Oxidative coupling of methane in a dual-bed reactor comprising of particle/cordierite monolithic catalysts

A dual-bed reactor was constructed comprising of a 5%Na2WO4-2%Mn/SiO2 particle catalyst and a 4%Ce-5%Na2WO4-2%Mn/SiO2 /cordierite monolithic catalyst.The reaction performance of the oxidative coupling of methane （OCM） over the dual-bed reactor system was evaluated.The effects of the bed height and operation mode,as well as the reaction parameters such as reaction temperature,CH4/O2 ratio and flowrate of feed gas,on the catalytic performance were investigated.The results indicated that the suggested dual-bed reactor exhibited a good performance for the OCM reaction when the feed gases firstly passed through the particle catalyst bed and then to the monolithic catalyst bed.A CH4 conversion of 38.2% and a C2H4 selectivity of 43.3% could be obtained using the dual-bed reactor with a particle catalyst bed height of 10 mm and a monolithic catalyst bed height of 50 mm.Both the CH4 conversion and C2H4 selectivity have increased by 2.5% and 12.8%,respectively,as compared with the 5%Na2WO4-2%Mn/SiO2 particle catalyst in a conventional single-bed reactor and by 12.9% and 23.0%,respectively,as compared with the 4%Ce-5%Na2WO4-2%Mn/SiO2 /cordierite monolithic catalyst in a single-bed reactor.The catalytic performance of the OCM in the dual-bed reactor system has been improved remarkably.

Metal-Support Interactions on Ag/Co_(3)O_(4)Nanowire Monolithic Catalysts Promoting Catalytic Soot Combustion

Tuning metal-support interactions(MSIs)is an important strategy in heterogeneous catalysis to realize the desirable metal dispersion and redox ability of metal catalysts.Herein,we use pre-reduced Co_(3)O_(4)nanowires(Co-NWs)in situ grown on monolithic Ni foam substrates to support Ag catalysts(Ag/Co-NW-R)for soot combustion.The macroporous structure of Ni foam with crossed Co_(3)O_(4)nanowires remarkably increases the soot-catalyst contact effi ciency.Our characterization results demonstrate that Ag species exist as Ag 0 because of the equation Ag^(+)+Co^(2+)=Ag^(0)+Co^(3+),and the pre-reduction treatment enhances interactions between Ag and Co_(3)O_(4).The number of active oxygen species on the Ag-loaded catalysts is approximately twice that on the supports,demonstrating the signifi cant role of Ag sites in generating active oxygen species.Additionally,the strengthened MSI on Ag/Co-NW-R further improves this number by increasing metal dispersion and the intrinsic activity determined by the turnover frequency of these oxygen species for soot oxidation compared with the catalyst without pre-reduction of Co-NW(Ag/Co-NW).In addition to high activity,Ag/Co-NW-R exhibits high catalytic stability and water resistance.The strategy used in this work might be applicable in related catalytic systems.

Catalytic combustion of toluene over Pd-based monolithic catalysts with a novel washcoat Ce_(0.8)Zr_(0.15)La_(0.05)O_δ

Two novel washcoats Ce0.8Zr0.15La0.05Oδ and Ce0.8Zr0.2O2 was prepared by an impregnation method, which acted as a host for the active Pd component to prepare Pd/Ce0.8Zr0.15La0.05Oδ/substrate and Pd/Ce0.8Zr0.2O2/substrate monolithic catalysts for toluene combustion. The washcoats was characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauner-Emmett-Teller (BET), and H2-temperature-programmed reduction (H2-TPR). The result indicated that both the washcoats had strong vibration-shock resistance according to ultrasonic test. Doping La3+ into CeO2-ZrO2 solid solution could generate more oxygen vacancies, and could inhibit the sinter of CeO2-ZrO2 solid solution when calcined at high temperatures (800, 900 and 1000 °C). The washcoat Ce0.8Zr0.15La0.05Oδ had much better redox properties. The reductive temperature of Ce4+ species shifted to low temperature by 60 °C when the washcoats calcined at high temperatures (800, 900 and 1000 °C). The Pd/Ce0.8Zr0.15La0.05Oδ/substrate monolithic catalyst calcination at 500 °C had the best catalytic activity and the 95% toluene conversion at a temperature as low as 190 °C. When calcined at low temperature (500 and 700 °C), the catalytic activity has little improvement, however, when calcined at high temperature, the catalytic activity of Pd/Ce0.8Zr0.15La0.05Oδ/substrate monolithic catalysts had significant improvement. As catalyst washcoat, the Ce0.8Zr0.15La0.05Oδ had better thermal stability than the washcoat Ce0.8Zr0.2O2, the developed Pd/Ce0.8Zr0.15La0.05Oδ/ substrate monolithic catalyst in this work was promising for eliminating Volatile organic compounds.

