Licensed Processes

Vinyl Chloride Monomer (VCM)

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JM Davy have recently acquired a well-established VCM technology which is recognised by industry as the most advanced acetylene-to-VCM process worldwide.

Our VCM flow sheet combines the best of JM Davy’s process design with Johnson Matthey’s PRICATTM catalyst technology to offer major advantages over alternative processes, including:

  • Lower investment cost
  • Higher VCM quality
  • Higher raw material efficiency
  • A mercury-free process
  • Anhydrous operation

Davy VCM is the only mercury-free process currently offered for license. As such it is the only process ready for the expected complete ban on mercury catalysts for plants started up after 2016 (as per the 2013 Minamata convention between 150 countries including China).

For more information, see this article published in Chemistry World which reports on Johnson Matthey’s mercury-free catalysis of VCM production.

PRICATTM is a trade mark of Johnson Matthey Plc.

Process Flowsheet

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Key Reactions

Hydrochlorination converts acetylene feed to VCM product:


VCM big equation

Process Description

The Davy VCM flow sheet centres on our hydrochlorination technology, which employs Johnson Matthey’s innovative PRICAT MFC (mercury-free catalyst).

An advanced three-stage separation and purification system follows, delivering high-grade VCM that is suitable for downstream polymerisation to PVC without requiring any further processing or purification.

Process feedstock

Acetylene gas is compressed, then dried to ppm moisture content by chilling and adsorption.

HCl gas, pre-dried to a similar moisture level, enters the system and mixes with the dry acetylene.

Using dry reactants is crucial, as water can carry a variety of undetectable impurities such as metal ions. These ions can cause issues in the downstream PVC production process, such as reactor fouling and black spots in the final product.  Dry reactants are also crucial to preventing plant corrosion.

The dry acetylene/HCl mixture then proceeds to hydrochlorination.


Entering the hydrochlorination reactors, the process gases pass over Johnson Matthey’s PRICAT MFC catalyst and react exothermically to form crude VCM:

hydrochlorination small equation

Separation, recycle and purification

The hot reactor discharge comprises VCM, unconverted reactants and a small proportion of heavy by-products.

After cooling and compression, this crude product stream enters a light-ends stripper which removes the unreacted acetylene and HCl.

The unreacted gases then proceed to one or more specially designed recycle reactors, in which the majority converts to VCM, before re-joining the hydrochlorination discharge stream.

Meanwhile, the bottoms stream from the light-ends stripper proceeds to a fractionator to separate the heavies from the VCM product. VCM retained in the heavies is recovered in a downstream stripper, while the VCM overhead goes through a final finishing column to remove residual HCl.


Johnson Matthey’s PRICAT family of catalysts serve a range of industries for the production of olefins, oleochemicals, fats & oils, oxo alcohols, aniline capro, specialty amines, fluorochemicals and chlorochemicals.

The Davy VCM flow sheet employs a special PRICAT mercury-free catalyst (MFC) formulation, the advantages of which are outlined below:

Traditionally, VCM production from acetylene has accounted for the largest intentional use of mercury in the world.

Johnson Matthey’s PRICAT MFC has the potential to transform the acetylene-to-VCM industry by completely eliminating the use of mercury from the process.

PRICAT MFC is guaranteed non-toxic and not harmful for the environment as it does not contain any volatile components that can be released to atmosphere or contaminate ground water.

Additional advantages of PRICAT MFC include:


  • No risk of mercury poisoning to VCM plant personnel.

Longer lifetime, reduced costs

  • PRICAT MFC has a much longer lifetime than mercury catalysts.
  • In existing plants, it can also be loaded directly into both primary and secondary reactors, whereas mercury catalysts typically require shifting from one reaction stage to the next.
  • Consequently, PRICAT MFC delivers significantly reduced catalyst loading and unloading per year, saving downtime, maintenance and plant staffing costs.

Reduced equipment costs

  • Less process equipment required due to the absence of any steps for mercury capture and handling, and treatment of mercury-contaminated waste water.

High selectivity

  • PRICAT MFC’s high selectivity towards VCM ensures efficient use of the HCl and acetylene reactants.
  • The low by-product formation that results means that little separation is required to produce high-purity VCM.
  • Fewer reactors are required due to the high reaction yield delivered by PRICAT MFC.


JM Davy’s VCM process technologies have been designed to maximise the benefits of PRICAT MFC and reduce catalyst costs by the following means:

Higher VCM yield

The Davy flowsheet achieves a higher VCM yield from PRICAT MFC (kg VCM/kg catalyst) than other VCM processes using the same catalyst.

Higher VCM productivity

  • When used in the Davy VCM flow sheet, PRICAT MFC achieves a significantly higher VCM productivity (kg VCM/kg catalyst/hour).
  • This means Davy VCM can use fewer reactors and less catalyst than other VCM processes using PRICAT.
The JM Davy Advantage

Together, JM Davy’s flow sheet and Johnson Matthey’s PRICAT MFC catalyst deliver the world’s most advanced acetylene-to-VCM process.

Read below to find out more:

+High VCM quality:

  • Davy VCM quality is equivalent to, or higher, than that achieved by the ethylene-based VCM process.
  • Our flow sheet also delivers much higher quality VCM than alternative acetylene-to-VCM processes.
  • The VCM product also has low water content due to anhydrous operation.
  • PRICAT MFC is highly selective towards VCM, prevents by-product formation and increases VCM product purity.
  • The process features a well-designed VCM purification system, supported by JM Davy’s rigorous process simulation and extensive distillation design experience.

+Anhydrous operation:

  • We employ an anhydrous production process (rigorous raw material drying and no water or caustic soda scrubbing).
  • This achieves a VCM water content of <10ppm, reducing the presence of metal ion impurities which, in the downstream PVC plant, may cause reactor fouling and product quality issues.
  • This also avoids corrosion problems in the VCM process itself, which is a common weakness of alternative acetylene-to-VCM plants.

+High raw material efficiency:

  • The Davy VCM flow sheet uses a much lower HCl/acetylene ratio than employed elsewhere, which reduces consumption of HCl and caustic.
  • PRICAT MFC delivers high selectivity with little by-product formation.
  • Our VCM recycle system operates at higher pressures and concentrations than secondary VCM reactors in alternative processes, giving higher overall yield.

+PRICAT catalyst delivers a
mercury-free process:

  • Johnson Matthey’s PRICAT MFC (mercury-free catalyst) is guaranteed non-toxic and not harmful to the environment.
  • Our process is the only mercury-free VCM flow sheet offered for license anywhere in the world.
  • Davy VCM is ready for the expected complete ban on the use of mercury catalysts for new plants started up after 2016.

+Low investment cost:

  • Our flow sheet has a low equipment count. This is due to a high single-reactor capacity driven by the PRICAT MFC catalyst and our recycle reactor arrangement.
  • Anhydrous operation also reduces the amount of spare equipment required, as there is reduced risk of equipment failure from corrosion.
  • Additionally, as our VCM process is mercury-free, it requires no process equipment for mercury removal.
  • This low equipment count requires only a small plot size.
  • Most of the equipment used in the Davy VCM flow sheet is of simple design and constructed of inexpensive carbon steel. The process requires very few vendor-designed special packages.
Core Technologies

Explore the Davy hydrochlorination technology that underpins our VCM process:

Core Technologies

Explore the Davy hydrochlorination technology that underpins our VCM process: