A novel method to discriminate between the residues of kerosene or gas oil and the residues of domestic plastics in fire debris was developed based on the analysis of alkylcyclohexanes by gas chromatography-mass spectrometry (GCMS). n-Alkylcyclohexanes (n-alkylCys) and n-alkanes in kerosene or gas oil exhibited a series of molecular distribution patterns which are characteristic of oils manufactured by fractionation. AlkylCys were detected from C6 to C15 in kerosene and from C6 to C23 in gas oil. In contrast, alkylCys were detected from C6 to C10 in the pyrolysis products of polyethylene and not at all in those of polypropylene, polyvinyl chloride, poly?styrene, and polyester. Such analysis allows definitive discrimination between the residues of kerosene or gas oil and the pyrolysis products of plastics, and will be very useful for discriminating whether alkanes detected by GCMS were derived from petroleum or from plastic in fire debris samples.
Waste cooking oils were investigated as the raw material for biodiesel production using calcium oxide as the solid base catalyst in refluxing methanol. Edible soybean oil and waste cooking oil from restaurants were converted into biodiesel completely within 2 h. However, catalyst recovery after the reaction markedly decreased for the waste cooking oil, due to dissolution of the solid base catalyst. Catalytic induction period was observed in the early stage of the reaction of the waste cooking oil. Most of the solid base catalyst was converted into calcium methoxide and glyceroxide, and trace of saponified calcium was collected after the reaction of the waste cooking oil. Waste cooking oil from homes increased the catalyst recovery, in comparison with waste oil from restaurants. The catalyst recovery was considerably improved by a removal of free fatty acids. Both polar fraction and moisture in the waste cooking oil were minor poisons for the solid base catalyst. Based on the above results, improvement of the biodiesel production requires protection for the solid base catalyst from the poisoning species contained in the waste cooking oil.
The antagonism between nitroxides of hindered amine light stabilizers (HALS NO) and phenolic antioxidants, such as 2,6-di-t-butyl-4-methylphenol (BHT), was investigated. Identification of the reaction products of HALS NO and BHT clarified the formation of HALS hydroxylamine (HALS NOH) and HALS amine (HALS NH) by the reduction of HALS NO, and the formation of quinone methide and stilbene quinone by the oxidation of BHT. The identification of these products in the reaction of HALS NO with BHT suggests a new antagonism between HALS NO and BHT: two molecules of HALS NO form HALS nitrosonium by electron transfer. The nitrosonium has strong oxidation power, and uselessly oxidizes a phenol such as BHT to quinone methide and finally stilbene quinone, while the nitrosonium and HALS NO are reduced to HALS NOH and HALS NH.
Ir/SiO2, Ir/WO3-SiO2 and Ba doped Ir/WO3-SiO2 powder catalysts have high activity for the selective reduction of NO with CO in the presence of O2 (CO-SCR). The present study investigated the activity of these three Ir/SiO2-based catalysts in monolithic form for industrial applications. The catalytic activity was evaluated during heating and cooling cycles between 200°C and 600°C. All monolithic catalysts showed low activity for NO reduction during the first heating cycle but high activity appeared from the next cycle. The active temperatures for the monolithic catalysts are different to those for the powder catalysts, probably because of the differences in heat and mass transfer. The activities for CO-SCR gradually decreased with the number of cycles. The activity and durability of the monolith catalysts were consistent with those of the powder catalysts. Ba doped Ir/WO3-SiO2 monolith catalyst was the best catalyst. XRD spectroscopy showed that catalyst deactivation was caused by oxidation of iridium metal, which is the active species, because the activities of the aged catalysts were recovered by hydrogen reduction. The presence of SO2 in the reaction gas increased the activity of Ir/SiO2 catalyst, but had little effect on the activities of Ir/WO3-SiO2 and Ba doped Ir/WO3-SiO2 catalysts.
Catalyzed diesel particulate filter (CDPF) is an effective way of reducing the carbon particles contained in the emissions of diesel vehicles. The behavior of the oxygen of cerium composite oxides during carbon combustion was investigated using isotopic oxygen to oxidize carbon particles trapped in the CDPF. The released oxygen from cerium composite oxides was used in the oxidation of carbon particles at lower temperatures. The effect of oxygen release coincided with the effect of temperature for carbon particle oxidation, so that CePr composite oxides that released oxygen at the lowest temperatures caused carbon oxidation from the lowest temperatures. Therefore, improvement of the oxygen release property of cerium composite oxides will reduce the temperature required for the oxidation reaction of carbon particles in the CDPF.
Compositional analyses of Gas to Liquid (GTL) diesel oil and Biomass to Liquid (BTL) diesel oil were carried out at the molecular level using GC-FID and GC-MS. Commercially available reagents and standard samples especially prepared were used as the reference samples for peak assignment in addition to the commercial mass spectrum library. BTL diesel oil was separated into the saturate, olefinic, aromatic, and polar fractions by open column chromatography. BTL diesel oil was also hydrogenated to allow type analysis of the olefinic compounds. GTL diesel oil consisted of only paraffinic compounds, i.e., 17 wt% of straight paraffins, 20 wt% of monomethyl paraffins, and 63 wt% of other branched paraffins. About half of the other branched paraffins could be analyzed based on molecular weight and concentrations, but the small quantity of the remainder continuously contributed to drift of the chromatography base line. GC chromatography of BTL diesel oil showed quite low drift of the baseline. BTL diesel oil consisted of 75 wt% of satutates, 22 wt% of olefins, 2.5 wt% of aromatics and 0.88 wt% of polar compounds. The saturate fraction consisted of 60 wt% of straight paraffins, 8.5 wt% of monomethyl paraffins, and 7.5 wt% of other branched paraffins/cycloparaffins. The olefinic fraction mainly consisted of straight 1-olefins and straight 2-olefins (cis and trans) with 0.3-0.4 wt% of cycloolefins. After hydrogenation of BTL diesel oil, the contents of straight paraffins increased by 18 wt%, monomethyl paraffins by 2 wt%, and other branched paraffins/cycloparaffins by 2 wt%, indicating that BTL diesel oil contained 18 wt% of straight oleffins, 2 wt% of monomethyl olefins, and 2 wt% of other branched olefins/cycloolefins. BTL diesel oil contained 2.5 wt% of aromatic compounds, consisting of 1.9 wt% of benzenes, 0.4 wt% of tetralins/indanes, and 0.2 wt% of naphthalenes. The polar fraction consisted of alcohols, ketones, aldehydes, and other unknown compounds.