Propane Dehydrogenation Reaction Research Articles

Theoretical and experimental study on the dehydrogenation of propane by oxygen vacancy caused by γ-Al2O3 with the assistance of S

As a nontoxic and cheap catalyst, the Al2O3 catalyst can be used to catalyze the propane dehydrogenation (PDH) process. However, due to its poor activity, it has been used as a catalyst carrier rather than catalysis. In this work, the experimental results indicate that γ- Al2O3-(110)-S catalysts can improve the yield of propane dehydrogenation more effectively than γ-Al2O3-(110) catalyst. We investigate the potential barrier of propane dehydrogenation reaction catalyzed by Al2O3-(110) under different conditions and found that the substitution of the S atom for partial O atom can modify the acid-base properties of the surface active site of γ-Al2O3-(110), thus reducing the reaction energy barrier. In particular, the yield of the reaction can be further improved by the active sites of oxygen vacancies generated by removing partial S atoms in γ-Al2O3-(110)-S, which is consistent with our theoretical calculation results. At the same time, theoretical calculation shows that Cu clusters can effectively remove the S atoms on the surface of γ-Al2O3-(110)-S and form oxygen vacancies. This strategy provides a new path to form oxygen vacancies on γ-Al2O3-(110), which opens up a new way for the study of propane dehydrogenation.

Boosting the performances of protonic solid oxide fuel cells for co-production of propylene and electricity from propane by integrating thermo- and electro- catalysis

Protonic solid oxide fuel cells (p-SOFC) integrated with clean thermal energy sources are promising platforms for decarbonized chemical production in addition to power generation, such as on-purpose propylene production from propane dehydrogenation (PDH). The catalytic performance of the conventional nickel-cermet-based anode materials in p-SOFC for propane conversion is restrained by their low active surface area and proneness to coking. In this work, by integration of a highly efficient industry-relevant thermal catalyst PtGa/ZSM-5 for PDH reaction, we demonstrate that both the electrochemical and catalytic performance of the propane-fueled p-SOFC can be effectively enhanced. The PtGa catalyst integrated p-SOFC exhibits a peak power density of 93 mW cm−2 at 600 °C, which is greater by about 100% and 50% than that without catalyst or with a perovskite-based (Pr0.3Sr0.7)0.9Ni0.1Ti0.9O3 (PSNT) catalyst layer, respectively. The PDH activity and olefin selectivity of the PtGa catalyst is also significantly higher than that of the PSNT catalyst. In addition, much improved coke tolerance and propylene selectivity (over 90%) compared to the catalyst-free Ni-cermet anode materials were achieved by integrating the industrial catalyst layer. The propane conversion can be further improved by an applied current density, whereas the olefin selectivity is almost unaltered. The excellent performance of the PtGa catalyst integrated p-SOFC is attributed to the high surface area, intrinsically high catalytic activity, selectivity, and anti-coking properties of the catalytic layer for propane conversion. This work provides a general approach and a case study for boosting the performances of p-SOFCs in chemical production by integrating thermo- and electro- catalysis.

Role of oxygen transfer and surface reaction in catalytic performance of VOx-Ce1–xZrxO2 for propane dehydrogenation

The bulk oxygen transfer and surface reaction as important parts of the chemical looping-related process are crucial for the rational design of new redox catalysts. This paper describes an experimental study on the effect of bulk oxygen transfer and surface reaction in Ce1–xxO2 supported VOx redox catalysts for the chemical looping oxidative propane dehydrogenation reaction. It was found that the introduction of Zr dictates the reaction performance of the redox catalyst by modulating the bulk oxygen transfer and surface reaction. The kinetic study reveals that the instantaneous reduction rate of the redox catalysts is determined by the H-abstraction step in the surface reaction. The introduction of Zr can reduce the activation energy of the H-abstraction step, which leads to the enhancement of the instantaneous reduction rate. Meanwhile, the oxygen supply capacity of the cerium oxide is increased by Zr, allowing the surface reaction to proceed over longer durations. Furthermore, the reaction model derived from the kinetics study is validated using a number of (quasi) in situ techniques. This study provides fundamental insights into the role of bulk oxygen transfer and surface reaction in chemical looping or related process.

