Byproduct Boosts Biodiesel Production

Oct. 22, 2015
Catalyst converts biofuel process waste into raw material for recycle back into the process

Using simple catalysis, researchers in the U.K. have been able to recycle a waste material produced when biodiesel is formed from vegetable oil and convert it into an ingredient that can help produce even more biodiesel.


The researchers, based at the Cardiff Catalysis Institute (CCI) at the University of Cardiff, Wales, hope the development will be an important step in helping the European Union (EU) achieve its 2020 target of 10% of all transport fuels coming from renewable sources such as biofuels.

Current industrial biodiesel production results in large quantities of crude glycerol, which contain impurities that make purification and re-use costly. So, the researchers took the byproduct and turned it back into methanol, one of the raw materials needed in the process.

To achieve this, the researchers reacted glycerol with water — to provide hydrogen — and a magnesium oxide catalyst. The simple one-step process takes place under mild conditions.

Using the recycled methanol, they estimate up to a 10% increase in biodiesel production, a figure they claim would be very helpful to industry at this point in time.

In detail, the process begins with using a syringe pump to inject the glycerol/water mixture into a pre-heater through a long needle extended into the center of the pre-heater. This ensures complete vaporization of the feed. This vaporized feed then enters into the main reactor after passing through a middle connector.

The catalyst is loaded into a stainless steel reactor tube and held in place between plugs of quartz wool. A thermocouple in the catalyst bed monitors the temperature. An external electric furnace heats the bed.

Products are collected in a series of cold traps. The first contains an ice/water mixture; escaping volatile products are condensed in a subsequent trap cooled by liquid nitrogen.

The temperature profile of the reactor is: pre-heater and middle connector, 563K, while the catalyst bed varies between 448K and 673K. Initially, catalysts were tested using a glycerol/H2O feed with 0.25–5g of catalyst. For analysis, the liquid products of the first and second traps are combined. After the third trap, gaseous products are collected in a gas bag for further analysis.

The work is in its early stages; future studies will look to optimize the design of the catalyst and significantly increase its activity and selectivity.

“We’ve provided unprecedented chemistry that highlights the potential to manufacture biodiesel in a much more environmentally friendly and potentially cheaper way by converting an undesired byproduct into a valuable chemical that can be reused in the process,” says Graham Hutchings, director of the CCI and lead author of the study. Its results appear in an article in the journal Nature Chemistry.

Co-author and CCI deputy director Stuart Taylor adds: “We set out to establish ways in which the waste product glycerol could be used to form other useful compounds, but we were surprised when we found that feeding glycerol and water over such a simple catalyst gave such valuable products and interesting chemistry.”

The CCI also coordinates NOVACAM, a project supported by joint funding from the EU’s research program and the Japan Science and Technology Agency. The focus here is on developing new catalysts that will help transform plant waste into key chemicals and liquid fuels.

Some partners in the collaboration are working on breaking down tough lignocellulose into smaller fragments known as platform molecules. Others are focusing on the synthesis and testing of new catalysts based on non-precious metals for processing platform molecules into useful compounds.

An important part of the work is to use materials characterization and computer modeling to understand how the new catalysts function so that materials design can help optimize catalyst performance.

The CCI is tasked with creating these new catalysts, which will take agricultural waste products such as corn husks and stems and transform them into useful chemicals and fuels.

Currently, deconstructing lignocellulose involves costly, rare metal catalysts. By developing more environmentally friendly catalysts, the researchers hope to overcome a major challenge preventing plant waste from being used in a sustainable way for the production of important chemicals and fuels.

Seán Ottewell is Chemical Processing's Editor at Large. You can email him at [email protected].

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