MCM-41 Catalysts Research Articles

The dual effects of ammonium bisulfate on the selective catalytic reduction of NO with NH3 over Fe2O3-WO3 catalyst confined in MCM-41

Ammonium bisulfate (ABS) has long been considered as a main poisoning material in the selective catalytic reduction by NH3 (NH3-SCR) due to the inevitable coverage of sticky ABS on catalytic active sites in sulfur-containing atmospheres, which severely hinders the achievement of stable and highly active NH3-SCR catalysts. In the present study, we report a novel observation of the dual effects of ABS on the NH3-SCR reaction. That is, ABS inhibits the NH3-SCR performance of Fe2O3-WO3/MCM-41 catalyst at low temperatures (50–200 °C) but shows apparent and sustainable reaction promotion when the temperature surpasses 250 °C. X-ray photoelectron spectroscopy (XPS) and NO probing adsorption confirmed that when ABS is deposited on the catalyst surface, a partial interaction between ABS and the Fe2O3-WO3 component occurs, resulting in blocking of the active sites and an obvious loss of catalytic activity. With increasing reaction temperature, the ammonium in ABS can be facilely consumed by NO/O2, thus inducing the disintegration of poisoning species. The sulfate group transforms into metal sulfate and survives at high temperatures. Importantly, owing to the strong inductive effect of sulfate species, both the acidity and redox properties of the catalyst are greatly improved, which contributes to the enhanced activity. The results of the present study expand our knowledge of the role of ABS in the NH3-SCR reaction and will be useful for designing high-performing NH3-SCR catalysts.

Catalytic performance and debromination of Fe–Ni bimetallic MCM-41 catalyst for the two-stage pyrolysis of waste computer casing plastic

A computer casing plastic waste containing brominated flame retardants (BFRs) was pyrolyzed in a two-stage vertical quartz tube reactor using iron and nickel metals modified MCM-41 catalysts. Various catalysts with different ratios of Fe and Ni were prepared and utilized to study their catalytic performance. At the presence of 20%Ni/MCM-41 catalyst, the pyrolytic yield of oil and gas reached maximum values of 49.9 wt% and 13.8 wt% respectively. The co-existence of Fe and Ni showed synergistic effect on oil composition by promoting the formation of valuable single ring hydrocarbons. With regard to the 15%Fe–5%Ni/MCM-41, 10%Fe–10%Ni/MCM-41 and 5%Fe–15%Ni/MCM-41 catalysts, the production of single ring hydrocarbons were 64.58%, 65.93% and 64.74% respectively. The bimetallic catalysts also exhibited remarkable effect on eliminating bromine from pyrolytic oil. At the presence of Fe–Ni/MCM-41, the bromine in pyrolytic oil was reduced to below 4 wt% compared with 10 wt% without catalyst. Higher amounts of Fe in the catalyst is beneficial for the debromination efficiency. The debromination process by the Fe–Ni/MCM-41 may be realized by these different mechanisms: catalytic cracking of organobromines, reaction of loaded metal oxides with HBr/SbBr3, and deposition of organobromines on the surface of catalyst.

Synergetic Impact of Secondary Metal Oxides of Cr-M/MCM41 Catalyst Nanoparticles for Ethane Oxidative Dehydrogenation Using Carbon Dioxide

