Isoolefins

Saturation of olefins other than reactive olefins usually is not desired. The added hydrogen is often expensive or useful elsewhere, and it does not provide any real improvement in product quality. Acmally, product quality may be reduced in the case of gasolines. Research octane number losses may be correlated with increasing olefin saturation. So in many cases, hydrodesulfurization conditions are selected with an eye toward minimizing olefin saturation over and above that needed for product quality improvement. There is one exception saturation of certain olefins shows substantial improvements in Motor octane number. This is true for iso- and n-pentenes and to a lesser extent for higher boiling isoolefins. The higher n-olefins show octane losses upon saturation. 

Monomethyl paraffins (C10-C15) from monomethyl paraffins, di-isoparaffins, di-isoolefins, aromatics Silicalite-1 Cyclohexane/n- hexane [146,157]... 

Also, a normal paraffin is converted to an isoparaffin first by dehydrogenation to a straight-chain olefin, then by rearrangement to form an isoolefin, and by hydrogenation to an isoparaffin. 

Waddell et al. (3) prepared elastomeric compositions effective as air barriers from novel C4 to C7 isoolefin oligomers and were free of long-chain branching. 

Olefins are formed by dehydrogenation of the n-paraffin feed over the metallic hydrogenation-dehydrogenation function and are adsorbed on the acidic surface of the catalyst as carbonium ions by proton addition. After skeletal isomerization they are desorbed as isoolefins and subsequently hydrogenated to the corresponding isoparaffins. The net result (i.e., the formation of carbonium ions) of the action of metal and acid in dual function catalysis is, on pure Friedel-Crafts type catalysts, described by the scheme ... 

K) C.M.Cawley et al,JlnstPetroleum(London) 34,5X1 -108(1948) CA 42,3961-2(1948) (Discussion on various incendiary mixts for bombs, mortar shells, etc) L)H.H.Cooke et al.USP 2445311(1548) CA 42,7985(1948)(Incorporation of isoolefin polymers of high mol wt with flammable naphtha produces a high-viscous mass almost semisolid in consistency which is suitable for incendiary bombs) Ll)D.P. O Brien,USP 2451864(1948) CA 43,1190(1949)... 

As shown in Figure 10, one reaction is the isomerization of the normal carbenium ion. We can neglect the reverse reaction since the iso/normal olefin ratio produced over the cracking catalyst is usually well below the thermodynamic equilibrium value, due in part to depletion of the isoolefins by hydrogen transfer. 

The MAT test with 1-pentene spiked feed did not show an increase in carbon numbers other than C5, leading to the conclusion that isomerization predominates over oligomerization at high temperatures, so that isoolefins come mainly from isomerization, and from cracking of larger olefins which are not products of oligomerization. 

A series of runs were made in which sulfuric acid was added in small increments to a 4 1 mixture of isobutane and 2.2,4-trimethyl pentene-1 at -30 C or -20 C. Increased amounts of the feed isoolefin reacted as more acid was added. Almost no reaction products were noted in the hydrocarbon phase at A/0 ratios of 0.25 or less. When the A/0 ratio was increased to 0.5, C9 - C Q hydrocarbons were formed during a 1.5 hour period during which tYme most of the original isoolefin reacted. 

H. H. Cooke E. J. Holzclaw, USP 2445311 and 2445312 (1948) CA 42, 7985-6 (1948). Incendiary mixtures consisting of flammable naphtha thickened to form a highly viscous mass by means of isoolefin polymers (such as... 

Isoolefin Polymers of molecular wt 50000 to 100000, such as Isobutylene polymer, were patented as thickeners for flammable naphtha... 

The synthesis of isobutene copolymers containing conjugated double bonds was accomplished only a few years ago by copolymerizing the isoolefin with suitable trienes. The results, largely unpublished, permit to compare the behaviour of these two classes of copolymers which display several analogies. The presence of the conjugated double bond functionalities gives rise to several possibilities of post-modification reactions which extend widely the utilization of these classes of synthetic elastomers. 

Bifunctional (metallic and acidic functions) catalysts are applied to a variety of oil-refining and petrochemical processes. For example, paraffin hydroisomerization involves n-paraffins dehydrogenation to a-olefins over metal, skeletal isomerization of n-olefins to isoolefins over acidic sites, followed by hydrogenation of isoolefins to isoparaffins over metal. Zeohte-supposted noble metal catalysts are often used for these types of reactions, which... 

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