Alkylation catalysts liquid acid properties

This contribution is an in-depth review of chemical and technological aspects of the alkylation of isobutane with lightalkenes, focused on the mechanisms operative with both liquid and solid acid catalysts. The differences in importance of the individual mechanistic steps are discussed in terms of the physical-chemical properties of specific catalysts. The impact of important process parameters on alkylation performance is deduced from the mechanism. The established industrial processes based on the application of liquid acids and recent process developments involving solid acid catalysts are described briefly. 2004 Elsevier Inc. 

The technology and chemistry of isoalkane-alkene alkylation have been thoroughly reviewed for both liquid and solid acid catalysts (15) and for solid acid catalysts alone (16). The intention of this review is to provide an up-to-date overview of the alkylation reaction with both liquid and solid acids as catalysts. The focus is on the similarities and differences between the liquid acid catalysts on one hand and solid acid catalysts, especially zeolites, on the other. Thus, the reaction mechanism, the physical properties of the individual catalysts, and their consequences for successful operation are reviewed. The final section is an overview of existing processes and new process developments utilizing solid acids. 

The use of immobilised ILs as catalysts would result in the easy separation of the catalyst from the reaction mixture, allowing its fast reuse and avoiding the generation of contaminated waste and its subsequent treatment. Ionic liquids have already been proposed as catalysts for Friedel-Crafts alkylation of benzene with olefins in order to produce LABs32-35. They show Lewis acidic properties when a Lewis acid (e.g. 

The catalytic cracking of four major classes of hydrocarbons is surveyed in terms of gas composition to provide a basic pattern of mode of decomposition. This pattern is correlated with the acid-catalyzed low temperature reverse reactions of olefin polymerization and aromatic alkylation. The Whitmore carbonium ion mechanism is introduced and supported by thermochemical data, and is then applied to provide a common basis for the primary and secondary reactions encountered in catalytic cracking and for acid-catalyzed polymerization and alkylation reactions. Experimental work on the acidity of the cracking catalyst and the nature of carbonium ions is cited. The formation of liquid products in catalytic cracking is reviewed briefly and the properties of the gasoline are correlated with the over-all reaction mechanics. 

Highly Lewis-acidic chloroaluminate ionic liquids (ILs) are well known to be both versatile solvents and effective catalysts for Friedel-Crafts reactions [1,2]. Tailoring the physical and chemical properties of the ILs to the needs of a specific reaction allows for a high diversity of applications [3,4]. We could show that immobilising these ILs on inorganic supports yields very active catalysts for alkylation reactions. The immobilisation of ionic liquids leads to novel Lewis-acidic catalysts (NLACs). The methods presented include the method of incipient wetness (method 1, further on called NLAC I), which has been introduced in detail by Hoelderich et al. f5], but focus of this presentation lies on the methods 2 (NLAC II) and 3 (NLAC III). 

There have been many efforts to commercialize 2,6-dicarboxynaphthalene for the preparation of poly(ethylene-2,6-naphthalate) due to its favorable thermoplastic properties compared with PET. Therefore, there are numerous patents in which 2,6-alkyl-substituted (alkyl = methyl, ethyl, isopropyl) naphthalenes are oxidized to the corresponding aromatic di-acids, applying mostly Co/Mn/Br catalysts with various co-catalysts such as Zr or Pd in acetic acid as the solvent. The major byproduct is formed by the oxidation of the naphthalene ring to give trimellitic acid (TMA) [5a, 8]. Sumikin Chemical has developed a method to prepare 2,6-naphtha-lenedicarboxylic acid by oxidation of 2,6-diisopropylnaphthalene (2,6-DIPN) in the liquid phase with air in a 500 tpy plant. Sumikin uses a newly developed catalyst based on Co/Mn with an addition of a few ppm of Pd giving advantages such as yields higher than 90 %, suppression of TMA production to around 1 %, and thus better catalyst recovery, and reduced consumption of acetic acid. 

It is not surprising that electrophilic aromatic substitutions were the first organic reactions investigated using acidic room-temperature chloro-almninate(III) ionic liquids. Indeed, chloroaluminate(ni) species combine their properties of good solvents for simple arenes to their role as Lewis acid catalysts. In Friedel-Craft alkylations, polyalkylation is common as well as the isomerisation of primary halides to secondary carbonium ions. 

With respect to ILs as cosolvents, the interest was centred on two types of ILs aUcylammonium and 1,3-dialkylimidazolium-based ionic liquids. For the first type, we selected ethylammonium nitrate, considering that it is a protic ionic liquid (PIL) and that it can act as a potential acid catalyst. With respect to the second type of ILs, we selected those based on l-methyl-3-n-butylimidazolium cation, characterised by a slighter HBD acidity than that of the alkylammonium type (Figs. 13.2, 13.3). These ILs exhibit a wide spectrum of physicochemical properties. It was demonstrated that their water content, density, viscosity, surface tension, melting point and thermal stability are affected by the length of the alkyl chain and the nature of the anion. Several anions were incorporated in this class of ILs. 

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