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The carbonylation of dimethyl ether to methyl acetate was carried out in a high-pressure flowed fix-bed reaction system over heterogeneous halide-free catalysts. The TG curves indicated that solid 12-tungstosilicic acid had a crystal structure (with six crystallization waters) identical to that of solid 12-tungstophosphoric acid, although they had different number of protons in molecules. The BET surface areas greatly increased by Cs substitution in HSiWO, and CsHSiWO showed a BET surface area of 206 m g. For the DME carbonylation at 473 K on 1 MPa under a CO/DME flow rate ratio of 18, CsHSiWO showed a DME conversion (6.7 %) higher than that over CsHPWO (4.6 %) because CsHSiWO had a larger surface area. CsHSiWO and CsHPWO showed high selectivity for methyl acetate of (98.0 and 97.5 %). By adding 1.0 wt% Rh in CsHSiWO, the DME conversion greatly increased from 6.7 to 30.8 % because a multiplier effect occurred between Rh and heteropoly acid. Rh/CsHSiWO showed a higher catalytic performance than those over the reported Rh/CsHPWO and Rh/H-MOR for the carbonylation. The DME conversion increased with increasing Rh loading from 0 to 1.0 wt% but became almost constant when Rh loading ranged from 1.5 to 3.0 wt% over Rh/CsHSiWO. With increasing the CO/DME ratio from 1.8 to 45, the DME conversion increased from 0.9 to 99.4 % over Rh/CsHSiWO at 473 K under 1 MPa. The 1 wt% Rh/CsHSiWO catalyst showed an initial DME conversion of 30.8 % (after 5 min on stream) but the DME conversion decreased to 23.3 % after 5 h on stream at 473 K on 1 MPa under a CO/DME flow rate ratio of 18. [ABSTRACT FROM AUTHOR]

The catalytic activities directing for an improvement of light olefin (C2′-C4′) selectivity were investigated on the RuMnLi/AlO Fischer-Tropsch synthesis catalysts in a low pressure fixed-bed reactor. The C2′-C4′ selectivities of RuMnLi/α-AlO and RuMnLi/β-AlO were a little higher than that of RuMnLi/γ-AlO. The difference seems to stem mainly from the crystallite sizes of metallic ruthenium, which is in the order: RuMnLi/γ-AlO > RuMnLi/β-AlO > RuMnLi/α-AlO, as evaluated from XRD, CO chemisorption and NH-TPD. The C3′ and 1-butene (1-C4′) were found to be predominantly formed over C2′ and, for C4, only n-butane and 1-C4′ were produced, but isobutane, isobutene and trans- or cis-2-butene were not formed, which is in sharp contrast with iron catalyst. Another reason for the improvement of C2′-C4′ selectivity is the Li effect, because, possibly, the secondary hydrogenation reaction of olefin intermediates could be suppressed on the Li-promoted catalyst. Thus, 50.2 % of C2′-C4′ selectivity was achieved at 300 °C and 0.5 MPa of CO/H using RuMnLi/α-AlO. [ABSTRACT FROM AUTHOR]

A series of modified MoS-supported catalysts was investigated for the synthesis of mixed alcohols from synthesis gas in a high-pressure gas-solid flow reaction system. AlO-pillared montmorillonite (denoted as AlO-Mont) was prepared by calcining [AlOAl(OH)(HO)]-pillared montmorillonite at 673 K in air. AlO-Mont was an excellent support for MoS in the synthesis of mixed alcohols from synthesis gas. The MoS/AlO-Mont catalyst showed a CO conversion of 34.6 % and a selectivity for alcohols of 33.5 % at 553 K under 8 MPa. By introducing 3 wt% K (one of the alkali metals) in MoS/AlO-Mont, the CO conversion increased to 40.5 % and the selectivity for alcohols increased to 41.9 % at 553 K under 8 MPa. Furthermore, by increasing 5 wt% Ni (one of Fischer-Tropsch metals) in KMoS/AlO-Mont, the CO conversion increased to 51.8 % and the selectivity for alcohols increased to 50.5 % at 553 K under 8 MPa. With increasing reaction temperature, the CO conversion and the ratio of C higher alcohols to methanol increased but the selectivity for total alcohols greatly decreased due to the formation of hydrocarbons over KNiMoS/Al-Mont under 8 MPa. With increasing reaction pressure, the CO conversion and the ratio of C higher alcohols to methanol increased while the selectivity for total alcohols was almost constant over KNiMoS/Al-Mont at 553 K. KNiMoS/Al-Mont showed a good catalytic stability in a feed gas containing 10 ppm HS but gradually deactivated in a clean feed gas due to losing sulfur component during the reaction. [ABSTRACT FROM AUTHOR]