Constructing rich-Zn Pt1Zn1 alloy over the BEA zeolite as a selective catalyst for propane dehydrogenation

The deactivation of Pt-based catalysts is the most critical problem in nonoxidative propane dehydrogenation reaction (PDH), usually manifested in carbon deposition and active site sintering. Zn, as another cheap metal with more abundant reserves than Sn, is also widely used as an assistant in Pt-based catalysts. However, both of them are easy to be reduced to metal valence state and lost in the reaction process. Herein, the enlarged quantities of Zn are applied in the bimetallic Pt-Zn catalyst preparation. As confirmed by the increased reduction temperature of oxidized Zn species, it effectively minimizes the influence of the active metal mobility caused by Zn loss. At the same time, the constructed bimetallic structure modulates the surface acidity of Zn species and presents benign propylene desorption ability, thus the formed highly dispersed Pt sites on the surface of Pt1Zn1 alloy are well-matched with its high propylene selectivity (∼98.6%). In addition, the rich-Zn Pt1Zn1 sites are beneficial for enhancing the capability of resisting-coke, thus retarding the deactivation of this catalyst.

Recent Progress on Catalyst Supports for Propane Dehydrogenation

Background: Propane dehydrogenation (PDH) is the most potential propylene production technology, which can make up the large gap in downstream products of propylene. The catalyst supports lay the foundation for the catalytic activity and stability of the prepared catalysts in PDH reactions. Therefore, we focus on the discussion of single oxides, composite oxides, zeolites, and carbon materials as supports to demonstrate the improvement of the catalytic performance of the PDH catalysts. Methods: Recent studies on catalyst supports are reviewed, including the preparation, characterization, and PDH performance. Results: The supports with different morphologies and crystal structures have been reported for PDH. The enhanced strong interaction between the support and metal components is responsible for the superior PDH performance. Conclusions: The PDH catalysts mainly depend on the development of the support with specific physicochemical properties for the corresponding PDH processes. Therefore, it is crucial to develop the optimal supports to improve the PDH performance in the area of nanoscience materials.

Regulation of Active ZnO Species on Si‐based Supports with Diverse Textural Properties for Efficient Propane Dehydrogenation

AbstractPropylene is deemed as a kind of key raw materials with significant value in industrial production. Highly dispersed Zn species are served as active sites in catalyzing propane dehydrogenation reaction (PDH). More importantly, the morphology and textural properties of Si‐based support exert the great influence on the formation of active Zn species. Herein, active Zn species were dispersed on macroporous commercial SiO2, mesoporous siliceous materials (SBA‐15, MCF, DMSN, KIT‐6), and microporous silicalite‐1 (S‐1), respectively. Characterization result indicated that the dispersed active ZnO species were prone to be formed on S‐1, which could be attributed to the confinement effect of micropores in S‐1 and the abundant Si‐OH groups interacted with Zn2+ species. As a result, the optimal ZnOA/S‐1 catalyst exhibited superior catalytic activity (propane conversion of 40.4 %, propylene selectivity of 96.0 %, 550 °C, WHSV=0.47 h−1) during PDH process. Furthermore, the relatively considerable performance of ZnOA/S‐1 catalysts could help to offer a guidance on the design of efficient and low‐cost catalysts for PDH reaction.

Salt-assisted surface charge driven synthesis of large pores alumina as carbon tolerance support for propane dehydrogenation

Porous alumina has been widely used as catalytic support for industrial processes. Under carbon emission constraints, developing a low-carbon porous aluminum oxide synthesis method is a long-standing challenge for low-carbon technology. Herein, we report a method involving the only use of elements of the aluminum-containing reactants (e.g. sodium aluminate and aluminum chloride), sodium chloride was introduced as the coagulation electrolyte to adjust the precipitation process. Noticeably, the adjustment of the dosages of NaCl would allow us to tailor the textural properties and surface acidity with a volcanic-type change of the assembled alumina coiled plates. As a result, porous alumina with a specific surface area of 412 m2/g, large pore volume of 1.96 cm3/g, and concentrated pore size distribution at 30 nm was obtained. The function of salt on boehmite colloidal nanoparticles was proven by colloid model calculation, dynamic light scattering, and scanning/transmission electron microscopy. Afterward, the synthesized alumina was loaded with PtSn to prepare catalysts for the propane dehydrogenation reaction. The obtained catalysts were active but showed different deactivation behavior that was related to the coke resistance capability of the support. We figure out the correlation between pore structure and the activity of the PtSn catalysts associated with the maximum conversion of 53 % and minimum deactivation constant occurring at the pore diameter around 30 nm of the porous alumina. This work offers new insight into the synthesis of porous alumina.

