Microwave-assisted alkyne semihydrogenation with lead-free Pd catalysts: from batch to flow reactors

21 July 2021

AperTO - Archivio Istituzionale Open Access dell'Università di Torino

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Microwave-assisted alkyne semihydrogenation with lead-free Pd catalysts: from batch to flow reactors

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100 99.8 99.6 99.4 99.2 99.0 98.8 98.6 98.4 98.2 98.0 W ei gh t % (%) 25 40 60 80 100 120 140 150 Temperature (°C)

TGA

0 1 2 3 4 5 0 5 10 15 20 25 30 35 40 45 Rel ati v e F requenc y [% ] Pd particle size [nm]

NOVACAM is a coordinated EU-Japan project supported by the European Union and the

Japan Science and Technology Agency. This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and

demonstration under grant agreement no 604319.

www.novacam.eu

Microwave-assisted alkyne

semi-hydrogenation with lead-free Pd catalysts:

from batch to flow reactors

Laura Rotolo, Zhilin Wu, Maela Manzoli, Emanuela Calcio Gaudino, Giancarlo Cravotto.

Dep. of Drug Science and Technology and NIS - Centre for Nanostructured Interfaces and Surfaces, via P. Giuria 9, University of Turin, Turin, Italy.

• Based on previous results achieved with boehmite supported Pd catalyst 2,3 we design a new procedure under non-conventional conditions for the preparation of Pd supported alumina beats to be used in alkyne semi-hydrogenations.

Introduction

Structure - activity relationship

References

1 _{Wu, Z., Borretto, E., Medlock, J., Bonrath, W., Cravotto, G., ChemCatChem, 6 (2014), 2762 –2783.}

2 _{Wu, Z.; Cherkasov, N.; Cravotto, G.; Borretto, E.; Ibhadon, A. O.; Medlock, J.; Bonrath, W. ChemCatChem (2015), 7 (6), 952–959.} 3 _{Wu, Z.; Cravotto, G.; Calcio Gaudino, E.; Medlock, J.; Bonrath, W.; Ultrason. Sonochem. (2016), 35, 664-672.}

4 _{Kappe, C. O., Angew. Chem. Int. Ed., 43 (2004), 6250-6284; Angew. Chem., 116 (2004), 6408 –6443}

5 _{Wu, Z.; Rotolo, L.; Calcio Gaudino, E.; Medlock, J.; Bonrath, W.; Cravotto, G.; Chem. Eng. Process. (2016), 110, 220-224}

• The effect of environmentally benign enabling technologies such as ultrasound and microwaves on the preparation of lead-free Pd catalysts for selective hydrogenation has been studied1.

• Lindlar catalyst was an industrial standard for more than 50 years. Because of lead toxicity, there is a drive to develop new lead-free semi-hydrogenation catalysts

.

FRESH catalyst

USED catalyst

Catalyst was prepared by impregnation technique in oil bath at 80 °C for 2h with n-propanol as solvent. The Pd(OAc)₂ precursor was pre-dispersed in ultrasound (US) using a cavitating tube (Danacamerini - Turin)

H₂ MW (flow mode)

Flow MW Reactor

Conv. > 85% - Sel. > 90% ICP-MS: Pd content = 126.15 mg/kg

Total Pd leaching after semi-hydrogenation test: 22.76% 20 l of alkyne solution

Moreover, no peaks due to the presence of crystalline Pd in the XRD pattern of the catalyst [email protected] Cavitating tube (19.9 kHz, 100 W) US

50000 X

300000 X

Pd particle size distribution

Schematic cross sections of the Pd distribution in the catalyst pellet (egg-shell): Metallic Pd 200 (cubic) 00-001-1312 XRD analysis: bare support 20 40 60 80 100 0 500 1000 1500 2000 2500 3000 X

= Mg silicate, MgSiO₃ (orthorombic) 00-003-0519

*

= Mg silicate, MgSiO₄ (orthorombic) 00-034-0189 O= Mg, Al oxide (monoclinic) 00-010-0238 X X O O O O * * * * * * 042 137 232 1112 226 0012 0012 312 306 125 125 125 214 122 122 211 202 202 110 110 Cps 2 Theta 110 * O X Al 2O3, corundum (rombhoedral) 00-001-1296

US promotes nucleation rather than the growth of crystalline Pd nanoparticles

The pre-dispersion of the Pd precursor in ultrasound (US) led to the formation of Pd nanoparticles on the catalyst surface

Milestone

FlowSYNTH

Gas flow-meter

Catalyst Preparation

Catalyst reactor chamber