Re-modified Pt/SiO 2–Al 2O 3 catalysts, which were active for the direct hydrotreating of jatropha oil into C 18 hydrocarbons, were found to be effective for glucose transformation into C 6 alkanes. At 350 °C and glucose/catalyst weight ratio of 2, the highest glucose conversion of 100 % was achieved with selectivity to C 6 alkanes of 57.1 %. The reaction pathway involves glucose hydrocracking to form C 6 polyols, followed by deoxyhydration and subsequent C=C bond hydrogenation by synergistic effect of Pt and Re. [ABSTRACT FROM AUTHOR]

Ethanol conversion to C3+ olefins, especially propylene, using Zr-modified H-ZSM-5 catalysts was investigated. Zr-modification to H-ZSM-5 zeolite could improve the initial yield of C3+ olefins and propylene and could reduce the initial yield of ethylene. In general, catalysts exhibiting the higher initial yield of propylene showed the steeper decrease in propylene yield as the reaction proceeded. However, Zr-modification to H-ZSM-5 could depress the decrease in propylene yield for aqueous ethanol. As cause of catalytic deactivation, carbon deposition on catalyst and framework collapse of zeolite support can be considered. The addition of water to Zr-modified H-ZSM-5 catalyst could depress carbon deposition in some degree, and, as a result, the decrease in propylene yield could be depressed. [ABSTRACT FROM AUTHOR]

Renewable green C2-C9 alkanes can be directly produced by Pt/H-ZSM-5-catalyzed hydrocracking of biomass-derived materials, no pre-treated or pre-treated by alcohol. The pre-treatment of cellulose in 1-hexanol at 623 K, followed by hydrocracking catalyzed by Pt/H-ZSM-5(23) at 673 K, produced C2-C9 alkanes in as high as 89% yields with CH/CO yields of only 6%. The reaction pathway involves lowering of molecular weight of cellulose materials, producing, probably, oxygenates intermediates such as mono-saccharide and disaccharide, which are further efficiently converted to alkane products by successive hydrocracking and condensation, catalyzed by Pt/H-ZSM-5. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Metal modification effects on ethanol conversion to propylene were examined by use of H-ZSM-5 with Si/Al ratio of 150. In La- and Mg-co-modified H-ZSM-5 (La/Al ratio: 1.0, Mg/Al ratio: 0.10), 32% propylene selectivity was obtained at 0.1 MPa, 550 °C. This value was higher than those of unmodified and La-modified (La/Al ratio: 1.0) H-ZSM-5. The number of acid sites and the acid strength (surface acidity) decreased in the order of unmodified, La-modified, and La- and Mg-co-modified H-ZSM-5. In the initial stage of ethanol introduction, ethylene production by dehydration of ethanol increased in La- and Mg-co-modified H-ZSM-5 with lower surface acidity, whereas the formation of aromatics by oligomerization-cracking increased in unmodified H-ZSM-5 with higher surface acidity. The propylene selectivity was 25% after 36.2 h in the La- and Mg-co-modified H-ZSM-5. The selectivity ratio of propylene to ethylene was 0.47 after 36.2 h; a rapid increase in ethylene formation was also depressed. Therefore, La- and Mg-co-modified H-ZSM-5 with Si/Al ratio of 150 was highly effective for the conversion of ethanol to propylene. [ABSTRACT FROM AUTHOR]

