Alumina boria catalyst

Sato et al. [195] have studied the surface borate structures and the acidic properties of alumina-boria (3-20 wt.%) catalysts prepared by impregnation method using B(MAS)-NMR measurements and TPD of pyridine, as well as their catalytic properties for 1-butene isomerization. The number of Brpnsted acid sites was found to increase with increasing boria content, and the catalytic activity was explained by the strong Brpnsted acid sites generated by BO4 species on the surface of alumina. 

It follows from all the above considerations that the acidic character of the surface is necessary for the esterification reaction. This view is supported by the parallel found by some workers [405,406] between the rate of esterification and that of other typical acid-catalysed reactions. A linear correlation was established between the rate of acetic acid—ethanol esterification and that of deisopropylation of isopropylbenzene on a series of silica—alumina, alumina—boria and alumina catalysts [406] a similar relation was found between the rate coefficient of the same esterification reaction and the cracking activity of a series of silica—alumina catalysts prepared in a different way [405]. 

The acid function of the catalyst is supplied by the support. Among the supports mentioned in the literature are silica-alumina, silica-zirconia, silica-magnesia, alumina-boria, silica-titania, acid-treated clays, acidic metal phosphates, alumina, and other such solid acids. The acidic properties of these amorphous catalysts can be further activated by the addition of small proportions of acidic halides such as HF, BF3, SiFit, and the like (3.). Zeolites such as the faujasites and mordenites are also important supports for hydrocracking catalysts (2). 

Several different types and sizes of catalyst have been employed in commercial catalytic cracking processes. The commercial catalysts have been composed predominantly of either silica and alumina, or silica and magnesia. Other compositions have been investigated in the laboratory although some, such as silica-zirconia, alumina-boria, and alumina activated with various fluorides, have high activities, none has yet proved sufficiently attractive to warrant displacing the presently used catalysts. 

Similarly, we prep/ired a large batch of purified precipitated hydrous alumina and precipitated other materials on it. We found that alumina-boria was an active catalyst. Moving down the Periodic Table from silicon to titanium, we were not able to prepare an active catalyst from titania-alumina but titania-boria was active. 

The early type of catalytic cracking units involved the use of a fixed-bed operation and this type of processing has been largely supplanted by the fluid- and moving-bed types of operation. The catalysts are used in the form of powder, microspheres, spheres, and other preformed shapes. The catalysts employed are either synthetic silica-alumina composites or natural aluminosilicates. Other catalysts, such as silica-magnesia, alumina-boria, silica-zirconia, and silica-alumina-zirconia have found limited commercial application and, at present, the synthetic silica-alumina and natural clay catalysts dominate the field. 

Boron phosphorous oxide shows a high catalytic activity for 1-decane oligomerization. The optimum composition of the oxide and pretreatment temperature are P/B = 1.1 and 873 K, respectively. For the reaction, acid sites stronger than ffo— —5.6 are effective. Although the surface area of boron phosphorous oxide is less than one-tenth those of silica alumina and alumina boria, the conversion of 1-decane on the former catalyst is much higher than those on the latter catalysts. 

A detailed examination of the effects of operation conditions on boria on alumina catalyst performance and lifetime is reported in this paper, in an attempt to further elucidate the important parameters controlling optimisation and maintenance of caprolactam yield. 

Fig-1, (a) oxime conversion, (+ ) ceprolactam selectivity and ( ) caprolactam yield with time using 0.1 g boria on alumina catalyst at a reaction temperature of 300 C. 

The effect of temperature on the conversion, selectivity and yield after 3 hours on stream is shown in figure 2. In each case a catalyst mass of 0.1g boria on alumina catalyst was tested. With increasing reaction temperature the oxime conversion increased, however, maxima in lactam selectivity and yield were observed at a reaction temperature of 300 C. At higher temperatures excessive coking and side reactions were thought to occur,... 

Fig.4. (a) Oxime conversion, (b) Caproiactam selectivity, (c) Caproiactam Yield using 0.2g (.) boria on alumina, M regenerated boria on alumina and (+) alumina catalyst at 300 C for 30 hours. 

In conclusion, decrease in cyclohexanone oxime yield and caprolactam selectivity with time on stream is a major factor in the use of boria on alumina catalyst in the rearrangement reaction. Coke deposition and basic by-product adsorption have been suggested as a means of deactivation. In addition the conversion of water soluble boron, which is selective to lactam formation, to an amorphous water insoluble boron species is another factor that can account for the catalyst deactivation. 

Alumina is one of the most widely used catalyst supports in the petroleum industry because it is robust, porous, relatively inexpensive, and—what is especially important—it is capable of contributing acid-catalyzed activity that can be tailored to suit the requirements of a diverse array of catalytic processes. These include reforming (52, 55), hydrotreating (84, 55), and paraffin isomerization (56-55). Since pure alumina is relatively inactive for the skeletal isomerization reactions that are necessary in such processes, its acid activity is promoted through the addition of catalyst components such as fluoride, chloride, phosphate, silica, or boria. After a discussion of pure alumina itself, we will review pertinent studies of surface acidity and catalytic activity of the promoted aluminas. 

FIGURE 158 The MW distribution of polymers made with Cr/alumina is significantly altered by the presence of boria on the catalyst, which lowers the H2 sensitivity of some sites. Catalysts were tested at 95 °C with 8 ppm BEt3,1.0 MPa H2, and 3.8 MPa ethylene. 

Figure 159 shows the unusual effect that a surface silica coating has on the MW distribution of the polymer. Like boria, silica creates a second, high-MW peak. Because these polymers were made with H2 in the reactor, it is likely that the silica-affected sites lost their ability to respond to H2, and this loss caused the appearance of the high-MW peak. The addition of a small coating of silica on Cr/alumina had a different effect from the addition of Al3+ ions to Cr/silica. Both treatments increased activity, but whereas the former increased the polymer MW, the latter decreased it. Again, on Cr/Si-alumina catalysts this may reflect, not the rate of (3-hydride elimination, but the influence of hydrogenolysis on the MW distribution. 

Beside adsorption techniques, an 85% control efficiency of dioxins/furans can be achieved by the employment of the DeDiox system. The catalysts used are mostly composed of Ti, V and W oxides. Additionally, Pt and Au oxides supported on silica-boria-alumina were also found to be effective at 200" C. ... 

The common catalysts lose most of their activity at the following temperatures Super Filtrol natural, 1400°F silica-alumina synthetic, 2000 F silica-magnesia, 1400°F and silica-boria, 1400°F. However, in practice, regeneration temperatures are kept below 1000 to 1100 or 1150°F except bauxite which may be regenerated at even 1300°F without appreciable loss in activity. All catalysts lose some activity upon long use. The decline is. particularly noticeable with natural catalyst processing sour stocks and even the excellent catalyst cases of the Houdry process allow some decline in activity over a period of a... 

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