Oxidative dehydrogenation of alkanes to alkenes by a mild oxidant such as carbon dioxide is an active area of research. A series of MCM41-supported bimetallic oxide catalysts containing chromium oxide in addition to metal oxides (Ce, Co, Zn, V, Nb, and Mo) has been prepared. The binary catalysts have Cr metal oxide incorporated into MCM41 structure while the other oxides are either incorporated with Cr or impregnated on the MCM41 surface. The synthesized catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 sorption, scanning electron microscopy (SEM), hydrogen temperature programmed reduction (H2-TPR), and Diffuse reflectance UV–vis spectroscopy (DRS). The catalytic activity of Cr(4)-M(4)/MCM-41 catalysts in the dehydrogenation of ethane with CO2 was investigated. The textural properties of the synthesized samples showed that the addition of the bimetallic oxides did not disturb the mesoporous structure of MCM41 and the prepared catalysts exhibited a high BET surface area; however, the lowest surface area was recorded for Cr(4)-Mo(4)/MCM41 catalyst at 701 m2/g. Among the prepared catalysts, H2-TPR profile of Cr(4)-Ce(4)/MCM41 revealed the increase in the concentration of Cr6+ species which interacted with the framework of siliceous support. On the other hand, H2-TPR profiles of Cr(4)-Co(4)/MCM41 showed wide reduction peaks centered at 400 °C which is ascribed to reduction of Cr6+ to Cr3+ species and Co3O4 to metallic Co. At the same time, Cr(4)-Mo(4)/MCM41 and Cr(4)-V(4)/MCM41 exhibited higher temperature reduction peaks, indicating these two catalysts require higher activation temperatures. The synergy between the Cr with Zn or Nb metals reduced the concentration of Cr6+ species which is reflected in their catalytic performance. Cr(4)-Ce(4)/MCM41 recorded the highest catalytic activity toward ethylene production where the ethane conversion and ethylene yield were 37.9% and 35.1%, respectively.

Catalytic Activity and Kinetic Modeling of Various Modules HZMS-5 and Treated MCM-41 Catalysts, for the Liquid-Phase Ketalization of Glycerol With Acetone.

Studies of the Ketalization reaction using trivalent alcohol glycerol in combination with acetone and their kinetics modeling are still limited. The focus of this current study is an investigation into HZSM-5 with various silica to alumina molar ratios (M = 35, 90, and 160) for the reaction between glycerol and acetone. In addition, the influence of reaction temperatures (25, 50, and 60°C) on the rate of the reaction have also been considered. Additionally, this investigation established the rate law for all HZMS-5 models (M = 35, 90, and 160) which showed “n” order equals half while the activation energy was found to be 164.34 kJ mol−1 with a constant reaction rate of k0 = 5.2678*1028 (Concentration1/2. min-1). Furthermore, MCM-41 pure mesoporous materials were separately treated using various methods. The first involved treatment using Dichlorodimethylsilane MCM 41(TD) and later treatment of a pure sample with sulfuric acid MCM-41. The sulfated MCM-41 sample (MCM41-SU) showed that reaction order equals n = −1 and a rate constant of (k) = 3.9 × 102 (Concentration−2. min−1). A close correlation and agreement was found between the experimental modeling and the theory. Additionally, this current kinetic study showed that water production has no effect on the conversion activity within 10 min from the start of reaction. Besides, further kinetics investigations were performed to ascertain the estimated time for water production based on the conditions applied during the reaction system. It resulted in an average time of 3 min for equilibrium to be reached in the reaction system. It was found that the estimated reaction equilibrium time (teq) is within the range from zero to 10 min in agreement with the proposed kinetic model in this work. Finally, it was also observed that a low equilibrium conversion (XAeq) had been obtained in the present work about 0.42 (42%). At a reaction temperature of 60°C (333.15 K) and at one atmosphere, the acetone was shown to exert a vapor pressure of about 113.737 mm Hg. Hence, the overall order of the reaction was determined by the method of initial rates. Similarly, in order to ascertain the dispersion of aluminum, together with its distribution on the surface of a catalyst for a zeolite that has varying molar ratios of silica to alumina as is the case for example with ZSM-5 (35), a mathematical approach is proposed in this study for its calculation.

