Adsorption Of Propane Research Articles

Nonmetal oxygen vacancies confined under boron nitride for enhanced oxidative dehydrogenation of propane to propene

In heterogeneous catalysis, oxygen vacancies of metal oxides play a key role by modulating properties of coordination, electron states, electrical conductivity, and surface property. However, the investigation of oxygen vacancies in nonmetal oxides and their catalytic applications have rarely been reported. Here, we present oxygen vacancies-rich BPO4 hollow spheres covered by few-layer hexagonal boron nitride (BN) with a sandwich-like structure (BN@BPO4@BN) through an in-situ growth method. The as-prepared catalyst showed better catalytic activity and higher selectivity than that of commercial BN in the oxidative dehydrogenation of propane to propene because of the synergetic effect between oxygen vacancies-rich BPO4 and h-BN. Oxygen vacancies increase the adsorption amount of propane and the confined space at the interface of BN and BPO4 weakens the adsorption of propene, beneficial for the recycle of active sites. Moreover, the confined space and oxygen vacancies result in the transformation of reaction kinetic model.

Catalytic combustion of propane on Pd-modified Al–La–Ce catalyst – from reaction kinetics and mechanism to monolithic reactor tests and scale-up

Abstract A propane combustion catalyst was prepared by supporting of Pd on optimized multiphase composition, containing Al2O3, La2O3 and CeO2 aiming for possible application in catalytic converters for abatement of propane in waste gases. The catalyst characterization has been made by N2- physisorption, XRD, SEM/EDX, TEM and XPS. The obtained values for reaction order towards propane and oxygen are 0.57 and 0.14, respectively. The negative reaction order towards the water vapour (−0.26) shows an inhibition effect of the water molecules. According to the kinetics model calculations, the reaction pathway over Pd-modified La–Ce catalyst proceeds most probably through Langmuir–Hinshelwood mechanism with adsorption of propane and oxygen on different types of sites, dissociative adsorption of oxygen, whereupon water molecules compete with propane molecules for one and the same type of adsorption sites. For practical evaluation of the synthesized material, a sample of Pd/Al2O3–La2O3–CeO2, supported on rolled Al-containing stainless steel (Aluchrom VDM®) to form a single monolithic channel was prepared and tested. Two-dimensional heterogeneous models were used to simulate the propane combustion from laboratory reactor to full-scale adiabatic monolithic converter for ensuring an effective abatement of propane emissions.

All-silica DD3R zeolite for adsorptive separation of propylene from propane: Equilibrium and kinetic data

Abstract Propylene/propane separation by adsorption is an energy-efficient process which is considered as an alternative for energy-intensive separation by cryogenic distillation. The main part of the adsorption process is the design of an efficient adsorbent. All-silica DD3R zeolite is a special adsorbent for the proposed process. In this paper, two different sizes of that zeolite are synthesized. Adsorption isotherms of propylene were experimentally measured on large DD3R zeolite crystals (~12 μm) at 303–423 K and up to 1000 kPa. Due to the very slow adsorption kinetics of propane, full equilibrium was not reached on large-sized DD3R crystals and even on small crystals (~2 μ m) after 3.5 days at 303 K. However, for the first time, real propane adsorption isotherms have been successfully measured on small-sized DD3R particles at higher temperatures, i.e., 373–473 K, up to 500 kPa. Experimental adsorption kinetics of propylene and propane were tested at various pressures and temperatures, and finally the diffusion coefficients were predicted. The investigation revealed that diffusivities increase with both pressure and temperature. Estimated high values of propylene/propane kinetic selectivities, i.e., 9.76 × 103 and 3.66 × 103 at 373 and 423 K at 80 kPa, respectively, revealed that DD3R zeolite is a superior kinetic-based adsorbent for propylene/propane separation.

