Grażyna Gryglewicz

Preparation of polyol esters based on vegetable and animal fats

The possibility of using some natural fats: rapeseed oil, olive oil and lard, as starting material for the preparation of neopentyl glycol (NPG) and trimethylol propane (TMP) esters is reported. The syntheses of final products were performed by alcoholysis of fatty acid methyl esters, obtained from natural fats studied, with the appropriate polyhydric alcohol using calcium methoxide as a catalyst. The basic physicochemical properties of the NPG and TMP esters synthesized were the following: viscosity at 40 degrees C in the range of 13.5-37.6 cSt, pour point between -10.5 and -17.5 degrees C and very high viscosity indices, higher than 200. Generally, the esters of neopentyl alcohols were characterized by higher stability in thermo-oxidative conditions in comparison to native triglycerides. Due to the low content of polyunsaturated acids, the olive oil based esters showed the highest thermo-oxidative resistance. Also, methyl esters of fatty acids of lard would constitute a good raw material for the synthesis of lubricating oils, provided that their saturated acids content was lowered. This permits synthesis of NPG and TMP esters with a lower pour point (below -10 degrees C) than natural lard (+33 degrees C).

The behaviour of sulphur forms during pyrolysis of low-rank coal

Abstract Flame coal was pyrolysed up to 1700°C in a fixed bed in an atmosphere of the evolved gases. Sequential changes in the sulphur form distribution were quantitatively determined. A marked enrichment in organic sulphur was observed between 330 and 600°C when conversion of pyrite into ferrous sulphide occurred. SEM with X-ray microanalysis showed that the reduction of pyrite followed the changes in its morphology, from massive to dendritic structure. Above 1000°C, ferrous sulphide began to lose sulphur. The organically combined sulphur appeared to be stable at 1700°C. A sulphur removal of 89.8% was achieved at this temperature. The effects of the reaction of the coal matrix with the sulphur from pyrite decomposition and the presence of alkali minerals in the original coal on the efficiency of its desulphurization during pyrolysis were also considered.

Effectiveness of high temperature pyrolysis in sulfur removal from coal

Abstract A series of Polish hard coals of different rank that contained sulfur in the quantity from 0.37 to 4.90 wt% was investigated in this study. The coals were subjected to pyrolysis at 1000°C in an atmosphere of the gases evolved during the pyrolysis process. Results have shown a decreasing trend in the degree of sulfur removal by high temperature pyrolysis with increasing coal rank. The effectiveness of pyrolysis in sulfur removal appears to be related to the proportion of the non-thiophenic sulfur to the total organic sulfur in the coal. These are linear correlations between the total sulfur content in the coke and total, pyritic and organic sulfur contents in the initial coal.

Sulfur transformations during pyrolysis of a high sulfur Polish coking coal

Abstract A coking coal containing 4.9 wt%, db, of sulfur was subjected to pyrolysis at 330–1700°C in an atmosphere of evolved gases. The changes in the forms of sulfur were determined by wet chemical analysis. Scanning electron microscopy (SEM) combined with X-ray microanalysis were used to monitor the reduction of pyrite during coal pyrolysis and the retention of sulfur by the alkali constituents of the coal mineral matter. It was found that between 360 and 700°C the conversion of pyrite to ferrous sulfide occurred. This was accompanied by a high accumulation of organic sulfur in the char. Calcite and siderite present in the mineral matter of the coal were responsible for a further increase in sulfide sulfur. Spherical agglomerates composed of calcium and iron sulfides were detected. Above 1000°C sulfur re-enrichment on the surface of ferrous sulfide particles was observed. Pyrolysis conducted at 1700°C did not remove the sulfide sulfur completely. Organic sulfur was also present in a significant amount. The roles of alkali components and an environment rich in volatile sulfur compounds in sulfur retention during coal pyrolysis are discussed.

Development of mesoporosity during phosphoric acid activation of wood in steam atmosphere.

Oak and birch were used as precursors to produce the activated carbons (ACs) with well-developed mesoporosity by phosphoric acid-promoted activation in a steam atmosphere. The effect of experimental variables such as the amount of activating agent, the soaking time and the type of wood on the development of porous structure upon heating at 480 degrees C was investigated. The materials were characterized by N2 adsorption at 77K, mercury porosimetry and elemental analysis. It was demonstrated that increasing impregnation ratio favors the development of micropores and small mesopores of 2-5nm, whereas the soaking time promotes the creation of large mesopores, between 10 and 50nm. Compared to birch, the oak activation using phosphoric acid in the same conditions gives ACs with lower mesopore volume and higher contribution of small mesopores that reflects the differences between both precursors in their biopolymer composition. The presence of steam in the H3PO4 activation process compared to nitrogen facilitates the development of mesoporosity to much higher extent for the birch than that of oak. The ACs prepared in this work show the BET surface area ranging from 800 to 2250m2g(-1), the total pore volume of 0.35-2.04cm3g(-1) with mesopore fraction between 0.06 and 0.68.

