GB939938A - Improvements in or relating to activated earths - Google Patents

Abstract

An acid-activatable raw earth in the form of granules or nodules having a moisture content of 5 to 45% by weight is stabilized and activated by contacting it with from 4 to 13 milli-equivalents acid per grame of raw earth of either HCl of at least 20% w/w concentration or H2SO4 of at least 40% w/w concentration, digesting the mixture at above 85 DEG C., then diluting the mixture so that in the liquid phase the concentration of Clof SO4- is less than 13% or less than 25% respectively, and then digesting the diluted mixture above 85 DEG C., the digestion being terminated before the SiO2:Al2O3 ratio in the earth exceeds 16:1. Preferably when HCl is used its concentration should not exceed 30% w/w. When H2SO4 is used its concentration should preferably not exceed 70% w/w. It is desirable that the initial digestion is conducted at a temperature of at least 90 DEG C. and the digestion of the diluted mixture is conducted at the boiling point of the liquid phase. The initial digestion usually ranges from 30 minutes to 5 hours. In a modification the raw earth can be treated in pelleted form, having an initial moisture content of 20 to 45% by weight. Examples of the raw earths which can be treated are montmorillonite, beidellite, illite and nontronite, and also impure clays containing these, such as those commonly known as sub-bentonites. In carrying out the process each digestion step is effected by continuously recirculating the acid through a bed of the earth granules or nodules, and the dilution step is effected by introducing water into the recirculating acid. The stabilized activated product can be employed for the adsorption of unsaturated compounds from toluene. The term "acidactivatable raw earth" means aluminous triple layer clay minerals and impure clays containing these. Specification 939,937 is referred to.