Hideo Okado

Synthesis of ZSM-5 zeolite with small crystal size and its catalytic performance for ethylene oligomerization

Abstract ZSM-5 zeolites of SiO 2 Al 2 O 3 = 25 with a small crystal size were synthesized under various conditions in order to clarify a relationship between external surface area and catalytic performance, especially lifetime, for the oligomerization of ethylene to higher hydrocarbons of the gasoline range. The measurement of the external surface area, XRD patterns, and FTi.r. spectra of the resulting ZSM-5 zeolites suggested that their crystal grains were very fine. The shapes and sizes of the primary grains of the ZSM-5 zeolites were observed by means of a scanning electron microscopy with a magnification of 300,000. The crystal sizes were in the range of 30–50 nm. In the oligomerization of ethylene, a proton-type zeolite that was synthesized under a high molar ratio of OH SiO 2 showed both high ethylene conversion and high gasoline range selectivity for three times longer on-stream time than those of other zeolites. The external surface area of the zeolite was also three times greater than those of other zeolites, which indicated that the lifetime of ZSM-5 zeolite in the oligomerization of ethylene depended on the external surface area or crystal size.

Deactivation resistance of ZSM-5-type zeolites containing alkaline earth metals used for methanol conversion

Abstract ZSM-5 and its alkaline earth forms were used for methanol conversion at 600°C where unmodified ZSM-5 rapidly cokes. Of the alkaline earth forms, the calcium and strontium forms are much more coke resistant providing a long on-stream life for methanol conversion. Coke burning regeneration of the calcium form after one cycle results in some migration of calcium to the external surface of the zeolite which lowers the coke resistance. These findings are attributed to the effect of the alkaline earth on the acidity of the zeolite.

Improvement of catalyst stability of ZSM-5 zeolite containing calcium by modification with CaCO3.

Abstract The catalyst life of Ca H ZSM 5, which yields high selectivities to light olefins in methanol conversion, was significantly extended by modification with CaCO 3 . The amount of coke on CaCO 3 /Ca H ZSM 5 after a long-term aging in methanol conversion was considerably less than that on Ca H ZSM 5, indicating that CaCO 3 inhibits the formation of an excessive amount of coke. However, CaCO 3 can hardly prevent the catalyst structure from degradation caused by dealumination with water. From these results, we have concluded that CaCO3 is effective for the improvement of resistance to coking rather than that to steaming, for high catalyst stability.

Hydrogenation of carbon monoxide to form light olefins over zeolite-based iron catalysts

Abstract Zeolite-based iron catalysts promoted with various transition metals were tested by using a reaction gas mixture of CO:H2:Ar=45:45:10 at temperature ranging from 350to 450 ° under pressure varying from; 0.2 to 4.5 MPa. It was found that high selectivity of C2and C3 olefins was obtained with Fe-Ti-V- and Fe-Ti-Mn-zeolite-based catalysts.

High Steam Stability of ZSM-5 type Zeolites Containing Alkaline Earth Metals

Abstract In order to examine the dealumination of the framework of H-ZSM-5 type zeolites containing alkaline earth metals, which yields high selectivities to light olefins in methanol conversion at high temperatures, the characteristics of the steamed zeolites were investigated by means of 27 Al MASNMR, FT-ir, TPD of NH 3 and methanol conversion. It was found that the dealumination of the framework of the H-ZSM-5 type zeolites is greatly inhibited due to alkaline earth metals occluded and that the rate of the dealumination has a secondorder dependence on the amount of the framework aluminiums.

Development of a high efficiency GTL process based on CO2/steam reforming of natural gas and slurry phase FT synthesis

Abstract CO 2 /steam reforming catalysts composed of noble or transient metal and MgO support and Ru-based slurry phase FT synthesis catalyst have been developed to improve the efficiency and lower the costs of GTL processes. Their high carbon and hydrogen conversion in the CO 2 /steam reforming, low methane selectivity, high olefin/paraffin ratio of the light hydrocarbons used in the FT synthesis, together with their durability, have been verified through extensive bench scale tests. Based on the performance of these catalysts, an optimal commercial scale GTL plant configuration has been developed, along with a cash flow economic evaluation that confirms the promising economics of this process. The COE (Crude Oil Equivalent) price is around US

Oxidative coupling of methane over ternary metal oxide catalysts consisting of Groups I, III and V elements in the Periodic Table

17/bbl-product oil.

