Propylene Yield Research Articles

Bioethanol Conversion into Propylene over Various Zeolite Catalysts: Reaction Optimization and Catalyst Deactivation.

Catalytic conversions of bioethanol to propylene were investigated over different zeolite catalysts. H-ZSM-5 (SiO2/Al2O3 = 80) was found to be the most effective for propylene production. Furthermore, H-ZSM-5 (SiO2/Al2O3 = 80) was investigated under different variables of catalytic reaction (calcination temperature, feed composition, reaction temperature, and time on stream) for the conversion of ethanol to propylene. The H-ZSM-5(80) catalysts calcined at 600 °C showed the highest propylene yield. The moderate acidic site on ZSM-5 is required for the production of propylene. The activity on ZSM-5 is independent of the ethanol feed composition. H-ZSM-5 catalyst deactivation was observed, owing to dealumination. The highest propylene yield was 23.4% obtained over HZSM-5(80). Propylene, butene, and ≥C5 olefins were formed by parallel reaction from ethylene. Olefins were converted to each paraffin by sequential hydrogenation reaction. HZSM-5(80) catalyst is a promising catalyst not only for ethanol but also for the conversion of bioethanol to light olefins.

Regulating Ni–O–V bond in nickel doped vanadium catalysts for propane dehydrogenation

Supported vanadium catalysts are commonly investigated in industrial propane dehydrogenation (PDH) but still remain a great challenge to achieve high propylene selectivity and productivity. Here, Ni species were adopted to regulate the micro-structure of V2O5 supported by γ-Al2O3 via incipient wetness impregnation method. The Ni-doped vanadium catalyst exhibits an optimal propylene yield of 31.88% with a superior propylene selectivity of 85.91% compared to undoped catalyst with a propylene yield of 20.49% (propylene selectivity of 80.77%). Experimental characterizations (such as XPS, XAFS and Raman studies) and DFT calculations were combined to support that the Ni–O–V bonds are active sites for PDH and could promote the charge redistribution from Ni to V based in the Ni–O–V bonds, which greatly strengthens the adsorption of C3H8 over V sites. This endows the Ni-doped vanadium catalyst high propane conversion and superior propylene selectivity.

Organic-free modulation of the framework Al distribution in ZSM-5 zeolite by magnesium participated synthesis and its impact on the catalytic cracking reaction of alkanes

Al distribution engineering is an effective way to tune the catalytic performance of ZSM-5 zeolite. In the present work, a series of [Al, Mg]-ZSM-5 with different Mg contents were obtained by hydrothermal synthesis method. For comparison, Mg/ZSM-5 with a comparable Mg content were also prepared using the conventional impregnation method. Characterizations of XPS-sputtering, H2-TPR and Py-IR indicated the distribution and coordination structures of Mg in the samples obtained by the two preparation methods were quite different. Besides, the introduction of magnesium by hydrothermal synthesis well regulates the location of framework Al, which is not possible by the impregnation method. 27Al MAS NMR and UV–vis-DRS of Co2+-exchanged zeolites demonstrated [Al,1.0 Mg]-ZSM-5 has less aluminum in the channel intersections compared to conventional HZSM-5. Finally, the significantly lower content of “Al pairs” in [Al,1.0 Mg]-ZSM-5 inhibits the hydride transfer process, resulting in higher yields of propylene in n-octane and crude oil catalytic cracking reactions.

Modeling of propane dehydrogenation combined with chemical looping combustion of hydrogen in a fixed bed reactor

A redox process combining propane dehydrogenation (PDH) with selective hydrogen combustion (SHC) is proposed, modeled, simulated, and optimized. In this process, PDH and SHC catalysts are physically mixed in a fixed-bed reactor, so that the two reactions proceed simultaneously. The redox process can be up to 177.0% higher in propylene yield than the conventional process where only PDH catalysts are packed in the reactor. The reason is twofold: firstly, SHC reaction consumes hydrogen and then shifts PDH reaction equilibrium towards propylene; secondly, SHC reaction provides much heat to drive the highly endothermic PDH reaction. Considering propylene yield, operating time, and other factors, the preferable operating conditions for the redox process are a feed temperature of 973 K, a feed pressure of 0.1 MPa, and a mole ratio of H2 to C3H8 of 0.15, and the optimal mass fraction of PDH catalyst is 0.5. This work should provide some useful guidance for the development of redox processes for propane dehydrogenation.

