Propane Conversion Rate Research Articles

Efficient propane dehydrogenation catalyzed by Ru nanoparticles anchored on a porous nitrogen-doped carbon matrix

Propane dehydrogenation (PDH) is a vital industrial process for producing propene, utilizing primarily Cr-based or Pt-based catalysts. These catalysts often suffer from challenges such as the toxicity of Cr, the high costs of noble metals like Pt, and deactivation issues due to sintering or coke formation at elevated temperatures. We introduce an exceptional Ru-based catalyst, Ru nanoparticles anchored on a nitrogen-doped carbon matrix (Ru@NC), which achieves a propane conversion rate of 32.2% and a propene selectivity of 93.1% at 550 °C, with minimal coke deposition and a low deactivation rate of 0.0065 h−1. Characterizations using techniques like TEM and XPS, along with carefully-designed controlled experiments, reveal that the notable performance of Ru@NC stems from the modified electronic state of Ru by nitrogen dopant and the microporous nature of the matrix, positioning it as a top contender among state-of-the-art PDH catalysts.

The dynamic catalysis of Ga/ZSM-5 catalysts for propane-CO2 coupling conversion to aromatics and syngas

Alkane coupling with CO2 by metal-containing zeolites catalysis is found to be a promising way to produce aromatics and syngas in recent years, but the real active sites and the role of CO2 are still unclear owing to the quick evolution of the metallic active sites and the complex reaction processes including direct propane aromatization, CO2 hydrogenation, reverse water–gas shift reaction, and propane-CO2 coupling aromatization. Herein, Ga/ZSM-5 catalysts were constructed to study the dynamic evolution of the metallic active sites and the role of CO2 during the propane and CO2 coupling reaction. After optimizing the reaction conditions, a notable propane conversion rate of 97.9% and an impressive aromatics selectivity of 80.6% in hydrocarbons can be achieved at the conditions of 550 °C and CO2/C3H8 of 4. 13CO2 isotope experiments illustrate that C-atoms of CO2 can enter into CO (86.5%) and aromatics (10.8%) during the propane-CO2 coupling reaction process. In situ XANES and FTIR spectroscopies at 550 °C and H2/C3H8 atmosphere reveal that GaOx species can be gradually dispersed into [GaH2]+/[GaH]2+ on the Brønsted acid sites of ZSM-5 zeolite during H2 and/or C3H8 treatment, which are the real active sites for propane-CO2 coupling conversion. In situ CO2-FTIR experiments demonstrate that the [GaH2]+/[GaH]2+ species can react with CO2 and accelerate the propane and CO2 coupling process. This work not only presents a cost-effective avenue for CO2 utilization, but also contributes to the active site design for improved alkane and CO2 activation in coupling reaction system.

Less Is More: Selective-Atom-Removal-Derived Defective MnOx Catalyst for Efficient Propane Oxidation.

Defect manipulation in metal oxide is of great importance in boosting catalytic performance for propane oxidation. Herein, a selective atom removal strategy was developed to construct a defective manganese oxide catalyst, which involved the partial etching of a Mg dopant in MnOx. The resulting MgMnOx-H catalysts exhibited superior low-temperature catalytic activity (T50 = 185 °C, T90 = 226 °C) with a propane conversion rate of 0.29 μmol·gcat.-1·h-1 for the propane oxidation reaction, which is 4.8 times that of pristine MnOx. Meanwhile, a robust hydrothermal stability was guaranteed at 250 °C for 30 h of reaction time. The comprehensive experimental characterizations revealed that the catalytic performance improvement was closely related to the defective structures including the abundant (metal and oxygen) vacancies, distorted crystals, valence imbalance, etc., which prominently weakened the Mn-O bond and stimulated the mobility of surface lattice oxygen, leading to the elevation in the intrinsic oxidation activity. This work exemplifies the significance of defect engineering for the promotion of the oxidation ability of metal oxide, which will be valuable for the further development of efficient non-noble metal catalysts for propane oxidation.

