Reaction between phosphorus pentachloride and sulfuric acid?
First phosphorus pentachloride reacts with sulfuric acid to form the intermediate(thanks @bon) chlorosulfonic acid. See here. Also Wikipedia

$$\ce{H2SO4 + PCl5 → POCl3 + HSO3Cl + HCl~~~~~~~~~~~~~~~~~~(1)}$$

Chlorosulfonic acid is actually an intermediate between  sulfuryl chloride  and sulfuric acid. After the formation of the intermediate, the reaction will proceed forward to form stable sulfuryl chloride. (Here)

$$\ce{HSO3Cl + PCl5 → POCl3 + SO2Cl2 + HCl~~~~~~~~~~~~~~~~~~~(2)}$$

Adding (1) and (2), we get the final reaction:

$$\ce{H2SO4 + 2PCl5 -&gt;2POCl3 + SO2Cl2 + 2HCl}$$

My reaction is same as that of Vishnu JK's reaction and bon.