Lopez struck with a header just after halftime at the Gran Parque Central Stadium here on Thursday to hand the three-time champions their second win of the campaign, reports Xinhua.
The result left Palmeiras third in Group 2 with four points.
Meanwhile, Argentina's Racing Club recovered from two goals down to draw 2-2 at Deportivo Cali, also on Thursday.
Andres Roa and Fabian Sambueza struck first-half goals for the Colombian outfit before Leandro Grimi and Lisandro Lopez drew the visitors level after the interval.
In other matches on Thursday, Argentina's Rosario Central beat Uruguay's River Plate 3-1 and Paraguay's Olympia overcame Emelec of Ecuador 4-2.