Refining and reforming: Engineering methods

Distil, crack, reform: the steps that reshape a barrel

What this tab covers The engineering methods that can do this conversion, compared on efficiency, scale, economics, limitations and reliability.

A modern refinery chains several units; hydrogen and syngas routes differ mainly in feed and whether carbon is captured.

Comparison

Method	Efficiency	Scale	Economics	Limitations	Reliability
Atmospheric and vacuum distillation³⁶	109 and 89 thousand Btu per barrel; up to 54% and 39% savings potential	Up to 665,000 barrels per stream day at Marathon's Galveston Bay, the largest US refinery on that basis (Motiva's Port Arthur is largest per calendar day)	Front end of every refinery; energy is its main running cost	Only separates; cannot change the product mix	Runs continuously for years between planned turnarounds; fouling and corrosion are the main issues
Fluid catalytic cracking and hydrocracking²⁶	FCC 183 thousand Btu per barrel of feed	The main gasoline-making unit in US-style refineries	Turns low-value heavy oil into high-value fuels	FCC regenerator is a large CO2 source; hydrocracking needs much hydrogen	Catalyst attrition and erosion
Catalytic reforming, alkylation and hydrotreating²⁶	Reforming 264; alkylation about 245 to 250; hydrotreating 81 thousand Btu per barrel	Standard in most refineries	Needed to meet octane and sulphur specifications	Alkylation uses hazardous hydrofluoric or sulphuric acid	Catalyst life and regeneration set cycles
Steam methane reforming (grey hydrogen)⁸⁹¹⁰	75.4% HHV	Up to about 480,000 kg/day per plant in NETL's design; Dangote has two SMRs making 200,000 Nm3/h	About 1.06 USD/kg (2018 USD)	10 to 12 kg CO2-eq per kg H2 unabated; capture is harder because flue gas CO2 is dilute	Reformer tube creep and catalyst ageing; 90% capacity factor assumed
Autothermal reforming (ATR) with capture⁹	67.9% HHV with 94.5% capture	Larger single trains: 660,000 kg/day in NETL's case	1.59 USD/kg with storage (2018 USD)	Needs an oxygen plant and CO2 storage	Similar to SMR
Coal gasification and coal-to-liquids⁹¹⁰¹²¹³	About 65% HHV to hydrogen; roughly 35 to 40% energy yield to liquids (calculated)	Sasol Secunda about 150,000 to 160,000 b/d with 80 gasifiers; Ningxia 4 Mt/yr with 28 gasifiers	2.58 USD/kg hydrogen; liquids only viable with cheap coal and policy support	22 to 26 kg CO2-eq per kg H2; heavy water use	80% capacity factor assumed; gasifier refractory and burner wear

Distillation and cracking are mature and hard to improve by more than about 30% on energy. For hydrogen, SMR is cheapest and most efficient; ATR is the better route if CO2 is to be captured; coal gasification costs about 2.5 times as much and emits about twice the CO2, so it survives mainly where coal is cheap and gas is scarce, as in China and South Africa. Coal-to-liquids needs about three times the capital per barrel of an oil refinery.

How each method works

Atmospheric and vacuum distillation

Crude is heated in fired heaters and split by boiling point in tall columns; the vacuum column separates heavy residue at lower temperatures.

Fluid catalytic cracking and hydrocracking

Hot powdered zeolite catalyst cracks gas oil in seconds and is regenerated by burning off coke; hydrocracking does the job under hydrogen pressure and makes cleaner diesel and jet.

Catalytic reforming, alkylation and hydrotreating

Reforming raises naphtha octane and releases hydrogen; alkylation combines light gases into gasoline; hydrotreating removes sulphur with hydrogen.

Steam methane reforming (grey hydrogen)

Gas and steam pass through catalyst-filled tubes in a furnace, then shift reactors and PSA purification.

Autothermal reforming (ATR) with capture

Oxygen from an air separation unit burns part of the gas inside the reactor to supply the heat, so nearly all CO₂ ends up in one concentrated stream.

Coal gasification and coal-to-liquids

Coal reacts with oxygen and steam in a gasifier; the syngas is cleaned and shifted to hydrogen, or converted by Fischer-Tropsch catalysts into diesel, naphtha and LPG.

Sources

Refining crude oil: the refining process US Energy Information Administration, 2025
U.S. refining capacity largely unchanged as of January 2025 US Energy Information Administration, Today in Energy, 2025
Energy Bandwidth for Petroleum Refining Processes US Department of Energy (Energetics Inc.), 2006
Dangote Refinery, Lagos (project profile, 2021; completion dates in it are out of date) NS Energy, 2021
Comparison of Commercial, State-of-the-Art, Fossil-Based Hydrogen Production Technologies National Energy Technology Laboratory, US DOE, 2022
Global Hydrogen Review 2024: GHG emissions of hydrogen and its derivatives International Energy Agency, 2024
Gasifipedia: Sasol National Energy Technology Laboratory, US DOE, 2024
Visiting the world's biggest single coal-to-liquid project in Yinchuan, China IEA Clean Coal Centre (sustainable-carbon.org), 2017