Cordierite Monolithic Catalyst Research Articles

Catalytic Activity and Mechanical Stability of ZIFs‐Derived CoCeOx/Cordierite Monolithic Catalysts

AbstractBimetallic oxide catalysts derived from zeolitic imidazolate frameworks (ZIFs) have good catalytic oxidation activity, but their application is limited because the powder is not conducive to industrial production. In this study, CoCeOx/cordierite monolithic catalysts derived from ZIFs were prepared by a simple impregnation method. Firstly, a phase transition of Co‐ZIF was induced in ethanol solution by adding excessive Ce(NO3)3. Subsequently, tannic acid (TA) was used to chelate excess metal on the surface to expose more active sites. Meanwhile, TA staying on the surface of the precursor could also prevent the accumulation of Ce at high temperatures. After the activity test, CoCeOx/cordierite showed excellent activity for the catalytic oxidation of o‐xylene with a T90 of 295 °C. The mechanical stability of the catalyst was also tested by ultrasonic vibration method. In addition, we investigated the influence of factors such as impregnation cycles and TA treatment time on the physical and chemical properties. This paper provides a new idea for preparing monolithic catalysts derived from ZIFs.

Weakening Mn-O Bond Strength in Mn-Based Perovskite Catalysts to Enhance Propane Catalytic Combustion.

Exploring highly efficient and robust non-noble metal catalysts for VOC abatement is crucial but challenging. Mn-based perovskites are a class of redox catalysts with good thermal stability, but their activity in the catalytic combustion of light alkanes is insufficient. In this work, we modulated the Mn-O bond strength in a Mn-based perovskite via defect engineering, over which the catalytic activity of propane combustion was significantly enhanced. It demonstrates that the oxygen vacancy concentration and the Mn-O bond strength can be efficiently modulated by finely tuning the Ni content in SmNixMn1-xO3 perovskite catalysts (SNxM1-x), which in turn can enhance the redox ability and generate more active oxygen species. The SN0.10M0.90 catalyst with the lowest Mn-O bond strength exhibits the lowest apparent activation energy, over which the propane conversion rate increases by 3.6 times compared to that on the SmMnO3 perovskite catalyst (SM). In addition, a SN0.10M0.90/cordierite monolithic catalyst can also exhibit a remarkable catalytic performance and deliver excellent long-term durability (1000 h), indicating broad prospects in industrial applications. Moreover, the promotional effect of Ni substitution was further unveiled by density functional theory (DFT) calculations. This work brings a favorable guidance for the exploration of highly efficient perovskite catalysts for light alkane elimination.

Experimental study of low-temperature combustion performance in hydrogen/air mixtures over Pt–Cu/HZSM-5/cordierite bimetallic catalysts

Catalytic combustion provides a feasible technology to effectively avoid NOx formation due to the high temperature in the process of hydrogen combustion. Recently, the development of efficient and affordable catalysts has attracted extensive attention as the cost of noble metals remained high. In this study, a list of cordierite monolithic catalysts with low noble metal loading are prepared by introducing the appropriate amount of transition metals (Mn, Cu, Fe, Co, and Ce), and their catalytic performance are further investigated. On this basis, the study on catalytic stability and kinetic is carried out, and the synergistic interaction between the bimetals is revealed with comprehensive characterization methods. The results show that Cu could promote the reaction rate of the Pt-based catalyst which show the best catalytic performance with the Cu loading of 1 g/L. The ignition temperature T10 is 58.5 °C, and the burnout temperature T100 is 100 °C, with activation energy as low as 44.00 kJ/mol. The enhancement of the catalytic performance is attributed to the interaction between the bimetallic elements. On the one hand, the valence state of Cu and Pt is changed, and on the other hand the dispersion of Pt get improved, which contributed to the catalytic reaction rate.

Ru-based monolithic catalysts for the catalytic oxidation of chlorinated volatile organic compounds.