Weakening Mn-O Bond Strength in Mn-Based Perovskite Catalysts to Enhance Propane Catalytic Combustion.

Exploring highly efficient and robust non-noble metal catalysts for VOC abatement is crucial but challenging. Mn-based perovskites are a class of redox catalysts with good thermal stability, but their activity in the catalytic combustion of light alkanes is insufficient. In this work, we modulated the Mn-O bond strength in a Mn-based perovskite via defect engineering, over which the catalytic activity of propane combustion was significantly enhanced. It demonstrates that the oxygen vacancy concentration and the Mn-O bond strength can be efficiently modulated by finely tuning the Ni content in SmNixMn1-xO3 perovskite catalysts (SNxM1-x), which in turn can enhance the redox ability and generate more active oxygen species. The SN0.10M0.90 catalyst with the lowest Mn-O bond strength exhibits the lowest apparent activation energy, over which the propane conversion rate increases by 3.6 times compared to that on the SmMnO3 perovskite catalyst (SM). In addition, a SN0.10M0.90/cordierite monolithic catalyst can also exhibit a remarkable catalytic performance and deliver excellent long-term durability (1000 h), indicating broad prospects in industrial applications. Moreover, the promotional effect of Ni substitution was further unveiled by density functional theory (DFT) calculations. This work brings a favorable guidance for the exploration of highly efficient perovskite catalysts for light alkane elimination.

Enriching GaHx species via co-feeding hydrogen to boost efficient propane dehydrogenation over Ga2O3/Al2O3 catalysts

With the demand for propene and the development of shale gas, propane dehydrogenation is an effective strategy to tackle the tight propene supply. Ga-based catalysts have immense potential for propane dehydrogenation among many environmentally friendly non-precious metal catalysts. Herein, we found that the hydrogen co-feeding not only significantly improved the activity but also enhanced the stability of Ga/Al-R catalyst for propane dehydrogenation. The propane conversion rates at zero reaction time at a hydrogen concentration of 10% was 81 mmolC3H8gcat−1h−1, almost twice as high as in the absence of hydrogen (43.8 mmolC3H8gcat−1h−1). In addition, co-feeding with hydrogen significantly enhanced catalyst stability and resistance to carbon deposition. In-situ IR spectroscopy confirmed that the addition of hydrogen could effectively contribute to the production and enrichment of GaHx species. The H2-D2 exchange and elimination of GaHx species by CO2 experiments demonstrated that GaHx species was the more active site for PDH over Ga/Al-R catalyst.

Effect of Mo content on oxidative dehydrogenation of propane with CO2 over ZnOx catalysts supported on Mo–Zr mixed–oxides

The production of propylene from readily available propane sources is of great importance as it serves as a crucial building block for producing numerous value-added chemicals. Oxidative dehydrogenation of propane with carbon dioxide (ODPC) has been proposed as a viable and eco-friendly approach for simultaneous propylene production and carbon dioxide reduction. In this study, ZnOx catalysts were prepared by supporting them on a range of molybdenum–zirconium (Mo–Zr) mixed–oxides with varying Mo contents, aiming to utilize them for ODPC applications. The incorporation of suitable quantities of Mo in zirconium dioxide (ZrO2) supports increases the surface concentration and enhances the dispersion of ZnOx, thereby demonstrating promotional effects on the surface properties of the supported ZnOx catalysts. Notably, the ZnOx catalyst supported on a Mo–Zr mixed–oxide, with an optimized Mo content, exhibits a propane conversion rate more than two-fold higher than that of the catalyst without Mo in ODPC. Furthermore, the introduction of Mo into the ZrO2 supports effectively inhibits the formation of coke by suppressing the cleavage of C–C bonds in propane. In comparison, the supported ZnOx catalysts with higher Zn loadings, show that a Mo–Zr mixed–oxide support effectively suppresses the formation of bulk ZnOx more than an unmodified ZrO2 support, leading to improved ODPC performance. The promoting effects of Mo emphasize the potential of utilizing mixed–oxide supports for ZnOx catalysts in ODPC, demonstrating a promising opportunity for enhancing catalytic performance.

