HOW DO JOHNSON MATTHEY PURIFIERS WORK?
Palladium
Palladium membrane hydrogen purifiers operate via pressure driven diffusion across palladium membranes.  Only hydrogen can diffuse through the palladium.  The palladium membrane is typically a metallic tube comprising a palladium and silver alloy material possessing the unique property of allowing only monatomic hydrogen to pass through its crystal lattice when it is heated above nominally 300°C. The hydrogen gas molecule coming into contact with the palladium membrane surface dissociates into monatomic hydrogen and passes through the membrane. On the other surface of the palladium membrane, the monatomic hydrogen is recombined into molecular hydrogen - the ultrapure hydrogen used in the semiconductor process.

Palladium purifiers can provide <1 ppb impurity removal purity with any inlet gas quality including O2, H2O, CO, CO2, N2 and THCs.   Palladium purifiers require heating and control systems, available from JM or provided by the customer.

Getter
Getter gas purifiers use two processes to remove impurities, adsorption and bulk diffusion. Impurities adsorb onto the surface of the getter material in the first step.  The heated getter then allows the impurities to diffuse into the bulk of the getter material, binding it to the material.  The reaction is irreversible, so the impurities cannot be released back into the gas stream.  Getter purifiers remove O2, H2O, CO, CO2, N2 and THC. The getter is consumed during use, but the bulk diffusion provides very high capacities leading to long lifetimes.

Ambient Catalytic
Catalytic purifiers operate via chemical and physical adsorption.  Impurities react on the surface of the high surface area media and are held via chemisorption or physisorption.  The reactions are reversible, so the purifier can be regenerated to purge impurities and allow the purifier to be used repeatedly.  Impurities removed include O2, H2O, CO, CO2 and non-methane hydrocarbons (NMHC). Capacity for CO2 and NMHC is relatively small, so these purifiers are most often used when O2 and H2O are the key impurities to be removed. These purifiers require no heating or control system for POU applications.
 

HOW DO I DETERMINE WHICH TECHNOLOGY (Palladium, getter or catalytic) IS BEST FOR MY APPLICATION?
The choice of the best technology will be determined by the gas (ie, palladium is only for hydrogen), flow rate, inlet purity, duty cycle and outlet purity specification. Johnson Matthey will work with you to help select the best purifier for every application. 

WHAT CAN ACT TO POISON A PALLADIUM MEMBRANE,/GETTER, OR/CATALYTIC GAS PURIFIER?
Large amounts of metals, sulfur, oils and non-methane hydrocarbons can poison any type of purifier.
 

AT WHAT PRESSURES AND TEMPERATURES DO THESE PURIFIERS RUN?
Palladium membrane purifiers – maximum operating pressure is 250 psig at 300 to 400 degrees Celsius (high pressure vessels available)

Getter purifiers – maximum operating pressure is 250 psig at room temperature/450 degrees Celsius (high pressure vessels available)

Catalytic purifiers – maximum operating pressure is 250 psig at room temperature
 

WHAT IS THE LIFETIME OF THE PURIFIERS?
Normal life expectancy of the palladium membrane in hydrogen purifiers is 5 years.

 Getter beds, operating at the nominal flow rate with inlet gas quality of 99.999%, have a normal life expectancy of two years.

Catalytic beds, provided they are properly maintained and regenerated, can have unlimited life.
 

WHAT ROUTINE MAINTENANCE DO THESE PURIFIERS REQUIRE?
There is no routine maintenance required for a palladium membrane hydrogen purifier.  For the catalytic purifiers, periodic regeneration is necessary.  The frequency of regeneration is determined by the impurity levels in the feed gas stream.
 

WHAT DO YOU DO IF YOU SUSPECT PRODUCT FAILURE?
If a problem is suspected with the palladium membrane hydrogen purifier, a helium leak check should be performed. If the membrane is confirmed to be leaking please contact Johnson Matthey.  Should impurity breakthrough of an ambient getter or catalytic POU purifier be suspected the bed can be regenerated. Should impurity breakthrough of a heated getter purifier occur, contact Johnson Matthey about replacement of the vessel.
 

