Syngas purification by modified solvents with nanoparticles

The as-produced synthesis gas (syngas) in raw form contains compounds or a proportion of compounds that must be purified or regulated before entering as feed gas to downstream processing such as methanol, ammonia, or pure hydrogen production. The composition of the syngas can widely vary depending on gasification feed such as biomass or natural gas or municipal wastes. The gas-phase composition mainly consists of H2 (4%–50%), CO (1%–50%), CO2 (15%–56%), CH4 (6%–18%), H2S (< 40 ppm), and N2 (45%–66%). This composition of the syngas must be refined in a way before entering the downstream production unit to have an appropriate profile, e.g., H2/CO = 2.1–2.25, CO2 = 2–10 vol%, H2S = 1.6 ppmv-2%. Different catalytic and noncatalytic methods such as absorption/adsorption for this treatment can be considered. In this chapter, gas purification is mainly viewed from the absorption angle in the solvent to absorb CO2. A variety of solvents and fluids have been developed or are being developed for this purpose. However, a variety of ionic liquids (ILs) and deep eutectic solvents (DESs) have attracted a lot of attention due to their special characteristics such as high stability and low vapor pressure and have a high ability to absorb various gases such as CO2, SO2, H2S, and can even be selectively adjusted and designed to absorb the specific molecule. In all types of fluids, nanomaterials can increase the ability of the base fluid to absorb gas up to more than 90% by increasing the capability of mass transfer into the fluid with different mechanisms (grazing effect or Brownian motion). Advances in nanotechnology in the last two decades and the use of nanofluids as a new and suitable environment for heat and mass transfer have created a new horizon for improving the transfer of mass and heat. And, if the use of nanofluid is applied, one of the most important problems of industries in the field of mass and heat transfer would be resolved.