CHARACTERIZATION OF COAL CHARS FROM A FLASH PYROLYSIS PROCESS BY CROSS POLARIZATION/MAGIC ANGLE SPINNING 13C NMR

Chars from the Illinois Springfield (No. 5) Coal are prepared by flash pyrolysis at progressively higher charring temperatures. The results of a study of these chars by ¹³C NMR with CP/MAS indicate that the initial stage of heating (300^°C) produces a char with aromatic carbon fraction (f_ar) of 68%, and successive heating gives chars with f_ar of 70% (400^°C), 73% (500^°C), 89% (600^°C), 95% (700^°C), and 96% (800^°C). However, the actual amount of aromatic and aliphatic carbon in the char can be calculated by using the NMR measurements, the organic carbon content of the char, and the weight of the char. The calculated values show that the amount of aromatic carbon in char remains relatively constant at each temperature, but the amount of aliphatic carbon in char is reduced during higher temperature charring. At 600^°C, both a large reduction of the aliphatic carbon content and a maximum weight loss occur. Evidently, the aliphatic-bond carbon in coal is the principal source of volatiles derived from coal. The apparent increase in aromaticity (f_ar) of the char heated to progressively higher temperatures is due to the loss of aliphatic-bond moieties and reduction in volume of materials.     

RAPID PYROLYSIS OF EASTERN CANADIAN COALS BY FREE FALL REACTORS

Abstract

The effect of temperature was investigated on the rapid pyrolysis of Prince, Lingan and No. 26 coals in the temperature range of 525^° to 750^°C using a 600 cm high stainless-steel free fall reactor at atmospheric pressure.

The yields of char, condensibles and gaseous products were determined at 25^°C intervals. Gaseous products were analysed for H₂, CO, CO₂, CH₄ and C₂+.

Volatile product (condensible and gas) yields exceeded the volatile product in the A.S.T.M. methods at and above 700^°C.

Some experiments using Prince coal were repeated at reduced pressure (50 mm mercury) in both the 600 cm height stainless-steel and a 140 cm height quartz reactor in order to find out the effect of pressure and retention time.

The experimental results indicated that the condensable yield was higher at the lower pressure and at the shorter retention time. The effect of retention time was far more pronounced.     

STUDY OF STRUCTURAL FEATURE OF PEAT,LIGNITE AND HUMIC ACID BY SOLID STATEl3C NMR SPECTROSCOPY

Abstract

Four low rank coals (peat and lignite) and their derived humic acids have been investigated by the^l3C CP/MAS/TOSS NMR technique. The NMR analysis indicates that the peat contains a significant amount of unaltered plant components including cellulose, hemicellulose, lignin, waxes, and resins.

Variable contact time and dipolar dephasing experiments were performed on each sample. The data from above experiments, together with normal CP/MAS integration over selected chemical shift range, were used to derive 12 parameters of carbon skeletal structure including the aromaticity.From the ratio of aromatic bridgehead carbons, f_a ^cp, to the aromatic peripheral carbons, f^cpxBp as measured by NMR, the aromatic cluster size may be estimated for each coal.     

13C-N.M.R. STUDIES OF A FLASH PYROLYSIS TAR AND A SUPERCRITICAL GAS EXTRACT USING MODERN PULSE SEQUENCES

ABSTRACT

The oil and the asphaltene obtained from a flash pyrolysis tar of an Australian sub-bituminous coal and the oil and asphaltene from a supercritical gas extract of an Australian bituminous coal were studied by ¹³;c-n.m.r. apectroscopy using modern pulse sequences which distinguish between primary (CH₃), secondary (CH₂), tertiary )CH( and quaternary (C) carbons. The oil from the flash pyrolysis tar was further separated into three fractions by elution chromatography and these were also studied. All the samples studied contained considerable amounts of long unsubstituted aliphatic chains. In the flash pyrolysis tar, a sizeable proportion of the long chains had a CH = CH₂ end group pertaining to both 1-alkenea and those chains attached to aromatic rings (w-aryl-1-alkenes), but this was much less in the supercritical gas extract. From the quaternary and tertiary carbon subspectra, it appears that the division of the aromatic carbon signal at 129-130 ppm between aromatic CH and C carbons is not valid for polar fractions of coal liquids. Though these pulse sequences are very useful for obtaining information on well resolved signals, broad featureless signals often found in coal liquids pose considerable problems.     

