Acidity Of Catalysts Research Articles

Hydrogen-free carbon monoxide production through decomposition of formic acid over a HPW/TiO2 catalyst

The dehydration of formic acid over supported phosphotungstic acid (H3PW12O40, HPW) catalysts was investigated for the production of hydrogen-free carbon monoxide (CO). The variations in the support type (SiO2, Al2O3, ZrO2, and TiO2) and HPW content (0.0–20.0 wt.%) affect the acidity of catalysts, which was demonstrated by the temperature-programed desorption of iso-propanol (IPA-TPD) and pyridine-adsorbed infrared spectroscopy (Py-IR). The catalytic activity in formic acid dehydration exhibited a volcano-type distribution in accordance with the HPW content and was maximized at 15 wt.% loading. Furthermore, the catalytic activity was more closely related to the density of Brønsted acids than that of Lewis acids and inversely proportional to the peak temperature of propylene desorption during IPA-TPD. The strongly adsorbed H2O on the catalysts, which is generated during formic acid dehydration, induces deactivation of the catalyst, particularly at lower reaction temperatures (<230 °C).

Para-xylene production from toluene methylation: Novel catalyst synthesis, fabrication and ANFIS modelling

BackgroundToluene methylation to p-xylene is a key reaction in the petrochemical industry, with p-xylene being an important feedstock for the manufacturing of many chemical commodities. MethodsThe present contribution reports the synthesise of Al-HMS industrial catalysts with different Si/Al ratios and H-ZSM-11 industrial catalysts with surface modification (SM-H-ZSM-11). The properties of the catalysts were characterized by X-ray crystallography (XRD), scanning electron microscope (SEM), thermogravimetric Analysis (TGA), Fourier-transform infrared spectroscopy (FTIR) of pyridine adsorption, and NH3 TPD. catalytic performances were evaluated for the toluene methylation with methanol by assessing the effects of temperature, pore size, acidic strength, and residence time of reactants on the shape-selectivity of the product. Significant findingThe results show that whilst an increase in pore size has an unfavorable impact on the shape selectivity of p-xylene, an increase in the strength of the acid site enhances the shape selectivity of p-xylene, hence counterbalancing the effect of pore size. In particular, Al-HMS-5 has a larger pore size than that of H-ZSM-11 but the stronger acidity of Al-HMS-5 is more effective on the shape selectivity of the catalyst. Beside experimental studies, a computational process modelling was carried out to estimate percentage of toluene conversion as a function of the reaction temperature (K), WHSV (h−1), toluene/MeOH molar ratio, acidity of catalyst (mmol/g), and surface area (m2/g) using an adaptive neuro-fuzzy inference system optimized by a particle swarm optimization algorithm. Excellent agreement between measured and predicted toluene conversion confirmed the satisfactory performance of our model. The results show that by suitable tuning of catalyst acidity it is possible to retain high selectivity whilst increasing pore size, hence alleviating potential problems due to diffusion limitation in small pores. The relevancy factor calculated for reaction temperature, WHSV, acidity, and BET surface area of the catalysts were1.35, 0.096, 0.0071, and 10.42, respectively, which shows that highest sensitivity of toluene methylation relates to BET surface area of the catalysts.

Selective hydrodeoxygenation of guaiacol to cyclohexanol over core-shell Cox@C@Ni catalysts under mild condition

Guaiacol, a typical lignin-derived phenolic compound, can be converted to high value-added cyclohexanol through hydrodeoxygenation (HDO). In this work, a series of core-shell Cox@C@Ni catalysts were prepared via two-step hydrothermal and calcination treatments, and applied to catalyze guaiacol to cyclohexanol. Compared with Co@C catalyst, core-shell Cox@C@Ni catalysts exhibited much better catalytic performance. Almost 100% guaiacol conversion and 90% cyclohexanol selectivity were achieved over Co1.2@C@Ni catalyst at 220 °C, 0 MPa N2 for 2 h using isopropanol as H-donor solvent, which was carried out under much milder conditions compared with previous research. The structure feature of core-shell Cox@C@Ni catalysts were analyzed by BET, XRD, SEM, TEM, HRTEM, etc. The catalyst compositions and acidities played a significant role on hydrodeoxygenation of guaiacol via ICP and NH3-TPD analysis. The influences of reaction temperature, reaction time and initial nitrogen pressure were also investigated to explore the optimal reaction condition. Moreover, the possible reaction pathways and reaction mechanism was deduced based on the product distributions and physicochemical properties.

