Apparent Order Research Articles

Enhancement of the intrinsic Ni/GDC activity under rSOC operation by means of Fe–Au doping: An electro-kinetic study

The investigation dealt with the effect of Fe and Au wt.% concentrations on the enhanced performance and stability of Ni/GDC under rSOC operation. Moreover, it focused on the comparison of the intrinsic electro-kinetics between the best performing Fe–Au-modified cell and Ni/GDC under SOE operation. The rSOC performance and stability of all cells was examined in the temperature range of 900–800 °C. The electro-kinetic measurements took place at 900 °C by varying the pH2O. All Fe–Au–Ni/GDC electrodes exhibited enhanced activity, compared to the SoA Ni/GDC, with variations in their stability after three rSOC cycles. Specifically, the fuel electrode with the lowest wt.% concentration in Fe and Au (0.5Fe–1Au–Ni/GDC) exhibited the highest activity and stability under rSOC operation. By increasing the wt.% loadings to 2 wt% Fe and 3 wt% Au, there was rapid degradation of the initially high performance, mainly due to increase of the ohmic resistance. SEM analysis showed higher macro-porosity on the reduced state of the modified electrodes, which in the case of the best performing 0.5Fe–1Au–Ni/GDC was the least affected after rSOC operation. Interestingly, the SOE performance of the examined Fe–Au-modified electrodes was not similarly inhibited by the decrease of temperature, compared to Ni/GDC. This was further clarified through electro-kinetic measurements, aiming to verify the effect from the Fe–Au doping on the intrinsic electrochemical activity of Ni/GDC for the H2O electrolysis reaction. Comparison between the SoA and the best performing 0.5Fe–1Au–Ni/GDC showed an enhancing effect on the intrinsic electro-kinetics of the modified electrode. Specifically, the dependence of the polarization resistance on the pH2O was found to be strongly positive, resulting in a higher apparent reaction order, compared to Ni/GDC.

Highly active sulfonic ionic liquid modified heteropoly acid composite catalysts for efficient production of ethyl palmitate

Highly active inorganic-organic composite catalysts were synthesized by incorporating Keggin-type tungstophosphoric acid (H3PW12O40; HPW) with SO3H-functionalized ionic liquids (SFILs), which were prepared by integrating chloromethylated polystyrene (CP) resin, piperazine (PI) and 1.3-propane sultone, as primary sources. The [CPPI-SO3H]nH3−nPW12O40 (n = 1.0–3.0) catalysts were characterized by XPS, SEM, FT-IR, XRD, TG-DTA, TEM, and solid-state 31P MAS NMR. These HPW-SFIL composite catalysts were found to be highly stable and possess ultra-strong Brønsted acidity, desirable self-separation properties, and catalyst reuse for production of biodiesels through esterification of palmitic acid (PA) and ethanol (EtOH). On the basis of the Box-Behnken design (BBD), further process optimization using response surface methodology (RSM) over the [CPPI-SO3H]2.0H1.0PW12O40 catalyst led to the optimized experimental conditions: EtOH/PA = 7.7 mol/mol, catalyst amount = 4.4 wt%, reaction time = 2.5 h, reaction temperature = 363 K, accompanied by an ethyl palmitate yield of 97.2%, in excellent agreement with the predicted value. The catalyst was highly stable, retaining a 94.7% yield after six consecutive running cycles. Moreover, a kinetic study performed under optimal reaction conditions revealed an apparent reaction order of 1.40 and an active energy of 14.80 kJ mol−1.

Total turnover number prediction of an aggregating biocatalyst: Amino ester hydrolase (AEH)

Amino ester hydrolase (AEH) from Xanthomonas campestris is a promising candidate for β-lactam synthesis but suffers from low thermostability and rapid deactivation. Wild-type AEH was found to deactivate with an apparent order that varies with temperature from n = 2 at 30 °C (close to the temperature of optimum activity Topt) to n = 1.5 at 25 °C. AEH features two transitional temperatures: (1) from native ‘N’ to partially unfolded, inactive intermediate ‘I’, and (2) from partially unfolded to fully unfolded entity ‘U’ at the melting temperature Tm. CD and light scattering data suggest aggregation near Topt. To determine the total turnover number TTN, AEH was deactivated by imposing a temperature gradient and recording instantaneous rates of cephalexin hydrolysis. The TTN increased ∼ 5-fold from the wild-type (WT) for the quadruple variant N186D/A275P/E143H/V622I (QVH) at 25 °C and 10 nM AEH but varied significantly with AEH concentration and temperature.

