The dehydration of ethanol into ethylene was investigated over various solid acid catalysts, such as zeolites and silica-alumina, at temperatures ranging 453-573 K under atmospheric pressure. Ethylene was produced via diethyl ether during the dehydration process. H-mordenites were the most active for the dehydration. It was suggested that the catalyst activity could be correlated with the number of strong Brønsted acid sites in the catalyst. Further, the H-mordenite was more stable with a SiO 2 /Al 2 O 3 ratio of 90 than with a SiO 2 /Al 2 O 3 ratio of 20.
Renewable green diesel-type alkanes can be produced by hydrotreating jatropha oil and vegetable oils at standard hydrotreating conditions (i.e., 543−573 K) with Pt/H-ZSM-5 catalysts, which are active under the weight ratio of jatropha or vegetable oil/catalyst of 1. The carbon molar yield of straight chain C15−C18 alkanes was ∼80% for hydrotreating pure jatropha oil. However, under the jatropha oil/catalyst weight ratio of 10, being important from a practical point of view, the alkanes yield falls to only 2.3%. Under a high jatropha oil/catalyst ratio of 10, rhenium-modified Pt/H-ZSM-5 catalyst is found to be effective for raising the C15−C18 alkanes yield. The yield of C15−C18 alkanes is 67% at an optimun Re/Al molar ratio of 0.8. Investigation of catalyst natures indicates that metallic Pt and Re are independently present on the surface, but synergism of these two metals could play an important role in the hydrotreating reaction, even at a high ratio of jatropha oil/catalyst of 10. The reaction pathway involves hydrogenation of the CC bonds of the jatropha oils followed by mainly hydrodeoxygenation with decarbonylation and decarboxylation to form C15−C18 straight chain alkane mixtures.
Our group's studies on Cu/ZnO-based catalysts for methanol synthesis via hydrogenation of CO 2 and for the water-gas shift reaction are reviewed. Effects of ZnO contained in supported Cu-based catalysts on their activities for several reactions were investigated. The addition of ZnO to Cu-based catalyst supported on Al 2 O 3 , ZrO 2 or SiO 2 improved its specific activity for methanol synthesis and the reverse water-gas shift reaction, but did not improve its specific activity for methanol steam reforming and the water-gas shift reaction. Methanol synthesis from CO 2 and H 2 over Cu/ZnO-based catalysts was extensively studied under a joint research project between National Institute for Resources and Environment (NIRE; one of the former research institutes reorganized to AIST) and Research Institute of Innovative Technology for the Earth (RITE). It was suggested that methanol should be produced via the hydrogenation of CO 2 , but not via the hydrogenation of CO, and that H 2 O produced along with methanol should greatly suppress methanol synthesis. The Cu/ZnO-based multicomponent catalysts such as were highly active for methanol synthesis from CO 2 and H 2 . The addition of a small amount of colloidal silica to the multicomponent catalysts greatly improved their long-term stability during methanol synthesis from CO 2 and H 2 . The purity of the crude methanol produced in a bench plant was 99.9 wt% and higher than that of the crude methanol from a commercial methanol synthesis from syngas. The water-gas shift reaction over Cu/ZnO-based catalysts was also studied. The activity of Cu/ZnO/ZrO 2 /Al 2 O 3 catalyst for the water-gas shift reaction at 523 K was less affected by the pre-treatments such as calcination and treatment in H 2 at high temperatures than that of the Cu/ZnO/Al 2 O 3 catalyst. Accordingly, the Cu/ZnO/ZrO 2 / Al 2 O 3 catalyst was considered to be more suitable for practical use for the water-gas shift reaction. The Cu/ZnO/ZrO 2 /Al 2 O 3 catalyst was also highly active for the water-gas shift reaction at 673 K. Furthermore, a two-stage reaction system composed of the first reaction zone for the water-gas shift reaction at 673 K and the second reaction zone for the reaction at 523 K was found to be more efficient than a one-stage reaction system. The addition of a small amount of colloidal silica to a Cu/ZnO-based catalyst greatly improved its long-term stability in the water-gas shift reaction in a similar manner as in methanol synthesis from CO 2 and H 2 .
H-ZSM-5 (Si/Al 2 = 29) zeolite showed especially high activity in the conversion of ethanol to BTX (benzene, toluene, xylenes), while other zeolites exclusively formed ethylene. Noble metal catalysts supported on H-ZSM-5 (29) zeolite have high activity for the formation of BTX. Of these, Au/H-ZSM-5 catalyst can partially inhibit carbon deposition during the reaction, thus maintaining constant catalytic activity for BTX formation.
Biohydrogenated diesel (BHD) and liquefied petroleum gas (LPG) fuel were produced by the hydrotreatment of vegetable oils over Ni–Mo-based catalysts in a high-pressure fixed-bed flow reaction system at 350 °C under 4 MPa of hydrogen. Because triglycerides and free fatty acids underwent the hydrogenation and deoxidization at the same time during the reaction, various vegetable oils (jatropha oil, palm oil, and canola oil) were converted to mixed paraffins by the one-step hydrotreatment process although they contained quite different amounts of free fatty acids. Ni-Mo/SiO2 formed n-C18H38, n-C17H36, n-C16H34, and n-C15H32 as predominant products in the hydrotreatment of jatropha oil. These long normal hydrocarbons had high melting points and thus gave the liquid hydrocarbon product over Ni-Mo/SiO2 a high pour point of 20 °C. Either Ni-Mo/H-Y or Ni-Mo/H-ZSM-5 was not suitable for producing BHD from jatropha oil because a large amount of gasoline-ranged hydrocarbons was formed on the strong acid sites of zeolites. When SiO2-Al2O3 was used as a support for the Ni-Mo catalyst, the pour point of the liquid hydrocarbon product decreased to −10 °C by converting some C15–C18 n-paraffins to iso-paraffins and light paraffins on SiO2-Al2O3. Because SiO2-Al2O3 had a proper solid acidic strength, both the chemical composition and the pour point of liquid hydrocarbon product over Ni-Mo/SiO2-Al2O3 were similar to those of a normal diesel bought from a petrol station. Meanwhile, the glycerin groups in the vegetable oils were converted to propane over Ni-Mo/SiO2-Al2O3 by the hydrogenation and deoxidization. Therefore, the liquid hydrocarbon product can be directly used as a BHD fuel for the current diesel engines, and the gas hydrocarbon product can be used as a liquefied petroleum gas (LPG) fuel in the hydrotreatment of vegetable oils over Ni-Mo/SiO2-Al2O3.
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