Influence of Lewis and Brønsted acid catalysts in the transformation of hexoses into 5-ethoxymethylfurfural

Several sulfonated polymers, which are typical Brønsted acid catalysts, have been employed in the production of two biofuels: 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) as main byproduct, and the catalytic results have been attributed to their different chemical and morphological properties. The Purolite CT275DR attained the best results from 5-hydroxymethylfurfural (HMF) with a 63% EMF yield after 16 h at 100 °C thanks to their more abundant superficial acid sites. Moreover, Purolite CT275DR was able to efficiently dehydrate and etherify fructose, with a total EMF plus EL yield of 65% after 24 h at 100 °C. When glucose or galactose were used as feedstock, alumina was utilized to provide Lewis acid sites, necessary for the transformation of aldoses in solution enabling a combined biofuel yield (EMF plus EL) of 40% from glucose after 24 h at 140 °C. With the study of the role of each catalyst, both Brønsted and Lewis acid catalysts (resin and alumina, respectively) were required to obtain considerable EMF yields from aldoses. The reutilization of the catalysts employed for 5 catalytic runs demonstrated that Purolite CT275DR suffers no appreciable loss of activity, but alumina showed progressive losses in activity in each cycle due to carbonaceous deposits and catalyst loss.

Dimethyl Ether to Olefins on Hybrid Intergrowth Structure Zeolites

A series of catalysts based on hybrid intergrowth structure zeolites MFI-MEL, MFI-MTW, and MFI-MCM-41 are studied in the reaction of olefins synthesis from dimethyl ether at atmospheric pressure and a temperature of 340 °C. The total acidity of hybrid zeolite-based catalysts is shown to correlate with their activity. However, the use of zeolite with the structure MFI-MCM-41, which is characterized by a high content of medium acid sites, additionally catalyzes the methanol dehydration reaction, resulting in a decrease in the observed DME conversion. The obtained product distributions are brought into correlation with the texture of catalysts. It is shown that the use of hybrid zeolites does not change the mechanism of reaction, but the structural features of zeolites influence the priority of the competing MTO reactions: high ethylene yield is observed for catalysts with high micropore volume. The topology of the hybrid zeolite has been shown to influence the hydrogen transfer reaction rate, but not to change the isomerizing activity of the catalyst.

Poisoning mechanism of different Cd precursors on Fe-Ce/TiO2 catalyst for selective catalytic reduction of NOx with NH3

As one of the most harmful heavy metals, Cd can present in many chemical forms in real flue gas and may deactivate the SCR catalysts, but the poisoning mechanism of different Cd species over the Fe-Ce/TiO2 catalysts remains unclear. Therefore, in our work, Fe-Ce/TiO2 catalyst is prepared and doped with Cd(NO3)2, CdCl2, and CdSO4, respectively, aiming to investigate the effect of different Cd precursors on the catalytic performance, physicochemical properties, and poisoning mechanisms of Fe-Ce/TiO2 catalyst. The results demonstrate that different Cd precursors exert different influences on the catalytic activity of the catalyst and the deactivation sequence is CdSO4 <Cd(NO3)2 <CdCl2. The doping of Cd decreases the specific surface area, promotes the grain growth of active species, and results in the aggregation of surface active species to varying degrees. Although the total H2 consumption of Cd poisoned catalysts is enhanced, they are not originated from more amounts of surface active species and thus it does not contribute to the redox cycles and catalytic activity of catalysts. The doping of Cd(NO3)2 decreases the surface acidity of catalysts, while CdCl2 and CdSO4 promote surface acidity, but the adsorbed NH3 over CdCl2 poisoned catalyst is unreactive. In addition, both Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms are involved in the SCR reaction over the Fe-Ce/TiO2 catalyst and different Cd poisoning makes no change to the reaction mechanism.

