Avgamasya asfaltitinin katalizörlü ve katalizörsüz olarak hidrosıvılaştırılması
Catalytic and non-catalytic hydroliquefaction of avgamasya asphaltite
- Tez No: 21822
- Danışmanlar: DOÇ. DR. AYŞE ŞENATALAR(ERDEM)
- Tez Türü: Yüksek Lisans
- Konular: Kimya Mühendisliği, Chemical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1992
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 60
Özet
ÖZET Bu çalışmada, asfalt itten hidrosıvılaştırma ve katalitik hidrosıvılaştırma yöntemleri ile elde edilen dönüşme ve ürün verimleri üzerinde sıcaklık, hidrojen basıncı ve sürenin etkilerinin incelenmesi amaçlanmıştır. Katalitik hidrosıvılaştırma deneylerinde ticari bir katalizör olan CoMo/A^Oj, katı bir süper asit olan Fe»0, /SOi ve MoS« katalizörlerinin kullanımı denenmiştir. Deneyler 500 °C ve 350 atmosfere dayanıklı manyetik karıştırmalı bir otoklavda gerçekleştirilmiş, gaz ürünler gaz kromatografisi ile incelenmiş, sıvı ürünler ise çözünürlüklerine göre yağ ( malten), asfalten ve preasfalten kesimlerina ayırılmıştır. Hidrojen gazının kullanılmadığı, azot atmosferinde yalnızca hidrojen-verici çözücü varlığında yapılan deney lerle kıyaslandığında, sonuçlar, asfaltitin sıvılaşma verimleri üzerinde hidrojen basıncının en etkili parametre olduğunu göstermektedir. 440 "C'da 80 atm soğuk hidrojen basıncında asfaltitin kuru külsüz bazdaki dönüşmesi % 70' lerden % 90 'm üzerine çıkarılabilmiştir. Söz konusu katalizörlerin kullanımının asfaltitin sıvılaşması üzerinde belirgin olumlu bir etkileri olmadığı görülmektedir. Dışardan katalizör eklenmeden elde edilen yüksek verimlerden asfaltitin mineral maddesi ve içerdiği Ni, V gibi değerli metallerin kendi katalitik etkilerinin hidrosıvılaştırma ortamında belirginleştiği açıktır. Katalizörlü deneylerin verimlerinde görülen azalmanın da bir yandan yine mineral madde ve metallerin, diğer yandan da katalizör üzerinde kok oluşumunun yol açtığı katalizör zehirlenmesiyle ilgili olduğu düşünülmektedir.
Özet (Çeviri)
CATALYTIC AND NON-CATALYTIC HYDROLIQUEFACTION OF AVGAMASYA ASPHALTITE SUMMARY On a world scale, coal is the most important alternative fuel and chemical feedstock in terms of reserves, availability, commercial acceptance and technology development. As recently as the 1940s, coal was the primary basis of the organic chemical industry. In the 1950s, petro chemistry underwent a tremendous surge in its industrial development. Today, oil is the primary organic chemical feedstock for all the leading industrial nations. However, even the most optimistic estimates of oil reserves show that, at currently projected production and consumption rates, oil will only last a few more decades. In contrast, known coal reserves should provide fuel and chemical feedstock for several centuries. Recent events in the Middle East once again high lighted the probable ultimate need for effective direct liquefaction processes for the production of transport fuels and chemical feedstocks from coal. Direct coal liquefaction basically involves the partial breaking down of the complex and heterogeneous coal structure into smaller molecules. The aim is to remove mineral matter and heteroatoms such as nitrogen, oxygen, sulfur, and to increase the proportion of hydrogen to carbon, two- or three-fold by weight, and to produce soluble products to distillates of lower molecular weight. The kinetics of hydroliquefaction processes have been examined for a long time and several investigators have shown that the reaction pathway of coal liquefaction is quite complex, and that the conversion of coal to oil should be described by a combination of consecutive and parallel reactions from coal to preasphaltenes, ( asphaltenes, oil and gas. Most of these reactions consume hydrogen. Therefore, most coal liquefaction processes consist of heating the coal in the presence of an organic hydrogen donor solvent, an overpressure of reducing gas, mostly hydrogen, and, in some processes, catalyst. Liquids from coal contain much less hydrogen and considerably more heteroatoms than oil and oil fractions,and have much higher concentration of asphaltenes as well as aromaticity. Besides lignites, there are considerable deposits of other solid fuels, namely oil shales and asphaltites in Türkiye, which have potential for conversion to liquid fuels and chemical feedstocks. Among these, the asphaltites are found in the south eastern region of the country, and vary in their degree of metamorphosis. Avgamasya asphaltite is a representative deposit of the asphaltic substances of southeastern Türkiye which range from asphaltite to asphaltic pyrobitumen according to their degrees of alteration. It is geo-, chemically classified as a solid aromatic - asphaltic oil containing mineral matter, derived from nearby oil deposits by alteration during migration. Asphaltites were observed to contain trace elements with commercial value such as vanadium, nickel, titanium and molybdenum and radioactive minerals such as UjOg and ThC>2. It was also found that they have high hydrogen and sulphur contents compared to lignites. Production of liquids from Avgamasya asphaltite by pyrolysis, sub-critical moderate pressure solvent extrac tion, supercritical gas extraction, and hydro jen-donor solvent extraction were studied and a maximum conversion of 77 % was obtained by hydrogen-donor solvent (tetralin) extraction at 450 °C. Since the products resembled those obtained from coal in terms of their aromaticity and degrees of substitution and, tar sands and heavy oil fractions in terms of their molecular weight and degrees of condensation of aromatic carbon structure, use of hydrogen gas and catalysts is expected to increase the yields and improve the quality of the products. The purpose of this study is to produce