Activation of Co-O bond in (110) facet exposed Co3O4 by Cu doping for the boost of propane catalytic oxidation

Defects engineering in metal oxide is an important avenue for the promotion of VOCs catalytic oxidation. Herein, the influence of crystal facet of Co3O4 is first investigated for the propane oxidation. An intelligent Cu doping is subsequently performed in the most active (110) facet exposed Co3O4 catalyst. The optimized Cu-Co3O4-110–3 catalyst exhibits a prominently enhanced activity with propane conversion rate of 1.9 μmol g−1 s−1 at reaction temperature of 192 °C and the propane mass space velocity of 60,000 mL g−1 h−1, about 2.4 times that of the pristine Co3O4. Systematic experimental characterizations (XAS, EPR, Raman, TPR, XPS, etc.) combined with density functional theory calculations point out that the incorporated Cu could increase the electrophilicity of nearby O atom and implant beneficial defect structures (lattice distortion, coordination unsaturation, abundant oxygen vacancies, etc.), which could significantly activate Co-O bond in Co3O4, leading to the facilitated generation of active oxygen species as well as promoted oxidation ability. This study could set an illuminating paradigm for the boost of the intrinsic oxidation activity by the precise defect construction in Co3O4 catalyst, which will help drive ahead the pursuit of non-precious metal catalyst for VOCs abatement.

Catalytic process development strategies for conversion of propane to liquid hydrocarbons

The temperature effect on propane dehydroaromatization pathways on the PtZn/SiO2 +ZSM-5 bifunctional catalysts is investigated to develop strategies for propane conversion to valuable liquid hydrocarbons. At high temperature (550 ℃), high dehydrogenation rates and lower monomolecular cracking rates are required to minimize methane formation, leading to primarily propene and BTX (benzene, toluene, and xylenes). By recycling propene in the propane conversion range of 30–45%, > 80% BTX yields is likely achievable at full recycle. At mid temperature (400–450 ℃), the product has high selectivity to gasoline-blending hydrocarbons (butanes, C5+ hydrocarbons, toluene, and xylenes) at 15–25% propane conversions because dehydrogenation rates are moderately high, and oligomerization is more favored than cracking. At low temperature (350 ℃), ~25% propane conversion is achieved and has high selectivity (~60%) to butanes, but the propane conversion rates are likely too low to be practical. While methane formation by monomolecular cracking limits liquid yields at high reaction temperature, hydrogen co-produced at high propane conversions saturates light olefins to make undesired ethane, which becomes major yield loss reaction on the PtZn/SiO2 +ZSM-5 at mid and low temperatures.

Catalytic performance of different zeolites for propane and CO2 coupling to propylene

CO2 hydrogenation to light olefins is an exothermic reaction, while propane dehydrogenation to propylene is an endothermic reaction, and with generating of hydrogen. Coupling of the two reactions can break the equilibrium limit of thermodynamics and dynamics of the single reaction and improve yield of propylene. Therefore, the effects of different crystalline zeolites (HZSM-5, SAPO-34 and Al-SBA-16) on the reactivity of propane coupled with CO2 to propylene were investigated. The properties of different zeolites were characterized by means of XRD, SEM, NH3-TPD, N2 desorption and TG, and the catalytic performance of the three different zeolites in the reaction of propane and carbon dioxide coupling to propylene was investigated in a fixed bed reactor. The experimental results showed that HZSM-5 zeolite had high content of weak acid, large specific surface area and excellent catalytic activity. Typically the propane conversion rate is 10.5%, the CO2 conversion is 3.0%, the propylene selectivity is 38.4% and the yield is 4.0% when the volume ratio of propane to CO2 is 1:4, the reaction pressure is 0.1 MPa, the reaction temperature is 580°C, the catalyst mass is 0.2 g and the space velocity is 6000 mL/(gcat·h).