B-Axis-Oriented ZSM-5 Nanosheets for Efficient Alkylation of Benzene with Methanol: Synergy of Acid Sites and Diffusion

ZSM-5 nanosheets are promising catalysts for the catalytic reactions controlled by diffusion limitations. This study reveals its significant application in the alkylation of benzene with methanol. The b-axis-oriented ZSM-5 nanosheets with similar acid property but varied thicknesses of about 30, 90, and 300 nm were prepared to investigate the effect of thickness on their catalytic properties for alkylation reactions. Comparative results demonstrate that the sample with a thickness of 30 nm exhibits higher benzene conversion, xylene selectivity, and methyl selectivity (up to 97%), accompanied by an ultralong lifetime (up to 1000 h, 10 times longer than that of the sample with a thickness of 300 nm) and lower byproduct ethylbenzene selectivity. This is ascribed to the shortened straight channel length, increased specific surface area, and enlarged mesopore volume that significantly facilitate the diffusion of reactants and products, increase the accessibility of acid sites, and decrease the coke formation. Moreover, compared with conventional ZSM-5 nanocrystals, ZSM-5 nanosheets deliver a substantially extended lifetime due to fewer framework defects. Most significantly, this study unravels the diffusion effect on ethylbenzene selectivity over ZSM-5 nanosheets with different thicknesses and illustrates the role of strong Brønsted acid sites in the dynamic changes of ethylbenzene selectivity. In light of the above analysis, we developed a precoking strategy and an introducing-heteroatom strategy to precisely tailor the catalyst acidity, further suppressing the ethylbenzene formation (<0.3%) while maintaining long-term stable operation (>300 h).

Synergetic metal-Nx and metal nanoparticles derived from Zn/Co-zeolitic imidazolate frameworks boosted conversion of microalgal lipids

In order to enhance acid-base active sites and their utilization efficiency to efficiently convert microalgal lipids into biodiesel, an acid-base catalyst was synthesized through pyrolyzing ZnCo bimetallic zeolitic imidazolate frameworks (ZIFs). Pyrolysis destroyed saturated coordinated metal-N4 sites in ZIFs and produced more unsaturated metal-Nx and metal nanoparticles, which enhanced Lewis acidity. The increased pyridinic N and unsaturated metal-Nx promoted Lewis basicity. Meanwhile, Zn doping reduced sizes of catalyst crystals and metal nanoparticles, which improved utilization efficiency of active sites. Hence, compared with pyrolyzed ZIF-67, the acidity of optimal catalyst increased from 0.205 to 1.535 mmol/g, whereas basicity increased from 0.069 to 0.405 mmol/g. DFT calculations revealed that catalytic performances of metal nanoparticles and unsaturated metal-Nx were better than that of saturated metal-N4. Therefore, the catalytic efficiency of C-Zn/Co-ZIF = 4 (molar ratio of Zn to Co was 4) catalyst was highest at 96.2%, because of the minimal catalyst crystals and metal nanoparticles.

High Activity and Selectivity towards Ethyl Methyl Carbonate through Optimizing Surface Acidity and Alkalinity of the Transesterification Catalyst

AbstractEthyl methyl carbonate (EMC) is the product of the partial transesterification of dimethyl carbonate (DMC) with ethanol (EtOH). How to modulate the catalyst with suitable acidity and alkalinity is of key importance for achieving both high activity and selectivity toward EMC. Herein, an Mg−Zn−P/AT‐ZSM‐5 catalyst with moderate basicity and moderate acidity was intelligently designed by the co‐doping of Mg−Zn−P after the desilication of ZSM‐5. Under the optimized reaction conditions, the EtOH conversion can reach 99.1 % with a high EMC selectivity of 96.3 %. Based on the results of multiple characterizations, the enhanced EtOH conversion and high EMC selectivity should be attributed to the well dispersed supported metal species, and enhanced metal‐support interactions, especially the suitable surface acidity and alkalinity property of the catalyst. Such work provides a more reasonable design strategy for the preparation of a catalyst used for the transesterification reaction of DMC and EtOH to selectively produce high‐valued EMC.

Preparation of 5-(Acyloxymethyl)furfurals from Carbohydrates Using Zinc Chloride/Acetic Acid Catalyst System and Their Synthetic Value Addition.

5-(Acyloxymethyl)furfurals (AMFs) have received considerable attention as hydrophobic, stable, and halogen-free congeners of 5-(hydroxymethyl)furfural (HMF) for synthesizing biofuels and biochemicals. In this work, AMFs have been prepared directly from carbohydrates in satisfactory yields using the combination of ZnCl2 as the Lewis acid catalyst and carboxylic acid as the Brønsted acid catalyst. The process was initially optimized for 5-(acetoxymethyl)furfural (AcMF) and then extended to producing other AMFs. The effects of reaction temperature, duration, loading of the substrate, and dosage of ZnCl2 on AcMF yield were explored. Fructose and glucose provided AcMF in 80% and 60% isolated yield, respectively, under optimized parameters (5 wt % substrate, AcOH, 4 equiv ZnCl2, 100 °C, 6 h). Finally, AcMF was converted into high-value chemicals, such as 5-(hydroxymethyl)furfural, 2,5-bis(hydroxymethyl)furan, 2,5-diformylfuran, levulinic acid, and 2,5-furandicarboxylic acid in satisfactory yields to demonstrate the synthetic versatility of AMFs as carbohydrate-derived renewable chemical platforms.

CO2 or Carbonates – What is the Active Species in Electrochemical CO2 Reduction over Fe‐Porphyrin?

AbstractCO2 reduction is typically performed at neutral pH. Under these conditions CO2 is in equilibrium with H2CO3, HCO3− and CO32−. However, despite their presence so far most studies solely focus on the contribution of CO2 while carbonate species as alternative reactants are generally neglected. Using density functional theory (DFT) modelling we explore the possible contribution of these carbonate species to the overall CO2 reduction activity for a Fe porphyrin model catalyst. Considering only reaction Gibbs free energies, we find the reduction of carbonic acid (H2CO3), bicarbonate (HCO3−) and CO2 to be equally likely. However, owing to a very high activation barrier for the initial adsorption of CO2 onto the catalyst, bicarbonate and carbonic acid reduction are found to be several orders of magnitude faster. These data are used to model the pH dependence of the reaction rates of the different reactants. These results confirm that carbonic acid and bicarbonate are the most likely reactants independent of the pH and reactor setup.

Comparative First-Principles Study on Tetravalent Ion-Incorporated MTW-Type Zeolites

The density functional theory (DFT) with dispersion correction was used to study the tetravalent metal (Ti, Zr, Ge, Sn)-incorporated MTW-type (Mobil-TWelve) zeolites that are usually denoted as ZSM-12 (Zeolite Socony Mobil-twelve). Their stability, Lewis acidity, and structural properties were analyzed with periodic models. The calculated substitution energies indicate that Ti and Zr are more easily incorporated into MTW than Ge and Sn. The most stable substitution energies of four elements correlate with their covalent radii (R2 = 0.95), implying that the thermodynamics of incorporation process could be designed by covalent radii. Incorporations of a tetravalent metal result in the variation of cell volume due to their larger covalent radii; significantly, there is a good correlation between substitution energies and cell volume, indicating that the stability could be judged by the cell volume from accessible characterization. The Lewis acidity is measured by ammonia adsorption as follows: Sn-MTW > Zr-MTW > Ti-MTW > Ge-MTW. This finding provides the basis of theoretical Lewis acidity and agrees with previous experiments. In addition, the structural deformation has a great influence on the zeolitic stability, proved by two correlations: (1) relative mean square deviation of [MO4] and substitution energy of Ti-, Ge-, and Sn-MTW and (2) root-mean-square error of [MSi4] and substitution energy of Zr-MTW. Our work provides the theoretical basis for the preparation and Lewis acidity of tetravalent metal-incorporated MTW-type zeolitic catalysts.

A molecular kinetic model incorporating catalyst acidity for hydrocarbon catalytic cracking

AbstractThis work built a molecular‐level kinetic model for hydrocarbon catalytic cracking, incorporating the catalyst acidity as the parameter to estimate reaction rates. The n‐decane and 1‐hexene co‐conversion catalytic cracking process was chosen as the studying case. The molecular reaction network was automatically generated using a computer‐aided algorithm. A modified linear free energy relationship was proposed to estimate the activation energy in a complex reaction system. The kinetic parameters were initially regressed from the experimental data under several reaction conditions. On this basis, the product composition was evaluated for three catalytic cracking catalysts with different Si/Al. The Bronsted acid and Lewis acid as the key catalyst properties were correlated with kinetic parameters. The built model can calculate the product distribution, gasoline composition, and molecular distribution at different reaction conditions for different catalysts. This sensitive study shows that it will facilitate the model‐based optimization of catalysts and reaction conditions according to product demands.