Influence of the Porous Structure of V2O5-ZrO2-SiO2 Catalyst on Reaction of Propane Dehydrogenation

A spherically granular, amorphous, mesoporous catalyst was obtained by supporting V2O5 on synthesized by direct sol-gel method of ZrO2-SiO2 hydrogel and was identified by SEM, XRD and N2 adsorption / desorption. It is shown that its hydrothermal and alcohol treatment increases the specific surface, volume and width of pores and leads to an increase in the yield of propylene in the reaction of propane dehydrogenation and decreases the temperature of reaching its high values.

Increasing the propylene production in the MTP process through thermal coupling with naphtha reforming process

• Thermal coupling of naphtha reforming and methanol to propylene (MTP) process. • Using the MTP process as a heat source instead of naphtha reforming furnaces. • Enhancement in propylene production in the MTP process. • Mathematical modeling of MTP process. This paper presents the thermal coupling of the naphtha reforming process with methanol to propylene (MTP) process. In this integrated configuration, the required heat of the endothermic naphtha reforming process is provided by MTP which is an exothermic process. Therefore, intermediate heaters of conventional naphtha reforming (CNR), which were used to adjust the feed temperature of the reactors, were eliminated. The temperature of the MTP reactor increases slightly by transferring its heat to the naphtha reforming reactor; hence, the produced heat in the MTP reactor is controlled to prevent hotspot formation on catalysts. Furthermore, the MTP process is cooled inherently without extra equipment. MTP and naphtha reforming processes were considered to occur in fixed-bed reactors with axial co-current feed streams. The MTP reactor feed streams are parallel while the naphtha reforming feed streams are in series. Results show that in the MTP process, produced propylene and consumed methyl ether in the three parallel reactors are 878 kmol/h and 0.034 kmol/h, respectively. Also, the molar flow rate of aromatics in naphtha reforming is 112 kmol/h. The propylene yield in thermally coupled reactors is 10% more than the conventional one.

Highly dispersed atomic layer deposited CrOx on SiO2 catalyst with enhanced yield of propylene for CO2 –mediated oxidative dehydrogenation of propane

The increasing worldwide demand for propylene and the necessity of CO2 mitigation attracted the attention of scientists to focus on CO2-oxidative dehydrogenation of propane (CO2-ODHP). In this regard, CrOx/SiO2 catalyst is an important and conventional option. Herein, we studied the atomic layer deposition (ALD) of CrOx on silica to increase the propylene production by increasing the dispersion of the catalyst. For ALD synthesis of CrOx/SiO2 catalyst, Cr(acac)3 and synthetic air were used as metal precursor and oxidant. The catalysts were examined in the CO2-ODHP reaction and their characteristics were compared to their impregnation counterparts using UV–Vis DRS, Raman, XANES, HRTEM and STEM-EDS mapping, H2-TPR, NH3-TPD and TPO. The ALD catalysts have shown up to 2 times higher acidity and enhanced reducibility compared to the impregnation catalysts. The presence of mainly Cr(VI) with a pre-edge peak at 5.994 keV in both series of catalysts was confirmed by XANES. UV–Vis DRS and Raman spectroscopy revealed the higher contents of active polymeric Cr(VI) species in the ALD ones. The dark field HRTEM and STEM-EDS mapping represented higher dispersion of chromium oxide particles in ALD catalysts. In CO2-ODHP, the ALD catalysts showed up to 18 and 15% promotion in propane conversion and propylene yield.

Enhanced catalytic activity of phosphorus-modified SSZ-13 zeolite in the ethylene-to-propylene reaction by controlling acidity and intracrystalline diffusivity

