Aromatization of isophorone

It is absolutely necessary to control the hydrogenation process in order to avoid production of phenol or a mixture of hydro-xybenzenes with or without an alkyl group. It has been reported that 2,3,5-trimethyl phenol is also obtained during aromatization of isophorone [1,7] ... 

Isolation of meto-cresol from the products of high temperature pyrolysis/aromatization of isophorone has been commercially successful, and both meto-cresol and 3,5-xylenol are being produced by a number of companies, pioneered by Shell Chemicals, UK. 

Dimethylphenol is not directly accessible by selective alkylation of phenol with methanol it is produced by the aromatization of isophorone at 540 to 650 °C on Cr203/K20/Al203 catalysts, or chrome-nickel steel. 

Figure 5.25 Flow diagram for the aromatization of isophorone to 3,5-dimethylphenol...

Unlike o-xylene and p-xylene, the application of m-xylene is limited to the production of isophthalic acid, nitrated xylenes and m-xylylenediamine. Production of 3,5-dimethylphenol, which was carried out in earlier times by alkali fusion, has now been replaced by gas-phase aromatization of isophorone (see Chapter 53.4.3.2). 

S)-Proline based chiral modifier esters and amides containing aromatic rings were used in the enantioselective hydrogenation of isophorone and EtPy (Sipos et al. ). 

The various reaction rate properties of the different solvents influence the design of a catalytic reactor. Eor example, for a specific catalyst bed design, an effluent stream containing a preponderance of monohydric alcohols, aromatic hydrocarbons, or propjiene requires a lower catalyst operating temperature than that required for solvents such as isophorone and short-chain acetates. 

For environmental reasons there has been interest in methods for manufacturing isocyanates without the use of phosgene. One approach has been to produee diurethanes from diamines and then to thermal eleave the diurethanes into diisocyanates and alcohols. Although this method has been used for the production of aliphatic diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, for economic reasons it has not been adopted for the major aromatic isocyanates MDI and TDI. 

In certain niche applications, aliphatic isocyanates, such as isophorone diisocyanate (IPDI), hexamethylene diisoeyanate (HDI), methylene 4,4 -biscyclo-hexylisocyanate (H12MDI), and polymeric versions of these diisocyanates, are used, e.g., in instances where light stability or reduced reactivity is needed. These isocyanates usually cost more than the aromatic diisocyanates. Thus, they are used in adhesive areas that can Justify the higher costs. 

A key factor in the preparation of polyurethanes is the reactivity of the isocyanates. Aromatic diisocyanates are more reactive than aliphatic diisocyanates, and primary isocyanates react faster than secondary or tertiary isocyanates. The most important and commercially most readily accessible diisocyanates are aliphatic and colorless hexamethylene-1,6-diisocyanate (HDI), isophorone diisocyanate (IPDI),and aromatic, brownish colored diphenylmethane-4,4 -diiso-cyanate (MDI), 1,5-naphthalenediisocyanate, and a 4 1 mixture of 2,4- and 2,6-toluenediisocyanates (TDI). 

With its high surface area and the accessibility to the amino groups, chitosan aerogel appeared as a good candidate to play the double role of support for metal complexes and organic base. Silica supported metallophthalocyanine are efficient catalysts for the oxidation of aromatic compounds [139]. The immobilization of hydrosoluble metallophthalocyanines (MPcS with M = Fe or Co) on chitosan aerogels afforded new heterogeneous catalysts for the aerobic oxidation of p-isophorone [140]. 

Acetone aldol condensation proceeds on either acidic or basic catalysts. On basic catalysts, the reaction products are mainly a,P-unsaturated ketones [5] whereas on acidic materials formation of aromatics and olefins is favored [6]. In our catalytic tests, the main reaction products were mesityl oxides (MO s) and isophorone (IP). MO is formed from the initial selfcondensation of acetone whereas IP is a secondary product arising from the consecutive aldol condensation between MO and acetone. Over all the samples the reaction rate diminished as a function of time-on-stream as shown in Fig. 1 for the MgjAlOx sample which lost about 60 % of its initial activity after 10 h-run. Initial reaction rates (r ) and product selectivities (S j) were calculated by extrapolating the reaction rates vs. time curves to zero. 

Three diisocyanates (D) were studied toluene dllsocyanate (TDI), isophorone dllsocyanate (IPDI), and dlcylcohexylmethane-4,4 -diisocyanate (HMDI). Weatherablllty is one consideration in the choice of a dllsocyanate. Oligomers based on aliphatic diisocyanates form coatings that weather well, whereas coatings based on aromatic dllsocyanates yellow on exposure. ... 

Trimethylcyclohe.xanone [873-94-9] (TMC-one, 3,3,5-trimethylcyclohexanone) is a saturated cyclic ketone. It is a colorless high boiler with an aromatic odor reminiscent of menthol. Trimethylcyclohexanone is only moderately miscible with water, but is miscible in all proportions with all organic solvents. It is chemically closely related to isophorone. Trimethylcyclohexanone dissolves cellulose nitrate, low molecular mass PVC grades, poly(vinyl acetate), vinyl chloride-vinylacetate copolymers, chlorinated rubber, alkyd resins, unsaturated polyester resins, epoxy resins, acrylic resins, etc. 

Aliphatic isocyanates are used whenever resistance to ultraviolet light is a critical concern. Examples of aliphatic isocyanates are hexamethylene diisocyanate, hydrogenated MDI, isophorone diisocyanate, and tetramethylxylene diisocyanate. Structures for these molecules are shown in Fig. 23. The aliphatic isocyanates are usually more expensive than aromatic isocyanates and find limited use in adhesive applications. Resistance to ultraviolet light is usually not a critical concern in adhesives because the substrate shields the adhesive from sunlight. 

For the synthesis of DPUR, a cycloaliphatic diisocyanate, isophorone diisocyanate (IPDI) from Fiiils, was used since unlike aromatic isocyanates, it does not result in yellowing of the coatings and films. The polyols used were polytetramethylene glycol (PTMG) with a MW of 2000... 

---