Silica-alumina base

Amorphous Silica—Alumina Based Processes. Amorphous siHca—alumina catalysts had been used for many years for xylene isomerization. Examples ate the Chevron (130), Mamzen (131), and ICI (132—135). The primary advantage of these processes was their simpHcity. No hydrogen was requited and the only side reaction of significance was disproportionation. However, in the absence of H2, catalyst deactivation via coking... 

Although detectable concentrations for several elements could be found after fusion, it is felt that the volatility of mercury and possibly lead and tin would make their determination by lithium tetraborate fusion questionable. Table I shows the elements selected for analysis and the accuracy and precision data for the standards used to check the fusion method. Each standard in Table I was of known composition and siliceous in nature. The standards were separately prepared 10 times so that a statistical evaluation of the results could be made. The standards used were USGS Standards G-2, W-l, BCR-1, commercially prepared silica-alumina based standards, and unfused synthetic standards prepared by the Coal Research Bureau (9, 10, 11, 12). The synthetic standards were used because no commercially prepared standard having... 

Chemical composition silica-based and silica-alumina-based materials, chrome, magnesia, chrome-magnesia, spinel, SiC, materials containing carbon (more than 1% carbon or graphite), and special materials (containing other oxides or materials such as zircon, zirconia, Si3N4, etc.)... 

Miller and Zakarian26 have studied the kinetics of the HDA (hydrofinishing) of hydrocracked and dewaxed 500Ns over noble, base metal, and nickel-tin catalysts, all on a silica-alumina base, at 15.3 MPa total pressure and at temperatures between 220°C and 260°C. The feedstocks employed contained trace quantities of sulfur (up to 19 ppm) and nitrogen (3 to 4 ppm). Since a correlation... 

Etiiylene alone, or witii 1-butene Linear polyediylene,ho mo- or copolymer Cyclohexane, pentane, or octane Chrome oxide on silica alumina base 400-500 275-375 Precipitation with water then steam stripping... 

Even when it does not contain any RE ions, the Y zeolite is always responsible for a drop in octane number compared to the old amorphous silica-alumina-based catalysts. In order to gain a few points in the octane number, many refiners add to the principal catalyst a small percentage of a ZSM-5-based additive that has pores 0.55 nm in diameter that can only be penetrated by linear aliphatic structures and, to a lesser degree, by monobranched aliphatic structures (Tables 1 and 2). These hydrocarbons, which are those with the lowest octane number, are mainly cracked to olefin-rich LPG, obviously at the expense of a few percentage points in gasoline yield. 

Although mordenite is much more active than the former amorphous silica-alumina-based catalysts, it is not fully selective for this application and should progressively be replaced by other high-performance acid zeolites such as that with a 10-membered ring aperture, which was recently developed (Table 2). 

Indeed the FCC process as early as the late fifties started to use catalyst formulations based on the incorporation of thermally-stabilized zeolites in a suitable matrix. The advantages were increased rates, increased liquid products, increased tolerance to poisons and larger operating flexibility as compared to former silica-alumina based catalysts. 

Union Carbide discovered X Y zeolites but it remained to Plank and Rosinski (1964, Mobil Oil) to apply these zeolites to clay or silica alumina-based FCC catalysts and thereby achieve a considerable boost to activity and selectivity. It is pleasing to note that Plank and Rosinski were introduced to the US patent office inventors Hall of Fame for this discovery (Figures 22-24) Table VI documents of history of FCC catalyst manufacture. 

The catalyst system (silica-alumina-based catalyst) is non-corrosive and truly heterogeneous ... 

Catalysts suitable for selective hydrogenation of acetylenic compounds in cracked gas streams contain elements of group VI and VIII of the periodic table. An early catalyst was molybdenum sulfide supported on activated alumina (Key and Eastwood, 1946). This was followed by the development of cobalt molybdate and nickel based catalysts (Giaro, 1956 Barry, 1950). Modem catalysts for impure (sulfur-bearing) cracked gas streams typically contain nickel, cobalt, and chromium on a silica-alumina base (United Catalysts, 1993). 

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