CHARACTERIZATION OF THE STRUCTURAL FEATURES OF OXIDIZED BEYPAZARI LIGNITE USING DECONVOLUTED SOLID STATE 13C NMR SPECTRA

The solid state ¹³C NMR method have been used to investigate the structural changes occurred in Beypazari lignite while oxidizing at 150°C in a dynamic air atmosphere. Least squares curve fitting techniques have been used to resolve the overlapping bands in the 0-220 ppm region of the 13_c NMR spectra. Measurements of the relative intensities of the functional groups observed in the oxidized coals were used to follow the progress of air oxidation. Oxidation reactions seemed to decrease the total intensities of both aliphatics and aromatics, though the reduction in aliphatics was more pronounced. The relative intensities of the total aliphatics decreased from 1.0 to 0.9 and 0.6 in the original and lignites oxidized for 12 and 312 hours, respectively. The relative intensities of Ar-C-C in the 130-148 ppm region for the same set of samples were 1.0, 0.9 and 0.8. The least-squares bands resolved in the carbonyl region were at 175 ppm and 190 ppm in the original lignite; at 180 ppm (carboxylic acids), 195 ppm (meta substituted ketones) 210 ppm (di orto substituted ketones) in the lignite oxidized for 12 hours and at 170 ppm (esters), 180 ppm, 200 ppm (aldehydes) and 210 ppm in the lignite oxidized for 312 hr. Carbonyl intensity increased from 1.0 in the original lignite to 2.3 and 3.3 in the oxidized lignites. The intensity of aromatic ethers increased from 1.0 in the original lignite to 1.9 and 1.6 for the oxidized samples. The mechanism of oxidation ether. Aldehydes are easily oxidized to carboxylic acids in the presence of air by the free radical formation of a peroxy acid. The carboxylic acid formed by disproportionation reactions between the peroxy acid and aldehydes might combine with phenols to produce esters as it was observed in the present work. The presence of high free radical concentration in the oxidation atmosphere probably caused to abstract hydrogen atoms from the aromatic structures thus degrading aromatics to produce hydroperoxides which acted later as it was described above. The gradual degradation of aromatic structures observed in the present study indicated that the oxidation reactions of the aromatic rings should less probable when compared to the oxidation of aliphatic structures.     

RELATION BETWEEN SWELLING OF LIGNITES AND THE CHARACTERISTICS OF SWELLING AGENTS

Relation between swelling ratio of lignites and lignite and solvent characteristics was developed using a third level factorial design with three variables; percent carbon content, particle size of the lignite and electron donor number of the solvent. The results indicate that particle size of the lignite does not affect the swelling ratio. While swelling ratio of the lignites decreases slightly with increasing carbon content of the lignites electron donor number of the solvent has a noticeable effect on the swelling ratio.     

RELATION BETWEEN SWELLING OF LIGNITES AND THE CHARACTERISTICS OF SWELLING AGENTS

Abstract

Relation between swelling ratio of lignites and lignite and solvent characteristics was developed using a third level factorial design with three variables; percent carbon content, particle size of the lignite and electron donor number of the solvent. The results indicate that particle size of the lignite does not affect the swelling ratio. While swelling ratio of the lignites decreases slightly with increasing carbon content of the lignites electron donor number of the solvent has a noticeable effect on the swelling ratio.     

EXAMINATION OF THE HYDROLIQUEFACTION BEHAVIOR OF CHINESE LIGNITE

ABSTRACT

In order to examine the hydroliquefaction behaviour of Chinese lignites a series of bench scale experiments with four lignites, obtained from Inner Mongolia and province Yunnan, in comparison with three foreign lignites or brown coals were performed under three sets of constant reaction conditions. The results show that Chinese lignites in general are comparable with other lignites and conversion can be precaculatad from analytical data with reasonable accuracy. The H/C-ratio of the organic coal matter is an appropriate characterization parameter for the evaluation of the hydroliquefaction behaviour of lignites. Chinese lignites Shengli and Xun-dian reveal higher hydrogenation reactivity than the other five lignite samples. Under conditions used a maximum conversion of more than 80% with oil yields of 60% are obtained. The influence of temperature, H-transfer potential, catalyst and residence time on the product distribution were also investigated in detail. Each lignite has specific sensivities for these factors. The experimental results provide interesting informations for a perspective on hydroliquefaction of these lignites.     

