Applied Catalysis A, General (v.348, #2)
Editorial Board (CO2).
Microstructural characterization of Cu/ZnO/Al2O3 catalysts for methanol steam reforming—A comparative study by Patrick Kurr; Igor Kasatkin; Frank Girgsdies; Annette Trunschke; Robert Schlögl; Thorsten Ressler (153-164).
The microstructure of Cu/ZnO/Al2O3 catalysts for methanol steam reforming was investigated and compared to structure–activity correlations of binary Cu/ZnO model catalysts. Similar to the binary system, characteristic defects (e.g. lattice strain) in the Cu phase of Cu/ZnO/Al2O3 catalysts are indicative of a homogeneous microstructure and superior catalytic performance. ▪Microstructural characteristics of various real Cu/ZnO/Al2O3 catalysts for methanol steam reforming (MSR) were investigated by in situ X-ray diffraction (XRD), in situ X-ray absorption spectroscopy (XAS), temperature programmed reduction (TPR) and electron microscopy (TEM). Structure–activity correlations of binary Cu/ZnO model catalysts were compared to microstructural properties of the ternary catalysts obtained from in situ experiments under MSR conditions. Similar to the binary system, in addition to a high specific copper surface area the catalytic activity of Cu/ZnO/Al2O3 catalysts is determined by defects in the bulk structure. The presence of lattice strain in the copper particles as the result of an advanced Cu–ZnO interface was detected only for the most active Cu/ZnO/Al2O3 catalyst in this study. Complementarily, a highly defect rich nature of both Cu and ZnO has been found in the short-range order structure (XAS). Conventional TPR and TEM investigations confirm a homogeneous microstructure of Cu and ZnO particles with a narrow particle size distribution. Conversely, a heterogeneous microstructure with large copper particles and a pronounced bimodal particle size distribution was identified for the less active catalysts. Apparently, lattice strain in the copper nanoparticles is an indicator for a homogeneous microstructure of superior Cu/ZnO/Al2O3 catalyst for methanol chemistry.
Keywords: Methanol steam reforming; Cu/ZnO/Al2O3 catalyst; Hydrogen production; Homogeneous microstructure; Cu lattice strain; TPR; TEM; XRD; XAS; In situ;
Catalytic partial oxidation of methane on rhodium and platinum: Spatial profiles at elevated pressure by A. Bitsch-Larsen; R. Horn; L.D. Schmidt (165-172).
Under pressure: Spatially resolved species and temperature profiles inside foam monoliths have been investigated. This has been done under catalytic partial oxidation conditions of methane over Rh- and Pt-coated catalysts at pressures up to 1.1 MPa. Our results show that the Rh catalyst is governed by mass transfer limitations, while the Pt is kinetically controlled.▪Catalytic partial oxidation (CPO) of methane is a potential technology for conversion of methane into synthesis gas, because the process operates autothermally with millisecond residence times and at high temperatures ( > 800 ° C) with no external heating. In an industrial setting, it is required to operate the process at elevated pressure. In this work we present spatially resolved data on the effect of pressure on CPO of methane on Rh- and Pt-coated foams from 0.1 to 1.1 MPa total pressure. There is little effect of pressure over Rh on rate at constant mass flow rate, which can be explained by mass transfer limitations. At constant linear inlet velocity the oxidation zone is extended with increasing pressure, again in accordance with mass transfer limitations. On Pt increasing pressure at constant mass flow rate leads to faster oxygen consumption and higher H2 production because of higher operating temperature and longer residence times. Catalyst deactivation was not observed for Rh, but initial deactivation was observed for Pt.
Keywords: Catalytic partial oxidation; Methane; Rhodium; Platinum; Pressure;
Influence of hydrothermal aging on the catalytic activity of sulfated zirconia by Mariana Busto; Kiyoyuki Shimizu; Carlos R. Vera; Javier M. Grau; Carlos L. Pieck; Miguel A. D’Amato; M.T. Causa; M. Tovar (173-182).
