroscopia de infravermelho foi utilizada em modo de reflectância total atenuada em combinação com regressão parcial para prever com precisão relativamente à SARA análise dos mínimos quadrados. Os coeficientes de regressão para calibração foram de 0,99, 0,96, 0,97 e 0,99 para os modelos preditivos saturados, aromáticos, resinas e asfaltenos, respectivamente. O tempo necessário para a análise SARA por amostra foi de 10 minutos. Palavras-chave:MIR-ATR, PLS, análise SARA, a destilação molecular, fundos de vácuo. Orrego-Ruiz JA, Cabanzo R, Mejía-Ospino E. PLS models for determination of SARA analysis of Colombian vacuum residues and molecular distillation fractions using MIR-ATR. 2014;27(1):43-48
PLS models for determination of SARA analysis of Colombian vacuum residues and molecular distillation fractions using MIR-ATR
Modelos PLS para determinación del Análisis SARA en residuos de vacío y fracciones de destilación molecular usando MIR-ATR PLS modelos para determinação da análise SARA em resíduos de vácuo e frações de destilação molecular utilizando MIR-ATR Abstract In this work, prediction models of Saturates, Aromatics, Resins and Asphaltenes fractions (SARA) from thirty-seven vacuum residues of representative Colombian crudes and eighteen fractions of molecular distillation process were obtained. Mid-Infrared (MIR) Attenuated Total Reflection (ATR) spectroscopy in combination with partial least squares (PLS) regression analysis was used to estimate accurately SARA analysis in these kind of samples. Calibration coefficients of prediction models were for saturates, aromatics, resins and asphaltenes fractions, 0.99, 0.96, 0.97 and 0.99, respectively. This methodology permits to control the molecular distillation process since small differences in chemical composition can be detected. Total time elapsed to give the SARA analysis per sample is 10 minutes. Keywords: MIR-ATR, PLS, SARA analysis, molecular distillation, vacuum residue. Resumen En este trabajo se obtuvieron modelos predictivos para la determinación de la fracción de saturados, aromáticos, resinas y asfáltenos (SARA) en fondos de vacío y sus fracciones, a partir del análisis de treinta siete muestras de dichos fondos. Se utilizó espectroscopia infrarroja en el modo de reflectancia total atenuada en combinación con regresión de mínimos cuadrados parciales para predecir de manera relativamente exacta el análisis SARA. Los coeficientes de regresión para la calibración fueron de 0,99, 0,96, 0,97 y 0,99 para los modelos predictivos de saturados, aromáticos, resinas y asfáltenos, respectivamente. El tiempo requerido para el análisis SARA por muestra fue de 10 minutos. Palabras claves: MIR-ATR, PLS, análisis SARA, destilación molecular, fondos de vacío. Resumo Neste trabalho, os modelos preditivos para determinar a fração de saturados, aromáticos, resinas e asfaltenos (SARA) em fundos de vácuo e suas frações foram obtidas a partir da análise de trinta e sete amostras de fundos. A espectroscopia de infravermelho foi utilizada em modo de reflectância total atenuada em combinação com regressão parcial para prever com precisão relativamente à SARA análise dos mínimos quadrados. Os coeficientes de regressão para calibração foram de 0,99, 0,96, 0,97 e 0,99 para os modelos preditivos saturados, aromáticos, resinas e asfaltenos, respectivamente. O tempo necessário para a análise SARA por amostra foi de 10 minutos. Palavras-chave:MIR-ATR, PLS, análise SARA, a destilação molecular, fundos de vácuo. Orrego-Ruiz JA, Cabanzo R, Mejía-Ospino E. PLS models for determination of SARA analysis of Colombian vacuum residues and molecular distillation fractions using MIR-ATR. 2014;27(1):43-48
Finding a relationship between the composition and the emulsifying character of asphaltenes through FTICR-MS
ABSTRACT In this work, n-heptane insoluble fractions (asphaltenes) from six crude oils were analyzed by means of Fourier-transform ion cyclotron resonance mass spectrometry (FTICR MS) using both positive Atmospheric Pressure Photo Ionization (+) APPI and negative Electro-Spray Ionization (-) ESI in order to understand their water-oil emulsion stabilization capability on a molecular level basis. Through (+) APPI it was possible to obtain an overview of samples composition. By sorting as nitrogen sulfur and oxygen containing compounds, it was possible to compositionally distinguish the asphaltenes. Through (-) ESI, several differences were also observed by grouping the classes as oxygen (NxOy+NxOySz+Oy+OySz) and non oxygen containing classes (Nx+NxSz). The interactions of these two groups of compounds must be considered in order to understand the water-oil emulsion stability. It implies that the cores where nitrogen and sulfur are part may interact via n-n stacking, while the oxygen containing compounds may interact either via hydrogen bonding or via dipole forces with the aromatic