Hello,
I need to use guanidium chloride to denature a protein. However, I’m reluctant because it is absolutely crucial for my experiment that no isocyanic acid is formed. I need to know the equilibrium constants of the reactions where guanidium chloride in solution forms urea which then forms isocyanic acid to see if the isocyanic acid formed is negligible or not. If not negligible, I also need to know the thermodynamics of the reaction (if it occurs very slowly, then it should be okay).
I tried looking it up but I couldn’t find it. Is there a website or an equation that can be used to find eq constants?
Thanks for your time.
Amoon
Pyrolysis of urea and guanidinium salts to be used as ammonia precursors for selective catalytic reduction of NOx
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https://doi.org/10.1016/j.jaap.2015.04.007Get rights and content
Abstract
In this work, the thermal decomposition (pyrolysis) of urea, ammonium carbamate, and guanidinium acetate, carbonate and chloride was performed, using thermogravimetric and differential thermal analysis coupled to gas chromatography and mass spectrometry (TGA/DTA–GC/MS, from 25 to 500 °C). Solid products from pyrolysis were characterized with infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Triazines and heptazines were found as solid products of pyrolysis for the tested solids. Crystallite sizes were assessed using the Scherrer equation; it was found that guanidinium acetate and guanidinium chloride had the biggest crystallites of all solids analyzed (maximums of 113 and 109 nm for guanidinium acetate and guanidinium chloride, respectively) up to 350 °C. These compounds also showed the highest decomposition temperatures, with thermal decomposition starting at 246 °C for guanidinium acetate and 300 °C for guanidinium chloride. This results show the composition of the solid and gaseous products for guanidinium acetate, carbonate and chloride, along with identification of ammonia production of guanidinium salts, which offer an important comparative with the thermal decomposition of well-known ammonia precursor compounds like urea and ammonium carbamate.
Introduction
Controls in nitrogen oxides (NOx), which are environmental pollutants, have become tighter in the last years; this has increased the need for better pollutant controls in lean emissions, typically present in diesel powered motors. There are many processes [1] for achieving low NOx concentrations in exhaust gas, one of these being the selective catalytic reduction (SCR). In this process, nitrogen oxides react with a reductant which can be ammonia or hydrocarbons. The precise reaction mechanism followed by the system depends on the relationship between NO and NO2, with at least three reactions possible, being:
When NO accounts for at least 90% in the exhaust, reaction 1, named “Standard SCR”, is present [2], [3]. For Reaction (2) to occur, a slight majority in the NO2 concentration must exist, higher than 50% in the exhaust. Reaction (3) occurs when NO and NO2 concentrations are equal. The latter reaction is also called “Fast-SCR” reaction [4].
Hydrocarbon-SCR presents several disadvantages when implementing it in a commercial scale, the most important being an increase in fuel usage. Ammonia-SCR avoids this problem, by using an NH3 precursor compound, typically an aqueous solution of 32.5% urea in water, known commercially as AdBlue®, which has the advantages of low toxicity and easy transportation, compared to gaseous pure ammonia [5]. However, there are important disadvantages of the solution, such as a moderately high 261 K freezing point, the possibility of having solid formation in the exhaust line, and difficulties in dosing at exhaust temperatures below 473 K. These drawbacks have motivated several researchers to study alternative ammonia-promoting compounds [6].
Some of the recently investigated alternatives have been liquid solutions of different compounds, such as ammonium formate [7], methanamide [8], formamyde [9] and guanidinium formate [10]. However, solid alternatives like ammonium carbamate [11] and amminated inorganic salts [12] have been studied due to their potential increase in performance compared with liquid alternatives. Solid urea and ammonium carbamate are well known and the thermal decomposition has been studied in the past with many detailed mechanisms available [13], [14], [15], [16], [1
he ammonia solid precursors used were urea (CH4N2O, 99.0–100.5%, Sigma–Aldrich, St. Louis, USA), ammonium carbamate (CH6N2O2, > 99.5%, Sigma–Aldrich, St. Louis, USA), guanidinium acetate (C3H9N3O2, 99%, Sigma–Aldrich, St. Louis, USA), guanidinium carbonate (C3H12N6O3, 99%, Sigma–Aldrich, St. Louis, USA) and guanidinium chloride (CH6N3Cl, > 99%, Sigma–Aldrich, St. Louis, USA). There was no pre-treatment protocol used, thus materials were used “as-received”.
he ammonia solid precursors used were urea (CH4N2O, 99.0–100.5%, Sigma–Aldrich, St. Louis, USA), ammonium carbamate (CH6N2O2, > 99.5%, Sigma–Aldrich, St. Louis, USA), guanidinium acetate (C3H9N3O2, 99%, Sigma–Aldrich, St. Louis, USA), guanidinium carbonate (C3H12N6O3, 99%, Sigma–Aldrich, St. Louis, USA) and guanidinium chloride (CH6N3Cl, > 99%, Sigma–Aldrich, St. Louis, USA). There was no pre-treatment protocol used, thus materials were used “as-received”.
Thermogravimetric and differential thermal
Thermogravimetric and differential thermal