Hydroformylations economic aspects

Based on their chain length, olefins converted in commercial oxo plants are divided into four groups ethylene (C2), propene (C3), butene to dodecene (C4 to Cl2) and longer-chain olefins (> C12). The factors influencing product distribution and reaction rates in the hydroformylation of olefins will be discussed in Section 2.1.1.3.3. The economical aspects of 0x0 processes are described in Section 2.1.1.4.1. The share of various products in the overall olefin hydroformylation capacity is C2 2%), C3 (73%), C4-C12 (19%) and >Ci2 (6%). 

An aspect of the hydroformylation reaction which is of particular importance in continuous commercial operation is the separation of the catalyst from product aldehyde and/or alcohol, together with its recovery and recycle into the reactant stream. This feature is of considerable economic and process importance for cobalt reactions and of extreme economic importance for rhodium reactions. 

Among the different synthetic procedures available for the preparation of hydratropic acids (e.g., indirect methylation of arylacetic acids,4 asymmetric hydroformylation of styrenes,5 rearrangements of a-bromoalkyl aryl ketals,6 etc.), direct methylation of arylacetic acid derivatives seems the most attractive from both economical and synthetic aspects the reagents are easily accessible and a one-pot reaction is involved. Nevertheless, this procedure is seldom used since the yields of the monomethyl derivatives are severely limited by the low selectivity of the reaction. Sizeable amounts of dimethylated by-products form.2 Even under phase-transfer catalysis conditions, high selectivity in monomethylation is elusive.7-8... 

The results discussed above show that hydroformylation in organic-organic solvent systems is basically possible. However, much more detailed studies are needed to determine whether it is economically feasible. Aspects such as catalyst deactivation during recycling, reaction time, (undesired) formation of alcohols, and continuous operation should be considered. 

A very important general aspect of hydroformylation catalysis is the fact that the regioselectivity of the reaction is usually of great importance for the economic value of the generated products. Typically, the linear product enjoys a much higher market value than the branched one. This point can be exemplified for both the hydroformylation of propene and that of 1-dodecene. While the lower vapor pressure of the resulting plasticizer alcohol defines the higher... 

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