Production Of Light Olefins Research Articles

Engineering crystal phases of oxides in tandem catalysts for high-efficiency production of light olefins from CO2 hydrogenation

Advances in design concept of oxide-zeolite (OX-ZEO) bifunctional tandem catalysts have demonstrated its potential for highly enhanced selectivity and yield in CO2 conversion by assigning CO2 activation and C-C coupling to specific oxide and zeolite, respectively. However, the crystalline structural effects of oxides have not been thoroughly investigated. Here, ZnO/ZrO2 with different ZrO2 crystalline phases modulated by Li doping has been used as an oxide catalyst to combine with SAPO-34 as a bifunctional composite catalyst for CO2 hydrogenation to light olefins. With the transformation of the support ZrO2 crystalline phase from tetragonal phase to mixed crystalline phase in the catalyst, the CO2 conversion and yield of target product light olefins were significantly improved. The best-performing ZnO/5Li-ZrO2 catalyst exhibited a CO2 conversion of 28.56%, light olefins selectivity of 82.00% with a yield of 8.77% along with good stability under the reaction conditions of 380 °C, 3 MPa, and 6000 mL/g/h. The characterization results by XRD, Raman, HRTEM, XPS and CO2-TPD confirmed that the highly enhanced catalytic performance was attributed to the strong interaction between the mixed crystal phase 5Li-ZrO2 and ZnO, which generated a large number of oxygen vacancies for CO2 activation. The results indicate that controlling the crystal phase of the oxide support is of prime importance in designing more active and selective oxide-zeolite bifunctional catalysts for high-efficiency CO2 to light olefins conversion.

Hydrogenation of CO2 to light olefins on ZZ/MnSAPO-34@Si-2: Effect of silicalite-2 seeds on the acidity and catalytic activity

Light olefin is a primary building block for synthesizing various chemical intermediates and products. CZZ@MnSAPO-34 and ZZ@MnSAPO-34 core–shell catalysts were prepared for hydrogenation of CO2 via Silicalite-2 seed-assisted in-situ hydrothermal synthesis method. The evaluation results showed that CZZ@MnSAPO-34 favors the generation of light alkanes, while ZZ@MnSAPO-34 benefits the production of light olefins. Further, the core–shell catalysts coating with Silicalite-2 shell denoted as ZZ@Si-2, CZZ@Si-2, and MnSAPO-34@Si-2 were synthesized by the in-situ hydrothermal synthesis technique. The microstructure, acidity, and element distribution of the above core–shell catalysts were investigated by XRD, NH3-TPD, and SEM-EDS analysis. The physically mixed ZZ/MnSAPO34@Si-2 exhibited the highest CO-free selectivity for light olefins up to 70.0%, with CO2 conversion of 17.3% at 380 °C, 2.0 MPa, GHSV = 4800 h−1. The effective synergistic interactions and weak acidity of the MnSAPO34@Si-2 zeolite favored the formation of light olefins via promoting CC coupling of methanol intermediates and inhibited the secondary hydrogenation. Meanwhile, the strong hydrogenation capacity of the CZZ elevated the selectivity to C20-C40 (82.1%) on CZZ/MnSAPO-34@Si-2 catalyst. It is found that the modulation of active metal components and inter-component synergy contributes to the regulation of product distribution.

Analysis of thermodynamic equilibrium yield and process simulation for catalytic pyrolysis of light hydrocarbons based on one set of independent reactions

The catalytic pyrolysis of light hydrocarbons has been regarded as a promising route for satisfying the growing demand for light olefins. This study established a thermodynamic equilibrium model based on one set of independent reactions in the catalytic pyrolysis process, for predicting the thermodynamic equilibrium yield and analyzing the effects of the operating conditions on the equilibrium yields. The trend of the equilibrium yields was consistent with the trend of the experimental yields. Thus, under the present operating conditions, determined by applying the thermodynamic equilibrium model, the production of light olefins was increased and the propylene/ethylene (P/E) ratio could be tailored to meet market demands. Then, an actual reaction degree model based on independent reactions was established and incorporated in Aspen Plus to simulate the catalytic pyrolysis process, and the reliability was validated experimentally. The thermodynamic equilibrium model and process simulation are easy to implement and can help to optimize the operating conditions and to predict the product yields for the catalytic pyrolysis of light hydrocarbons.