aggregates (highly polarizable), forming potentially surface active aggregates. Thus, the rate between these two families of compounds may determine the surfactant character of asphaltenes at the water-oil interface. Bearing this in mind, an emulsion stability coefficient was proposed based on the relative abundances of some families of compounds detected by (-) ESI-FTICR-MS to explain the crude oils' tendency to form emulsions.RESUMEN En el presente trabajo, las fracciones iiinsolubles en n-heptano (asfaltenos) de seis crudos fueron analizadas por espectrometría de masas de resonancia Ion-Ciclotrón con transformada de Fourier (FT-ICR MS) utilizando ionización de presión atmosférica en modo positivo (+) APPI e ionización electro-spray en modo negativo, con el fin de comprender a nivel molecular su capacidad de estabilización de emulsiones agua-aceite. A través de (+) APPI, fue posible obtener una visión general de la composición de las muestras. Al ordenar los compuestos como azufrados-nitrogenados, y oxigenados fue posible distinguir composicionalmente los asfaltenos. A través de (-) ESI también se observaron varias diferencias, al agrupar los compuestos detectados como los que contienen oxígeno (NxOy + NxOySz + Oy + OySz) y los que no contienen oxígeno (Nx + NxSz). Las interacciones de estos dos grupos de compuestos deben considerarse para comprender la estabilidad de la emulsión agua-aceite. Esto implica que los núcleos donde el nitrógeno y el azufre son parte pueden interactuar mediante apilamiento n-n, mientras que los compuestos que contienen oxígeno pueden interactuar mediante enlaces de hidrógeno o mediante fuerzas dipolo con los agregados aromáticos (altamente polarizables) formando agregados superficialmente activos. Es decir, la relación entre estas dos familias de compuestos puede determinar el carácter tensioactivo de los asfaltenos en la interfaz agua-aceite. Teniendo esto en cuenta, se propuso un coeficiente de estabilidad de emulsiones basado en las abundancias relativas de algunas familias de compuestos detectadas por (-) ESI-FT-ICR.MS que permita luego explicar la tendencia de los aceites crudos a formar emulsiones
Distribution of Oxygen-Containing Compounds and Its Significance on Total Organic Acid Content in Crude Oils by ESI Negative Ion FT-ICR MS
In
the present work the distribution of oxygen compounds in the
total organic acid content of ten crude oils was assessed by means
of negative ion electrospray ionization Fourier transform ion cyclotron
resonance mass spectrometry ((−) ESI FT-ICR-MS). As a first
attempt, the relative abundance of the O2 class was related to the
total acid number (TAN) for samples following the state of the art,
and no positive correlation was achieved. Therefore, we performed
the selective isolation of acidic compounds via solid phase extraction
using amino-propyl silica (APS), finding an acceptable correlation
(<i>R</i><sup>2</sup> = 0.98) between acidic fraction percentage
and TAN. Both the reliability and performance of the APS method were
confirmed using a chosen sample as control. FT-IR spectroscopy was
employed to validate the acidic nature of the isolated fraction. In
the IR spectrum of the acidic fractions, characteristic signals of
carboxylic acids, such as the sharp band around 1700 cm<sup>–1</sup> and the wide band around 2300–3500 cm<sup>–1</sup>, were identified. Additionally in such fractions, oxygenated classes
such as O2, NO2, O3, SO2, and O3S were detected through (−)
ESI FT-ICR-MS. Nevertheless, it can be said that none of these classes
exclusively belong to the acidic fraction since for instance, O2 and
NO2 compounds were found in both nonacid and acid fractions. In this
sense, some O2 compounds may be considered to be bifunctionalized
alcohols, phenols, ketones, or ethers. Finally, by comparing the contour
plots DBE vs carbon number of chosen samples, it was possible to infer
that the contribution of the O2 class over the TAN is structure dependent
for samples with TAN lower than 0.5 mg KOH/g. Thus, the DBE distribution
within the acidic and nonacidic fractions must be carefully considered
in order to estimate their relevance over the total acid content
Combination of Negative Electrospray Ionization and Positive Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry as a Quantitative Approach of Acid Species in Crude Oils
Crude
oils differ from one another in numerous chemical and physical
properties, many of which play an important role in defining their
quality and price. Generally, statistical analysis of price differentials
has focused on two main properties: density and sulfur content. However,
the growing significance of high total acid number (TAN) crude oils,
especially from developing countries, has aroused the necessity for
extending these models. Consequently, refineries must obtain real
and exact information regarding crude oil quality to achieve optimal
