Improvements relating to the formation of silica-alumina slurries adapted for conversion into gel-type catalysts

摘要

A silica alumina slurry suitable for conversion into a gel type catalyst is formed by reacting a mineral acid and an alkali metal aluminate in the presence of hydrated silica gel in aqueous suspension whereby aluminium hydroxide is precipitated on the hydrated silica gel. In an example, nine tons (1420 gallons) of 50 per cent sodium hydroxide solution were measured out and heated to approximately 100-105 DEG C. and 8.2 tons of bauxite ore concentrate were added thereto; the temperature being brought rapidly to 110-112 DEG C. and then more slowly to 117 DEG C. Water was then added to dilute the solution to 2860 gallons. The sodium aluminate thus formed contained approximately 28.5 per cent by weight alumina and 19.5 per cent by weight of sodium oxide. This solution was stored at at least 75 DEG C. while 1900 lbs. of hydrated silica gel at a pH of 6.4-7.6 were run into a coating tank and 26 gallons of 25 per cent sulphuric acid solution added thereto, thus reducing the pH to approximately 3. Eighty gallons of the sodium aluminate solution were withdrawn from storage, diluted with 51 gallons of water and the diluted solution run into the hydrated silica gel simultaneously with 140 gallons of 25 per cent. sulphuric acid solution thus raising the pH of the silica gel to 4.0-5.5. Aluminium trihydrate was precipitated onto the silica gel. Approximately 10 gallons of sulphuric acid were then added to bring the pH to approximately 4.7. Following ageing for 30 minutes, the slurry was washed and filtered; drying and calcining the slurry leads to a silica-alumina gel catalyst which is suitable for use as a cracking or dehydration catalyst. Specification 626,455 is referred to.