By far the easiest way to get from Indianapolis International Airport to Purdue. Travel time is ca. 1.5 hrs.
Lafayette Limo: https://www.lafayettelimo.com/
One way tickets are $27 ($50 round trip). Regular service every two hours between 6:30 a.m. and 10:30 p.m. Book online or during check-in at the Lafayette Limo booth in the Ground Transportation Center, across from Avis Rental Car. Bus leaves from Zone 5 of the Ground Transportation Center.
Reindeer Shuttle: https://www.reindeershuttle.com/
One way tickets are $30 ($27 for students) if booked at least 24 hrs in advance, $35 for walk ups, plus a fuel surcharge (currently $3). Seating is only guaranteed with advance reservation.
Shuttle Bus pickup is outside the Ground Transportation Center at loading Zone #5. The Ground Transportation Center is located across the street from Baggage Claim 4.
A convenient drop off location at Purdue is the Purdue Memorial Union (PMU) or the Union Club Hotel, within walking distance of Wetherill Hall of Chemistry.