Synthesis of 2-Methylpyrazine Over Highly Dispersed Copper Catalysts

Abstract

A series of CuCoAl catalysts were synthesized by co-precipitation and impregnation methods, tested in synthesis of 2-methylpyrazine (2-MP) and characterized by X-ray diffraction, N 2 adsorption, thermo-gravimetry analysis, H 2 -temperature-programmed reduction, dissociative N 2 O adsorption and temperature-programmed oxidation. The precursors prepared by co-precipitation method shows a well-crystallized hydrotalcite. The study proves that the calcination temperature of hydrotalcite has a significant effect on the catalyst surface area, crystallite size and copper dispersion. In comparison with catalyst prepared by impregnation, the catalyst prepared by co-precipitation method calcined at 500°C exhibits higher specific surface area, higher copper dispersion and the better reducibility. Consequently, CuCoAl catalyst derived from hydrotalcite is more active and selective for synthesis of 2-MP. Moreover, it shows the better stability due to the good resistance to coke formation.

Facile synthesis of CuMAl (M = Cr, Mn, Zn, and Co) with highly dispersed Cu and tailorable surface acidity for efficient 2-methylpyrazine synthesis

“…As previously reported for Co(Zn)-Al LDH samples, excess aluminum segregates to form additional phases such as gibbsite AlO(OH) at 2q ¼ 37.4 , 16,17 instead of incorporating into the hydrotalcite-type structure. 7,18 Hence, these results support our results showing the formation of an Al(OH) 3 phase from excess Al in the CuAl, CuZnAl, and CuCoAl samples. While for the case of CuCrAl sample neither Al(OH) 3 nor hydrotalcite-like crystallite phases (i.e., amorphous CuCrAl) was found, probably due to the low kinetic crystallization constant of Cr 3+ .…”

“…CuMAl LDH precursors (M ¼ Co, Zn, Cr, and Mn) were prepared by a conventional Na 2 CO 3 /NaOH co-precipitation method. 7 Typically, 100 mL of a mixed metal solution, containing 1 M of cations (Cu(NO 3 ) 2 $6H 2 O, M(NO 3 ) x $yH 2 O, and Al(NO 3 ) 3 $9H 2 O), with the desired molar ratio and 100 mL of a mixed basic solution consisting of NaOH and Na 2 CO 3 with […”

“…Usually, increasing the metal loading may result in the formation of large copper particles and thus poor catalytic activity. 7 Thermal decomposition of layered double hydroxides (LDHs) is an attractive approach to obtain uniformly distributed metal nanoparticles. [7][8][9][10][11] Venugopal et al prepared LDHs-derived Cu/Zn-Cr-O catalysts and used them in the synthesis of 2,6dimethylpyrazine.…”

“…7 Thermal decomposition of layered double hydroxides (LDHs) is an attractive approach to obtain uniformly distributed metal nanoparticles. [7][8][9][10][11] Venugopal et al prepared LDHs-derived Cu/Zn-Cr-O catalysts and used them in the synthesis of 2,6dimethylpyrazine. However, the low surface area (50 m 2 g À1 ) and the large CuO x crystalline size (5.8 nm) of the catalyst resulted in a poor glycerol conversion (9%) at 375 C. 9 The formation of the LDH precursor can be signicantly altered by changing the secondary metal element (M) in CuMAl catalysts, thereby potentially leading to higher metallic Cu dispersion.…”

Activation and Decomposition of Methane over Cobalt‐, Copper‐, and Iron‐Based Heterogeneous Catalysts for COx‐Free Hydrogen and Multiwalled Carbon Nanotube Production

“…The amount of hydrogen consumed in the second TPR step was denoted as y . The dispersion of metal was calculated according to literature correlations …”