Fixed Bed Plug Flow Reactor Research Articles

Catalyst Activity Profile Estimation and Dilution Rate Optimization on Fixed Bed Plug Flow Reactor

Catalyst Activity Profile Estimation and Dilution Rate Optimization on Fixed Bed Plug Flow Reactor

Nonoxidative dehydrogenation of propane using boron-incorporated silica-supported Pt Sites synthesized by atomic layer deposition.

Nonoxidative dehydrogenation of propane to propylene using Pt-based supported catalysts is an active research area in catalysis because catalyst attributes of Pt sites can be controlled by careful design of active sites. One way to achieve this is by the addition of a second metal that may impart a change in the electron density of active sites, which in turn affects catalytic performance. In this study, bimetallic Pt and B sites were deposited on powder SiO2 using atomic layer deposition (ALD). Boron was first deposited on SiO2 via half-cycle ALD using triisoproplyborate as the B source. Following calcination, Pt deposition was performed via half-cycle ALD using trimethyl(methylcyclopentadienyl)platinum(IV) as the Pt source. The synthesized catalysts were reduced under H2 at 550 °C and characterized using inductively coupled plasma optical emission spectroscopy for elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO to examine the properties of Pt, and time-resolved X-ray absorption near edge structure spectroscopy to examine the changes in the reducibility of Pt sites. The samples were then tested for nonoxidative dehydrogenation of propane at 550 °C using a fixed-bed plug-flow reactor to examine the role of B on the catalytic performance. Characterization results showed that the addition of B imparted an increase in electron density and affected the reducibility of Pt sites. In addition, incorporating B on SiO2 created anchoring sites for Pt ALD. The amount of Pt deposited on B/SiO2 was 2.2 times that on SiO2. Catalytic activity results revealed the addition of B did not change the initial activity of Pt sites significantly, but improved propylene selectivity from 80% to 87% and stability almost threefold. The enhanced selectivity and stability of PtB/SiO2 is most presumably due to favored desorption of propylene and mitigating coke formation under reaction conditions, respectively.

A principal component analysis assisted machine learning modeling and validation of methanol formation over Cu-based catalysts in direct CO2 hydrogenation

With the advent of powerful machine learning algorithms strongly supporting complex non-linear regression modeling, catalyst design features for a wide and customized set of catalysts used for a specific reaction have been made easy. Herein, we use these techniques in the methanol synthesis by CO2 reduction over Cu-based binary and ternary catalysts with the help of three machine learning algorithms: artificial neural network, support vector machine regression, and gaussian process regression. 227 catalytic performance dataset points from existing literature on CO2 hydrogenation to methanol were compiled and initially accessed by Principal Component Analysis (PCA) for training and preliminary evaluation of the algorithms, which was further guided using a 10-fold cross-validation method. The predictive model and its insights were validated experimentally over 30 datasets derived from experimental runs of this reaction over a ternary Cu/ZnO/ZrO2 laboratory-synthesized catalyst at varying conditions of temperature, pressure, and space velocity in a continuous mode fixed-bed plug-flow reactor. The assessment of the space of input and laboratory data was aided by Principal Component Analysis (PCA), scores, and loadings plot. This work shows how experimentalists can predict typical heterogeneous catalytic reaction outputs (R2 greater than 0.9 for three variables) with fair accuracy using a combination of machine learning and PCA.

In situ and operando study of catalysts during high-temperature high-pressure catalysis in a fixed-bed plug flow reactor with x-ray absorption spectroscopy.