Effect of non-boron element with the different electronegativity of binary boride on oxidative dehydrogenation of propane

Boron-based catalysts are active and selective in the oxidative dehydrogenation reaction of propane (ODHP) to propylene. Herein, the binary boron-based compounds (boron nitride, boron phosphide, boron carbide, and silicon boride) composed of boron elements and one type of other non-boron elements, and the elemental boron were systematically compared to elucidate how the non-boron elements of binary borides influence their catalytic activity in ODHP. By combined experimental and computational studies, we demonstrated that the non-boron elements can modulate the performance of catalysts by altering the ability of the B-OH site to activate dioxygen and the subsequent activation of propane. In particular, the turnover frequency (TOF) of the catalyst exhibited a high negative linear correlation with the electronegativity of the non-boron element, except for the boron phosphide. This study highlights the importance of the chemical environment around the active boron sites and provides insight into the design of efficient ODHP catalysts.

Properties of CrOx/MCM-41 and Its Catalytic Activity in the Reaction of Propane Dehydrogenation in the Presence of CO2

Propylene is an important raw material for the production of many valuable compounds, especially polypropylene, the consumption of which continues to grow every year. The reaction of oxidative dehydrogenation of propane, where carbon dioxide is used as a mild oxidant, is a promising method for producing propylene. At the same time, the problem of utilization of greenhouse gas CO2 is partially solved. The synthesis and analysis of the physicochemical properties of mesoporous silicate MCM-41 and supported catalysts CrOx/MCM-41 prepared on its basis were carried out. These catalysts were prepared using incipient wetness impregnation. The support and catalysts were characterized by the methods of low-temperature nitrogen adsorption, TG-DTA, XRD, SEM, TPR-H2, UV/Vis diffuse reflectance spectroscopy, and small-angle X-ray scattering. It is shown that chromium is present in the samples simultaneously in the form of Cr3+ and Cr6+. The catalytic tests were performed in the range of 550–700 °C. The highest selectivity for propylene was observed for the 5%Cr/MCM-41 catalyst and was 76% at a temperature of 650 °C with a propane conversion of 20%. The deposited catalysts Cr/MCM-41 and Cr/SiO2 (Acros) were compared. The propylene selectivity for the MCM-41-supported catalyst was ~1.5 times higher than that for the SiO2-supported catalyst.

Size-Dependent Structures and Catalytic Properties of Supported Bimetallic PtSn Catalysts for Propane Dehydrogenation Reaction

Heterogeneous bimetallic catalysts are widely used in industrial processes, and the structural features of the bimetallic catalysts have profound impacts on their properties in numerous catalytic processes. Bimetallic nanoclusters with particle sizes ≤1 nm have shown better performances in various catalytic reactions in comparison to conventional bimetallic nanoparticles with sizes above 1 nm. Despite the progress made in recent years in the synthesis and catalytic studies of bimetallic nanoclusters, achieving a fundamental understanding of the structure–reactivity relationships at the molecular and atomic levels remains challenging because of the complexity of the bimetallic catalysts with particle sizes ≤1 nm. In this work, we have studied the structural features of supported bimetallic PtSn species with different sizes (∼0.6 to ∼1.6 nm), which is shown to be associated with the size-dependent formation process of bimetallic PtSn species according to theoretical modeling and experimental studies. Furthermore, the catalytic consequences of their size-dependent structural features are reflected in the dehydrogenation of propane to propylene, in which the subnanometer PtSn clusters are more active than the PtSn alloy nanoparticles.