A highly selective means of producing propylene via the ethylene-to-propylene (ETP) reaction is required to manage the supply-demand balance of light olefins. To improve the catalytic activity of the ETP reaction, a phosphorus-modified SSZ-13 zeolite (P-SSZ-13) was prepared by introducing phosphorus to the SSZ-13 zeolite via a simple impregnation method. The P-SSZ-13 catalyst exhibited increased propylene selectivity and yield compared to the pristine catalyst. According to solid-state NMR spectroscopy and STEM-EDS observation, the phosphorus species were mainly located on the outer part of the crystal as a form of polyphosphate. To reveal the effect of the phosphorus loading on the enhancement of ETP reactivity, a series of surface-modified SSZ-13 catalysts were prepared and investigated. It was found that the polyphosphate species in the P-SSZ-13 catalyst not only weakened the acidity of the zeolite by bonding with the framework aluminum species but also reduced the diffusion out of the relatively large-sized hydrocarbon species by partially blocking the pore mouths. The change in the diffusivity of the hydrocarbons over the SSZ-13 catalysts also affected the ETP reactivity. The relationship between the amount of phosphorus and the ETP reactivity of the P-SSZ-13 catalysts could also be clearly demonstrated in terms of the change in both acidity and intracrystalline diffusivity. Moreover, 13C MAS NMR measurement with isotopic switch experiment confirmed the alkyl naphthalene-based hydrocarbon pool mechanism over the P-SSZ-13 for the ETP reaction.

Low-Temperature Nonoxidative Dehydrogenation of Propane over Sn-promoted Mo-Y Zeolite: Catalytic performance and nature of the active sites

Owing to its higher value and ever-growing market, the production of light olefins is more attractive for many refineries. Among the existing routes, on-purpose dehydrogenation technologies seek special attention for the production of light olefins. Here we report a Mo-based bi-metallic catalyst exhibiting highly selective, active and stable for the direct dehydrogenation of propane to propylene. A comprehensive surface study of the MoSn/Y catalyst has been acquired to understand the interatomic interactions between metals. Extended X-ray absorption fine structure analysis suggested the Mo-O species is highly dispersed along with Sn-O. The structure-yield relationship illustrates that the Pt does not affect the catalytic performance when compared to Pt free system. We achieved a 40.94% propylene yield over MoSn/Y catalyst with the gradual coke deposition rate of 5.4x10-3 gcoke.gcat-1.h−1.

A Novel Strategy to Enhance Acid Strength of Zeolites by Incorporating Ge into Zeolite Framework

AbstractIn the long history of zeolite research, further enhancement of their acid strength has looked difficult. In this study, we achieved the enhancement by incorporating Ge into the zeolite framework. We synthesised the zeolites by a dry gel conversion method and characterised them in terms of morphology, crystal structure, and composition. We determined the acid strength of these zeolites by calculating the change in the enthalpy of desorption in the temperature‐programmed desorption of ammonia and confirmed that the acid strength of the zeolites with Ge was higher than that of a conventional zeolite. This enhancement of acid strength probably originated from the unprecedented interactions between Al and Ge, unlike the conventional interactions between Al and Si. The enhanced acid strength led to high efficiency of ethanol‐to‐propylene reactions, affording higher yield of propylene than that obtained using conventional zeolites.

One-step leap in achieving oil-to-chemicals by using a two-stage riser reactor: Molecular-level process model and multi-objective optimization strategy

With the demand for vehicle fuels (i.e., gasoline and diesel) is expected to decline soon, crude oil to chemical technology exhibits great potential to drive the next industry transition. This megatrend has led to studies on maximizing the production of low-carbon petrochemicals at the cost of fuels, which requires aggressive ways of converting oil into chemicals in a clean and efficient pattern. Herein, we proposed a novel process, termed OSCO, to crack naphtha, kerosene, diesel and heavy oil in a two-stage riser reactor efficiently, which can perform several refining procedures in the two-stage riser reactor vessel. A novel integration model of mixed fraction structure and molecular level is proposed. The multi-objective optimization strategies are also carried out to solve the optimization problem. As a result, the OSCO process can stably convert untreated heavy Daqing crude oil into light olefins with total yields of ethylene and propylene over 33 wt%, which also exhibits superior techno-economic, society, people's livelihood, and environmental performance. These insights may have a positive pushing role in engineering design, process intensification, and the optimization of direct catalytic cracking of crude oil.

The active sites and catalytic properties of CrOx/Zn-Al2O3 catalysts for propane dehydrogenation

The CrOx-based catalysts supported on Zn-modified alumina were prepared for propane dehydrogenation. The CrOx/Zn-Al2O3 catalysts possess uniform foamed pores with high specific surface area and large pore size. The zinc enriched on the surface of alumina changes the surface energy and acid sites, which decreases interaction between chromium and support so that increases the particle size of crystal Cr2O3 and changes the distribution of Cr species. The dispersion of Cr6+ species on the Zn-modified alumina is improved, and the zinc promotes the formation of more active oligomeric and polymeric chromate on the surface and highly dispersive non-redox Cr3+ species in pore channel simultaneously, which chromium species exhibit high propane conversion and propylene yield. The zinc modifier obviously inhibits the formation of coke deposition to increase catalyst stability.