Numerous important catalytic reactions, such as Fischer-Tropsch synthesis (FTS), are performed under harsh conditions in terms of high temperature of a catalyst in a mixture of reactants at a high pressure. There has been a lack of an intrinsic correlation between a catalytic performance and its corresponding catalyst structure due to the unavailable information on the authentic structure of the catalyst during catalysis under a high-temperature high-pressure (HTHP) condition. Here, we report in situ/operando studies of Co catalysts during catalysis under HTHP conditions using x-ray absorption spectroscopy (XAS). A high-temperature high-pressure catalysis-XAS (HTHP Catalysis-XAS) system using a thin, small quartz or beryllium tube as the reactor was built for in situ/operando characterization of high-energy absorption edges of 4d transition metals or low-energy absorption edges of 3d/4d transition metals under high-temperature high-pressure conditions, respectively. This reactor can be used for HTHP catalysis performed at a temperature of up to 550 °C and a gas pressure of up to 60 bars for uncovering the chemical states and coordination environments of metal atoms of these catalysts during HTHP catalysis. The capability of collecting XAS data during HTHP catalysis was confirmed through tests at 400oC in the mixture of 20 bar mixture of reactants at beamline endstation. The operando studies of Ru catalyst particles under Fischer-Tropsch catalytic conditions with extended x-ray absorption fine structure spectroscopy revealed a restructuring of the Ru catalyst at 250 °C in the mixture of 6 bars CO and 12 bars H2 during FTS (30 ml/min), which was not observed at 300 °C in 1bar H2 (20 ml/min). This observation suggests new chemistry for metal catalysts under HTHP condition inaccessible due to a lack of applicable characterizations. These tests confirmed the function of this HTHP Catalysis-XAS system for in situ/operando characterizations of catalysts during HTHP catalysis.

Cover Picture: A Versatile Ambient‐to‐High‐Pressure Reaction Transmission Cell for in situ/operando Infrared Spectroscopic Investigations (Chemistry ‐ Methods 7/2021)

The Front Cover shows a self-developed stainless-steel reaction cell for operando transmission FTIR studies of heterogeneous catalytic gas-phase reactions at pressures up to 30 bar and temperatures up to 300°C, which is connected to a mass spectrometer for online product analysis. The performance of the cell has been tested in three types of CO2 hydrogenation reactions (CO2 Fischer-Tropsch synthesis, CO2 methanation, CO2 conversion to dimethyl ether) on various solid catalysts implemented as self-supporting wafers. Catalytic data obtained with this cell showed the same trends as those measured in a fixed-bed plug-flow reactor, thus confirming their reliability. More information can be found in the Full Paper by Jane Weiß et al.

Advanced Study of Promoted Pt /SAPO-11 Catalyst for Hydroisomerization of the n-Decane Model and Lube Oil

SAPO-11 is synthesized from silicoaluminophosphate in the presence of di-n-propylamine as a template. The results show that the sample obtained has good crystallinity, 396m2/g BET surface area, and 0.35 cm3/g pore volume. The hydroisomerization activity of (0.25)Pt (1)Zr (0.5)W/SAPO-11 catalyst was determined using n-decane and base oil. All hydroisomerization experiments of n-decane were achieved at a fixed bed plug flow reactor at a temperature range of 200-275°C and LHSV 0.5-2h-1. The results show that the n-decane conversion increases with increasing temperature and decreasing LHSV, the maximum conversion of 66.7 % was achieved at temperature 275°C and LHSV of 0.5 h-1. Meanwhile, the same catalyst was used to improve base oil specification by increasing viscosity index and decreasing pour point. The isomerization reaction conditions, employed are temperature (200-300)ºC, the liquid hourly space velocity of 0.5-2h-1, and the pressure kept atmospheric. The present study shows that Pt Zr W/SAPO-11 minimizes the pour point of lubricating oil to -16°C at isomerization temperature of 300°C and LHSV of 0.5 h-1 and viscosity index 134.8.

