Propylene Yield Research Articles

Influence of Ni/Mo ratio on the structure-performance of ordered mesoporous Ni-Mo-O catalysts for oxidative dehydrogenation of propane

Abstract A series of ordered mesoporous Ni-Mo-O catalysts with different ratios of Mo/Ni were prepared by a two-step method, which firstly prepared ordered mesoporous NiO by hard template method and then impregnation with Mo precursor. And their catalytic performance were tested for propane oxidative dehydrogenation. The catalysts were characterization by XRD, N2-adsorption, TEM, XPS, H2-TPR and Raman analyses. It can avoid the dissolution of surface Mo species during etching silica template by a two-step method. And the catalysts with low Mo loading amounts show highly ordered mesoporous structure. A highly proportional β-NiMoO4 phase can exist stably in Ni-Mo-O catalysts at room temperature. And the in-situ Raman results demonstrated the transformation of α-NiMoO4 to β-NiMoO4 with the increasing of temperature. The transformation temperature in this work is relatively low (250 °C) due to the promotion of NiO. The catalyst with Mo/Ni of 0.4 shows the highest activity with the propene yield of 15.6%. The reasons may be from the high β-NiMoO4/α-NiMoO4 ratio, the mesoporous structure and the suitable redox ability.

Dehydrogenation of Propane to Propylene Using Promoter-Free Hierarchical Pt/Silicalite-1 Nanosheets

Propane dehydrogenation (PDH) is the extensive pathway to produce propylene, which is as a very important chemical building block for the chemical industry. Various catalysts have been developed to increase the propylene yield over recent decades; however, an active site of monometallic Pt nanoparticles prevents them from achieving this, due to the interferences of side-reactions. In this context, we describe the use of promoter-free hierarchical Pt/silicalite-1 nanosheets in the PDH application. The Pt dispersion on weakly acidic supports can be improved due to an increase in the metal-support interaction of ultra-small metal nanoparticles and silanol defect sites of hierarchical structures. This behavior leads to highly selective propylene production, with more than 95% of propylene selectivity, due to the complete suppression of the side catalytic cracking. Moreover, the oligomerization as a side reaction is prevented in the presence of hierarchical structures due to the shortening of the diffusion path length.

Surface modification of H-ZSM-5 with organo-disilane compound for propylene production from dimethyl ether

Abstract The efficient modification of zeolites for improving their catalytic properties is a significant subject of microporous materials chemistry. H-ZSM-5 zeolite is a potent catalyst of the production of propylene as an important start material of a variety of chemical products, which is mainly obtained from fossil resources. Recently, the production of propylene using non-fossil carbon resources are desired because of the depletion risk of fossil fuels and global warming problem. Dimethyl ether (DME) conversion to propylene is actively studied using acid catalysts as an alternative synthetic route of propylene. This paper reports the propylene production from DME using H-ZSM-5 catalyst whose surface was modified with an organo-disilane compound, 1,4-bis(hydroxydimethylsilyl)benzene. An H-ZSM-5 catalyst surfacely modified with the disilane compound produced propylene from DME in higher yield than original (non-modified) H-ZSM-5. Air flow treatment at 480 °C effectively regenerated the modified H-ZSM-5 that was deactivated by coke formation during the reaction, and this regenerated catalyst had a nearly equivalent activity of the propylene production to the catalyst before deactivation. The polycyclic aromatic compounds formed from the benzene ring of the disilane compound that covered the exterior surface of H-ZSM-5 controlled the catalytic activity to increase the yield of propylene.

