• Energy Research

Abstract Waste tires are attractive sources for alternative energy due to their long hydrocarbon chains with a high heating value. However, the condensed (volatile portion) pyrolysis oil derived from waste tires contains a relatively large level of sulfur compounds (1.15 wt%), which is not appropriate for use in combustion engines. Therefore, this research aimed to improve the waste tire pyrolysis oil (WTPO) via hydrodesulfurization (HDS) catalyzed by molybdenum (Mo), nickel–Mo (NiMo) or cobalt–Mo supported on alumina (γ-Al 2 O 3 ). The maximum % sulfur removal (87.8%) was achieved when the reaction was performed at 250 °C for 30 min using a 2 wt% NiMo/γ-Al 2 O 3 catalyst loading based on the WTPO content and 20 bar initial hydrogen pressure. The amount of sulfurous compounds in the waste tire pyrolysis oil was determined using gas chromatography spectroscopy equipped with a flame photometric detector (GC–FPD). The HDS of the WTPO was effective to reduce the sulfurous compounds, especially thiophene and its derivatives. The results from the simulated distillation gas chromatography (GC–SIMDIS) showed that the hydrodesulfurized WTPO (HDS-WTPO) was mainly composed of a light naphtha fraction (ca. 69%). The heating value of the HDS-WTPO (44 MJ/kg) was similar to those for commercial diesel (45 MJ/kg) and gasoline (gasohol) fuels (47 MJ/kg).

AbstractRenewable fuels are major alternatives to fossil fuels. Biomass was considered as raw materials and renewable energy sources. Pyrolysis process is one of the efficient methods for converting biomass in bio-oil. This work investigates the pyrolysis of Giant Leucaena wood in liquid phase by various conditions: The experiments were conducted in an autoclave at following conditions; temperature of 325–400°C, holding time of 0–60min, biomass 250 gram, NiMo/Al2O3 catalyst weight (0–30 percent by weight) by using hexane as a solvent. Bio-oils were analyzed by gas chromatography–mass spectrometry to identify the structure and chemical compounds, also by CHN analyzer. The results showed that the liquid products were phenolic compounds, cyclic compounds and furans which were determined by gas chromatography.

This work investigated an influence of operating conditions on the biocrude yield and properties obtained from hydrothermal liquefaction (HTL) of Coelastrum sp. microalgae in a two-step sequential HTL (THTL) and a single-step HTL (SHTL) using a semi-continuous system. A higher biocrude yield with a lower nitrogen content was obtained with the THTL process than the SHTL one. The operating temperature, pressure and water flow rate were sequentially varied in a univariate analysis for a 2 h reaction time to optimize the obtained biocrude yield. Increasing the temperature improved the biocrude yield, but the second step temperature should not be higher than 320 °C to prevent the thermal cracking to gaseous compounds. The optimal conditions of THTL were preliminarily temperature of 200 and 320 °C and pressure of 7 and 20 MPa for the first and second step, respectively, both with a water flow rate of 0.50 mL/min.

Abstract The extremely increasing amount of plastic waste due to the development of human society, economics and urbanization is an emergency task that must be urgently handled in order to reduce environmental problems. Although the plastic wastes can be converted to alternative liquid fuels through pyrolysis process, the compositions in the pyrolysis oil depended on the chemical structure of raw materials and pyrolysis condition affect its quality. Thus, this research aimed to comparatively investigate the production of alternative liquid fuels obtained from mixed plastics containing polystyrene (PS)/polyethylene terephthalate (PET)/polyethylene (PE)/polypropylene (PP) at 20/5/35/40 (w/w) via non-catalytic cracking (under N2 atmosphere), non-catalytic hydrocracking (under H2 atmosphere), and catalytic hydrocracking over 10 wt% Ni/SBA-15 catalyst conducted at an atmospheric pressure and 650 °C for 1 h. The product yields and chemical compositions (paraffins, olefins, aromatics and PAHs) in the liquid products generated from these processes were investigated and also compared to ones obtained from the non-catalytic processes of each plastic. Herein, the characteristics of 10 wt% Ni/SBA-15 catalyst was analyzed by N2-adsorption/desorption, X-ray diffraction (XRD), and H2-temperature programmed reduction (H2-TPR). The results indicated that the non-catalytic processes of PS provided the highest content of oil and wax product (ca. 92 wt%). Whereas, the non-catalytic hydrocracking of the mixed plastics gave the lowest one (ca. 69 wt%). However, the catalytic hydrocracking over 10 wt% Ni/SBA-15 catalyst (2.5 – 10.0 wt% based on the mixed plastics) could suppress the cracking and yielded the higher amount of oil and wax to ca. 76–80 wt%. To consider the chemical compositions in the liquid phase, the PAHs formation was relied on the aromatic structure in the feedstocks. The liquid product derived from the non-catalytic processes of PS contained the highest amount of PAHs compounds (2622–2926 ppm) followed by the mixed plastics. When the 10 wt% Ni/SBA-15 catalyst was applied to the catalytic hydrocracking of the mixed plastics, the amount of PAHs in the liquid product decreased from 1621 ppm to ca. 1000 ppm (30 – 40% PAHs reduction) without the reduction of heating value when compared to one obtained from the non-catalytic processes.