ASPHALT OXIDATION -- AH OVERVIEW INCLUDING A NEW MODELFOR OXIDATION PROPOSING THAT PHYSICOCHEMICAL FACTORS DOMINATE THE OXIDATION KINETICS

Oxidative aging of asphalt is the primary cause of asphalt hardening in pavements, thus contributing to various forms of pavement cracking. The major identifiable functional groups formed on oxidation at use temperatures are ketones and sulfoxides. Anhydrides are formed in significant amounts at the higher levels of oxidation, apparently not via carboxylic acids, but at specific aromatic bridgehead positions from the same precursors that form the ketones. Only trace amounts of carboxylic acids are formed. The sulfoxides formed have thermal sensitivity to subsequent decomposition, thus they reach a “steady state” concentration which is a function of temperature and oxygen diffusion rate. A differential infrared technique has been developed to quantitatively determine the major oxygen-containing functional groups present and/or formed on oxidation. The technique is based on the use of selective chemical reactions and selective solvents.     

芳香族化合物氧化反应研究的进展

氧化反应是对芳香族化合物进行官能团转化的重要方法之一。通过氧化反应可以由芳香族化合物得到酚、醛、酮、醌和羧酸等重要的有机中间体和精细化学品。综述了国内外关于芳香族化合物氧化反应的研究进展 ,分析了存在的问题并提出了解决问题的思路。     

EXAMINATION OF THE HYDROLIQUEFACTION BEHAVIOR OF CHINESE LIGNITE

In order to examine the hydroliquefaction behaviour of Chinese lignites a series of bench scale experiments with four lignites, obtained from Inner Mongolia and province Yunnan, in comparison with three foreign lignites or brown coals were performed under three sets of constant reaction conditions. The results show that Chinese lignites in general are comparable with other lignites and conversion can be precaculatad from analytical data with reasonable accuracy. The H/C-ratio of the organic coal matter is an appropriate characterization parameter for the evaluation of the hydroliquefaction behaviour of lignites. Chinese lignites Shengli and Xun-dian reveal higher hydrogenation reactivity than the other five lignite samples. Under conditions used a maximum conversion of more than 80% with oil yields of 60% are obtained. The influence of temperature, H-transfer potential, catalyst and residence time on the product distribution were also investigated in detail. Each lignite has specific sensivities for these factors. The experimental results provide interesting informations for a perspective on hydroliquefaction of these lignites.     

ADSORPTION OF ASPHALT FUNCTIONALITIES AND OXIDIZED ASPHALTS ON AGGREGATE SURFACES

ABSTRACT

The adsorption of asphalt functionalities and asphalt oxidized to different degrees on real and model aggregates has been investigated. The functionalities used were: nitrogen-base, phenolic, carboxylic acid, ester, ketone, sulfoxide, and polynuclear aromatic. Adsorption isotherms of these functionalities on porous silica showed different affinity rankings dependent upon concentration. The competitive affinity ranking of the asphalt functionalities on dried silica was obtained as phenylsulfoxide > qulnoline > phenol > benzoic acid > benzophenone > benzylbenzoate > pyrene. The sensitivity to moist silica surface of the four most strongly adsorbed compounds was: qulnoline > benzoic acid > phenol > phenylsulfoxide.

Asphalts oxidized to different degrees were adsorbed on different aggregates. On silica and alumina, the oxidized asphalts with viscosities of 32,000 and 126,000 poise were adsorbed less than AC-20. On limestone and sandstone, the adsorption of AC-20 and oxidized asphalts was concentration dependent; asphaltene adsorption followed the same trends. These adsorptions followed the Langrauir isotherm with monolayer coverage decreasing with increased oxidation.

functionalities such as ketones produced during oxidation are not as strong adsorbers as other functionalities; thus, changes in chemical composition during oxidation may result in substantial changes in asphalt adsorptive behavior. As oxidation increased in the different asphalts, the monolayer coverages of the asphalts decreased. Aggregate sensitivity to oxidation ranked in the order of silica > alumina > sandstone > limestone. Thus, the adsorptive behavior of an asphalt is a function of both the degree of oxidation and the aggregate onto which it is adsorbing.     

THERMAL REACTIVITIES OF SOME TURKISH LIGNITES

A DTA study has been made to investigate the thermal reactivities of five Turkish lignites (Elbistan, Ilgin, Karliova, Xangal, Yatagan) in an air atmosphere. The coal samples exhibited thermal reactivity at temperatures starting from 20 °C and continuing up to 671 °C. Endothermic peaks were observed at the lower end of the temperature range, the highest endothermic peak temperature being 146°C for Elbistan lignite. Exothermic peaks appeared at around 260, 360 and 600 °C. These temperatures are considered to signify the release and combustion of single benzene ring structures and combustion of condensed aromatic rings respectively. Corresponding stages are observed in the TGA traces. After correcting for differences in methodology, the overall heat effects measured by DTA are within greater than 90% of the calorific values of the coal samples determined by bomb calorimetry.     