Thiophene HDS on La-Modified CoMo/Al2O3 Sulfided Catalysts. Effect of Rare-Earth Content

Alumina-lantana (2.5, 5, 7.5 and 10 wt% La) mixed oxides of suitable texture to be applied as supports of catalysts for hydrodesulfurization of FCC naphtha-range oil-derived distillates were prepared by rare-earth pore-filling impregnation through corresponding nitrate. Co, Mo and P were deposited on binary carriers by one-pot simultaneous impregnation method used during commercial hydrotreating catalysts preparation. Materials were characterized by N2 physisorption, XRD, SEM–EDS, adsorbed CO2 FTIR (basicity measurements), Raman and UV–vis spectroscopies. Sulfided catalysts were studied by chemical composition (EDAX) and HR-TEM. In general, amount and strength of surface basic sites increased with rare-earth content in binary carriers at 5 wt% and higher. Deposited molybdates dispersion augmented with lanthanum content in carriers. However, progressively increasing rare-earth loading on supports was detrimental on gas-phase thiophene HDS (523–563 K, steady-state fixed-bed plug-flow reactor operating at atmospheric pressure). Hardly sulfidable tetrahedral Mo species could be originated by decomposition of heteropolymolybdates originally present in one-pot acidic (pH ~ 1.9) Co–Mo–P solutions by impregnating at basic conditions in pores of La-modified carriers. At isoconversion (~ 10%) rare-earth containing sulfided CoMo catalysts had decreased yield to fully saturated n-butane as to the material supported on pristine alumina.

Surface Modification of Nanocrystalline Zeolite X and Its Application as Catalyst in Synthesis of Cumene in a Packed Bed Flow Reactor: A Kinetic Study

AbstractIn the present investigation, synthesis of cumene by transalkylation of 1, 4 DIPB with benzene was studied over cerium modified nano crystalline zeolite X in a fixed bed plug flow reactor. Nano crystalline zeolite X was synthesized and characterized by XRD, SEM, TPD, EDS and FTIR. A series of nanocrystalline zeolite X (MX4, MX6, MX10) modified with ceric ammonium nitrate of different concentrations (4 %, 6 %, 10 %) was used for synthesis of cumene. MX10zeolite was proved to be the most active catalyst over which 27.12 % yield of cumene was obtained at temperature 553K, benzene/1, 4 DIPB mole ratio of 7.5 and space time-10.54 kg h/kmol. Reduction of crystal size (100–500 nm) in MX10increases surface area (633m2/gm) and thereby increases cumene yield. A kinetic rate equation was developed from the product distribution pattern following Langmuir–Hinshelwood approach. Kinetic parameters were estimated by nonlinear regression analysis. The activation energy for transalkylation and isomerisation reaction was found to be 88.86 kJ/mol and 99.04 kJ/mol respectively.

Glycerol steam reforming over modified Ru/Al2O3 catalysts

Glycerol, a by-product of biodiesel industry, could be utilized for the production of hydrogen via steam reforming. In the present work, three Ru-based catalysts, namely Ru/Al2O3, Ru/Β2Ο3-Al2O3 and Ru/MgO-Al2O3, have been studied regarding their physicochemical and catalytic properties for the title reaction. N2 adsorption-desorption, powder XRD, CO Adsorption, NH3-TPD, CO2-TPD, TPR, TEM and SEM-EDS were employed to investigate the textural and structural characteristics of the catalysts. Quantitative assessment of the carbonaceous deposits, formed under reaction conditions, was performed using TPH and TPO methods The catalytic performance of the synthesized catalysts for the glycerol steam reforming reaction has been investigated in a fixed bed plug flow reactor using a feed of water/glycerol at a molar ratio of 20:1 at 400, 500 and 600°C. Results show that at the low reaction temperature (400°C), the support has a determining role on the catalytic performance, the selectivity to various oxygenates depending on the acid-base properties of the catalyst. At higher temperature (600°C) metal activity dominates, H2 and CO2 being the main reaction products.