liquids from Avgamasya asphaltite using hydroliquef action and catalytic hydroliquefaction, and to investigate the effects of temperature, hydrogen pressure and reaction time, on the conversion and yields obtained with or without the addition of catalysts to the reaction system. All reactions are carried out in a batch reactor having a volume of 250 ml, which is a magnetically stirred stainless steel autoclave that can stand a maximum pressure of 300 bar and a maximum temperture of 500 'C. The V31reaction vessel is heated by an electric furnace of 2.4 kw and is provided with a heater controller. The reactor temperature is measured by a Ni-CrNi thermocouple and automatically controlled by a digital temperature controller. The asphaltite samples used in this study were obtained from Avgamasya, Şırnak. All samples were grounded and sieved to obtain - 125 um fraction. Prior to the experiments proximate analysis was carried out and moisture and ash contents were found to be approximately 1 and 36 %, respectively. In order to investigate the effects of catalyst type, three different catalysts were used in this study. One is a commercial cobalt- molybdenum on alumina catalyst '? containing 4 % CoO and 10 % MoO, cylindirical in shape with 2.6-3 mm diameter. The second catalyst tested in the experiments, is a solid super acid, Fe^Oj/SO/, containing 6.1 wt % SO/, and the last one is a sulfided Mo catalyst which was dispersed by wetting the coal with a solution of (NHi),MoO»S,, which rapidly decompose to MoS, at about 200 *C. 22 g asphaltite samples were loaded into the autoclave with 110 g of tetralin which is considered to be one of the most convenient hydroaromatic solvents with sufficient hydrogen donor ability, in each run and pressurized with hydrogen except for two runs with nitrogen which were performed to determine the effect of hydrogen pressure on liquefaction. In case of CoMo catalyst, the weight ratio of asphaltite to catalyst used was 1:0.075. In the other catalytic experiments, 0.7 wt % of iron was used with respect to the asphaltite sample in case of Fe,0,/SO, catalyst and impregnated (NH.hMoOgS, catalyst on asphaltite contained 1 wt % Mo with respect to asphaltite. In the hydroliquef action experiments performed, the effects of varying reaction time was examined for 45, 60, 90 minutes; temperature for 400, 420, 440 "C and pressure for 60, 80 and 100 bar. In catalytic hydroliquef action with CoMo catalyst, the effects of reaction times of 30, 60, 90 minutes and temperatures of 430, 440, 450 'C and in catalytic hydroliquef action with FeaO,and MoS» catalysts, only the effect of temperature at 4u0 and 440 'C were examined. In each run, after the reactions, the gases were analysed by gas chromatography and liquids were separated VI 11into their fractions by filtration, extraction, precipita tion and vacuum evaporation methods. Liquid products are fractionated into oils (hexane- solubles), asphaltenes (toluene-soluble but n-hexane- insolubles), preasphaltenes (THF-soluble but toluene- insolubles) and insoluble residue (THF-insolubles ). Temperature and pressure in hydroliquefaction of asphaltite are observed to be the parameters which have the strongest effects both on the yield and the conversions. The conversions were observed to be in the range from 80 to 95 %. Oil yield inreases as the temperature increases. There is a relatively little change in the yield of gas. Asphaltenes and preasphaltenes have shown an increasing and a decreasing trend, respectively as the temperature rises. Similar results were observed by varying the reaction time, at 440 °C. The reaction temperature of 440 °C, cold hydrogen pressure of 80 bar and a reaction time of 60 minutes are determined to be the optimum conditions for the hydro- liquefaction of the Avgamasya asphaltite. In the experiments with CoMo catalyst, as has also been mentioned above, the effect of temperature and reaction time were studied. There is not any significant effect of increasing the reaction time on the yields and conversion after 60 minutes, presumably as a result of the deactivation of the catalyst. Conversion decreases with increasing temperature. In case of Fep^and MoS,catalysts, conversions observed are high and above 8o % at all temperatures. In the runs at 400 'C asphaltene yields are higher than those at 440 'C. On the contrary, oil yields are higher at 440 °C. The effects on the yields and conversion of these catalysts are very similar to each other. CoMo catalyst showed the highest selectivity to oil when compared with the other catalysts used. Interestingly, the conversion and product yields obtained by hydroliquefaction were higher than those by catalytic hydroliquefaction. One of the reasons of this, is believed to be related to the catalytic activities of the mineral matter content present in the asphaltite. The mineral content and trace elements such as V, Ni might have also caused problems by poisoning the added catalyst, thus reducing its activity. Although conversions are resonably ixhigh, oil yields are quite low. There is also a high probability that the poisoning might have arisen at least partly from the coking of the asphaltenic structures of high molecular weight, aromaticity and degree of condensa tion, present in the system. According to these experiments, non-catalytic hydroliquef action is observed to give satisfactory results with high yields of oil. The use of catalysts is not found to improve either the conversion or the yields. The catalytic activity of mineral matter and trace elements contained in the asphaltite, is evident from the high conversion and yields, obtained in hydrogen atmosphere without any added catalyst.
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