Catalytic Cracking for Propylene Production over Au Catalyst Supported by External Surface-Modified ZSM-5 Zeolite

To improve the yield of propylene in fluidized catalytic cracking, a series of different Au/ZSM-5-TOS catalysts were prepared by modifying ZSM-5, using an external surface modification method and Au nanoparticles. The modified catalyst maintained the MFI structure of ZSM-5, whereas the pore-opening size of the zeolite relatively decreased, without affecting its internal structure. The acidity of ZSM-5, especially the Brønsted acidity, reduced. Among the studied catalysts, the 0.2 wt% Au/ZSM-5-1%TOS catalyst exhibited the best feedstock conversion and propylene selectivity, along with a significant increase in propylene selectivity and a slight decrease in the conversion of light diesel oil, even after water vapor treatment at 800 °C for 4 h. Its catalytic activity at 360 °C exceeded that of ZSM-5 at 460 °C, showing great application potential in petrochemical processes.

Maximizing margins and optimizing operational conditions for residue fluid catalytic cracking with an artificial intelligence hybrid reaction model

AbstractBecause of the recent declining demand for gasoline, the key to making refineries competitive is to maximize the yields of propylene and aromatics by converting heavier feedstock into basic petrochemicals through the residue fluid catalytic cracking (RFCC) process. This study presents an artificial intelligence (AI) hybrid reaction model to optimize the catalyst make‐up rate and maximize the product yield in a real‐time operation by (1) developing a catalyst activity evaluation method, (2) integrating the catalyst to oil (Cat/Oil) ratio to evaluate the reaction performance, and (3) incorporating the yield prediction model into the latest digital technologies. To this end, the catalyst deactivation function, which uses a deep neural network of the basic machine learning method, was added to the past RFCC reaction model. Under actual operational conditions, this study shows that the AI hybrid reaction model using the catalyst deactivation function can minimize catalyst loss and produce an accurate yield prediction as a production planning support tool.

Investigation of Effective Parameters Ce and Zr in the Synthesis of H-ZSM-5 and SAPO-34 on the Production of Light Olefins from Naphtha

In this paper, Ce and Zr modified commercial SAPO-34 and H-ZSM-5 catalysts were synthesized via a wet impregnation method and used as catalysts for the production of light olefins from naphtha. The synthesized catalysts were characterized using SEM, TGA, XRD, BET, and NH3-TPD. Thermal catalytic cracking of parent catalysts (SAPO-34 and H-ZSM-5) and modified catalysts with Ce and Zr on the production of light olefins from naphtha has been studied. The effects of different loading of Ce (2–8 wt.%), Zr (2–5 wt.%), and different temperatures on the yield of ethylene and propylene were also investigated. The yield of ethylene and propylene improved by 21.78 wt% and 23.8 wt%, respectively, over 2% Ce and 2% Zr on SAPO-34 catalyst. This is due to the higher acid sites on the surface of modified catalysts. It was found that H-ZSM-5 with 2% Zr loading has the highest yield of light olefins (40.4%) at 650°C in comparison with unmodified parent catalysts, while Ce loading has less effect on the olefin yield compared to Zr loading. Finally, simultaneous loading of Ce and Zr showed no effect on the light olefin yield owing to the significant decline of acid sites.

Empirical modeling of normal/cyclo-alkanes pyrolysis to produce light olefins

Due to the complexity of feedstock, it is challenging to build a general model for light olefins production. This work was intended to simulate the formation of ethylene, propene and 1,3-butadiene in alkanes pyrolysis by referring the effects of normal/cyclo-structures. First, the pyrolysis of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, cyclohexane, methylcyclohexane, n-hexane and cyclohexane mixtures, and n-heptane and methylcyclohexane mixtures were carried out at 650–800 °C, and a particular attention was paid to the measurement of ethylene, propene and 1,3-butadiene. Then, pseudo-first order kinetics was taken to characterize the pyrolysis process, and the effects of feedstock composition were studied. It was found that chain length and cyclo-alkane content can be qualitatively and quantitively represented by carbon atom number and pseudo-cyclohexane content, which made a significant difference on light olefins formation. Furthermore, the inverse proportional/quadratic function, linear function and exponential function were proposed to simulate the effects of chain length, cycloalkane content and reaction temperature on light olefins formation, respectively. Although the obtained empirical model well reproduced feedstock conversion, ethylene yield and propene yield in normal/cyclo-alkanes pyrolysis, it exhibited limitations in simulating 1,3-butadiene formation. Finally, the accuracy and flexibility of the present model was validated by predicting light olefins formation in the pyrolysis of multiple hydrocarbon mixtures. The prediction data well agreed with the experiment data for feedstock conversion, ethylene yield and propene yield, and overall characterized the changing trend of 1,3-butadiene yield along with reaction temperature, indicating that the present model could basically reflect light olefins production in the pyrolysis process even for complex feedstock.

