Abstract
Plant based sources of hydrocarbons are being considered as alternatives to petrochemicals because of the need to conserve petroleum resources for reasons of national security and climate change. Changes in fuel formulations to include ethanol from corn sugar and methyl esters from soybean oil are examples of this policy in the United States and elsewhere. Replacements for commodity chemicals are also being considered, as this value stream represents much of the profit for the oil industry and one that would be affected by shortages in oil or other fossil fuels. While the discovery of large amounts of natural gas associated with oil shale deposits has abated this concern, research into bio-based feedstock materials continues. In particular, this chapter reviews a literature on the conversion of bio-based extracts to hydrocarbons for fuels and for building block commodity chemicals, with a focus on soybean derived products.
Conversion of methyl esters from soybean triglycerides for replacement of diesel fuel is an active area of research; however, the focus of this chapter will not reside with esterification or transesterification, except has a means to provide materials for the production of hydrocarbons for fuels or chemical feedstocks. Methyl ester content in vehicle fuel is limited by a number of factors, including the performance in cold weather, the effect of oxygen content on engine components particularly in the case of older engines, shelf-life, and higher NOx emissions from engines that are not tuned to handle the handle the enhanced pre-ignition conditions of methyl ester combustion [1]. These factors have led to interest in synthesizing a hydrocarbon fuel from methyl esters, one that will maintain the cetane number but will achieve better performance in an automobile: enhanced mixing, injection, and combustion, and reduce downstream issues such as emissions and upstream issues such as fuel preparation and transportation.
Various catalytic pathways from oxygenated precursor to hydrocarbon will be considered in the review: pyrolysis [2], deoxygenation and hydrogenation [3, 4], and hydrotreatment [5]. The focus of many of these studies has been production of fuels that are miscible or fungible with petroleum products, e.g., the work published by the group of Daniel Resasco at U. Oklahoma [6]. Much of the published literature focuses on simpler chemical representatives of the methyl esters form soybean oil; but these results are directly applicable to the production of chemical feedstocks, such as ethylbenzene that can be used for a variety of products: polymers, solvent, and reagent [3].
Although many chemical pathways have been demonstrated in the laboratory, the scale-up to handle quantities of bio-derived material presents a number of challenges in comparison with petroleum refining. These range from additional transportation costs because of distributed feedstock production to catalyst cost and regeneration. Other chapters in the book appear to address the cultivation and harvesting of soybeans and production of oil, so these areas will not be dealt with directly in this chapter except as they may relate to chemical changes in the feedstock material. However, the feasibility of the production of hydrocarbons from soybean triglycerides or methyl esters derived from these triglycerides will be considered, along with remaining technical hurdles before soybeans can make a significant contribution to the hydrocarbon economy.