crude oil selection and processing decisions. This could be attained
when a detailed molecular-level characterization is performed. The
present work presents the combination of negative electrospray ionization
[(−)ESI] and positive atmospheric pressure photoionization
[(+)APPI] Fourier transform ion cyclotron resonance (FT-ICR) mass
spectrometry, as a prominent approach to semi-quantify the acid species
comprised in crude oils. A novel polarity index is proposed that corrects
the relative abundances of (−)ESI classes, where mainly acid
species are detected. By consideration of different indexes, it was
possible to enhance the correlation coefficients (<i>R</i><sup>2</sup>) from 0.579 to 0.986 between the percentage of acid
compounds and TAN of crude oils, where most of the samples stand close
to a linear tendency. These results avoid the deviations observed
in previous works on the correlations between relative abundances
of the O2 class through (−)ESI and TAN and could support achieving
optimal crude oil selection and defining their quality and price
Characterization of Acid Species in Asphaltenic Fractions by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry and Infrared Spectroscopy
Despite
significant advances in the characterization
of asphaltenes,
the study of this fraction of crude oil remains challenging for the
scientific community and oil companies. It is well-known that asphaltenes
are responsible for many of the difficulties found in the extraction,
production, transportation, storage, and refining of petroleum. Although
they are defined as the fraction of crude oil that is insoluble in
paraffinic solvents of low-molecular-weight-type n-heptane (C7) or n-pentane (C5), asphaltenes present a great compositional variety, concentrate
a variety of elements (among which nitrogen, oxygen, sulfur, vanadium,
and nickel stand out), apart from hydrogen and carbon, and are distinguished
by grouping the molecules with greater aromaticity of crude oil. Given
its high compositional and structural complexity, associating operational
problems with specific characteristics of asphaltenes is a task that
is still in force. Asphaltenes, in addition to being distinguished
by their high aromaticity, are also known for their acid–base
properties. The acid character varies according to the origin of the
asphaltenes and is related to the presence of carboxylic acids, phenols,
carbazoles, and indoles. The basic character can be attributed to
the presence of amines, amides, and other nitrogen-containing compounds.
Progressing in the detailed compositional characterization of the
polar compounds comprising the n-heptane-insoluble
fraction (asphaltenes) is still a necessary task toward the understanding
of asphaltene aggregation phenomena and the relationship with crude
oil properties, such as interfacial tension and viscosity. In the
present work, the naphthenic acids of the insoluble fractions of five
Colombian crude oils were characterized. The n-heptane-insoluble
fraction was subjected to a washing process affording four subfractions,
named as extractable 48 h, extractable 72 h, and extractable 96 h,
which correspond to the heptane-soluble fractions that were recovered
after each indicated time, and asphaltene 96 h, which corresponds
to the remaining heptane-insoluble compounds after 96 h of washing.
The samples were chosen so that they had a wide range of asphaltene
content that varied from 3.0 to 19.2%. The acid fraction was obtained
from each sample by solid-phase extraction using aminopropyl silica
as an adsorbent material
Exploring Compositional Changes along In Situ Combustion and Their Implications on Emulsion Stabilization via Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS)
In
situ combustion (ISC) is one of the highest potential enhanced
oil recovery (EOR) processes for heavy oils. However, several operational
issues, including the formation of highly stable emulsions, have limited
its application. Disclosing the physicochemical proprieties of these
emulsions, especially the chemical nature of the compounds involved
in the stabilization process, has become relevant for the success
of ISC projects. In the present work, the physicochemical changes
at a laboratory-scale low-temperature oxidation (LTO) regimen performed
over a Colombian heavy crude oil were followed by mass spectrometry.
The compositional analyses were performed using both positive-ion
atmospheric pressure photoionization ((+) APPI) and negative-ion electrospray
ionization ((−) ESI) Fourier transform ion cyclotron resonance
mass spectrometry (FT-ICR MS). Further isolation of acidic compounds
and surface-active species allowed us to determine that the process
incorporates a wide variety of compounds to build up the O/W (oil/water)
interface, thus increasing the stabilizing tendency of the emulsions.
