Catalytic combustion of volatile organic compounds over CuO-CeO 2 supported on SiO 2 -Al 2 O 3 modified glass-fiber honeycomb

Supercritical Carbon Dioxide Extraction-Mediated Amendment of a Manganese Oxide Surface Desired to Selectively Transform Nitrogen Oxides and/or Ammonia

“…The NH 3 -TPD experiment provided a curve of “the amount of NH 3 desorbed from the surface versus temperature” under various rates (β) used to elevate the temperature (10–30 °C min –1 ), as shown in Figure S9. The TPD theorem served to extract the energies required for desorbing a mole of NH 3 from the surfaces ( E NH3 ) under two major assumptions that E NH3 values were constant even with the change in the NH 3 coverage on the surfaces and the surfaces were composed of multiple L sites whose binding strengths with NH 3 were diverse. − The NH 3 -TPD curves were deconvoluted into three sub-bands of I, II, and III with the peak temperatures ( T M ) of ∼255, ∼326, and ∼409 °C, respectively. This again might be caused by a variety of sites with dissimilar binding affinities to NH 3 and allowed us to establish the relationships of ln­(β/ T M 2 ) versus 1/ T M for the catalysts (Figure A) whose slopes are − E NH3 / R ( R : gas constant). − Resulting E NH3 values of the surface sites featured by the sub-bands of I, II, and III for the catalysts were then averaged to compare their Lewis acidic strengths.…”

“…NH 3 oxidation on L sites present in Mn oxides was reported unavoidable at elevated temperatures and could severely reduce S N2 values if L strengths were strong. ,− Therefore, NH 3 -TPD runs on the catalysts post NH 3 adsorption at 350 °C were conducted and analyzed identical to those post NH 3 adsorption at 180 °C (Figures S9 and S14). − Again, the purpose of these experiments was to measure the quantities ( N NH3 ) and strengths ( E NH3 ) of acidic sites accessible to NH 3 at 350 °C (Table S1). N NH3 values of the catalysts were reduced at 350 °C in comparison with those at 180 °C.…”

“…This suggested that Mn might reveal larger conversions of NH 3 ( X NH3 ) than Mn-CO 2 under diffusion-limited domains if E NH3 values of acidic sites inherent to the catalysts were of comparable magnitude. The relationships of ln­(β/ T M 2 ) versus 1/ T M were constructed using two sub-bands of deconvoluted NH 3 -TPD profiles for the catalysts (Figure B). − A higher thermal energy could spur the surfaces to release NH 3 more readily, thus decreasing the E NH3 values of the catalysts at 350 °C compared to those at 180 °C. Nevertheless, Mn-CO 2 provided a smaller E NH3 value (∼21 kJ mol NH3 –1 ) than Mn (∼25 kJ mol NH3 –1 ).…”

“…In addition, NH 3 -TPD (or NO-TPD) experiments were also initiated by purging the material surfaces with 10 vol % O 2 /He at 400 °C for an hour and cooling to 180 °C (or 350 °C) under He; 5 vol % NH 3 /He (or 5 vol % NO/He) was then passed through the surfaces for an hour for their saturation with NH 3 (or NO) at 180 °C (or 350 °C) and was altered to a He before the surfaces were heated to 700 °C under He with the a ramping rate (β) of 10, 20, or 30 for collecting the profiles of the NH 3 signal ( m / z ∼17) (or NO signal ( m / z ∼30)) versus temperature. These profiles were then deconvoluted into two or three sub-bands, each of which could provide the temperature with maximum intensity (denoted as T M ). − The energies required for the desorption of NH 3 (or NO) on the material surfaces (denoted as E ZZ where ZZ indicates NH 3 or NO) were evaluated using TPD theorem − whose specifics can be found in eq where R and θ M indicate the gas constant (8.314 J mol –1 K –1 ) and surface coverage of NH 3 (or NO) at T M , respectively, whereas ν n and n are lumped constants indigenous to the surfaces. Equation could allow for the construction of ln­(β/ T M 2 ) versus 1/ T M for the materials, whose slope is − E NH3 / R (or − E NO / R ) upon the presumption that E NH3 (or E NO ) is constant and independent to the surface coverage of NH 3 (or NO) ( e .…”

“…Equation could allow for the construction of ln­(β/ T M 2 ) versus 1/ T M for the materials, whose slope is − E NH3 / R (or − E NO / R ) upon the presumption that E NH3 (or E NO ) is constant and independent to the surface coverage of NH 3 (or NO) ( e . g ., θ M ). − …”