Structural-disorder-driven critical quantum fluctuation and localization in two-dimensional semiconductors

Quantum fluctuations of wavefunctions in disorder-driven quantum phase transitions (QPT) exhibit criticality, as evidenced by their multifractality and power law behavior. However, understanding the metal-insulator transition (MIT) as a continuous QPT in a disordered system has been challenging due to fundamental issues such as the lack of an apparent order parameter and its dynamical nature. Here, we elucidate the universal mechanism underlying the structural-disorder-driven MIT in 2D semiconductors through autocorrelation and multifractality of quantum fluctuations. The structural disorder causes curvature-induced band gap fluctuations, leading to charge localization and formation of band tails near band edges. As doping level increases, the localization-delocalization transition occurs when states above a critical energy become uniform due to unusual band bending by localized charge. Furthermore, curvature induces local variations in spin-orbit interactions, resulting in non-uniform ferromagnetic domains. Our findings demonstrate that the structural disorder in 2D materials is essential to understanding the intricate phenomena associated with localization-delocalization transition, charge percolation, and spin glass with both topological and magnetic disorders.

Photocatalytic Degradation and Kinetics of Dyes in Textile Effluent Using UV – ZnO-Al System

This study investigates the photodegradation of a mixture of 4 azo dyes (direct orange 39, chlorantine fast red 5B, viscose black B and direct sky blue K) present in textile effluents and the influence of catalyst dose, irradiation time, UV power intensity on the overall photodegradation kinetics of the process. The photocatalytic experiments were conducted in a batch stirred photoreactor equipped with a 10 W, 30W and 60 UV lamps, magnetic stirrer and thermometer. The photocatalysts used was zinc oxide nanoparticle doped with aluminium (AZO, 15nm, 99.99 to %). The results obtained showed that variation in the physical parameters influenced the efficiency of photodegradation. The kinetic study indicated that the photodegradation of the dyes present in the effluent from the textile industry followed the Langmuir-Hinshelwood model that is modified to accommodate reactions occurring at a solid-liquid interphase. At the catalyst dose of 0.5g/l, the apparent first order rate constant K1, was 0.00615 min-1 but at 2.5g/l it reduced to 0.00567 min-1. The best degradation was at the catalyst dose of 2.0g/L with the rate constant of 0.0134 min-1.

Dependence of carbonyl, sulphoxide and hydroxyl functional group formation on oxygen concentration during the oxidation of roading bitumen

The aim of this study was to provide insights into the chemical mechanism by which, over the course of its lifetime, bitumen in road surfacings reacts with oxygen in the atmosphere. Oxidation was measured at 50 °C (a realistic in-service temperature) to determine the effect of oxygen concentration on the formation of key oxidation products. Experiments were conducted on thin films of bitumen (<0.03 mm) so that the effect of oxygen diffusion on the rate was negligible. The films were oxidised under air (oxygen partial pressure 22.23 kPa) and pure oxygen (101.33 kPa).The rate of formation of carbonyl, sulphoxide and hydroxyl group containing reaction products was measured by infrared spectroscopy. The reactions were carried out over a time-frame sufficient to cover both the “fast” and “slow” (linear) reaction rate regions and the results discussed in terms of the reaction mechanism. It was observed that the rate of formation of all three functional groups was dependent on oxygen concentration. The apparent reaction order with respect to oxygen concentration was about 0.5 in each case and did not change significantly as the reaction moved from the fast and into the linear rate regions. The non-zero rate dependence observed despite the relatively high oxygen partial pressures used, is significant in that it is inconsistent with a conventional free radical autoxidation chain mechanism and suggests a parallel oxidation process is occurring.

Kinetic investigations of oxidative dehydrogenation of propane on boron oxide in confined spaces

Oxidative dehydrogenation of propane (ODHP) is a promising process for on-purpose propylene production with favorable thermodynamics. Boron-based catalysts exhibit high alkene selectivity in ODHP, but the understanding of catalytic mechanism remains incomplete, especially regarding the observed supra-linear reaction order of alkanes. In this work, we studied the impact of spatial confinement on the performance and kinetics of boron oxide supported on silica with different pore structures. The formation rate of propylene decreases with the degree of confinement of active boron sites derived from the support. Intriguingly, the apparent activation energy increases with the ODHP activity, and exhibits a positive correlation with the apparent propane reaction order. The apparent propane order of B2O3/SiO2 varies from 1 to 3, which is impacted by pore structure of supports, loading of B2O3, and partial pressure of propane. The trend in propane reaction order and apparent activation energy on B2O3 can be rationalized by the rate expression derived based on the proposed radical chain mechanism with three distinct pathways of propane activation.

