Partial Oxidation Of Propane Research Articles

Techno-economic analysis of bromine mediated propane oxidative dehydrogenation to produce propylene

The production of propylene from propane is becoming increasingly important. Catalytic propane dehydrogenation (PDH) is the major on-purpose propylene production process today. The conventional PDH process has a relatively high energy consumption (6.1–9.4 kWh/kg C3H6) which results in high direct CO2 emissions and modest propylene yield (0.8–0.9 kg C3H6/kg C3H8). A bromine-mediated propane oxidative dehydrogenation process (Br-ODH) is evaluated in this techno-economic study which can potentially improve both the process energy efficiency and product yield. To investigate the Br-ODH process feasibility, a heat integrated process model was designed using Aspen Plus® V12 for a 450 kta propylene facility using reaction data from the literature. The partial oxidation of propane under bromine limited conditions selectively produces a propylbromide intermediate which can be readily separated from propane. Propylbromide undergoes dehydrobromination under relatively mild conditions to produce the propylene product in a second step. Bromine is regenerated by conversion of the hydrogen bromide byproduct either thermochemically or electrochemically. Due to the current interest in use of renewable electricity in chemical processes, the electrochemical regeneration process was evaluated in this study. Based on the model, the Br-ODH process can achieve approximately 10% higher propylene yield with 37% lower utilities than conventional PDH. However, the use of high-cost electrolyzers resulted in the capital investment increasing by approximately 11%. Capital cost was also increased due to the requirements of high alloy materials of construction for the potentially corrosive halogen containing equipment. The sensitivity analysis showed that the production cost was most sensitive to the propane price. For the electrolyzer-based regeneration process the capital cost was found to be key parameter that might limit competition with conventional PDH; however, the development of a commercial thermochemical HBr oxidation process analogous to the Deacon process for chlorine would likely bring significant cost savings.

Reaction-Driven Formation of Ag-Cu Alloy Nanostructures from Cu@Ag Core-Shell Nanoparticles Analyzed by Moirè Patterns Using Environmental TEM Images

Well defined Cu@Ag core@shell (or core-shell) nanoparticles have been synthesized through a carbon monoxide (CO)-assisted solution phase method. These Cu@Ag nanoparticles transformed into Ag-Cu alloy nanostructures under propylene epoxidation conditions. Environmental transmission electron microscopy (ETEM) revealed the structural evolution of Cu@Ag nanoparticle under different propylene-to-oxygen (PP/O2) ratios based on the Moirè pattern analysis of the micrographs obtained in situ. The counter diffusion of Ag and Cu atoms, from the shell and core respectively, was observed at the PP/O2 ratio of 2:1. When the PP/O2 ratio was 1:1, Cu@Ag core-shell nanoparticles turned into alloy nanostructures. The transformation from Cu@Ag to Ag-Cu alloy nanoparticles changed the catalytic performance in the production of propylene oxide from partial oxidation of propylene, resulting in a yield of 1.14 min−1 and selectivity of 79% when the PP/O2 ratio was 2:1. This study shows besides temperature and pressure, other less-studied factors of reaction conditions such as composition of reactants may play critical roles in the dynamics of bimetallic nanostructures, thus their corresponding catalytic performances. This study develops the techniques on the applications of Moirè patterns for analyzing the dynamics of bimetallic core-shell nanostructures at atomic scale using (S)TEM micrographs.

Partial Oxidation of Propane: Single-Site Pd/γ-Al2O3 Catalysts

The paper proposes a method for synthesizing a heterogeneous catalyst that contains single Pd sites on γ-Al2O3 surface. This method involves preliminary heterogenization of a Pd complex with a hydroxyquinone (e.g., alizarin) on the γ-Al2O3 surface, followed by hydrogenolysis of the Pd–alizarin bond, reduction of Pd(II) into Pd(0), and removal of alizarin. The catalyst was examined by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and tested in propane oxidation into key petrochemicals. During the test, the catalyst exhibited high activity (242 mol of the product per g-at Pd per hour).

