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NMR Spectroscopy of Bulk Oxide Catalysts
Published in Alexis T. Bell, Alexander Pines, NMR Techniques in Catalysis, 2020
The η-, γ-, δ-, and θ-forms are known as the transitional aluminas. They have highly disordered structures, high surface areas, and a large number of surface hydroxyl species at exposed surfaces. Transitional aluminas are catalytically active materials and are known to facilitate Η-D exchange, C-H activation, skeletal olefin isomerizations, and alcohol dehydrations [57]. In industrial catalytic processes, aluminas are mostly used as catalyst support materials.
Synthetic Crude Processing
Published in Sonil Nanda, Prakash Kumar Sarangi, Dai-Viet N. Vo, Fuel Processing and Energy Utilization, 2019
Rachita Rana, Sonil Nanda, Ajay K. Dalai, Janusz A. Kozinski, John Adjaye
The typical desirable properties of these catalysts are high surface area, larger number of active sites, thermal and chemical stability, selectivity, suitable shape, and pore-size (Botchwey et al. 2004). These ideal catalysts are active components of molybdenum (Mo) or tungsten (W), generally in combination with a suitable metal promoter (e.g., nickel, cobalt, and iron) and an alumina or silica support. Catalyst support is used to give mechanical strength to the catalyst and allow it to withstand extreme reaction conditions (Satterfield 1996). However, in the case of feeds with high metal content, a catalyst with high pore volume to avoid mouth plugging is required (Ancheyta et al. 2005). Apart from the feed constituents, coke formation at high reaction conditions also can contribute to poor catalytic activity that might eventually lead to catalyst deactivation (Ancheyta and Speight 2007).
Catalytic Reforming Catalysts
Published in Soni O. Oyekan, Catalytic Naphtha Reforming Process, 2018
A catalytic reforming catalyst support material could be a composite of a porous inorganic oxide, molecular sieve, and appropriate binder. Inorganic oxides suitable for use as catalyst support material can include alumina, magnesia, titania, zirconia, chromia, zinc oxide, thoria, ceramic, porcelain, bauxite, silica, silica-alumina, silicon carbide, clays, and crystalline zeolitic aluminosilicate materials.(18) A variety of crystalline alumina forms such as alpha, eta, gamma, and theta alumina are used. Several excellent studies have been conducted on the phase transition of bayerite, gibbsite, and boehmite, and their results are as shown in Figures 5.1 and 5.2.(6,7) Boehmite and gibbsite are different forms of aluminum hydroxides that occur naturally in bauxite deposits.(26) Boehmite is the monohydrate form of alumina (AlOOH) and gibbsite is the trihydrate form (Al (OH)3) and the fact that the boehmite is aluminum monohydrate is highly significant, as the gamma alumina produced from boehmite has a high concentration of residual hydroxide groups.
Physicochemical Characterization and Chemical Reactivity of Biochar from Pyrolysis of Dried Distiller’s Grains with Solubles (DDGs)
Published in Combustion Science and Technology, 2023
Danlan Cui, Xin Zheng, Jianfeng Zou, Shirui Yu, Xiao Kong, Junmeng Cai, Xingguang Zhang
The content of alkali metals (Na, K) and alkaline earth metals (Mg, Ca), which are important nutrients for improving soil fertility, was also determined by ICP (Wu et al. 2022) (Table 2). The content of inorganic elements in DDGs-biochar increased significantly, indicating that heat treatment still has a certain influence on the inorganic content of biomass. DDGs and DDGs-biochar contain a large number of minerals, which can be utilized. According to related literature, the mineral elements in DDGs are processed using synthetic fertilizers, conducive to the growth of plants. For example, the potassium in DDGs-biochar can be absorbed by plants, while most of the potassium in DDGs is water-soluble and easy to flow in wet soil, so it is easily bioavailable (Dirbeba et al. 2018). If used as a catalyst support, it may also have a catalytic effect on the reaction rate.
Synthesis of OMC supported Pt catalysts and the effect of the metal loading technique on their PEM fuel cell performances
Published in Chemical Engineering Communications, 2020
Silver Güneş, F. Çiğdem Güldür
Generally, the catalyst support is expected to act as a good mass transfer medium while providing the catalyst with a good dispersion and a high surface area. Carbon black (Vulcan XC 72) is the conventional support material for Pt, because of its availability and low cost (Auer et al., 1998). However, carbon black has a disordered structure and contains too many micropores that are not interconnected (Antolini, 2009). A number of alternatives have been proposed as better supports, including carbon nanotubes (CNTs) (Paoletti et al., 2008), aerogels, xerogels (Arbizzani et al., 2011), cryogels (Babič et al., 2006), nanocoils (Cellorio et al., 2014) and fullerenes, with limited success. Among the most promising ones are the CNTs, however, the lack of binding sites makes the metal loading very diffucult and leads to either a low metal loading or non-uniform metal distribution (Zhang et al., 2005). Small mesopore diameters and two-dimensional structures are additional obstacles for metal loading. Another family of mesoporous structures, the ordered mesoporous carbon (OMC) have recently attracted considerable attention for its potential uses in fuel cell applications (Chang et al., 2007; Liu et al., 2009; Hsueh et al., 2013; Viva et al., 2014; Stojmenovic et al., 2015). OMCs typically exhibit high surface areas, high electrical conductivities and well-organized pore framework which is advantageous for mass transfer.
Recent development of integrating CO2 hydrogenation into methanol with ocean thermal energy conversion (OTEC) as potential source of green energy
Published in Green Chemistry Letters and Reviews, 2023
Mohd Hizami Mohd Yusoff, Lau Kok Keong, Nor Hafizah Yasin, Mohammad Syamzari Rafeen, Amiruddin Hassan, Geetha Srinivasan, Suzana Yusup, Azmi Mohd Shariff, A. Bakar Jaafar
Choi et al. (30) investigated the methanation of CO2 using Pd-Cu/CeO2 catalyst. Highest methanol yield was obtained by the impregnation of the catalysts, including 10 wt.% of Cu, 1 Pd, and CeO2 at 210°C. In catalysis, the catalyst support provided to the catalyst causes a significant increase in the activity of the catalyst. Therefore, Lin et al. (31) investigated the use of catalyst support of Pd-Cu for the heterogeneous catalysts, including TiO2, ZrO2, Al2O3, and SiO2. Among the TiO2 supports, commercial TiO2 P25 supported with Pd-Cu exhibited the highest CO2 hydrogenation activity and showed CH3OH selectivity of 25.7%, and CO2 conversion of 16.4%. Meanwhile, Dong et al. (32) investigated the CO2 hydrogenation to methanol using Cu/Zn/Al/Zr catalyst calcined at 573 K. The maximum CO2 conversion of 24.5% and 57.6% of methanol selectivity were obtained at a pressure of 5 MPa, H2/CO2 molar ratio of 3:1, reaction temperature of 270°C and GHSV of 4600 h−1. Peng Gao et al. (33) investigated the production of methanol using carbon dioxide by modifying the Zn/Al/Cu catalysts with the help of Mn, Ze, and Y. Results indicated that BET surface area in each case was significantly increased. However, the catalyst modified with Y exhibited the highest production efficiency of methanol. The operating conditions were kept at H2/CO2 ratio of 3:1, temperature of 230–270°C, and pressure of 5.0 MPa. This was observed due to significant increase in the surface area of Cu, which in turn increased the number of basic actives sites to the total number of active sites.