Determination of sulfur groups in pyrolysed low-rank coal by atmospheric-pressure t.p.r.

Abstract Atmospheric-pressure temperature-programmed reduction (t.p.r.) was used to follow in pyrolysed sub-bituminous coal the changes in amount of pyrite and in organic sulfur groups as a function of temperature. At higher pyrolysis temperatures, pyrite and aliphatic and mixed aliphatic-aromatic sulfides disappeared systematically and more complex sulfur compounds such as aromatic sulfides and simple thiophenic structures were formed.

A study of the reductive pyrolysis behaviour of sulphur model compounds

Abstract The difficulties inherent in the direct determination of sulphur functionalities in complex solid matrices by various techniques often make the need for reference compounds indispensable. One of the pyrolysis techniques used for sulphur determination is atmospheric pressure–temperature programmed reduction (AP-TPR). Experiments on sulphur model compounds have served successfully as a reference for both the temperature region in which the reduction or hydrogenation occurs and the efficiency of the reduction reaction. In this study, the pyrolysis behaviour of several organic and inorganic sulphur model compounds is investigated by AP-TPR using a mass spectrometer detector interfaced with the pyrolysis reactor (AP-TPR-MS). This technique permits a more complete description of the competitive and successive reactions that are occurring during the pyrolysis of the model compounds, providing new information regarding the reduction efficiency of oxidised and non-oxidised sulphur compounds.

Preparation and characterization of spherical activated carbons from oil agglomerated bituminous coals for removing organic impurities from water

A new and simple method of producing of spherical activated carbons (SACs) from different bituminous coals, i.e., gas coal, gas-coking coal and orthocoking coal, is presented. Coal agglomerates of spherical shape obtained by oil agglomeration using rapeseed oil and linseed oil, were subjected to carbonization and activation with steam at 850 8C. The SACs prepared from gas-coking coal (hvAb) agglomerates were characterized by the best developed porous structure with surface area SBET 23 of about 800 m / g and pore volume of 0.40 cm / g. The adsorption capacity of the produced SACs was determined in terms of substituted phenolic compounds. The adsorption of 2-chlorophenol (OCP), 4-chlorophenol (PCP) and 4-nitrophenol (PNP) from aqueous solutions was studied under a static conditions on the SAC prepared from gas-coking coal agglomerated using rapeseed oil. At high concentrations of the solute the adsorption behavior of OCP was found to be different in comparison to PCP and PNP. The adsorption of the two last phenolic compounds on the selected SAC is very well described by Langmuir adsorption model. For OCP a two-stepped adsorption isotherm was obtained. The Langmuir isotherm equation fits very well only for the first stage of the OCP adsorption.  2002 Elsevier Science Ltd. All rights reserved.

Rank dependence of organic sulfur functionalities in coal

Organic sulfur functionalities were characterized and quantified by atmospheric-pressure temperature-programmed reduction (AP-TPR). Nine coals were chosen to cover the entire rank range from subbituminous coal to anthracite. To be able to study the organic sulfur groups, the vitrinite concentrates were separated from each coal sample. The results confirm the larger amount of sulfide in low-rank coals. The amount of thiophenes generally increases with rank. Nevertheless, sulfur functionality distribution can vary from coal to coal even at the same rank.

Effect of calcium and calcium minerals in coal on its thermal analysis

Abstract The effect of the presence of limestone and dolomite in coal, and calcium in lignite, on atmospheric-pressure temperature-programmed reduction (AP-TPR) analysis was studied. AP-TPR experiments were carried out on a bituminous coal with added limestone and dolomite and on a demineralized lignite. The results showed that both calcium minerals captured the gaseous H 2 S formed under AP-TPR conditions and produced CaS. Consequently the sulfur recovery monitored was too low and the AP-TPR kinetograms were deformed. The study also showed that the influence of dolomite is greater than of limestone. AP-TPR analysis of lignite demineralized and then loaded with calcium ions again showed a clear lowering of sulfur comparable with that of dolomite, but starting at a higher temperature.