A series of cordierite monolithic catalysts with Ru species supported on different available low-cost carriers were prepared and investigated for the elimination of CVOCs. The results suggest that the monolithic catalyst with Ru species supported on anatase TiO2 carrier with abundant acidic sites exhibited the desired catalytic activity for DCM oxidation with the T 90% value of 368 °C. In addition, a pseudo-boehmite sol used as binder was introduced into the preparation of the monolithic catalysts to further improve the adhesion between the powder catalysts and cordierite honeycomb carrier. The results suggest that although the T 50% and T 90% of the Ru/TiO2/PB/Cor shifted to higher temperature of 376 and 428 °C, the weight loss of the coating for the Ru/TiO2/PB/Cor catalyst was improved and decreased to 6.5 wt%. Also, the as-obtained Ru/TiO2/PB/Cor catalyst exhibited ideal catalytic properties for the abatement of ethyl acetate and ethanol, indicating that the catalyst can meet the demand for the treatment of actual multi-component industrial gas.

Effect of Acid Treatment on the Catalytic Activity and Mechanical Stability of SmMnO3/Cordierite Monolithic Catalysts

AbstractSmMnO3/cordierite monolithic catalysts were synthesized by a modified citric acid method and treated with dilute HNO3, which was used to explore the effect of acid treatment on the catalytic performance and mechanical stability of the monolithic catalysts. Firstly, acid treatment can significantly improve catalytic activity of catalyst in o‐xylene oxidation, which is attributed to the increase of the specific surface area of the catalyst and the change of surface oxygen species. A series of single factor experiments show that the SmMnO3/cordierite monolithic catalyst treated by 1.0 mol/L HNO3 for 6 h and calcined at 450 °C for 1 h has the best performance. Furthermore, the mechanical stability of the catalysts treated by dilute HNO3 was tested, which show that too long acid treatment time and too high acid concentration will reduce the mechanical stability of the catalyst and 1.0 mol/L HNO3 treatment for 1 h is the best. Different calcination temperature and calcination time will also affect the mechanical stability of the catalyst. Finally, the catalyst has good stability of catalytic performance and mechanical stability.

Preparation and Testing of Cordierite Monolithic Catalysts for Oxidation of Aromatic Volatile Organic Compounds

This work reports the results of catalytic oxidation of aromatic volatile organic compounds (VOCs). A gaseous mixture of benzene, toluene, ethylbenzene, and o-xylene (BTEX) in nitrogen was used as representative of VOCs. Reactions were carried out in a monolithic reactor at different temperatures, with a constant initial concentration of reactants and a constant ratio of BTEX and oxidant (synthetic air). Analysis of the oxidation products was carried out on-line before and after reaction using gas chromatography. The work involves the preparation of catalysts and their application on an inert cordierite monolithic carrier, using different combinations of mixed manganese oxides (manganese with copper, iron, and nickel) and palladium as a representative of noble metals. The prepared cordierite monolithic catalysts showed great mechanical stability and high performance regarding oxidation of the mixture of aromatic compounds. High conversion values (90 %) of all components of the mixture were achieved at temperatures below 200 °C, depending on the chemical composition of the catalytic layer. A comparison with the activity of a commercial monolithic catalyst (Purelyst PH-304), which contains Pt and Pd as catalytically active components, using toluene as a model component. A comparison of the prepared manganese oxides showed that MnFeOx and MnCuOx had the best catalytic activity. When Pd was used in combination with MnFeOx in a form of a single monolith, where Pd was applied to ¼ of the overall monolith length and MnFeOx to ¾ of overall length, achieved 90 % conversions (T90) were up to 20 °C lower when compared with the same MnFeOx monolithic catalysts without Pd. Based on the comparison of the prepared ceramic monolithic catalysts with a commercial catalyst and because the comparison was made only based on toluene conversion, it was concluded that the prepared catalysts can be considered as alternatives to commercial monolithic catalysts by introducing a low concentration of Pd.