Particle/metal-based monolithic catalysts dual-bed reactor with beds-interspace supplementary oxygen:Construction and performance for oxidative coupling of methane

A novel particle/metal-based monolithic catalysts dual-bed reactor with beds-interspace supplementary oxygen is constructed comprising of the upper-layer 5 wt%Na2WO4-2 wt%Mn/SiO2 particle catalyst and the under-layer 3 wt%Ce-5 wt%Na2WO4-2 wt%Mn/SBA-15/Al2O3/FeCrA1 metal-based monolithic catalyst as well as a side tube in the interspaces of two layers for supplementing 02. The reaction performance of oxidative coupling of methane （OCM） in the dual-bed reactor system is evaluated. The effects of the reaction parameters such as feed CH4/O2 ratio, reaction temperature and side tube feed 02 flowrate on the catalytic performance are investigated. The results indicate that the suggested mode of dual-bed reactor exhibits an excellent performance for OCM. CH4 conversion of 33.2%, C2H4 selectivity of 46.5% and C2 yield of 22.5% could be obtained, which have been increased by 6.4%, 4.1% and 5.5%, respectively, as compared with 5 wt%Na2WO4-2 wt%Mn/SiO2 particle catalyst in a single-bed reactor and increased by 10.7%, 31.9% and 17.7%, respectively, as compared with 3 wt%Ce-5 wt%Na2WO4-2 wt%Mn/SBA-15/Al2O3/FeCrA1 metal-based monolithic catalyst in a single-bed reactor. The effective promotion of OCM performance in the reactor would supply a valuable reference for the industrialization of OCM process.

Catalytic Combustion of Methane over Co_(1-x)Mg_(x)O/Al_(2)O_(3)/FeCrAl Monolithic Catalysts

A series of CoxMgxO/Al2O3/FeCrAl catalysts （x=0-1） were prepared. The structures of the catalysts were characterized using XRD, SEM, and TPR analyses. The catalytic activity of the catalysts for methane combustion was evaluated in a continuous flow microreactor. The results indicated that the active washcoats adhered well on the FeCrAl foils. The phases in the catalysts were Co--xMgxO solid solutions, α-Al2O3, and γ-Al2O3. The surface particle size of the catalysts varied with variations in the molar ratios of Co to Mg. The Co component of the Co1_xMgxO/Al2O3/FeCrAl catalysts played an important role in the catalytic activity for methane combustion. In the Co1-xMgxO/AluO3/FeCrAl series catalyst （x=0.2-0.8）, the catalytic activity in terms of x was in the order of 0.5〉0.2〉0.8 under the experimental conditions. The presence of Mg in these catalysts could promote the thermal stability to a large extent. There were strong interactions between the Co1-xMgxO oxides and the AluO3/FeCrAl supports.

Toluene Combustion over Pd-Ce_(0.4)Zr_(0.6)O_2 Directly Washcoated Monolithic Catalysts

A Ce0.4Zr0.6O2 washcoat was prepared using an impregnation method, which acted as a host for the active Pd component to prepare a Pd-Ce0.4Zr0.6O2/substrate monolithic catalyst for toluene combustion. The catalyst was characterized by scanning electron microscopy （SEM）, Raman spectroscopy, Brunauner-Emmett-Teller （BET）, and carbon monoxide tonperature-programmed reduction （CO-TPR）. It was found that the washcoat had strong vibration-shock resistance according to an ultrasonic test. The Pd-Ce0.4Zr0.6O2/substrate monolithic catalyst calcined at 400 ℃ showed 95% toluene conversion at a temperature as low as 210 ℃. Furthermore, the lowest temperature for 95% toluene conversion was increased by 40℃ after the catalyst calcined at 900℃, indicating that the catalyst had good thermal stability. The results revealed that the developed catalyst in this study was promising for eliminating volatile organic compounds （VOCs）.

Catalytic combustion of VOCs on Pt/CuMnCe and Pt/CeY honeycomb monolithic catalysts

The metal oxides CuMnCe and CeY washcoats on cordierite were prepared using an impregnation method, and then used as support for the active Pt component to prepare the Pt/CuMnCe and Pt/CeY monolithic catalysts for the deep oxidation of VOCs. In comparison with the Pt/CeY, CuMnCe, and CeY monolithic catalysts, the Pt/CuMnCe monolithic catalyst shows an excellent performance for toluene,ethyl acetate,and n-hexane oxidation and the Tis low to 216, 200 and 260 ℃,respectively. The active components Pt/PtO and CuMnCe result in a better synergetic interaction, which promote the catalyst reducibility, increase the oxygen mobility, and enhance the adsorption and activation of organic molecules.