Effect of porous structure of coal on propylene adsorption from gas mixtures

This paper addresses the issue of the sorption process on coal concerning propylene released from the source of coal heating in the deposit. In this study, the interaction between Polish coals and propylene molecules, as well as three other hydrocarbons (ethylene, ethane, and propane) with the application of a fixed-bed column, was investigated. The experimental results show that propylene adsorption was measurable under the experimental conditions. The differences in the amount of adsorbed propylene were predominately caused by various gas diffusion rates within the pore network associated with the molecular sieving effect. According to the experimental results, the influence of mesopores on propylene adsorption was significantly stronger than the share of micropores of the explored coals. The column tests demonstrated that the largest amount of propylene was adsorbed by coal with the highest value of pore diameter (6.48 nm) determined by nitrogen adsorption at 77 K. Under the experimental conditions, the influence of other hydrocarbons and a surface area on the quantity of the adsorbed gas was unnoticeable. This study provides an understanding of the behavior of some of the fire gases during the flow of the mixture through a heterogeneous structure of coal in the mine environment. The sorption of gases from multi-component mixture released during the self-heating of coal on carbon materials such as bituminous and lignite coals is poorly understood which provides the rationale for the topic of this work.

Photocatalytic Oxidation of Propane Using Hydrothermally Prepared Anatase-Brookite-Rutile TiO2 Samples. An In Situ DRIFTS Study.

Photocatalytic oxidation of propane using hydrothermally synthesized TiO2 samples with similar primary crystal size containing different ratios of anatase, brookite and rutile phases has been studied by measuring light-induced propane conversion and in situ DRIFTS (diffuse reflectance Fourier transform infrared spectroscopy). Propane was found to adsorb on the photocatalysts, both in the absence and presence of light. The extent of adsorption depends on the phase composition of synthesized titania powders and, in general, it decreases with increasing rutile and brookite content. Still, the intrinsic activity for photocatalytic decomposition of propane is higher for photocatalysts with lower ability for propane adsorption, suggesting this is not the rate-limiting step. In situ DRIFTS analysis shows that bands related to adsorbed acetone, formate and bicarbonate species appear on the surface of the photocatalysts during illumination. Correlation of propane conversion and infrared (IR) data shows that the presence of formate and bicarbonate species, in excess with respect to acetone, is composition dependent, and results in relatively low activity of the respective TiO2. This study highlights the need for precise control of the phase composition to optimize rates in the photocatalytic oxidation of propane and a high rutile content seems to be favorable.

The effect of supported Rh, Ru, Pt or Ir nanoparticles on activity and selectivity of ZrO2-based catalysts in non-oxidative dehydrogenation of propane

A series of catalysts on the basis of ZrO2, LaZrOx and YZrOx with supported Rh, Ru, Pt or Ir nanoparticles (NPs) were prepared. They were tested in the non-oxidative dehydrogenation of propane (PDH) to elucidate the effects of (i) the kind of supported metal and its loading, (ii) the size (1 nm or 5 nm) of NPs, (iii) metal oxide promoter for ZrO2 and (iv) reaction temperature on PDH performance. Although the metals did not directly participate in propene formation, they improve catalyst activity through (i) promotion of Zrcus (cus means coordinatively unsaturated) formation and (ii) acceleration of hydrogen formation. The kind of metal was also established to be decisive for propene adsorption. The latter property has a negative effect on catalyst activity and propene selectivity. The most active Rh/YZrOx catalyst with 0.05 wt% Rh revealed about 1.6 times higher propene formation rate than a commercial-like K-CrOx/Al2O3 or the state-of-the-art Ru/YZrOx.

Surface modification of macroporous La0.8Sr0.2CoO3 perovskite oxides integrated monolithic catalysts for improved propane oxidation

Perovskite oxides have emerged as promising alternatives for the supported Platinum group metal catalysts for total oxidation of propane and other volatile organic compounds (VOC). Here, we report a surface modification method to improve propane oxidation activity of La0.8Sr0.2CoO3 monolithic catalysts using diluted oxalic acid etching. The oxalic acid treatment decreases the light-off temperatures of propane oxidation by 30–40 °C. Experimental and DFT investigations reveal that the treatment selectively etches Sr cations and slightly reduces LSCO surface, leading to an increased population of low-valence Co2+ Lewis acid sites, which promotes activation of lattice oxygen and adsorbed oxygen species and facilitates propane adsorption and dissociation. Our work offers a rapid strategy to activate perovskite monolithic catalysts and will inspire the research on surface modification of perovskite catalyst.

