Selective Catalytic Reduction of NO_x by Hydrocarbons/Oxygenates. Application for the Control of NO_x from the Regenerator of a Fluid Catalytic Cracking Pilot-Plant Unit

Abstract

Rh supported on γ-alumina and unpromoted γ-alumina were used as catalysts for the selective catalytic reduction of NO by propene and methanol, respectively. Fixed-bed experiments were initially performed to study the catalytic activity using a feed that simulates flue gases. Emphasis was placed on the SO2 effect on the NO reduction activity. A fluidized-bed deNO x unit was connected to the exit of the regenerator of a pilot-plant-scale fluid catalytic cracking unit aiming at the cleanup of this stream from gaseous pollutants. The deNO x catalysts and the reductants were the same as those in the fixed-bed experiments. More than 70% of the incoming NO was converted to N2 when the deNO x unit was operated at the appropriate temperature range. Moreover, up to 90% of the inlet CO was oxidized to CO2 at sufficiently high temperatures. At the same temperatures SO2 was adsorbed by alumina.

deNO x reduction by methanol over Co/alumina

“…The deNO x process, in the presence of transition metal cations [10], requires three kinetically uncoupled functions: (i) oxidation of NO to NO 2 ; (ii) mild oxidation of hydrocarbons to alcohol and aldehyde, in the presence of NO 2 ; (iii) reduction of NO to N 2 , assisted by the deep oxidation of the alcohol or aldehyde to CO 2 . According to this model, the first function (oxidation of NO to NO 2 ) was observed on both alumina and 0.5 wt%Co/Al 2 O 3.…”

“…Most of NO x reduction performed in these conditions has been described using zeolites or oxides associated with C1-C4 hydrocarbons [1][2][3][4][5] or alcohols [6][7][8][9][10][11][12][13][14] as reductants. Methanol associated with alumina modified by sulfatation or transition metal oxides have received increasing attention [6][7][8][9][10]. We studied the deNO x reduction by methanol over Co/ alumina catalysts and we discuss the results according to a general model based on ''three-function catalysts'' [15].…”

Effects of CH4 and CO on the Reduction of Nitric Oxide to Nitrogen in a Discharge Reactor

“…1,2 The typical emission control strategy of NO x has been intensively implemented via the catalytic process through the addition of reductant. 3,4 Recently, one method attempted to improve the catalyst feasibility at lower temperatures is by using the nonthermal plasma approach. Plasma seems particularly effective when the flow rate of effluents is lower, such as in the ranges of several to tens of standard liters min Ϫ1 (slms) through a dielectric-barrier discharge (DBD) or corona discharge process.…”

“…9,10 Most of the NO conversion in N 2 /O 2 /H 2 O mixtures achieved via the plasma approach is a result of processing oxidation reaction, leading to the common final products of NO 2 , NO 3 , and HNO 3 , and only a small fraction can be caused by the reduction process. 7,[11][12][13] However, in an application like automobile exhaust gas treatment, reducing NO to N 2 is attractive, because no additional process, such as a scrubbing system, is needed for further treatment.…”

“…To enhance the NO conversion, a process including the injection of NH 3 or Ca(OH) 2 into the stream has been used to neutralize the acids and to terminate reverse reactions. 8,16 In addition, a cheap additive, such as CH 4 , as well as CO and CO 2 , which are usually generated from combustion itself, have been used to assist in NO removal and to enhance NO conversion.…”