Roles of nitrogen species on nitrogen-doped CNTs supported Cu-ZrO2 system for carbon dioxide hydrogenation to methanol

Cu-ZrO2 catalysts supported on nitrogen-doped CNTs were tested for CO2 hydrogenation to methanol in a fixed-bed plug flow reactor. The characterization results indicate that the presence of pyridinic nitrogen increases the copper oxide dispersion, promotes their reduction, decreases the Cu particle size and enhances H2 adsorption capability; the activated CO2 adsorption predominantly controls CO2 conversion. In addition, pyridinic nitrogen contributes to the strong adsorption of CO2, stimulating methanol formation, while pyrrolic nitrogen contributes to the medium adsorption of CO2, mainly boosting CO formation. Thus, pyridinic nitrogen dominant CNTs supported catalyst (CZ/CNT-N) possesses more active sites compared with the other three catalysts, leading to maximum methanol yield (8.64%) and space time yield (102.21mgg−1cath−1); pyrrolic nitrogen dominant CNTs supported catalyst (CZ/CNT-NH2) obtains more highly active structure, giving the highest intrinsic activity (TOF values).

Preparation of a raspberry ketone precursor in the presence of rare earth oxide catalysts

The raspberry precursor 4-(4-hydroxyphenyl)-but-3-ene-2-one which afterwards undergoes a catalytic hydrogenation to produce raspberry ketone was synthesized by aldol condensation of acetone and 4-hydroxybenzaldehyde over rare earth oxides as basic catalysts and supported rare earth oxides as acid–base bifunctional catalysts. Thereby, several rare earth metal oxides were tested in their neat form as well as supported on carriers with high surface areas such as alumina, titania, tetragonal zirconia and charcoal. The catalysts were characterized by XRD, BET, NH3/CO2-TPD and pyridine-FTIR. All experiments were carried out batch wise in 75ml autoclaves adjusting molar ratios of acetone and 4-hydroxybenz-aldehyde from 12:1 to 4:1, temperature range from 80 to 200°C and autogeneous pressures from 1 to 25bar. It could also be realized, that titania and alumina are no inert materials, but also highly active catalysts for this reaction. An experimental design program was used to optimize the reaction conditions as well as the conversion and selectivity. In addition the reaction was carried out in a fixed bed plug flow reactor to determine stability and robustness of the catalyst. The quality/contaminations of the starting material have a strong influence on the catalytic performance.

Deoxygenation and cracking of free fatty acids over acidic catalysts by single step conversion for the production of diesel fuel and fuel blends

Gas phase deoxygenation of oleic acid was accomplished over palladium containing acidic catalysts under solvent-free conditions. Aluminum oxide catalysts were prepared out of three different boehmite precursors by calcination at different temperatures between 500°C and 1100°C forming different aluminum oxide phases. All catalysts were impregnated with 1wt.% palladium and subsequently tested for their deoxygenation performance either batch wise in autoclaves or continuously in a fixed bed plug flow reactor or in a trickle bed reactor. Conversion of oleic acid and selectivity to the desired diesel-like C17 hydrocarbons heptadecane and heptadecenes were studied with the best aluminum oxide found in the catalyst screening at different reaction temperatures, catalyst amounts and palladium amounts on the catalyst. Using boehmite found as best alumina precursor, different mixtures of such aluminum oxide with zeolites were prepared in order to increase the catalyst acidity and thus the deoxygenation performance. The optimum reaction conditions found for aluminum oxide catalysts were applied for the screening of these composite catalysts. Using the best composite catalyst, the effect of hydrogen dilution with nitrogen, the addition of water and catalyst regeneration by thermal treatment was tested. In addition catalyst containing silica aluminates doped with 1wt.-% Pd were prepared and tested for their catalytic activity in deoxygenation and cracking of free fatty acids. Some reactions were conducted under elevated hydrogen pressure. The catalysts were characterized by nitrogen adsorption isotherms (BET), temperature programmed desorption of ammonia (TPD), X-ray powder diffraction (XRD), thermo gravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM).