Conversion of methanol to propylene over SAPO-14: Reaction mechanism and deactivation

Methanol to olefins (MTO) reaction as an important non-oil route to produce light olefins has been industrialized, and received over 80% ethylene plus propylene selectivity. However, to achieve high single ethylene or propylene selectivity towards the fluctuated market demand is still full of challenge. Small-pore SAPO-14 molecular sieve is a rare MTO catalyst exhibiting extra-high propylene selectivity. It provides us a valuable clue for further understanding of the relationship between molecular sieve structure and MTO catalytic performance. In this work, a seconds-level sampling fixed-bed reactor was used to capture real-time product distributions, which help to achieve more selectivity data in response to very short catalytic life of SAPO-14. Changes in product distribution, especially during the low activity stage, reflect valuable information on the reaction pathway. Combined with in situ diffuse reflectance infrared Fourier-transform spectroscopy, in situ ultraviolet Raman measurements and 12C/13C isotopic switch experiments, a reaction pathway evolution from dual cycle to olefins-based cycle dominant was revealed. In addition, the deactivation behaviors of SAPO-14 were also investigated, which revealed that polymethylbenzenes have been the deactivated species in such a situation. This work provides helpful hints on the development of characteristic methanol to propylene (MTP) catalysts.

Reducing CO2 emissions of existing ethylene plants: Evaluation of different revamp strategies to reduce global CO2 emission by 100 million tonnes

Steam cracking is the leading technology to produce light olefins and the most energy-consuming process in the chemical industry, using approximately 10% of the sector's total primary energy globally. Six technological improvements, requiring limited hardware changes and implementable today, have been evaluated: high emissivity coatings, 3D reactor designs, advanced coil material, oxy-fuel combustion, carbon capture and storage (CCS), and biogas firing. These technologies have the potential to reduce both energy consumption and raw material demand. Life cycle inventory data are obtained from the first principles-based COILSIM1D model of the furnaces, validated with industrial data, combined with a Petro-SIM model of the overall mass and energy balance of the plant. Cradle-to-gate life cycle assessment (LCA) shows that a major contribution to the overall carbon footprint of light figureolefin production is related to the feedstock supply. Oxy-fuel combustion combined with CCS followed by biofuel combustion has the highest potential to reduce the carbon footprint, and reach a target of over 100 × 106 metric tons/yr of CO2 eq. worldwide. On the other hand a combination of radiant coatings and novel reactor coil design yields in a marginal 0.5% reduction or potentially 3 × 106 metric tons/yr of CO2 eq. worldwide. In order to decrease the carbon footprint more one would have to consider both substantial hardware changes - requiring a large investment - and the use of non-fossil derived feedstocks.

Wheat straw/HDPE co-reaction synergy and enriched production of aromatics and light olefins via catalytic co-pyrolysis over Mn, Ni, and Zn metal modified HZSM-5