INVESTIGATION INTO THE IGNITION PROPERTY OF COAL UNDER PRESSURE

ABSTRACT

The ignition property (ignition temperature and combustion time) of coals and chars were determined at the heating rate of 7.5°/min and under pressure. Different factors have been investigated, which include particle size, total pressure, partial pressure of oxygen, macerals, preparation method and catalyst. The results show that: the ignition temperature decrease with decreasing particle size and increasing total pressure or partial pressure of oxygen; coal char prepared by lower heating rate has higher ignition temperature than that by higher heating rate; vitrinite has higher ignition temperature than fusinite, but after carbonization the situation turns opposite; addition of K⁺; and Na+ to anthracite or coal char can decrease ignition temperature and K⁺; is more effective than Na⁺;.     

VARIATION IN THE CHEMICAL NATURE OF ASPHALTENES WITH THE PROCESS,THE COAL AND THE REACTION CONDITIONS

ABSTRACT

Average structure data for twelve asphaltenes are reported, based on ¹³C- and H- n.m.r. spectroscopy combined with elemental, molecular weight and functional group analyses. The asphaltenes were from supercritical gas extraction, flash pyrolysis and hydrogenation of a brown and a bituminous coal. The effect of the reaction temperature and, for hydrogenation, the catalyst and solvent on the nature of the asphaltene produced was studied. The asphaltene obtained from supercritical gas extraction of the brown coal at 350°C was the least aromatic (f_a = 0.44) with the highest H/C atomic ratio (1.16) and probably consists mainly of single ring aromatlcs with about half of the aromatic sites substituted. A significant proportion of the carbon in this asphaltene is in long alkyl chains and the hydroxyl content is high. Whereas, the asphaltenes produced by hydrogenatlon of the bituminous coal at 450°C were far more aromatic with more highly condensed but less substituted aromatic ring systems and few, if any, long alkyl chains, together with a lower hydroxyl content. The asphaltenes obtained from the brown coal are less aromatic with less condensed aromatic ring systems but a higher degree of aromatic substitution than those produced from the bituminous coal under the same conditions. The asphaltenes formed at 450°C had lower H/C atomic ratios, molecular weights and degree of aromatic substitution, but higher aromaticities Ohan those produced at 35O°C or 400°C under like processing conditions. The asphaltene produced in the presence of both stannous chloride catalyst and tetralin was less aromatic than when either of these species was absent.     

RESIDUUM HYDROTREATING APPLICATION OF IH AND QUANTITATIVE CARBON-13 NMR SPECTROSCOPY FOR THE STUDY OF HYDROTREATED PRODUCTS

ABSTRACT

Bai-Hassan reduced crude (350^°C + ) was hydrotreated in fixed bed reactor with commercial Ni-Mo-alumina catalyst. H and quantitative C NMR are used to derive statistical average structure parameters of feedstock and hydrotreated products. The main aromatic hydrocarbons (of type C_ar,H + C_ar,CH₃ + C_ar,n + C_ar,I) of hydrotreated products decreases by temperature, (at mild conditions) particularly at lower space velocity. The severe operating conditions increases the main aromatic hydrocarbons. An approximate inverse correlation is observed between the behaviour of saturated hydrocarbons and the aromatics of type C_ar,H + C_ar,CH₃ + C_ar,n + C_ar,I during hydrotreating process. Higher temperatures show an increase in the percentage of alkyl aromatics of type C_ar,alkFurthermore, the severe operating conditions promotes the formation of the alkyl aromatics with H_α(ArCH₃) while it decreases the alkyl aromatic having H₈ and H₈ The kinetic study of napthenes formation indicates that this reactin is well correlated with a first-order kinetics. The apparent activation energy lpar;E rpar;, enthalpy lpar;? H rpar;and entropy lpar;? s?lpar; of activation are 23.630 KJ mol 18.390 kJ mol ^-1 and -225.95 J mol^-1 k^-1 respectively.     

