BASF has patented a butadiene-based route for the production of commodity oxo alcohols, namely n-butanol and 2-ethylhexanol. Preliminary analysis shows this technology could be cost competitive with rhodium based propylene oxo alcohol technology in certain scenarios.

The butadiene/C⁴-based process proceeds via the following steps as outlined below. The first step in the process is the addition of n-butanol to butadiene (in pure or contained form). This produces a number of products. However, the major products are 3-butoxybutene-1 (3BOB1) and 1-butoxybutene-2 (1BOB2). By-products include C⁸ and C¹²+ hydrocarbons and oxygenates.

The desired product from the addition reaction is 1BOB2. However, this is produced in lower selectivity than 3BOB1. Hence there is a process step to isomerize 3BOB1 into 1BOB2.

Finally 1BOB2 needs to be converted to 1-butoxy-butene-1, an enol ether. Hydration of the enol ether releases n-butanol and n-butyraldehyde. If the hydration is carried out in the presence of hydrogen then n-butanol is the only product. The isomerization/hydration/hydrogenation reactions can be carried out using one catalyst.

At the time of publication the technology is still embryonic and requires considerable work, especially concerning the addition reaction. Selectivity needs to be improved as well as conversion rates as this dominates the size of any recycle streams. This is very important when a crude C⁴ stream is used as feedstock. However, results to date show some promise.

Speculative economics for a butadiene based route to n-butanol and 2-ethylhexenol are presented and compared to the conventional propylene based route. In the case of the C⁴ route, pure butadiene and crude C⁴ streams are examined as feedstocks. Several cases are presented:

• Mid-point performance based on thermodynamic models developed from patent date (interpolation).
  
• Enhanced performance based on thermodynamic models developed from patent data (extrapolation).
  
• Target performance for second generation C⁴/oxo process.

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