Partial Oxidation of Propane: Single-Site Pd/γ-Al2O3 Catalysts

Partial Oxidation of Propane: Single-Site Pd/γ-Al2O3 Catalysts

Structure sensitivity of propane partial oxidation over chromium-manganese binary oxides

Catalytically active chromium-manganese oxides (CMO) were synthesized by the sol-gel route for the partial oxidation of propane to propene. The effects of calcination temperature and time on the catalytic performance of the CMO were examined in a fixed bed reactor within 300–600 °C at a gas hourly space velocity (GHSV) of 6,000 mL·g−1cat·h−1. Structural and morphological analysis disclosed nano-crystallite sizes and spherical shapes with smooth and tiny particles. The introduction of Cr tends to increase the specific surface area, decrease the pore diameter and crystallite size, as well as the bandgap energy of the obtained samples, which promoted the movement of abundant lattice oxygen. Based on the light-off curves, the catalyst CM32 (CMO calcined at 300 °C@2 h), with low calcination temperature and long calcination time, achieved the best performance and stability. CM32 exhibited the highest selectivity and yield, 79.35% and 29.80%, respectively. CM32 owned a reaction rate of 2.93 mol·g−1cat·s-1 and apparent activation energy of 49.52 kJ mol-1, which could be related to not only its higher quantity of lattice oxygen (O2−) and Cr6+/Cr3+ ratio, but also to the decrement in pore diameter size and bandgap energy. The reaction pathway was proposed based on the MvK mechanism for the propane partial oxidation. Moreover, CM32 maintained its catalytic performance after a stability test of 100 h’ time-on-stream. The highly stable and active CM32 catalyst obtained shows good potential for partial oxidation of propane to propene.

Sorption-enhanced propane partial oxidation hydrogen production for solid oxide fuel cell (SOFC) applications

Solid oxide fuel cells (SOFC), as high-temperature fuel supply systems, are regarded as one of the most adaptable technologies in terms of efficiency, flexibility, and environmental friendliness. Catalytic propane partial oxidation is recognized as an efficient gas supply method for SOFC applications. However, incombustible by-product CO2 would decrease the purity of hydrogen, thereby reducing the power of fuel cells. Sorption-enhanced propane partial oxidation is an efficient way to adapt to SOFC operating conditions while improving hydrogen production and reducing carbon dioxide emissions. This paper introduces a cage-like porous Ce1-xCaxMO3-λ (M = Co, Fe and Cu) sorbent for providing high carbon dioxide sorption capacity and improving hydrogen purity over the Ni/Al2O3 catalyst. As obtained, Ce1-xCaxFeO3-λ and Ni/Al2O3 sorbent-catalyst performed the best, with the highest hydrogen yield up to 1654 μmol/gcat·s which was 1055 μmol/gcat·s higher than that of pure Ni/Al2O3. The produced reforming gas is served as a fuel in the proposed SOFC system. A maximum output power density of 581 mW/cm2 was reached. This work offered a simple and viable way of combining inexpensive and robust catalyst-sorbent for sorption-enhanced propane partial oxidation in terms of efficient indirect hydrogen supply toward SOFC power generation.

Fine cubic Cu2O nanocrystals as highly selective catalyst for propylene epoxidation with molecular oxygen

Propylene epoxidation with O2 to propylene oxide is a very valuable reaction but remains as a long-standing challenge due to unavailable efficient catalysts with high selectivity. Herein, we successfully explore 27 nm-sized cubic Cu2O nanocrystals enclosed with {100} faces and {110} edges as a highly selective catalyst for propylene epoxidation with O2, which acquires propylene oxide selectivity of more than 80% at 90–110 °C. Propylene epoxidation with weakly-adsorbed O2 species at the {110} edge sites exhibits a low barrier and is the dominant reaction occurring at low reaction temperatures, leading to the high propylene oxide selectivity. Such a weakly-adsorbed O2 species is not stable at high reaction temperatures, and the surface lattice oxygen species becomes the active oxygen species to participate in propylene epoxidation to propylene oxide and propylene partial oxidation to acrolein at the {110} edge sites and propylene combustion to CO2 at the {100} face sites, which all exhibit high barriers and result in decreased propylene oxide selectivity.

Partial oxidation of propylene with H2 and O2 over Au supported on ZrO2 with different structural and surface properties

Various ZrO2 with pure tetragonal, monoclinic, and mixed phases were used as carriers of gold nanoparticles for an exploration to production of propylene oxide (PO) in co-presence of propylene with H2 and O2. Catalysts with similar gold dispersion (2–5 nm gold particles) were prepared by a deposition–precipitation method. 100% selectivity to PO was obtained for the first time over non-titanium-supported Au catalysts on both tetragonal and monoclinic ZrO2 supports, which needs a good match of nanogold and active sites (quite possible hydroxyls connected with Zr4+). However, Au/tetragonal ZrO2 benefits PO formation that could be accelerated by hydroxyl groups while Au/monoclinic ZrO2 generates more acrolein and suppresses CO2 formation. The active sites for the production of PO are speculated to be Au and Zr-O rectangular pyramids in ZrO2, similar to that on TiO2 and acrolein appears on the Au near oxygen vacancies.