The use of reflux aged sulfated zirconia for isomerization of n-butane and isomerization-cracking of long paraffins was assessed. Though hydrothermal aging of the gel greatly improved the specific surface area and other textural properties, sulfate promotion of aged gels produced materials with poor activity in both test reactions. A dissolution-precipitation process present during aging was thought to eliminate gel sites responsible for much of the activity of the final catalyst. ▪The use of reflux aged zirconia gel in the synthesis of sulfated zirconia catalysts for isomerization of short paraffins and isomerization-cracking of long paraffins was assessed. It was found that reflux aging greatly improved zirconia textural properties. The growth of the monoclinic phase was greatly suppressed and the initial area and sintering resistance were increased. The specific surface area of reflux aged material with no sulfate was almost 75 m2 g−1 after calcination at 800 °C. Sulfate promotion of aged materials further increased the tetragonal/monoclinic ratio and the area of sulfated catalysts was 220 m2 g−1 after calcination at 600 °C.Impregnation of reflux aged materials with sulfate produced materials which had very low activity in isomerization of n-butane. The effect of aging was explained in terms of a dissolution-precipitation process that eliminated specific sites of the gel that were responsible for much of the activity of the final catalyst. In the case of the hydroisomerization-cracking of long paraffins the effect was less deletereous partly due to the higher reactivity of this feedstock.
Keywords: Reflux aging; Sulfated zirconia; n-Butane isomerization; n-Octane isomerization-cracking;
Partial oxidation and autothermal reforming of methane on Pd/CeO2–Al2O3 catalysts by L.S.F. Feio; C.E. Hori; L.V. Mattos; D. Zanchet; F.B. Noronha; J.M.C. Bueno (183-192).
Pd/Al2O3 catalyst was strongly deactivated during partial oxidation or autothermal reforming of methane, while CeO2-containing catalysts exhibited higher stability for high CeO2 loading. The activity and stability apparently decrease with Pd dispersion. This fact was ascribed to partial coverage of Pd by [CePd x O]Pd0-like species, which result in a higher accessibility of the active sites to methane. ▪The surface properties and catalytic behavior of Pd/xCeO2–Al2O3 catalysts in partial oxidation of methane and autothermal reforming of methane were investigated. There was an increase on ceria's apparent crystallite sizes with the increase of CeO2 loadings and with the rise of the calcination temperatures of the supports from 500 to 900 °C. A decrease on the density of Pd sites was observed with the use of supports calcined at lower temperature and with the increase of CeO2 loadings. However, CO linearly bonded/CO bridged bonded intensity ratios showed an opposite trend. This apparent disagreement could be due to the partial coverage of Pd sites by CeO x species. Pd/Al2O3 catalyst was strongly deactivated during partial oxidation or autothermal reforming of methane, while catalysts with higher ceria loadings exhibited superior stability. Pd/xCeO2–Al2O3 catalysts show an increase of activity for autothermal reforming of methane with the increase of CeO2 loading. Therefore, the activity and stability apparently decrease with Pd dispersion. This fact was ascribed to partial coverage of Pd by [CePd x O]Pd0 species, which show high ability to promote the gasification of coke. The formation of [CePd x O]Pd0 species results in a decrease of the density of Pd sites but led to higher accessibility of the active sites to methane.
Keywords: Partial oxidation of methane; Autothermal reforming of methane; Pd/Ce–Al2O3 catalysts; CeO2; Palladium on alumina; CO adsorption;
The influence of metals and acidic oxide species on the steam reforming of dimethyl ether (DME) by Tetsuya Fukunaga; Naonori Ryumon; Shogo Shimazu (193-200).
