Fractionation of pitches by molecular weight using continuous and semibatch dense-gas extraction

Edwards, William F.; Thies, Mark C.

doi:10.1016/j.carbon.2005.07.042

Cited by 29 publications

(37 citation statements)

References 11 publications

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“…To this end, our group [7,8] is investigating the use of dense-gas extraction (DGE) for the fractionation of petroleum pitches. Although the DGE concept is not new [9,10], its application to petroleum pitches with the goal of controlling MWD, is.…”

Section: Introductionmentioning

confidence: 99%

Control of the Molecular Weight Distribution of Petroleum Pitches via Dense‐Gas Extraction

Cervo

Thies

2007

Chem Eng & Technol

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Dense-gas extraction (DGE) was used to fractionate an isotropic petroleum pitch (number-average molecular weight M n = 516) into oligomeric cuts. A countercurrent-flow packed column was used to effect the separation, with supercritical toluene being used as the dense-gas solvent and commercially available M-50 or A-240 pitch being used as the feed. Isothermal operation at 330, 350, and 380°C was investigated, as well as operation with a linear positive temperature gradient (+DT), with the bottom of the column at 330 and the top at 380°C. For isothermal operation, the molecular weight distribution of the bottom products consisted primarily of dimer (M n = 508) and trimer (M n = 759) species, with pressure changes of as little as 5 bar producing significant changes in their relative distribution, as observed by MALDI mass spectrometry. On the other hand, by operating with a +DT, we could produce a bottom product consisting primarily of trimers and tetramers (M n = 997).

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Section: Introductionmentioning

confidence: 99%

Control of the Molecular Weight Distribution of Petroleum Pitches via Dense‐Gas Extraction

Cervo

Thies

2007

Chem Eng & Technol

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“…7, 2012 a mild formation of radical cations of polycyclic aromatic molecules, preventing unwanted fragmentation. 33,[37][38][39]41 According to Edwards et al, 33 the content of the matrix/pitch used in their study did not significantly affect the results. Thus, we chose the ratio 1:5 (analyte:matrix), the lowest studied.…”

Section: Sample Preparationmentioning

confidence: 75%

“…These results are in accordance with those previously reported by Edwards and Thies. 38,39,41 The results from Marzec 45 also showed a bimodal distribution of masses for coal, with regions between m/z 130-600 and 1300-3500.…”

Section: Studies By Maldi-tof-msmentioning

confidence: 91%

Mesophase evolution in heat-treated solid petroleum pitches

Lima¹,

Lima²,

França³

et al. 2012

J. Braz. Chem. Soc.

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Uma combinação de técnicas analíticas foi utilizada para acompanhar a evolução da mesofase em pixes de petróleo em fase sólida. As amostras foram caracterizadas por dessorção a laser assistida por matriz, seguida de espectrometria de massas por tempo de vôo (MALDI-TOF-MS), ressonância magnética nuclear de 13 C ( 13 C NMR) de alto campo, 1 H NMR de baixo campo, ressonância eletrônica de spin (EPR), microscopia ótica polarizada e análise termogravimétrica (TGA). A análise por MALDI-TOF-MS revelou uma distribuição oligomérica de pesos moleculares no pixe: monomérica (m/z 200 a 400), dimérica (m/z 400 a 650), trimérica (m/z 650 a 950) e tetramérica (m/z 950 a 1600), fator essential para a produção de fibras de carbono, bem como outros compósitos de carbono. Estudos de tempo de relaxação (T 1 ) permitiram a observação de duas grandes áreas: a dos aromáticos e a de mesofase. Estes resultados também mostraram que o tempo de aquecimento aumenta a área de mesofase. Através de medidas não destrutivas de 13 C NMR, foram obtidos os conteúdos de carbonos aromáticos e alifáticos, e também o grau de protonação desses carbonos. A microscopia ótica com luz polarizada mostrou as interfaces entre as regiões anisotrópicas e isotrópicas, bem como o processo de coalescência da mesofase. Os resultados obtidos pelas outras técnicas corroboram com os resultados de MALDI-TOF-MS e NMR.A combination of analytical techniques was used to follow the mesophase evolution of petroleum pitches in the solid phase. The samples were characterized by matrix assisted laser desorption and time of flight analysis by mass spectrometry (MALDI-TOF-MS), high field 13 C nuclear magnetic resonance ( 13 C NMR), low field 1 H NMR, electron spin resonance (EPR), polarized optical microscopy and thermogravimetric analysis (TGA). MALDI-TOF-MS revealed an oligomeric distribution of molecular weights in the pitch: monomeric (m/z 200 to 400), dimeric (m/z 400 to 650), trimeric (m/z 650 to 950) and tetrameric (m/z 950 to 1600), an essential factor for the production of carbon fibers, among other advanced composite of carbon. Relaxation time (T 1 ) studies permitted to observe two large areas: the aromatics and the mesophases. These results also showed that the heating time increases the mesophasic area. Also through direct and non-destructive 13 C NMR measurements, we obtained the content of aromatic and aliphatic carbons, as well as the degree of protonation of these carbons. Optical microscopy with polarized light showed the interfaces between the anisotropic and isotropic regions as well as the process of coalescence of mesophase. The results obtained by the other techniques corroborate the MALDI-TOF-MS and NMR results.

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“…Because DGE is reported in detail elsewhere [10,12], only a brief description is given here. The two monomer-rich pitch fractions (PFs) were produced by continuous DGE (see Fig.…”

Section: Dense-gas Extraction Apparatus and Proceduresmentioning

confidence: 99%

“…The conventional technique for analytical-scale pitch separation, gel permeation chromatography (GPC), suffers from a number of disadvantages, including poor peak resolution and the incomplete solubility of higher mol wt pitches in even aggressive mobile-phase solvents [1,[6][7]. Thies and co-workers [8][9][10] have recently developed a technique, known as dense-gas extraction (DGE), for separating pitches into fractions of relatively narrow mol wt. Such fractions can serve as standards for additional characterization work; in addition, we are investigating their large-scale production via DGE as "designer" pitches whose molecular compositions are tailored for a given, final carbon product application [11].…”

Section: Introductionmentioning

confidence: 99%

The Molecular Design of High-Performance Carbon Materials

Thies¹

2008

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Fractionation of pitches by molecular weight using continuous and semibatch dense-gas extraction

Cited by 29 publications

References 11 publications

Control of the Molecular Weight Distribution of Petroleum Pitches via Dense‐Gas Extraction

Control of the Molecular Weight Distribution of Petroleum Pitches via Dense‐Gas Extraction

Mesophase evolution in heat-treated solid petroleum pitches

The Molecular Design of High-Performance Carbon Materials

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