Mechanism of xanthation reaction in viscose process

Xanthation reaction in viscose process is heterogeneous reaction (gaseous CS2-wet alkaline cellulose) complicated with side reactions. Commercial requirement of CS2 in viscose process is 32-34%, which is significantly higher than the stoichiometric requirement (23.5% w/w of the cellulose) due to formation of byproducts. Detailed xanthation reaction kinetics study was performed to understand the xanthate and by-products formation mechanism along with effect of mass transfer and its possible impact on CS2 consumption. Heterogeneous nature of the xanthation reaction offers significant mass transfer resistance and was hypothesized to be driven by CS2 partitioning into wet alkali cellulose and its unstable complex (DTCdithiocarbonate) formation with alkali. Xanthation reaction mechanism in the form of physico-chemical process steps has been proposed with experimental justification. [GRAPHICS] .