Guard bed system and process

1. A process for operating a guard bed system in a reaction system for the production of ethylene carbonate and/or ethylene glycol said reaction system comprising a guard bed system positioned upstream of a catalytic EO reactor, said guard bed system comprising a feed line supplying a gaseous feed to be treated and an effluent line configured to remove the treated gaseous feed and two or more guard bed vessels arranged in series in sequential order, each guard bed vessel comprising an inlet, a bed of guard bed material and an outlet, wherein the inlet of each guard bed vessel is attached by means of valves to both the feed line and the outlet of the guard bed vessel preceding it in sequential order and wherein the outlet of each guard bed vessel is attached by means of valves to both the effluent line and to the inlet of the guard bed vessel following it in sequential order and wherein the guard bed vessel following the last guard bed vessel in sequential order is the first guard bed vessel in sequential order, said process comprising the steps of:

(i) supplying a gaseous feed via a feed line;

(ii) feeding said gaseous feed through two or more guard bed vessels arranged in series, wherein each guard bed vessel comprises a bed of guard bed material capable of removing impurities from the gaseous feed;

(iii) contacting the gaseous feed with the guard bed material in each of the two or more guard bed vessels thereby removing impurities from the gaseous feed;

(iv) removing a treated gaseous feed from the final guard bed vessel in series;

(v) after a period of time, removing the first guard bed vessel from the flow of the gaseous feed and allowing the gaseous feed to continue to flow through the second and any subsequent guard bed vessels;

(vi) refreshing the guard bed material present in the first guard bed vessel; and

(vii) restoring flow of the gaseous feed through the first guard bed vessel such that it is the last guard bed vessel in series to be contacted with the gaseous feed

wherein the guard bed material contained within the second guard bed system arranged in series comprises palladium and gold, preferably supported on silica.

2. The process according to claim 1 , wherein two or more guard bed systems operated by this process are arranged in series and the treated gaseous feed stream removed from the final guard bed vessel in series of the first guard bed system is supplied as the gaseous feed via a feed line to the second guard bed system.

3. The process according to claim 2 , wherein the guard bed material contained within the first guard bed system arranged in series comprises silver on alumina.

4. The process of claim 1 wherein the reaction system further comprises an ethylene oxide absorber wherein the gas composition from the catalytic EO reactor is contacted with a lean absorbent in the presence of one or more catalysts that promote carboxylation and hydrolysis to produce a gas stream, at least a portion of which gas stream is passed to the guard bed system of claim 1 .

5. The process according to claim 1 , wherein each bed of guard bed material is a radial fixed bed.

6. The process according to claim 1 , wherein the guard bed system is also upstream of a carbon dioxide absorber, which is upstream of the catalytic EO reactor.

7. The process according to claim 3 , wherein the guard bed material contained within the first guard bed system arranged in series comprises silver on alumina and said guard bed system comprises more than two guard bed vessels arranged in series.