Aldox process

The same front-end Oxo process is used to make the butyraldehyde feed for 2-EH manufacture, but then the butyraldehyde is dimerized in a reaction called aldol condensation. Some plants even combine the Oxo process and the Aldol process and then refer to it as the Aldox process. 

Aldox process. A two-step process combining the Oxo process and the Aldol Process. For example, propylene is reacted with carbon monoxide and hydrogen to form butyraldehyde (Oxo process), which is then dimerized and hydrogenated to give 2-ethylhexyl alcohol. 

Ethylhexanol is usually produced by subsequent aldolization of butyraldehyde produced in the oxo reaction followed by hydrogenation of the intermediate unsaturated aldehyde.89 In Esso s Aldox process, however, in situ aldol condensation is effected by suitable promoters.11 Magnesium ethoxide and soluble zinc compounds are recommended to promote controlled aldolization during the oxo reaction. The Shell variant uses potassium hydroxide. Serious disadvantages (mixed aldolization with the branched aldehyde, problems associated with recycling of the additives), however, prevented wider use of the Aldox process. 

Alcohols from an aldol reaction may be linear if acetaldehyde is a reactant, but usually aldol alcohols are branched primary alcohols. An aldol condensation sometimes is done with an OXO reaction. The combined process is called the ALDOX process. 

This so-called Aldox process, commercially performed by Shell as well as by Exxon [4, 35], is realized in a one-pot reaction by adding Ni and KOH as co-catalysts to the medium of the Co -catalyzed oxo reaction (cf. Section 2.1.1). 

Aldol condensations occur, particularly under basic conditions. This property has been used to form higher aldehydes and alcohols directly in a single step under hydroformyiation conditions , the so-called Aldox process. 

Another example for the use of a multifunctional solid catalyst is the Aldox process for the production of 2-ethyIhexanol (Eq. 6-10). 

Aldox process, the aldolization occurs within the propylene hydroformylation reactor. 

---