Borealis to construct PDH plant for propylene production in Belgium

The production of renewable propene from biomass-derived ethanol is highly significance for sustainable chemical production. Herein, propene was produced directly from bioethanol over ZnCeOx and HBeta composites. Although the basicity of ZnCeOx is necessary for the first step of ethanol dehydrogenation, catalyst acidity is much more crucial for propene selectivity. Si/Al ratio of HBeta and its ratio to ZnCeOx oxide were optimized to be 43 and 1:10, respectively. This hybrid catalyst gives an over 55 % yield of propene and only 3% yield of ethene under optimized conditions. NH3-TPD and 31P MAS NMR using trimethylphosphine oxide as a probe show that more weak Brönsted acid sites and relatively strong Lewis acid sites in composites significantly increase propene selectivity. Ethanol-TPD-MS, in situ DRIFTS and acetone model reaction suggest the possible reaction pathways could be ethanol→acetaldehyde→ethyl acetate→acetone→isopropanol→propene. The composite catalyst shows no obvious deactivation, propene selectivity remains around 50 % after three regeneration cycles.

Oxidative dehydrogenation of propane over Mg-V-O oxides supported on MgO-coated silica: Structural evolution and catalytic consequence

Supported Mg-V-O oxides were prepared by co-impregnation of magnesium and vanadium citrates with MgO-coated mesoporous silica (SBA-15). Their structures were characterized by complementary techniques including powder X-ray diffraction, Raman spectroscopy, diffuse reflectance UV–vis spectroscopy and transmission electron microscopy. These catalysts were examined in oxidative dehydrogenation (ODH) of propane to propylene, and the reaction kinetic parameters of k1/k2 and k3/k1 were analyzed, which represent the ratios of the rate constants for primary propane ODH (k1) to propane combustion (k2) and that for secondary propylene combustion (k3) to k1, respectively. Characterization results show the structural evolution of the vanadium species from isolated VO4 monovanadates to Mg3V2O8 crystallites, without formation of crystalline V2O5, with increasing the vanadium content from 1.7 wt% to 25.6 wt%. Dispersed monovanadates exhibited higher propane ODH rates than Mg3V2O8 crystallites, in line with their higher reducibility probed by temperature-programed reduction in H2, but they were less selective to propylene due to the favorable propylene combustion over its formation, as reflected by the higher k3/k1 ratios. The supported Mg3V2O8 crystallites with sizes of about 15–30 nm, relative to those of above 30 nm, were found to be intrinsically more selective for the propane ODH, consistent with their higher k1/k2 and lower k3/k1 ratios. Consequently, they offered the superior selectivities and yields of propylene at higher propane conversions. Such understanding on the intrinsic catalytic properties of the Mg-V-O oxides and particularly Mg3V2O8 crystallites provides new insights into the structural requirement for the propane ODH reaction, beneficial to design of more efficient Mg-V-O-based catalysts for the production of propylene.

Roles of the free radical and carbenium ion mechanisms in pentane cracking to produce light olefins

In order to explore the roles of the free radical and carbenium ion mechanisms in alkane cracking to produce light olefins, pentane cracking tests have been carried out over a zeolite catalyst at 600–800 °C, and a particular attention has been paid to the measurement of the product distribution. The cracking modes for pentane included “uncatalytic pyrolysis” following the free radical mechanism, “catalytic cracking” following the carbenium ion mechanism, and “catalytic pyrolysis” following the dual mechanisms (involving the concurrence of the free radical and carbenium ion mechanisms): (1) The free radical mechanism did not occur until 700 °C under the studied conditions, and it led to an ethylene-rich product distribution. (2) Zeolite catalyst initiated the carbenium ion mechanism that led to a propene-rich product distribution. (3) The dual mechanisms exhibited a wide distribution of ethylene and propene, which approximated to that of the free radical mechanism from that of the carbenium ion mechanism with increasing reaction temperature. The kc/kt and kcp/(kt+kc) parameters have been proposed to determine the relationship between the free radical and carbenium ion mechanisms. It was found that the carbenium ion mechanism greatly contributed to pentane cracking at the low temperatures, and the free radical mechanism took over the dominant position at the high temperatures. A proper proportion between the carbenium ion and free radical mechanisms promoted pentane cracking. In addition, yield of propene plus ethylene (P + E) and ratio of propene to ethylene (P/E) have been employed to evaluate the light olefins production. In the research scope, pentane cracking at 740 °C over 200 mg K-ZSM-22 zeolites seemed the optimal process, which has taken the consumption of energy and catalyst as well as the production and distribution of light olefins into consideration.