WHAT IS THE NORMAL FAILURE MODE?
A leak across the palladium alloy membrane can develop in the palladium membrane in a hydrogen purifier. A process upset can cause a getter or catalytic purifier to fail.
 

WHAT HAPPENS IF THE POWER IN THE FAB/PLANT FAILS?
A hydrogen purifier purge system is recommended to automatically purge the hydrogen out of the palladium membrane system before the system cools down.  Failure to evacuate or purge hydrogen from the palladium membrane purifier will affect the operating life of the purifier.  If running hot, getter gas purifiers must be isolated in the event of a power failure.  Power failures do not affect ambient getter or catalytic purifiers.
 

WHAT HAPPENS IF THE PALLADIUM MEMBRANE COOLS IN HYDROGEN?
Cooling in hydrogen leads to entrainment of the hydrogen in the palladium alloy lattice thereby causing stresses within the membrane, which over time increases the possibility of membrane failure. Purging with nitrogen is recommended.
 

HOW LONG HAS JOHNSON MATTHEY BEEN IN THE HYDROGEN PURIFIER BUSINESS?
Johnson Matthey has been in the purification business for over 40 years.
 

ARE THE PURIFIERS HARD TO INSTALL?
Following the technical manual supplied, Johnson Matthey purifiers are easy to install and operate. For larger systems a commissioning service is offered.
 

WHAT IS THE PRESSURE DROP ACROSS THE PURIFIERS?
When operating within normal parameters the pressure drop across a getter or catalytic bed is less than 1 atm.  Pressure across the palladium membrane is required in order to drive the hydrogen across the palladium membrane. The larger the pressure drop the greater the flow and the smaller the palladium membrane size required, thus improving the economics. 
 

WHAT SIZES DO THE PURIFIERS COME IN?
Palladium membrane hydrogen purifiers range from 1 liter per minute to over 1,000 liters per minute. Getter and catalytic gas purifiers range from 0.1 liters per minute to over 2,000 liters per minute.
 

WHY ARE THE CONTROL PANEL AND PURIFIER SEPARATED IN THE LARGER PALLADIUM MEMBRANE HYDROGEN PURIFIERS?
In palladium membrane hydrogen purifiers separating hydrogen components from electrical components is done to make them code-compliant.
 

WHAT SPARES SHOULD I CARRY FOR THE UNIT?
For palladium membrane hydrogen purifiers a spare cell and/or spares of certain components are recommended.  Speak to your Johnson Matthey representative for more information on what components may be recommended for your unit.  Spare getter and catalytic vessels are not required but are suggested for rapid replacement.
 

WHAT IS THE DIFFERENCE BETWEEN RUNNING GETTER GAS PURIFIERS HOT VS. COLD?
Running getter gas purifiers hot will avoid the need for periodic regeneration and allow removal of nitrogen and methane from rare gases.  Operating getter gas purifiers at ambient requires no power, so it is a viable option for low-flow applications where inlet gas quality is 99.9999% or better.

For specialty gases, the getter is run at ambient temperature in all cases.
 

WHY ARE JOHNSON MATTHEY PALLADIUM PURIFIERS BETTER THAN OTHER TYPES OF HYDROGEN PURIFIERS?
Refer to the technical bulletin section of this web site for detailed information on the specific advantages of palladium purifiers.

I AM UNHAPPY WITH PURIFIERS FROM ANOTHER SUPPLIER, BUT I NEED THE SAME SIZE UNIT TO ALLOW DIRECT REPLACEMENT, CAN YOU HELP ME?
Absolutely, many of our purifiers use industry-standard dimensions to allow direct replacement.  For other applications, Johnson Matthey will work to engineer a unit, or system, to fit your needs. .