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M.A.M. Ishak et al.: Liquefaction of MB Coal via Semi-continuous Two-stage Solvent Flow Reactor Systemextraction method. The coal mixtures contained in the 1000ml round-bottom flask was heated until a colourless solventwas observed in the soxhlet extractor (i.e. about 4 h). Thehexane-soluble was then cooled down before the n-hexanewas evaporated by using the rotary evaporator. Toluenewas used to replace the hexane and the extraction wascontinued on the hexane-insoluble in the soxhlet extractorand the same procedure was applied in the extraction usingTHF. Figure 2 shows the schematic diagram of soxhletextraction method.The coal liquid was analyzed by Gas ChromatographyMass Spectroscopy (Varian Model CP-3800) according toASTM D2887. The column used is CP8944, 30 m 3 0.25mm 3 0.39 mm packed with VF-5ms. The oven temperaturewas raised from 60ºC to 270ºC at a constant heating of 5ºC/min. The separated compounds will immediately enter themass spectrometer which generates the mass spectrum forthe compounds. The carrier gas used was helium througha flow rate of 20 ml/min and the analysis was run in splitmode at 30:70. The raw and the coal liquefaction residuewere analyzed for proximate analysis using DTA/DSC TAModel SDT Q600 that follows the ASTM D2974. Carbon,hydrogen and nitrogen analyses were performed using anElemental Analyzer (EA), model CHNS-932 series, withhelium gas as the carrier and followed the ASTM D3172 forthe ultimate analysis.RESULTS AND DISCUSSIONLiquefaction Using Solvent-flow Reactor SystemEffect of reaction temperature. Effects of the reactiontemperature on the liquefaction of MB coal are representedin Table 2 and Figure 3. During this experiment, otherparameters such as solvent flow-rate and reaction time werefixed at 1 ml/min and 30 min, respectively. It is equallyimportant to determine the appropriate temperature for theliquefaction in order to enhance the coal conversion and oilyield. Figure 3 shows that the coal conversion increasedwith increasing temperature. It was also noted that theincreased reaction temperature also increased the oil+gasyield. At low temperature (300ºC), the coal conversion wasat the lowest and increased significantly until it reached420ºC where the conversion began to linear up.According to Karaca et al. (2001), the bond cleavagereactions in lignite and pre-asphaltene occurredsimultaneously beyond 350ºC. Thus, it was possible thatTable 1. Characteristics of Mukah Balingian coal sample.Proximate analysis (wt% db)Ultimate analysis(wt% daf)Calorificvalue (MJ/kg)Volatile Fixed Ash C H N S Omatter carbon contentRaw coal 44.7 51.1 4.2 63.9 5.1 1.9 0.5 28.6 24.6(daf = dry-ash-free basis, db = dry basis)Table 2. Effect of various extraction conditions for coal liquefaction on the conversion of product yields.ExpExtraction conditionsConversion (% daf)FR (ml/min) RT (min) Temp. (ºC) Total PAS AS O+GEffect of solvent flow-rate1 1 30 420 78.9 12.4 11.9 54.72 3 30 420 78.1 12.0 16.5 49.73 5 30 420 78.4 11.4 17.3 48.6Effect of reaction time4 1 30 420 77.9 12.4 11.9 54.75 1 45 420 78.7 11.6 8.8 58.36 1 60 420 79.4 11.9 7.3 60.1Effect of reaction temperature7 1 30 300 41.2 15.1 12.4 13.78 1 30 350 59.5 15.6 13.5 30.49 1 30 400 73.1 7.6 11.7 53.810 1 30 420 78.9 11.8 12.3 54.611 1 30 450 79.2 11.3 13.1 54.8FR = Solvent flow-rate; RT = Reaction time; Temp = Reaction temperature; Total = Coal conversion; PAS = Pre-asphaltene;AS = Asphaltene; O+G = Oil+gas.9