Sulfuric acid baking and leaching of spent sulfuric acid catalyst

Abdulrahman Wahoud,Mohamedalkhaled Abdulbake,Adel Alouche

doi:10.3311/pp.ch.2011-1.06

Abdulrahman Wahoud, Mohamedalkhaled Abdulbake + Show 1 more

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https://doi.org/10.3311/pp.ch.2011-1.06

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Abstract

Vanadium, iron and aluminum were recovered from the spent sulfuric acid catalyst with efficiency of 98%, 95% and 85%, respectively by using low temperature sulphuric acid baking followed by leaching. The optimum baking conditions were four grams of concentrated sulfuric acid per ten grams of spent catalyst at 300 ^\circ C for two hours. Sulphuric acid baking followed by leaching was found to be the best and it is more effective in Iron and Aluminum dissolution. Sulfuric acid baking is expected to consume small amount of chemicals and generate much less waste effluents during the separation process of metals with alkali solutions. It is economically favorable, as it avoids us much more environmental contamination.

Highlights

Catalytic processes have many industrial uses [1, 2], which is increasing every day
3.2 Sulphuric acid leaching The leaching of spent catalyst with sulphuric acid can be represented by the following equations: V2O5 + H2SO4 → (VO2)2SO4 + H2O Fe2O3 + 3H2SO4 → Fe2(SO4)3 + 3H2O Al2O3 + 3H2SO4 → Al2(SO4)3 + 3H2O According to these equations and to the chemical composition of this spent catalyst mentioned above, less than 0.25 grams of concentrated sulphuric acid is enough for reacting with all the three metals contained by one gram of spent catalyst
The results show that the acid concentration of about 2.5 M is enough to dissolve about 90% of vanadium, while iron and aluminum dissolution seems to be only 60% and 50%, respectively

Summary

Introduction

Catalytic processes have many industrial uses [1, 2], which is increasing every day. The catalysts deactivate with time and when the activity of the catalyst declines below the acceptable level, it is usually regenerated and reused [3, 4], but regeneration is not always possible [5, 6], and after a few cycles of regeneration and reuse, the catalyst activity may decrease to very low level and further regeneration may not be economically feasible. Most of these catalysts contain valuable metals (V, Ni, Mo, Co, etc.) in the form of oxides or sulfides supported on carriers such as alumina, silica, etc. Recovery of these metals, many of which in turn consumed in carbon and stainless steel- making as an alloying agent to produce ferro-alloys and other valuable products, is an attractive option [11–13]. Recovery of vanadium pentoxide from spent sulfuric acid catalysts was reported [20] using a three–step process consisting of acid leaching, oxidation and precipitation. In many other instances, leaching with strong mineral acids or alkaline reagents was found to be ineffective in completely dissolving the catalyst.

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