Waste tire pyrolysis oil has high potential to replace conventional fossil liquid fuels due to its high calorific heating value. However, the large amounts of sulfurous compounds in this oil hinders its application. Thus, the aim of this research was to investigate the possibility to apply the photo-assisted oxidation catalyzed by titanium dioxide (TiO2, Degussa P-25) to partially remove sulfurous compounds in the waste tire pyrolysis oil under milder reaction conditions without hydrogen consumption. A waste tire pyrolysis oil with 0.84% (w/w) of sulfurous content containing suspended TiO2 was irradiated by using a high-pressure mercury lamp for 7 h. The oxidized sulfur compounds were then migrated into the solvent-extraction phase. A maximum % sulfur removal of 43.6% was achieved when 7 g/L of TiO2 was loaded into a 1/4 (v/v) mixture of pyrolysis waste tire oil/acetonitrile at 50 °C in the presence of air. Chromatographic analysis confirmed that the photo-oxidized sulfurous compounds presented in the waste tire pyrolysis oil had higher polarity, which were readily dissolved and separated in distilled water. The properties of the photoxidized product were also reported and compared to those of crude oil.

We evaluated two-step hydrothermal liquefaction in a semi-continuous reactor for recovery of both nutri- ents and biocrude from the alga Coelastrum sp. in direct comparison with a one-step process. The influence of the operating temperature, pressure and water flow rate was investigated by means of a 2 k factorial experimental design and response surface methodology. The two-step process gave a higher total biocrude yield (~36 wt% (daf. basis)) and nutrient recovery level in terms of nitrogen containing compounds (~60 wt% of the protein content in the original algae as ammonium and nitrate ions and protein/polypeptides) than the single-step process. The highest biocrude yield was achieved at first-step temperature of 473 K, second-step temperature of 593 K, pressure of 200 bar and water flow rate of 0.5 mL/min.

Transformation of some oxygenated compounds in bio-oil derived from biomass pyrolysis via hydrodeoxygenation (HDO) generally improves its quality and potentially produces bio-based chemicals. Although alumina (Al₂O₃) supported catalysts are normally applied for HDO, they have certain limitations, such as acidity and high susceptibility to water, which need to be improved. In this research, an Al2O3-incorporated zirconia (ZrO2) composite (AZ) was prepared as a support of nickel (Ni)-molybdenum (Mo) catalysts used for HDO of guaiacol (GUA) and real bio-oil derived from pyrolysis of Leucaena leucocephala trunks to produce phenols. In the absence of water, the NiMo catalyst supported on AZ at 1/1 Al2O3/ZrO2 molar ratio [NiMo/AZ(1/1)] having higher reducibility with a greater number of weak-medium acid sites provided >98% GUA conversion with 87% selectivity to phenols. In the presence of water, the NiMo/AZ(1/1) catalyst maintained its catalytic activity, whereas NiMo/Al2O3 catalyst showed its deactivation to obtain the lowering GUA conversion (27.1% reduction). The FESEM and 27Al-NMR analyses revealed that the addition of ZrO2 improved the water tolerance of the catalyst by protecting the Al2O3 structure and preventing the transformation of Lewis acid-related tetrahedral Al to octahedral Al. Moreover, the NiMo/AZ(1/1) catalyst exhibited the highest HDO activity for real bio-oil without solvents, achieving a maximum oil yield of 25.2 wt% with 75.6% selectivity to phenols and the lowest coke formation.

Abstract Effect of copper (Cu) or cerium (Ce) as promoters for nickel-molybdenum/γ-alumina (NiMo/γ-Al2O3) catalyst on the hydrodeoxygenation (HDO) of guaiacol (GUA), a model oxygenated compound found in a bio-oil derived from woody biomass, was comparatively investigated. The addition of Cu- or Ce-promoters affected the physicochemical properties of the NiMo catalyst. The NiMo catalyst promoted by Cu showed the higher reducibility, whilst the Ce-promoter (2–8 wt% based on γ-Al2O3 content) provided the NiMo catalyst with a higher distribution of active metals and induced a greater difficulty in the reduction under hydrogen (H2) atmosphere. For the HDO of GUA at a mild reaction condition (10 bar initial H2 pressure and 300 °C) in the absence of solvent, the Cu-promoter enhanced the hydrogenation activity of the NiMo catalyst to convert GUA to phenol and methylphenols, one-atomic oxygen species. Whereas, the addition of Ce obviously inhibited the formation of coke on the catalyst surface after a long reaction period (6 h) and gave a higher GUA conversion level with increasing yield of phenols. For the HDO of real bio-oil obtained from the fast pyrolysis of cassava rhizome, the NiMo catalysts promoted by Cu or Ce at 4 wt% based on the γ-Al2O3 content showed a higher performance at eliminating the oxygenated compounds in the bio-oil, reducing the oxygen/carbon (O/C) molar ratio by over seven-fold from 1.75 to 0.24–0.25. Moreover, the gross heating value of the bio-oil was improved from 21.5 to ca. 29.0 MJ/kg after the HDO process. However, the addition of the Cu or Ce promoter did not inhibit coke deposition, possibly due to the acidic properties of the bio-oil that deteriorated the catalyst performance by metal leaching.