Sn1Pt single-atom alloy evolved stable PtSn/nano-Al2O3 catalyst for propane dehydrogenation

The PtSn/Al2O3 is a prototypical industrial catalyst for propane dehydrogenation (PDH). However, the local structures of the active sites are still inconclusive under the operation conditions. Herein, the evolutions of the Pt-Sn active centers supported on nano-Al2O3 are definitely discerned at the atomic level during PDH reaction. By combining complementary in situ characterizations and theoretical calculations, we demonstrate that a highly productive Sn1Pt single-atom alloy (47.6 molC3H6 gPt–1 h–1) forms after the reduction, and thereby self-assembles to the Pt3Sn intermetallic compound during the reaction, which exhibits a rather stable performance (kd-10~40h: 0.0026 h–1). Intriguingly, the results of in situ diffuse reflectance infrared Fourier-transform spectroscopy further corroborate that the adjacent Pt atoms with terrace sites aggravating the coke deposition can be circumvented through this single-atom alloy mediated reconstruction. Our findings depict an unprecedented evolution process of the active sites of the PtSn/Al2O3, and afford an effectual nanostructure engineering pathway for stable PDH catalysts.

CFD-DEM analysis of the influence of heat storage materials on propane dehydrogenation process

The heat transfer process can significantly affect the propane dehydrogenation (PDH) reaction due to its strongly endothermic nature. This paper describes the influence of heat storage materials (HSM) on the heat transfer and reaction process of PDH, using computational fluid dynamics coupled with discrete element method in combination with reaction kinetics and heat transfer models at the particle scale. During the dehydrogenation, the particle temperature and propane conversion gradually decrease due to the endothermic nature until they become relatively stable. It is found that, initially, HSM particles can provide heat to the reaction through particle–fluid–particle conduction and maintain higher temperature and propane conversion. Gradually, HSM particles can take part in the gas–solid convection and then transfer the heat to the catalyst particles by particle–fluid–particle conduction for the endothermic reaction. Eventually, the heat of reaction and the heat from the hot feed by convection and radiation reach a balance. Furthermore, HSM particles with higher specific heat capacity can provide more heat to the reaction, while the thermal conductivity of HSM particles has insignificant effect on the heat transfer process, since the particle–fluid–particle conduction plays a major role in the heat transfer between particles. This study presents comprehensive understandings of the heat transfer process and the function of HSM particles for endothermic reaction.

Al2O3 Nanorod with Rich Pentacoordinate Al3+ Sites Stabilizing Co2+ for Propane Dehydrogenation

The search for inexpensive, environmentally friendly, and highly effective catalysts to activate C-H bonds in propane dehydrogenation (PDH) reactions is still a major challenge. Co-based catalysts have gained significant attention in recent years due to their excellent ability to activate C-H bonds and their high selectivity towards olefins, despite being a non-noble and environmentally unfriendly metal. However, further improvements are necessary for practical utilization, particularly in terms of activity and anti-carbon deposition capacity. In this study, we synthesized Al2O3 nanorods with abundant pentacoordinated Al3+ (Al3+penta) sites. The supported Co on the Al2O3 nanorod (Co/Al2O3-NR) exhibited higher selectivity (>96% propylene selectivity) and stability (deactivation rate 0.15 h−1) compared to Co supported on an Al2O3 nanosheet with fewer pentacoordinated Al3+ sites. Various characterizations confirmed that Co(II) mainly exists as CoAl2O4 rather than Co3O4 in the form of Co/Al2O3-NR, which inhibits the reduction of Co(II) to Co0 and accordingly improves catalyst stability.

Amorphous silica-alumina as robust support for catalytic dehydrogenation of propane: Effect of Si/Al ratio on nature and dispersion of Cr active sites

The effect of amorphous silica-alumina (ASA) with Si/Al ratios of 0.01, 0.1, 1, and 3 on the catalytic performance of chromium catalysis in the propane dehydrogenation reaction were studied. The characterization results reveal that the Si/Al ratio significantly affects the nature and dispersion of chromium species, reducibility, the surface concentration of Cr3+, and acidity. ASA catalysis with Si/Al ratios of 0.1 and 0.01 showed a remarkable increase in Cr6+ species and the lowest α-Cr2O3, which have the highest propane conversion (with initial propylene yield of 60 and 57, respectively) due to the reduction of surface monochromate Cr6+ species, which are the precursor of coordinatively unsaturated active sites (c.u.s.) to active Cr3+ species. Si/Al increase to the values of 1 and 3 can restrict the access of reactants to active Cr species due to the decrease in chromium reduction and increase in α-Cr2O3.