CHEMICAL CHARACTERISTICS OF SUPERCRITICAL TOLUENE EXTRACTS FROM TWO TURKISH LIGNITES

ABSTRACT

Samples from two major deposits of Turkish lignites were subjected to supercritical toluene extraction at 325°C and 14.1 MPa in an autoclave. The resultant extracts were separated into pre-asphaltene, asphaltene, saturates, aromatics and resin fractions by column chromatography. The fractions were characterized by ¹H-NMR, ¹³C-NMR, IR. and elemental analysis in order to compare the chemical composition of extracis from the two coal samples. The results show that the extracts from the Tungbiiek (T-coal) deposits contain aliphatic constituent which is composed of mostly long chain unbranched alkyl compounds while the extracts from the Soma Mcrkeg (S-coal) deposits contain a significant amount of branched paraffinic compounds. The resin fractions from both samples were found to contain a significant amount of single ring aromatic compounds.     

KINETICS OF CORN COB CHAR GASIFICATION IN CARBON DIOXIDE

ABSTRACT

The Reactivity of corn cob char in CO₂ has been studied on a thermogravimetric balance to develop a rate equation for the design of biomass gasifiers operating on corn cob char. Experiments in the range of 650-1000^°C were conducted with cylindrical shaped pellets of 1 cm diameter having L/D=l. The average porosity of the pellets was 0.5. It was observed that the rate of the CO₂/char reaction decreased with increase in temperature from 650-750^°C and then increased with temperature upto 1000^°C.

The data obtained at temperatures 750^°C and above has been used to determine a rate equation for char gasification. It has been found that the reaction proceeds according to the Sharp Interface Model (SIM) with a first order chemical reaction as the rate controlling step. The activation energy is found to be 40 Kcal/mole with frequency factor being 1.2 × 10⁷ mm/sec. Analysis of the data obtained for the decreasing reaction rate regime (650-750^°C) indicates that the change in the ash structure result in this kind of behavior.     

The inhibitory effect of black pepper on formation of heterocyclic aromatic amines in high-fat meatball

The effect of black pepper on the formation of heterocyclic aromatic amines (HCAs) in high-fat meatball fried at three different frying temperatures (175 °C, 200 °C, and 225 °C) was investigated. The fried samples were analyzed for five HCAs, including 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), and 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP). In control group meatballs without black pepper, the total HCAs amount increased in parallel with the frying temperature increased. The highest total HCA amount was found 37.81 ng/g in control group meatballs fried at 225 °C, 31.80 ng/g of which belonged to PhIP accounting.  The reduction of black pepper on PhIP compound was 100%. On the perspective of total HCA amount, black pepper has an inhibitory effect (ranging from about 12 to 100%). MeIQx was not detected in any of chops samples.     

SOLID STATE 13C NMR STUDY OF THERMALLY UPGRADED LOW RANK COALS

ABSTRACT

The results of solid-state ¹³C NMR study aimed at evaluating the chemical changes and extent of upgrading achieved in the thermal treatment of two western Canadian low rank coals are discussed. The coals were thermally treated at varying temperatures (200 - 500°C) using different process media (nitrogen, steam and products of combustion)

Apparent aromaticity of the two coals was increased after the thermal treatment and increased with treatment temperature. Significant chemical changes, such as loss of the protonated aromatic carbons, quaternary carbons in alkylated rings and aliphatic ethers, were observed at 400°C and above. Condensation and polymerization of the chemical components were also evident. The effect of process medium was found to depend on the coal feed and the treatment temperature.     

EFFECTS OF COAL SURFACE CHARGE ON THE ADSORPTION AND GASIFICATION ACTIVITIES OF CALCIUM AND POTASSIUM

ABSTRACT

The electrokinetic properties of lignite, subbituminous and bituminous coal particles and their demineralized derivatives have been measured as a function of pH. Compared to the raw coals, demineTalization generally increased the net negative surface charge densities on the coals. Calcium or potassium adsorption (by ion-exchange) onto the demineralized coals was strongly dependent on pH and the surface charge properties of the coals. Metals uptake was very low (0,1-0.4% wt.) in strongly acidic media (～pHl) but increased dramatically as the net negative charge on the coals was increased by increasing the pHs of the coal suspensions to pH 6 or 10. The reactivities of the calcium- ot potassium-loaded chars in carbon dioxide at 800^°C were similarly dependent upon the pHs at which the catalysts were ion-exchanged onto the coals. For the calcium-containing chars, the reactivities increased in the order: pH 6 > “pH 10 > pH 1 while the variation of the gasification rates with potassium loading pH was: pH 6 ～ pH 10 ? pH I. These findings are attributed to differences in the extent of electrostatic interaction between the calcium or potassium ions and the charged coal surface during catalyst loading from solution.     

