Syngas

Conversion of biomass to syngas is typically low-yield. The University of Minnesota developed a metal catalyst that reduces the biomass reaction time by up to a factor of 100.[8] The catalyst can be operated at atmospheric pressure and reduces char. The entire process is autothermic and therefore heating is not required. Another process has been developed at DTU Energy which is efficient and does not have any issues of fouling of the catalyst (in this case a cerium oxide catalyst)[9][10]

A two-stage method developed in 2012 produces syngas consisting only of carbon monoxide and hydrogen. In a first step, methane is decomposed at a temperature of more than 1000 °C, thus forming a mixture of carbon and hydrogen[11] (reaction: CH₄ + energy -> C + 2 H₂). Preferably, a plasma heater provides heating in the first step. In a second step, CO₂ is added to the hot mixture of carbon and hydrogen[12] (reaction: C + CO₂ -> 2 CO). The carbon and the CO₂ react at high temperature to form carbon monoxide (reaction: C + CO₂ -> 2 CO). The mixture of carbon monoxide from the second step and hydrogen from the first step thus forms a high-purity syngas consisting only of CO and H₂.

Alternatively, water can be used instead of CO₂ in the second step to achieve a higher amount of hydrogen in the syngas.[13] In this case, the reaction of the second step is: C + H₂O -> CO + H₂. Both methods also allow to vary the ratio of CO to H₂.

CO₂ can be split into CO and then combined with hydrogen to form syngas . A method for production of carbon monoxide from carbon dioxide by treating it with microwave radiation is being examined by the solar fuels-project of the Dutch Institute For Fundamental Energy Research. This technique was alleged to have been used during the Cold war in Russian nuclear submarines to allow them to get rid of CO₂ gas without leaving a bubble trail.[14] Publicly available journals published during the Cold War indicate that American submarines used conventional chemical scrubbers to remove CO₂.[15] Documents released after the sinking of the Kursk, a Cold War era Oscar-class submarine, indicate that potassium superoxide scrubbers were used to remove carbon dioxide on that vessel.

Heat generated by concentrated solar power may be used to drive thermochemical reactions to split carbon dioxide to carbon monoxide or to make hydrogen.[16] Natural gas may be used as a feedstock in a facility that integrates concentrated solar power with a power plant fueled by natural gas augmented by syngas while the sun is shining.[17][18][19]

By employing co-electrolysis, i.e. the combined electrochemical conversion of steam (H
2O) and carbon dioxide (CO
2) to carbon monoxide (CO) with the use of renewably generated electricity, syngas can be produced in the framework of a CO
2-valorization scenario, allowing for a closed carbon cycle.[20]

Electricity generated from renewable sources is also used to process carbon dioxide and water into syngas through the high-temperature electrolysis. This is an attempt to maintain carbon neutral in the generation process. Audi, in partnership with company named Sunfire, opened a pilot plant in November 2014 to generate e-diesel using this process.[27]

Coal gasification processes to create syngas were used for many years to manufacture illuminating gas (coal gas) for gas lighting, cooking and to some extent, heating, before electric lighting and the natural gas infrastructure became widely available. The syngas produced in waste-to-energy gasification facilities can be used to generate electricity.

Syngas that is not methanized typically has a lower heating value of 120 BTU/scf .[28] Untreated syngas can be run in hybrid turbines that allow for greater efficiency because of their lower operating temperatures, and extended part lifetime.[28]

Syngas is used to directly reduce iron ore to sponge iron.[29]

Syngas can be used in the Fischer–Tropsch process to produce diesel, or converted into e.g. methane, methanol, and dimethyl ether in catalytic processes.

If the syngas is post-treated by cryogenic processing, it should be taken into account that this technology has great difficulty in recovering pure carbon monoxide if relatively large volumes of nitrogen are present due to carbon monoxide and nitrogen having very similar boiling points which are –191.5 °C and –195.79 °C respectively. Certain process technology selectively removes carbon monoxide by complexation/decomplexation of carbon monoxide with cuprous aluminum chloride (CuAlCl
₄) dissolved in an organic liquid such as toluene. The purified carbon monoxide can have a purity greater than 99%, which makes it a good feedstock for the chemical industry. The reject gas from the system can contain carbon dioxide, nitrogen, methane, ethane, and hydrogen. The reject gas can be further processed on a pressure swing adsorption system to remove hydrogen, and the hydrogen and carbon monoxide can be recombined in the proper ratio for catalytic methanol production, Fischer-Tropsch diesel, etc. Cryogenic purification, being very energy-intensive, is not well suited to simply making fuel, because of the greatly reduced net energy gain.

Syngas is used to produce methanol as in the following reaction.

${\displaystyle {\ce {CO_2 + 3 H2 ->CH3OH + H2O}}}$

Syngas is used to produce hydrogen for the Haber process.

In an Australia, Logan City Council will use the gasification process to dramatically shrink the volume of waste needing to be trucked off site and produce syngas to power the facility. Once wastewater is treated to kill off harmful pathogens and bacteria, the remaining biosolids will be heated to high temperatures to produce a synthetic gas made up of mostly hydrogen, carbon monoxide, methane and carbon dioxide.[30]