Catalytic fast co-pyrolysis of waste greenhouse plastic films and rice husk using hierarchical micro-mesoporous composite molecular sieve

Catalytic fast co-pyrolysis of waste greenhouse plastic films and rice husk over a hierarchical HZSM-5/MCM-41 catalyst was performed in an analytical Py-GC/MS. We evaluated the effect of pyrolysis temperature and the ratio of rice husk to waste greenhouse plastic films on the total peak area of condensable organic products and CO2. In order to evaluate synergy possibilities among the two feedstocks, we performed non-catalytic pyrolysis and catalytic fast pyrolysis of rice husk and waste greenhouse plastic films separately. In addition, we report results for the catalytic fast co-pyrolysis of the mixture rice husk and waste greenhouse plastic films. The maximum relative content of hydrocarbons from catalytic fast co-pyrolysis of rice husk and waste greenhouse plastic films is obtained at 600 °C. When the mass ratio of rice husk to waste greenhouse plastic films is 1:1.5, the relative content of hydrocarbons reaches a maximum (71.1%). The hierarchical micro-mesoporous composite molecular sieve used in this work has outstanding catalytic activity and increases the relative content of hydrocarbons.

A study on the performance of coke resistive cerium modified zeolite Y catalyst for the pyrolysis of scrap tyres in a two-stage fixed bed reactor

Catalytic pyrolysis is a useful technique for the conversion of scrap tyres into liquid fuels. Zeolite catalysts were employed in the pyrolysis of scrap tyres for the production of aromatic rich fuel. Deactivation of zeolite catalysts during pyrolysis reaction was investigated which played an important role in the product quality and composition. Herein, the performance of microporous zeolite catalysts and mesoporous MCM-41 catalyst was evaluated in a two-stage fixed bed reactor for the pyrolysis of scrap tyres. Comparative studies showed the increase in the production of aromatic compounds up to 23.7% over zeolite catalyst as compared to 18.7% over MCM-41 catalyst. However, Zeolite Y catalyst exhibited higher coke formation led to the rapid deactivation. The stability of zeolite catalysts is addressed by the incorporation of Cerium metal within the framework of two zeolite catalysts namely Zeolite Y and ZSM-5 through the ion-exchange technique. Parent and spent catalysts were characterised using synchrotron FT-IR spectroscopy, temperature-programmed desorption of ammonia (NH3-TPD), N2 Physisorption, scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), energy-dispersive X-ray spectroscopy (EDX), and hydrogen temperature-programmed reduction (H2-TPD). A higher percentage of aromatics were produced over the large pore Zeolite Y. Cerium ion-exchange decreased the formation of coke from 8.1% to 5.7% over submicron and large pore Zeolite Y catalyst. Moreover, naphthalene production decreased over both Ce-Zeolite Y and Ce-ZSM-5.

Quantitative Relationship Between Activity and Acid Site Distribution in the Oligomerization of Ethylene Over MCM-41 Catalyst

Nickel ion exchanged MCM-41 samples with different Si/Al ratios and Ni-ZSM-5/MCM-41 were prepared and used to catalyze ethylene oligomerization which was performed in a fixed bed model (T = 523 K, P = 2 MPa). A temperature programmed desorption of ammonia (NH3-TPD) method was employed to quantitatively determine the acid strength distribution of Ni-MCM-41 samples with different Si/Al ratios and Ni-ZSM-5/MCM-41. The TPD spectrum was analyzed by an interrupted-TPD method with desorption-control (dc-method) to obtain the desorption activation energy of ammonia, which can be used as acid strength scale for the purpose of correlation with catalytic activity. A quantitative relationship between catalyst acidity and catalytic activity was established by a Bronsted type equation. The site with desorption activation energy of ammonia E = 124 kJ mol−1 was found as the most suitable site for ethylene oligomerization. An approximate linear relationship is obtained between the activity of the ethylene oligomerization reaction and the acid amount corresponding to the acid site with E = 124 kJ mol−1.