A New Method for the Measurement of the Diffusion Coefficient of Adsorbed Vapors in Thin Zeolite Films, Based on Magnetoelastic Sensors.

In the current work an experimental method is used in order to calculate the diffusivity (diffusion coefficient) of various vapors in thin zeolite films. The method is based on adsorption data from magnetoelastic sensors on top of which a zeolite layer was synthesized, and the diffusivity is extracted by fitting the data to Fick’s laws of diffusion. In particular, the method is demonstrated for two volatile organic compound (VOC) vapors on two different zeolites, the p-Xylene adsorption in Faujasite type zeolite with at and the propene adsorption in Linde Type A type zeolite with at , two diffusion coefficients which are extracted experimentally for first time. Our results are within the order of magnitude of other VOC/zeolite values reported in literature.

A comparative study of silver- and palladium-exchanged zeolites in propylene and nitrogen oxide adsorption and desorption for cold-start applications

Silver and palladium ion-exchanged BEA zeolites (Si/Al = 12.5) and silver ion-exchanged ZSM-5 zeolites (Si/Al = 15) were studied for their ability to adsorb and desorb propylene and NO under simulated diesel exhaust conditions. The adsorption experiment results demonstrated the excellent ability of bare BEA zeolites to adsorb propylene, but only a small amount of NO. The presence of H2O inhibited the adsorption of both C3H6 and NO. Ion-exchanging BEA zeolites with Ag (1.2 and 5.1 wt.% Ag/BEA) attenuated the inhibiting effect of H2O on C3H6 adsorption, while NO storage remained inhibited. Adsorption experiments indicated that C3H6 and NO competed with each other for Pd sites with C3H6 showing stronger adsorption compared to NO, whereas Ag sites preferentially adsorbed C3H6. DRIFTS data indicated the formation of nitrate, formate and acetate species on Ag and Pd, while C3H6 and NO adsorption was also observed on the zeolite hydroxyl groups in the absence of H2O. However, the C3H6 and NO adsorption on the zeolite hydroxyl groups was significantly inhibited in the presence of H2O. Additionally, nitrosyl, acrolein and carbonate species were formed over 1.0 wt.% Pd/BEA. The effluent analysis during the temperature-programmed desorption in the DRIFTS reactor revealed that adsorbed C3H6 and NO reacted during the release to form oxidation reaction byproducts. The 1.0 wt.% Pd/BEA zeolite showed the greatest oxidation ability during desorption with the majority of stored C3H6 converted to CO2.

Preferential Adsorption of Propylene over Propane on a Ag-Exchanged X-Type Zeolite Membrane.

We investigated the adsorption properties of propylene and propane on an olefin-selective Ag-X membrane and discussed the contribution of adsorption selectivity to propylene/propane separation performance through this membrane. The isotherms of propylene and propane on Ag-X membranes were measured in unary systems at 313 K. The amount of propylene adsorbed on the Ag-X membrane at a lower pressure increased remarkably compared with that on the Na-X membrane. Such a change of adsorption property could induce excellent separation property for the Ag-X membrane. We compared the adsorption properties in a binary system calculated based on the Markham-Benton approach with the results of a permeation test. The molar fractions of propylene in the adsorbed phase in the binary system provided good agreement with propylene purity on the permeation side of the Ag-X membrane. These results clearly show that permeation selectivity of the Ag-X membrane for the propylene/propane mixture is mainly governed by adsorption selectivity.

C2/C3 Hydrocarbon Separation by Pressure Swing Adsorption on MIL-100(Fe)

