Rice Husk Derived Porous Silica as Support for Pd and CeO2 for Low Temperature Catalytic Methane Combustion

Abstract

The separation of Pd and CeO2 on the inner surface of controlled porous glass (CPG, obtained from phase-separated borosilicate glass after extraction) yields long-term stable and highly active methane combustion catalysts. However, the limited availability of the CPG makes such catalysts highly expensive and limits their applicability. In this work, porous silica obtained from acid leached rice husks after calcination (RHS) was used as a sustainable, cheap and broadly available substitute for the above mentioned CPG. RHS-supported Pd-CeO2 with separated CeO2 clusters and Pd nanoparticles was fabricated via subsequent impregnation/calcination of molten cerium nitrate and different amounts of palladium nitrate solution. The Pd/CeO2/RHS catalysts were employed for the catalytic methane combustion in the temperature range of 150–500 °C under methane lean conditions (1000 ppm) in a simulated off-gas consisting of 9.0 vol% O2, and 5.5 vol% CO2 balanced with N2. Additionally, tests with 10.5 vol% H2O as co-feed were carried out. The results revealed that the RHS-supported catalysts reached the performance of the cost intensive benchmark catalyst based on CPG. The incorporation of Pd-CeO2 into RHS additionally improved water-resistance compared to solely Pd/CeO2 lowering the required temperature for methane combustion in presence of 10.5 vol% H2O to values significantly below 500 °C (T90 = 425 °C).

Sustainable Biodiesel Synthesis from Honne-Rubber-Neem Oil Blend with a Novel Mesoporous Base Catalyst Synthesized from a Mixture of Three Agrowastes

“…Heterogenous catalysis offers several advantages including recyclability, easy separation, non-corrosiveness, higher selectivity, environmentally benign nature and longer catalyst life [4,5]. Exploitation of wastes for catalyst development in biodiesel production could be used to mitigate environmental damage [9,10]. Currently, a lot of effort has been put into development of heterogeneous solid acid and alkali catalysts for biodiesel synthesis which may help reduce overall production costs.…”

“…Evidence from several works indicate that this approach has been successfully applied for biodiesel production. Sources of biomass-derived catalysts include waste shells, biomass ashes, activated carbon-supported catalysts, animal bones and waste coral [10][11][12][13][14][15].…”

Generation of High Quality Biogenic Silica by Combustion of Rice Husk and Rice Straw Combined with Pre- and Post-Treatment Strategies—A Review

“…10-20 wt % of the initial fuel remains as ash rich in silica (i.e., "biogenic silica"). It can be an economically valuable material for various applications including the cement and concrete industry [25][26][27], an adsorbent to remove heavy metal ions such as lead (II), mercury (II), zinc (II) and nickel (II) ions from wastewater streams, as catalyst [28][29][30][31][32][33][34][35][36][37][38], for synthesis of zeolites and mesoporous silica [39][40][41][42][43][44][45][46] or for drug delivery systems [47,48]. Depending on the anticipated application, biogenic silica is required with different purities.…”

Comparative Study of the Characteristics and Activities of Pd/γ-Al2O3 Catalysts Prepared by Vortex and Incipient Wetness Methods

“…Several Pd catalysts have also been developed using other supports. Liu et al [10] developed a rice husk derived porous silica support for a Pd-CeO 2 catalyst for low temperature combustion of methane with 90% conversion at 325 • C. A monolithic Pd/Al 2 O 3 /Fe-Ni catalyst with metal foam as matrix in a microcombustor improved methane conversion to more than 99% [11]. Cargnello et al [12] developed a novel Pd@CeO 2 /hydrophobic-Al 2 O 3 core-shell catalyst that had methane conversions of 50% and 100% at 325 • C and 400 • C respectively.…”