Abstract
A nickel-silica core@shell catalyst was applied for a methane tri-reforming process in a fixed-bed reactor. To determine the optimal condition of the tri-reforming process for production of syngas appropriate for methanol synthesis the effect of reaction temperature (550–750 °C), CH4:H2O molar ratio (1:0–3.0) and CH4:O2 molar ratio (1:0–0.5) in the feedstock was investigated. CH4 conversion rate and H2/CO ratio in the produced syngas were influenced by the feedstock composition. Increasing the amount of steam above the proportion of CH4:H2O 1:0.5 reduced the H2:CO molar ratio in produced syngas to ∼1.5. Increasing oxygen partial pressure improved methane conversion to 90% at 750 °C. At low ∼550 °C reaction temperature the tri-reforming process was not effective with low hydrogen production (H2 yield ∼20%) and very low <5% CO2 conversion. Increasing reaction temperature increased hydrogen yield to ∼85% at 750 °C. From all the tested reaction conditions the optimal for tri-reforming over the 11%Ni@SiO2 catalyst was: feed composition with molar ratio CH4:CO2:H2O:O2:He 1:0.5:0.5:0.1:0.4 at T = 750 °C. The results were explained in the context of characterisation of the catalysts used. The obtained results showed that the tri-reforming process can be applied for production of syngas with composition suitable for methanol synthesis.
Highlights
Methane reforming is a well established industrial process for syngas production
Increasing reaction temperature from 550 to 750 C resulted in increasing methane conversion from 24% to above 70%
For the tested catalyst, increasing the amount of oxygen in the feedstock improved methane conversion to 90% and reduced coke deposition but did not improve the H2:CO ratio in produced syngas
Summary
Methane reforming is a well established industrial process for syngas production. The goal of methane reforming is to achieve high methane conversion with the required H2:CO ratio without coke deposition. The process can sometimes be combined with CO2 conversion and utilisation. That process requires high energy input and there is a risk of coke deposition that would deactivate the catalyst [1]. In the novel process of tri-reforming, syngas production and CH4 conversion is possible without CO2 separation and with relatively low energy consumption [2]. The fact that it is not necessary to separate CO2 from methane can reduce the cost of reforming and at the same time can reduce the volume of CO2 emissions. The tri-reforming process combines the three generally used methane reforming processes into one. In the tri-reforming of methane in a single reactor, the following reactions are coupled: methane steam reforming (1), methane partial oxidation (2) and carbon dioxide reforming of methane (3): CH4þH2O/CO þ
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