The main objective of this work is the separation of 0.30/0.70 ethane/propane and 0.30/0.70 ethylene/propane by pressure swing adsorption (PSA) on MIL-100(Fe). The metal–organic framework MIL-100(Fe) was proposed as a potential adsorbent due to its high C2/C3 selectivity. Since adsorption equilibrium data are essential for the process design, the adsorption isotherms of ethane, ethylene, and propane were measured at 323, 373, and 423 K by a gravimetric method. Fixed-bed experiments were conducted at 0.5 SLPM, 323 K, and 150 kPa feed conditions on a bench-scale vacuum PSA (VPSA). Equilibrium and dynamic studies confirmed the preferential adsorption of propane over ethane and ethylene, with a high adsorption separation factor. Two five-step VPSA cycles with two different feed compositions, 0.30 ethane/0.70 propane, and 0.30 ethylene/0.70 propane, at 323 K and 150 kPa on MIL-100(Fe) were designed and performed experimentally. The performance parameters demonstrated the high viability of the proposed processes, since ethane purity of 99.5% was achieved, and with a high ethane recovery (86.7%). In the same cycle, 99.4% of propane was recovered with 97.0% purity. In cycle scheme 2, an ethylene purity of 100.0% was achieved. The propane was 100% recovered with a purity of 94.7%.

Three-dimensionally macroporous MnZrOx catalysts for propane combustion: Synergistic structure and doping effects on physicochemical and catalytic properties

Three-dimensionally macroporous (3DM) MnZrOx catalysts were fabricated to reveal the structure and Zr-doping effects on both physicochemical properties and propane combustion behaviors. The increasing addition of zirconium is favorable for the formation of 3DM structure and amorphous Mn-Zr solid solution, leading to tunable physicochemical properties. The significant activity improvement after zirconium addition was originally attributable to the superior redox ability, higher oxygen mobility and more abundant oxygen vacancy. The excellent catalytic activity, cycling stability and water resistant ability over 3DM Mn0.6Zr0.4Ox make it a promising material for hydrocarbons elimination. The comparative TPSR, in situ DRIFTs and kinetics study over 3DM and bulk catalysts emphasize the advantageous function of 3DM architecture on promoting propane adsorption, oxidation and lattice oxygen mobility.

Room-Temperature Propylene Dehydrogenation and Linear Atomic Chain Formation on Ni(111)

The structures formed by propylene adsorption on Ni(111) at room temperature are determined by a combination of scanning tunneling microscopy and density functional theory. As a result of the interaction with the Ni(111) surface, propylene molecules are dehydrogenated and coupled into linear hydrocarbon chains. The length of the chains varies from 8 to 60A, with the most frequently observed length of 18A. At saturated coverage, some chains are closed in rings with a diameter of 6A. A C12H12 model is proposed for most often observed chains. We demonstrate that the possibility of combining initial propylene molecules into chains appears after dehydrogenation of the CH3 fragment.

Electrically heated catalyst device

The performance of the MIL-101(Cr) loaded with cuprous oxide (Cu2O) nanoparticles was evaluated in both equilibrium and kinetic conditions for adsorption of propane and propylene via volumetric method. The single-component adsorption isotherms were measured at temperatures of 303, 323, 343 and 363 K and pressures up to 400 kPa. To correlate the experimental isotherm data points, temperature-dependent Sips model was applied, which exhibited high accuracy of prediction. The synthesized samples were characterized by XRD, BET, FE-SEM, EDS mapping and TEM techniques. The binary mixture adsorption behavior and selectivity of propane/propylene were calculated by using the ideal adsorbed solution theory (IAST). Obtained results showed that by increasing the loading of Cu2O nanoparticles up to 15 wt%, the propylene selectivity of MIL-101(Cr) was enhanced from 1.5 to 12.2 at 100 kPa and 303 K. Moreover, the optimum performance in terms of both adsorption capacity and selectivity was achieved using 12%[email protected](Cr) sample. Fast diffusion of the adsorbates, obtained by accurate fitting of the isothermal micropore model to the uptake curves data, along with reusability suggest the 12%[email protected](Cr) as a promising adsorbent for effective separation of propane/propylene mixture.