Multiple important roles of phosphorus modification on the ZSM-5 in ethanol to olefin reaction: Acidity adjustment, hydrothermal stability and anti-coking

The effects of phosphorus doping on the reaction of bioethanol to light olefins catalyzed by HZSM-5 were studied from both catalytic experiments and molecular simulations. P-doping promotes the highest yield of propylene up to 35.0 %. The propylene yield remained above 22.5 % even after 100 h. The introduction of P improves the catalyst acidity and the electronic environment of the active center of HZSM-5, which is beneficial to increase the selectivity of propylene, making the adsorption and conversion reaction of ethanol and the desorption of ethylene and propylene products more favorable. The framework aluminum is stabilized by the phosphate groups outside the framework, so that the framework dealumination is inhibited. The deep polymerization of ethylene is inhibited, and the anti-coking ability is enhanced. The presence of water enhances the hydrothermal stability and inhibit the carbon deposition of P-modified ZSM-5 catalyst, which makes the P-doping ZSM-5 the most promising catalyst for bioethanol conversion applications.

Ultrafine particles of zeolitic imidazolate frameworks induced by efficient nucleation facilitated conversion of microalgal lipids

In order to improve property and utilization of active sites on catalyst surfaces, novel ultrafine particles of zeolitic imidazolate framework (ZIF-67) were synthesized for microalgal biodiesel production. The synergy of N,N-dimethylformamide (DMF) and ethanol promoted deprotonation of imidazole and efficient nucleation of ZIF-67, which reduced crystal size from ∼300 nm (using methanol as solvent) to ∼20 nm. Meanwhile, the ratio of unsaturated coordinated Co-Nx (x = 1,2,3) to saturated CoN4 increased from 0.40 to 0.57, and pyridinic N content on catalyst surface increased from 16.59% to 32.25%, which enhanced the acidity and basicity of catalyst. The total acidity of optimal ZIF-67 increased from 0.125 to 0.691 mmol/g, while total basicity increased from 0.078 to 0.137 mmol/g. Density functional theory (DFT) calculations clarified that unsaturated Co-Nx sites and pyridinic N exhibited excellent catalytic activity. Therefore, ZIF-67-DE catalyst (using DMF and ethanol as solvents) effectively converted microalgal lipids into biodiesel with a catalytic efficiency of 97.8%.

1,4-d-Sorbitan: A Promising Biobased-Platform for the Synthesis of Chiral Amines.

The regio- and diastereoselective synthesis of chiral amines derived from 1,4-d-sorbitan has been developed via the borrowing hydrogen reaction using a cooperative catalysis between an achiral iridium catalyst and diphenylphosphoric acid. The different reactivities of the four hydroxyl groups on the 1,4-d-sorbitan scaffold have also been highlighted.

Tandem CO2 Valorization and Ethane Dehydrogenation: Elucidating the Nature of Highly Selective Iron Oxide Active Sites

Iron oxide-based catalysts can selectively covert CO2 to added-value CO in parallel with on-purpose ethylene production via ethane dehydrogenation (CO2-EDH). The 5Fe/10NiMgZr catalyst, calcined at 700 °C for 5 h, reached 90% selectivity, at a single-pass C2H6 conversion of ∼23.3%, during CO2-EDH at 650 °C. X-ray characterization techniques (XRD, XPS, XAS, and XRS), along with structural modeling were used to elucidate the nature of highly selective active sites toward C–H bond scission. Under reaction conditions, Fe atoms are incorporated into the support lattice, as it was exemplified by XRS at Mg L2,3- and O K-edges. The dynamic structural modifications, occurring during CO2-EDH, highlighted the pivotal role of the support, reaching an ethylene yield of 21%. Mg coordination altered from octahedral to tetrahedral. The latter was accompanied by an electronic modification, which had a strong impact on the catalyst acidity, based on Fourier transform infrared spectroscopy combined with in situ adsorption of pyridine, resulting in an unpresented ethylene selectivity for Fe oxide-based catalysts.

