Core Technologies

Hydrogenolysis

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Hydrogenolysis

Hydrogenolysis is a reaction where hydrogen is added to a compound and breaks that compound’s bonds, forming two molecules as a result.

In Context

JM Davy’s hydrogenolysis technology reacts hydrogen gas (H2) with a vapour-phase carbonyl compound.

We employ Davy hydrogenolysis in various flowsheets, including our natural detergent alcohols (NDA) process, which converts fatty acid methyl esters (FAME) to fatty alcohols:

hydrogenolysis-vap-in-context1

In addition, the Davy butanediol (BDO) process employs hydrogenolysis to convert dimethyl maleate or dimethyl succinate to BDO and gamma-butyrolactone (GBL) products:

hydrogenolysis-vap-in-context2

Also, our n-methyl-2-pyrrolidone (NMP) process employs the route to GBL shown above.

In the examples above, an esterification step precedes hydrogenolysis to convert an acidic feed to a non-acidic ester.

An ester feed greatly simplifies the process, as Davy ester hydrogenolysis can proceed in the vapour phase over a fixed catalyst bed. This is in contrast to acid hydrogenolysis, which usually requires a more complex, slurry-based procedure.

Hydrogenolysis also drives our propylene glycol flowsheet, where a fast dehydration reaction converts glycerol feed to a carbonyl, before reaction with hydrogen completes the process.

The overall reaction proceeds as shown:

Hydrogenolysis Flowsheet

Roll over the numbers on the flowsheet to see more information

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Process Description

JM Davy’s hydrogenolysis technology centres on a vapour-phase reaction between hydrogen gas (H2) and a carbonyl compound in the presence of a heterogeneous catalyst.

As the hydrogen gas passes through a loop, it vaporises the liquid feed then reacts with it to produce crude product in a simple, continuous process.

Liquid reactant enters the top of the vaporiser. A hot H2-rich gas stream simultaneously enters the vessel’s base. As this H2 gas rises it vaporises the liquid reactant descending through the vessel.

The resulting H2 gas and reactant vapour overheads then proceed to the hydrogenolysis reactor, in which they flow co-currently as they react to form product vapour.

The hydrogenolysis reaction proceeds in the presence of a fixed catalyst bed. As the solid catalyst is fixed in the reaction vessel, there is no need for catalyst separation prior to further downstream processing.

The hydrogenolysis product is cooled and condenses out of the H2 gas cycle as a crude liquid product.

The H2 gas recirculates via a recycle circulator, with make-up H2 added to replace that consumed in the hydrogenolysis reaction.

This recycle gas then reheats in a heater, before feeding into the bottom of the hydrogenolysis vaporiser.

The JM Davy Advantage

JM Davy’s vapour-phase technology offers many advantages over traditional hydrogenolysis processes:

+Low operating pressures:

  • Using a large excess of H2 gas gives it a high partial pressure, which eliminates the need for a high overall operating pressure to drive the reaction.
  • H2 gas in a vapour-phase reactant requires only low pressures compared with using a liquid reactant.

+ Excess H2 - temperature uniformity:

  • The large excess of H2 gas easily absorbs the heat from the exothermic hydrogenolysis reaction.
  • This promotes temperature uniformity by eliminating hotspots, maintaining the mixture at the ideal reaction temperature and so optimising conversion.

+Ideal mixing - high conversion and low residence times:

  • Vapour-phase operation ensures the organic reactants blend well with the abundant H2 and achieve ideal catalyst contact.
  • This in turn delivers high conversion rates and temperature uniformity with minimal residence times, generating high throughput.

+ High process selectivity - high quality product:

  • The mild operating conditions of this Davy technology, along with the uniform temperature profile and short residence time of the reactants and products, deliver a very selective process that results in minimal by-product formation and a very clean, high-quality product.

+No catalyst separation required:

  • As the hydrogenation proceeds in the gas/vapour phase, the solid catalyst does not mix with any reactants or products, eliminating any need for component separation prior to further downstream processing.

+Low material and equipment costs:

  • Mild operating conditions and non-acidic feedstock allows construction of the hydrogenolysis system from carbon steel.
  • Operating at low pressure also reduces pipe and vessel wall thickness, further reducing equipment cost. Lighter equipment also reduces the installation, piling, structural and civil costs of the plant.

+Plant safety and operability:

  • The use of low-pressure hydrogenolysis and the simplicity of the fixed-bed vapour phase loop significantly improve plant safety.
  • The hydrogenolysis system can be started up and shut down very quickly without any consequences to the catalyst.

+Process efficiency:

  • The high efficiency of the process means that very little by-product is produced and these small amounts can be used as boiler fuel.
  • The low operating pressure of the hydrogenolysis system also reduces the potential for fugitive emissions.
Related Processes & Core Technologies

Our hydrogenolysis technology underpins a number of the processes we license to industry. Find out more here:

JM Davy also offers technologies for hydrogenation, a chemical reaction closely related to hydrogenolysis:


Related Processes

Core Technologies

JM Davy also offers technologies for hydrogenation, a chemical reaction closely related to hydrogenolysis: