Zirconia has advantageous thermal stability and acid–base properties. The acidity character of ZrO2 can be enhanced through the sulfation process forming sulfated zirconia (ZrO2-SO4). An acidity test of the catalyst produced proved that the sulfate loading succeeded in increasing the acidity of ZrO2 as confirmed by the presence of characteristic absorptions of the sulfate group from the FTIR spectra of the catalyst. The ZrO2-SO4 catalyst can be further modified with transition metals, such as Platinum (Pt), Chromium (Cr), and Nickel (Ni) to increase catalytic activity and catalyst stability. It was observed that variations in the concentrations of Pt, Cr, and Ni produced a strong influence on the catalytic activity as the acidity and porosity of the catalyst increased with their addition. The activity, selectivity, and catalytic stability tests of Pt/ZrO2-SO4, Cr/ZrO2-SO4 and Ni/ZrO2-SO4 were carried out with their application in the hydrocracking reaction to produce liquid fuel. The percentage of liquid fractions produced using these catalysts were higher than the fraction produced using pure ZrO2 and ZrO2-SO4 catalyst.

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Catalytic activity and selectivity toward liquid fuels production of ZrO2, SZ, 0.5NiSZ, 1.0NiSZ, and 1.5NiSZ catalysts with different physicochemical properties, in hydrocracking process upon the second stage of sequential LDPE plastic conversion method after pyrolysis process, were examined. The hydrocracking reaction was carried out at 300°C under 20 mL/min of hydrogen gas flow for 1 h. Modifying commercial ZrO2 with sulfate and Ni enhances the acidity of catalyst, even though there is a decrease in surface area. The increase in acidity of catalyst results in the higher liquid fuels conversion. The presence of nickel reduces olefins content and aromatic content of liquid product, and also reduces coke formation. The highest liquid yield (44.32%) that composed by 66.25% fraction of gasoline is produced over 1.5NiSZ which has the highest catalyst acidity.

The effect of sulfating agent concentration, calcination temperature, and Ni incorporation on commercial zirconia have been evaluated. Sulfation of commercial zirconia was prepared by wet impregnation with different amounts of sulfuric acid (0.2, 0.5 and 0.8 M) then calcined at 400, 500, 600, 700, 800 and 900°C for 4 h. Ni was incorporated by refluxing over sulfated zirconia, followed by calcination-reduction process. All samples were characterized by XRD, FTIR, ammonia sorption, SEM-EDX, TEM, and AAS. The presence of sulfate has been added to acidic strength of the sulfated zirconia, the more sulfuric acid were used the stronger the acidic property. There has been degradation of sulfate groups that was adrift in sulfated zirconia by calcination treatment above 600°C. The best physicochemical properties of sulfated zirconia were modification with 0.8 M sulfuric acid and on calcination at 400°C. The 0.8SZ-400 has exhibited the highest Brønsted acidic sites with total acidity of 1.71 mmol/g. The impregnation of Ni enhanced the Lewis acidic sites on the surface of the 0.8SZ-400 which NiSZ gave 2.71 mmol/g of total acidity. All prepared materials consisted of nearly spherical shape of nanocrystal with mostly aggregated particles.

In this work, nickel promoted sulfated zirconia (Ni/SZ) as catalyst was prepared by either by reflux (Ni/SZ-R) or hydrothermal Ni impregnation (Ni/SZ-H) routes. The aim of this study was to evaluate the influences of two preparative methods on the physico-chemical properties of prepared catalysts. Both the catalysts were characterized by XRD, FTIR, ammonia adsorption, SEM-EDX, TEM-SAED, AAS and BET. It was found that the presence of sulfate and nickel could enhance the Brønsted and Lewis active acid sites. In relation to the effect of Ni impregnation method, acidity, amount of sulfate and Ni found in Ni/SZ-R were higher than those in Ni/SZ-H. Unfortunately, higher impregnated sulfate and nickel on zirconia support led to a decrease in surface area and pore volume and an increase in crystallite size of grainy aggregated mesoporous nickel promoted sulfated zirconia (Ni/SZ).