Preparation of cordierite monolithic catalyst for α-methylstyrene hydrogenation in a rotating packed bed reactor

A rotating packed bed (RPB) reactor with excellent mass transfer performance can be applied for catalytic reactions. However, the structure of catalyst particles randomly inside the rotor of the RPB reactor was easily deformed under the centrifugal field. In this work, a cordierite (COR) monolithic catalyst with high mechanical strength was prepared, aiming to be used in the RPB reactor for hydrogenation. The acid pretreatment and Al2O3 coating were employed to increase the specific surface area of COR substrate. Active component palladium (Pd) was deposited on Al2O3/COR. Hydrogenation of α-methylstyrene (AMS) was selected as a model reaction for the RPB reactor with the above Pd/Al2O3/COR. Experimental results show that the space time yield (STY) in the RPB reactor was effectually enhanced 9.2 times higher than that in the fixed bed reactor at the operation conditions of 30 °C and 0.2 MPa, which shows potential prospects of the RPB reactor with Pd/Al2O3/COR monolithic catalyst for the process intensification of catalytic reaction.

Temperature-dependent reaction pathways of CO oxidation and the application as monolithic catalysts for Co3O4 nanorods

Via investigating the evolution of carbonate intermediates by in-situ DRIFTS (25 °C–350 °C) analysis, temperature-dependent reaction pathways of CO oxidation over Co3O4 nanorods are successfully proposed. The types of reactive oxygen species participated in CO oxidation may affect the way CO react with neighboring oxygen atoms. Additionally, the negative effect of water and CO2 on the catalytic activity was also studied. Considering the remarkable reactivity towards CO, the Co3O4 catalysts were integrated onto metallic and cordierite monolithic substrates and used for CO conversion as application. SEM examinations show that the catalyst layer was coated on the substrates uniformly with few microcracks, and desirable mechanical shock and thermal shock resistance was observed. The influence of substrate materials, gas hourly space velocity, the existence of water vapor and CO2, and reaction time on the CO oxidation performance of monolithic catalysts was investigated. Metallic monolithic catalysts performed higher CO oxidation activity mainly owing to superior heat conductivity and larger surface area compared with cordierite monolithic catalysts. It is noticeable that superior activity was also achieved under high gas flow with the existence of H2O (5.6 vol.%) and CO2 (7 vol.%) at 220 °C, suggesting great promise for practical application.

Low temperature catalytic activity of Ag based SCR catalysts with 2-propanol—toluene mixture as reductant

In this experimental investigation, synthesized Ag-Cu-Pt-Ce/cordierite monolithic catalyst were studied in order to determine low temperature catalytic activity. The catalyst was characterized by Field Emission-Scanning Electron Microscopy (FE-SEM) and x-ray Fluorescence (XRF). Selective Catalytic Reduction (SCR) performance tests with 2-propanol-toluene mixture as reductant were carried out with using exhaust gas sample of a diesel engine. NOx conversion rates were measured at various space velocities such as 20000, 30000 and 40000 h−1 and engine loads of 1 kW, 2 kW, 3 kW and 4 kW ranging from 170 to 260 °C exhaust gas temperature with the intervals of 10 °C. The characterization analysis of catalysts showed that coating process has been performed successfully due to the well-dispersed metallic particles to catalyst surface and pores. The results also demonstrated that the NOx conversion rates increased due to the increment in exhaust gas temperature which has significant effect on catalytic activity. In conclusion, the maximum NOx conversion rate was obtained as 68.4% at the engine load of 4 kW, 20000 h−1 and at 260 °C.

Boron nitride wash-coated cordierite monolithic catalyst showing high selectivity and productivity for oxidative dehydrogenation of propane

Hexagonal boron nitride (h-BN) is a burgeoning catalyst for oxidative dehydrogenation of propane (ODHP) with impressive light olefins selectivity, which deserves further study to optimize the heat and mass transfer process with the aim of promoting the potential industrial application since ODHP is a highly exothermic process. Herein, h-BN wash-coated cordierite monolithic catalyst was designed through a chemical vapor deposition method using boron acid and urea as precursors, which was used for ODHP reaction and exhibited a ∼16.8% conversion of propane and 82.1% selectivity towards propylene, with only 3.7% selectivity of CO and no detected CO2, at temperature of 535 ℃ and a high gas hourly space velocity (GHSV) of 576,000 mL/gBNh. The typical structure of h-BN/Cordierite with well-developed straight-channel and short diffusive pathway of the thin wash-coated h-BN layer guarantee the mass transfer process at high GHSV, achieving a high propylene space time yield of 18.6 gC3H6 gBN−1 h−1 and improving the selectivity towards propylene and ethylene by suppressing secondary reactions of deep oxidation. Meanwhile, the high GHSV and excellent thermal conductivity of h-BN contribute to the heat transfer during reactions.

