Selective formation of aniline over nanogold incorporated cobalt loaded SBA 15 catalysts

Selective Liquid‐Phase Hydrogenation of a Nitro Group in Substituted Nitrobenzenes over Au/Al2O3 Catalyst in a Packed‐Bed Flow Reactor

“…One can assume that in the given case aggregation of the smallest gold nanoparticles proceeds through a dissolution–redeposition mechanism (the so‐called Ostwald ripening of gold) and/or as an on‐surface particle migration–coalescence process. Both can be aided by aromatic amine formed, which is present in the reaction stream in a high concentration and may interact with gold nanoparticles to promote their reversible dissolution in an organic solvent . An increase in the d s value for gold particles registered after two successive catalytic runs means a decrease in the total surface of supported gold nanoparticles by a factor of 1.8 (assuming a simple model of gold nanospheres) and the corresponding reduction in the observed activity of the catalyst if it is in direct proportion to the amount of surface gold atoms.…”

“…Both can be aided by aromatic amine formed,w hichi sp resent in the reaction streami n ah igh concentration and may interactw ith gold nanoparticles to promote their reversible dissolution in an organic solvent. [12] An increase in the d s value for gold particles registered after two successive catalytic runs meansadecrease in the total surface of supported gold nanoparticles by af actor of 1.8 (assuming as imple model of gold nanospheres [25] )a nd the corresponding reduction in the observed activityo ft he catalyst if it is in directp roportion to the amounto fs urfaceg old atoms. Thus, the agglomeration of Au particles is probably another factor that causes the deactivationo ft he Au/Al 2 O 3 catalyst ChemPlusChem 2015, 80,1741 -1749 www.chempluschem.org during the liquid-phase hydrogenation of substituted nitrobenzenes under flow conditions.…”

“…Viswanathan et al. also noted that the catalytic performance of supported gold strongly depended on the porous nature of the support because it might play an important role in stabilizing the efficient dispersion of gold nanoparticles or vice versa in facilitating metal particle agglomeration …”

“…[8,9,11] Viswanathan et al also noted that the catalytic performance of supported gold strongly dependedo nt he porous nature of the support because it might play an important role in stabilizing the efficient dispersion of gold nanoparticles or vice versa in facilitating metal particle agglomeration. [12] To date, hydrogenation of aromatic nitro compounds was performed in either liquid-phase batch reactors [5][6][7][8] or gasphase flow reactors [4,9,10] and,t ot he besto fo ur knowledge, has never been examined under continuous liquid-phase flow conditions. Meanwhile,t he last decadeh as witnessed rapid As eries of substituted nitrobenzenes with the general formula XC 6 H 4 NO 2 (X = Cl, CH=CH 2 ,o rC (O)CH 3 )d issolved in toluene were reduced with hydrogen over the 1.9 %A u/Al 2 O 3 catalyst at 60-110 8Ca nd 10-20 bar in at hree-phase packed-bed reactor operating in up-flow mode.…”