Modulating the crystallinity of boron nitride for propane oxidative dehydrogenation

In this work, we optimized the catalytic performances of h-BN in propane oxidative dehydrogenation by modulating the catalyst crystallinity. The propane conversion rate per unit specific surface area of the catalyst (-mol C3H8/m2/s) was improved by almost ten times by modulating the crystallinity of BN catalyst, gaining a propylene productivity of about 3.10 μmol g cat−1 s−1. The reaction activity presented a negative relationship with the specific surface area but positively related to the crystallinity of BN. High degree of crystallinity is proved to be beneficial for the binding of O2 to BN by the O2-TPD results and zeta potentials of BN-T, which could probably reduce the energy barrier for the activation of O2 and the formation of active sites. Additionally, the increase in propane conversion with the increase of reaction temperature tends to be gentle when the reaction temperature is above 530 °C, and it is almost equal to zero for O2/C3H8 value increasing from 1.30 to 2.00, indicating an energy-efficient and economical route to convert C3H8 over BN catalyst with high crystallinity.

Co-generation of electricity and olefin via proton conducting fuel cells using (Pr0.3Sr0.7)0.9Ni0.1Ti0.9O3 catalyst layers

As one of the most important feedstocks, light olefins such as propylene and ethylene have drawn worldwide attention. In this work, co-generation of propylene and ethylene with electricity is successfully demonstrated in a propane fueled proton conducting solid oxide fuel cell (P-SOFC) using a novel (Pr0.3Sr0.7)0.9Ni0.1Ti0.9O3 (PSNT) catalytic layer, which is applied to preprocess propane fuel. Highly dispersive nickel nano-particles are in-situ exsolved from the reduced PSNT catalytic layer, which greatly improve propane conversion rate, and thus depress the anode carbon deposition. Importantly, conversion selectivities to propylene and ethylene increase with the current densities, reaching 36 % and 32 %, respectively, at 300 mA cm−2 and 700 °C. This phenomenon indicates that the intrinsic dehydrogenation reactions in anode of P-SOFC benefit light olefins synthesis. Our work demonstrates promising feasibility to co-generate light olefins and electrical power via P-SOFCs, which may shed some new lights on the application of P-SOFCs.