A facile route for spraying preparation of Pt/TiO2 monolithic catalysts toward VOCs combustion

This study presents an efficient, economic, and simple preparation strategy for Pt/TiO2 monolith catalysts. Nano-Pt/TiO2 dispersion liquid with good activity and stability was synthesized by hydrolysis and chemical reduction method. Various Pt/TiO2 monolithic catalysts were prepared by spraying the dispersion liquid on different substrates. Results of transmission electron microscopy, scanning electron microscopy, N2 adsorption-desorption, H2 temperature-programmed and CO oxidation showed that the Pt/TiO2 nanoparticles with good mesoporous structure and redox properties were highly dispersed on the substrate. The as-prepared 0.5 Pt/TiO2 cordierite monolithic catalyst with 0.1 wt‰ Pt content exhibited excellent catalytic combustion activity (T90 of toluene combustion was 212 ℃), stability (no deactivation was observed during a 120 h test) and firmness (mass loss was 0.11% after 1 h ultrasonic vibration) under experimental conditions. Compared with state-of-the-art methods, this method is more suitable for large-scale production of waste-gas-treated monolith catalysts. And this method meets the concept of energy saving and emission reduction because of its simplicity, high efficiency, environmental friendliness, and high utilization of active components.

High-performance HZSM-5/cordierite monolithic catalyst for methanol to propylene reaction: A combined experimental and modelling study

Methanol to propylene (MTP) reaction system over HZSM-5 zeolites is characterized by obvious consecutive side reactions to paraffin and aromatics, which practically gives rise to a low propylene yield. In this work, HZSM-5/cordierite monolithic honeycomb catalyst was prepared by washcoating method and investigated in a lab fixed-bed reactor. Compared to the traditional extrudes, the monolithic honeycomb accelerated methanol conversion rate by 2.78 and 6.66 times when methanol was fed alone and co-fed with butene, respectively, and reduced the output of paraffin and aromatics by 90% when methanol was co-fed with butene. A two-dimensional mathematic model was then developed to simulate the HZSM-5/cordierite catalyst and validated by experimental data. On the basis of a commercial configuration of MTP reactor, a six-stage adiabatic fixed-bed reactor was simulated with ethylene and C4–C6 olefins recycled, the calculated space velocity and propylene selectivity for monolithic catalyst can be as high as 5.27gMeOH/gcat/h and 81.6%, with significant enhancement achieved compared to the conventional catalyst with the results of 0.741 and 62.6%, respectively.

Total oxidation of ethanol over Au/Ce0.5Zr0.5O2 cordierite monolithic catalysts

The aim of this work was to propose the methods for gold introduction during the preparation of monolithic catalysts and to investigate their effect on catalyst properties. Two types of catalysts were prepared: (i) monoliths washcoated with gold/ceria-zirconia powder, and (ii) gold deposited on the monoliths washcoated with ceria-zirconia powder. An important part of the work was the characterization of the catalysts, in particular Au particle size and redox properties. Catalytic performance and selectivity were evaluated using ethanol gas-phase oxidation. It was shown that the enhanced reducibility of the catalysts with higher Au dispersion leads to improved catalytic performance.

