DESILICATION of natural zeolite by alkali treatment to produce solketal was successfully prepared. Natural zeolite from Tasikmalaya, West Java, Indonesia, has been used as a catalyst source. The natural zeolite source was mordenite type structure. The experimental condition was varied to study their effect on the catalyst efficiency. Several characterization methods, such as Thermogravimetric Analysis (TGA), Brunauer Emmett Teller (BET), X-ray Diffraction (XRD), Scanning Electron microscopy (SEM), etc., were used to analyze the physicochemical properties of the prepared catalyst. From the temperature-programmed desorption of NH3 (TPD analysis), the acidity of zeolite decreased from 0. 597 to 0. 444 by increasing NaOH concentration from 0. 1 to 0. 7 M, respectively. The result showed that alkali treatment did not change the phase structure of natural zeolite significantly. Here, the ratio of Si/Al decreased by increasing NaOH concentration, resulting in the decrease of acidity value. Interestingly, the efficiency of zeolite catalyst (HZ-01) shows the highest conversion and selectivity at around 98. 73% and 74. 66%, respectively. This exciting result opens the possibility to develop an economic catalyst with high efficiency from the abundant Indonesian mineral resource.