Oxidative coupling of methane over alkali halide- promoted perovskite oxide catalysts

Abstract Ternary metal oxides consisting of Group I (alkali metals)/Group III/Group V metals with an atomic ratio of 1:1:0.3 were prepared and their catalytic performance for the oxidative coupling of methane as well as their physicochemical properties were investigated. When adding Group V metals to Group I/Group III binary catalysts, a noticeable increase in the conversions of methane and oxygen was observed without any change in C 2+ selectivity. Of the ternary metal oxide catalysts, a Na/La/0.3Nb metal oxide showed the highest performance, viz. a methane conversion of 16.0% and a C 2+ selectivity of 74.1% at 1023 K under atmospheric pressure with a total gas flow-rate of 100 ml NTP/min ( CH 4 /O 2 molar ratio= 9 ). The stability test using a Na/La/0.2Nb catalyst, which was performed under the same conditions as above, showed that the catalyst was very stable with no decrease in methane conversion and C 2+ selectivity for more than 100 h. The crystalline structure, the surface composition and properties of base sites of Na/La/Nb oxide catalysts were investigated using X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) of carbon dioxide. The catalytic performance of the Na/La/Nb mixed oxides depended on the ratio of the two crystalline phases of La 2 O 3 and La 3 NbO 7 . When sodium was added to La 2 O 3 with a La/Na ratio of 1, new base sites were produced, resulting in an increase in the C 2+ selectivity with a significant decrease in methane conversion. The methane conversion was increased by adding a small amount of niobium to the Na/La catalyst, resulting in a change of part of the La 2 O 3 to La 3 NbO 7 . However, when all of the La 2 O 3 was changed to La 3 NbO 7 , the C 2+ selectivity decreased due to the lack of new base sites. A good balance of both crystals (La 2 O 3 and La 3 NbO 7 ) may be obtained at a Nb/Na atomic ratio of 0.15–0.3, which optimizes the catalytic performance of the mixed oxides.

Oxidative coupling of methane over sodium-doped CaO catalysts prepared by the sol-gel method

Abstract The catalytic performance of some alkali halide-promoted perovskite oxides as well as that of the perovskite oxides alone for the oxidative coupling of methane were investigated. Although the perovskite oxides alone showed relatively low catalytic activity, a noticeable increase in activity and C2 selectivity was observed when the oxides were promoted by alkali halides. Sodium chloride ( NaCl ) was the most effective promoter among the alkali halides. Of the perovskite oxides examined in the present study, the catalytic activity of PbTiO3 was most remarkably promoted by addition of NaCl, because it showed almost no activity for the reaction in the absence of NaCl. The maximum C2 yield of 28.2% was obtained for an NaCl (0.2 mol against 1 mol of PbTiO3) added PbTiO3 catalyst, where methane conversion and C2 selectivity were 50.7% and 55.7%, respectively, under the conditions;Pch4=10.1 kPa,PO2 = 5.1 kPa,PHe = 86.1 kPa, total gas flow-rate =100 ml STP/min, temperature = 1023 K,W/F= 0.22 g min/ml. The stability test for the 0.2 mol NaCl/PbTiO3 catalyst suggests that the catalyst loses its high activity when most of the NaCI has been removed from the catalyst during the test. However, the same level of activity is recovered when NaCI is added again to the deactivated catalyst. The thermal and temperature-programmed desorption analyses suggest that both high activity and high C2 selectivity for the Nacl-promoted PbTiO3 catalyst can be ascribed to the generation of new basic active sites. These sites must be created through the interaction between NaCl and PbTiO3 on the surface of the catalyst.

Natural Calcium Compounds as Catalysts for Oxidative Coupling of Methane

Abstract Sodium-doped calcium oxide (Na/CaO) catalysts prepared by the sol-gel method (SGM) show relatively high performance for oxidative coupling of methane (OCM) compared with that prepared by impregnation method (IM). The difference between the performance of these catalysts for OCM seems to come from the difference in morphology and TPD profiles of these catalysts.