Applied Petrochemical Research (v.3, #3-4)
Perspective on FCC catalyst in China by Rui Feng; Ke Qiao; You-he Wang; Zi-feng Yan (63-70).
This paper provides an overview of the enormous challenge in processing heavier fluid catalytic cracking (FCC) feedstock and producing higher qualified liquid fuels. Besides optimizing the operation conditions of the FCC unit, it is crucial to design new catalysts especially for heavier and inferior feedstock. In this paper, a new concept, stepwise structure of catalyst, was postulated and a potential new catalyst based on stepwise structure design was prepared.
Keywords: Fluid catalytic cracking; Heavy oil; Catalyst; Zeolite
High alcohol synthesis (HAS) from syngas over supported molybdenum carbide catalysts by Hamid Al-Megren; Tiancun Xiao; Mohammad AlKinany; Saud Aldree; Yu Huang; Haoyi Chen; Peter P. Edwards; Vladimir Kuznetsov (71-77).
In this work, different kinds of supported molybdenum carbide catalysts have been prepared using temperature programmed carburization method with 20 vol% CH4/H2. Cobalt and potassium were later loaded over the resultant carbides. The catalysts were evaluated on the new alcohols test rig under 70 bar pressure with syngas feed gas with a H2/CO ratio of 2.0 at various temperatures. The carbide catalysts supported over boron-modified Al2O3 produced higher alcohols in significant yields. The best catalyst achieved 46.7 % selectivity to alcohol at 31.8 % conversion of CO. This corresponds to 199.7 g/alcohol/liter of catalyst/hour. In addition, 72.5 % selectivity to alcohol (93.1 % on CO2 free basis) was achieved at lower temperature with a conversion of 14.1 %. Characterization results showed that the boron-modified supports result in smaller molybdenum carbide crystallite size which might be responsible for the high activity. Higher potassium content benefits the high alcohol selectivity, but affects the catalyst activity to some extent.
Keywords: Higher alcohol synthesis; Supported molybdenum carbide; Syngas
Noble metal ion-substituted ceria as efficient oxygen storage catalysts for clean combustion of fuels by Rajagopalan Vijayaraghavan (79-82).
Three-way catalysts, a component of automobile converters, can control auto exhaust emissions by its capacity of converting CO, un-burnt hydrocarbon and oxides of nitrogen (NO x ) into less harmful CO2, H2O and N2 simultaneously. This process is efficient only when the A/F ratio is at 14.7. To widen the ratio for better chemical control, oxygen storage catalysts (OSC) based on CeO2, capable of three-way action, are employed in converters along with conventional catalysts. In this article, the enhanced activity of noble metal ion incorporated/dispersed CeO2 catalysts towards three-way action over conventional metal particles dispersed (in a matrix) catalysts is illustrated. The better performance of the metal ion dispersed catalysts is attributed to better dispersion of active metal ion sites over the reducible matrix like CeO2, leading to many-fold increase in the number of active sites.
Keywords: Oxygen storage capacity; Pd2+/CeO2 catalysts; CO oxidation; XPS; Temperature programmed reduction
Comparing Pt/SrTiO3 to Rh/SrTiO3 for hydrogen photocatalytic production from ethanol by A. K. Wahab; T. Odedairo; J. Labis; M. Hedhili; A. Delavar; H. Idriss (83-89).
Photocatalytic hydrogen production from ethanol as an example of biofuel is studied over 0.5 wt% Rh/SrTiO3 and 0.5 wt% Pt/SrTiO3 perovskite materials. The rate of hydrogen production, rH2, over Pt/SrTiO3 is found to be far higher than that observed over Rh/SrTiO3 (4 × 10−6 mol of H2 g catal. −1 min−1 (1.1 × 10−6 mol of H2 m catal. −2 min−1) compared to 0.7 × 10−6 mol of H2 g catal. −1 min−1 (5.5 × 10−8 mol of H2 m catal. −2 min−1), respectively, under UV excitation with a flux equivalent to that from the sun light (ca. 1 mW cm−2). Analyses of the XPS Rh3d and XPS Pt4f indicate that Rh is mainly present in its ionic form (Rh3+) while Pt is mainly present in its metallic form (Pt0). A fraction of the non-metallic state of Rh in the catalyst persisted even after argon ion sputtering. The tendency of Rh to be oxidized compared to Pt might be the reason behind the lower activity of the former compared to the later. On the contrary, a larger amount of methane are formed on the Rh containing catalyst compared to that observed on the Pt containing catalyst due to the capacity of Rh to break the carbon–carbon bond of the organic compound.
Keywords: Ethanol-photoreaction; XPS Rh3d; XPS Pt4f; Hydrogen production; Perovskite materials; Band gap; SrTiO3Carbon–carbon bond dissociation
Comparative study of the dry reforming of methane on fluidised aerogel and xerogel Ni/Al2O3 catalysts by Zheng Jiang; Xin Liao; Yongxiang Zhao (91-99).
The xerogel and aerogel Ni(20 wt %)/Al2O3 catalysts were prepared through incipient-wetness-impregnation and co-precipitation-supercritical drying (CP-SCD), respectively. All the fresh and used catalysts were well characterised using FESEM, BET, XRD, H2-TPR and H2-TPD techniques. Their properties and catalytic performance in dry reforming of CH4 in a fluidised bed reactor were comparatively investigated. In comparison with the xerogel catalyst, the aerogel catalyst possessed smaller crystallite size of nickel, larger specific surface area, higher nickel dispersion, lower bulky density and better fluidization quality. More importantly, the aerosol catalyst showed higher catalytic activity, stability and less carbon deposition in dry reforming, due to the excellent physicochemical properties of the aerogel catalyst and its enhanced fluidization quality.
