Desorption of Mercaptans and Water from a Silica–Alumina Gel

Abstract

An industrially widely used technology for the removal of condensable components like water and mercaptans from natural gas is cyclic temperature swing adsorption. Optimized design of these coupled adsorption−desorption processes requires detailed knowledge of desorption properties of the used adsorbents. Therefore, the desorption behavior of water, methyl mercaptan, and ethyl mercaptan was investigated on a commercial silica−alumina gel. In dynamic experiments, a preloaded fixed bed was regenerated with hot purge gas (300 °C), and time-dependent concentration and temperature profiles were measured and discussed by means of equilibrium theory. Characteristic plateau temperatures were found between 43 and 63 °C, rising with the adsorption affinity. Experiments with competitive adsorption of water and mercaptans show that process dynamics are mainly controlled by water. The results are evaluated with regard to technical relevance.

Adsorptive Water Removal from Dichloromethane and Vapor-Phase Regeneration of a Molecular Sieve 3A Packed Bed

“…The concentration plateau is lost for high mass flows, in which case the transfer zones overlap. 15 , 39 The second (latter) mass-transfer front forms a tail as the concentration difference between the solid phase and the fluid phase decreases with time.…”

Temperature Swing Adsorption in Natural Gas Processing: A Concise Overview

“…The formation of COS is also observed when 5A zeolites or other molecular sieves are used to dehydrate natural gases. If dew point requirements are not very strict (e.g., pipeline transport), silica or silica‐alumina gels which have been reported to produce no significant amounts of COS , are often used for dehydration and separation of heavy hydrocarbons. Cines et al.…”

“…al show that the characteristic temperature plateaus during desorption of mercaptans in a TSA process also depend significantly on the dipole moments. However, in multi‐component systems, desorption dynamics are dominated by water, which is even more polar .…”

“…al proved that silica and silica‐alumina gels show no significant conversion of H 2 S and CO 2 to COS even under extreme test conditions due to the lack of catalytic sites. The authors point out that that no COS formation is assumed to occur in industrial processes when silica gels are used for drying or dew point adjustment .…”

Adsorptive Separation of CO2 from Flue Gas by Temperature Swing Adsorption Processes

“…Typical applications of TSA are the removal of trace components from a process gas, e.g., in natural gas treatment , . In this process the adsorbate that has to be removed, bounds strongly on the adsorbent.…”