In Ukrainian

Propylene is important olefin with an annual production of roughly 8×10 7 t. A great deal of attention has been paid to the on-purpose propylene production technology, such as propane dehydrogenation in the presence of mild oxidants (CO 2 , N 2 O), due to its potential to make-up the shortfall of propylene supply left by conventional steam cracking of hydrocarbons where propylene is produced as a byproduct of ethylene. The In 2 O 3 –Al 2 O 3 is one of the most effective catalysts for propylene production via oxidative dehydrogenation of propane with CO 2 (PODH-CO 2 ). The textural characteristics of alumina-based compositions depend on their preparation method [Journal of Structural Chemistry. 2011. 52 : 326]. The work presents results on the effect of the preparation method of In 2 O 3 -Al 2 O 3 (YSZ) compositions on their textural and structural characteristics, and hence catalytic performance in the PODH-CO 2 . The catalysts were prepared by the methods of alcoholic coprecipitation of In and Al hydroxides from nitrates of these elements, alcoholic coprecipitation with the following hydrothermal treatment (HT), dry mixing and grinding of In and Al nitrates, impregnation of the supports (commercial Al 2 O 3 and Y-stabilized zirconia (YSZ)) with an aqueous solution of indium nitrate. Catalysts were characterized using the powder X-ray diffraction (Bruker AXS Advance) and nitrogen adsorption-desorption at liquid nitrogen temperature (Sorptomatic 1990 porous material analyzer). Catalysts tests in the PODH-CO 2 were performed in fixed-bed flow reactor at atmospheric pressure, temperature of 600 °C and GHSV = 6000 h –1 . During reaction, the gas reactant contained (vol. %) 2.5 C 3 H 8 , 5–15 CO 2 and a balance of He. The feed and the reaction products were analyzed using on-line GC equipped with the TCD as well as Poropak Q and molecular sieves columns. The catalysts performance in the PODH – CO 2 was characterized by the propane conversion, propylene selectivity and yield, rates of propane conversion and propylene formation normalized per catalyst weight (r С3Н8 (С3Н6) , mmol С 3 Н 8 (С 3 Н 6 )·h –1· g –1 ). In the presence of In 2 O 3 -Al 2 O 3 catalysts the highest selectivity to propylene and propylene yield are achieved for PODH-CO 2 reaction mixture with 10 vol. % CO 2 . The hydrothermal treatment of catalyst In 2 O 3 -Al 2 O 3 (HT) improves its mesoporous structure (specific surface and mesoporous volume), that results in higher selectivity to propylene (51 %) compared to catalysts prepared by other methods (25–36 %). The highest propane conversion and propylene yield are achieved on In 2 O 3 -YSZ catalyst, indicating that the effect of the support nature. In the presence of the developed catalysts In 2 O 3 -Al 2 O 3 (YSZ), a higher propane conversion rate (1.31–2.3 mmol С 3 H 8 ·h –1 ·g –1 ) and a slightly lower rate of propylene formation (0.74 mmol С 3 H 6 ·h –1 ·g –1 ) compared with the catalysts of similar composition In 2 O 3 -Al 2 O 3 (r С3H8 = 1.21 mmol С 3 H 8 ·h –1 ·g –1 , r С3H6 = 0.93 mmol С 3 H 6 ·h –1 ·g –1 ) [Journal of Catalysis. 2010. 272 : 101] are achieved. Thus, the catalytic performance of In 2 O 3 -Al 2 O 3 (YSZ) compositions in the PODH-CO 2 depends on both the support nature and their porous structure, which can be optimized by their preparation method.

Hierarchical Ga-MFI Catalysts for Propane Dehydrogenation

We report the synthesis, characterization, and enhanced propane dehydrogenation properties of hierarchical Ga-MFI zeolite catalysts synthesized by two different methods: (i) repetitive branching and (ii) utilization of a long chain alkyl SDA. Structural, compositional, and morphological characterizations confirm that the Ga-MFI catalyst materials have hierarchical structures including micropores and mesopores in a single particle and show that Si/Ga ratios comparable to bulk Ga-MFI catalysts can be obtained. Acid site analysis using NH3-TPD and pyridine adsorption followed by in situ IR spectroscopy allowed quantification of the number and types of acid sites present and show that the hierarchical catalysts have considerably higher Lewis acid site concentrations than the bulk catalysts. The hierarchical Ga-MFI catalysts show superior PDH performance (at 600 °C) compared to bulk Ga-MFI catalysts. Propane conversion rates are increased 2–6-fold and propylene selectivities are 10–100% higher. We also examine...

A Mesoporous Cobalt Aluminate Spinel Catalyst for Nonoxidative Propane Dehydrogenation

AbstractA mesoporous CoAl2O4 spinel (Co‐Al) is synthesized by a one‐step evaporation‐induced self‐assembly (EISA) method. N2 physisorption and TEM are used to demonstrate the presence of mesopores within the Co‐Al material. The spinel crystal structure of Co‐Al, in which Co occupies tetrahedral (Td) sites, is confirmed by using XRD and UV/Vis spectroscopy. In nonoxidative propane dehydrogenation at 550 °C, a propane conversion of approximately 8 % is observed for Co‐Al with a >80 % propylene selectivity, which corresponds to a turnover frequency of 5.1 h−1 based on an estimation of the number of active Co sites by using NH3 temperature‐programmed desorption. A much higher propane conversion rate and a circa 80 % propylene selectivity is observed upon reaction at 600 °C. Continuous deactivation of the catalyst is observed for Co‐Al at this elevated temperature. In situ X‐ray absorption spectroscopy results suggest that Co remains as a Td Co2+ species under the reaction conditions. The Td Co2+ sites within the Co‐Al material are thus proposed to act as Lewis acidic active sites; this acidity is verified using IR spectroscopy with pyridine as a probe molecule.