Amine-based CO2 capture aided by acid-basic bifunctional catalyst: Advancement of amine regeneration using metal modified MCM-41

The most critical challenge for the industrial implementation of amine solution CO2 capture is the high heat duty of rich solvent thermal regeneration. Despite significant efforts to lower energy consumption, including employing new amine solvents and process intensification, a novel approach of overcoming this challenge is still demanded. Here, we introduce a novel acid-basic bifunctional catalyst system to reducing the regeneration heat duty by adding metal modified MCM-41 catalyst into amine-based solution. MCM-41 was modified with three metals (Fe, Al, Mo) as well as with different Fe content for catalysis of the rich monoethanolamine (MEA) solvent regeneration process at 98 °C. Results reveal that all the catalysts accelerated regeneration process, and Fe2O3 modified MCM-41 (MFe) catalysts exhibited superior catalytic performance. Notably, the addition of MFe greatly improved the CO2 desorption performance (desorption factor) to 206.3–337.1% compared to the catalyst-free run. The excellent catalytic performance of MFe is ascribed to its improved Brϕnsted acid sites and increased basic sites. Additionally, MFe showed good cyclic stability and its use in the regeneration process enhanced the subsequent CO2 absorption performance. Furthermore, a plausible dual sites mechanism of catalytic amine solvent regeneration over MFe was proposed. Our results demonstrate that the acid-basic bifunctional catalyst plays significant role in developing the amine-based post-combustion CO2 capture technology and has important promise for real-world application.

Influence of process parameters on single bed Ni/(Al)MCM-41 for the production of propene from ethene feedstock

A Ni aluminized mesoporous MCM-41 catalyst was prepared and applied for the direct conversion of ethene to propene. Suitable ethene conversion and good selectivity for the desired molecule propene were achieved. The catalyst placed in a packed tubular reactor was stable for more than 2000 h with time on stream. A reaction network analysis was performed evaluating the product spectrum observed covering a large range of operating conditions. Thereby, temperature and feed concentration can be considered as significant influence parameters on the product distribution. Based on the product spectra, a modified reaction network including a catalytic cycle is suggested, which adds cracking of long-chain olefins to the conventionally considered dimerization/oligomerization and isomerization steps. Following previous publications, the catalyst presented strong deactivation behavior. It was observed that the regeneration conditions (oxygen concentration and regeneration time) are crucial parameters concerning long-time stability. Finally, a cycling reactor operation of deactivation-regeneration steps is suggested.

Synergistic effects of bimetallic PtRu/MCM-41 nanocatalysts for glycerol oxidation in base-free medium: Structure and electronic coupling dependent activity

Bimetallic PtRu catalyst was first reported for oxidation of glycerol to glyceric acid in base-free medium using O2 as the oxidant. A combination of density functional theory (DFT) calculations and multi-characterizations (e.g., H2-TPR, HAADF-STEM and XPS) revealed that the strong interaction between Pt and Ru could promote the dispersion of PtRu alloy nanoparticles and enhance the electronic coupling effect on the metal surface. Meanwhile, compared to the monometallic Pt catalyst, the introduction of Ru contributes to the direct dissociation of molecular oxygen and water to hydroxyl group, leading to the excellent catalytic activity. A volcanic-shaped relationship between Ru/Pt ratio, catalytic performance, structure-sensitivity and electronic coupling effect was systematically established. Furthermore, the role of structure-sensitivity and electronic coupling effect for the enhanced catalytic activity of PtRu catalysts with different Ru/Pt ratios are distinguished in detail. Finally, the Pt0.8Ru0.8/MCM-41 catalyst showed excellent catalytic activity (TOF: 823.9 h−1), glyceric acid selectivity (80.1%) and stability (recycling for 5th) under the optimized conditions (80 °C, 1 MPa O2 and 12 h). The insights and methodology reported here may pave the way to the rational design of bimetallic catalysts for efficient conversion of bio-derived substrates under mild conditions.

