The 22-year-old midfielder has been in fine form since joining Betis in August and shone in the club's shock 4-3 victory over Barcelona on Sunday.
Lo Celso scored in the 71st minute at Camp Nou to put Betis 3-1 up and put in an eye-catching performance in a game that saw Lionel Messi score twice for the hosts on his return from injury.
Lopez Catalan said the club would endeavour to keep Lo Celso when his loan expires in June, and explained that Betis have a compulsory clause to purchase the player should they qualify for European competition as well as first refusal if they do not.
"It is very clear that Lo Celso is going to stay at Betis," Lopez Catalan told Radio Marca.
"We are convinced. We were convinced throughout the summer."
Lopez Catalan was in talks with Barcelona over the potential signing of Rafinha before the season started but he claimed that Lo Celso was always the preferred option.
"He was our option number one and is proving that he is the player we believed," said the Betis chief.
"There is a mandatory purchase option for €25 million if we enter Europe. And if not, it is optional for us and mandatory for PSG, if we carry it out."