Olefination mechanism

A conventional FCC unit can be an olefin machine with proper operating conditions and hardware. Catalysts with a low unit cell size and a high silica/alumina ratio favor olefins. Additionally, the addition of ZSM-5, with its lower acid site density and very high framework silica-alumina ratio, converts gasoline into olefins. A high reactor temperature and elimination of the post-riser residence time will also produce more olefins. Mechanical modification of the FCC riser for millisecond cracking has shown potential for maximizing olefin yield. 

However, there is no reason to believe that a x-allyl or x-olefin mechanism for C—C bond rupture is limited to ring opening. Rather it should be a general process occurring in straight and branch-chain aliphatics as well. For the purpose of illustration, we write reactions (22) and (23) as generalizations of the reverse of (11) and (13), respectively. We shall refer to mechanisms such as (22) and (23) x-olefin/allyl hydrogenolysis... 

Halogen Transfer Reactions from bis-Amino Halonium Ions to Acceptor Olefins Mechanism and Strategies for Chiral Halogenation... 

This reaction affords the cyclopropanation of olefins. Mechanism... 

In conclusion, although our results do not rule out the mechanism of carbene insertion into a metal-alkyl bond (2b), the possibility of making C - C bonds in Fischer-Tropsch via a car-bene-olefin mechanism should be considered as an alternative path. Further studies are in progress to decide between both types of mechanisms. 

Decomposition of TMPs and Other Isoparaffins TMPs and other isoparaffins in alkylates contain tertiary C-H bonds, which permit degradation reactions. First, sulfuric acid acts as an oxidant to start a series of reactions that convert TMP into a mixture of C4-C16 isoparaffins. Second, because of their tertiary C-H bonds, TMPs react (are actually alkylated) with C3-C5 olefins mechanism 2-type reactions are predominant. Both types of reactions lower the quality and the quantity of the alkylate. 

It is possible to apply the methods of conformational analysis to predict the relative yields of the cis- and metal atom to which the 2-butyl radical is attached may be regarded as equivalent to another methyl group, it is found that there are three possible staggered conformations (see Fig. 4). Conformation (I) would lead only to ci -2-butene, (II) only to [Pg.106]

Figure 2 represents the hydride mechanism in which H2 adds before the olefin. Sometimes the olefin adds first (the olefin mechanism) as is found for [Rh(dpe)(CH30H)2]BF4 (10). 

Jeske, G.,. Oligomerization of olefins. Mechanism of hydrocarbon insertion, J. Amer Chem. Soc., 107, 3091, 1985. 

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