The co-reaction synergy of wheat straw (WS) and high-density polyethylene (HDPE) plastic waste with varying mass ratios were evaluated at 550 °C in a fixed bed pyrolyzer reactor. Ex-situ catalytic co-pyrolysis of WS and HDPE feed mix (3:1) at a high feed to catalyst ratio (10:1) was performed over Mn, Ni, and Zn (1, 5, and 10 wt%) metal-modified HZSM-5 at 550 °C to study the effect of metal promotors variations on the production of aromatics and light olefins. The prepared catalysts were characterized by employing XRD, N2 physisorption, NH3-TPD, H2-TPR, and UV-Vis analytical techniques. The results obtained in the present work indicated that 1%-Zn modified HZSM-5 produced a more relative proportion of aromatics (25.12%) in the co-pyrolysis oil organic phase, followed by 5% Ni and 5%-Zn-loaded HZSM-5 at 16.22% and 15.76% respectively. Furthermore, 5% Ni-HZSM-5 has shown higher deoxygenation ability (58.43%) in reducing the oxygenates formed, followed by 5% Mn (40.96%) and 1% Zn (35.37%) respectively. While, 5% Mn-HZSM-5 generated pyrolytic gases with higher volumetric compositions of (C2-C4) light olefins at 15.84%, followed by 1% Mn (13.97%) and 10% Ni (13.61%) respectively and these volumetric yields were strongly correlated with intermediate acidity of catalysts. The physical properties (e.g. HHV ~ 41–43 MJ/kg) of the resultant organic fraction of catalytic co-pyrolysis bio-oil are almost analogous to conventional fuels such as diesel and light fuel oil (LFO). Additionally, the resultant catalytic pyrolytic gases possessed excellent calorific value (LHV ~ 30–31 MJ/Nm3) and are comparable to natural gas. Overall, the present study has successfully demonstrated the promising nature of the catalytic co-pyrolysis process for the conversion of biomass and waste plastic into useful chemicals and fuels.

Catalytic fast pyrolysis of cellulose over different metal-modified ZSM-5 zeolites for light olefins

Light olefins (C2H4, C3H6 and C4H8) are important chemical building blocks in modern energy and material system. In this study, the effects of different metal-modified ZSM-5 catalysts on the production of light olefins from cellulose fast pyrolysis were investigated in a fixed bed. Fe, La, Cu, Mg, Al and Ce modified ZSM-5 were prepared by the impregnation method, and then the derived modified ZSM-5 catalysts were characterized by different analytical instruments. The correlation between catalyst characteristics and the production of light olefins was explored. The results showed that the specific MFI-type structure of ZSM-5 remained intact after modification, and the surface area, pore volume and the amount of acid sites of catalysts varied. The highest light olefins yield was obtained over Cu-ZSM-5 (7.64 C-mol%), while the lowest was achieved over Mg-ZSM-5 (3.75 C-mol%). Moreover, the formation of light olefins can be promoted with the increasing of ZSM-5 other-pore volume and surface area, medium and strong acidity, and the decreasing of micro-pore volume and surface area, weak acidity. The results may share some light on the design of high efficiency ZSM-5 catalyst for high light olefins production.

Production of light olefins by catalytic hydrogenation of CO2 over Y2O3/Fe-Co modified with SAPO-34

Direct conversion of CO2 to hydrocarbons by hydrogenation was used in the production of light olefins. Hydrothermal coating and physical blending procedures were used to synthesize Y2O3/Fe-Co-SAPO-34 in this study. Based on the results from characterization, a unique micro-mesoporous structural composite with co-existing basic and acidic sites was obtained without any excessive close-fitting between the active sites in the physically blended composite. The catalyst’s overall selectivity for the light olefins was 82.6% with CO2 conversion of 19.9% for H2/CO2 of 3.0, with space velocity of 10 L.g.cat −1 h−1 at 400 °C and 20 bars. Furthermore, an increase in the number of acidic-basic sites, meso-microporous structures, alongside the synergetic effects of the compositephases over the catalyst without any support, improved the catalyst’s activity for CO2 conversion which in turn yielded higher C2=–C4= selectivity. The hybrid catalyst had a commendable stability within 80-hours of operation without losing its activity

Low-temperature selective production of propylene from non-oxidative dehydrogenation of propane over unconventional Zr/ZK-5 catalysts

The supply-side abundance of inexpensive propane and ethane from shale gas and stranded gas are drivers for technologies for the on-demand production of light olefins, propylene and ethylene. However, existing catalysts exhibit relatively poor stability and deactivate rapidly at the high temperature required for dehydrogenation. This indicates an opportunity for new catalyst systems which can activate propane at a relatively lower temperature. Small pore zeolites, ZK-5 with improved acidity, notably monodispersed zirconia ZK-5 catalyst, are explored for low-temperature dehydrogenation of propane to propylene. Zeolite supports help to stabilise the metal particles and improve metal-support synergy. This paper demonstrates a Pt-free metal impregnated zeolite catalyst for propane dehydrogenation while maintaining good stability and activity. The Zr/ZK-5 catalyst exhibits 40.3% conversion with 45.2% propylene selectivity at 500 °C for 24 h. The combination of Zr and ZK-5 effectively activates the CH bond, inhibits side reactions, reduces coke formation, and improves selectivity as well as stability.

