Żelifikacja węgla ksylitowego w świetle badań petrograficznych i fizyczno-chemicznych

Przedstawiono wyniki badan petrograficznych i fizyczno-chemicznych wegla ksylitowego i jego popiolow. Wedlug wzrastającego stopnia zelifikacji tkanki drewna wyrozniono ksylit polkruchy, kruchy, slabo, średnio i silnie zzelifikowany oraz wegiel doplerytowy (zelowy). Odmiany te wytypowano na podstawie zroznicowanych cech fizycznych, ktore znajdują odbicie w zmiennym skladzie petrograficznym i chemicznym. Zroznicowanie petrograficzne polegalo na zastepowaniu tekstynitu ulminitem i zelinitem, natomiast chemiczne - na rosnącej ilości C i zmieniającej sie ilości grup funkcyjnych w tym wzrastającej zawartości grup, decydujących o aromatycznym charakterze struktury chemicznej wegla. Aromatyzacja wegla i związany z tym wzrost strukturalnego uporządkowania powstającej podstawowej jednostki strukturalnej jest funkcją wytworzenia sie w toku biochemicznej zelifikacji tzw. humin oraz związkow organomineralnych nazywanych doplerytem. Zmiany strukturalne potwierdzają wyniki badan absorpcji wegla w podczerwieni, rozpraszania ramanowskiego oraz innych badan chemicznych. Stwierdzono, ze: zelifikacja materialu roślinnego, odbywająca sie początkowo na drodze biochemicznej, a nastepnie chemicznej, ma cechy humifikacji i doplerytyzacji. Humifikacja jest procesem uweglenia, ktorego produktem jest zel organiczny zbudowany z humin, natomiast doplerytyzacja prowadzi do wytworzenia mieszaniny związkow organomineralnych typu huminianow. Wyroznienie obydwu kierunkow ma wyraźny aspekt chemizmu koncowych produktow, natomiast termin zelifikacja jest pojeciem wskazującym na fizykalną strone procesu uweglania. GELIFICATION OF XYLlTIC COAL IN THE LlGHT OF PETROGRAPIC AND PHYSICO-CHEMICAL STUDIES Gelification belongs to typical carbonification processes which takes place in the course of sedimentation of plant material and directly thereafter. Gelification of fossil wood may be analysed from the point of view of physical, chemical or biochemical alterations of its components, especially celulose and lignin as dominating ones. From the physical point of view, these complex processes end with origin of gel, which becomes transformed into vitrain at subsequent stages of carbonification. In analysing nature of final products from the chemical point of view it should be noted that gel may be huminous (purely organic) or dopplerite (organomineral) in character. Transformations proceeding on biochemical way (due to activity of microorganisms) give products similar in chemical composition. However, it should be remembered that the latter alterations are primarily connected with decay of plant component least resistant to peatbog conditions (i.e. carbohydrates and albumins) whereas those proceeding on purely chemical way primarily influence wood lignin. Identification of major phases in chemical decay of individual components of wood is highly important for the knowledge of the above processes. In order to give at least some approximate solution of this question for the case of lignin, samples of xylit coals were subjected to detailed petrographic and chemical studies by the methods of infrared and Raman spectroscopy. Samples of xylit coals were ordered according to increasing degree of gelification. Microscopic petrographic studies in thin sections and determinations of content of ash organically related la coal matter showed that xylit coal samples from Upper Oligocene layer in the Glogow region represent a series of so-called doppleritization of xylits and those from deposit at Legnica (Upper Miocene) - the gelificalion type named as humification. Xylits varying in advancement of gelification were compared with semi-brittle and brittle ungelified ones. Spectrophotometric spectra of the xylits in basic infrared range and oscillatory Raman spectra were studied in detail. The obtained results were compared with estimations of content of COOH group in coal and chemical composition of ash (Table 3). The infrared spectrum range from 1700 to 1500 cm -1 and Raman spectra of coal appeared to be the key for solving the above problem. The obtained results made it possible to establish succession of individual stages in transformation of lignin, reflected by increasing degree of gelification of xylits. Transformation of lignin into humus matter was found to be primarily connected with elimination of ether bonds between its radicals, separation of metoxyl groups from the radicals and formation of free phenol groups. The presence of the latter may be the reason of secondary condensation of the radicals modified in this way. At the same time, aliphatic ketone fragments are subjected to advanced structural changes which involve enolization of ketone patterns. The enolization may be connected with origin of. soluble alkaline metal salts which undergo decay after condensation and formation of chinons. Because of weakly oxidating conditions, chinons become transformed into reactive ketonoacids in result of break up of a part of rings. Transformations of that type take place in weakly alkaline or neutral environment which changes into the acid along with advancement in gelification. Under the influence of some geological agents and time, acids change into humins. A change of the environment into alkaline results in chemical reactions between organic acids and inorganic alkalies and their salts. This leads to origin of a mixture of so-called huminians (Ca, Mg, K, Fe and others), which are the major components of dopplerite coal. The results of the studies confirmed duality of final products of wood gelification process. This fully justifies differentiation of the following trends in physical process of gelification: humification, leading to origin of humins, and doppieritization, the final products of which at the transformation stage is organomineral gel (dopplerit).