One‐Pot Catalytic Conversion of Poly(3‐hydroxybutyrate) to Propylene at 240 °C

AbstractPoly(3‐hydroxybutyrate) (PHB), a renewable feedstock from microorganisms, was a good resource for propylene production by a simple one‐pot reaction. The reaction was catalyzed by triruthenium dodecacarbonyl (TD) at relatively mild temperature (240 °C), and the yield and selectivity of propylene reached 22.9 wt% and 46.8%, respectively. A small part of hydrocarbon oils reached 9 wt% was also obtained, which contained 79.1 wt% of carbon and 12.3 wt% of hydrogen, with a theoretical high heating value of 41.2 MJ/kg.

3D-printed ZSM-5 monoliths with metal dopants for methanol conversion in the presence and absence of carbon dioxide

The development of effective strategies to utilize CO2 as a renewable feedstock for producing commercially-viable products is an interesting challenge to explore new concepts and opportunities in catalysis and industrial chemistry. In this study, 3D-printed ZSM-5 monoliths doped with Ga2O3, Cr2O3, CuO, ZnO, MoO3, and Y2O3were synthesized using the state-of-art 3D printing technique. The physicochemical properties of the catalysts were characterized by X-ray diffraction, N2 physisorption, NH3 and CO2 temperature-programed desorption and H2 temperature-programmed reduction. The promotional effect of doped metals on catalytic performance of 3D-printed ZSM-5 monoliths in methanol to hydrocarbon (MTH) reaction in the presence and absence of CO2 was investigated. Results indicated that both metal dopants type and reaction atmosphere greatly influence catalyst stability and product distribution. The yield of light olefins was enhanced over all metal-doped 3D-printed ZSM-5 monoliths in N2 atmosphere (absence of CO2), however, CO2 atmosphere did not favor the production of light olefins. Although selectivity toward ethylene slightly decreased, the propylene yield was almost constant after switching N2 to CO2 in MTH reaction at 400 °C. Furthermore, it was found that Y- and Zn-doped ZSM-5 monoliths exhibited higher yield of light olefins and BTX compounds in the in the absence and presence of CO2, respectively.

Potential Production of Olefins in Pyrolysis of Algerian Gas Condensate Compounded with Ethane

The present work aims to investigate the possibility of substituting ethane, usually used as pyrolysis feedstock, by the Algerian gas condensate compounded with ethane. Several experiments have been setup using different percentage dilutions (5, 10, and 20%) of Algerian gas condensate and its fractions (light, medium and heavy) compounded with ethane. The impacts of temperature, steam flow and flows of material on the yield and composition of pyrolysis products have also been investigated. High yields of ethylene (19 to 36%) and propylene (9 to 20%) were obtained in the pyrogas. The present study demonstrates the potential of the Algerian gas condensate product which can be valorized and used to enhance the yields of ethylene and propylene used in the production process of polyethylene and polypropylene.

Catalytic efficiency of activated carbon functionalized with phosphorus-containing groups in 2-propanol dehydration

The functionalization of activated carbon (AC) by P-containing groups was conducted, and their thermal desorption was studied. Depending on the used method, the functionalized AC contains 0.5–1.45 mmol/g of acidic groups acting in catalytic 2-propanol dehydration. All catalysts showed 100% conversion of 2-propanol to propylene. The catalytic activity does not change with time under isothermal conditions and during their repeated use in catalysis, for 3 cycles of heating-cooling. In fact, the yield of propylene remains stable; it does not decrease with each cycle. Preliminary oxidation with nitric acid causes a small increase in the catalytic activity.