Plasmonic nanoreactors regulating selective oxidation by energetic electrons and nanoconfined thermal fields

Optimizing product selectivity and conversion efficiency are primary goals in catalysis. However, efficiency and selectivity are often mutually antagonistic, so that high selectivity is accompanied by low efficiency and vice versa. Also, just increasing the temperature is very unlikely to change the reaction pathway. Here, by constructing hierarchical plasmonic nanoreactors, we show that nanoconfined thermal fields and energetic electrons, a combination of attributes that coexist almost uniquely in plasmonic nanostructures, can overcome the antagonism by regulating selectivity and promoting conversion rate concurrently. For propylene partial oxidation, they drive chemical reactions by not only regulating parallel reaction pathways to selectively produce acrolein but also reducing consecutive process to inhibit the overoxidation to CO2, resulting in valuable products different from thermal catalysis. This suggests a strategy to rationally use plasmonic nanostructures to optimize chemical processes, thereby achieving high yield with high selectivity at lower temperature under visible light illumination.

Enhancement effect of catalyst support on indirect hydrogen production from propane partial oxidation towards commercial solid oxide fuel cell (SOFC) applications

Utilization of propane in solid oxide fuel cells (SOFCs) is desired for commercial applications. However, the susceptibility of conventional Ni-based anode to coking is still a technical challenge. Developing an efficient catalyst for hydrogen production through partial oxidation of propane is a feasible approach to address this issue. In fact, hydrogen production from propane partial oxidation is profoundly determined by catalyst performance, which further affects the fuel cell efficiency. In this study, a robust and efficient catalyst is developed by incorporating inexpensive TiO2 into Ni-Co/Al2O3 catalyst. The results suggested that an appropriate amount of TiO2 in catalyst support could regulate the interaction between active metal and Al2O3 support therefore inhibiting catalyst carbon deposition and sintering. Also, TiO2 addition is conducive to the catalyst regeneration process by reducing the activation energy of oxidative decarburization. Hydrogen yield was efficiently promoted by the synthesized catalyst. Consequently, under the equivalent hydrogen (160 ml/min) produced over the catalyst, the SOFCs, with a cathode area of 15 cm2, display impressive performance (maximum power density, 404 mW/cm2) and excellent stability. Through cost-benefit analysis, the application of the synthesized catalyst is considered for great advantages in capital and energy saving. Ultimately, this work might offer a novel point of view for developing a low-cost, robust and efficient catalyst towards indirect hydrogen production for SOFCs.

CO as a Probe Molecule to Study Surface Adsorbates during Electrochemical Oxidation of Propene

AbstractA major challenge in the electrochemical oxidation of hydrocarbons is understanding the formation of intermediate species, some of which continue to react, while others are non‐reactive or poisonous species that block adsorption of further reactants. Herein we investigate the identity and behavior of adsorbates formed during partial oxidation of propene. We employ two techniques: Electrochemistry‐Mass Spectrometry (EC‐MS) and Attenuated Total Reflection Infrared Spectroscopy (ATR‐FTIR). In both cases, we use CO as a probe molecule, to perturb the ad‐layer of propene intermediates. In the EC‐MS experiments, propene and its intermediates were quantified by triggering their desorption via displacement with CO. We show evidence for at least two distinct classes of propene adsorbates, via CO displacement and electrochemical stripping. A redshift in the ν(C−O) mode was observed, during IR spectroscopy, reflecting the chemical environment arising from strongly bound propene intermediates.