Strategies for regeneration of Pt-alloy catalysts supported on silica for propane dehydrogenation

Catalyst stability, resistance to deactivation, and regeneration remain a challenge for high temperature reaction processes. For Pt alloys used in propane dehydrogenation (PDH), the primary pathways of catalyst deactivation include coke formation and metal nanoparticle sintering over time. Recent work shows that silica-supported catalysts provide excellent selectivity for this reaction, but the regenerability of silica-supported catalysts has not been established. In this work, we study a series of Pt alloys, including PtMn, PtZn, and PtSn, for the PDH reaction at 550 °C and 600 °C, and we subject the catalysts to regeneration over multiple cycles. While oxidation in air restores the reactivity completely with minimal catalyst sintering, it is surprising to find that these catalysts can also be regenerated in pure hydrogen. Here we explore the types of coke formed on these catalysts using in situ temperature programmed oxidation (TPO). Two types of coke are found: one on the metallic NP surface, and a second on the silica support. Our work shows that treatment in hydrogen causes redistribution of the coke between the metal and support, which can restore most catalytic activity lost during a reaction run. Periodic introduction of H2 during a reaction cycle may constitute an unexplored strategy for extending the lifetime of PDH catalysts.

Small-Molecule Modification Provides Pt Nucleation Sites for Enhanced Propane Dehydrogenation Performance

The rational synthesis of catalysts with controllable structures and the study of their structure–activity relationships to break the limitations of traditional catalysts remain challenging. Herein, tetrakis(dimethylamido)tin (TDMASn) exposures were used to modify silicalite-1 (S-1) lacking suitable chemisorption sites on their surfaces to provide Pt nucleation sites, obtaining a Pt/20TDMASn/S-1 sample. For comparison, Pt species supported on bare S-1 (Pt/S-1) and Pt species supported on the S-1 of pre-deposited SnO2 (Pt/20SnO2/S-1) were also prepared. Catalysts were characterized extensively by X-ray diffraction, temperature-programmed reduction, transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse-reflectance infrared Fourier transform spectroscopy of adsorbed CO. The results showed that this surface modification (TDMASn or SnO2) yielded up to about a 40-times increase in Pt content after 20 cycles of Pt atomic layer deposition (ALD). Compared with Pt/20SnO2/S-1, Pt/20TDMASn/S-1 had a smaller particle size, stronger interactions between the metal species and the support, and a lower Sn0 content, thus resulting in a remarkably higher initial propane conversion in the propane dehydrogenation (PDH) reaction. The catalytic activity could also be optimized based on the number of ALD-TDMASn exposures. As a consequence, Sn not only provided nucleation sites for Pt but also acted as a promoter to enhance the catalyst performance. This fundamental understanding will help researchers obtain suitable catalysts for PDH processes.

Effect of yttrium on catalytic performance of Y-doped TiO2 catalysts for propane dehydrogenation

Defective bulk catalysts based on TiO2 have superior catalytic performance for propane dehydrogenation (PDH). The oxygen vacancy concentration and the number of active sites on the catalyst surface can be effectively tuned by doping metal in TiO2. Herein, yttrium (Y)-doped titanium dioxide (nY/TiOx) catalysts were in-situ synthesized via the coprecipitation method to study the effect of rare earth metal Y doping on the structure of TiO2 and the catalytic performance for PDH. Experimental results demonstrate that Y-doped TiO2 exhibits higher catalytic activity, propylene selectivity and stability than bare TiO2. Full characterizations with X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy of pyridine adsorption (Py-IR), temperature-programmed desorption of ammonia (NH3-TPD), H2 temperature-programmed reduction (H2-TPR), and Raman techniques on these catalysts reveal that Y3+ can enter TiO2 lattice, and the lattice stability of the catalyst can be enhanced by replacing Ti4+ to form Y–O–Ti structure. Meanwhile, the introduction of an appropriate amount of Y can obviously promote the PDH reaction by adjusting the acidity of the catalyst, improving the release capacity of TiO2 lattice oxygen and increasing the formation of active centers. Nevertheless, excessive Y doping will lead to pore clogging, and the exposure of active sites will be reduced, resulting in the degradation of catalytic performance.

