GB436877A - Improvements in or relating to the saccharification of cellulosic materials - Google Patents

Abstract

In the saccharification of cellulosic material by means of sulphuric acid, the acid is recovered in the form of ferric sulphate or other sulphate which evolves sulphur trioxide when heated by adding ferric oxide or other suitable oxide to the liquor. Cupric oxide may, for example, be used instead of ferric oxide, and mixtures of ferric and cupric oxides can be employed. The method is especially applicable in processes in which the cellulosic material is first dissolved in strong sulphuric acid and the solution obtained diluted, for example, to a concentration of more than two per cent, and heated to saccharify the intermediate product formed; but it may also be applied in single stage processes in which the material is dissolved in dilute acid, for example, of less than two per cent concentration. The residue formed by heating the ferric sulphate to form sulphur trioxide may be hydrated with steam to facilitate solution in further acid liquor. The sulphur trioxide is absorbed, for example, in diluted sulphuric acid, to form concentrated acid for the treatment of fresh cellulosic material. The heating of the ferric sulphate need not be continued until all the sulphur trioxide is driven off, for example, the sulphate may be fed down an externally heated flue and withdrawn from a hearth at the base at such a rate that the desired proportion of sulphur trioxide is given off. An example is included.