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Abstract

Introduction

At present, it is proved that the structure of organic matter of coals of different type of reductivity and the same degree of metamorphism is not the identical. At an equal degree of metamorphism reduced coals (type в) always contain a greater number of hydrogen and sulfur than low-reduced coals (type a). There are also differences in qualitative and quantitative content of functional groups comprising the organic mass of coal types a и в [1, 2]. The researchers attributed the formation of this coals to various factors: the expansion of plants which formed coals with the environment in the peat stage, with different geological and physical conditions during metamorphism, and so on [3- 5]. Methylation – a method that allows detailed examination of the original structure of the coals, to obtain biomarkers – substances that reflect the composition of plants which formed coals. In my master's paper discusses a method of methylation, invented recently – methylation in suite. The possibilities of this method have been studied only in lignites. We continued to work, applying this method to the study of coal. In carrying out termohymolysis has been studied the structure of Donbass reduced and law-reduced coals grades D and F from Gagarin and Trudovskaya mine. Pyrolysis with methylating agent – a new method in coal chemistry, which allows us to determine from what plant material formed the reduced and low-reduced coals.

1. Theme urgency

Analytical pyrolysis is widely used to study the structure and properties of various materials of organic origin. A decade ago, the traditional analytical pyrolysis was improved by heating the sample in the presence of tetramethylammoniumhydroxide, known as "pyrolysis methylating" or " termohymolysis " [6]. Methylating pyrolysis at the moment is one of the most powerful tools for the study of biopolymers, fossil lignins, humic substances, coal, asphaltenes, kerogen in the oil rock oil (bituminous) shale [7]. In contrast extraction, this method yields a largequantity of liquid products, as compared to conventional, "dry" versions of the low-temperature pyrolysis, prevents the rupture of chemical bonds. Termohimoliz at temperatures of 400 – 500 0 C is used for the detection of carboxylic acids and molecules adsorbed in sedimentary rocks. Tetramethylammonium, in this case prevents the destruction of oxygen-containing groups or forms with degradation products the simple and methyl esters [8].

2. Goal and tasks of the research

Purpose – a study of geochemical aspects of formation reduced and low-reduced coals of Donbass, the peculiarities of their composition and structure. As objects of study were selected two pairs of Donets reduced and low-reduced coal grades D and Zh.

3. Review of the literature

Bulgarian scientists was held termohymolysis lignites mined in the north-west of the Dacian Basin. The products of termohymolysis were analyzed with using gas-chromatography-mass spectroscopy. The sample was recognized gymnosperms. The content of angiosperms were low, represented by a very small number of types, also some herbs have been found. In addition, the palynomorphs without pollen were found. Contribution of paleoplants in organic matter of coal is proposed to evaluate from the relationship of the content of biomarkers, i.e., triterpenoids as indicators for the angiosperms and diterpenoids as conifer markers [17]. Data on the content of pollen confirmed the presence of herbaceous wetland plants that have contributed to the accumulation of peat in the swamp. The biomarker assemblage makes the Lom lignite unique in Bulgaria.

4. Preparative thermohymolysis

Preparative off line thermohymolysis analysis was carried out by the next way. Approximately 1-2 g of coal was placed in a ceramic boat and 2 ml TMAH (25% v/v in EtOH) were added dropwise. The moistened sample was left to stand overnight. It was then inserted into a Pyrex tube and heated at 400 °C (1 h), the thermohymolysis products being removed by a flow of N2 (100 ml/min) to trap of CHCL3 cooled in an ice bath (-15 °C). At the end of the treatment, the system was disconnected and the trapped products were combined and concentrated under reduced pressure (Fig. 1). Separation of the products obtained was performed by chromatography on a column. Stationary phase was a silica particle size of 0.2 – 0.5 mm. previously activated at 200 ° C for 2 hours. As the eluent used a mixture of hexane and diethyl ether (Et2O) in different percentages. Were collected following fractions: hexane (1), 10% Et2O in hexane (2), 20% Et2O in hexane (3), 50% Et2O in hexane (4). The first and second fractions were examined by gas chromatography-mass spectrometry HP 6890 with a capillary column with helium as an inert carrier gas (1.2 ml / min).
equipment for carrying out the thermohymolysis (анімація: 15 кадрів, 132 кілобайта)

Figure 1 – Equipment for carrying out the thermohymolysis

5. Analysis of results

The results of gravimetric analysis showed that the yield of products of the thermohymolysis affect the degree of metamorphism of coal and type of reduction (Fig. 2).

The yield of the thermohymolysis's products,% mass

Figure 2 – The yield of the thermohymolysis's products,% mass

A coals grade D give more liquid products, compared with the grade Zh. This is explained by their degree of metamorphism. Reduced coal produced more tar. Component analysis of the liquid products by chromatography on a plate showed a significant content of phenol (Fig. 3). Moreover, the amount of phenol varies within 40 – 50% the mass of all liquid products thermohymolysis (Fig. 3), i.e. absolute yield of phenol reaches 26% of the organic mass of the original sample. In the literature, however, are not found mention of such a high output of phenol from organic mass of coal.Usually, the amount of phenol is ranges from a few percent. [10]. The results of column chromatography are shown in Fig. 4. As can be seen from the data, coals of grade Zh give more quantity of the first and second fractions, which contain mainly low molecular weight, nonpolar organic compounds and phenols [12]. This is explained by structural features of the organic mass of coals middle stage of metamorphism [13].

Amount of phenol contained in LP of thermohymolysis,% mass

Figure 3 – Amount of phenol contained in LP of thermohymolysis,% mass

Results of chromatography of liquid products of thermohymolysis

Figure 4 – Results of chromatography of liquid products of thermohymolysis.

Conclusions

From the presented results we can see that the coal and coal type of reductivity affect to yield and composition of the products of the thepmohymolisys. The analysis of found geochemical indicators shows that the main differences in the structure of reduced and low-reduced coals related to the degree of decomposition of plant remains at the stage of diagenesis. In the master's work was considered the method of methylation, allowing detailed examination of the original structure of the coals and get biomarkers – substances that reflect the composition of plants that which formed the coal.

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