Leaching kinetics of de-lithium residue from spent ternary lithium-ion battery cathodic materials with starch as reductant

Starch was employed as a reductant for the recovery of Ni, Co, and Mn from ternary lithium-ion batteries (LIBs) cathodic materials de-lithium residue, and the leaching kinetics and mechanism were studied. The effects of stirring speed, leaching temperature, H2SO4 concentration, and starch dosage on leaching efficiencies of Ni, Co, and Mn from de-lithium residue were systematically investigated. Optimized conditions (1.5 mol/L H2SO4, 6 g/L starch, stirring speed of 500 r/min, 80 °C and 60 min) yielded leaching efficiencies of 98.07%, 96.52%, and 98.06 %, for Ni, Co, and Mn, respectively. Apparent activation energies, described by the chemically controlled unreacted shrinking core model, were 93.32, 102.84, and 95.68 kJ/mol, for Ni, Co, and Mn, and their apparent reaction orders in H2SO4 were 0.9225, 1.0335, and 1.1285, respectively. Starch is abundant, affordable, and exceptionally alternative to conventional reductants for the recovery of valuable metals from spent ternary LIBs.

Determination of the kinetic parameters of leaching from experimental data using the non-porous shrinking particle model: Effect of error propagation

All alternatives of the non-porous shrinking particle model (NSPM) referred to in the literature were reviewed and critically compared – they differ especially in their ability to reflect the role of three crucial model parameters: the order of reaction, liquid/solid ratio and activity coefficient of the leaching reagent. A procedure to calculate an experimental error related to the methodology of laboratory leaching tests (including the effect of different ore-particle size) has been proposed. Error propagation in the process of determination of the apparent order of reaction and activation energy from experimental data was analysed in detail, to estimate the systematic error of the simulation model developed. The simulation models tested were validated using the experimental data for the reaction system MgO-HCl-H2O. Based on the results obtained, some recommendations for an effective practical use of the NSPM have been suggested.

Phosphorus Recovery from Municipal Wastewater: Brucite from MgO Hydrothermal Treatment as Magnesium Source

Crystallization of struvite (MgNH4PO4·6H2O, MAPH) for both N and P recovery from municipal wastewater is an attractive alternative. The low magnesium concentration in municipal wastewater calls for low-cost magnesium sources. In the present work, the precipitation of struvite from supersaturated solutions was investigated. The supersaturated solutions were prepared by the addition of either slurry of Mg(OH)2 (brucite) obtained from the hydrothermal treatment of magnesium oxide (MgO) or using the aqueous solution equilibrated with brucite after separation from the solid. In both cases, in the supersaturated solutions prepared by the addition of ammonium dihydrogen phosphate, the Mg:NH4:P ratio was 1:1:1, pH 7.0–11.0. The apparent order for the precipitation suggested that the dominant mechanism was surface diffusion according to the polynuclear model. The apparent rate constant for struvite precipitation was two orders of magnitude smaller for the slurry prepared supersaturated solution in comparison with the respective prepared from the brucite-equilibrated solution. Simulated wastewater (SWW), was supersaturated with respect to struvite, by inoculation with brucite. The apparent rate constant was two orders of magnitude higher than that corresponding to the supersaturated solutions prepared by the addition of solution equilibrated with brucite. The P recovery from SWW reached 70%.

