Sunday, March 14, 2010

Better Catalysts, Better BioDiesel from Jatropha

Conventional bio-diesels suffer from poor cold weather performance. Better means of converting unsaturated vegetable oil triglycerides to straight chain alkanes (without glycerine and without double bonds). Jatropha oil is seen as having potential for high oil yield, with minimal environmental disruption.
Researchers at Japan’s National Institute of Advanced Industrial Science and Technology (AIST) have devised rhenium-modified catalysts that significantly increase the yield of diesel-type alkanes (C15-C18) from the hydrotreatment of jatropha oil under conditions of higher jatropha-to-catalyst weight ratios. A paper on their work was published online 10 March in the ACS journal Energy & Fuels.....

... Pt-Re-based catalysts are known to be effective for naptha reforming and other processes. At 20 wt % Re, the conversion into hydrocarbons was found to be constant at ~80% at any jat/cat ratio employed, with high selectivity for C18. They also found that Pd-modified Re/H-ZSM-5 catalysts are excellent candidates for triglyceride conversion as well.

Rhenium-modified Pt/H-ZSM-5 catalysts were found to be much more effective for hydrotreating jatropha oil even at a high jat/cat ratio of 10, and 80% conversion and 70% C18 selectivity were achieved. The reaction pathway involves hydrogenation of the C=C bonds of the these triglycerides followed by mainly C15-C18 alkane production through hydrodeoxygenation with decarbonylation and decarboxylation. _GCC

Renewable green diesel-type alkanes can be produced by hydrotreating jatropha oil and vegetable oils at standard hydrotreating conditions (i.e., 543−573 K) with Pt/H-ZSM-5 catalysts, which are active under the weight ratio of jatropha or vegetable oil/catalyst of 1. The carbon molar yield of straight chain C15−C18 alkanes was 80% for hydrotreating pure jatropha oil. However, under the jatropha oil/catalyst weight ratio of 10, being important from a practical point of view, the alkanes yield falls to only 2.3%. Under a high jatropha oil/catalyst ratio of 10, rhenium-modified Pt/H-ZSM-5 catalyst is found to be effective for raising the C15−C18 alkanes yield. The yield of C15−C18 alkanes is 67% at an optimun Re/Al molar ratio of 0.8. Investigation of catalyst natures indicates that metallic Pt and Re are independently present on the surface, but synergism of these two metals could play an important role in the hydrotreating reaction, even at a high ratio of jatropha oil/catalyst of 10. The reaction pathway involves hydrogenation of the C═C bonds of the jatropha oils followed by mainly hydrodeoxygenation with decarbonylation and decarboxylation to form C15−C18 straight chain alkane mixtures. _ACS

South and Southeast Asia can become new global energy superpowers, if palm, jatropha, pongamia, moringa, and other tropical seed oil crops live up to their potential -- and if these vegetable oils can be converted into pure hydrocarbon fuels economically.

These Asian operations will be largely administered by either Chinese or Indian companies. Other tropical regions -- such as parts of South America and Africa -- also present significant potential for production of high yield tropical oilseed crops. Chinese biofuel ventures in Africa are likely to grow more numerous, as the operations in Southeast Asia begin to become more profitable.

Advances in the refinement of bio-oil fuels, such as described in the Japanese research above, should expedite the global impact of these tropical oilseed derived fuels.

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