Preparation and characterizations of Ce-Cu-O monolithic catalysts for ethyl acetate catalytic combustion

Ce-Cu-O monolithic catalysts were prepared by using Ce0.9Cu0.1O1.9 solid solution or nitrate as precursors,and their catalytic performance for the combustion of ethyl acetate were studied.The catalysts calcined at a low temperature showed high catalytic activities.When calcined at high temperatures,the catalyst with Ce0.9Cu0.1O1.9 solid solution as precursor remained a high activity,while the catalyst with metal nitrates as precursors exhibited a suppressed reactivity.Therefore,the catalyst prepared with th...

Low-temperature and stable CO oxidation of Co_(3)O_(4)/TiO_(2) monolithic catalysts

Highly efficient Co_(3)O_(4)/TiO_(2) monolithic catalysts with enhanced stability were in-situ grown on Ti mesh for CO oxidation,which could completely oxidize CO at 120℃.The comprehensive catalytic performance is competitive to some noble metal catalysts and conventional Co_(3)O_(4) powder catalysts,which holds great potential toward industrial applications.Meanwhile,the in-situ synthesis strategy of Co_(3)O_(4)/TiO_(2) monolithic catalysts on flexible mesh substrate in this work can be extended to the development of a variety of oxide-based monolithic catalysts towards diverse catalysis applications.

One-Pot Three-Dimensional Printing Robust Self-Supporting MnO_(x)/Cu-SSZ-13 Zeolite Monolithic Catalysts for NH_(3)-SCR

Honeycomb cordierite coated with Cu-SSZ-13 zeolite is widely used for the selective catalytic reduction of NO_(x) with NH_(3)(NH_(3)-SCR)to reduce pollutants from vehicle emissions.However,conventional honeycomb catalysts fabricated via coating techniques are limited by low zeolite loadings,loss of the deposited zeolites,and complicated preparation processes.Herein,a facile,one-step three-dimensional(3D)printing strategy is developed to construct MnO_(x)/Cu-SSZ-13 monolithic catalysts with excellent catalytic performance for NH_(3)-SCR.Iron-containing halloysite nanotubes(Fe-HNTs)are introduced as printing ink additives to ensure mechanical stability and modulate the NH_(3)-SCR performance of monolithic catalysts in high temperature conditions.In situ incorporation of Mn into the Cu-SSZ-13 zeolite monoliths during the 3D printing process boosts the mechanical strength of the monolithic structures from 2.54 MPa to 4.33 MPa as well as broadens the temperature window(165-550℃)of the catalysts for NH_(3)-SCR with NO_(x) conversion of above 80%.Such robust multicomponent-integrated 3D-printed selfsupporting catalysts not only possess high zeolite loading and excellent catalytic activity,but also avoid complicated manufacturing processes,which contrasts with conventional honeycomb catalysts fabricated by extrusion coupled with coating.

Partial Oxidation of Methane over Monolithic Ni/CeO_2-ZrO_2/γ-Al_2O_3 Catalysts

A series of monolithic Ni/CeO_2-ZrO_2/γ-Al_2O_3 catalysts for the POM reaction were prepared. The activity test shows that the catalyst has the best performance when CeO_2-ZrO_2 content is 8 wt%.The synergistic actions between CeO_2-ZrO_2 and γ-Al_2O_3 improve highly catalytic activity by increasing CH_4 conversion, H_2 and CO selectivity. XPS analysis of the used catalyst indicates that there coexist Ce^(4+) and Ce^(3+).

Effect of Fe_2O_3 Loading Amount on Catalytic Properties of Monolithic Fe_2O_3/Ce_(0.67)Zr_(0.33)O_2-Al_2O_3 Catalyst for Methane Combustion

Ce0.67Zr0.33O2-Al2O3 solid solution was prepared by the co-precipitation method. Fe2O3-based catalysts supported on the solid solution were obtained by the impregnation method. The article revealed that the optimal loading amount of Fe2O3 on Ce0.67Zr0.33 O2-Al2O3 in our experimental condition for catalytic combustion of methane was 8% （ mass fraction）. The prepared catalysts were characterized by BET, TPR, XRD analyses, and their catalytic activity was investigated after being calcined at 873 K and after being aged in water gas at 1273 K. When the loading amount of Fe203 was 8% （ mass fraction）, the catalyst held the highest activity, and the best temperature speciality and thermal stability. The complete-conversion temperature of methane for fresh and aged sample was 788 and 838 K, respectively. The range between the light-off temperature and the complete-conversion temperature was only 15 K. The characterization results of XRD indicated that Fe2O3 was well dispersed on the Ce0.67Zr0.33O2-Al2O3 matrix. The results of BET and TPR were in good harmony with the catalytic activity results.

