3. Fraction CO2 in product
Product MM CO2/ MM Product
Al(CO2)2 0.765217391
CH3CO2H (acetic acid) 0.733333333
NaHCO2 0.647058824
H2NCONH2 0.628571429
BHCO3 0.611111111
Fe(CO2)2 0.611111111
NaHCO3 (via NaH) 0.523809524
MgCO3 (via MgCl2) 0.521945433
MgCO3 (via MgO) 0.521945433
ethyl carbonate 0.5
CaCO3 (via CaCl2) 0.44
CaCO3 (via CaO) 0.44
Calcium looping is a well-established CO2 capture method producing calcium
carbonate. In figure B, the data is presented for species that preform better than
calcium carbonate. In figures C and D, the pounds produced and fraction CO2 are
evaluated independently and decreasing trends are shown.
In figure E, the average value of the two parameters is calculated for the species
presented in figure D. Balanced equations for each of these species are presented
below listed in descending order.
Al+ 2CO2 ร Al(CO2)2
Fe+ 2CO2 ร Fe(CO2)2
MgCl2+ H2O +CO2 ร MgCO3 +2HCl
CaCl2+ H2O + CO2 ร CaCO3 + 2HCl
NaH + H2O + CO2 ร NaHCO3 + H2
Complete price data was available for six species (NaHCO3 via NaH, NaCO3 via NaH,
NaHCO3 via NaOH, CH2CO2H via CH3OH, CaCO3 via CaCl2, and H2NCONH2). Two
gave a positive result for cost of products minus cost of feed:
Formula Cost Products โ Cost Feed
2NH3 +CO2 ร H2NCONH2 + H2O 27.2125
NaOH + CO2 ร NaHCO3 3.367
NaHCO3 via NaH and CaCO3 via CaCl2 were included in the previous list (figures D
and G) but will no longer be considered after giving a negative result. While the
4. oxalate products looked promising due to their high pounds produced and fraction
CO2 values, their electrochemical conversion is a more promising application
beyond the scope of this study. Additionally, diphenyl carbonate via PhNH2 will be
considered due to its high pounds produced value, secondary ammonia product, and
its application in polymer chemistry. An updated list of formulas with standard
Gibbโs free energy is provided below.
Formula โGยฐr (kJ)
MgCl2 (c) + H2O (l) +CO2 (g) ร MgCO3 (s) +2HCl (g) +20.25
2NH3 +CO2 ร H2NCONH2 + H2O -100.4
NaOH (aq) + CO2 (g) ร NaHCO3 (s) -37.5
2C6H5NH2(g) +2H2O+ CO2 (g) ร (C6H5O)2CO + 2NH3(l) + H2(g) +1244.9
Conclusions and Recommendations:
From this study the most promising carbon dioxide capture species were urea and
sodium bicarbonate. Both reactions are well documented and employed in industry.
Ammonia ranks second in largest tonnage produced. On a grand scale, this scenario
poses the same problem as looping: a finite need for urea. However, through
integration of an existing urea producing operation to use waste carbon dioxide
there exists a potential net gain.
Sodium hydroxide is a co-product of the chlor-alkali process. Interestingly, the
Solvay process producing sodium bicarbonate uses calcium carbonate as the carbon
dioxide source, paralleling calcium looping. The initial input of calcium carbonate,
and the subsequent replenishment of spent material, could be produced with waste
carbon dioxide.
Learning Outcomes for Student:
When I chose to work on this project, I was warned that there was a high probability
nothing would come of my work. In terms of hard results this was true. The two
results come from industry. More importantly both results were isolated based on
evaluation of cost rather than the two parameters I chose to use.
This semester was an entirely different variety of research than my work in a lab,
despite many overlapping topics. The most challenging aspect of this semester was
finding relevant data. Consequently, the most tangible skill I will draw from this
experience learning how to manipulate each resource to ultimately find what I need.
There was a lot of improvising along the way trying to fit what I had to what I
needed. For example when I was not able to find all of the price information, I had to
make assumptions that would give me the same information in the end. I gathered
information from online sources, libraries, professors, and mentors. If I had come to
a blockade, there was someone who had a bridge.