A comparative study of various Cu-based catalysts was performed on the steam reforming reaction of dimethyl ether (DME). Ru/Al2O3 showed very high CH4 production, irrespective of the presence of acidic sites, due to the high intrinsic methanation activity of Ru metal. In contrast, Cu-based catalysts did not produce CH4 as a by-product when mixed with acidic oxides such as Al2O3. CuMn-spinel + Al2O3 was superior to commercial CuZnAl + Al2O3, exhibiting higher DME conversion at a lower temperature. Replacing Al2O3 with a zeolite led to a further increase in activity. The higher performance of the CuMn-spinel catalyst can be attributed to its high methanol steam reforming activity. Thus, the activity and selectivity of this process strongly depend on the identity of the metals and acidic oxide species employed.▪The performance of catalysts from the platinum group and Cu-based catalysts were compared in the dimethyl ether (DME) steam reforming reaction.Without acidic oxides, Cu-based catalysts formed undesired CH4 via a direct decomposition of DME into methoxy (–OCH3) and methyl (–CH3) groups, followed by the hydrogenation of the methyl group to CH4. However, in the presence of acidic oxides such as Al2O3, practically no CH4 was produced. Therefore we speculate that the MeOH formed on the acidic sites moves onto Cu and is adsorbed as a methoxy group without the co-formation of a methyl group, preventing the formation of CH4 and leading to an even higher yield of H2.Pt/Al2O3 and Ru/Al2O3 showed a relatively high DME conversion, although the undesired production of CH4 was quite high, irrespective of the presence of acidic sites. A high CH4 selectivity can be explained in terms of a high methanation activity.The catalyst formed from CuMn2O4 spinel oxide mixed with Al2O3 showed higher activity and greater durability than commercial CuZnAl catalysts mixed with Al2O3. By replacing Al2O3 with H-ZSM5, the CuMn2O4 spinel oxide showed a further increase in activity resulting in up to 100% conversion even under 300 °C. We attribute this very high activity at relatively low temperature to both the high DME hydration activity of H-ZSM5 and the high MeOH steam reforming activity of CuMn2O4 spinel oxide.
Keywords: Cu-spinel; Platinum group metal; Steam reforming; Dimethyl ether; Hydrogen;
Effect of Mg, La and Ca promoters on the structure and catalytic behavior of iron-based catalysts in Fischer–Tropsch synthesis by Ali Nakhaei Pour; Seyed Mehdi Kamali Shahri; Hamid Reza Bozorgzadeh; Yahya Zamani; Ahmad Tavasoli; Mehdi Ahmadi Marvast (201-208).
Mg, La and Ca promoters affect the structure and surface area on the reduction, carburization and catalytic behavior of precipitated Fe/Cu/SiO2 Fischer–Tropsch synthesis (FTS) catalysts were investigated. It is found that Mg, La and Ca promoters have negligible effect on the textural properties and the addition of these promoters can enhance the surface basicity of the catalyst in the order of Ca > Mg > La. An appropriate amount of these promoters in atomic ratio X/Fe = 0.02 (X = Ca, Mg and La) can promote the reduction and carburization of the catalysts during the reduction and Fischer–Tropsch synthesis reaction in the order of Ca > Mg > La. Presented promoters can inhibit the ability of catalysts hydrogenation in the order of Ca > Mg > La. The results also indicate that an appropriate amount of these promoters can improve the CO conversion and WGS reaction, suppress the formation of methane, enhance the selectivities to olefin and higher molecular weight products, amplify the break down in ASF distributions in the order of Ca > Mg > La because of rising the catalyst surface basicity and dropping the catalyst reducibility. ▪The effects of Mg, La and Ca promoters on the structure, surface area, reduction, carburization and catalytic behavior of precipitated Fe/Cu/SiO2 Fischer–Tropsch synthesis (FTS) catalysts were investigated. The catalysts are characterized using X-ray diffraction (XRD), H2 and CO temperature-programmed reduction (TPR) techniques. The catalysts were assessed in terms of their FTS activity and product selectivity using two superimposed Anderson–Schulz–Flory (ASF) models. The performance of the catalysts was tested in a fixed-bed reactor at 563 K, 1.7 MPa and feed (syngas with H2/CO molar ratio of 1) flow rates of 4.9 and 13.3 nl h−1 g(Fe)−1. It was found that Mg, La and Ca promoters have negligible effects on the textural properties of the catalyst. Promoter addition enhanced the surface basicity of the catalyst in the order Ca > Mg > La. Addition of the promoters with the atomic ratio of X/Fe = 0.02 (X = Ca, Mg and La) improved the reduction and carburization during the reduction and FTS reaction in the order of Ca > Mg > La. The promoters suppressed the rate of hydrogenation reaction in the order of Ca > Mg > La. The results also indicate that Mg, La and Ca promoters can improve the CO conversion and WGS reaction, suppress the formation of methane, enhance the selectivities to olefin and higher molecular weight products, enhance the break in ASF distributions in the order of Ca > Mg > La due to increasing the catalyst surface basicity and dropping the reducibility.