Selective Production of Propylene from Methanol over Monolith-Supported Modified ZSM-5 Catalysts

The catalytic activity of ZSM-5 zeolites with a SiO2/Al2O3 molar ratio of 30, 50, 80, 280, and 410 was investigated in a fixed bed continuous flow reactor system and was found that the ZSM-5 zeolite with SiO2/Al2O3 molar ratio of 280 (HZ-280) exhibited best catalyst performance. The optimized reaction conditions achieved were 500 °C, 1 bar pressure, and weight hourly space velocity of 15 h–1 using methanol as feed. At optimum reaction conditions, HZ-280 exhibited propylene selectivity of 47.3% and propylene yield 17.4% with 100% methanol conversion. HZ-280 zeolite was modified with P, Ce, Fe, and La to select the best promoter to enhance propylene selectivity and yield. The best-modified catalyst obtained was HZ-280 with 0.1 wt % phosphorus loading, which further improved propylene selectivity by 14% and yield by 24.7%. Then, the monolith structured catalysts were prepared by single-layer (6.8%), double-layer (10.3%), and triple-layer (13.1%) coating of HZ-280 catalyst. HZ-280 single-layer-coated monolith...

Zone method based coupled simulation of industrial steam cracking furnaces

Coupled furnace/reactor simulations were conducted to study industrial steam cracking furnaces. Zone method was performed for the firebox side, and the one-dimensional reactor model COILSIM1D was used for the reactor side. In the firebox model, the Hottel zone method model was used to calculate the radiation heat transfer. The flow and combustion model were based on the results of computational fluid dynamics (CFD) simulations. A comparison was made among the results of zone method simulation, CFD simulations, and industry or design data, and the zone method simulation results were found to agree well with industry or design data. For the secondary burners installed 0.6 m away from the primary burners, the tube skin temperature and heat flux obtained with the zone method were higher than that under CFD simulation in the middle of reactor tube, and after 15 m they were lower than that obtained with CFD simulation. The higher process gas temperature led to a faster increase in ethene yield using the zone method compared with CFD simulation, whereas a shift in the maximum propene yield upstream of the reactor occurred with the zone method. This method was suitable for real-time operation optimization of industrial steam cracking units.

Enhanced stability and propylene yield in methanol to light olefins conversion over nanostructured SAPO‐34/ZSM‐5 composite with various SAPO‐loadings

AbstractNanostructured core‐shell silicoaluminophosphate (SAPO)‐34/zeolite socony mobil (ZSM)‐5 composite has been synthesized with various SAPO‐34 loadings in order to control light olefins selectivity and increase its lifetime in methanol to olefins process. Physicochemical properties and catalytic performance of SAPO‐34/ZSM‐5 composite catalyst were different, compared with the parent SAPO‐34 and ZSM‐5. As‐synthesized samples were characterized by different methods such as X‐Ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller, energy‐dispersive X‐ray, Fourier transform infrared spectroscopy, and NH3‐temperature‐programmed desorption techniques. By increasing SAPO‐34 content in composite catalysts, relative crystallinity of CHA‐phase (chabazite) was enhanced, whereas it was decreased for MFI‐phase. Also, surface area improved by increasing SAPO‐34 loading in core‐shell composite catalysts. The results of the activity test showed that lifetime remarkably increased by using composite catalysts. Compared with the parent SAPO‐34 and ZSM‐5, the composite catalyst with 80% SAPO‐34 loading showed higher methanol conversion and olefins selectivity with time on stream. This is due to the synergic effect between SAPO‐34 and ZSM‐5 zeolites in composite catalyst.

Propane Dehydrogenation on Chromium Oxide and Gallium Oxide Catalysts in the Presence of CO2

The catalytic and physicochemical properties of GaOx/SiO2 and CrOx/SiO2 supported onto silica gels as catalysts for propane dehydrogenation were studied with the use of stationary and nonstationary (a response method) techniques, TPR-H2, TPD-NH3, and UV spectroscopy, and the effect of CO2 on the course of dehydrogenation reaction was examined. It was found that the relatively low acidity of silica gels prevents intense coke deposition and has a positive effect on the stability of catalyst operation. At the same time, the acid hydroxyls of these supports play an important role in the formation of a disperse active surface. In the case of the GaOx/SiO2 catalysts, the insufficient dispersity of the active phase is a reason for the low specific activity of these systems. It was found that the appearance and growth of catalytic activity with temperature was accompanied by the formation of the reduced forms of gallium oxide, the fraction of which was limited under the conditions of dehydrogenation (600°C). It was established that CO2 hindered the adsorption of propane on the surface of catalysts to decrease its conversion; at the same time, it prevented the adsorption of propylene and its further conversion into coke. In the case of the chromium systems, the increase in the yield of propylene and in the stability of operation due to the oxidation of coke and hydrogen upon the introduction of CO2 prevailed over a negative effect. This negative effect was more pronounced for the gallium catalysts, and this led to a decrease of the propylene yield.