THERMAL REACTIVITIES OF SOME TURKISH LIGNITES

Abstract

A DTA study has been made to investigate the thermal reactivities of five Turkish lignites (Elbistan, Ilgin, Karliova, Xangal, Yatagan) in an air atmosphere. The coal samples exhibited thermal reactivity at temperatures starting from 20 °C and continuing up to 671 °C. Endothermic peaks were observed at the lower end of the temperature range, the highest endothermic peak temperature being 146°C for Elbistan lignite. Exothermic peaks appeared at around 260, 360 and 600 °C. These temperatures are considered to signify the release and combustion of single benzene ring structures and combustion of condensed aromatic rings respectively. Corresponding stages are observed in the TGA traces. After correcting for differences in methodology, the overall heat effects measured by DTA are within greater than 90% of the calorific values of the coal samples determined by bomb calorimetry.     

A STUDY OF SULPHUR REMOVAL DURING LIGNITE HYDROLIQUEFACTION

ABSTRACT

Samples of Beypazari, Elbistan and Kangal lignites have been liquefied in hydrogen atmosphere in the presence of a solvent (tetralin) in a stainless steel reactor tube at 440^°C. Cobalt/motybdate and iron/sulfide were used as catalysts in all hydroliquefaction experiments. Semi-coke yield and total sulphur content reduction of the lignites were studied. It has been found that the use of a catalyst increased the semi-coke yield considerably. Sulphur content reduction varied depending on the type of catalysts and the lignite used in the experiment. The highest total sulphur content reduction was obtained using 5% iron sulphide catalyst with Elbistan lignite. It has also been observed that the reduction in the total sulphur content exhibits a maximum for increasing percentages of total sulphur in the subject lignites.     

PYROLYSIS OF SOME TURKISH LIGNITES BETWEEN 200 - 600°C

This study was undertaken to examine the effect of pyrolysis between 200-600°C on sulphur content, proximate and ultimate analyses of four (Seyitomer, Tuncbilck, Elbistan and Kangal) lignite samples. A decrease in semi-coke yield and an increase in tar and gas yields with increasing temperature were observed for all samples. Percent reduction of volatile matter was the same up to 400°C for the lignites. It has been observed that total sulphur contents were reduced significantly during carbonization. The highest sulphur reduction, 45%, was obtained with Elbistan lignite. By increasing temperature, hydrogen, carbon dioxide, methane and hydrogen sulphur yields increased notably but ethane and propane yields increased only slightly for all samples. In order to study effect of C, H and O contents of the original lignites on the yield and the distribution of the products, a linear regression analysis has been carried out and the model relations have been obtained. Experimental data and the model values from the relations have been compared. Yield values appear to be in good agreement with the model values for all samples.     

A STUDY OF SULPHUR REMOVAL DURING LIGNITE HYDROLIQUEFACTION

Samples of Beypazari, Elbistan and Kangal lignites have been liquefied in hydrogen atmosphere in the presence of a solvent (tetralin) in a stainless steel reactor tube at 440^°C. Cobalt/motybdate and iron/sulfide were used as catalysts in all hydroliquefaction experiments. Semi-coke yield and total sulphur content reduction of the lignites were studied. It has been found that the use of a catalyst increased the semi-coke yield considerably. Sulphur content reduction varied depending on the type of catalysts and the lignite used in the experiment. The highest total sulphur content reduction was obtained using 5% iron sulphide catalyst with Elbistan lignite. It has also been observed that the reduction in the total sulphur content exhibits a maximum for increasing percentages of total sulphur in the subject lignites.     

PYROLYSIS OF SOME TURKISH LIGNITES BETWEEN 200 - 600°C

Abstract

This study was undertaken to examine the effect of pyrolysis between 200-600°C on sulphur content, proximate and ultimate analyses of four (Seyitomer, Tuncbilck, Elbistan and Kangal) lignite samples. A decrease in semi-coke yield and an increase in tar and gas yields with increasing temperature were observed for all samples. Percent reduction of volatile matter was the same up to 400°C for the lignites. It has been observed that total sulphur contents were reduced significantly during carbonization. The highest sulphur reduction, 45%, was obtained with Elbistan lignite. By increasing temperature, hydrogen, carbon dioxide, methane and hydrogen sulphur yields increased notably but ethane and propane yields increased only slightly for all samples. In order to study effect of C, H and O contents of the original lignites on the yield and the distribution of the products, a linear regression analysis has been carried out and the model relations have been obtained. Experimental data and the model values from the relations have been compared. Yield values appear to be in good agreement with the model values for all samples.     

