Contents - Akademi Sains Malaysia

ASM Science Journal, Volume 7(1), 2013Table 3. Conversion, PAS yield, AS yield and O+G yield.Ni Loading Extraction conditions Conversion (% daf)(wt%) FR (ml/min) RT (min) Temp. (ºC) Total PAS AS O+GEffect of Ni loading (two-stage solvent flow reactor)1 1 30 420 78.1 10.3 7.4 60.43 1 30 420 78.2 8.1 4.4 65.75 1 30 420 77.9 5.5 2.9 69.57 1 30 420 78.9 5.3 3.8 69.8Table 4. Proximate and ultimate analyses of raw and CLR of MB coal.SampleAnalysesCalorificProximate (wt% db) Ultimate (wt% db) value (MJ/Kg)VM FC Ash C H N Oa SRaw 44.7 51.1 4.2 63.9 5.1 1.9 28.6 0.5 24.6CLR 27.9 65.0 7.1 73.7 4.1 2.5 19.6 0.1 27.6VM = volatile matter; FC = fixed carbon; a = calculated by difference.Another reason was that the low rank coals with theirhigh concentrations of oxygen functional group adsorbedthe multi-charged metal cation through an ion exchangemechanism and this property is used for dispersing metalcatalysts across a coal surface prior to extraction (Huet al. 1998). The catalyst itself improves the reactivity ofliquefaction by weakening the dependence of conversionon molecular hydrogen and hydrogen donor solvent (Huet al. 2000). Thus, it would be beneficial in decreasing thehydrogen consumption during liquefaction and increasingthe conversion of coal liquefaction.Coal Liquid Analysis by GCMSThe aim of this section is to compare the chromatographyspectra for the catalytic and un-catalytic coal liquefactionliquid. Theoretically, the reducing catalyst used wouldfurther reduce the coal extracts including coal liquid intosmaller molecular compounds. By observing the differencein the chromatography spectra between those two coalliquids, the reducing effect of catalyst could be proved.Figures 7 and 8 show the results of coal liquid extract fromcoal liquefaction at a temperature of 420ºC without andwith catalyst by using GCMS, respectively.For MB coal extraction, the existence of a complicatedmixture and that of many compounds were identified.MB coal is a low rank coal having high carboxyl and/or sulphidic type functional groups and based on theprevious study, the covalent breakage starts at temperaturesbetween 400ºC to 425ºC (Begon et al. 2002). Accordingto Prasassarakich et al. (2007), during coal liquefactionthe main reactions were thermolysis, dehydrogenation,cleaving of cyclic hydrocarbon structures into an openchainhydrocarbon and condensation reactions. Moreover,Prasassarakich et al. (2007) found that the improvement incoal liquefaction can be achieved by adding catalyst intothe coal. Furthermore, he concluded that in the absenceof a catalyst, the oil yield decreased and the content ofnaphtha and kerosene increased while the light gas oil andgas decreased. The presence of catalyst would benefit theformation of lighter components, kerosene and light gasoil.From Figure 8, it can also be seen that there is acollection of compounds that appeared at the beginningof retention time. It showed that there are differences incompounds between these two chromatography spectra(Figure 7) which indicated that the catalyst did play itspart in further reducing the molecular compounds incoal extracts. The major compounds that were identified(by mass spectrometer’s library) in coal liquid extractionfor non-catalytic liquefaction were mostly alcohols andaromatic hydrocarbons. Benzene and naphthalene are twopopular compounds in coal. Yagmur et al. (2008) foundthat most of the components in coal consist of condensedaromatic and oxygenous aromatic compounds during theirstudy on liquefaction of Zonguldak bituminous coal usingtetralin as solvent.Furthermore, several aromatic compounds were foundto decrease in intensity when the chromatography wascompared for catalytic and non-catalytic coal extracts.Compounds such as 1-methyl-indan, 2-ethyl-2,3-dihydro-1H-indene, and 3,4-dihydro-1(2H)-naphthalenone havehigh intensity in non-catalytic coal extracts but low in14