Thermodynamic equilibrium analysis of combined dry and steam reforming of propane for thermochemical waste-heat recuperation

The thermochemical waste-heat recuperation is one for perspective way of increasing the energy efficiency of the fuel-consuming equipment. In this paper, the thermochemical waste-heat recuperation (TCR) by combined steam-dry propane reforming is described. To understand the influence of technological parameter such as temperature and composition of inlet gas mixture on TCR efficiency, thermodynamic equilibrium analysis of combined steam-dry propane reforming was investigated by Gibbs free energy minimization method upon a wide range of temperature (600–1200 K) and different feed compositions at atmospheric pressure. The carbon and methane formation was also calculated and shown. From a thermodynamic perspective, the TCR can be used for increasing energy efficiency at temperatures above 950 K because in this range the maximum conversion rate is reached (from 1.22 to 1.30 for the different feed composition). Approximately 10 mol of synthesis gas can be generated per mole of propane at the temperatures greater than 1000 K. Furthermore, the propane conversion rate and yield of hydrogen are increased with the addition of extra steam to the feed stock. Also, undesirable carbon formation can be eliminated by adding steam to the feed. The thermodynamic equilibrium analysis was accomplished by IVTANTHERMO which is a process simulator for thermodynamic modeling of complex chemically reacting systems and several results were checked by Aspen-HYSYS.

Kinetics of low-temperature steam reforming of propane in a methane excess on a Ni-based catalyst

Systematic studies were performed on low-temperature steam conversion or low-temperature steam reforming (LTSR) of propane in an excess of methane on a Ni-based catalyst. The LTSR of the methane–propane mixture is a two-stage process involving the irreversible steam conversion of propane into carbon dioxide and hydrogen and reversible methanation of carbon dioxide. Above ~250°C, the methanation of carbon dioxide is quasi-equilibrium. The rate of propane conversion during the LTSR of the methane–propane mixture is first-order based on propane; its activation energy is ~120 kJ/mol and is almost independent of the methane, carbon dioxide, hydrogen, and steam concentrations. This very simple macrokinetic scheme allows us to correctly describe the experimental data and predict the temperature and flow rate of the mixture at which complete conversion of propane is achieved.

Propane dehydrogenation catalyzed by gallosilicate MFI zeolites with perturbed acidity

The propane dehydrogenation (PDH) behavior of gallosilicate MFI catalysts synthesized in the presence of 3-mercaptopropyl-trimethoxysilane (MPS) is investigated. MPS addition to the zeolite synthesis gel results in gallosilicate molecular sieves with reduced Brønsted acidity and enhanced Lewis acidity, as shown by combined NH3 temperature-programmed desorption (TPD), isopropylamine (IPA) TPD and IR analysis of pyridine-loaded catalysts. In particular, the gallosilicate MFI catalysts prepared using MPS provide a significant concentration of strong Lewis acid sites, which are important in controlling the selectivity of PDH. Enhanced PDH performance with higher propane conversion rates and improved propylene selectivity with limited cracking and aromatization products are obtained from the catalysts synthesized with MPS. The gallosilicate MFI materials prepared using MPS are compared with a benchmark chromia-alumina catalyst, and the gallosilicate materials have a lower rate of deactivation (>50% lower) but slightly inferior propylene selectivity (Ga-MFI: 75%; Chromia-Alumina: 85%).

