A Promising Approach to Advanced Biofuels w/o Hydrotreatment

Finland's Neste Oil has proven its hydrotreatment approach to advanced biodiesel beyond question. But hydro-treating bio-oils is expensive, and more economical approaches are likely to find quicker and more widespread acceptance among advanced synthetic liquid fuels producers. Fortunately, a joint team from both China's Zhejiang University and the US University of Michigan, is hot on the trail of a process which achieves the advanced renewable synthesis of liquid hydrocarbons without requiring expensive hydrotreatment.

We report herein on the conversion of saturated and unsaturated fatty acids to alkanes over Pt/C in high-temperature water. The reactions were done with no added H2. The saturated fatty acids (stearic, palmitic, and lauric acid) gave the corresponding decarboxylation products (n-alkanes) with greater than 90 % selectivity, and the formation rates were independent of the fatty acid carbon number. The unsaturated fatty acids (oleic and linoleic acid) exhibited low selectivities to the decarboxylation product. Rather, the main pathway was hydrogenation to from stearic acid, the corresponding saturated fatty acid. This compound then underwent decarboxylation to form heptadecane. On the basis of these results, it appears that this reaction system promotes in situ H2 formation. This hydrothermal decarboxylation route represents a new path for using renewable resources to make molecules with value as liquid transportation fuels. _Wiley abstract_via_GCC

Here is more detail on the research from GreenCarCongress.com:

As described in the paper, the team of Jie Fu, Xiuyang Lu, and Phillip Savage converted five different fatty acids prevalent in nature—stearic, palmitic, lauric, oleic, and linoleic—to alkanes over a commercial 5% Pt/C catalyst in high-temperature water (330 °C). The reactions were done with no added hydrogen, in contrast to the processes that have adapted petroleum hydrotreatment technology to convert triglycerides and fatty acids into hydrocarbons.

Recent review articles have highlighted the significant research and development (R&D) efforts that have been devoted to using and adapting petroleum hydrotreatment technology to convert triglycerides and fatty acids into hydrocarbons...The high H2 consumption associated with these processes is their main drawback. H2 is not currently available in large quantities from renewable resources and H2 costs can be high. Moreover, H2 is made primarily from steam reforming of natural gas and CO2 is the byproduct. Thus, a near-term process for the production of fully renewable biofuels needs to operate without added H2.

—Fu et al.

_More at GCC

The GCC article goes on to describe the decarboxylation process adopted by the joint-university team, which produces CO2 as a byproduct of decarboxylation. The process is faster and perhaps more efficient using saturated fatty acides as feedstock, as opposed to unsaturated fatty acids. Oils such as palm oil, which are high in saturated palmitic acid, would seem to be ideal for the process.

If the world can ever pacify the carbon hysterics -- at least remove them from positions of high office and power -- the terrestrial and oceanic plants of the world can be freer to enjoy some extra free CO2, courtesy of the human animal.