DEVELOPMENT OF HIGH-PERFORMANCE HEAVY OIL HYDROCRACK1NG CATALYSTS: CHARACTERIZATION OF ATMOSPHERIC RESIDUE FEED

ABSTRACT

The characterization results of the atmospheric residue obtained from Saudi Arabian Light crude oil show the complex nature and composition of this material. The distillation results showed that about 50 percent of Arab Light crude is the atmospheric residue. The elemental analysis of the residue showed that high amount of carbon, sulfur and nitrogen is present along with heavy metals such as nickel and vanadium. The determination of hydrocarbon types by HPLC exhibited that 12% polars and 27% aromatics are present along with 6% asphaltenes. Nuclear magnetic resonance study conducted on the residue and its fraction provides a detailed composition in terms of aliphatic and aromatic nature of the residue and its fractions. The results showed that the residue contains 21% aromatic and 79% aliphatic carbon. The aliphatic carbon is present in saturates and as side chains of aromatic and polar molecules whereas the aromatic carbons are those in the ring structure. Asphaltenes separated from the residue were characterized for their different properties to understand its complexity. The use of electron spin resonance spectroscopy provides determination of the free radicals present in the residue. Asphaltenes were analyzed using the state-of-the-art high temperature high pressure electron spin resonance (ESR) technique in the temperature range 20 to 625 °C and at 30 and 50 bar hydrogen pressure. The ESR determination at 30 bar shows that me pressure was not enough to prevent the boiling of the asphaltene and thus a decrease in the spin concentration was observed beyond 350 °C temperature. The data at 50 bar pressure showed the adequacy of this pressure for ESR measurement. The PMRTA analysis of asphaltene showed a decrease in residual hydrogen with increasing temperature.     

COPROCESSING OF COAL WITH HEAVY PETROLEUM CRUDES AND RESIDUA

ABSTRACT

This work investigates the coprocessing of coal in six different heavy petroleum crudes and residua. Coprocessing reactions of coal and the petroleum solvents are performed under three sets of constant reaction conditions, yielding informative comparative data for processing applications. Definitive comparisons of coal reactivity and solvolysis in the petroleum solvents have been obtained using solvent fractionation which provides a measure of the degree of upgrading achieved by the liquefied coal. Regressive reactions and low coal conversions are observed in coprocessing reactions in N₂ at 400^°C. Higher conversions and a reduction in regressive reactions are observed in H₂ at 400^°C. Catalytic hydrotreatment and higher temperature, 425^°C, result in increased coal conversion and a net production of pentane soluble materials. The amount of product fractions obtained from the upgrading of the coal alone is calculated. The effect of reaction temperature using different solvents and reaction conditions on the product slate is also examined.     

Calculations of heats of formation for nitroaromatics with PM3 and MM2

Abstract

We have attempted to calculate heats of formation (Δ H _f °) for various aromatic nitro compounds with the semi-empirical molecular orbital theory and the molecular mechanics. As the results we may say that PM3, a semi-empirical MO method, and MM2, molecular mechanics, can estimate Δ H _f ° of energetic materials with accuracy enough to use Δ H_f° for energy hazards prediction. In case of aromatic polynitro compounds, both methods may be able to calculate accurate Δ H_f°.     

Correlation between main structural group parameters of crude oils of the Volga–Urals oil and gas basin by <Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR data