Comparative study of propane steam reforming in vanadium based catalytic membrane reactor with nickel-based catalysts

The performance of catalytic membrane reactor with Pd-coated V membrane was examined for steam reforming of propane. The long term reforming experiment confirmed the stability of the V membrane with high hydrogen selectivity and permeability. The effect of types of hydrogen permeable membranes on the performance of the catalytic membrane reactor was studied by comparing Pd-coated V, Pd–23Ag, and Pd–10Ag membranes. The types of hydrogen separation membranes (i.e. hydrogen removal rates) did not have a marked effect on the propane conversion rates, while the product compositions were largely influenced by the hydrogen removal rate. Varying metal oxide supports of Ni-catalysts resulted in significant differences in the product compositions. Further, the evaluation of various catalyst-support systems (9wt%Ni–1wt%M/CeO2, M = Co, Pt, Ag, Ru) revealed that hydrogen yield was the highest when 1wt%Ag was added to Ni/CeO2. However, it was also found that excessive secondary metal additions can have negative impact on the catalytic behaviour of parent catalysts.

Oxidative dehydrogenation of propane with nitrous oxide over Fe–O–Al species occluded in ZSM-5: Reaction and deactivation mechanisms

Fe-ZSM-5 was prepared via solid-state exchange method using ferrocene as iron precursor and applied as a model catalyst to investigate the reaction and deactivation mechanisms of the oxidative dehydrogenation of propane (ODHP) with nitrous oxide. Characterization results reveal that after severe calcination highly isolated Fe–O–Al species are the only exposed iron sites detectable, which account for ca. 60% of the total iron species in Fe-ZSM-5. Results from temperature-programmed experiments and in situ DRIFT spectroscopy suggest that the chemisorption of nitrous oxide on Fe–O–Al species leads to the formation of stable mono-oxygen species, which can react with gaseous propane to produce propylene with high selectivity. The accumulation of organic species in the catalyst is observed during the reaction, and the major organic species are determined to be alkylbenzenes. The accumulation rate and the specific constitution of alkylbenzenes are found to depend on the relative partial pressures of propane and nitrous oxide: lower N2O/C3H8 ratios result in formation of aromatics with smaller kinetic diameter, which are accumulated at a lower rate. This leads to lower deactivation rates and longer catalyst lifetimes. Remarkably, a superior stable propane conversion rate of ca. 13mmolgcat−1h−1 and a propylene production rate of ca. 6mmolgcat−1h−1 can be kept for >40h with a N2O/C3H8 ratio of 1:2.

Combustion of propane with Pt and Rh catalysts in a meso-scale heat recirculating combustor

The results obtained from the combustion behavior of propane over platinum and rhodium catalysts in a meso-scale heat recirculating combustor are presented. The extinction limits, conversion, product selectivity/yield, and activation energy using the two catalysts were compared in an effort to predict their performance using a liquid fuel. The extinction limits were also compared to those of non-catalytic combustion in the same combustor. The results showed that the use of a catalyst greatly expanded the range of stable operating conditions, in terms of both extinction limits and flow rates supported. The Rh catalyst was found to exhibit a higher propane conversion rate, reaching a maximum of 90.4% at stoichiometric conditions (as compared to only 61.4% offered by the Pt catalyst under lean conditions), but the Pt catalyst had superior CO2 selectivity for most of the examined conditions, indicating more of the heat released being used for product formation as opposed to being lost to the environment. However, despite having a higher rate of heat loss, the combustion with the Rh catalyst produced an overall higher amount of enthalpy than the Pt due to its superior fuel conversion. The Pt catalyst also had a significantly smaller activation energy (13.8kJ/mol) than the Rh catalyst (74.7kJ/mol), except at equivalence ratios richer than Φ=1.75 (corresponding to catalyst temperatures below 500°C), where it abruptly changed to 211.4kJ/mol, signifying a transition from diffusion-limited reactions to kinetically limited reactions at this point. The results reveal that Rh would be a more suitable catalyst for use in liquid-fueled meso-scale combustors, as fuel conversion has been found to be a limiting factor for combustion stability in these systems, and as its higher output energy allows for greater flexibility of use.