Isomerization/disproportionation

Migration of the Methyl Groups. Reactions that involve migration of the methyl groups include isomerization, disproportionation, and... 

A key portion of the SHOP process is the isomerization—disproportionation (I/D) process in which excess light (C —C q) and heavy olefins (Cjg ) are converted to detergent range odd and even linear internal olefins. Eor each pass through this system, only 10—15% of the olefins fed are... 

Isomerization, disproportionation, and decomposition reactions of the radical Ri yield nonsaturated end groups CH2=CH—CH2 and result in the formation of ethane and ethylene. Isomerization and decomposition... 

Industrial applications of zeolites cover a broad range of technological processes from oil upgrading, via petrochemical transformations up to synthesis of fine chemicals [1,2]. These processes clearly benefit from zeolite well-defined microporous structures providing a possibility of reaction control via shape selectivity [3,4] and acidity [5]. Catalytic reactions, namely transformations of aromatic hydrocarbons via alkylation, isomerization, disproportionation and transalkylation [2], are not only of industrial importance but can also be used to assess the structural features of zeolites [6] especially when combined with the investigation of their acidic properties [7]. A high diversity of zeolitic structures provides us with the opportunity to correlate the acidity, activity and selectivity of different structural types of zeolites. 

Dealkylation and isomerization (disproportionation) processes used in the manufacture of benzene and xylenes are discussed in Sections 4.5.2 and 5.5.4. 

Superacids were shown to have the ability to effect the protolytic ionization of a bonds to form carbocations even in the presence of benzene.190 The formed car-bocations then alkylate benzene to form alkylbenzenes. The alkylation reaction of benzene with Ci—C5 alkanes (methane, ethane, propane, butane, isobutane, isopentane) are accompanied by the usual acid-catalyzed side reactions (isomerization, disproportionation). Oxidative removal of hydrogen by SbF5 is the driving force of the reaction ... 

C at pressures of about 250—400 kPa (36—58 psi). The two types of catalysts, the amorphous silica—alumina (52) and the crystalline aluminosilicates called molecular sieves or zeolites (53), exhibit strong carboniumion activity. Although there are natural zeolites, over 100 synthetic zeolites have been synthesized and characterized (54). Many of these synthetic zeolites have replaced alumina with other metal oxides to vary catalyst acidity to effect different type catalytic reactions, for example, isomerization. Zeolite catalysts strongly promote carboniumion cracking along with isomerization, disproportionation, cyclization, and proton transfer reactions. Because butylene yields depend on the catalyst and process conditions, Table 7 shows only approximations. 

Nafion-H whose acid strength is —12 is active lor diversified organic reactions such as alkylation isomerization, disproportionation, transalkylation acyla lion, nitration, hydration, rearrangement etc [1 5] Since Nafion-H can be used m aqueous solution it is a useful catalyst... 

Rosin. Rosin is used mainly in some modified form. Because the abietic-type acids in rosin each contain a carboxyl group and double bonds, they are reactive and can be used to produce salts, soaps, esters, amines, amides, nitriles, and Diels Alder adducts and they can be isomerized, disproportionated, hydrogenated, dimerized, and polymerized. When destructively distilled, rosin produces a viscous liquid, termed rosin oil, used in lubricating greases. 

Zeolites are integral components of petrochemical refineries that produce benzene, xylene isomers, ethylbenzene and cumene. These aromatics must be high in purity for downstream conversion to polyesters and styrenic or phenolic based plastics. Catalytic processes for producing aromatics employ zeolites for isomerization, disproportionation, transalkylation, alkylation, and dealkylation. 

The following reactions occur isomerization, disproportionation, transalkylation, ring saturation, and dealkylation/cracking. The low yields of methane and ethane indicate that methyl groups are removed and combined to form higher paraffins by what is known as... 

Time on Stream = Ih TMB = Trimethylbenzene " p-xylene/o-xylene = Isomerization/Disproportionation... 

Nafion (Figure 4.12), a perfluorinated polymer containing pendant sulfonic acid groups, is generally considered to be a solid superacid whose pK ranges from -5 to -9. It was earlier shown to be an active catalyst for various organic reacfions such as alkylation, isomerization, disproportionation, transalkylation, acylation, nitration, hydration, rearrangement, and so on. ° ° ... 

In a more general way, the changes in the isomerization/ disproportionation ratio on zeolite Y with different Si/Al ratio have been related with changes in the zeolite adsorption capacity occurring during dealumination (182,183). The xylene isomerization on other 12 MR zeolites h been reported (184,185), showing that depending on the size and structure of channels different isomerization/disproportionation ratios are obtained, as well as different distribution in the trimethylbenzenes formed. 

Borosilicate Catalysts, BorosHicates, which are prepared by the substitution of B for the Al in ZSM-5, are described as practical catalysts for shape-selective acid catalysis. The preferred application is the processing of Cg aromatics using isomerization, disproportionation, and transalkylation reaction steps. The borosilicate catalyst may also contain a metal additive, such as nickel or noble metal. 

The most important benzene aromatics in terms of quantity are benzene and p-xylene. Since the production from reformer gasoline, pyrolysis gasoline and coke-oven benzole is frequently inadequate to meet the demand, isomerization, disproportionation and dealkylation methods have been developed to complement the direct production from aromatics mixtures. 

Humphries et al. [92,93] gave an overview of different test reactions used to characterize the acidity of zeolites. The reactions included cracking, isomerization, disproportionation, and alcohol dehydration as well as hydride transfer reactions involving cyclohexene conversion. In the following sections, we will discuss each class of these test reactions for their ability to give information about the nature, concentration, and strength of the active sites involved in acid-catalyzed reactions. 

To cope with the unsatisfactory distribution of olefins, the SHOP includes an isomerization/disproportionation section which converts light and heavy olefins into more valuable internal C12C15 olefins). 

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