Selective gas phase hydrogenation of p-nitrobenzonitrile to p-aminobenzonitrile over zirconia supported gold

Abstract

The catalytic action of Au/ZrO2 in the gas phase hydrogenation of p-nitrobenzonitrile (p-NBN) to p-aminobenzonitrile (p-ABN) has been assessed against Au/Al2O3. Crystalline ZrO2 was prepared by precipitation of ZrOCl2 with aqueous NH3 and calcined to generate tetragonal and monoclinic phases. Catalyst and support were characterised by surface area/porosity, temperature-programmed reduction (TPR), H2 chemisorption/temperature programmed desorption (TPD), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Xray photoelectron spectroscopy (XPS) measurements. Higher calcination temperatures (673-973 K) increased the monoclinic ZrO2 content with a decrease in surface area and pore volume. Introduction of Au by deposition-precipitation resulted in tetragonal→monoclinic transformation with post-TPR formation of Au particles in the 3-13 nm size range and electron transfer from ZrO2. Reaction over Au/ZrO2 delivered 100% p-ABN yield with higher turnover frequency (267 h-1) than Au/Al2O3 (109 h-1) attributed to greater H2 chemisorption capacity under reaction conditions and enhanced −NO2 activation. Au/ZrO2 outperformed benchmark Pd/Al2O3 and Ni/Al2O3, which generated p-aminotoluene via subsequent hydrogenation/hydrogenolysis.

Continuous gas phase catalytic transformation of levulinic acid to γ‐valerolactone over supported Au catalysts

“…To the best of our knowledge, this is the first report of 100% GVL yield in continuous operation with full hydrogen utilisation. Under these reaction conditions, Pd/Al 2 O 3 delivered a higher LA consumption rate than Au/Al 2 O 3 (1090 vs 300 mmol GVL g metal −1 h −1 ), that correlates well with the reported higher activity for Pd (vs Au) in hydrogenation but promoted undesired pentanoic acid ( S Pentanoic acid = 10%). We have recorded 100% yield of GVL with an order of magnitude greater productivity relative to the state‐of‐the art supported Pd and Ru catalysts .…”

Gas phase selective hydrogenation of phenylacetylene to styrene over Au/Al2O3

“…(C). Hydrogen uptake measured at ambient temperature (Table ) was low suggesting limited capacity to chemisorb H 2 , as has been noted elsewhere for a range of Au systems . Uptake was appreciably higher at 423 K (median reaction temperature), indicating that H 2 chemisorption on supported Au is an activated process.…”

“…Hydrogen uptake measured at ambient temperature (Table 1) was low suggesting limited capacity to chemisorb H 2 , as has been noted elsewhere for a range of Au systems. 25,40,41 Uptake was appreciably higher at 423 K (median reaction temperature), indicating that H 2 chemisorption on supported Au is an activated process. Although we could find no reported chemisorption values to relate to our measurements, van Bokhoven and co-workers 39,42 and Lin et al 43 have proposed enhanced H 2 activation on Au/Al 2 O 3 and Au/TiO 2 , respectively, at higher temperatures.…”

Formic Acid or Formate Derivatives as the In Situ Hydrogen Source in Au‐Catalyzed Reduction of para‐Chloronitrobenzene

“…Table shows hydrogenation activity of p ‐CNB over Au/ZrO 2 catalyst with varied hydrogen sources. Au/ZrO 2 catalyst was firstly chosen to investigate the effect of hydrogen source on the hydrogenation of p ‐CNB, since Au/ZrO 2 was reported as high performance on the hydrogenation of p ‐CNB and dehydrogenation of HCOOH ,. When H 2 was used as hydrogen source, p ‐CNB conversion over Au/ZrO 2 catalyst was 25.0%.…”