Down flow can help to keep the media in the bed, while up flow tends to remove the smallest particles. Generally down flow has a chance of higher flow rate without fluidizing the bed.

If absorption is down flow with uniform distribution, then regeneration would best be done up flow to give the most complete regeneration near the bottom.

The operation can be represented as a Log-Log function. For economical operation the saturation does not go to completion and regeneration does not go to completion.

Two parameters affect the direction of flow: the resultant lifting or fluidizing of bed and type of feed (i.e. gas or liquid).

For gases, it's better to have downwards flow where high velocities may cause fluidizing. For liquids, if you consider upwards flow then you need to have low flow rate to prevent bed lifting, however sometimes it is better to have slight bed expansion to reduce the pressure drop. More expansion can cause your bed to be well mixed. 

For better reference, you can refer to a book: adsorption technology and design.

Thank you for your answers. can i prevent bed lifting by placing something in between beds? like marbles or cotton?

Of course you may prevent bed lifting by fixed glass drip, mesh or similar. For liquid adsorption tests upward flow may also assist in removal of trapped air. Of course downward flow can be realized by hydrostatic pressure only.