MRI used to peek at temperatures inside catalytic reactors

MRI technology could help improve the design and environmental impact of catalytic reactors, including lab-on-a-chip devices

Schematic of metal-organic framework catalyst that promotes the conversion of propylene into propane

UCLA chemists in California, US have employed magnetic resonance imaging (MRI) – a technique normally reserved for scanning the human body – to measure the temperature of gases inside a catalytic reactor. The research could help improve the design and environmental impact of catalytic reactors, including lab-on-a-chip devices, used in the manufacture of pharmaceuticals and other products.

The new method for mapping the temperatures at the gas-solid interface, in which gases are altered through contact with a solid catalyst, was first reported in the journal Nature (502, pp537–540).

Measuring temperature distributions within a reactor is crucial to understanding the energetics of a chemical reaction as reacting gases flow over a catalyst, and to optimising reactor design. But until recently, it was not possible to probe gas temperatures in the reaction mixture without perturbing the flow inside an operating reactor.

 

While there are methods to probe temperatures in liquids, few approaches exist for mapping the properties of gases inside a catalytic reactor without perturbing the flow being studied

‘The new method is important because an overwhelming majority of chemical industry products are made using heterogeneous catalysts functioning at the gas-solid interface,’ said the study’s senior author, Louis Bouchard, Assistant Professor of Chemistry and Biochemistry at UCLA. ‘While there are methods to probe temperatures in liquids, few approaches exist for mapping the properties of gases inside a catalytic reactor without perturbing the flow being studied,’ he said. ‘The inherent non-invasive nature of MRI bypasses this issue and allows us to generate thermal maps of gases during a reaction.’

The researchers also demonstrated microscale MRI images in a micro-reactor. ‘The ability to follow the reaction in a micro-reactor will help engineers and chemists design better lab-on-a-chip devices,’ Bouchard said. Such devices are increasingly used in pharmaceutical synthesis and other catalytic reactions.

Catalytic micro-reactors may provide green chemistry alternatives – less chemical waste, lower cost and minimal energy waste – to conventional, industrial-sized reactors because they make it easier to control the chemical reaction conditions and operate the reactor closer to optimal conditions. However, a longstanding problem has been the lack of tools to map out the chemical reaction conditions inside micro-reactors.