On the Kinetics of the Absorption of Nitric Oxide into Ammoniacal Cobalt(II) Solutions

Abstract

Experiments were conducted using a custom double-stirred tank reactor to determine the rate constants of reactions between nitric oxide (NO) and both pentaaminecobalt(II) and hexaaminecobalt(II) at temperatures of 298.2 and 303.2 K and pH levels between 8.50 and 9.87 under atmospheric pressure. The NO concentration of simulated flue gas stream ranged from 400 to 1400 ppmv. Ammoniacal cobalt(II) solutions were prepared by adding aqueous ammonia into a cobalt(II) nitrate solution in the presence of concentrated ammonium nitrate. The reaction rate constants were calculated with an enhancement factor for gas absorption associated with parallel chemical reactions. The results showed that the reaction between NO and pentaaminecobalt(II) was first order with respect to both the NO and the pentaamminecobalt(II) ion. Similarly, the reaction between NO and hexaamminecobalt(II) was first order with respect to both the NO and the hexaamminecobalt(II) ion. The forward reaction rate constants of these two reactions were 6.43 × 10(6) and 1.00 × 10(7) L · mol(-1) · s(-1) at 298.2 K, respectively, and increased to 7.57 × 10(6) and 1.12 × 10(7) L · mol(-1) · s(-1) at 303.2 K, respectively. Ammoniacal cobalt(II) solutions also have the potential to simultaneously remove CO2, SO2, and NOx from postcombustion flue gas.

Kinetics of the absorption of carbon dioxide into aqueous ammonia solutions

“…CO 2 absorption took place in a DSTR filled with 500 mL of ammonia at a concentration between 0.42 and 7.67 kmol·m −3 . The details of the absorber can be found elsewhere . Briefly, the reactor was operated continuously with respect to the gas phase and batch‐wise with respect to the liquid phase.…”

“…Besides temperature, ionic strength also plays an important role in the Henry's Law constant . In this study, the aqueous ammonia solution has a concentration of 0.42–7.67 kmol·m −3 .…”

“…For example, they concluded that the reaction order with respect to CO 2 was zero but their measured absorption rate increased linearly with the rising CO 2 concentration, which indicated a first order with respect to CO 2 . This type of reactor has also found numerous applications in the study of nitric oxide absorption into solutions …”

Experimental investigation of nitric oxide removal from flue gas using hexamminecobalt(II) solution scrubbing in a pilot-scale facility

“…They also investigated the regeneration and kinetics of the gas–liquid reaction between NO and hexamminecobalt(II) (Long et al, 2004). Yu compared the denitration performances of iron( 2+ )(Fe(II)–EDTA), hexamminecobalt(II) chloride ([Co(NH 3 ) 6 ]Cl 2 ), and hydrogen peroxide (H 2 O 2 ) (Yu, 2012; Yu and Tan, 2013, 2014). Liu Z conducted experimental studies on the influence of operating conditions on NO and SO 2 removal performances (Liu Z et al, 2016) .…”

Removal of nitric oxide in a microporous tube‐in‐tube microchannel reactor by ferrous chelate solution

“…In the past decades, various technologies have been developed to reduce NO emission, mainly including combustion modification and flue gas treatment . Among them, wet scrubbing technology is considered to be a promising and cost‐effective approach.…”