Removing and cleaning dehydrogenation catalysts

A method to remove from one or more vessels and associated piping a catalyst selected from the group consisting of:

• i) catalysts comprising
• Mo0.9-1.1V0.1-1Nb0.1-0.2Te0.01-0.17X0-2Od
• wherein:
• X is selected from Pd, Sb, Ba, Al, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Ni, Cr, Zr, Pt, and Ca,
• and d is a number to satisfy the valence of the catalyst;
• and
• ii) catalysts of the formula
• MoaVbNbcTeeOd
• wherein:
• a is from 0.75 to 1.25;
• b is from 0.1 to 0.5;
• c is from 0 to 0.5;
• e is from 0 to 0.35;
• and
• d is a number to satisfy the valence state of the catalyst
• wherein the catalyst is supported on an alumina support;
• the method comprising contacting the catalyst with from 10 to 100 ml of a not less than 0.5 molar solution of oxalic acid per 1 to 5 g of catalyst at a temperature from 20° C. to 100° C. for a period of time of not less than 1 hour, wherein contacting the catalyst dissolves the catalyst in the solution of oxalic acid.