Homogeneous Metal-Complex Catalyst Systems in the Partial Oxidation of Propane with Oxygen

Homogeneous Metal-Complex Catalyst Systems in the Partial Oxidation of Propane with Oxygen

Theoretical study of propylene epoxidation heterogeneous‐homogeneous mechanism over MoOx/SiO2 catalyst

AbstractThe green direct propylene (C3H6) epoxidation on MoOx is well studied by experimental methods, but detailed molecular reaction mechanism studies using in‐silico experiments method are few. Here, the different oxidation heterogeneous‐homogeneous pathways for MoOx/SiO2 catalyst are calculated, mainly involving Mo=O on di‐oxo tetracoordinate MoOx, allyl peroxy (C3H5OO•), and allyloxy (C3H5O•) radicals. The results show that, for surface reaction mechanism with Mo=O, the barriers of propylene oxide (PO) and acetone generation are too high; in comparison, the byproduct acrolein is more beneficial product with a lower barrier. In heterogeneous‐homogeneous pathways, the desorbed allyl (C3H5•) from the surface can easily combine with O2 to synthesize C3H5OO• radical, and in the partial oxidation of propylene with C3H5OO• as an oxidant, PO is more beneficial with a low barrier compared to byproducts such as propanal, acetone, acetaldehyde, etc. These indicate that (a) gas‐phase free radical reactions have important effects on PO generation, in which C3H5OO• is the main active species; (b) on MoOx surface, Mo=O is difficult to be used as the active O species for PO production. Further research is needed on other active sites such as Mo‐O‐Mo or defective sites.

Atmospheric-pressure growth of multi-walled carbon nanotubes over Ni–Fe nanosheets supported on α-Al2O3 foam

A novel Ni–Fe nanosheets catalyst supported on α-Al2O3 foam ceramic was synthesized by a hydrothermal method and used to obtain multi-walled carbon nanotubes (MWNTs) via the propane partial oxidation. Catalytic performance tests were carried out at 600 °C and atmospheric pressure using a fixed-bed reactor. The synthesized catalysts and carbon materials were analyzed using various characterization methods. According to the field emission scanning electron microscope (FESEM) results, the catalyst morphology was a 3D grid structure consisting of nanosheets 800 nm length and 80 nm width. Additionally, the quantity and quality of the carbon nanotubes were greatly influenced by different oxygen-to-propane molar ratios, defined as the equivalence ratio ϕ (ϕ = 1.5, 1.78, 2). Transmission electron microscope (TEM) images showed that carbon nanotubes over all catalysts were MWNTs. In addition, the thermogravimetric analysis and Raman data showed that a high yield of MWNTs was obtained at ϕ = 1.78, but the accumulated MWNTs at ϕ = 1.5 exhibited a higher degree of graphitization (ID/IG = 0.89) compared with the other two equivalence ratios.

Exploring the possibilities of carbon materials as catalytic supports for partial oxidation reactions

The present study evaluates the possibilities as catalytic supports for partial oxidation reactions of two activated carbons obtained from biomass waste by partial gasification with CO2 and chemical activation with H3PO4 (AC and ACP, respectively), and of one mesostructured carbon material (PMC). For comparative purposes, the results are compared with those obtained with conventional mesoporous silica material SBA-15. The porous structure and chemical composition have been evaluated by N2 and CO2 adsorption at -196 and 0 °C respectively, SEM, TEM, ICP, XRD and TPR, whereas the support properties have been evaluated as support for Cu active phases during propylene partial oxidation reaction. The results have shown that ACP is a very useful catalytic support that presents many advantages, due to its low cost and simple synthesis, that allow preparing activated carbons with high mesoporosity, favoring the distribution of Cu species, with high stability against gasification at relatively high temperatures and good catalytic activity and selectivity in acrolein production.

Enhancing hydrogen production from propane partial oxidation via CO preferential oxidation and CO2 sorption towards solid oxide fuel cell (SOFC) applications

Under the demand of distributed power sources, solid oxide fuel cell (SOFC) has attracted considerable interest for its high efficiency. However, non-carbon neutral and CO poisoning limit the applications of SOFC when converting hydrocarbons to hydrogen-rich gas by thermally incorporating an external/internal processor. In this work, an external reformer and SOFC system is established to improve hydrogen production therefore enhancing power density by CO preferential oxidation and CO2 sorption-enhanced methods. The prepared CoxMgyCa(1-x-y)Oz sorbents are observed to provide porous structures, and Co0.110Mg0.204Ca0.686Oz presents the most uniform pore size distribution and the highest CO2 sorption capacity by lowering the CO2 sorption activation energy via kinetic analysis. By using the mixture of Ni/Al2O3–SiC catalyst and the synthesized CoxMgyCa(1-x-y)Oz sorbents, sorption-enhanced hydrogen production from propane partial oxidation is achieved for a higher hydrogen production and lower CO, CO2 productions. The produced hydrogen is served as a fuel of the proposed SOFC system, and a maximum output power density of 513 mW/cm2 at 1.2 A/cm2 is reached, which is equivalent to 160 mL/min of pure H2. This work might offer a novel insight for developing low-cost processes towards indirect hydrogen production for fuel cells.