Demonstration of Pilot-scale Bio-dimethyl ether Synthesis Via Oxygen- and steam- enriched Gasification of Wood Chips

The demonstration operation of an pilot-scale bio-dimethyl ether(DME) synthesis system was carried out for with 300-350 kg/h of wood chips as feedstock. The tar content was 4.4-5.7 g/Nm3 and carbon percent in the residual char was low due to the combined advantages of the specific gasifier combining with upstream and downstream gasification with O2-rich air(46.3vol%), fed through the top and bottom inlets of the gasifier. Steam, as the secondary gasifying agent, also increased H2 content in the raw bio-syngas. The reforming of tar and light hydrocarbons further decreased tar content to 0.42-0.67 g/Nm3 over Ni-MgO/γ-Al2O3 cordierite monolithic catalysts with less than 5.0vol% of CH4 content in the raw bio-syngas. CO2 removal efficiency was about 70% by pressure-swing unit(PSA), using propylene carbonate as adsorbent. CO conversion and space-time yield of DME over Cu/Zn/Al/HZSM-5-packed fixed-bed tubular reactor were 61.4-71% and 90.4-155.8 kg/mcat3/h respectively when the gas hourly space velocity(GHSV) was 650-1500 h-1 at 220oC and 4.3 MPa. The selectivity of methanol and hydrocarbons were than less 3% under the typical operation condition. About 15.7% carbon of dried wood chip was converted to DME with the production cost of ca. ¥4810/ton DME.

In-situ hydrothermal synthesis of Cu-SSZ-13/cordierite for the catalytic removal of NOx from diesel vehicles by NH3

Cu-SSZ-13/cordierite monolithic catalyst was prepared by in situ hydrothermal synthesis method. The physicochemical properties of the as-prepared Cu-SSZ-13/cordierite were investigated by X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, N2-adsorption, inductively coupled plasma, X-ray photoelectron spectroscopy, and solid-state NMR techniques. The removal of nitrogen oxides (NOx) from simulated diesel vehicle exhaust gas was performed using fixed-bed reactor. The effects of crystallization time and addition of HF during hydrothermal synthesis, reaction space velocity, and aging treatment of catalyst on the catalytic performances of NOx reduction reactions were investigated. The results indicate that the optimum crystallization time was 72h. Highly crystalline structure of zeolite Cu-SSZ-13 was formed, in a close combination with a carrier, via one step hydrothermal process. Cu-SSZ-13/cordierite showed excellent DeNOx performance for selective catalytic reduction (SCR) and anti-aging properties in a simulated diesel exhaust gas under a high space velocity. At a high space velocity of 72,000h−1, the highest conversion and N2 selectivity of 94% and 90%, respectively, were achieved. After the aging for 50h at 720°C, NOx reduction rate was still >80% in the temperature range of 350–550°C. The larger height to diameter ratio of the same catalysts enhanced the NH3-SCR catalytic activity and broadened the active temperature window. The addition of HF increased the catalytic activity and anti-aging performance of the sample.

Preparation, Structure Characterization and Hydrodesulfurization Performance of B-Ni2P/SBA-15/Cordierite Monolithic Catalysts

A series of B-Ni2P/SBA-15/cord monolithic catalysts were prepared by coating the slurry of the B-Ni2P/SBA-15 precursors on a pretreated cordierite support, and followed by temperature-programmed reduction in a H2 flow. The samples were characterized by X-ray diffraction (XRD) and N2 adsorption–desorption technique. The catalytic activities for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) were evaluated. The results showed that Ni2P phase was present in all B-Ni2P/SBA-15/cord monolithic catalysts. The specific surface areas (SBET) of the B-Ni2P/SBA-15/cord monolithic catalysts was first increased to 167m2·g−1, and then decreased to 155m2·g−1 with the increase of boron contents. The catalytic activity also showed the similar trend with the increase of boron contents. The 1.75% (by mass) B-Ni2P/SBA-15/cord monolithic catalysts exhibited the highest DBT conversion of 98.4% at 380°C. The cordierite-based monolithic catalysts showed better low temperature sensitivity for HDS of DBT in comparison with the particle catalysts. Moreover, two HDS routes, direct desulfurization (DDS) and hydrogenation (HYD), proceeded independently over B-Ni2P/SBA-15/cord monolithic catalysts and the main pathway was DDS.