catalytic conversion of ethanol to propylene was carried out using H-ZSM-11. The highest propylene selectivity was obtained at Si/Al ratio of 120 and the value was 25% at 0.1 MPa, 550 °C. In W-modified H-ZSM-11, the ethylene production by the dehydration of ethanol was promoted by higher W/Al ratio, whereas C formation by the oligomerization-cracking was slightly decreased with an increase in the W/Al ratio. When the W/Al ratio was 1.0, 23% and over of propylene selectivity was kept for over 16 h at 500 °C. A rapid increase in ethylene formation was also depressed. W-modified H-ZSM-11 with Si/Al ratio of 120 was found to be highly effective for the conversion of ethanol to propylene. [ABSTRACT FROM AUTHOR]

A catalytic conversion of ethanol to propylene was carried out by use of H-ZSM-5 with Si/Al2 ratio of 280. In H-ZSM-5 modified at a molar ratio of La to Al2 of 2.2, the propylene selectivity was 31% at 0.1 MPa, 550 °C and was higher than those of non-modified and other metal modified catalysts. In the La-modified H-ZSM-5, a rapid increase in ethylene formation was also depressed and the propylene selectivity was still high (24%) even after 28 h-reaction. A catalytic conversion of ethanol to propylene was carried out by use of H-ZSM-5 with Si/Al2 ratio of 280. In H-ZSM-5 modified at a molar ratio of La to Al2 of 2.2, the propylene selectivity was 31% at 0.1 MPa, 550 °C and was higher than those of non-modified and other metal modified catalysts. In the La-modified H-ZSM-5, a rapid increase in ethylene formation was also depressed and the propylene selectivity was still high (24%) even after 28 h-reaction.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Polyoxocation ([AlO4Al12(OH)24(H2O)12]7+ and [Zr4(OH)14(H2O)10]2+)-pillared montmorillonites were prepared by ion exchange, and they were used as solid acid catalysts, in comparison to some other solid acids, for the selective hydrocracking of Fischer–Tropsch waxes to diesel-ranged hydrocarbons. XRD patterns and elemental analyses proved that the polyoxocations were successfully introduced into the interlayer region of the montmorillonites. N2 adsorption–desorption measurement indicated that polyoxocation-pillared montmorillonites have large BET surface areas (>230 m2 g−1), high thermal stability (>673 K), and large pores (comparing to those in zeolites). FT-IR spectra of chemisorbed pyridine indicated that polyoxocation-pillared montmorillonites possess both Lewis and Bronsted acid sites on the solid surface. Temperature-programmed desorption of ammonia indicated that the acidity strength of the polyoxocation-pillared montmorillonites was weaker than those of H–ZSM-5, H–Y, WO3/ZrO2, and Al2O3–SiO2. In the hydrocracking of Fischer–Tropsch (F–T) waxes, the acidity strength of the solid acids in bifunctional catalysts greatly influences the product composition. Pt-promoted H–Y afforded a high yield of gasoline-ranged hydrocarbons (>90%) while Pt-promoted H–ZSM-5 afforded a larger amount of gas products due to its strong solid acid sites. On the other hand, among various catalysts, Pt-modified polyoxocation-pillared montmorillonites afforded the highest yield of diesel-ranged hydrocarbons (>70%) due to the appropriately weak acid strength, high thermal stability, large BET surface area, and large pore size. Pt is necessary for the hydrocracking of F–T waxes because it enables hydrogenation/dehydrogenation. However, a high Pt loading on the catalyst produces more light hydrocarbons due to the stimulation of hydrogenolysis. High hydrogen pressure improved the selectivity for diesel-ranged hydrocarbons but decreased the conversion of F–T waxes due to the suppression of alkane dehydrogenation. The hydrocracking of F–T waxes at a low temperature with a large amount of catalyst for longer reaction time increased the yield of diesel-ranged hydrocarbons. [ABSTRACT FROM AUTHOR]