Preparation of Pd/c-Al_(2)O_(3)/nickel foam monolithic catalyst and its performance for selective hydrogenation in a rotating packed bed reactor

Selective hydrogenation plays an important role in chemical industries,yet its selectivity is usually limited by the mass transfer.In this work,the enhanced hydrogenation selectivity was achieved in a rotating packed bed(RPB)reactor with excellent mass transfer efficiency.Aiming to be used under the centrifugal filed,a monolithic catalyst Pd/c-Al_(2)O_(3)/nickel foam suiting for the shape and size of the rotor of RPB reactor was prepared by the electrophoretic deposition method.The mechanical strength of the catalyst can meet the requirement of high centrifugal force in the RPB.The hydrogenation selectivity in the RPB reactor using the 3-methyl-1-pentyn-3-ol hydrogenation system was 3–8 times higher than that in a stirred tank reactor under similar conditions.This work proves the feasibility of intensifying the selectivity of hydrogenation process in the RPB reactor.

Autothermal reforming of biogas over a monolithic catalyst

This study focused on measurement of the autothermal reforming of biogas over a Ni based monolithic catalyst. The effects of the steam/CH4 （S/C） ratio, O2/CH4 （O2/C） ratio and temperature were investigated. The CH4 conversions were higher under all examined temperatures than the equilibrium conversion calculated using the blank outlet temperature, because the catalyst layer was heated by the exothermic catalytic partial oxidation reaction. The CH 4conversion increased with increasing O2/C ratio. Moreover, the CH4 conversion was higher than the equilibrium conversion calculated using the blank outlet temperature for O2/C〉0.42 and reached about 100% at O2/C=0.55. However, the hydrogen concentration decreased for O2/C〉0.45 because hydrogen was combusted to steam in the presence of excess oxygen. On the other hand, the hydrogen and CO2 concentrations increased and the CO concentration decreased with increasing SIC ratio. As a result, it was found that the highest hydrogen concentrations and CH4 conversions were attained at the O2/C ratios of 0.45-0.55 and the SIC ratios of 1.5-2.5. Moreover, the H2/CO ratio could also be controlled in the range from about 2 to 3.5 to give at least 90% CH4 conversion, by regulating the O2/C or S/C ratios.

Low Temperature Catalytic Combustion of Ethanol over Pt/γ-Al_2O_3/Ce_xZr_(1-x)O_2 Honeycomb Catalysts

It has been found that the catalytic activity toward the decomposition of ethanol in a fix bed reactor can be greatly improved by loading Pt on the surface of CexZr1-xO2. In this study, we have investigated the effects of different x of Pt/γ-Al2O3/CexZr1-xO2 on the catalytic activity of catalysts. The prepared catalysts were characterized by BET, XRD, and TPR. The BET surface areas of the catalysts decreased with x decreasing. XRD results reveal that deposited Pt dispersed on the CexZr1-xO2 and γ-Al2O3 matrix. The order of catalytic activities is Pt/γ-Al2O3/ Ce0.5Zr0.5O2〉Pt/γ-Al2O3/Ce0.25Zr0.75O2〉Pt/γ-Al2O3/Ce0.75Zr0.26O2〉Pt/γ-Al2O3/CeO2〉Pt/γ-Al2O3/ZrO2. Among the catalysts, the reduction peak area of Pt/γ-Al2O3/Ce0.5Zr0.5O2 is the largest and the oxygen mobility is noticeably promoted, which is in good harmony with the catalytic activity. Incorporation of ZrO2 into the CeO2 lattice considerably decreases the destruction temperature for ethanol. Based on these observations, the mechanistic role of oxygen mobility in the oxidation reaction has been suggested.

In-situ synthesis of monolithic Cu-Mn-Ce/cordierite catalysts towards VOCs combustion

A monolithic series of Cu-Mn-Ce oxides supported on cordierites with different Cu/Mn/Ce molar ratios were prepared by the in-situ sol-gel method without any binder. The catalysts were characterized by scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS）, X-ray diffraction （XRD）, and Brunauer-Emmett-Teller method （BET） and examined in the catalytic combustion of volatile organic compounds （VOCs）. The results showed that the well-dispersed nanometer particles of mixed oxides adhered firmly to the cordierite surface. Cu0.15Mn0.3Ce55/cordierite was identified as the most active catalyst. Compared with commercial Pd/Al2O3, Cu0.15Mn0.3Ce55/cordierite showed higher activities for the combustion of various types of VOCs, especially for oxy-derivative compounds which could be lighted off below 200 ℃.

