Linzhou Zhang

Characterization of heavy petroleum fraction by positive-ion electrospray ionization FT-ICR mass spectrometry and collision induced dissociation: Bond dissociation behavior and aromatic ring architecture of basic nitrogen compounds

This paper examined the bond dissociation behavior and aromatic ring architecture of basic nitrogen compounds in Sudan heavy petroleum fraction. Both broadband and quadrupole isolation modes positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with collision induced dissociation (CID) techniques were used to characterize a low sulfur crude oil derived vacuum residuum (VR). The appropriate CID operating condition was selected by comparing the molecular weight distributions of the basic nitrogen compounds under various CID operating conditions. Both odd- and even-electron fragment ions were observed from the mass spectrum, indicating that the heterolytic and homolytic bond cleavages occurred simultaneously during the CID process. The odd-electron fragment ions were predominant in each class species, indicating preferential heterolytic bond cleavages. At the optimal CID condition, the alkyl groups decomposed deeply and just left the aromatic cores of the nitrogen compounds. No significant variation in double bond equivalent (DBE) value was observed between the fragment and parent ions, revealing that the domination of single core structure.

Effects of cooling rate during casting on performance of metal hydride electrodes and nickel-metal hydride batteries

In this work, three Mm(Ni-Co-Mn-Al)(5) alloys with the same formula were produced by vacuum induction melting and casted at different cooling rates: normal cooling, fast cooling, rapid quenching. In addition, a portion of the rapidly quenched alloy was annealed. The crystallographic and structural properties and the electrochemical performance of these materials were characterized. For all the as-cast alloys, cooling rate did not significantly affect their activation process and cycle life. In contrast, the alloy, which was rapidly quenched and then annealed, displayed a longer cycle life. However, it required a long activation process to achieve its maximum capacity. The effects of metallurgical processes on the sealed cell. performance such as cycle life, internal gaseous pressure after charging, and storage behavior after formation were also examined

Collision cross section (CCS) measurement by ion cyclotron resonance mass spectrometry with short-time Fourier transform

RATIONALE The collision cross section (CCS) is an important shape parameter which is often used in molecular structure investigation. In Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), the CCS affects the ion signal damping shape due to the effect of ion-neutral collisions. It is potential to obtain ion CCS values from FTICR-MS with the help of a proper ion-collision model. METHODS We have developed a rapid method to obtain the ion damping profile and CCS for mixtures by only one FTICR-MS measurement. The method utilizes short-time Fourier transform (STFT) to process FTICR-MS time domain signals. The STFT-processed result is a three-dimensional (3D) spectrum which has an additional time axis in addition to the conventional mass-to-charge ratio and intensity domains. The damping profile of each ion can be recognized from the 3D spectrum. RESULTS After extracting the decay profile of a specified ion, all the three ion-neutral collision models were tested in curve fitting. The hard-sphere model was proven to be suitable for our experimental setup. A linear relationship was observed between the CCS value and hard-sphere model parameters. Therefore, the CCS values of all the peaks were obtained through the addition of internal model compounds and linear calibration. CONCLUSIONS The proposed method was successfully applied to determine the CCSs of fatty acids and polyalanines in a petroleum gas oil matrix. This technique can be used for simultaneous measurement of cross sections for many ions in congested spectra.

Petroleum heteroatom compounds in various commercial delayed coking liquids: characterized by FT-ICR MS and GC techniques

Delayed coking is an important petroleum resid conversion process. The processability of coking liquids is known to be dependent on the heteroatom compounds present in the coking liquids. Eight commercial delayed coking liquids were characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatographic techniques. High relatively abundant heteroatom compounds in the coking liquids were 1–4 aromatic-ring pyridinic nitrogen compounds, carbazoles, benzocarbazoles, phenols, mercaptans, benzothiophenes, dibenzothiophenes, and naphthobenzothiophenes. Coking liquids derived from various feeds had similar compound class types, molecular weight distribution ranges, and double bond equivalents (DBE). However, the concentration of individual compounds and the distribution of DBE versus carbon number of heteroatom compounds varied. A comparison of heteroatom compounds in coker feeds and products revealed the various reaction mechanism of heteroatom compounds occurred during the coking process. The results suggested that molecular-level process models can be developed for optimization of unit operation to obtain desirable products that meet the environmental specifications and quality requirements.

Molecular-Level Composition and Reaction Modeling for Heavy Petroleum Complex System

A new methodology for the molecule-based modeling of heavy petroleum mixtures has been developed. Molecules in the heavy feedstock have been described in terms of three essential structural attributes (cores, side chains, and inter-core linkages) and then statistically juxtaposed into a set of representative molecular compositions that can be constrained by a set of probability density functions (pdfs). In order to obtain the optimal molecular composition, an optimization loop was employed to minimize an objective function in terms of available measurements via adjusting the limited parameters of the pdfs. An example of resid feedstock containing 400,000 components was created using only O(30) parameters. To limit the kinetic model to a practical size, the reaction model was described in terms the reactions of the three constituent types and a set of irreducible molecules. Subsequent product property estimation was a straightforward juxtaposition of attributes. For example, a model for resid coking was built in terms of 2,839 attributes and equations but kept the full compositional details of the 400,000-molecule mixture.