ZSM-5 Catalysts for MTO: Effect and Optimization of the Tetrapropylammonium Hydroxide Concentration on Synthesis and Performance

Light olefin production from methanol using various zeolite catalysts has industrial and economic importance considering the growth of the petrochemical market. Zeolites are generally synthesized using various organic templates as structure-directing agents (SDAs). In this study, synthesis of a series of ZSM-5 zeolites was performed systematically using the microwave-assisted crystallization method, and these samples were analyzed in detail to understand the effect of the SDA concentration. Powder diffraction, N2 adsorption, scanning electron microscopy, ammonia adsorption desorption, and 27Al and 29Si NMR spectroscopies were used for the characterization. The organic SDA tetrapropyl ammonium hydroxide (TPAOH/SiO2 mole ratio = 0.0500) is found to have an optimum concentration against the silica precursor for achieving the highest crystallinity, suitable morphology, ideal pore size, effective pore volume, and tuned microporous/mesoporous area. For samples with a template concentration ratio of 0.050 or higher, 29Si and 27Al NMR data revealed the presence of an intact ZSM-5 structure. Using a fixed bed reactor at 500 °C and atmospheric pressure, the catalytic performance of the selected catalysts from the series is investigated for the methanol-to-olefin conversion reaction. The sample with the highest crystallinity showed the best conversion, selectivity toward light olefins, and time on stream stability. It is also worth noting that the highest crystallinity, micropore area, and micropore volume are reached for the optimum value rather than the highest template concentration. This allows for a reduction in the template concentration and a move closer to a synthesis pathway benign to environment and economics.

A strategy combining the catalytic cracking of C6-C8 olefins and methanol to olefins (MTO) reaction through SAPO-34 pre-coking

The coupling conversion of C6-C8 olefins and methanol over SAPO-34 is proposed for enhancing carbon resource utilization and light olefins production. With the aid of thermogravimetric analysis (TGA), dissolution-extraction experiment and molecular dynamics simulations, the relationship between reactive “coke” and reaction pathway of methanol-to-olefin (MTO) are studied. Owing to its remarkable product shape selectivity, octene is explored to be an effective coking source for promoting ethene production.

Using Biomass Gasification Mineral Residue as Catalyst to Produce Light Olefins from CO, CO2 , and H2 Mixtures.

Invited for this month's cover is the group of Bert Weckhuysen at Utrecht University. The image shows how iron nanoparticles in a biomass gasification residue can convert CO, CO2 , and H2 mixtures into light olefins. The Research Article itself is available at 10.1002/cssc.202200436.

Using Biomass Gasification Mineral Residue as Catalyst to Produce Light Olefins from CO, CO 2 , and H 2 Mixtures

The Front Cover shows a coarse solid residue particle, originating from the gasification of biomass, which acts as a solid catalyst to produce high-value chemicals, such as olefins, from mixtures of H2, CO, and CO2. The heart of the developed catalyst material are nanoparticles, consisting of iron carbides and iron metal, together with some alkali elements, such as sodium and potassium. The latter elements act as promotors to boost the production of light olefins. This approach represents an elegant example illustrating how we can apply the concept of materials circularity, in which a waste material is transformed into a functional catalyst material. More information can be found in the Research Article by I. C. ten Have et al.

