Pd-W and Pd-Mo catalysts for NO decomposition and NO/CO reduction reactions

Abstract

Pd/γ-Al 2 O 3 catalysts with two different metal particle sizes were prepared from [Pd(acac) 2 ]. Subsequently, the photochemical reaction of [M(CO) 6 ] (M = Mo or W) in the presence of Pd/γ-Al 2 O 3 was used to prepare bimetallic Pd-M/γ-Al 2 O 3 catalysts. DRIFTS FTIR spectra of the catalyst surfaces prior to thermal decomposition showed unstable subcarbonyl [M(CO) n ] species. Chemisorption and CO/NO adsorption results indicated a blockage of the Pd active sites when the second metal was incorporated. The catalytic activity and the selectivity for the NO/CO reaction were higher for Pd with higher particle size, but they were both inhibited when Mo or W were incorporated. On the other hand, when the catalysts were tested for NO decomposition, the presence of Mo or W led to an increase in the catalytic activity, with optimal results observed in the presence of Mo.

Understanding the chemical state of palladium during the direct NO decomposition – influence of pretreatment environment and reaction temperature

“…For instance, the performance of supported noble metal catalyst, which is the commercialized component of three-way catalyst, was only addressed in a few reports for direct NO decomposition. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Pt based catalysts were investigated in early 20 th century and found out that the catalysts deactivates quickly at lower temperatures. [16][17][18][19] Recently, studies have been focused on investigating palladium based catalysts for direct NO decomposition because of its better thermal stability and low cost compared to Pt based catalysts.…”

“…[16][17][18][19] Recently, studies have been focused on investigating palladium based catalysts for direct NO decomposition because of its better thermal stability and low cost compared to Pt based catalysts. [20][21][22][23][24][25][26][27][28][29][30] Most of the reports concentrated on the performance of supported palladium catalyst in direct NO decomposition at various reaction temperatures (from 300 C to 900 C). [20][21][22][23][24][25][26][27][28][29][30] However, a very deep understanding about the function and chemical state of the palladium during direct NO decomposition at different reaction temperatures has not been attained.…”

“…[20][21][22][23][24][25][26][27][28][29][30] Most of the reports concentrated on the performance of supported palladium catalyst in direct NO decomposition at various reaction temperatures (from 300 C to 900 C). [20][21][22][23][24][25][26][27][28][29][30] However, a very deep understanding about the function and chemical state of the palladium during direct NO decomposition at different reaction temperatures has not been attained. For example, Baibich group [26][27][28][29] evaluated several supported and bimetallic Pd catalysts for direct NO decomposition and reported that metallic Pd catalysts deactivate with time irrespective of support and foreign metal.…”

“…[20][21][22][23][24][25][26][27][28][29][30] However, a very deep understanding about the function and chemical state of the palladium during direct NO decomposition at different reaction temperatures has not been attained. For example, Baibich group [26][27][28][29] evaluated several supported and bimetallic Pd catalysts for direct NO decomposition and reported that metallic Pd catalysts deactivate with time irrespective of support and foreign metal. On the other hand, Naito et al 30 reported that metallic Pd supported on SiO 2 catalyst exhibits a stable NO conversion aer forming few oxygen layers on the surface.…”

Synergistic Effects of Bimetallic AuPd and La2O3 in the Catalytic Reduction of NO with CO

“…Nitric oxide and carbon monoxide emitted from internal combustion engines are dangerous to public health and ecological balance [12]. Noble metals such as Rh, Pt, and Pd supported on metal oxides have been extensively explored for eliminating NO and CO simultaneously [13][14][15][16][17][18][19][20]. Catalytic reduction of NO with CO proceeds via the formation of isocyanate (-NCO) species and their reaction with NO to form N 2 and CO 2 [14].…”