Anchoring Au Nanoparticles onto ZnO Nanowires by Heteroepitaxy

ZnO NWs were fabricated by a thermal evaporation-condensation method in a high-temperature tube furnace. The 2wt%Au/Zn Onanocatalysts were prepared by a deposition-precipitation method. The ZnO NW and powder supported Au catalysts are labeled as Au/ZnO-NW and Au/ZnO-P, respectively. The final catalysts were obtained by calcining the precursors at 400°C for 4 hours. The 5wt%Au/ZnO nanocatalysts calcined at 600°C were synthesized for XRD analysis. The catalytic performances of the prepared samples for CO oxidation were evaluated in a fixed-bed plug-flow reactor. Powder X-ray diffraction (XRD) patterns were taken on a PANalyticalX’pert PRO MRD X-ray diffractometer using Cu Ka radiation. The JEOL JEM-ARM200F aberration-corrected scanning transmission electron microscope (STEM), with a nominal image resolution of 0.08 nm in the high-angle annular dark-field (HAADF) imaging mode, was used to investigate the structure of the Au/ZnO catalysts.

Cross ketonization of Cuphea sp. oil with acetic acid over a composite oxide of Fe, Ce, and Al

The objective of this work was to demonstrate the viability of the cross ketonization reaction with the triacylglycerol from Cuphea sp. and acetic acid in a fixed-bed plug-flow reactor. The seed oil from Cuphea sp. contains up to 71% decanoic acid and the reaction of this fatty acid residue with acetic acid yields the fragrance compound and insect repellent 2-undecanone. To this end, we screened several ketonization catalysts taken from the literature including CeO2, CeO2/Al2O3, CeO2/ZrO2, MnOx/Al2O3. The catalysts were characterized by N2 adsorption/desorption, H2-TPH, CO2-TPD, and XRD. Each of these catalysts affected the conversion but the highest yield was found with a new coprecipitated mixed metal oxide of empirical formula Fe0.5Ce0.2Al0.3Ox. In a flow reactor, Fe0.5Ce0.2Al0.3Ox gave 2-undecanone at 91% theoretical yield with reaction conditions of 400°C, weight hourly space velocity of 2, molar ratio of acetic acid to Cuphea oil of 23, and N2 carrier gas flow of 125ml/min at 2.4bar. This high yield is attributed to the low rate of coke formation on the mixed metal catalyst. In the absence of acetic acid, coupling of the decanoic acid residues gives 10-ketononadecane.

Preferential oxidation of CO in hydrogen stream over nano-gold catalysts prepared by photodeposition method

A series of gold catalysts supported on TiO 2 were prepared by photodeposition method. The effects of preparation parameters, such as power of UV light, irradiation time, and initial gold concentration, on the characteristics of the catalysts were studied. The catalysts were characterized by inductively coupled plasma-mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, and high-resolution transmission electron microscopy. The catalytic activity of the catalyst for preferential oxidation of CO in hydrogen stream (PROX) was measured in a fixed-bed plug-flow reactor. The reactant gas containing 1.33% CO, 1.33% O 2, 65.33% H 2 and He for balance was fed into the reactor with a space velocity of 30,000 ml/g h. The lower power source lamp can deposit small gold particles on the support, which in turn was responsible for the enhanced catalytic activity. The photodeposition method facilitates to prepare gold particles as small as 1.5 nm on the support. These catalysts were very active and selective in PROX reaction. However, the small gold particles were not stable as long as the reaction temperature was > 50 ∘ C .

Determination of optimal temperature profile in an OCM plug flow reactor for the maximizing of ethylene production

An optimal temperature profile for achieving the highest amount of ethylene production in a fixed bed plug flow reactor of oxidative coupling of methane (OCM) was determined and analyzed from chemical reactions point of view. A performance index was defined to solve the problem and the optimal temperature profile was found by means of “piecewise linear continuous optimal control by dynamic programming” (PLCOCIDP) algorithm. The performance obtained from the optimal temperature profile was compared with the best isothermal performance of the reactor, gained from optimization calculations. It was concluded that the quantity of ethylene production by applying the optimal temperature profile is about 42% greater than that of the best isothermal performance of the reactor at 1096.3 K. It was also observed that maximization of ethylene production and minimization of carbon dioxide production are interrelated in this system. The effects of total pressure and initial oxygen concentration were studied as well. The optimal temperature profile spread out and its minimum point rose a little with increasing the concentration of oxygen and/or decreasing the total pressure. Moreover, when the total pressure or initial oxygen mole fraction was elevated, the ethylene molar flux increased, however the selectivity of ethylene reduced in case of increasing the oxygen molar flux.

