Pillared clay catalysts yields

In conclusion, pillared clays catalysts are not as good as initially predicted for the cracking of heavy gas oils, mainly because of the iron contamination of natural clays. There is a probability that they could be applied for the conversion of hydrotreated gas oils, giving a slightly lower gasoline yield, but higher octane number than REY zeolites. 

Finally, PILC, REY-PILC, and a commercial equilibrium catalyst were evaluated at near constant conversion using a heavier feed, hydrotreated resid. The product yields are shown in Table III. Steam deactivated (D), REY-PILC, produced the same gasoline selectivity, LCO/HCO ratio, and coke yield as calcined PILC. The equilibrium catalyst which represents a more severely deactivated (E) sample had higher gasoline selectivity, lower coke yield, and lower HCO/LCO ratio. The higher coke yield of REY-PILC could be due to occlusion of high molecular weight hydrocarbons in the microstructure of the pillared clay. 

Nanosized sulfated tin oxide (STO) particles dispersed in the micropores of Al-pillared clay (STO/Al-P), were used by Mishra and co-workers [91] as an environmentally benign, recyclable and efficient catalyst for the solvent-free synthesis of 3,4-dihydropyrimidin-2(l//)-ones 42 using a domestic microwave oven. The protocol offers advantages in terms of simple experimentation, reusable catalyst, excellent yields, short reaction times, and preclusion of toxic solvents (Scheme 31). 

Another approach to designing shape-selective heterogeneous oxidation catalysts was to use redox metal oxides as the pillaring agents in the preparation of pillared clays. These redox pillared clays have been used for a number of selective oxidations. Chromium pillared montmorillonite (Cr-PILC) is an effective catalyst for the selective oxidation of alcohols with tert-butyl hydroperoxide. 7 Primary aliphatic and aromatic alcohols are oxidized to the aldehydes in very good yields. Secondary alcohols are selectively oxidized in the presence of a primary hydroxy group of a diol to give keto alcohols in excellent yields (Eqn. 21.12). 2... 

A pillared clay containing a quaternary ammonium bromide surfactant has been used as an inexpensive phase-transfer catalyst for the reaction of alkyl halides with sodium azide to form alkyl azides in 82-93% yields.260 It could be reused at least twice, with little or no loss in yield. 

Recently, vanadium-containing oxynitrides were also used as effective new class of catalysts for the ammoxidation of 3P [71, 72]. Furthermore, SAPO and modified SAPOs, such as Sb-V-SAPO-5, Mo-V-SAPO-5 and Mn-V-SA-PO-5, were used for the ammoxidation of 3 and 4Ps picolines and claimed 85% and 90% yields of their corresponding nitriles, respectively [e.g., 73]. Best results on this reaction were reported in various patents [e.g., 42, 74, 75]. The yield of 3CP achieved was over 90% at almost total conversion of picoline. More details on the ammoxidation processes in general and 3P to 3CP in particular can be found in a recent review of Cavani et al. [76]. Roy et al. [77] reported the application of Ti-pillared clay based vanadia catalysts for producing hetero aromatic nitriles from picolines at 350-450°C. 

A tartrate-modified solid Ti catalyst has also been prepared starting from a montmorillonite clay (31). This clay can be pillared with Ti polycations prepared by acid hydrolysis of Ti(OiPr)4. In the presence of tartrate ester, an allylic alcohol such as tram-2-buten-l-ol is epoxidized in 91% yield with 95% ee. These results are superior even to those for the homogeneous catalyst. Moreover, the reaction also proceeds in the absence of the molecular... 

Other examples are pillared bentonite and other clays, which exist as thin sheets only weakly connected, if at all. These layered materials yield low levels of LCB when the catalyst activated at temperatures below its fusion temperature. However, if it is heated to 600-700 °C, so that the structure rearranges, very high LCB levels are produced in the polymer. 

Triphasic systems involving clays pillared with surfactants as catalysts offer versatile routes to a range of useful benzylic compounds.40 By using the organo-clay assemblies with sodium cyanide, thiocyanate and hydroxide, it is possible to prepare benzonitriles, benzyl thiocyanates and benzyl alcohols from the corresponding benzyl chlorides. Most of these reactions occur in yields of ca. 80%. 

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