During the combustion, oxygen is chemically incorporated to the crude
over hydrocarbon compounds, as well as over sulfur- and nitrogen-containing
compounds, generating classes such as O, O2, O3, O4, OS, NO2, and
NO3 that explain the high viscosity and high stability of the emulsions
Detailed Characterization of Petroleum Sulfonates by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
Petroleum
sulfonates obtained from heavy vacuum gas oil (HVGO)
were characterized by negative electrospray ionization Fourier transform
ion cyclotron resonance mass spectrometry [(−) ESI FT-ICR MS]
to better understand the chemical nature of their surface-active components.
Electrospray ionization (ESI) analysis showed that sulfonates contain
mainly O3S, O3S2, O4S, and NO3S classes, which means that the sulfonation
reaction does not occur selectively for aromatic hydrocarbon (HC)
class compounds because it also reacts with N, S, and O heteroatom
classes. Because sulfonates were separated by solubility into lipophilic
and hydrophilic categories, it was confirmed that the same classes
compose hydrophilic and lipophilic sulfonates. Moreover, this procedure
revealed that lipophilic sulfonate extracts contain organic acids
(O2 class) that are related to the total acid number of the starting
HVGO. However, selective isolation of the surface-active species using
the “wet-silica” procedure allowed for detection that
these compounds have a non-surface-active character because they do
not interact with the water phase. The new structural information
disclosed about petroleum sulfonates and their raw materials might
encourage further studies on the rational design and synthesis of
novel petroleum surfactants with the desired properties for industrial
applications, such as chemical enhanced oil recovery (CEOR)
Composition to Interfacial Activity Relationship Approach of Petroleum Sulfonates by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
In the present work, petroleum sulfonates
were obtained from three
atmospheric residues (ARs) and characterized by negative-ion electrospray
ionization Fourier transform ion cyclotron resonance mass spectrometry
[(−) ESI FT-ICR MS], looking for an approach to establish a
relationship between molecular composition and interfacial activity
for chemical enhanced oil recovery (CEOR) formulations. From the correlation
of the (−) ESI FT-ICR MS data and the interfacial tension measurements,
it was possible to infer that the composition and some characteristics,
such as aromatic and/or naphthenic condensation, must be taken into
account to understand the performance of petroleum sulfonates. Obtained
sulfonates contained mainly O3S, NO3S, O3S2, and O4S compounds, but
the relative abundance of each class depended directly upon the chemical
composition of the raw AR. Both carbon number (CN) and double bound
equivalent (DBE) distributions of the main classes provided a way
to explain the lipophilicity and interfacial activity of the sulfonates.
This information can be useful to establish the initial characteristics
desired in ARs to produce petroleum sulfonates with appropriate capabilities
for CEOR applications
Identification of Refractory Weakly Basic Nitrogen Compounds in a Deeply Hydrotreated Vacuum Gas Oil and Assessment of the Effect of Some Representative Species over the Performance of a Ni–MoS<sub>2</sub>/Y-Zeolite–Alumina Catalyst in Phenanthrene Hydrocracking
Heavy crude oil processing
leads the way in current refining. These
crudes yield larger amounts of distillable heavy fractions such as
vacuum gas oil (VGO). VGO must be treated in at least two refining
units: a hydrotreating unit where sulfur, nitrogen, and other heteroatoms
are removed, and a hydrocracking unit where suitable fuels are obtained.
Removal of heteroatoms during hydrotreating, particularly, nitrogen,
dictates the efficiency of hydrocracking. In the first part of this
work, the nature of refractory nitrogen-containing compounds on the
performance of a hydrotreating catalyst was evaluated. To achieve
this goal, both a VGO and its hydrotreated counterpart were studied
using electrospray ionization with Fourier transform ion cyclotron
resonance mass spectrometry (ESI-FT-ICR-MS). Weakly basic N-containing
compounds, namely, heavy pyrrolic-like compounds and their partially
hydrogenated derivatives, were found to be the most refractory to
hydrotreating. These compounds are weakly basic compared to most nitrogen
compounds present in VGO. Considering this finding, the second part
of the work was devoted to assessing the effect of pyrroles on the
reactivity of phenanthrene over a Ni–MoS<sub>2</sub>/Y-zeolite–alumina
two-stage hydrocracking catalyst. Tests were carried out in a fixed-bed
reactor using mixtures of carbazole and tetrahydrocarbazole. Results
showed that these compounds can affect the catalytic performance of
Ni–MoS<sub>2</sub>/Y-zeolite–alumina by reducing its
activity and inhibiting its selectivity to hydrocracking products.
These findings draw attention to the possible role of weakly basic
nitrogen compounds in the catalytic performance of materials employed
for two-stage hydrocracking units