In-situ growth of large-area monolithic Fe_(2)O_(3)/TiO_(2) catalysts on flexible Ti mesh for CO oxidation

In this study, we reported the in-situ fabrication of a series of Fe_(2)O_(3)/TiO_(2) monolithic catalysts on flexible Ti mesh via plasma electrolytic oxidation process, hydrothermal reaction and chemical bath deposition(CBD) method. The morphology tailoring of Fe_(2)O_(3) nanostructures finds that Fe2O3 nanosheets supported on TiO2 exhibit superior catalytic performance with a complete oxidation of CO at 260℃. The catalytic stability test indicates that the in-situ grown Fe_(2)O_(3)/TiO_(2) catalysts own outstanding performance for continuous CO oxidation due to the strong substrate adhesion without mass loss. The microstructures and interfaces of Fe_(2)O_(3)/TiO_(2) catalysts are well studied using series of characterization techniques. The in-situ preparation strategy of metal oxide catalysts in this work will open up more opportunities for the rational design of variety of monolithic catalysts used for CO oxidation, de-NO_(x), three-way catalysis and other related application in industry.

Atomic Pt anchored on hierarchically porous monolithic carbon nanowires as high-performance catalyst for liquid hydrogenation

Monolithic catalysts play a crucial role in various catalytic applications,e.g.,chemical synthesis,energy conversion,and environmental treatment,but their catalytic efficiency is often limited by the restricted mass transfer and insufficient exposure of active sites.Herein,we present a dual-templating strategy to fabricate atomic Pt dispersed on monolithic N-doped mesoporous carbon nanowires(Pt_(1)/NMCW)with abundant super-/macropores,which,as monolithic catalyst,exhibits high catalytic performance in hydrogenation of 4-nitrophenol(4-NP).During synthesis,triblock copolymer(Pluronic F127)is employed as a primary soft template to generate the mesoporous structured carbon nanowires to improve the accessibility of Pt single sites;KCl crystallite is used as a secondary hard template to create the super-/macropores,which are beneficial for enhancing the mass transfer efficiency.Thanks to the dual-templating strategy that creates the monolithic carbon nanowires with hierarchically porous structure,the obtained Pt_(1)/NMCW shows highly enhanced catalytic activity in 4-NP hydrogenation,outperforming its analogue synthesized without using KCl as template and being comparable to the nano-powder catalyst(i.e.,atomic Pt loaded on the Ndoped carbon nanospheres,Pt_(1)/NCS).

Remove cooking fume using catalytic combustion over Pt/La-Al_2O_3

Five monolithic catalysts with low noble metal content were prepared by irnmerge method （Pt/γ=Al2O3, Pt/La-Al2O3, Pt/YSZ-AI203, Pt＋Pd/La-Al2O3 and Pd/La-Al2O3） and their activity measurements were carried out in a conventional fixed-bed flow reactor. The results show that La-Al2O3 can promote activity of the prepared catalysts and can decrease the complete conversion temperature of cooking fume. The Pt/La-Al2O3 catalyst has the highest activity and can be applied in wide range of gas hourly space velocity （GHSV）. Some characterizations （XRD, TPR） were carried out with the objective to explain differences in catalytic behaviors. The prepared catalyst showed a great potential for application.

Development of Cu foam-based Ni catalyst for solar thermal reforming of methane with carbon dioxide

Using solar energy to produce syngas via the endothermic reforming of methane has been extensively inves- tigated at the laboratory- and pilot plant-scales as a promising method of storing solar energy. One of the challenges to scaling up this process in a tubular reformer is to improve the reactor＇s performance, which is limited by mass and heat transfer issues. High thermal conductivity Cu foam was therefore used as a sub-strate to improve the catalyst＇s thermal conductivity during solar reforming. We also developed a method to coat the foam with the catalytically active component NiMg3AlOx. The Cu foam-based NiMg3AlOx performs better than catalysts supported on SiSiC foam, which is currently used as a substrate for solar-reforming cat- alysts, at high gas hourly space velocity （≥400,000 mL/（g.h）） or at low reaction temperatures （≤ 720 ℃）. The presence of a γ-Al2O3 intermediate layer improves the adhesion between the catalyst and substrate as well as the catalytic activity.