Keywords: Ca promoter; Mg promoter; La promoter; Fischer–Tropsch synthesis; Iron-based catalyst;
Surface analysis of Pd/ZnO catalysts dispersed on micro-channeled Al-foils by XPS by K. Dumbuya; R. Denecke; H.-P. Steinrück (209-213).
X-ray photoelectron spectroscopy (XPS) investigation of non-activated and activated Pd/ZnO catalysts dispersed on micro-channeled Al-foil reveals that the former is composed of PdO, while the latter comprises mainly PdZn and ∼30% metallic Pd in the surface region. The fraction of Pd metal was completely converted to PdZn in the activated catalyst following heating to 600 K in UHV. PdO species in the non-activated sample were reduced to the metal in the same temperature range. Mg segregation occurred above 700 K in both samples. ▪We have investigated the surface composition of Pd/ZnO catalysts dispersed on micro-channeled Al-foils in a non-activated and in the activated state, between 300 and 700 K using X-ray photoelectron spectroscopy (XPS). While the surface of the non-activated catalyst, as obtained after calcination, is composed of PdO, the surface of the activated (reduced) catalyst consists of predominantly PdZn and ∼30% metallic Pd. When increasing the temperature up to 700 K in UHV significant structural surface changes were observed for both samples. For the non-activated sample, PdO was reduced mainly to the Pd metal with some fraction of PdZn alloy. For the activated catalyst, the fraction of metallic Pd was also converted to PdZn, yielding a pure alloy, which is stable to at least 600 K. At 700 K both samples show changes due to segregation of Mg from the micro-channeled Al-foils onto which the powdered catalysts were deposited, which contains 3% Mg.
Keywords: Pd/ZnO catalyst; PdZn; Methanol steam reforming; X-ray photoelectron spectroscopy; Mg enrichment;
OMS-2 catalyzed oxidation of tetralin: A comparative study of microwave and conventional heating under open vessel conditions by Shanthakumar Sithambaram; Edward K. Nyutu; Steven L. Suib (214-220).
Oxidation of tetralin with OMS-2 catalysts under conventional and microwave conditions are compared. Significant differences were found in conversion and product distribution when experiments performed at the same reaction conditions. The characterization of catalysts before and after reactions using XRD, SEM and Raman are reported.▪Microwave heating as an alternative to conventional heating for K-OMS catalyzed oxidation of tetralin under atmospheric pressure conditions has been described. The conversions and selectivities obtained by microwave and conventional heating are compared for K-OMS-2 catalysts. Significant differences were found in conversion and product distribution when comparing the conventional and microwave heated experimental results performed under the same reaction conditions. Conversions up to 88% and turnover frequencies up to 20 were achieved under microwave irradiation. The major products of oxidation of tetralin were tetralone and tetralol (>75%). In addition, the effects of using different solvent systems in the reactions were studied. The characterization of catalysts before and after the reactions using XRD, SEM, and Raman are reported.
Keywords: Microwave irradiation; Oxidation; Manganese octahedral molecular sieves; Hydrocarbons; Open vessel;
Partial oxidation of methane over Pt–Ru bimetallic catalyst for syngas production by R. Lanza; P. Canu; S.G. Järås (221-228).