We have found that Zr- and Li-modified Ru/SiO2 catalysts (Q-15) are extremely stable and can be used in FT synthesis to maintain the conversion rate of CO constant even after 33 h. Modification of Ru/SiO2 by Zr (5 wt%) and Li (0.1 wt%) resulted in a remarkable increase in the stability of the catalyst. Taking into account surface acidity and reducibility, we assumed that this remarkable stability is due to the cooperative effects of Ru, Zr, Li, and the SiO2 support. [ABSTRACT FROM AUTHOR]

The activity of a H-ZSM5-90 for the dehydration of ethanol at 473 K increased with an increase in time on stream. The results of NH3-TPD and Ar adsorption showed that the number of acid sites of the H-ZSM5-90 increased during the dehydration. On the other hand, the activity and the number of acid sites of H-mordenite-90 were almost unchanged during the dehydration. Since the pre-treatment of the H-ZSM5-90 with ethylene at 473 K largely increased its activity for the dehydration of ethanol, it is suggested that a large number of new acid sites could be formed inside the pores of H-ZSM5-90 via the polymerization of ethylene produced by the dehydration of ethanol. [ABSTRACT FROM AUTHOR]

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 SiO2/Al2O3 ratio of 90 than with a SiO2/Al2O3 ratio of 20. [ABSTRACT FROM AUTHOR]

The dehydrogenation of propane over a silica-supported vanadium oxide catalyst was investigated at 823 K under atmospheric pressure in the presence/absence of CO2. The yield of propene and the selectivity to propene were higher in the dehydrogenation in the presence of CO2 than those in the dehydrogenation in the absence of CO2. On the other hand, the yield of aromatics and the selectivity to aromatics were much higher in the dehydrogenation in the absence of CO2 than those in the dehydrogenation in the presence of CO2. TPR measurements, NH3 desorption studies and in-situ UV–vis studies on the catalyst were also performed to elucidate the effects of CO2 on the behavior of the vanadium oxide in the catalyst during the dehydrogenation of propane. [ABSTRACT FROM AUTHOR]

The catalyst system consisting of Pd, transition metal-modified ZrO2 and acetic acid was found to catalyze the hydroxylation of benzene with molecular oxygen without hydrogen and phenol was formed. Of transition metals employed, only vanadium additive was found to be effective for improving the rate of phenol formation as well as the selectivity, while any other transition metals such as iron, molybdenym, tungsten and yttrium were not promotive. Support effects on vanadium were in the order: V/ZrO2> V/Al2O3> V/SiO2. The highest rate of phenol formation was obtained at 0.5wt%V/ZrO2 catalyst. Phenol selectivity was dramatically improved by the addition of sulfolane, while benzene conversion and STY of phenol formation decreased. It is assumed that Pd(II) and Pd(IV) intermediates derived from acetic acid, oxygen and palladium acetate could play an important role in hydroxylation of benzene. [ABSTRACT FROM AUTHOR]

The pre-treatment of a silica-supported gallium oxide catalyst with H2 at 823 K increased the yield of aromatics and the selectivity to aromatics in the dehydrogenation of propane over the catalyst at 823 K. Gallium oxide in the catalyst was partially reduced with H2 at 823 K. NH3 desorption and DRIFTS studies on the gallium oxide catalyst suggest that the dehydrogenation of propane over a silica-supported gallium oxide catalyst would proceed in the following way: (1) the dehydrogenation of propane to produce propene would occur on Ga sites including Gaδ+–H sites and (2) the aromatization of propene to aromatics on Ga–O–H acid sites. [ABSTRACT FROM AUTHOR]

