(488a) Two-Step Sub/Supercritical Water and Ethanol Processes for Non- Catalytic Biodiesel Production

Two-step
Sub/supercritical Water and Ethanol Processes for Non- catalytic Biodiesel Production

Aso A. Hassan, Hayder
Al-Hameedi, Dr. Joseph Smith

Chemical
and Biochemical, Engineering/ Missouri University of Science & Technology,
USA

ABSTRACT

The
catalyst-free two-step process has been developed for biodiesel production
using low-grade feedstocks. The first step consists of triglycerides hydrolysis
under subcritical water conditions to generates and increase a free fatty acid
(FFA) contains for ethyl ester production. In its subcritical state, water can
be used as both a solvent and reactant for the hydrolysis of triglycerides. The
hydrolyzed products mixture is separated by decantation into the oil phase of
FFA (upper layer) and a water phase that contains glycerol (lower layer). In
the second step, the hydrolyzed products of free fatty acids were successfully
esterified to their ethyl ester in supercritical ethanol conditions without any
catalyst. Under the sub- and supercritical conditions of water and ethanol the hydrolysis
and the esterification reactions proceed quickly, with the conversion of
greater than 98% after 10-20 min. This two-step process for biodiesel
production offers several advantages such as milder reaction conditions and
pollution reduction due to water using instead of organic solvents. Also, the
glycerol is removed after the hydrolysis reaction so that the backward reaction
between the glycerol and the ethyl ester eliminated and lead to the biodiesel
yield and quality improvement. Finally, the water-glycerol layer (lower layer)
could use directly in supercritical water gasification or dehydration processes
for hydrogen or acrolein production, respectively. The aim of this study is
making a comparison between our previous one-step process and the two-step
reactions process (see Figures 1 and 2) to find the best pathway for designing
and building an integrated reactor. Indeed, the two-step process is more
applicable for the low-grade feedstocks with a high amount of FFA and water.

Figure
1: The Transesterification reaction (One-step)

Figure
2: The hydrolysis and esterification reactions (Two-step)

Keyword:
Biodiesel, supercritical ethanol, subcritical water, hydrolysis.