A bimetallic catalyst (Pt–Ru 50/50) has been prepared for methane partial oxidation. Total metal load was 1 wt%. The support was alumina mixed with 25 wt% of a ceria–zircona mixture. This because of the good performances of alumina for such applications and to exploit the oxygen buffer effect of the ceria–zirconia system. The catalyst has been prepared by incipient wetness and characterized by means of XRD, BET surface area, TPR/TPO and SEM–EDS analyses. It showed good activity and high selectivity towards CO and H2, produced in a ratio suitable for Fisher–Tropsch applications. The effect of spatial velocity (GHSV) has been investigated; ramping temperature up and down, some hystersis has been evidenced, especially at the highest GHSV, mainly caused by thermal effects. Overall, 100% conversion of methane to H2 and CO in the appropriate syngas ratio (2/1) can be easily and stably achieved.▪A bimetallic catalyst (Pt–Ru 50/50) has been prepared for methane partial oxidation. Total metal load was 1 wt%. The support was alumina mixed with 25 wt% of a ceria–zirconia mixture. This because of the good performances of alumina for such applications and to exploit the oxygen buffer effect of the ceria–zirconia system. The catalyst has been prepared by incipient wetness and characterized by means of XRD, BET surface area, TPR/TPO and SEM–EDS analyses. It showed good activity and high selectivity towards CO and H2, produced in a ratio suitable for Fisher–Tropsch applications. The effect of spatial velocity (GHSV) has been investigated; ramping temperature up and down, some hysteresis has been evidenced, especially at the highest GHSV, mainly caused by thermal effects. Overall, 100% conversion of methane to H2 and CO at the appropriate syngas ratio (2/1) can achieved easily and with stability.
Keywords: Methane; Partial oxidation; Catalytic; Platinum; Ruthenium; Bimetallic; Syngas; Hysteresis; Activity;
Reforming of methane, ethylene, and desulfurized kerosene over Ni-8YSZ catalyst by Yohei Tanaka; Tohru Kato (229-235).
Catalytic activity for reforming of CH4, C2H4, and kerosene were investigated over a Ni-8YSZ catalyst from the viewpoint of space velocity. At temperatures higher than 650 °C, a thick Ni-8YSZ layer exhibited a high catalytic activity for reforming of methane, ethylene, and kerosene of which gas concentration was less than 1%. On the other hand, thin anode layer will require some modification of the catalytic activity. Steam reforming of kerosene over Ni-8YSZ may be possible at high steam-to-carbon ratio and high temperatures. ▪For solid oxide fuel cell (SOFC) systems fueled by kerosene, reforming of methane, ethylene, and desulfurized kerosene was investigated over Ni-8YSZ catalyst at 750 °C and steam-to-carbon ratio (S/C) = 3 as a function of gas hourly space velocity (GHSV). At temperatures higher than 650 °C, a thick Ni-8YSZ layer exhibited a high catalytic activity for reforming of methane, ethylene, and kerosene of which gas concentration in a pre-reformate gas was less than 1%. On the other hand, thin anode layer will require some modification of the catalytic activity. Carbon was formed as particles in the inlet quartz wool via pyrolysis of ethylene at flow-stagnation points, which will cause pore closure in Ni-anode catalysts. This type of carbon formation would bring about inhomogeneous flow-and-voltage distribution in a cell. Direct feed of steam and kerosene to Ni-8YSZ was examined at GHSV = 2400 h−1, S/C = 3 and 550–750 °C. Gas composition analysis and FTIR spectra indicate that high kerosene conversion (≥95%) could be attained at 650–750 °C over Ni-8YSZ assuming relatively thick Ni-anode layer. The catalytic activity was deteriorated at lower temperatures. Clear carbon deposition on Ni-8YSZ or inlet quartz wool was not observed on the experimental condition. The direct feeding system may be possible only at high temperatures and high S/C. As long as a temperature of anode-supported SOFCs is kept over 650 °C, small amount of methane, ethylene, and kerosene will not harm performance of the SOFCs.
Keywords: Reforming; Space velocity; Methane; Ethylene; Kerosene; Ni-8YSZ;
Metal halide catalysts to synthesize dichloropentafluoropropanes by the reaction of dichlorofluoromethane with tetrafluoroethylene by T. Tanuma; H. Okamoto; K. Ohnishi; S. Morikawa (236-240).
