A catalyst comprising chromia and at least one additional metal or compound thereof and wherein the catalyst has a total pore volume of greater than 0.3 cm3/g and the mean pore diameter is greater than or equal to 90 Å, wherein the total pore volume is measured by N2 adsorption porosimetry and the mean pore diameter is measured by N2 BET adsorption porosimetry, and wherein the at least one additional metal is selected from Li, Na, K, Ca, Mg, Cs, Sc, Al, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, In, Pt, Cu, Ag, Au, Zn, La, Ce and mixtures thereof.