Hydrolysis-oxidation of cellulose to formic acid in the presence of micellar vanadium-containing molybdophosphoric heteropoly acids

OxFA-processing of inedible cellulose is considered as a perspective way for the production of biogenic formic acid (FA) which appeared to be a promising source for sustainable energy. In our work, the one-pot hydrolysis-oxidation of cellulose to FA was studied in the presence of the micellar acidic catalysts based on Mo–V–P heteropoly acids [Cn-MIM]y/H3+x-yPMo12-xVx (n = 6, 10 and 16; x = 1, 2 and 4; y = 2–6). The influence of amount of V, substitution of H+ by [Cn-MIM] and the length of alkyl group Cn of the cation was revealed. The optimization of the reaction conditions was also performed. To our knowledge, heterogeneous catalysts of such a composition were applied in cellulose hydrolysis-oxidation to FA for the first time. In the presence of C10-MIM/HPMo11V catalyst, the optimal reaction conditions were determined: 10 g/L of cellulose, 1.25–10 g/L of catalyst, 5 MPa of gas mixture (O2/N2 - 20/80 vol/vol) and 170–180 °C. Decreasing the alkyl group length of Cn-MIM+ cation or V content into framework of heteropoly anion were revealed to rise up the yield of the target product. These correlations were caused by the following factors. First, the decreasing acidity of micellar catalysts. Senond, the change in distribution of electron density in heteropoly anion due to the interaction between hydrogen atoms of alkyl group of Cn-MIM cation and oxygen atom of heteropoly anion. Third, blocking of V active sites for reagents. Influence of acidity on catalytic properties of micellar catalysts was also revealed in the course of screening samples with the different degree of protons substitution by C16-MIM+. The reaction rate was demonstrated to rise with increasing degree of protons substitution by C16-MIM + cation in C16-MIM/HyPMo11V and C16-MIM/HyPMo8V4 samples. The yield of FA up to 45 mol% can be reached over micellar HPA catalysts studied.

Structural and Catalytic Properties of the Binary Systems Alumina – Amorphous Aluminosilicate

The amorphous aluminosilicate – alumina systems were examined using various physicochemical methods, including the analysis of 27Al NMR spectra of solid samples, estimation of the catalyst acidity by temperature-programmed desorption of ammonia, investigation of the sample structure by X-ray diffraction analysis, and thermogravimetric analysis of the samples. A study on the catalytic properties of the samples upon cracking on the model feedstock n-dodecane in a mixture with 2-methylthiophene revealed that conversion of the feedstock increases in the series: 100 % Al2O3 (AH) &gt; 70 % Al-Si + 30 % Al2O3 (AH) &gt; 30 % Al-Si + 70 % Al2O3 (AH) &gt; 100 % Al-Si (AH – aluminum hydroxide obtained by sulfate method; Al-Si – amorphous aluminosilicate). An increase in the calcination temperature of the samples from 500 to 700 °C decreases the conversion of the feedstock. The growing contribution of hydrogen transfer reactions leads to an increase in the formation selectivity of hydrogen sulfide and a decrease in the content of sulfur compounds in the liquid products.

Promoting catalytic performance by balancing acid and redox sites on Mn3O4–Mn2P2O7/TiO2 for selective catalytic reduction of NO by NH3 at low temperature

The surface acidity and redox property of catalyst are extremely important in the selective catalytic reduction of NOx with NH3 (NH3-SCR) process. In this work, phosphoric acid was used to regulate the acidity and redox property of Mn3O4/TiO2 and Mn3O4–Mn2P2O7/TiO2 (MnPO/TiO2) catalyst was firstly prepared. And its effect on the catalytic activity was investigated in NH3-SCR. The experimental results showed that Mn2P2O7 modified Mn3O4/TiO2 catalyst exhibited excellent catalytic activity and strong resistance to SO2 and H2O than Mn3O4/TiO2. The Brunauer-Emmett-Teller (BET) results showed that the formation of Mn2P2O7 was beneficial to optimize pore structure and significantly increased the specific surface area of Mn3O4/TiO2 catalyst. At the same time, the generation of Mn2P2O7 led to partial obstruction of Mn3+/Mn4+ with Mn2+ redox cycles, which weakened the redox property of Mn3O4/TiO2 catalyst and then prevented excessive dehydrogenation of NH3. Furthermore, the introduction of Mn2P2O7 provided more acid sites for Mn3O4/TiO2 catalyst. The moderate redox property and enhanced acidity facilitated adsorption and activation of NO and NH3. In situ DRIFTs results showed that the SCR reaction over MnPO/TiO2 catalyst at 200 °C was predominantly controlled by L-H route.