Ammoxidation of toluene on vanadyl polyphosphates-VO(PO3)2, 2. Catalytic properties

Abstract

Crystalline and amorphous vanadyl polyphosphates (VO(PO3)2) with a P/V ratio = 2 were used as catalysts in the ammoxidation of tohene, The crystalline specimens exhibit a rather low activity compared with the amorphous solid, The benzonitrile selectivities always reached nearly 90%. Noticeable benzaldehyde amounts were detected that could be due to an inadequate ammonia activation on the solid surface.

Unprecedented Catalysis of Cs+ Single Sites Confined in Y Zeolite Pores for Selective Csp3–H Bond Ammoxidation: Transformation of Inactive Cs+ Ions with a Noble Gas Electronic Structure to Active Cs+ Single Sites

“…Here, we report the first example of the catalytic selective activation of C sp3 –H bonds to produce C–N bonds on Cs + single ion sites in Y zeolite pores (Cs + /Y) due to transformation of inactive Cs + ions with a noble gas electronic structure to active Cs + sites with HOMO­(O 2p)–LUMO­(Cs 6s) by chemical confinement of Cs + ions at Y zeolite pore surfaces, making Cs–O bonds and reactive coordination. Ammoxidation of methyl C sp3 –H bonds of aromatics with O 2 + NH 3 is an avenue for the synthesis of organic nitriles, which have been commercially used as common building blocks for high-performance rubbers, polymers, and molecular electronics and also as integral parts for producing pharmaceuticals, agrochemicals, and fine chemicals, such as vitamins, heterocycles, and various carboxylic acid derivatives. , Generally, organic nitriles were synthesized by cyanation of aldehydes using toxic hydrogen cyanide and metal cyanides, which caused environmental disasters. ,− Industrially, the vapor-phase ammoxidation of toluene to benzonitrile has been extensively studied with metal and metal oxide catalysts of V, Cr, Mo, etc., − whose catalysts possess moderate redox potentials and sufficient M–O bond strengths to provide active lattice oxygen and oxygen atoms at the catalyst surfaces for the redox catalysis. The Cs + /Y catalyst without a beneficial redox property showed a high benzonitrile yield (92.7% yield; 94.6% conversion and 98.0% selectivity at 623 K) and a high NH 3 utilization efficiency (almost no extra consumption) in toluene ammoxidation employed as a test reaction; to the best of our knowledge, this is the highest yield without NH 3 loss for the benzonitrile synthesis from toluene with O 2 + NH 3 in a single-step gas-phase reaction.…”

Vanadium–phosphorous oxide supported on mesoporous SBA-15 catalysts for ammoxidation of toluene to benzonitrile

“…Moreover, they observed a noticeable amount of benzaldehyde in the product mixture due to low adsorption of ammonium ions. 38 Ch. Srilaxmi et al studied the ammoxidation of 2-methyl pyrazine into 2-cyanopyrazine over α- and β-VOPO 4 samples and found that the α-VOPO 4 phase is slightly more active than β-VOPO 4 due to the existence of different structures.…”

NH3-efficient ammoxidation of toluene by hydrothermally synthesized layered tungsten-vanadium complex metal oxides

“…Ammoxidation of methyl-substituted aromatics such as toluene, xylene and methylpyridine to their corresponding nitriles is an industrially important reaction, and numerous reports have been dealt with this reaction [1][2][3][4]. The vapor phase ammoxidation of toluene to benzonitrile has been extensively studied as a model reaction [5][6][7][8][9][10][11][12][13][14][15][16]. Various metal oxide-based catalysts, including vanadium (V)-based catalysts (V 2 O 5 [5], VO x /TiO 2 [6,7], VO x /ZrO 2 [8], V 2 O 5 /Nb 2 O 5 -TiO 2 [9], (VO) 2 P 2 O 7 [10][11][12][13]) and other catalysts (MoO x /Nb 2 O 5 [13], MoO x /ZrO 2 [15], Fe-based mixed oxides [16]) have been reported to show moderate to good yields (44-77%) of benzonitrile (based on toluene) at around 400 ˚C [5][6][7][8][9][10][11][12][13][14][15][16].…”