In Volga?Urals crude oils, an increase in the aromatics content is characterized by a rapid increase in the relative amount of polysubstituted aromatic rings and a generally lower proportion of bi- and polycyclic aromatics, unlike the case of Western Siberia oils. The difference between the oil and gas basins is most probably due to the special features of the source organic matter of the oils. The regional features of the Volga?Urals oils are a relatively weak relationship between the concentrations of mono- and bi- + polycyclic aromatics and a relatively close relation of Σn-Alk to typically uninformative parameter Hβ, which indicate a high uniformity of the composition of saturated cyclic compounds and moieties of hybrid naphthenoaromatic components. In addition, the assumption that (H/C)_ar/(H/C)_al = const does not hold for Volga?Urals oils. However, the relationships between the main parameters describing total aromaticity (primarily, C_ar, H_ar) and n-alkyl structures (primarily, Σn-Alk) are identical for oils from both the basins. The total number of relationships that can be universal for oils from different oil-and-gas basins is fifteen. To estimate C_ar from ¹H NMR data for Volga?Urals crude oils, a linear dependence on the two variables H_ar and H_α should be used. The expressions obtained to relate the structural-group parameters have made it possible to reveal a number of oils that stands out among the others.     

HYDROLIQUEFACTION OF TEXAS LIGNITE IN COAL- AND PETROLEUM-DERIVED SLURRY OILS

ABSTRACT

Hydroliquefaction of Texas lignite (68.5%. C daf) was conducted in a batch autoclave under hydrogen in a coal–derived slurry oil at 90 bar initial pressure for temperatures of 380–460^° C and residence time of 15–60 minutes, or a vacuum distillate from petroleum at 435^° C for 60 minutes and initial H₂–pressure of 60–150 bar, or a vacuum residue from the same petroleum at 435 and 460^° C for 60 minutes and initial H₂–pressure of 90–150 bar or tetralin at 435^°C, 60 minutes and 90 bar initial H₂–pressure. Red mud plus sodium sulfide were added as a catalyst for all experiments. Lignite conversion ranged from 50 to 83%. The products were separated into gases, residue, asphaltenes, oils B,P. above 200^° C, oils B.P. below 200^° C. Total liquid products from coal reached 57% in coal-derived slurry-oil, 56% in vacuum distillate and 64% in vacuum residue at optimum conditions with 32% of product oil B.P. below 200^° C in vacuum distillate and 24% in vacuum residue. When coprocessing lignite with vacuum residue at 120 bar initial pressure, 435^°C and 60 minutes residence time the total mass balance presented an oil yield of 73%. with 32% boiling below 200^°C.     

Modeling of oil generation by Domanik carbonaceous shale

Experiments on artificial maturation of carbonaceous rock of the Domanik age in an autoclave in the presence of water at temperatures of 250, 275, 300 and 325°C have been performed. It has been shown that a significant amount of soluble organic matter (OM) is produced from insoluble OM under these conditions. Changes have been observed in both the biomarker composition of the bitumen and the Rock-Eval OM maturity parameters characteristic of natural catagenesis. By the solid-state ¹³C NMR technique, it has been shown that the amount of aliphatic units decreases and that of aromatic units increases in residual kerogen. Study the product composition of the pyrolysis of residual kerogen has revealed that the relative amount of precursors of n-alkyl structures increases as compared with low-molecular-weight aromatic and thiophenic structures.     

Influence of ZnO and P2O5 Content on Modified HZSM-5 on Aromatization of FCC Gasoline

Abstract

Catalytic properties of different content of ZnO and P₂O₅ supported on HZSM-5 zeolites were studied in the conversion of FCC gasoline (75°C–120°C) into aromatic hydrocarbons with a temperature of 430°C, a liquid hourly space velocity of 1.0 hr^?1, and a pressure of 0.1 MPa. In the reaction, when the contents of ZnO and P₂O₅ are 2% and 4%, respectively, Zn-P/HZSM-5 showed the highest selectivity and activity to aromatic hydrocarbons and conversion of olefins. The content of aromatics in the liquid product and the yield of aromatics reached as high as 94.53%, 68.87%, and 51.74%, respectively.     

Determination of the functional groups and the melting point of iraqi asphaltenes

A qualitative analysis study of n-C5 asphaltene of Iraqi crude oil from (Al-Dura, Kirkuk and Basra) oil fields was done using Fourier transform infrared spectroscopy (FT-IR). The melting points of the three oil derived asphaltenes were determined using Hot stage polarizing microscope at 180?°C for Al-Dura, 125?°C for Kirkuk and 140?°C for Basra asphaltenes. The FTIR spectrum shows an aromatic behavior of the asphaltene samples at a wavelength of 3049?cm^?1 and aliphatic chains were found at wavelengths 2924?cm^?1.