Role of water in cyclopentanone self-condensation reaction catalyzed by MCM-41 functionalized with sulfonic acid groups

Water is ubiquitous in many catalytic reactions used in the upgrading of biomass. Therefore, quantifying and controlling the influence of water in activity, selectivity, and catalyst deactivation is essential for advancing this technology. Here, we report a kinetic study of the cyclopentanone self-condensation over functionalized MCM-41 catalysts with varying acid densities and in the presence of controlled amounts of water. It is observed that small amounts of water enhance the activity of these catalysts. A detailed analysis of the experimental data indicates that the rate limiting step is the enol formed via protonation and tautomerization of a cyclopentanone molecule attacks the electrophilic carbon of a second carbonyl. On catalyst with high density of sulfonic acid groups, the best fitting of the experimental data is obtained with a kinetic model in which the CC bond forming step mostly occurs with the second carbonyl molecule adsorbed (and polarized) by an adjacent acid site (Langmuir-Hinshelwood, L-H). By contrast, at a lower density of sulfonic acid groups, the number of active sites with enough proximity greatly decreases and the CC bond forming occurs with the second carbonyl in the liquid phase (Eley-Rideal, E-R). In this case, it is observed that when water is added to the reaction mixture, the best description of the kinetics switches from E-R to L-H. Evidently, the water can help bridging active sites remotely located on the surface, extending the polarizing effect of the second acid site.

Role of TiO2 nanoparticle modification of Cr/MCM41 catalyst to enhance Cr-support interaction for oxidative dehydrogenation of ethane with carbon dioxide

Mesoporous silica (MCM41) is modified with TiO2 nanoparticles by solvolysis of titanium precursor to prepare a series of Ti(x)/MCM41 supports with different titanium contents for chromium based catalytic system. Incipient wetness impregnation method is used to introduce the chromium species to produce a series of Cr(y)/Ti(x)/MCM41 catalysts with different chromium contents. The effect of both titanium and chromium loading on the catalytic performance of Cr(y)/Ti(x)/MCM41catalysts for the oxidative dehydrogenation of ethane with CO2 was investigated. The prepared catalysts were characterized by XRD, TEM, SEM, EDX-elemental mapping, N2 sorption analysis, ICP, UV–vis-DSR, XPS and TPR-H2 techniques. The results show that modification of MCM41 with TiO2 nanoparticles altered the structural properties of the synthesized catalyst, such as, chromium species dispersion and size as well as the chromium-support interaction which in turn affect the catalytic performance of synthesized catalysts. Among the modified support catalysts, the Ti(1.9)/MCM41 has enhanced the concentration and stability of Cr6+ species and resulted in comparable amounts of surface reducible chromium species. The results have revealed that the highest catalytic activity is obtained for Cr-loaded TiO2-modified MCM41 containing 1.9 wt% titanium and 8 wt% chromium. It showed superior performance for ethane dehydrogenation with CO2 at 700 °C at 51.87% ethane conversion, and 48.14 and 92.80% ethylene yield and selectivity, respectively.

Study on syngas methanation mechanism over Ni4/MCM-41 catalyst based on density functional theory

The density functional theory method is employed to systematically explore the mechanism of syngas methanation on the Ni4/MCM-41 catalyst surface. The calculation results show that the optimal pathway of CH4 formation is CO + H → CHO + H → CH2O + H → CH3O → CH3 + H → CH4 with the rate-determining step of CH3O direct dissociation. Because the activation energy for the direct dissociation of CH3O species is much lower than that for the CH3OH formation (198.6 vs 264.8 kJ mol−1), there is almost no by-product CH3OH that appeared in the products of the syngas methanation over the Ni4/MCM-41 catalyst. Compared with other conventional nickel-based methanation catalysts, Ni4/MCM-41 catalyst is an excellent methanation catalyst with high selectivity of CH4.

Mechanism of Synergistic Effect on Electron Transfer over Co-Ce/MCM-48 during Ozonation of Pharmaceuticals in Water.

