A research collaboration of Japan’s National Institute of Advanced Industrial Science and Technology and Mexico’s Instituto Politecnico Nacional have developed a one-step hydrotreatment process over catalysts containing Ni-Mo and solid acids that converts the tested vegetable oils jatropha, palm and canola to renewable diesel and propane (LPG) fuels.

The research addresses some critical issues with the production of biodiesel.  Converting vegetable oils to diesel type products is more costly and complex than the product price can support and the abundant residue of glycerin poses alternative use, recycling or disposal problems.

The paper on the work has been published in the American Chemical Society Journal Energy & Fuels.

The paper narrative explains the problem saying, “In recent years, the hydrotreatment of vegetable oils to produce hydrocarbons has been studied worldwide and extensive research has been performed to search suitable reactors and catalysts. When vegetable oils are treated at high temperatures and high pressures without a catalyst, vegetable oils can be converted to the mixtures of paraffins, cycloparaffins, and aromatic hydrocarbons but a relatively large amount of fatty acids remains in the products.”

The paper points out two types of catalysts have been reported as effective catalysts in converting vegetable oils to diesel distillated hydrocarbons: noble metal catalysts (such as supported Pd, Pt, and so on) and sulfided bimetal catalysts (such as Ni-Mo, Co-Mo, Ni-W, and so on).

The paper narrative also covers the know-how that solid acids (such as H-ZSM-5, SO4/ZrO2, and so on) can convert vegetable oils to the mixtures of gasoline, kerosene, light gas oil, gas oil, and long residue in the hydrocracking of vegetable oils.

The research then sought to combine sulfided Ni-Mo and various solid acids to achieve hydrogenation, deoxygenation, hydroisomerization, and hydrocracking for the hydrotreatment of vegetable oils.

Here’s how the team set up the lab apparatus: Build a stainless steel tubular reactor with an inside diameter of 1 cm by 50 cm long for loading catalyst and a furnace for heating the tubular reactor. The vegetable oil is pushed into the reactor in a constant rate by a high-pressured microfeeder, while a mixed gas containing 90% H2 and 10% Ar is introduced into the reactor from a high-pressure H2 cylinder and the flow rate is controlled by a mass flow controller.

Pressure in the reaction system is controlled by a back-pressure regulator. A cold trap (submerged in a tank of ice water) was set between the reactor exit and the back-pressure regulator to collect liquid products. The standard reaction conditions were: catalyst amount, 1 g; reaction temperature, 350 °C; H2 pressure, 4 MPa; liquid hourly space velocity (LHSV), 7.6 h; ratio of H2 to oil in feed, 800 mL/mL, in which the H2 volume was described in the conditions of standard temperature and pressure (STP).

The various vegetable oils were converted to mixed paraffins by the one-step hydrotreatment process although they contained quite different amounts of free fatty acids, the team noted. At the same time triglycerides and free fatty acids underwent the hydrogenation and deoxidization during the reaction.

At the same time the glycerin groups in the vegetable oils were converted to propane over the catalyst Ni-Mo/SiO2-Al2O3 by hydrogenation and deoxidization.

The process looks pretty neat and clean.

There are a couple issues, the furnace level of heat needed, some 350ºC and the stream of hydrogen gas with a bit of argon.  These inputs have a cost to cover as well as the raw vegetable oils.

But the result is a liquid hydrocarbon product that can be directly used as fuel for current diesel engines, and the gas hydrocarbon product can be used as a liquefied petroleum gas (LPG) or propane fuel.

The team looks to have a new process to convert vegetable oil to fuel that would work in current engine technology.  The operating costs aren’t worked out, nor are the matters of scaling up discussed.

This is though, the first time a reactor has been built using a catalyst made from both a metal compound and a solid acid that works producing marketable fuels form the inputs of vegetable oil, some hydrogen and argon and heat.

It’s impressive work that answers those biodiesel problems.  Biodiesel has not gained the market share that ethanol has won – ethanol is increasing in market share worldwide, not just in the U.S. and Brazil.  The biodiesel market is just tiny in comparison.

If the collaborator’s technology can scale, that biodiesel market should change too.


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