Mononuclear Re sites on In2O3 catalyst for highly efficient CO2 hydrogenation to methanol

Catalytic hydrogenation of CO2 to methanol utilizing H2 derived from renewable energy represents one of the most prospective strategies for the sustainable recycle of carbon. Accordingly, the design and preparation of high-performance catalysts for methanol production has received broad attention. Herein, In2O3 supported mononuclear Re is reported to be an efficient catalyst for methanol production which exhibits methanol selectivity of up to 80% at CO2 conversion of 11.5%, providing a methanol STY of 758 mg·h−1·gcat−1 under 5 MPa and 300 °C, more than twice as that for pristine In2O3 (376 mg·h−1·gcat−1). The apparent reaction orders of CO2 and H2 were determined to be around 0 and 0.6 respectively, suggesting the activation of H2 is more crucial compared with CO2. In-depth characterizations reveal that the remarkably improved performance originates from the mononuclear Ren+ sites strongly interacting with In2O3, which significantly enhance the ability of H2 dissociation. Combined experimental and theoretical studies proved the feasibility of formate pathway over In2O3 supported mononuclear Re catalyst. The results of DFT calculations suggest that mononuclear Re site on In2O3(111) model plays a vital role on heterolytic H2 dissociation and intermediates transformation, boosting the formation of HCOO* and lowering the energy barriers of rate-determining step for methanol formation.

Base-metal oxide semiconductor electrodes for PPCP degradation: Ti-doped α-Fe2O3 for sulfosalicylic acid oxidation as an example

Sulfosalicylic acid is a typical pharmaceutical and personal care product with high toxicity, environmental persistence, and low biodegradability. Electrochemical oxidation has been demonstrated to be a promising way for hazardous organics treatment, but it is severely limited by the high cost and resource shortage of electrode materials. Base-metal oxide semiconductor anodes have the merits of low cost, diversity, and tunable energy levels for charge transfer, and thus may be alternatives to the electrodes for wastewater treatment. Herein, we found that Ti-doped α-Fe2O3, as an example, could be efficient for sulfosalicylic acid oxidation, reaching comparable faraday efficiency of sulfosalicylic acid to that of the boron-doped diamond electrode. Ti-doped electrodes exhibited both higher removal rates and current efficiency compared to the undoped. This could be mainly ascribed to the enhanced charge transfer rate constant. Kinetic analysis shows that the apparent reaction order, in terms of sulfosalicylic acid in bulk solution, depended on applied potential and pollutant concentration. Mechanism study shows that the oxidation of sulfosalicylic acid was mainly through indirect pathway. Moreover, the oxidation products were determined and the oxidation mechanism was proposed. This study may open a door to employ base-metal oxide semiconductor anodes for the efficient treatment of organic wastewater.

CHARCTERISTICS OF NEW BUILDINGS IN THE IMPACT AREA OF A LARGE CITY

The existence of many field estates, despite their apparent order, from the landscape point of view is chaotic, incoherent and inefficient in terms of communication. The article attempts to create a typology of the most characteristic layouts of housing estates and to indicate the main factors influencing the formation of building complexes. The subject of the study is the analysis of the specificity of the spatial development of suburban zones in three cities: Rzeszów, Poznań and Warsaw. The aim of the analysis is to show the similarities and differences in selected areas. The implementation effect is the recognition of the nature of the buildings spreading outside the city’s territory. Determining the typology of buildings that can be located in specific areas may also help in practice of issuing decisions on development conditions. The catalogue of possible solutions, together with the analysis of the produced communication systems, will allow to forecast the spatial shape of future investments and, consequently, to optimize the provisions limiting pathological solutions.

Larger Intrinsic Rate Constants of Alpha-amylase is Possible if Intrinsic Forward Rate Constant is ≠ Diffusion limited Rate of Encounter

Background: Previous research has shown that the intrinsic reverse (backward) and forward rate constants are larger than the effective or apparent rate constants for the formation and dissociation of an enzyme-substrate complex (ES). It is speculated that such intrinsic rate constants could be larger if an appropriate mathematical equation was adopted for their computation. &#x0D; Methods: Theoretical, experimental (Bernfeld method), and computational methods.&#x0D; Objectives: 1) To rederive the equations for calculating the intrinsic rate constants for forward (k1) and reverse (i.e., backward) (k2) reactions; 2) to calculate the intrinsic rate constants; and 3) to show that the probability (1/g) (or req(r)) that an enzyme is at a distance from the substrate is a variable. &#x0D; Results and Discussion: The equations for the determination of k2 and k1 were rederived. Unlike previous findings, the intrinsic (reverse) first order rate, k2 and forward second order rate, k1 were larger than their apparent counterparts, but they were, however, very similar in magnitude. The intrinsic rate constants were much larger than previously reported values when the enzyme (E) total concentration [ET] was much less than substrate’s total concentration [ST]. The k1 and apparent forward second order rate (kf) values where [ET] is much less than [ST] were &gt; where [ET] is less than [ST]. Therefore, the magnitude of the second order rate constant is a function of [ET]. The values of k1 and k2 where [ET] is much less than [ST] and vice-versa were respectively, 7.41 exp. (+6) L/mol. min and 81.34 exp. (+4) /min, and 15.76 exp. (+6) L/mol. min and 58.08 exp.(+4) /min. It was discovered that the probability (1/g) (or req(r))) that an enzyme is at a distance from the substrate with the possibility of mutual attraction is not constant. &#x0D; Conclusion: If the intrinsic forward rate constant (k1) is not equal to diffusion limited rate (kD) of encounter, the k1 and k2 values could be larger than values where k1 is equal to kD. The probability (1/g) (or req(r)) that an enzyme is at a distance from the substrate with the possibility of mutual attraction has been discovered to be a variable constant dependent on the concentration of the reaction mixture components and the enzyme's affinity for the substrate, and vice versa. Future research may attempt to derive an equation for the determination of an intrinsic catalytic rate constant for the formation of a product.