The same amount of metal was deposited on the surface of three-dimensional mesoporous MCM-48 by a facile impregnation-calcination method for catalytic ozonation of pharmaceutical and personal-care products in the liquid phase. At 120 min reaction time, Co/MCM-48 and Ce/MCM-48 showed 46.6 and 63.8% mineralization for clofibric acid (CA) degradation, respectively. Less than 33% mineralization was achieved with Co/MCM-48 and Ce/MCM-48 during sulfamethazine (SMZ) ozonation. In the presence of monometallic oxides modified MCM-48 catalysts, total organic carbon (TOC) removal of diclofenac sodium (DCF) was around 80%. The composite Co-Ce/MCM-48 catalyst exhibited significantly higher activity in terms of TOC removal of CA (83.6%), SMZ (51.7%) and DCF (86.8%). Co-Ce/MCM-48 inhibited efficiently the accumulation of small molecular carboxyl acids during ozonation. A detailed research was conducted to detect the nature of material structure and mechanism of catalytic ozonation by using a series of characterizations. The main reaction pathway of CA was determined by the analysis of liquid chromatography-mass spectrometry, in line with the results of frontier electron density calculations that reactive oxygen species (ROSs) were easy to attack negative regions of pharmaceuticals. The Si-O-Si, Co···HO-Si-O-Si-OH···Ce, and O3···Co-HO-Si-O-Si-OH···Ce-OH···O3 basic units in catalysts were constructed to detect the orbit-energy-level difference. The results revealed that a synergistic effect existed at the interface between cobalt and cerium oxides over MCM-48, which facilitated the ROSs sequence in solution with ozone. Therefore, the multivalence redox coupling of Ce4+/Ce3+ and Co3+/Co2+ along with electron transfer played an important role in catalytic ozonation process.

Microwave-assisted co-pyrolysis of lignin and waste oil catalyzed by hierarchical ZSM-5/MCM-41 catalyst to produce aromatic hydrocarbons

Microwave-assisted catalytic fast co-pyrolysis (MACFP) of lignin and waste oil with SiC as microwave absorbent and hierarchical ZSM-5/MCM-41 as catalyst were implemented in a microwave-induced reactor. ZSM-5/MCM-41 is a kind of composite catalyst with MCM-41 as shell and ZSM as core. The effects of catalyst temperature, the ratio of feedstock-to-catalyst and the ratio of two reactants (lignin and waste oil) on product distribution and yield were studied. The study shows that catalytic co-pyrolysis is a complex reaction process, and many reaction conditions could affect the final reaction results. The optimum reaction conditions are as follows: catalytic temperature 400 °C, the feedstock-to-catalyst ratio of 10:1 and the ratio of lignin to waste oil of 2:1. Under this reaction condition, the conversion of feedstocks reached 76.00%, the proportion of aromatics was 50.31% and the selectivity of monocyclic aromatic hydrocarbons (MAHs) was 42.83%.

Molecular Insights on the Role of (CTA+)(SiO−) Ion Pair into the Catalytic Activity of [CTA+]–Si–MCM-41

In this work, a theoretical study in conjunction with a spectroscopic analysis by FTIR were carried out in order to obtain molecular insights on the role of (CTA+)(≡SiO−) ion pair into the catalytic activity of [CTA+]–Si–MCM-41, the non-calcined form of Si–MCM-41. The reaction of transesterification of ethyl acetate with methanol was used as a model of transesterification of vegetal oils using the mesoporous heterogeneous catalyst. The theoretical study was performed in the framework of density functional theory (DFT) in order to provide new insights that could be helpful in the understanding of these chemical reactions on solid surfaces. It is found that the most favorable reaction mechanism is the dual site mechanism and that the presence of the (CTA+)(≡SiO−) ionic pair is fundamental for the catalytic activity. The basic center of [CTA+]–Si–MCM-41 catalyst polarizes the adsorbed methanol and the acid center polarizes the carbonyl of adsorbed ethyl acetate. Thus, this bifunctional catalytic site makes possible the concerted adsorption of both reactants at the pore mouth and generates a concerted transition state that gives rise to the beginning of the transesterification reaction and the formation of the unstable tetrahedral intermediate which will give rise to the products.