Hierarchical zeolite enveloping Pd-CeO2 nanowires: An efficient adsorption/catalysis bifunctional catalyst for low temperature propane total degradation

Abstract Volatile organic compounds (VOCs) are significant ozone (O3) and particulate matter (PM) formation precursors and are deleterious to both human health and environment. Catalytic combustion can degrade VOCs to H2O and CO2 without secondary pollution, suggesting a potential sustainable technology for air pollution control. However, the concentration of exhausted VOCs is usually too low for effective decomposition. Herein, a novel adsorption/catalysis bifunctional catalyst, hierarchical silicalite-1 (S-1) zeolite enveloping Pd-CeO2 nanowires (Pd-CeO2NW@S-1), was designed and prepared using a simple one-pot two-step method and applied for the degradation of propane. Pd-CeO2NW@S-1 exhibited superior catalytic activity (T90 decreased to 296 °C) as well as increased thermal and hydrothermal stability (no obviously decrease in activity when treated at 700 °C or reacted with water gas, respectively) compared with Pd-CeO2 nanowires supported on the outer surface of S-1 (Pd-CeO2NW/S-1) and previously reported Pd based catalysts for propane degradation. In addition, the activity over Pd-CeO2NW@S-1 after five reaction cycles just with little decrease and could be restored by a simple regeneration step and without any detection of coke. The remarkable performance over Pd-CeO2NW@S-1 was attributed to the high dispersion of Pd and Ce encapsulated in hierarchical zeolite with superior propane adsorption performance and the special confinement structure according the Mars-van-Krevelen (MvK) mechanism. This confinement adsorption/catalysis bifunctional strategy can be used to design other high-performance catalysts for degradation of VOCs.

Propane-selective design of zirconium-based MOFs for propylene purification

Separating propane from propylene is a significant challenge in petrochemical industry. Rational chemistry design of the propane-selective adsorbent has not been reported. This work demonstrates the first design of propane-selective adsorbents. Two strategies based on surface chemistry tuning, namely compositing 2D g-C3N4 and replacing ligand, have been proposed to yield the propane-selective g-C3N4@Zr-BPDC (BPDC = biphenyl-4,4′-dicarboxylate) and Zr-BPYDC (2,2′-bipyridine 5,5′-dicarboxylate). Whereas g-C3N4@Zr-BPDC has a high propane capacity of 8.79 mmol/g at room temperature and ambient pressure, Zr-BPYDC exhibits superior propane/propylene selectivity. The isosteric heat of propane and propylene adsorption on both adsorbents is lower than that of most reported adsorbents, indicating facile regeneration of the adsorbents. DFT calculations suggest the propane-selectivity comes from multiple CHδ+⋯Nδ− interactions between propane and nitrogen atoms of the adsorbents. Moreover, both adsorbents produce polymer-grade propylene through a one-step separation using a packed column, facilitating the energy-effective production of polymer grade propylene under ambient conditions.

Separation of ethane-ethylene and propane-propylene by Ag(I) doped and sulfurized microporous carbon

Abstract Separation of light olefins from their respective paraffins by adsorption is an attractive strategy due to the sustainable and inexpensive nature of adsorption process. It is well understood that the presence of Ag(I) in the adsorbent favors the adsorption of ethylene and propylene (olefins) over ethane and propane (paraffins) owing to the π - π complexation between Ag(I) and π bond present in olefins. In this research, Ag(I) doped microporous carbons were synthesized from furfuryl alcohol as carbon source. It is also shown that prior sulfurization of the carbon greatly favored Ag(I) content owing to the affinity of sulfur to Ag(I). All the carbons were successfully characterized with pore textural properties, SEM-EDX imaging and x-ray photoelectron spectroscopy (XPS). Only the carbon with highest Ag(I) content (2.5 at.%) and BET specific area (1193 m2/g) favored the adsorption of ethylene and propylene over ethane and propane, respectively. IAST-based selectivity values were also employed to calculate binary adsorption isotherms for ethane-ethylene and propane-propylene mixtures. The IAST-based selectivity values of ethylene/ethane and propylene/propane were in the range of 4.5 to 2.5 and 5 to 2.4, respectively. Finally, column breakthrough and pulse chromatographic peaks were simulated to confirm the separation of paraffin-olefin pairs on thus carbon. To the best of our knowledge, it is the first report of the separation of light paraffin and olefins in a carbon-based adsorbent and by harnessing the π - π complexation.