Kinetics of Low-Grade Scheelite Leaching with a Mixture of Sodium Phosphate and Sodium Fluoride

The current technology of leaching low-grade scheelite with sodium hydroxide or sodium carbonate has the disadvantages of large leaching reagent dosage and low leaching efficiency of tungsten. In order to extract scheelite efficiently, the kinetics of low-grade scheelite leaching with a mixture of sodium phosphate and sodium fluoride was investigated. In this study, the effects of temperature, phosphate concentration, and fluoride ion concentration on the leaching rate of tungsten were investigated. Our results showed that the leaching rate of tungsten was greatly influenced by the temperature and less affected by the concentration of phosphate and fluorine ions. The leaching process was controlled by a chemical reaction with an apparent activation energy value of 51 ± 0.2 kJ/mol. The apparent reaction orders with respect to phosphate and fluorine ions were 0.49 and 0.11, respectively. The reaction product calcium fluorophosphate was a loose, rod-like crystal, which would not tightly wrap on the surface of scheelite to prevent the diffusion process. The leaching kinetics of low-grade scheelite was in accordance with the shrinking core model, and the corresponding kinetic equation was also established.

Modelling the kinetics of stearic acid destruction on TiO2 ‘self-cleaning’ photocatalytic films

The kinetics of stearic acid, SA, removal by photocatalytic films are modelled using a log-normal distribution in surface reactivity, which shows that as the distribution in reactivity, ρ, increases, so too does the apparent order of reaction, m, of the observed variation in SA concentration, [SA], versus irradiation time, t. The model is used to fit the observed [SA] vs. t profiles exhibited by three very different TiO2 films, namely Activ™ self-cleaning glass, and prepared sol-gel TiO2 and P25 TiO2 films. These films show decay kinetics, with m = 0.3, 0.44 and 0.6, respectively, which fit the model predicted decay profiles with distribution width, ρ, values, 0.4, 0.54 and 0.7, respectively. A Ag photocatalyst indicator ink is used on these films to highlight the non-uniform distribution in surface reactivity on the micron scale. The use of the log-normal model to better understand the kinetics exhibited by photocatalytic films is discussed briefly.

Purification of highly concentrated cyanide-containing wastewater via stepwise recovering of valuable components

This study develops an efficient technique to purify the highly concentrated cyanide-containing industrial wastewater by recovering the valuable components. Firstly, sodium sulfide, sodium polysulfide and ferrous sulfate were respectively used as the precipitating agents to retrieve zinc, copper and iron from wastewater stepwise. In the meantime, cyanide presented as free cyanide and copper–cyanide complexes were transformed into thiocyanate by polysulfide. Afterwards, the solvent extraction of thiocyanate was systematically conducted with trioctylamine (TOA) as the extraction agent and sodium hydroxide solution as the stripping agent. The results showed that the contents of zinc, copper and iron in the solution after precipitation were less than 1 mg·L−1. Focusing on the reaction between copper–cyanide complex and polysulfide, three stages were established for the first time. In the first stage, Cu(CN)32− was gradually converted to CuCN0 and thiocyanate was rapidly generated. In the second stage, in addition to the formation of thiocyanate, Cu(I) was oxidized by polysulfide and precipitated as CuS ultimately. With an apparent activation energy of 70.9 kJ∙mol−1, kinetic analysis of the second stage suggested a significant effect of temperature on the copper–cyanide complex conversion rate. The apparent reaction orders of zero-valent sulfur and cyanide was 1.34 and 2.33, respectively. After the extraction and stripping process, the extraction efficiency of thiocyanate was nearly 100 % and the concentration of it can be enriched to 125 g·L−1 in the stripping solution. TOA and thiocyanic acid formed an extraction complex in a 1:1 ratio. This approach achieves the simultaneous recovery of valuable metallic ions (zinc, copper and iron) and cyanide conversion under the alkaline condition, which provides a new idea for the treatment of highly concentrated cyanide-containing wastewater with a complicated composition.

