1. PROCESS OF HYDROTHERMAL CONVERSION OF CARBON DIOXIDE INTO FORMIC ACID WITH ZINC
Daniel Román González, Alexander Navarrete, Antonio Nieto, Ángel Martín, María Dolores Bermejo
1High Pressure Processes Group. Department of Chemical Engineering and Environmental Technology. University of Valladolid (Spain)
- .Introduction and Aims 1
The last year, 2015, was the warmest year since modern record-keeping began in 1880, according to a new analysis by NASA´s Goddard Institute for Space Studies. The average temperature was 13.9ºC. This was 0.9 ºC above the average of the twentieth century. Carbon dioxide is an important greenhouse gas. Atmospheric 𝐶𝑂 2 levels have increased by more than 40 percent since the beginning of the Industrial Revolution, from about 280 parts per million (ppm) in the 1800s to 400 ppm today.
Our study aims to develop a technology that helps fighting climate change. From our point of view, carbon dioxide can be considered as a resource to get chemicals of interest. This technology can be seen as a complement to the carbon capture and storage.
The conversion of carbon dioxide will be under hydrothermal conditions, i.e. , at high temperature and pressure, using zinc as reducing metal. It is necessary to bring the reaction to those conditions, to break the stability of 𝐶𝑂 2 .
Products that can be formed with this way are: formic acid, methanol, ethanol and acetic acid. The majority compound formed is formic acid.
Experiments were performed with two different materials reactors : SS316 stainless steel and Inconel alloy In this work we show the influence of reactor material in the formic acid performance. 3 3 3
Figure 2. Formic acid molecule
Figure 1. Reaction Mechanism
- .Experimental section 2
1º Charge the reactor with a bicarbonate solution and Zn
2º Maintain the reactor within the muffle the stipulated time
3º Cool the reactor for 20 minutes in water
4º Separating the solid sample of the liquid sample
Testing of the liquid sample
HPLC
TOC
Zing conference on carbon dioxide catalysis, Algarve (Portugal), april 2016
Testing of the solid sample
XRD
Temperature: 275 and 300 °C
Time: min
Conditions
_ 𝒁𝒏/ 𝑵𝒂𝑯𝑪𝑶 𝟑 ratio 5/1 was used
_ Concentrations were 42 𝒈 𝑳 of 𝑵𝒂𝑯𝑪𝑶 𝟑 and 𝒈 𝑳 of Zn
_ % Filled Reactor= 50
Batch reactors are tubing with two end fittings.
EXPERIMENTAL DESIGN:
The main reaction is:
- .Results and Discussion 3
Zn+ 𝐶𝑂 2 + 𝐻 2 𝑂 HCOOH + ZnO
Figure 1. and Figure 2. show the different performance of the reaction according to the material of the reactor. Inconel in general presents a better performance than Stainless Steel. This could be explained because nickel from Inconel alloy favors the reaction.
In the experiment at 300ºC it can be seen that longer reaction times not to provide a higher yield of formic acid. That could be explained by the descarboxilation reaction of the formic acid:
Operating at 275ºC a better yield of the formic acid is obtained than at 300ºC. The maximum peak performance is observed after 90 minutes at 275ºC, while the peak at 300ºC occurs after 30 minutes.
HCOOH 𝐶𝑂+ 𝐻 2 𝑂
Fig 4. Solid Sample after 10 minutes of reaction at 275ºC (SEM)
Fig 3. Pot zinc (SEM)
Fig 5. Solid Sample after 10 minutes of reaction at 275ºC (EDX) (48% ZnO)
Fig 6. Solid Sample after 30 minutes of reaction at 275ºC (EDX) (>99% ZnO)
Fig 1. Inconel vs Stainless Steel at 275ºC
Fig 2. Inconel vs Stainless Steel at 300ºC
- .Conclusions 4
Better performance is obtained with Inconel reactors due to the catalytic effect of nickel.
A higher yield toward formic acid is obtained in experiments at 275ºC than at 300ºC, although at longer reaction times.
ACKNOWLEDGEMENTS:
This research has been financed by the Spanish Ministry of Economy and Competitiveness through project ENE R, “AQUA-CO2NV”. M. D. B. Thanks the Spanish Ministry of Economy and Competitiveness for a “Ramón y Cajal” research fellowship.