A series of metal halides were studied as Lewis acid catalysts for the reaction of dichlorofluoromethane with tetrafluoroethylene to form dichloropentafluoropropanes (HCFC-225s) which are being manufactured as an alternative to CFC-113. Zirconium tetrachloride and hafnium tetrachloride had high catalytic activity in the reaction and much better selectivity towards HCFC-225ca and HCFC-225cb than conventional aluminum trichloride. The Cl-F exchange reaction of zirconium tetrachloride or titanium tetrachloride with chlorofluoromethane produced metal chlorofluorides. When chlorofluoromethane-treated ZrCl4 or TiCl4 were used as a catalyst the reaction of dichlorofluoromethane with tetrafluoroethylene proceeded without the induction period that was observed using ZrCl4 or TiCl4 without pretreatment, indicating that the metal chlorides needed an activation time to become chlorofluorides before developing catalytic activity. Trichlorofluoromethane-treated ZrCl4, metal chlorofluoride, was characterized by thermogravimetry (TG), differential thermal analysis (DTA), and X-ray diffraction.
Keywords: Lewis acid catalyst; Titanium; Zirconium; Halide; Chlorofluoride; Dichloropentafluoropropane; HCFC;
Effect of nickel precursor and the copper addition on the surface properties of Ni/KL-supported catalysts for selective hydrogenation of citral by Jesús Álvarez-Rodríguez; Miriam Cerro-Alarcón; Antonio Guerrero-Ruiz; Inmaculada Rodríguez-Ramos; Adolfo Arcoya (241-250).
Effect of the Ni precursor and of the copper addition on the properties of Ni/KL-supported catalysts was studied by TPR, H2 chemisorption, N2 adsorption, CO-FTIR and CO adsorption microcalorimetry. Characterization measurements of catalysts prepared from nickel (II) nitrate hexahydrate, nickel (II) acetylacetonate and nickel (II) phthalocyanine, respectively, show different nickel species distribution in the zeolite, with electron rich metal particles inside the lattice. For NiCu/KL bimetallic catalysts, combined studies by CO-FTIR and by CO adsorption microcalorimetry, together with the TPR results, provide evidence of formation of bimetallic nanoparticles with alloy type structure. The contribution of this species to the surface composition of the catalysts depends on the respective Ni/Cu atomic ratio. Encapsulation of part of the metal components in the zeolite channels and formation of segregated copper particles were also found. Results in the hydrogenation of citral at 323 K in the liquid phase evidence a positive relationship of the catalytic activity with the population of electron rich metal species on the monometallic catalysts. Copper inhibits the hydrogenation activity of nickel and modifies the structure of the exposed nickel surface, which affects the stability of the catalysts and the selectivity for the competitive hydrogenation of conjugated C＝C and C＝O bonds of the citral molecule.Effects of the metal precursor and of the copper addition in Ni/KL catalysts were analyzed. Both variables affect the nature and location of the metal species formed, as evidenced by the BET, TPR, FTIR-CO and microcalorimetry results, which results in a significant modification of the catalytic performances in the hydrogenation of citral in the liquid phase. Copper inhibits the initial activity of nickel catalysts but improve their stability and modifies the selectivity toward the reaction products.▪
Keywords: KL-zeolite; Ni catalysts; NiCu catalysts; Surface alloy; CO microcalorimetry; FTIR spectroscopy; Citral hydrogenation;
Characteristics of iron oxide/activated carbon nanocomposites prepared using supercritical water by Chunbao Xu; Amyn S. Teja (251-256).