Propylene yield from naphtha pyrolysis cracking using surface response analysis

Propylene yield from naphtha pyrolysis cracking using surface response analysis

Sensitivity Analysis and Multi‐Objective Optimization of Oxidative Dehydrogenation of Propane in a Fixed‐bed Reactor over Vanadium/Graphene for Propylene Production

AbstractOxidative dehydrogenation of light alkanes is an attractive route for the production of olefins. This method does not need much energy, while common processes such as propane dehydrogenation and cracking require external energy resources and cause rapid catalyst deactivation. In this research, an isothermal one‐dimensional model of a fixed‐bed reactor was considered for oxidative dehydrogenation of propane over a V2O5/graphene catalyst. Operational parameter sensitivity analysis showed that high temperature (450–500 °C), high pressure (7–8 atm), a moderate molar propane to air feed ratio (about 0.7), and a low feed flow rate enhanced the propane conversion and propylene productivity. However, for the production of propylene as desirable product, low temperature, low pressure, a high molar ratio, and a high feed flow rate are preferred. Thus, to determine the exact interval of operational parameter values, a multi‐objective optimization was performed for the yields of propylene and COx, revealing a maximum propylene yield of ∼40 %. For safety reasons, a feed molar ratio of propane to air of > 0.6 was preferred, which is not in the flammable region.

New approach for enhancement of light olefin production through oxidative dehydrogenation of propane over doped Mo/TiO2 nanotubes

Using promoters in different types of catalysts can positively affect the yield of oxidative dehydrogenation process and the selectivity of propylene as the main product Titania nanotubes containing distinct promoters including silver, nitrogen and cerium have been synthesized with high specific area by the hydrothermal technique and used as a support in oxidative dehydrogenation of propane. The incipient wetness impregnation method was applied for catalysts preparation Mo/Ce-TNT, Mo/Ag-TNT and Mo/N-TNT were characterized by various techniques such as XRD, TEM, SEM, EDS, BET, H2-TPR. The presence of these promoters lead to enhancement of propylene yield among which the Mo/Ce-TNT catalyst was of great efficiency. From the results, it is considered to be quite evident that the oxygen capacity of the catalyst containing Ce can contribute to the oxidation state and redox reactions. In comparison to Mo/TNT, the yield to propylene in the Mo/Ce-TNT sample increased from 9.3% to 14.8% and propylene selectivity substantially surged from 39% to 66.3%.

Effects of Mg, Ca and K addition on Pt-Sn/γ-Al2O3 for propane dehydrogenation

Abstract: In the present study, the applicability of a bimetallic Pt-Sn/Al2O3 in propane dehydrogenation with different promoters, namely, Ca, Mg, incorporation of Mg-K and Ca-K was studied. The catalysts were prepared by the sequential impregnation of γ-alumina support and characterized by TPD, SEM, XRD and UV analysis. The propane conversion and propylene selectivity were evaluated under the representative industrial conditions. The results showed that the Pt-Sn-Mg-K/γ-Al2O3 catalyst had a better performance in terms of propane conversion and propylene selectivity and yield, due to the partially neutralize and synergistic effect of Mg and K (probably by increasing the platinum dispersion and preventing side reaction and coke formation). TPD results also showed the effects of all these promoters (Ca, Mg , Ca-K and Mg-K) on reduction of acidic sites of catalyst, which are favorable sites for cracking reaction and coke formation. In the meantime, Ca is more effective on reducing strong acidic sites, but also Mg is more effective on reducing weak and medium strength acid sites. Therefore, alkaline-earth metals and also using them with potassium could reduce side reaction products and lead to more selective reaction to propylene, and improve catalyst performance compared to industrial catalyst.