Effects of Surface Hydrophobicity on Catalytic Transfer Hydrogenation of Styrene with Formic Acid in a Biphasic Mixture.

Transfer hydrogenation (TH) of unsaturated hydrocarbons with formic acid (FA) is an attractive processing pathway for the reduction of lignocellulosic pyrolysis oils. The low solubility of hydrophobic bio-oil species in water and FA in oil necessitates the use of a biphasic system as the reaction environment. Here, we report the effects of Pd/silica catalyst surface wettability on the TH reaction rate. Modification of the surface with short chain (C1-C4) alkyl silanes resulted in an increase in the reaction rate as compared to the unmodified catalyst. In contrast, modification of the surface with sulfonate (hydrophilic) and C18 alkyl silanes (hydrophobic) resulted in a decrease in the reaction rate as compared to the unmodified catalyst. The results are discussed in terms of the catalyst interfacial activity and relative affinity of the reagents to the Pd active sites. An observed change in the apparent reaction order in styrene for a hydrophilic catalyst suggests that changing catalyst surface wettability from hydrophilic to hydrophobic resulted in a switch from a transport-limited to a kinetic-limited reaction regime.

Thermodynamic and kinetic parameters of iodine extraction from chloride aqueous solutions

Extraction is a versatile and relatively simple method for extracting rare and scattered elements, producing good results at minimal expenses in terms of reagents and equipment. Information about the thermal effects and kinetic dependencies of the extraction process is essential for predicting and counteracting fluctuations in external conditions. In this work, the thermodynamic and kinetic parameters of the iodine extraction process were studied using model solutions that contained sodium chloride with an ionic strength of 0–5 mol/l as a background mineralization. This composition closely corresponds to natural and man-made waters of oil and gas condensate fields. A mixture of tri-n-butyl phosphate and isooctane was used as the extractant. In order to evaluate thermodynamic parameters, extraction isotherms were constructed at temperatures of 278 and 288 K. For different background ionic strength values, equilibrium extraction parameters were determined, including the extraction degree, distribution coefficient and equilibrium constant, as well as changes in the enthalpy, entropy and Gibbs energy of the process. A study of the kinetic dependencies of iodine extraction from aqueous solutions under different ionic strength values at temperatures of 278, 288 and 293 K allowed the true and apparent orders of reaction to be established, along with the activation energy of the extraction process. Across the entire range of the studied ionic strength values, iodine extraction occurs spontaneously with high distribution coefficients and an extraction degree of over 86%. The kinetic parameters of the iodine extraction process (activation energy, temporal and concentration reaction order) indicate the diffusion nature of the rate-determining step, the presence of intermediate complexation stages and the absence of temperature effects on the reaction rate.

Kinetics of Liquid-Phase Condensation of Propylene with Formaldehyde over H–MFI and H–BEA Zeolites

This study investigated the kinetic patterns of the liquid-phase Prins condensation of propylene with formaldehyde in the range of 120–180°C over H–MFI and H–BEA zeolites. The apparent reaction order with respect to formaldehyde was found to vary between 0.1 and 0.2 for H–BEA and to be close to zero for H–MFI. The apparent activation energy for H–MFI and H–BEA was 26.1±0.6 kJ/mol and 20.0±4.0 kJ/mol, respectively. Based on these results, the reaction was demonstrated to occur in the intradiffusion or transition region; the calculated Thiele modulus and effectiveness factor further confirmed this fact. The diffusion limitations were partially removed by raising the initial formaldehyde concentration, as indicated by an increase in the apparent order of formaldehyde conversion to 1.0 for H–BEA and to 0.4 in the H–MFI case. To describe the substrate transformations observed, a modernized reaction mechanism was proposed.