Chemical and physical structural studies on two inertinite-rich lump coals.

Two Highveld inertinite-rich lump coals were utilized as feed coal samples in order to study their physical, chemical structural and petrographic variations during heat treatment in a packed-bed reactor unit combustor. The two feed lump coals were selected as it is claimed that Coal B converts at a slower rate in a commercial coal conversion process when compared to Coal A. The reason for this requires detailed investigation. Chemical structural variations were determined by proximate and coal char CO2 reactivity analysis. Physical structural variations were determined by FTIR, BET adsorption methods, XRD and 13C Solid state NMR analysis. Carbon particle type analysis was conducted to determine the petrographic constituents of the reactor generated samples, their maceral associations (microlithotype), and char morphology. This analysis was undertaken with the intention of tracking the carbon conversion and char formation and consumption behaviour of the two coal samples within the reactor. Proximate analysis revealed that Coal A released 10 % more of its volatile matter through the reactor compared to Coal B. Unburnt carbon in the ash bed zone was observed for both coal samples (Coal A and B), and it was attributed to incomplete carbon conversion. Coal char CO2 reactivity analysis showed that indeed Coal A is more reactive than Coal B. Qualitative FTIR analysis showed that both coals follow similar trends when exposed to high temperatures. Coal structural characterization revealed that Coal A has higher surface area when compared to Coal B. XRD analysis revealed that Coal A has less aromatic crystallites and lower Lc values compared to Coal B. It was observed that the coal structural properties of Coal A became more ordered and aligned at lower temperatures (289 0C), whereas Coal B starts at higher temperatures (693 0C). 13C Solid state NMR results showed that Coal B is more aromatic than Coal A implying that it is difficult to gasify/combust Coal B. Petrography analysis showed that Coal A has 34.6 vol % reactive macerals of which 78 % is from liptinite and vitrinite contents. Coal B has 53.6 vol % of reactive macerals of which 49 % was from liptinite and vitrinite, the other 51 % is from reactive semifusinite and inertodetrinite. The 49/51 split between reactive maceral value for Coal B may explain the lower reactivity compared to Coal A. Coal B appeared to produce more inert char particles, ran at higher temperatures in the ash bed because of its aromatic richness than Coal A. This was also attributed to the fact that Coal B has higher inertinite content than Coal A. The allocation of parent coal samples to “reactive” and “inert” macerals gave more in depth results that were able to show a possible reason behind reactivity difference occurring during the coal conversion process and support the structural analysis results obtained for these parent coal samples. The reactivity difference of these parent lump coal samples appears to be greatly influenced by the chemical reactions (structure) of these samples more than the kinetic reactions (pressure, temperature, reaction rates etc.) of these samples

Immobilized catalysts for alkene oxidation

Magister Scientiae - MScTertiary butyl substituted and unsubstituted Schiff base systems containing N,O donor ligands (Salicylaldimines) with aminotriethoxysilane tail were synthesized and complexed to Copper and Cobalt acetate. The ligands were characterized by FTIR and 1 HNMR Spectroscopy. The complexes were characterized by elemental analysis, ESI-Mass spectrometry and IR spectroscopy Mesoporous silica supports (SBA-15 and MCM-41) were synthesized and characterized by Xray diffraction, BET surface analysis and SEM. The tertiary butyl substituted and unsubstituted copper and cobalt salicylaldimine complexes were immobilized on amorphous (Davisil silica gel) and mesoporous supports (SBA-15 and MCM-41). Immobilized catalysts were characterized with Atomic Absorption Spectroscopy, X-ray diffraction, BET surface analysis, IR spectroscopy and SEM. Immobilized catalysts were tested for cyclohexene oxidation using molecular oxygen as cooxidant and hydrogen peroxide as oxidant. In this study the effect of metal, reaction time, nature of oxidant (hydrogen peroxide tertiary butyl hydroperoxide), substituents on the ligand and substrate concentration were investigated. Allylic products were obtained at relatively high cyclohexene conversion. In addition to the above, homogeneous systems were compared with heterogeneous analogues. The former were found to have better selectivity than their heterogeneous analogues although there appears to be no significant difference in the activity.South Afric

The petrographic determination of reactivity differences of two South African inertinite-rich lump coals

There is limited literature on the classification and characterization of chars generated from lump coals during synthesis gas production, especially from a South African perspective. Two inertinite-rich medium rank C Highveld lump coals (Coals A and B) were utilized to study their burning behaviour in a packed-bed reactor combustion unit. Seven sample increments were dissected per coal obtained from predefined zones within the reactor. Proximate analysis revealed that Coal A released 10% more of its volatile matter yield within the reactor zones when compared to Coal B. Petrographic analysis showed that Coal B had a higher content of reactive macerals when compared to Coal A. The reactive maceral content of Coal A was dominated by vitrinite and liptinite whereas for Coal B, reactive macerals were comprised of 49% vitrinite and liptinite and the other 51% is reactive semifusinite and reactive inertodetrinite. This difference leads to different reactivity behaviour when these coal samples were subjected to high temperatures. Coal B produced a greater proportion of inert chars, ran at higher temperatures in the hotter region of the reactor because of its aromatic richness thus leads to lower CO2 reactivity. This paper highlights the need for a detailed characterization of coals to fully determine their conversion performance; detailed coal petrography is one such tool that its value is frequently underplayed.http://dx.doi.org/10.1016/j.jaap.2011.10.008http://www.sciencedirect.com/science/article/pii/S016523701100183