Investigation of simultaneous adsorption of SO 2 and NO x on Na-γ-alumina with transient techniques

The simultaneous adsorption of SO 2 and NO x on Na-γ-alumina was studied by means of step experiments in a fixed bed plug flow reactor at 387 K and atmospheric pressure. Typically the molar composition of the feed gas was 1.5% SO 2, 1% O 2, 4000 ppm NO, 500 ppm NO 2, and Ar. First the adsorption behavior of the pure components was measured. SO 2 and NO 2 adsorb easily, whereas NO and O 2 do not adsorb. Moreover there is no influence of O 2 on the adsorption behavior of the pure components. NO and O 2 adsorption require the simultaneous presence of SO 2, NO, and O 2. The NO and O 2 adsorption rate is enhanced by an increasing SO 2/NO ratio. The total amount of SO 2 adsorbed is not affected by the simultaneous adsorption of NO and O 2. However, NO 2 adsorption increases the SO 2 adsorption capacity. In the presence of NO 2 most of the adsorbed NO x is released as NO.

Chlorinated alumina as an alkylation catalyst: influence of superficial HCl

Chlorinated alumina catalysts were obtained by reacting gamma-alumina with gaseous CCl4 or hydrogen chloride under various conditions. They had chlorine contents between 4 and 6% by weight, and differed in surface acidity. They were tested as catalysts for the alkylation of isobutane with 2-butene using a fixed bed plug flow reactor. Alumina reacted with CCl4 was found inefficient for this reaction. However, the solid chlorinated with HCl above 800 K was able to catalyze alkylation at a temperature as low as 273 K. Moreover, the CCl4-reacted solid could be activated upon further treatment with HCl at moderate temperatures (370 to 550 K). However, the catalytic activity decays after a few hours on stream. The composition of the alkylate varied somewhat with time on stream: large amounts of cracked products appeared during the initial period, after which the selectivity to trimethylpentanes (TMP) was comparable to that of other solid catalysts. The presence of hydrogen chloride bound to the catalyst surface was established by measuring the temperature-programmed desorption (TPD) of HCl from the various Al2O3–Cl. For the active catalysts, desorption started at temperatures (350–400 K) well under those for the CCl4-treated sample, but all solids continuously released HCl above 650 K. Thus, HCl interacts with particular Lewis acid sites of Al2O3–Cl, and creates the strong Brønsted sites required for catalytic alkylation.

Elucidation of Lean-NOxReduction Mechanism Using Kinetic Isotope Effect

The effect of an NO isotope on the kinetics of lean-NOx catalysis in (NO+C2H4+O2) reaction mixtures over Pt-ZSM-5 was theoretically analyzed and compared with experimental data obtained with a fixed-bed plug-flow reactor. The large kinetic isotope effect, as well as kinetic oscillations observed previously, was explained by NO decomposition kinetics on Pt surfaces which undergo phase transition between (1×1) and (hex) phases induced by adsorbed reactant species. Results indicate the importance of NO decomposition kinetics in lean-NOxcatalysis, lending further support to a lean-NOxreduction mechanism which involves NO decomposition accompanied by hydrocarbon oxidation.

Generalized treatment of concentration forcing in fixed-bed plug-flow reactors

A generalized treatment is presented for several basic types of reaction conducted in a fixed-bed plug-flow reactor (FBPFR) under conditions of forced periodic oscillations of feed compositions. The model reactions are adsorption-desorption types with Eley-Rideal surface kinetics. For nonlinear kinetics, there is a significant improvement in the time-averaged production rate relative to optimal steady-state operation. For linear kinetics, there is no improvement.