The properties of nanocomposites obtained by depositing iron oxide nanoparticles in the pores of two types of commercial activated carbon pellets using supercritical water were studied as a function of process variables. The loading of iron oxide nanoparticles in the nanocomposites increased with precursor concentration and immersion time, but was apparently unaffected by the temperature. The specific surface area and pore volume of the nanocomposites decreased with increased loading of the nanoparticles, possibly due to pore blockage and/or pore destruction resulting from acid attack during processing. The results suggest that an optimum loading of nanoparticles in the nanocomposites can be achieved by manipulating pellet dimensions, precursor concentration, and immersion time.The deposition of iron oxide nanoparticles in activated carbon pellets, and the morphological characteristics of the resulting nanocomposites, were investigated for a supercritical deposition process. The loading increased with several process variables. However, the specific area and pore volume decreased when the loading capacity increased, which suggests that an optimum loading capacity may be achieved in the supercritical process.▪
Keywords: Supercritical water; Activated carbon; Iron oxide; Nanocomposite;
Synthesis and characterization of conventional and mesoporous Ga-MFI for ethane dehydrogenation by Karen Thrane Leth; Anne Krogh Rovik; Martin Spangsberg Holm; Michael Brorson; Hans J. Jakobsen; Jørgen Skibsted; Claus Hviid Christensen (257-265).
Gallium was for the first time incorporated into the crystal structure of a mesoporous MFI zeolite. As a reference material, a well-defined conventional MFI zeolite with gallium incorporated was also synthesized. The materials were characterized by XRPD, NH3-TPD, elemental analysis, N2 physisorption measurements, SEM, FT-IR as well as 29Si and 71Ga MAS NMR spectroscopy. The Ga contents correspond to molar ratios of Si/Ga = 43 and 38 for the conventional and mesoporous Ga-MFI, respectively. The different types of analysis show that two almost identical zeolites were synthesized, the main difference being the morphology of the crystals. The catalytic properties of the samples were tested in ethane dehydrogenation at 823 K and at atmospheric pressure. The two Ga-MFI samples differ greatly in conversion of ethane, as a result of their difference in porosity, and it is found that the conversion is significantly improved by introducing mesopores into the structure. The major product is ethene for the conventional Ga-MFI, but there are significant amounts of benzene and toluene by-products for the mesoporous Ga-MFI. The 71Ga isotropic chemical shift and second-order quadrupolar effect parameter is reported for tetrahedral Ga incorporated in the MFI structure and it is shown that absorbed water molecules have an important impact on the 71Ga electric field gradients and thereby on the quantitative evaluation of the 71Ga MAS NMR intensities.
Keywords: Ga-MFI zeolites; Mesoporous; Ethane dehydrogenation; Aromatization; 71Ga MAS NMR;
Heterogeneous catalysts for the production of new lubricants with unique properties by Hans Schuster; Louis A. Rios; Patrick P. Weckes; Wolfgang F. Hoelderich (266-270).
The heterogeneously catalyzed nucleophilic addition of carboxylic acid to the epoxide center in the epoxidized methyl-cis-9-octadecenoate (eOME) was attempted and the lubricant properties of the resulted hydroxy esters are reported. It is demonstrated that solid acid catalysts like Nafion, Nafion–silica composites (SAC), Amberlyst 15, Amberlite IR 120, zeolite H-Y and montmorillonite were promising and selective catalysts for hydroxy ester formation at reaction temperature 30 °C. The lubricant properties of various hydroxy esters were evaluated by rotary bomb testing, which indicates higher oxidation stability of the hydroxyl di esters than the starting material, methyl oleate. The viscosity index calculation shows that the viscosities of the hydroxy esters are significantly influenced by the size of the carbon chain and nature of the carboxylic acid.The heterogeneously catalyzed nucleophilic addition of carboxylic acids to epodized methyl-cis-9-octadecenoate (eOME) was investigated. Solid acid catalysts like Nafion, Nafion/silica composites, Amberlyst, Amberlite, zeolite Y and montmorillonite were used. Taking into consideration catalyst stability and cost-efficiency, the best results were obtained with Amberlyst 15. Lubricant properties of the resulting fluids were tested. The carbon chain length of the carboxylic acid used influenced the oils viscosity.▪
Keywords: Methyl oleate; Epoxide; Hydroxy ester; Nafion silica composites; Heterogeneous catalysis; Renewable feedstock; Rapeseed oil;