Application of Organic Petrology and Raman Spectroscopy in Thermal Maturity Determination of the Karoo Basin (RSA) Shale Samples

An assessment performed using raman spectroscopy has found space in the black shales of the Cisuralian-age rocks of the Karoo Basin in South Africa, particularly those from the Guadalupian Ripon, Cisuralian Whitehill and Prince Albert Formations. It is used in conjunction with geochemical screening techniques such as organic petrology and programmed pyrolysis. In turn, the combination of these techniques is used for the assessment of the thermal maturity of the sedimentary organic matter from the perspective of hydrocarbon generation, retention, and expulsion. To provide further understanding of the black shales in the Cisuralian-age rocks of the Karoo Basin in South Africa, this study focuses on the characterization of samples from the KWV−01 borehole drilled in the southeastern Karoo Basin. In addition, the USA Devonian/Carboniferous Berea Sandstone project samples were included for comparison, and were used as a quality assurance measure. Organic petrology was utilized to assess the organic quality and thermal maturity of the black shales. The results obtained showed that the Karoo Basin shales are overmature, containing an abundance of solid bitumen, and this often characterizes a shale reservoir with moveable hydrocarbons (shale gas). The programmed pyrolysis analysis conducted on the black shales of the Karoo Basin yielded artifact results, as they were determined from a very low and poorly defined S2 peak. This indicated the shales to be overmature and categorized them to be of poor hydrocarbon generation potential. Raman spectroscopy was used to gain insights about the molecular structure of the black shales and to assess if this technique could be used as a complimentary tool to determine the thermal maturity of the shale samples. Raman parameters such as G–D1 Band separation, G and D1 band full width at half maximum (Gfwhm and D1fwhm) and G band position were successfully correlated with vitrinite reflectance (RoV), demonstrating a good potential for Raman spectroscopy to predict the thermal maturity of the shales. Overall, the study provides valuable information and knowledge concerning black shale sample characterization (particularly the thermal maturity and molecular structural characterization) in the Karoo Basin, South Africa

The impact of particle size and maceral segregation on char formation in a packed bed combustion unit

Highveld parent coal was crushed into three size fractions, namely: 5 mm–75 mm, 5 mm–53 mm, and 5–37.5 mm. The crushed samples were subjected as feed coals to heating in a packed-bed reactor to investigate the influence of particle size reduction on char formation and reactivity. Coal petrography was utilized to assess the maceral and char formation distribution of the feed coal samples and their packed-bed combustion unit’s products. The maceral distribution of the feed coal fractions differed from the typical run-of-mine Highveld coal petrographic composition; the smallest size fractions ( 53 mm and 37.5 mm) having the highest vitrinite content. Maceral distribution was further divided into total reactive maceral particles, total inert maceral particles, and total inertinite particles. The 53 mm and 37.5 mm feed coal samples had the highest total reactive maceral particle content. Inert char particles dominated in the packed-bed combustion unit samples due to high inertinite maceral group content of the Highveld coals. Unexpectedly, the 53 mm feed coal sample had higher content of total reactive maceral particles and lower content of total inert maceral particles; whereas the 37.5 mm feed coal sample had high content of reactive maceral particles and high content of total inert maceral particles. This variation in maceral group content lead to the 53 mm feed coal sample being more reactive (producing more devolatilized and porous chars and thus reacting faster with reactant gases) than the 37.5 mm feed coal sample. This was due to inert maceral particles restricting the 37.5 mm feed coal sample from fully softening and reacting with reactant gas. This was also this was attributed to variation in volatile propagation of the three particle sizes. This confirms that a feed coal with smaller particle sizes results in different reactivity, char formation, and better heat transfer during combustion than the feed coal with large particle size range. Another important factor that plays a role in combustion is maceral association; it was observed that maceral distribution has a great influence on the char formation and its reactivity more than coal particle size.http://www.journals.elsevier.com/fuel

Structural analysis of chars generated from South African inertinite coals in a pipe-reactor combustion unit

An inertinite-rich medium rank C bituminous South African coal was utilized to generate chars in a pipe-reactor combustion unit. This unit generates chars at atmospheric pressures and temperature was controlled with N2 to a maximum of 1250 °C. Chemical structural changes were investigated at different reaction zones identified in the pipe-reactor combustion unit. A combination of FTIR, XRD and Solid State NMR experiments were used to characterize the coal/char/ash fractions produced in the reactor. These techniques revealed that the coal structure becomes disordered in the drying zone as well as in the beginning of the pyrolysis zone in the reactor. As the temperature increases towards the base of the reactor the coal structure becomes more ordered and well aligned until char is formed and converted. Major structural changes were seen to occur in the drying to the pyrolysis zones. Structural changes within the molecular core were observed with FTIR and XRD results obtained from samples taken from the drying zone to the combustion zone. However, 13C CP/MAS and dipolar dephasing experiments were not able to corroborate these structural changes of the coal/char/ash fractions produced in the reactor occurring in the reduction and combustion zones.http://dx.doi.org/10.1016/j.fuproc.2010.09.00