Degradation of lignin catalyzed by nanochannels solid acids in ionic liquid

Acid treated mesoporous MCM-41 molecular sieves were adopted as catalysts for degradation of lignin dissolved in ionic liquid. On one hand, the acid sites doped the nanochannels activate lignin macromolecules to conduct degradation reaction, on the other hand, the confined spaces are benefit for restricting the repolymerization of the degraded lignin fragments. The AMCM-41s catalyst was found to be the best species for lignin degradation in 1-methyl-3-benzylimidazolium chloride (BnMIMCl) within the domain of present study. The efficiency of lignin degradation was increased to 74.02% under the optimal conditions. Meanwhile, over 80% of the liquid products were tested as phenols. The surface area, pore sizes and their distribution as well as the acidity of the acidified MCM-41 catalysts were analyzed, which were properly interconnected with the lignin degradation efficiency. This work contributes a degradation process for lignin in homogeneous solution under heterogeneous catalytic process, which is promising for obtaining phenols from lignin with the aid of green solvent. Furthermore, the recycled solid residues were fully transferred into activated carbon with excellent adsorption property for methylene blue and iodine.

Reducing Energy Penalty of CO2 Capture Using Fe Promoted SO42-/ZrO2/MCM-41 Catalyst.

The high energy consumption of CO2-loaded solvent regeneration is the biggest impediment for the real application of the amine-based CO2 capture process. To lower the energy requirement, three Fe promoted SO42-/ZrO2 supported on MCM-41 (SZMF) catalysts with different iron oxide content (5%, 10%, and 15%) were synthesized and applied for the rich monoethanolamine solution regeneration process at 98 °C. Results reveal that the use of SZMF hugely enhanced the CO2 desorption performances (i.e., desorption factor) by 260-388% and reduced the heat duty by about 28-40%, which is better than most of the reported catalysts for this purpose. The eminent catalytic activities of SZMF are related to their enhanced ratio of Brønsted to Lewis acid sites, weak acid sites, basic sites, and high dispersed Fe3+ species. Meanwhile, the addition of SZMF for CO2 desorption shows a promotional effect on its CO2 absorption performance, and SZMF presents an excellent cyclic stability. A possible mechanism is suggested for the SZMF catalyzed CO2 desorption process. Results of this work may provide direction for future research and rational design of more efficient catalysts for this potential catalyst-aided CO2 desorption technology.

Catalytic liquefaction of switchgrass in isobutanol/water system for bio-oil development over bifunctional Ni-HPMo/Fe3O4@Al-MCM-41 catalysts

A bifunctional Ni-HPMo/Fe3O4@Al-MCM-41 catalyst was prepared by impregnation method and used for the liquefaction of switchgrass in isobutanol/water mixed solvents. It was found that the introduction of Al species into MCM-41 could improve its catalytic performance of catalyst by enhancing the acidity and stability of mesoporous silica. The grafting of HPMo onto the Al-MCM-41 materials not only greatly increased the acidity but also enhanced the acid strength, with an optimal HPMo loading amount in the catalyst of 20 wt%. There was a clear effect of the catalyst on product yield and quality. A switchgrass conversion of 84.7% and a liquid yield of 55.0% could be obtained under the optimal conditions. Reuse of the catalyst indicated that it had a stable catalytic activity. Furthermore, the results showed that the isobutanol/water system was an efficient solvent for switchgrass liquefaction as well as the separation of higher heating value isobutanol phase products and lower heating value water phase products from the liquefaction mixture. This work thus offers an effective approach to improve the product yields and quality in biomass liquefaction by using metal-heteropolyacid bifunctional catalysts.

Oxidative dehydrogenation of ethylbenzene to styrene over the CoFe2O4–MCM-41 catalyst: preferential adsorption on the O2−Fe3+O2− sites located at octahedral positions

The present study describes the catalytic performance of cobalt ferrite supported on MCM-41 for the oxidative dehydrogenation of ethylbenzene.