Insight into catalytic properties of Co3O4-CeO2 binary oxides for propane total oxidation

A series of Co3O4-CeO2 binary oxides with various Co/(Ce+Co) molar ratios were synthesized using a citric acid method, and their catalytic properties toward the total oxidation of propane were examined. The activities of the catalysts decrease in the order CoCeOx-70 > CoCeOx-90 > Co3O4 > CoCeOx-50 > CoCeOx-20 > CeO2. CoCeOx-70 (Co/(Ce+Co) = 70% molar ratio) exhibits the highest catalytic activity toward the total oxidation of propane, of which the T90 is 310 °C (GHSV = 120000 mL h−1 g−1), which is 25 °C lower than that of pure Co3O4. The enhancement of the catalytic performance of CoCeOx-70 is attributed to the strong interaction between CeO2 and Co3O4, the improvement of the low-temperature reducibility, and the increase in the number of active oxygen species. In-situ DRIFTS and reaction kinetics measurement reveal that Ce addition does not change the reaction mechanism, but promotes the adsorption and activation of propane on the catalyst surface. The addition of water vapor and CO2 in reactant gas has a negative effect on the propane conversion, and the catalyst is more sensitive to water vapor than to CO2. In addition, CoCeOx-70 exhibits excellent stability and reusability in water vapor and CO2 atmosphere.

Separation of propane/propylene mixture using MIL-101(Cr) loaded with cuprous oxide nanoparticles: Adsorption equilibria and kinetics study

The performance of the MIL-101(Cr) loaded with cuprous oxide (Cu2O) nanoparticles was evaluated in both equilibrium and kinetic conditions for adsorption of propane and propylene via volumetric method. The single-component adsorption isotherms were measured at temperatures of 303, 323, 343 and 363 K and pressures up to 400 kPa. To correlate the experimental isotherm data points, temperature-dependent Sips model was applied, which exhibited high accuracy of prediction. The synthesized samples were characterized by XRD, BET, FE-SEM, EDS mapping and TEM techniques. The binary mixture adsorption behavior and selectivity of propane/propylene were calculated by using the ideal adsorbed solution theory (IAST). Obtained results showed that by increasing the loading of Cu2O nanoparticles up to 15 wt%, the propylene selectivity of MIL-101(Cr) was enhanced from 1.5 to 12.2 at 100 kPa and 303 K. Moreover, the optimum performance in terms of both adsorption capacity and selectivity was achieved using 12%Cu@MIL-101(Cr) sample. Fast diffusion of the adsorbates, obtained by accurate fitting of the isothermal micropore model to the uptake curves data, along with reusability suggest the 12%Cu@MIL-101(Cr) as a promising adsorbent for effective separation of propane/propylene mixture.

CrO supported on high-silica HZSM-5 for propane dehydrogenation

Industrial propane dehydrogenation (PDH) catalysts generally suffer from low catalytic stability due to the coke formation onto the catalyst surface to cover the active sites. The exploitation of an efficient catalyst with both high catalytic selectivity and long-term stability toward PDH is of great importance but challenging to make. Herein CrOx supported on high-silica HZSM-5 with a SiO2/Al2O3 ratio of 260 (Cr/Z-5(260) is synthesized by a simple wet impregnation method, which exhibits high catalytic activity, good selectivity and excellent stability for PDH. At a weight hourly space velocity (WHSV) of 0.59 h−1, a propylene formation rate of 4.1 mmol gcat−1 h−1 (~ 32.6% propane conversion and ~ 94.2% propylene selectivity) can be maintained over the 5%Cr/Z-5(260) catalyst after 50 h time on stream, which is much better than commercial Cr/Al2O3 (Catofin process, catalyst life is several hours) at the same reaction conditions. With increasing the WHSV to 5.9 h−1, a high propylene formation rate of 27.9 mmol gcat−1 h−1 can be obtained over the 5%Cr/Z-5(260) catalyst after 50 h time on stream, demonstrating a very promising PDH catalyst. Characterization results and Na+ doping experiments reveal that the Cr species combined with Brønsted acid sites in Cr/HZSM-5 catalysts are responsible for the high catalytic performance. In particular, the Brønsted acid sites in HZSM-5 zeolite could increase the propane adsorption and enhance the CH bond activation. Furthermore, the high surface area and well-defined pores of HZSM-5 zeolite can provide a special environment for the dispersion and stabilization of Cr species, thus guaranteeing high catalytic activity and stability.