Keywords: Dry reforming; Aerogel; Xerogel; Ni/Al2O3Fluidised bed
Distinct new catalysts for utilization of ethylene gas to polymer and oligomer by Abdulhamid A. Alsaygh (101-105).
Bi-nickel-center catalysts were prepared by Schiff-base condensation of 2,3-butanedione with 2,6-di-isopropylaniline; 2-5-butylaniline, 2-isopropylaniline and 1,4-phenylene diamine(I). More Schiff-base ligands were prepared by condensation of 2,3-butandione with 2,6-diisopropylaniline; 2,4-6-trimethyl aniline and 4,4-diaminophenyl (benzidine)(II), and subsequent metathesis reaction with (DME)NiBr2. Bis(alpha diimine)nickel(II)dibromide complexes are suitable catalysts and are precursors for the polymerization of ethylene after activation with methylaluminoxane (MAO). In comparison with these complex analogs, mono-nickel-center catalysts, the new catalysts have much bigger molecules, illustrated by the distance between every two active centers (II and III). For bi-nickel-center catalysts, the catalyst’s structural credibility had profound influence on the catalytic activity. When the substituent was diisopropyl; t-butyl or methyl, the catalysts demonstrated much higher catalytic activity than the corresponding mono-nickel-center catalysts. Catalyst (II) with phenyl bridge showed high activity compared with catalyst (III) with diphenyl bridge. The catalytic properties of these complexes and the character of the obtained polymers depend on the ligand structure of the used catalysts. Substituents on the arene moiety and/or the backbone of the ligand influence the polymerization reaction. Small aryl substituents result in the formation of low molecular weight oligomers, whereas bulky aryl substituents gave high molecular weight polyethylene. Catalysts are cheap and can be prepared easily with available starting material and stable in air. The effect of Al/Ni ratio, of reaction time, variation of ethylene pressure, and the effect of temperature on catalyst performance will be discussed.
Keywords: Organometallic; Polymerizations; Late transition metals; Ethylene
Sustainable world through sustainable materials and integrated biorefineries by Said Salah Eldin Elnashaie; Firoozeh Danafar; Fakhru’l-Razi Ahmadun (107-116).
The present world, with all its advancement, is not a sustainable world, simply because it is based on non-renewable raw materials (non-RRMs). Sustainable world is best expressed in terms of sustainable development and non-RRMs must be replaced by sustainable materials. The sustainable materials needed by modern society are very wide and the main pillars are biofuels and bioproducts. Both pillars are best related through integrated biorefineries (IBRs) formed of related concepts which are very important for the economic development and sustainability of all countries on our planet. Integrated biorefineries include the production of biofuels and bioproducts and utilizing novel technologies. An IBR contains at least two routes: a biochemical route based on a sugar platform and a thermochemical-catalytic route based on a syngas platform. It is a multiple inputs–multi outputs (MIMO) system with design flexibility to accept a wide range of biofeedstock, especially wastes. If the biorefinery consists of only one route/platform, or is limited with regard to MIMO or biofuels/bioproducts produced, then it should be considered an elementary biorefinery (EBR). Sustainable development engineering which is a subsystem of sustainable development (and sustainable world) is more general than Environmental Engineering; and Clean and Green Technology, because it also includes the utilization of RRMs to achieve not only sustainability but also clean environment. An integrated system approach based on system theory is used to analyse sustainable development, sustainable world, sustainable materials, IBRs, EBRs and their interactions.
Keywords: Sustainable; Integrated biorefineries (IBR); Biofuels; Renewable raw material (RRM)
Characterization and activity study of the Rh-substituted pyrochlores for CO2 (dry) reforming of CH4 by Devendra Pakhare; Hongyi Wu; Savinay Narendra; Victor Abdelsayed; Daniel Haynes; Dushyant Shekhawat; David Berry; James Spivey (117-129).
Isomorphic substitution of Rh at varying levels on the B site of lanthanum zirconate pyrochlore (La2Zr2O7; designated LZ) resulted in the formation of thermally stable catalysts suitable for fuel reforming reactions operating at 900 °C. Three specific catalysts are reported here: (a) unsubstituted lanthanum zirconate (LZ), (b) LZ with 2 wt% substituted Rh (L2RhZ), and (c) LZ with 5 wt% substituted Rh (L5RhZ). These catalysts were characterized by XRD, XPS, and H2-TPR. XRD of the fresh, calcined catalysts showed the formation of the pyrochlore phase (La2Zr2O7) in all three materials. In L5RhZ, the relatively high level of Rh substitution led to the formation of LaRhO3 perovskite phase which was not observed in the L2RhZ and LZ pyrochlores. TPR results show that the L5RhZ consumed 1.57 mg H2/gcat, which is much greater than the 0.508 H2/gcat and 0.155 mg H2/gcat for L2RhZ and LZ, respectively, suggesting that the reducibility of the pyrochlore structure increases with increasing Rh-substitution. DRM was studied on these three catalysts at three different temperatures of 550, 575, and 600 °C. The results showed that CH4 and CO2 conversion was significantly greater for L5RhZ compared to L2RhZ and no activity was observed for LZ, suggesting that the surface Rh sites are required for the DRM reaction. Temperature programmed surface reaction showed that L5RhZ had light-off temperature 80 °C lower than L2RhZ. The spent catalysts after runs at each temperature were characterized by temperature programmed oxidation (TPO) followed by temperature programmed reduction and XRD. The TPO results showed that the amount of carbon formed over L5RhZ is almost half of that formed on L2RhZ.
Keywords: Dry reforming; Lanthanum zirconate; Pyrochlores; Lattice oxygen; Isomorphic substitution; Perovskite; Reverse water gas shift