SEP 23, 2016

A Cleaner, More Efficient Method for Methanol

WRITTEN BY: Jennifer Ellis

Methanol is one of the world’s most widely used chemicals, and has been since the 1800’s. It is used to make formaldehyde and acetic acid for glue, resin and plastic production, and as a key component in the conversion of biodiesel fuel, development of fuel cells, and use for electricity generation.

The problem is that methanol production is tremendously energy heavy. An industrial methanol plant can produce 600 million gallons per year by reforming natural gas with steam, then converting to liquid methanol. The process uses extreme heat and pressure, which consumes large amounts of energy and expense.

Chemists at Stanford University might have just figured out how to convert methane into methanol more efficiently and with less energy consumption. It has been known for years that methane can be converted into methanol easily and at room temperature using zeolites. So what is holding the methanol industry back from using zeolites to convert methane using this less expensive method? No one has been able to figure out how exactly the process works. Until the process is determined in detail, it cannot be scaled up to industry standards.

Zeolites are small porous crystalline structures that contain trapped water. Certain types of zeolites happen to be very reactive with methane. Zeolites can form naturally in volcanic and sedimentary rock, or can be made synthetically for specific purposes such as detergents or catalysts.

In the 1990’s, Russian scientists discovered that specific zeolites that contain iron become very reactive with methane, quickly converting it to methanol at any temperature. Yet, no one could figure out how this reaction was occurring until now.

“Iron zeolites are promising catalysts for low-temperature methane conversion,” said study co-author Edward Solomon, a professor of chemistry at Stanford and of photon science at SLAC National Accelerator Laboratory. “Finding an efficient catalytic process for converting methane into methanol could have far-reaching economic implications.”

The key was discovering the location and make-up of the “active” site on the zeolites where the reaction takes place. The team was able to locate the “active” sites through a series of spectroscopy techniques and create computer models of the structure.

“We were then able to show what makes the active site so reactive,” Snyder said. “We found that the iron core of the active site is locked in an unusual, constrained geometry by the zeolite crystal, and this leads to exceptional reactivity with methane.”

Finding the primary location of the reaction and understanding how the reaction takes place provides the missing link to beginning work on scaling up the reaction. However, even though this is a great first step, there are other obstacles to overcome such as removing the methanol from the zeolites once the reaction occurs. Because the zeolite structures are porous, the converted methanol becomes trapped in the zeolite.

Despite technical obstacles, the knowledge gained from this study offers promise for more energy-efficient and cleaner production of methanol in the future.

Sources: Stanford News, Methanol Institute, Zeolites