Optimization of carbon nanotube growth via response surface methodology for Fischer-Tropsch synthesis over Fe/CNT catalyst

Light olefins such as ethylene, propylene, and butylene are key compounds in the chemical industry. Iron catalyst supported on carbon nanotubes (CNTs) is an appropriate candidate for light olefins production using synthesis gas in Fischer-Tropsch synthesis (FTS). First, catalytic chemical vapor deposition (CCVD) method was applied to synthesize CNTs using Fe/CaCO3 and acetylene as catalyst and hydrocarbon source, respectively. Applying response surface methodology, the optimum operating conditions were determined in CVD reactor for maximal yield and purity of CNTs. The effects of reaction time (30–60 min), reaction temperature (700–800 °C), and loading of the catalyst (10–30 wt% Fe) were investigated. The synthesized CNTs was characterized by Raman spectroscopy for its graphitic structure and purity. After acid-treatment of the synthesized CNTs, Fe/CNTs-synthesized catalyst was successfully fabricated by ultrasonic-assisted wet impregnation method. 20Fe/CNTs-synthesized, 20Fe/CNTs-commercial, and 20Fe/Al2O3 were analyzed in terms of physio-chemical properties and FTS catalytic performance. Comparison of transmission electron microscopy (TEM) and CO-chemisorption results showed that 20Fe/CNTs-synthesized reduces iron oxide agglomeration resulting in metal particles well-dispersed among the studied Fe-based catalysts. The catalytic performance of Fe-based catalysts was investigated using a fixed-bed reactor at 280 °C under 290 psi. 20Fe/CNTs-synthesized exhibited a lower rate of water-gas-shift (WGS) reaction compared with 20Fe/CNTs-commercial, with C2-C4 selectivity of 23.6% which is slightly less than that of its commercial counterpart. Analysis of FTS liquid products revealed that 20Fe/CNTs-synthesized provides liquid hydrocarbons in the range of C8-C18, while 20Fe/CNTs-commercial and 20Fe/Al2O3 obtained C9-C52 and C10-C20, respectively. After 120 h time on stream under steady state condition, higher activity had been maintained by the 20Fe/CNTs-synthesized catalyst compared to the 20Fe/CNTs-Commercial and 20Fe/Al2O3 catalysts.

Fabrication of extra–framework Al in ZSM–5 to enhance light olefins production in catalytic cracking of n–pentane

ZSM–5 zeolite catalysts are widely used for catalytic cracking of hydrocarbons to produce light olefins. In this study, secondary addition of Al was introduced in aluminum–silicon zeolites (ZSM–5) by impregnation to modify their acid properties. Characterizations revealed that extra–framework Al (EFAL) formed after calcinations both on the internal and external surface of the catalysts, which provided certain Lewis acid sites. Interestingly, the amount of strong Brønsted acid increased significantly in catalysts with the introduction of EFAL. In cracking of n-pentane, the modified ZSM-5 zeolites gave obviously enhanced TOF values based on Brønsted acid sites, and a significantly improved n-pentane conversion was realized than the pristine catalyst. Moreover, the isolated strong Brønsted acid sites with certain spatial barriers triggered the cracking reaction happening through monomolecular route, which inhibited the hydride transfer of light olefins. The optimized ZSM–5 with Si/Al ratio of 50 (Z–50(75)) gave 45.2 wt% yield of light olefins at 600 °C with an excellent catalytic stability.

Sr1-xKxFeO3 Perovskite Catalysts with Enhanced RWGS Reactivity for CO2 Hydrogenation to Light Olefins

The catalytic hydrogenation of CO2 to light olefins (C2–C4) is among the most practical approaches to CO2 utilization as an essential industrial feedstock. To achieve a highly dispersed active site and enhance the reactivity of the reverse water–gas shift (RWGS) reaction, ABO3-type perovskite catalysts Sr1-xKxFeO3 with favorable thermal stability and redox activity are reported in this work. The role of K-substitution in the structure–performance relationship of the catalysts was investigated. It indicated that K-substitution expedited the oxygen-releasing process of the SrFeO3 and facilitated the synchronous formation of active-phase Fe3O4 for the reverse water–gas shift (RWGS) reaction and Fe5C2 for the Fischer–Tropsch synthesis (FTS). At the optimal substitution amount, the conversion of CO2 and the selectivity of light olefins achieved 30.82% and 29.61%, respectively. Moreover, the selectivity of CO was up to 45.57% even when H2/CO2=4 due to CO2-splitting reactions over the reduced Sr2Fe2O5. In addition, the reversibility of perovskite catalysts ensured the high dispersion of the active-phase Fe3O4 and Fe5C2 in the SrCO3 phase. As the rate-determining step of the CO2 hydrogenation reaction to light olefins over Sr1-xKxFeO3 perovskite catalysts, FTS should be further tailored by partial substitution of the B site. In sum, the perovskite-derived catalyst investigated in this work provided a new idea for the rational design of a catalyst for CO2 hydrogenation to produce light olefins.