Hydrogen production via catalytic propane partial oxidation over Ce1-xMxNiO3-λ (M=Al, Ti and Ca) towards solid oxide fuel cell (SOFC) applications

Indirect hydrogen production routes presented extensive compatibilities for distributed solid oxide fuel cell systems. Catalyst activity directly determines hydrogen production and profoundly affects the power generation. In this work, Ce1-xMxNiO3-λ (M = Al, Ti and Ca) were synthesized for hydrogen production from propane partial oxidation (POx). From the results, it indicated that the choice of catalyst compositions could directly affect the microstructure during the preparation process. Also, different Ce1-xMxNiO3-λ catalysts displayed distinctive carbon tolerance performances due to the different active particle sizes and surface properties of the catalysts. In general, the synthesized Ce1-xMxNiO3-λ catalysts showed higher hydrogen production than a commercial nickel cerium catalyst. From the observation of a SOFC test system powered by injecting the generated H2 from catalytic propane POx reaction, the obtained power density of CNO–Al displayed an increase of 22.6% compared to the commercial nickel cerium catalyst. It was quite impressive that the equivalent hydrogen (160 ml/min) produced over CNO–Al and the obtained power density (482.6 mW/cm2) of SOFCs were competitive while CNO–Ca presented an excellent stability with a better carbon tolerance performance for the long-term tests. The achievements of this work might offer a novel point of view for developing low-cost catalyst towards indirect hydrogen production for SOFC.

Promoter Effects on Catalyst Selectivity and Stability for Propylene Partial Oxidation to Acrolein

Highly dispersed silica-supported CuOx/SiO2 catalysts were synthesized via solution-phase deposition and studied for their activity, selectivity, and stability in catalyzing the selective oxidation of propylene to acrolein. Strategies for ensuring high metal dispersion included controlling the surface density of silanols (via covalent silanol-capping) or by pre-installing different “promoter” transition metals at submonolayer coverages. A comparison of the effect of first row transition metal promoters showed that V and Cr significantly boost catalyst performance and stabilize CuOx sites against aggregation.

Hydrogen production from partial oxidation of propane: Effect of SiC addition on Ni/Al2O3 catalyst

One of the most attractive routes for hydrogen production for fuel cell applications is partial oxidation of hydrocarbons. However, exothermic partial oxidation reaction tends to cause local overheating of the reaction bed therefore reducing catalytic activity. In this study, hydrogen production by partial oxidationofpropane over Ni/Al2O3 based catalyst with the addition of SiC was experimentally investigated. Both packed bed mixing and bulk doping methods were introduced to study the effect of SiC for its high thermal conductivity and high temperature stability. The as-prepared samples were characterized by a variety of measurements. Due to the high temperature stability of SiC particles in the bulk regions, stacking dual porous-like structures were formed after calcination by doping SiC into Ni/Al2O3 with certain ratios. From the results, local overheating of the catalyst bed generated by the exothermic reactions was relieved by SiC addition for both cases. Ni/Al2O3-SiC (30 wt% SiC) catalyst performed a higher hydrogen production of 236 μmol/gcat.s and kept stable for 20 h at 600 °C compared to mechanical mixing method. Aggregation of Ni content and carbon deposition of the spent catalyst of SiC-containing catalysts were reduced compared to Ni/Al2O3. As can be seen from the morphological and non-isothermal kinetics, the carbon deposited on Ni/Al2O3-SiC catalyst that caused catalyst deactivation was more easily activated for removal due to SiC content with high thermal conductivity.

Efficient hydrogen production from partial oxidation of propane over SiC doped Ni/Al2O3 catalyst

The composite Ni/Al2O3-SiC catalyst was designed and synthesized for hydrogen production from propane partial oxidation. Through the composite of high thermal conductivity SiC and porous solid acid Al2O3, it improved the shortcoming of sintering and inactivation of high-temperature reaction for Ni-based catalysts. The samples were characterized by X-ray diffraction, N2 physical adsorption, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis etc. From the results, the SiC doped catalyst exhibited superior catalytic properties for hydrogen production by propane partial oxidation. By doping SiC with high thermal conductivity to Al2O3 support, the catalyst was improved for sintering and carbon deposition resistance and reducing the aggregation of Ni active sites reflected by improving the stability of hydrogen production.