Technologies for Hydrogen, Carbon Monoxide, and Syngas

SMR (Steam Methane Reformer)

ATR (AutoThermal Reactor)

POX (Partial Oxidation)



Steam Methane Reformer (SMR)

SMR is one of the predominant technologies for producing raw syngas (a gas mixture of hydrogen and carbon monoxide). Where only pure H2 is required as product, a water gas shift step is employed using steam as reactant to convert most of the CO in raw syngas to CO2 and additional H2.

hyrdogen plant

Then pure H2 is recovered as product using a H2 PSA unit. In SMR, superheated steam is combined with feedstock (natural gas, vaporized LPG, vaporized naphtha, biogas, refinery off-gas) in presence of a catalyst to produce hydrogen and carbon monoxide (raw syngas).

The reaction takes place at roughly 200 to 300 psig (15 to 20 barg). The reaction process parameters such as steam to carbon ratio in feed, reactor pressure and exit temperature are manipulated to achieve the desired ratio of hydrogen to carbon monoxide in the reactor effluent raw syngas stream.

SMR technology is by far the most commonly used technology for H2 production. It is a catalytic reactor, that produces syngas, but with high R value due to excess steam injection requirements. SMR can accept only vapor feeds so either gas or light liquid hydrocarbons that can be easily vaporized are used.

SMR is good fit where only H2 product is required however, it can also be used with CO2 recycle / imported CO2 injection for low R value syngas generation. One advantage of this technology is it is well proven, simple, and does not require O2 like the ATR and POX routes.

Steam Methane Reforming Reaction 
CH4 + H2O (+heat) → CO + 3H2

Pressure swing adsorption (PSA) with molecular sieves can be used for recovering pure H2 as product.

MATHESON SMR plants can be from small scale (0.1 mmscfd) to large scale (over 100 mmscfd) production facilities.

syngas production technologies



Autothermal Reactor (ATR) 

ATR technology is also catalytic but requires less steam than SMR and as a result produces lower R value syngas. It also requires vapor hydrocarbon feeds.

It operates at higher than SMR temperature, yielding raw syngas that is useful for several syngas or CO product applications. ATR being a catalytic reactor promotes conversions selectively to H2 and CO, at lower than non-catalytic reactors such as gasifiers.

Autothermal reforming (ATR) uses oxygen, steam, and in some cases carbon dioxide, in a reaction with light hydrocarbons such as methane to form raw syngas.

A key difference between SMR and ATR is that SMR does not use oxygen. ATR combines non-catalytic partial oxidation and catalytic steam and CO2 reforming of light and highly de-sulfurized NG in a single reactor.

ATR uses a lower steam to carbon ratio in the reformer feed as compared to SMR. Such lower S/C ratios lead to lower H2/CO ratios in raw syngas exiting the ATR. Addition of CO2 in the feed further reduces the H2/CO ratio.

ATR Reaction, using CO2: 
2CH4 + O2 + CO2 → 3H2 + 3CO + H2O

ATR Reaction, using steam: 
4CH4 + O2 + 2H2O → 10H2 + 4CO

The output ratios of these two reaction types are obviously quite different, and the user’s application will dictate which is chosen. The 1:1 ratio of the CO2 reaction can be useful, for example, in the production of DME.

ATR does not require external heat input; the heat of reaction is actually provided by internal combustion of part hydrocarbon feed with all of the O2 injected with feed.

An ATR reactor may also be used (as a secondary reformer) downstream of the primary SMR for conversion of the residual unreacted CH4 exiting the primary SMR.

The ATR technology is especially beneficial where low cost O2 is available and low H2/CO ratio syngas product, or CO product are desired.

Also, ATR is environmentally friendly as it does not have any CO2 loaded flue gas emissions (as in the case of SMR). All CO2 generated can be captured from the high pressure raw syngas stream via amine scrubbing. The captured CO2 can be recycled back to the ATR reactor;sold as raw CO2 product (and liquefied if required); or sequestered.

MATHESON ATR plants can be designed from 5 mmscfd to as large as 40 mmscfd syngas production facilities.


syngas generation




Partial Oxidation (POX)

Partial Oxidation is based on providing the heat of reaction via internal combustion of part of the feedstock with O2. The reactor can use natural gas, LPG, naphtha, asphalt, residual oil, petrol coke, or coal as feedstock. This technology is similar to ATR except:

  • POX does not use catalyst whereas ATR uses catalyst.
  • As POX is a non-catalytic reactor, it operates at higher temperatures of 1900 °F to 2300 °F as compared to ATR operating at 1650 °F to 1800 °F.
  • POX can process heavier feedstocks and liquids and solids, whereas ATR can accept only lighter hydrocarbon feeds in vapor form.
  • ATR is more selective with lower by-products formation due to catalytic reaction. As POX is non-catalytic, it requires higher temperatures to affect the reactions (thermal POX).

TPOX (thermal partial oxidation) reactions occur at temperatures of 1,900°F and above depending on how heavy the feedstock is. The high temperature heat recovery in POX is less efficient than SMR, but has an advantage over SMR because POX can use a “low value” feedstock, such that might contain sulfur or other compounds that would foul the SMR catalysts.

Non-catalytic POX Reaction: 
CH4 + ½ O2 → CO + 2H2

In ATR CPOX (catalytic partial oxidation), the use of a catalyst reduces the required temperature to roughly 1,650°F–1,800°F depending on the feedstock.

MATHESON POX plants range from 20 mmscfd to 100 mmscfd scale production facilities.



Interested in starting a dialogue about technologies for onsite production of syngas, hydrogen, or carbon monoxide?

Contact the Refining/Engineering Experts directly.


Also see:

Engineering Services Section

Onsite Gas Production Page


Refining Section
(including Chemical, Petrochemical, Energy)

Refining Gas Production Page


Air Separation Technologies