Mechanical stability of monolithic catalysts: Factors affecting washcoat adhesion and cohesion during preparation

Alumina‐washcoated cordierite monoliths are prepared to investigate the effects of the preparation process factors on the mechanical stability of monolithic catalysts. It is shown that the agent for pretreating substrates, properties of the washcoating solution (solid content, additive, and amount of additive), and washcoating times all have great effects on the washcoat loading and on the washcoat adhesion and cohesion. There is a great possibility of improving the mechanical stability through the optimization of these factors. If multiple washcoating is performed, the two‐time washcoating after calcination is recommended in this case. It is also pointed out that the minor variation of the washcoat loading with monolithic mini‐specimen increases the scatter of the washcoat adhesion and cohesion, resulting from fatigue failure of active material. Furthermore, the previously proposed mechanical failure mechanism is confirmed to be an effective tool to factors analysis of the mechanical stability of cordierite monolithic catalysts. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2765–2773, 2014

<i>In Situ</i> Synthesis of Cu-SAPO-34/Cordierite with Ultrasonic Treatment and its Property of NOx Removal

A Cu-SAPO-34/cordierite monolithic catalyst was prepared by in-situ hydrothermal method. The effects of ultrasonic treatment were mainly investigated during the preparing process. The removal of NOX was evaluated using a fixed-bed reactor. X-ray diffraction, scanning electron microscopy were used to characterize the samples showing that the crystallinity of Cu-SAPO-34 molecular sieve have increased after ultrasonic treatment. The Cu-SAPO-34/cordierite prepared by ultrasonic treatment showed higher de-NOx activity and stronger anti-aging property. NOx conversion could reach more than 80% between 440 and 560°C over the fresh Cu-SAPO-34/cordierite catalyst with ultrasonic treatment (600 W, 2 h) and the highest conversion was 86%, however, the highest conversion was only 76% over the Cu-SAPO-34/cordierite catalyst without ultrasonic treatment. After aging (treated for 15 h at 720 °C in the presence of 200 ppm SO2 and 10% vapor), NOx conversion reached more than 45% between 400 and 520 °C over the catalyst with ultrasonic treatment and the highest conversion was 57%, however, the highest conversion was only 43% over the catalyst without ultrasonic treatment. The XRD and SEM results indicated that the structure and morphology of Cu-SAPO-34/cordierite monolithic catalyst kept in good condition after aging.

Preparation of TS-1 Monolithic Catalysts and Activity Evaluation for Cyclohexanone Ammonization Reaction

The Titanium silicalite-1 (TS-1)/cordierite monolithic catalysts prepared by wash coating-method were investigated by means of experiments in which we discussed the effects of TS-1 mass fraction in slurry, coating times and solvent viscosity on loading amount and adhesiveness. The results of cyclohexanone ammonization in self-made recirculating reactor showed that the activity and stability of TS-1 monolithic catalysts supported on cordierite honeycomb were better than traditional TS-1 powder in slurry reactor.

Hydrogenation of dimethyl oxalate to ethylene glycol on a Cu/SiO2/cordierite monolithic catalyst: Enhanced internal mass transfer and stability

AbstractThe design and application of a Cu/SiO2‐based monolithic catalyst for hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) is presented. The catalyst was dip‐coated on cordierite with highly dispersed Cu/SiO2 slurry prepared by ammonia evaporation method. This structure guarantees high dispersion of copper species within the mesopores of silica matrix in the form of copper phyllosilicate. The catalyst is low cost, stable, and exhibits high activity in the reaction of hydrogenation of DMO, achieving a 100% conversion of DMO and more than 95% selectivity to EG. Notably, STYEG over the monolith is significantly enhanced compared to the packed bed Cu/SiO2 catalysts in both forms of pellet and cylinder. It is primarily due to the relatively short diffusive pathway of the thin wash‐coat layer and high efficiency of the active phase derived from the monolithic catalyst. Theoretical results indicated that the internal mass transfer is dominated on the catalysts of pellet and cylinders. Moreover, the monolithic catalyst possessed excellent thermal stability compared to the pellet catalyst, which is attributed to the regular channel structure, uniform distribution of flow. © 2011 American Institute of Chemical Engineers AIChE J, 2012