Uniformly stable hydroxylated cobalt(II) silicate species embedded within silicalite-1 zeolite for boosting propane dehydrogenation

Co-based catalysts are promising alternatives to replace expensive Pt- and toxic Cr-based catalysts for propane dehydrogenation (PDH), while the catalytic stability and propylene selectivity have been subjected to the diversity of Co speciations. Given the situation, uniformly stable hydroxylated Co2+ silicate sites (depicted as {OH–Si–(OH)–Co–O–Si-(OH)3}) are successfully embedded into the silicalite-1 zeolite framework located in the straight and intersection channels (Co@S-1) with the assistance of Co precursors and geminal silanols via a facile hydrothermal synthesis, as revealed by detail characterizations. Under comparable conditions, a superior catalytic PDH performance with attractive propylene formation rate of 14.6 mmol·gcat−1·h−1, propylene selectivity higher than 93% and very low deactivation rate of 0.0206 h−1 after 7 h is achieved over the Co@S-1(EDA) catalyst. Furthermore, the catalytic performance can be restored to the same as that of the fresh catalyst after 3 successive regenerations. In situ FTIR spectra analysis further reveals the dynamic changes in the characteristic absorption bands associated with the hydroxylated Co2+ silicate sites and the intermediate product (2-propyl) during the PDH reaction and a reaction mechanism is proposed accordingly. This work provides a new insight for designing high-efficiency nonprecious metal PDH catalysts.

Restructured zeolites anchoring singly dispersed bimetallic platinum and zinc catalysts for propane dehydrogenation

Restructuring of a heterogeneous catalyst under reaction conditions is a common phenomenon. Severe restructuring of a catalyst can result in deactivation in many catalytic systems—for example, the catalytic dehydrogenation of propane to propylene. Herein, we report the utilization of catalyst restructuring to improve activity and stability for the propane dehydrogenation reaction. A bimetallic platinum and zinc (Pt1Znm) catalyst protected by an in situ restructured silicalite-1 zeolite is prepared. The catalyst yields outstanding activity (initial conversion of ∼69.2%, initial selectivity of ∼91.1%) with high stability at 580°C, which is better than several commercial catalysts. Characterization shows the singly dispersed bimetallic sites of Pt1Znm serve as the catalytic sites during the reaction. Moreover, the less-stable silicalite-1 zeolite undergoes restructuring during the dehydrogenation reaction, forming a crucial protective layer on the Pt1Znm bimetallic nanocatalysts.

Synthesis of CexZr1‐xO2/SiO2 supports for chromium oxide catalysts of oxidative dehydrogenation of propane with carbon dioxide

AbstractBACKGROUNDPropane dehydrogenation is an alternative way both to produce propylene and to utilize CO2. Because of the high oxygen mobility in cerium‐zirconium oxide (CexZr1‐xO2), it looks promising as a support for the chromium oxide catalysts of propane dehydrogenation with CO2. Supports of CexZr1‐xO2 on mesoporous silica were synthesized in this work to combine the high oxygen mobility of the former and the pore structure of the latter.RESULTSTwo applied synthetic approaches resulted in materials with different structure and properties. The wet impregnated catalysts demonstrated a higher activity and selectivity to propylene. At the same time, they had larger pore size distribution maxima (~9 nm) than the samples prepared by the introduction of metals simultaneously with Si‐precursor hydrolysis (~2 nm). For the chromium catalysts with the same support, the catalytic activity decreased with varying chromium loading as follows: 5% Cr > 3% Cr ≈ 7% Cr. For the catalysts with different CexZr1‐xO2 supports and equal chromium loading, the activity decreased with x changing as follows: 0.5 > 0.6 > 0.8 for the samples prepared by wet impregnation, and 0.8 ≈ 0.6 > 0.5 for the other synthetic path.CONCLUSIONSCatalysts were tested in oxidative dehydrogenation of propane with CO2. The wet impregnation approach turned out to be much more promising in terms of catalytic activity and selectivity to propylene in the reaction of propane dehydrogenation with CO2. The selectivity achieved was ≤80% at a 40% conversion. © 2023 Society of Chemical Industry (SCI).