Grand Canonical Monte Carlo Simulations of Ethanol Conversion to Propylene Over Zeolite Catalysts

Ethanol conversion reactions were carried out over H-ZSM-5(40) and H-LEV (40) catalysts. For H-ZSM-5 (40), the yield of propylene was almost constant at 20 % during continuous experiments for 8 h. Higher initial propylene yield reached 31 % over H-LEV (40) catalyst. However, there is almost no propylene obtained over H-LEV (40) catalyst after 2 h. Results show that H-ZSM-5 (40) catalyst exhibited higher stability than H-LEV (40). The lower stability of H-LEV (40) is probably due to coke deposition. Grand Canonical Monte Carlo simulations were used to understand how the two zeolites affect their adsorption performance in the ethanol conversion reaction. The isosteric heat of ethylene in ZSM-5(40) zeolite at 303 K has been calculated to verify the rationality of model construction and simulation parameters. It is found that the adsorption of ethanol, ethylene and propylene in H-LEV(40) was stronger, which led to the more difficult desorption of products and higher content of coke deposition. A strong adsorption of reactants and products in H-LEV should be avoided in order to prevent the formation of coke. The simulation results are consistent with the experimental results.

Conversion of chloromethane to propylene over fluoride-treated H-ZSM-35 zeolite catalysts

H-ZSM-35 with 2D channel intersections has been first found to be an effective catalyst over chloromethane transformation into propylene. Fluoride treatment is further introduced to improve the catalytic performance. With a proper concentration of fluoride treatment, the selectivity and yield of propylene can be enhanced significantly while a high propylene/ethylene ratio is achieved. Detailed characterizations demonstrate that dealumination caused by fluoride treatment results in a reduction in acidic sites, which is responsible for the improvement of catalytic performance.

Catalytic transformation of ethylene to propylene and butene over an acidic Ca-incorporated composite nanocatalyst

The direct conversion of ethylene to propylene (ETP reaction) has become critically important due to the growing demands for propylene as one of the key building blocks in the petrochemical industries and the depletion of appropriate resources for propylene production. In the present study, an acidic metal-incorporated composite nanocatalyst has been prepared and characterized using XRD, FTIR, FESEM, EDX, NH3-TPD, and N2 physisorption analyses and applied to the ETP reaction. The maximum conversion of 77.8% was achieved over the catalyst at 723 K. The highest propylene yield (34.6 wt%) was obtained at 773 K, however. An increasing trend with temperature (573–823 K) was evident for the total light olefins selectivity, which amounted to 78.7 wt% at 823 K. The reaction rate increased constantly to 258 mol/(kg s) with the increase in the ethylene partial pressure. The remarkable performance of the composite catalyst in terms of propylene and butenes yields and its distinguished stability during the ETP reaction compared to the closely relevant HZSM-5 and HSAPO-34 counterparts, was attributed to both an appropriate porosity and a good compromise between the strength and amount of the acidic sites to an interestingly one-mode moderate acidity.