Structural Description of Polyaromatic Nucleus in Residue

The proton nuclear magnetic resonance spectroscopy （1H-NMR）, the synchronous fluorescence spectrometry （SFS） and the ruthenium ions catalyzed oxidation （RICO） method were used to determine the chemical structure of polyaromatic nucleus in Oman residue fractions. The results of 1H-NMR analyses showed that the average numbers of aromatic rings in the aromatics, resins and asphaltenes units were 3.2, 5.6 and 8.2, respectively. SFS was used to investigate the distribution of aromatic rings in residue fractions, the main distribution range of aromatic rings in aromatics, resins and asphaltenes were 3 4 rings, 3--5 rings and more than 5 rings, respectively. The aromatic network in residue fractions was oxidized to produce numerous carboxylic acids. The types and content of benzenepolycarboxylic acids, such as phthalic acid, benzenetricarboxylic acids, benzenetetracarboxylic acids, benzenepentacarboxylic acid and benzenehexacarboxylic acid disclosed the condensed types of aromatic nuclei in the core. The biphenyl fraction （BIPH）, the cata-condensed fraction （CATA）, the peri-condensed fraction （PERI） and the condensed index （BCI） were calculated based on the benzenepolycarboxylic acids formed. The results implied that there was less biphenyl type structures in all residue fractions. The aromatics fraction was almost composed of the cata-condensed type system, and the asphaltenes fraction was wholly composed of the peri-condensed type system, while in the resins fraction co-existed the two types, herein the peri-con- densed type was predominant over the cata-condensed type. Based on the analytical results obtained in the study, the components --aromatics, resins and asphaltenes -- were given the likely structural models.     

石蜡、微晶蜡非催化氧化的研究

在实验室对石蜡、微晶蜡非催化空气氧化进行了研究，考察了反应时间、反应温度和空气流量对其反应过程的影响及其差异。结果表明，异构烷烃含量高的微晶蜡比石蜡容易发生氧化的反应；石蜡及微晶蜡的氧化产物组成相似，是由脂肪酸、酯、铜等含氧化合物组成。     

不同芳烃种类对变压器油性能的影响

考察了不同芳烃种类对变压器油电气性能、抗氧化性能、溶解性能、抗析气性能和热物性的影响。结果表明：重芳烃、中芳烃、轻芳烃对变压器油电气性能影响由大到小的顺序为：重芳烃>中芳烃>轻芳烃;不同芳烃对基础油抗氧化性能和热物性影响不大,但中芳烃和重芳烃对抗氧剂感受性很差,而轻芳烃影响较小;溶解性能主要与芳烃含量有关,受芳烃种类影响较小,芳烃含量越高,溶解性能越好;芳烃具有良好的抗析气性,且中芳烃对基础油抗析气性的改善明显优于轻芳烃和重芳烃;在保证优异的电气性能和抗氧化性能前提下,变压器油中含适量的芳烃可改善变压器油的溶解性能和抗析气性能。     

EXTRACTION KINETICS OF COALS AT SUBCRITICAL AND SUPERCRITICAL CONDITIONS

ABSTRACT

The extraction kinetics of two lignites and one bituminous coal with benzene, toluene and pyridine were studied at both sub and supercritical conditions in a batch reactor equipped with a coal basket. The time-extract yield data of lignites at supercritical conditions could'nt be treated due to severe thermal decomposition and heating-up effects. The data for Zonguidak coal and those for subcritical extraction of Cizre lignite could be fitted into a first order rate equation with the rate constants changing 0·02-0·05 min^?1 range.     

EFFECT OF PHOTOOXIDATION ON MOLECULAR WEIGHT DISTRIBUTIONS OF CORBETT ASPHALT FRACTIONS BY GEL PERMEATION CHROMATOGRAPHY

ABSTRACT

Oxidation of asphalt is believed to be one of the major contributing factors to the failure of asphalt pavement. Due to molecular complexity, the oxidation mechanism of asphalt is complicated by interactions among the molecules of different types. To minimize the interactions, the asphalt sample was separated into saturates, naphthalene aromatics, polar aromatics, and asphaltenes. These Corbett fractions were then oxidized under ultraviolet irradiation. Gel permeation chromatography was used to analyze the molecular weight changes of the Corbett fractions during photooxidation. All Corbett fractions have shown significant increase in molecular weight. The oxidized saturates have the highest weight average molecular weight and the most complicated molecular size profiles among the oxidized Corbett fractions     

CHEMICAL CHARACTERISTICS OF SUPERCRITICAL TOLUENE EXTRACTS FROM TWO TURKISH LIGNITES

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.