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Commercial catalysts screening for the direct amination of cyclohexanol
Rui Churro,Fernando Mendes,Paulo Araújo,Luís M. Madeira,Filipa Ribeiro 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.95 No.-
Two groups of commercially available Ni- and Pd-based catalysts were used for the direct amination ofcyclohexanol (CHOL) with NH3 as aminating agent and in the presence of H2, aiming the selectiveproduction of cyclohexylamine (CHA) and aniline. The fresh catalysts were characterized in terms ofmetal loading, support composition (prevailing SiO2 and Al2O3) and metallic dispersion. Ni-basedcatalysts revealed to be highly active while Pd-based were more selective towards aniline, howeverrequiring higher temperatures and catalyst loading to reach significant CHOL conversions (from 17 up to67 %). The activity of the catalysts is intrinsically related to their metallic dispersion regardless the metalloading. The Ni-based catalyst with 46 wt. % of Ni is the most promising once it presents higher turnoverfrequency (TOF) values, as 10 fold high, particularly related to the ratio of desired to undesired by-products. Moreover, operating conditions considerably affect catalysts’ performance.
Pedro S. F. Mendes,João M. Silva,M. Filipa Ribeiro,Antoine Daudin,Christophe Bouchy 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.62 No.-
The development of zeolite-based hydroisomerization catalysts in the powder form is widely spread in scientific literature but shaped bodies are the ones being employed in industry. This work aims at bridging that gap. The shaping procedure for HUSY zeolite in presence of an alumina binder disclosed herein achieved a full conservation of zeolite properties, e.g. porosity and Brønsted acidity. When Pt was located inside the zeolite and an homogeneous Pt distribution along the extrudate was ensured, shaped Pt-containing catalysts had similar hydroisomerization performances to those of powder Pt/zeolite in terms of turnover frequency per Brønsted acid site and maximal feed isomers yield. Conversely, non-uniform distribution of Pt along the extrudates diameter (millimetric scale) was observed to reduce the feed isomers yield. This was tentatively explained by the lower local metal to acid sites ratio in the core of the extrudates. Optimal performance of shaped bifunctional catalysts requires, hence, an adequate metal to acid sites ratio throughout the whole catalyst (i.e. at millimetric and nanometric scale), even if full intimacy between catalytic functions is ensured at the nanoscale by the selective deposition of Pt inside the zeolite.
Pedro S. F. Mendes,Joao M. Silva,M. Filipa Ribeiro,Christophe Bouchy,Antoine Daudin 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.71 No.-
The inhibition of Brønsted acid sites by nitrogen-containing molecules was quantified under industriallyrelevant hydrocracking conditions. This was achieved by testing bifunctional catalysts based on HUSYzeolite in cyclohexane hydroconversion. For ammonia partial pressures within 0.2-2.8 kPa, thepercentage of inhibited Brønsted sites was superior to 98% at 623 K. Significant reduction in theammonia content caused rather moderate variations on the number of available sites. Conversely, atemperature raise from 600 to 640 K triplicated the vacant Brønsted sites due to the significantendothermicity of ammonia desorption. The inhibiting effect of ammonia can be therefore easilymodulated by temperature.