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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

Membrane reactors enable hydrogenation in ambient conditions without direct H2 input. We can track the hydrogen production and utilization in these systems using atmospheric mass spectrometry (atm-MS) and gas chromatography mass spectrometry (GC-MS).

Abstract

Industrial hydrogenation consumes ~11 Mt of fossil-derived H2 gas yearly. Our group invented a membrane reactor to bypass the need to use H2 gas for hydrogenation chemistry. The membrane reactor sources hydrogen from water and drives reactions using renewable electricity. In this reactor, a thin piece of Pd separates an electrochemical hydrogen production compartment from a chemical hydrogenation compartment. The Pd in the membrane reactor acts as (i) a hydrogen-selective membrane, (ii) a cathode, and (iii) a catalyst for hydrogenation. Herein, we report the use of atmospheric mass spectrometry (atm-MS) and gas chromatography mass spectrometry (GC-MS) to demonstrate that an applied electrochemical bias across a Pd membrane enables efficient hydrogenation without direct H2 input in a membrane reactor. With atm-MS, we measured a hydrogen permeation of 73%, which enabled the hydrogenation of propiophenone to propylbenzene with 100% selectivity, as measured by GC-MS. In contrast to conventional electrochemical hydrogenation, which is limited to low concentrations of starting material dissolved in a protic electrolyte, the physical separation of hydrogen production from utilization in the membrane reactor enables hydrogenation in any solvent or at any concentration. The use of high concentrations and a wide range of solvents is particularly important for reactor scalability and future commercialization.

Introduction

Thermochemical hydrogenation reactions are used in ~20% of all chemical synthesis1. These reactions require large quantities of H2 gas, which are usually derived from fossil fuels, temperatures between 150 °C and 600 °C, and pressures up to 200 atm2. Electrochemical hydrogenation is an appealing way to bypass these requirements and to drive hydrogenation reactions using water and renewable electricity3. For conventional electrochemical hydrogenation, an unsaturated feedstock is dissolved in a protic electrolyte in an electrochemical cell. When a potential is applied to the cel....

Protocol

1. Pd rolling

  1. Clean the Pd wafer bar with a mixture of hexanes using a cotton cloth.
    CAUTION: Hexane is flammable, a health hazard, an irritant, and environmentally damaging. Work under proper ventilation (i.e., a snorkel or a fume hood).
  2. Roll the Pd wafer using a manual roller until reaching a thickness of ≤150 µm, as determined by a digital micrometer.
  3. Roll the Pd using an automatic roller to a thickness of 25 µm, as determined by a digital microme.......

Representative Results

Atm-MS is used to measure the ionic current of the hydrogen that is produced in the membrane reactor. We can use these measurements to quantify how much hydrogen permeates through the Pd membrane during electrolysis. First, the hydrogen evolving from the hydrogenation compartment is measured (Figure 3, left of the dotted lines). When the signal reaches a steady state, the channel is switched to the electrochemical compartment. The H2 gas evolving from the electrochemical compartme.......

Discussion

The Pd membrane enables hydrogen permeation and chemical hydrogenation. The preparation of this membrane is, therefore, important to the efficacy of the membrane reactor. The Pd membrane size, crystallography, and surface are tuned to improve the experimental results. Although Pd metal can evolve hydrogen at any thickness, the Pd membranes are rolled to 25 µm. This standardization of membrane thickness ensures that the time it takes for hydrogen to permeate through the membrane is constant for all the experiments. M.......

Acknowledgements

We are grateful to the Canadian Natural Sciences and Engineering Research Council (RGPIN-2018-06748), the Canadian Foundation for Innovation (229288), the Canadian Institute for Advanced Research (BSE-BERL-162173), and Canada Research Chairs for financial support. This research was undertaken thanks in part to funding from the Canada First Research Excellence Fund, Quantum Materials and Future Technologies Program. We thank Ben Herring at the UBC Shared Instrument Facility for assistance with the GC-MS instrument and method development. We thank Dr. Monika Stolar for contributions to the development and editing of this manuscript. Finally, we thank the entire Berlingu....

Materials

NameCompanyCatalog NumberComments
Ag/AgCl Reference ElectrodeBASi research productsMW-2021Reference electrode
Analytical BalanceCole-ParmerRK-11219-03Instrument
Atmospheric Mass SpectrometerESS CatalySysNAInstrument
Bench Power SupplyNewark1550Instrument
Conductive Copper Foil Electrical Tape McMaster Carr76555A711Electrochemical cell assembly
DichloromethaneSigma Aldrich270997Reagent
Electric Rolling Press with Dual MicrometerMTI CorporationMR100AEquipment
Electrochemical glass H-cellUniversity of British Columbia glass blowingNAElectrochemical cell assembly
ESS catalysis QUADSTARESS CatalySysNASoftware
EthanolSigma Aldrich493511Reagent
Flat Rolling MillPepetolls18700AEquipment
Gas Chromatography Mass SpectrometerAgilentNAInstrument
GC-MS vialAgilent5067-0205Vial for GC-MS
HexanesSigma Aldrich1.0706Reagent
Hydrochloric AcidSigma Aldrich258148Reagent
Hydrogen peroxide solution (30% v/v)Sigma AldrichH1009Reagent
Isopropyl AlcoholSigma AldrichW292907Reagent
Masshunter Aquisition SoftwareAgilentG1617FASoftware
Micropipette (100 µL - 1000 µL)GilsonF123602instrument
Micropipette (20 µL - 200 µL) GilsonF123601Instrument
Mitutoyo Digital MicrometerUlineH-2780Instrument
Muffle FurnaceMTI CorporationKSL-1100XEquipment
Nitric acidSigma Aldrich438073Reagent
Nitrogen gasSigma Aldrich608661Reagent
Palladium (II) ChlorideSigma Aldrich520659Reagent
Pd wafer bar, 1 oz, 99.95%Silver Gold Bull.NAReagent
Platinum Auxiliary ElectrodeBASi research productsMW-1032Anode
PotentiostatMetrohmPGSTAT302NInstrument
PropiophenoneSigma AldrichP51605Reagent
Proton Exchange Membrane, Nafion 212Fuel cell store NAElectrochemical cell assembly
Sulfuric acid Sigma Aldrich258105Reagent

References

  1. Rytter, E., Hillestad, M., Austbø, B., Lamb, J. J., Sarker, S., Lamb, J. J., Pollet, B. G. Chapter six - Thermochemical production of fuels. Hydrogen, Biomass and Bioenergy. , 89-117 (2020).
  2. Arpe, H. -. J. . Industrial Organic Chemistry. , (2017).
  3. Orella, M....

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