Room-temperature ionic liquids (ILs) have been demonstrated to absorb SO(2) efficiently. However, after absorbing a large amount of SO(2), the viscosity, the conductivity, and the density of the ILs have not been studied systematically, and the mechanism of the interaction between SO(2) and ILs is still being disputed. In this work, two kinds of ILs (task-specific ILs and normal ILs) have been studied to absorb pure SO(2) at atmospheric pressure. It is found that the viscosity, the conductivity, and the density show different behaviors between task-specific ILs and normal ILs. For the task-specific ILs to absorb SO(2), before a 0.5 mol ratio of SO(2) to IL, the viscosity and density increase, and the conductivity decreases with an increase of the mole ratio of SO(2) to IL. After that, the conductivity and density increase, and the viscosity decreases with further increasing the mole ratio of SO(2) to IL. However, for the normal ILs, the conductivity and density increase and the viscosity decreases with an increase of the mole ratio of SO(2) to IL. A new mechanism of ILs absorbing SO(2) has been proposed. Task-specific ILs can chemically absorb SO(2) when the mole ratio of SO(2) to IL is not more than 0.5, and they can physically absorb SO(2) when the mole ratio is more than 0.5. The normal ILs can only physically absorb SO(2).

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Here we report a catalytic process for the efficient production of formic acid (FA) from common carbohydrates via VO 2 + formed by dissolving sodium metavanadate in acidic water. The polysaccharides undergo a hydrolysis reaction and an immediate oxidation reaction successively to produce FA in the same reaction system. The hydrolysis reaction decomposes the polymerized structures to produce monosaccharides, which are readily oxidized to FA under catalysis of VO 2 + . Typically, formic acid mole yields are 64.9% from cellulose and 63.5% from xylan (hemicellulose). The separation of FA from the catalytic system and recycling of the catalyst are demonstrated. † Electronic supplementary information (ESI) available: Spectroscopic data and further details. See