Biodiesel by Catalytic Distillation – Towards Sustainable Fuels
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Poster Session (EPIC - Poster) - P2
Keywords: biodiesel, reactive distillation, solid acids
Authors: Anton A. Kiss, Alexandre C. Dimian, Gadi Rothenberg
Affilitation: University of Amsterdam, The Netherlands
In the context of acute depletion of fossil fuel sources, sustainable energy management is a major concern that makes the urgent implementation of renewable fuels a crucial issue. Biodiesel is a sustainable alternative to petroleum diesel, with better performance and environmental benefits. It can be produced from vegetable oils, animal fat or even recycled greases from food industry. [1]
Biodiesel consists of fatty acid methyl esters (FAME), currently manufactured by either trans-esterification using liquid Na/KOH catalyst, or batch esterification of free fatty acids using H2SO4 as catalyst. These catalysts are not only corrosive and toxic, but they require neutralization and an expensive separation, thus making biodiesel an attractive but costly alternative fuel. The complete catalyst removal is imperative due to the EU restrictions on sulfur content in diesel fuels (< 15 ppm as of 2006).
To solve these problems, we propose the replacement of the homogeneous acid catalyst with solid acids [2] and develop a sustainable esterification process based on catalytic reactive distillation (RD). Solid acids can be easily separated from the biodiesel product; they need less equipment maintenance and form no polluting by-products. Finding catalysts that are active, selective, water-tolerant and stable under the process conditions is the main challenge for a successful design. We have previously screened a large number of zeolites, heteropoly-compounds, metal oxides, ion-exchange resins, and carbon-based solid acids.[3]
The catalyst development was integrated in the process design at an early stage, by data mining and embedding of reaction kinetics in the process simulation. In this work, we focus on the application of metal oxides catalysts (based on niobia, zirconia, titania and tin oxide) in an integrated reactive-separation design that is able to shift the chemical equilibrium to completion and preserve the catalyst activity by continuously removing the products.
The process proposed here dramatically improves the biodiesel synthesis and reduce the number of downstream steps. The key benefits are: efficient use of the reactor volume leading to high unit productivity; stoichiometric reactants ratio hence no external recycles of excess alcohol; no neutralization step since the solid acids do not mix with the products hence no salt waste streams; reduced capital and operating cost due to the integration of the reaction and separation into one unit and the elimination of additional separation steps; and sulfur-free fuel as solid acids do not leach into the biodiesel product.
In the lecture we will present the key features of our approach, and discuss the implications of this novel process to make low-cost biodiesel a reality in the near future.
References
1. B. Buczek, L. Czepirski, Inform 2004, 15, 186.
2. T. Okuhara, Chemical Reviews, 2002, 102, 3641.
3. A. A. Kiss, A. C. Dimian, G. Rothenberg, Adv. Synth. Cat., 2006, 348, 75.
Presented Thursday 20, 13:30 to 14:40, in session EPIC-1: Poster Session (EPIC - Poster) - P2.
