Promotion of CeO2–ZrO2–Al2O3 composite by selective doping with barium and its supported Pd-only three-way catalyst

Advancements in low-temperature NH3-SCR of NOx using Ba-based catalysts: a critical review of preparation, mechanisms, and challenges

Presently, selective catalytic reduction (SCR), with either carbon monoxide, urea, hydrocarbons, hydrogen, or ammonia as a reductant, has become a nitrogen oxide (NOx) removal technology (NOx conversion) of many catalytic companies and diesel engine exhaust gas. Although, there exists a serious threat of low-temperature limitations. So far, certain scientists have shown that barium-based (Ba-based) catalysts have the potential to be highly effective at SCR of NOx at low temperatures when ammonia is used as the reducing agent. The process of NOx storage and reduction which alternate SCR is known as the Lean NOx trap. Herein, we give the condensed advancements and production of the catalysts that involve BaO in low-temperature NH3-SCR of NOx, the advantages of BaO catalysts compared to the recently hot electrocatalysis, the stability of BaO catalyst materials, and the condensed advancements and production of the catalysts that involve BaO in low-temperature NH3-SCR of NOx. These catalysts are viewed in the light of their preparation method, particulate, and posture in mixed oxides. Also, the characteristic features of Ba-based catalysts are carefully considered and briefed under the following areas: preparation method and precursor, crystallinity, calcination temperature, morphology, acid sites, the specific surface area for reaction, redox property, and activation energy of catalysts. More to these are the discussions on Eley-Rideal [E-R] and Langmuir-Hinshelwood [L-H] mechanisms, the H2O/SO2 and O2 permissiveness, and the NH3-SCR reaction mechanism over Ba-based catalysts highlighting their possible effects. Finally, we proposed the prospect and the likely future research plan for the low-temperature NH3-SCR of NOx.

Progress on metal-support interactions in Pd-based catalysts for automobile emission control

The interactions between metals and oxide supports, so-called metal-support interactions (MSI), are of great importance in heterogeneous catalysis. Pd-based automotive exhaust control catalysts, especially Pd-based three-way catalysts (TWCs), have received considerable research attention owing to its prominent oxidation activity of HCs/CO, as well as excellent thermal stability. For Pd-based TWCs, the dispersion, chemical state and thermal stability of Pd species, which are crucial to the catalytic performance, are closely associated with interactions between metal nanoparticles and their supporting matrix. Progress on the research about MSI and utilization of MSI in advanced Pd-based three-way catalysts are reviewed here. Along with the development of advanced synthesis approaches and engine control technology, the study on MSI would play a notable role in further development of catalysts for automobile exhaust control.

Assessment of the Synergetic Performance of Nanostructured CeO2-SnO2/Al2O3 Mixed Oxides on Automobile Exhaust Control

In order to control diesel exhaust emission, CeO₂-SnO₂/Al₂O₃ (CTA) mixed oxides were prepared and coated on perforated stainless steel (SS) filter plates, and the catalytic activities were analyzed in this work. The CeO₂-SnO₂ (different compositions of Ce/Sn-2:8; 1:1; 8:2) composites and Al₂O₃ were prepared separately via a co-precipitation approach, and CeO₂-SnO₂/Al₂O₃ (CTA) mixed oxides were attained by mechanical mixing of 75 wt% CeO₂-SnO₂ composites with 25 wt% Al₂O₃. X-ray diffraction (XRD) and Raman spectroscopy were performed for all three CeO₂-SnO₂/Al₂O₃ (CTA) mixed oxides; the CeO₂-SnO₂/Al₂O₃ (Ce/Sn-1:1) sample confirmed the presence of cubic and tetragonal mixed faces, which enhances the redox nature (catalytic activities). Various characterizations such as high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), and a scanning electron microscope (SEM) were employed on CeO₂-SnO₂/Al₂O₃ (Ce/Sn-1:1) sample to investigate the structural, textural, compositional, and morphological properties. The CeO₂-SnO₂/Al₂O₃ (Ce/Sn-1:1) sample was coated on a perforated stainless steel (SS) filter plate via a simple, cost-effective, and novel method, and an exhaust emission test for various compression ratios (CR), injection pressure (IP), and load (L) was completed using an AVL Digas analyzer. The CeO₂-SnO₂/Al₂O₃ (Ce/Sn-1:1) sample, with a size of 10.22 nm and a high surface area of about 73 m² g^-1, exhibit appreciable catalytic properties.

Engineering multicomponent metal-oxide units for efficient methane combustion over palladium-based catalysts

A composition modulation strategy was exploited to rationally design high-performance Mg-promoted Pd/Ce_xZr_1−xO₂–Al₂O₃ catalysts for methane combustion.

Recent advances in three-way catalysts of natural gas vehicles

This review presents recent advances in TWCs for NGVs, particularly for Pd-based catalysts and potential alternatives.

Perovskite lattice oxygen contributes to low-temperature catalysis for exhaust gas cleaning

A Pd catalyst supported on Ba-substituted LaAlO3 perovskite (Pd/La0.9Ba0.1AlO3-δ ) was investigated for NO reduction at low temperature by propylene, which revealed that Pd/La0.9Ba0.1AlO3-δ has remarkably higher activity than other Pd catalysts at low temperatures (≤573 K) for NO reduction by propylene. To elucidate the surface reaction pathway, transient response tests were conducted using 18O2. Also, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were conducted. Comparison with a Ba-impregnated catalyst (Pd/Ba/LaAlO3) demonstrated that Pd/La0.9Ba0.1AlO3-δ shows higher activity for the formation of oxygenated species (C x H y O z ) as an intermediate for NO reduction because the surface lattice oxygen has improved mobility via Ba2+ substitution in LaAlO3. Therefore, Pd/La0.9Ba0.1AlO3-δ have high activity for NO reduction, even at low temperatures in a humid condition.

Catalytic co-pyrolysis of waste vegetable oil and high density polyethylene for hydrocarbon fuel production

In this study, a ZrO₂-based polycrystalline ceramic foam catalyst was prepared and used in catalytic co-pyrolysis of waste vegetable oil and high density polyethylene (HDPE) for hydrocarbon fuel production. The effects of pyrolysis temperature, catalyst dosage, and HDPE to waste vegetable oil ratio on the product distribution and hydrocarbon fuel composition were examined. Experimental results indicate that the maximum hydrocarbon fuel yield of 63.1wt. % was obtained at 430°C, and the oxygenates were rarely detected in the hydrocarbon fuel. The hydrocarbon fuel yield increased when the catalyst was used. At the catalyst dosage of 15wt.%, the proportion of alkanes in the hydrocarbon fuel reached 97.85wt.%, which greatly simplified the fuel composition and improved the fuel quality. With the augment of HDPE to waste vegetable oil ratio, the hydrocarbon fuel yield monotonously increased. At the HDPE to waste vegetable oil ratio of 1:1, the maximum proportion (97.85wt.%) of alkanes was obtained. Moreover, the properties of hydrocarbon fuel were superior to biodiesel and 0^# diesel due to higher calorific value, better low-temperature low fluidity, and lower density and viscosity.

Enhanced performance of a Pt-based three-way catalyst using a double-solvent method

A new Pt-based three-way catalyst (TWC) for compressed natural gas (CNG) exhausts emissions was developed using a double-solvent method.