Applying mass flow for novel process of CO2 hydrogenation
As hydrogen continues to increase in popularity as a fuel, demand for methanol and ethanol are also expected to increase. These chemicals are often made using a process called CO2 hydrogenation which reduces CO2 to CO and H2O via a thermodynamically intensive process called the reverse water gas shift reaction (RWGSR).
CO2 hydrogenation using renewable hydrogen, such as sourced from green, gold, orange, or white hydrogen, is a clean process that allows for CO2 to be made into a series of different end-products, including methanol, formic acid, and ethanol while simultaneously reducing CO2 emissions. By using CO2 hydrogenation and green hydrogen to make hydrogen carriers such as methanol, the hydrogen industry can more easily store hydrogen gas by converting it to chemicals that are easier to transport.
Although this process normally requires high temperatures and pressures, researchers at the Tata Institute of Fundamental Research (TIFR) located in Mumbai have developed a method for CO2 hydrogenation at room temperature by plasmonic excitation of H2 and CO2 via plasmonic catalysts.
In their process, the researchers at TIFR convert CO2 to CO at selectivity greater than 95% by applying the phenomenon of localized surface plasmonic resonance (LSPR) that explains how electrons at the surface of metals oscillate as their frequency matches that of incident electromagnetic radiation. In other words, these researchers use special gold-nickel (Au-Ni) nanoparticle catalysts to reduce CO2 to CO in the presence of solar light and H2 within a light reactor. As a result, much less energy is required to overcome the activation barrier, thus reducing the overall energy required to make different end products via CO2 hydrogenation.
Designing the new process
In the experimental design, CO2 and H2 are mixed into a continuous-flow reactor such that the Au-Ni catalyst bed is kept at about 1 mm in order to allow for sufficient light penetration. The intensity of the light and temperature are adjusted in order to optimize the efficiency under different operating conditions. However, the flow of CO2 and H2 are kept constant at 10 mL/min and 1 mL/min in order to create stable gas conditions in the reactor.
Using mass flow for stable research flow conditions in CO2 hydrogenation
Because the experimental CO2 hydrogenation processes requires stable flow conditions for CO2 and H2 in order to test other operating conditions, highly repeatable, precise, and accurate low flow full-scale control is required. Alicat MC-Series and CODA KC-Series mass flow controllers provide near-instantaneous, reliable, repeatable low flow control at full-scales down to just 0.5 SCCM or 40 g/hr.
Communication for automated control using either a PLC or computer via analog, serial, or industrial protocols allow for highly personalized flow data measurement and control. Features such as batching and totalizing allow for the tracking of flow data.
- Full-scale ranges of 0.5 SCCM to 5,000 SLPM
- Control range of 0.01% – 100% of full-scale
- Accuracy up to ±0.5% of reading or ±0.1% of full-scale, whichever is greater
- Repeatability up to ±0.1% of reading and 0.02% of full-scale
- Response times less than 30 ms
- Full scale ranges from 40 g/h to 100 kg/h
- Control range from 2% – 100% of full-scale
- Gas accuracy up to ±0.5% of reading or ±0.05% of full-scale, whichever is greater
- Repeatability up to ±0.05% of reading and ±0.025% of full-scale
- Pressure rated up to 4000 PSIA at higher full-scales
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