The Effect of ZrO2 as Different Components of Ni-Based Catalysts for CO2 Reforming of Methane and Combined Steam and CO2 Reforming of Methane on Catalytic Performance with Coke Formation

Abstract

The role of ZrO2 as different components in Ni-based catalysts for CO2 reforming of methane (CRM) has been investigated. The 10 wt.% Ni supported catalysts were prepared with ZrO2 as a support using a co-impregnation method. As a promoter (1 wt.% ZrO2) and a coactive component (10 wt.% ZrO2), the catalysts with ZrO2 were synthesized using a co-impregnation method. To evaluate the effect of the interaction, the Ni catalyst with ZrO2 as a coactive component was prepared by a sequential impregnation method. The results revealed that the activity, the selectivity, and the anti-coking ability of the catalyst depend upon the ZrO2 content, the Ni-ZrO2 interaction, basicity, and oxygen mobility of each catalyst resulting in different Ni dispersion and oxygen transfer pathway from ZrO2 to Ni. According to the characterization and catalytic activation results, the Ni catalyst with low ZrO2 content (as a promoter) presented highest selectivity toward CO owning to the high number of weak and moderate basic sites that enhance the CO2 activation-dissociation. The lowest activity (CH4 conversion ≈ 40% and CO2 conversion ≈ 39%) with the relatively high quantity of total coke formation (the weight loss of the spent catalyst in TGA curve ≈ 22%) of the Ni catalyst with ZrO2 as a support is ascribed to the lowest Ni dispersion due to the poor Ni-ZrO2 interaction and less oxygen transfer from ZrO2 to the deposited carbon on the Ni surface. The effect of a poor Ni-ZrO2 interaction on the catalytic activity was deducted by decreasing ZrO2 content to 10 wt.% (as a coactive component) and 1 wt.% (as a promoter). Although Ni catalysts with 1 wt.% and 10 wt.% ZrO2 provided similar oxygen mobility, the lack of oxygen transfer to coke during CRM process on the Ni surface was still indicated by the growth of carbon filament when the catalyst was prepared by co-impregnation method. When the catalyst was prepared by a sequential impregnation, the intimate interaction of Ni and ZrO2 for oxygen transfer was successfully developed through a ZrO2-Al2O3 composite. The interaction in this catalyst enhanced the catalytic activity (CH4 conversion ≈ 54% and CO2 conversion ≈ 50%) and the oxygen transport for carbon oxidation (the weight loss of the spent catalyst in TGA curve ≈ 7%) for CRM process. The Ni supported catalysts with ZrO2 as a promoter prepared by co-impregnation and with ZrO2 as a coactive component prepared by a sequential impregnation were tested in combined steam and CO2 reforming of methane (CSCRM). The results revealed that the ZrO2 promoter provided a greater carbon resistance (coke = 1.213 mmol·g−1) with the subtraction of CH4 and CO2 activities (CH4 conversion ≈ 28% and CO2 conversion ≈ %) due to the loss of active sites to the H2O activation-dissociation. Thus, the H2O activation-dissociation was promoted more efficiently on the basic sites than on the vacancy sites in CSCRM.

Tri-reforming of CH4 over a Thermally Stable and Carbon-Resistant Nanonickel Metal Catalyst Dispersed on Mesoporous-Zirconia

“…Further, the pure H 2 pulse injection was given with a time interval of 5 min until the identical hydrogen peak area was achieved in the TCD. After completion of the experiments, the active nickel surface area and metal dispersion were determined by using the equation discussed elsewhere …”

“…After completion of the experiments, the active nickel surface area and metal dispersion were determined by using the equation discussed elsewhere. 30 The basic strength of the reduced catalyst was determined by the CO 2 temperature-programmed desorption (CO 2 -TPD) technique. The CO 2 -TPD experiments were performed in Micromeritics ChemiSorb-2750 equipment (USA) equipped with a TCD instrument to quantify the amount of desorbed CO 2 .…”

Accelerated H2 activation over Pt/M-ZrO2 for the reductive amination of levulinic acid esters under benign conditions

“…† M-ZrO 2 exhibited basic sites with different strengths such as weak (100-200 °C), medium (200-550 °C) and strong (>550 °C). 50 Likewise, Pt/M-ZrO 2 displayed a similar profile pattern with a decreased and increased intensity of weak and strong acid site regions, respectively. The total number of basic sites rose slightly in the case of Pt/M-ZrO 2 (415 μmol g −1 ) compared with M-ZrO 2 (382 μmol g −1 ).…”

Combined Steam and CO2 Reforming of Methane over the Hierarchical Ni-ZrO2 Nanosheets/Al2O3 Catalysts at Ultralow Temperature and under Low Steam

“…In addition, ZrO 2 provides the great mechanical strength and high thermal stability. − Meanwhile, ZrO 2 creates the oxygen mobility from redox properties and presents high Lewis basicity. − Our previous work studied a ZrO 2 -promoted Ni-based catalyst for CSCRM. ZrO 2 enhances H 2 production by promoting the steam adsorption-dissociation via oxygen vacancies . Dharmasaroja et al revealed preparation of hierarchical Ni layered hydroxide via novel ammonia vapor diffusion impregnation.…”

“…ZrO 2 enhances H 2 production by promoting the steam adsorption-dissociation via oxygen vacancies. 24 Dharmasaroja et al revealed preparation of hierarchical Ni layered hydroxide via novel ammonia vapor diffusion impregnation. The advantages of the ammonia vapor diffusion impregnation method comprise low temperature and cost saving.…”