The Pd(OAc)2/Ti—Al-HMS/CH3OH catalyst system showed 61.2% selectivity for PO at 42.8% propylene conversion for the oxidation of propylene with molecular oxygen in an autoclave reactor at 373 K for 4 h. The catalyst is reusable using the filtration method or the vacuum distillation method after reaction. It is likely that a Ti cyclic peracid-like intermediate was formed in the system made up of a Ti site, an oxygen molecule and a methanol molecule. The Pd species activates the oxygen molecule and the Al site plays a role for stabilizing the Ti cyclic peracid-like intermediate to improve the yield of propylene oxide from the oxidation of propylene with molecular oxygen. [ABSTRACT FROM AUTHOR]

The dehydrogenation of propane over a silica-supported gallium oxide catalyst was investigated at temperatures ranging from 793 to 853 K under atmospheric pressure. The catalyst was found to be moderately active and highly selective to propene in the dehydrogenation of propane. The amount of carbonaceous deposits on the catalyst in the dehydrogenation was around 1/10th of that on a silica-supported chromium oxide catalyst. Lower reaction temperatures and lower concentrations of propane in the feed would be favorable for selective production of propene. [ABSTRACT FROM AUTHOR]

The stability of an Fe/AlO catalyst in the methane decomposition in the presence of O/CO was found to be improved by the addition of Mg into the catalyst (Mg/Fe=1/1 wt ratio), probably due to suppression of carbon deposition even under CH/ O/CO (80/10/5 vol. ratio) conditions. [ABSTRACT FROM AUTHOR]

Ti- and Al-containing hexagonal mesoporous silicas (HMS) were synthesized at ambient temperature using dodecylamine as surfactant, and the resultant compounds were used as catalysts for the oxidation of propylene by molecular oxygen. Ti-Al-HMS, which was prepared by reaction of Ti(iso-OC3H7)4, Al(iso-OC3H7)3 and SiOC2H5)4 in an alcohol-aqueous solution in the presence of dodecylamine, showed 47.8 of conversion and 30.6 of selectivity for propylene oxide (PO) at 523K. The yield of PO over Ti-Al-HMS (14.6) was much higher than those over Ti-HMS (1.3) and Al-HMS (0.9) at the same reaction conditions. Ti-Al-HMS was also found to be more effective for PO formation than the supported catalysts (Ti/Al-HMS and Al/Ti-HMS) prepared by impregnation method. These results indicated that the simultaneous existence of Ti and Al in HMS was very important for improving the yield of PO from the oxidation of propylene, and the synthesis method influenced the catalytic activity of the Ti- and Al-containing HMS catalysts. [ABSTRACT FROM AUTHOR]

Dehydrogenation and isomerization of n-butane or isobutane into isobutene over Cr catalysts supported on zeolites were investigated. We found that Cr catalyst supported on H-SSZ-35-type zeolite, having one-dimensional cage-type channel structure, was very effective for this reaction and the yield of isobutene was 5.44% from n-butane and 9.57% from isobutane. In this reaction, it is suggested that dehydrogenation of butanes is accelerated by Cr2O3 loading, and solid acidity of the zeolite support favors isomerization. [ABSTRACT FROM AUTHOR]

Hydrogen production by conversion of methane over Ni-supported zeolite catalysts was investigated, and Ni-supported USY-type zeolite (Si/Al = 14.0, 360) was found to have longer catalytic lifetime than Ni-supported silica (Cab-O-Sil) catalyst, which had been reported to have the longest catalytic lifetime for this reaction. [ABSTRACT FROM AUTHOR]

The effects of the pretreatments of Cu/ZnO-based catalysts prepared by a coprecipitation method on their activities for the water–gas shift reaction at 523K were investigated. The activity of a Cu/ZnO/ZrO2/Al2O3 catalyst for the water–gas shift reaction was less affected by calcination at temperatures ranging from 673-973K and by H2 treatment at 573 or 723K than that of a Cu/ZnO/Al2O3 catalyst. The catalyst activity could be correlated mainly to the Cu surface area of the catalyst. [ABSTRACT FROM AUTHOR]