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.

Effect of Transition Metal Nickel on the Selectivity of Light Olefins in n-Hexane Cracking of Ni/IM-5 Zeolite

The production of light olefins by catalytic cracking is a research hotspot in the petrochemical industry. Herein, nickel was used to modify IM-5 zeolite to improve the performance in catalytic cracking. Properties of the Ni/IM-5 zeolites with different nickel loadings were characterized. It was demonstrated that nickel species were mainly located on the external surface of impregnated IM-5 zeolite, only a few Ni2+ ions were distributed in the ion exchange site as compensation cations. Pyridine infrared results indicated that the introduction of nickel could modulate the acidity of IM-5 zeolite and increase the amount of Lewis acid sites. Compared with IM-5, Ni/IM-5 exhibited higher olefin selectivity, especially ethylene, in n-hexane cracking reactions. It was considered that nickel could provide dehydrogenation active sites and promote the formation of light olefins. Thus, the selectivity of light olefins can be improved by controlling the amount and distribution of nickel in IM-5 zeolite.

Effect of chromium and boron incorporation methods on structural and catalytic properties of hierarchical ZSM-5 in the methanol-to-propylene process

We introduced chromium and boron into the hierarchical structure of ZSM-5 by following an incipient wet impregnation and hydrothermal synthesis approach to enhance the performance of the catalysts in the methanol-to-propylene process. Crystal structure, preferred orientation, and crystal symmetry of synthesized zeolites were discussed using Rietveld refinement and revealed that all synthesized zeolites crystallized in a monoclinic structure, whereas the boron-incorporated sample exhibited an orthorhombic symmetry. Large-scale defect-free single-crystalline structures of hierarchical zeolite created by CTAB and F127 mesoporogens are confirmed by electron microscopy and magic angle spinning nuclear magnetic resonance (MAS NMR). The formation of surface metal oxides and extra-framework metal oxides caused changes in the electronic structure of the components as visible in Si 2p and O 1s spectra. The predominant presence of OH groups and the higher Cr (VI) /Cr (III) ratio account for the better performance of impregnated chromium-ZSM-5 especially in the production of light olefins. The introduction of boron by impregnation further preserved the preferred growth orientation, hierarchical structure with high crystallinity and caused surface acidity changes in favor of increasing propylene selectivity to 67% with a propylene/ethylene ratio of close to 8.

Exergetic, exergoeconomic, and exergoenvironmental analyses of an existing industrial olefin plant

Light olefins production via thermal cracking of hydrocarbons is a process with the highest value of energy consumption in the petrochemical industry. Therefore, the study of the process from three points of view, i.e., thermodynamic, economic, and environmental, is of interest. In the previous exergy-based analyses of the olefin process, analysis of the steam system along with the other sections is ignored. In this work, for the first time, exergetic, exergoeconomic, and exergoenvironmental analyses of an existing industrial olefin plant with ethane feedstock, at both design and working conditions, are performed. The environmental impacts are calculated through Life Cycle Assessment (LCA). The formation of cost and environmental impact in the plant are indicated through Sankey diagrams. The results indicated that the cracking section (66%), steam system (14%), and ethylene purification section (8%), respectively, are the main contributors to the total exergy destruction. It was illustrated through exergoeconomic analysis that the monetary cost of a product can be very lower/higher than its real exergy-based value. The optimization of the process aiming at the minimum specific total cost rate, the minimum specific total environmental impact rate, or a combination of them per unit of mass of useful products is suggested.