Synthesis of layered magnesium-aluminum hydroxide on the γ-Al2O3 surface for modifying the properties of supported platinum catalysts

Layered magnesium-aluminum hydroxides of hydrotalcite-like structure were synthesized on the surface of γ-Al2O3. The synthesis was performed via the interaction of aluminum and magnesium hydroxides and carbonate ions in the pores of alumina support. Novelty of the approach was that the synthesis involved the boehmite phase AlO(OH) that formed directly on the surface of γ-Al2O3 under hydrothermal conditions. This approach provides fixation of the forming layered phase on the surface of initial support and retains textural parameters of the support. The formation of a layered structure on the γ-Al2O3 surface was confirmed by XRD analysis and electron microscopy studies. Investigation of the H2[PtCl6] anchoring on γ-Al2O3 with supported magnesium-aluminum hydroxide by UV–vis DRS, 195Pt NMR and HRTEM showed that platinum was adsorbed on the surface as chloride forms of the complexes with a low degree of hydrolysis even at a low metal content. Catalytic properties of the synthesized supported platinum catalysts were examined in a model reaction of propane dehydrogenation. In comparison with the alumina-platinum catalyst, the modified sample showed a better stability at a somewhat higher yield of propylene because the formation of heavy products was suppressed.

Effect of particle shape on catalyst deactivation using particle-resolved CFD simulations

A method has been demonstrated using particle-resolved CFD simulations to simulate the transient catalyst deactivation due to carbon formation process and its impact on the particle properties. Preliminary simulations with cylindrical particles and propane dehydrogenation reactions showed higher carbon accumulation for the near-wall particles due to the presence of wall heat flux. Significant gradients of carbon concentration within the particle pointed to the presence of diffusion limitations. The accumulated carbon decreased the rate of the reactions thereby decreased the propene formation with time. Later, the effect of particle shape on the catalyst deactivation was investigated using five different particle shapes with constant particle volume, but varying in particle surface area. Considerable variations in the accumulated carbon were observed both with respect to the particle position and the particle shapes. The initial reaction rate increased with the particle surface area due to reduced diffusion limitation, but after a certain time, it decreased with particle surface area due to faster catalyst deactivation. As a result, the propane conversion and propene yield decreased with particle surface area. Also, the propene yield to ΔP ratio decreased with particle surface area due to smaller ΔP offered by particles with the lower surface area. Therefore, the present work showed that the particles with the lower surface area are favorable for propane dehydrogenation process due to slower catalyst deactivation leading to higher conversion and longer operating time. The trilobe particle shape gave the highest propane conversion and highest propene yield to ΔP ratio.

Synthesis of SSZ-13 zeolite in the presence of dimethylethylcyclohexyl ammonium ion and direct conversion of ethylene to propylene with the SSZ-13

The conversion of Y zeolites having wide silica/alumina ratio (SAR, 5.1–80) into SSZ-13s was carried out in the presence of N,N,N-dimethylethylcyclohexylammonium (DMCHA) ion, as an organic structure directing agent (OSDA). SSZ-13 zeolites could be obtained from siliceous Y zeolites; however, another phase, analcime (ANA) was obtained when aluminous Y zeolites (SAR: 5.1–12) were converted. Sodium silicate was used not only to successfully convert the aluminous Y zeolites into SSZ-13s but also to increase the SAR of the obtained SSZ-13 zeolites. The synthesis of SSZ-13 with DMCHA was possible in the absence of any seed, which is advantageous in the viewpoint of both the expense and convenience of the synthesis. Moreover, the synthesized SSZ-13s were utilized in the direct conversion of ethylene-to-propylene (ETP). Moderately siliceous SSZ-13s (SAR: 18–24) showed better performance in ETP than aluminous or siliceous SSZ-13s. DMCHA-derived SSZ-13 was also competitive or better in ETP than SSZ-13s prepared with other reported templates including N,N,N-trimethyl-1-adamantanamine hydroxide (TMAda-OH). For example, the maximum propylene yield in ETP over SSZ-13s (with similar SAR of 15–19) prepared with choline chloride, tetraethylammonium hydroxide (TEA-OH), TMAda-OH, and DMCHA-Br were 51, 61, 65 and 68%, respectively. Based on the syntheses and ETP reactions, DMCHA ion can be recommended as a versatile/inexpensive OSDA for the conversion of Y (with wide SARs) into SSZ-13 zeolites which can be effective in ETP reaction. However, further work is required to understand the reason of the competitiveness of the DMCHA-derived SSZ-13 and the effect of the SAR on the propylene yield in ETP.