Methanol To Propylene Research Articles

Study on the synthesis of nanosheets petal-shaped ZSM-5 Zeolites

In this work, a novel strategy for hydrothermal synthesis of nanosheets petal-shaped ZSM-5 zeolites was introduced. The experimental results indicated that the nanosheets petal-shaped ZSM-5 zeolites exhibited a higher specific surface area and more abundant acid sites. Under the synergistic crystallization effect of ethanol and seeds, the addition of CTAB promoted the growth of the layered structure, and the introduction of trace amounts of seeds effectively inhibited the growth of mordenite in a high alkalinity environment, reducing the crystallization time to 48 hours. More importantly, the petal-shaped ZSM-5 zeolites exhibited excellent MTP (Methanol-to-Propylene) catalytic performance, with methanol conversion maintained above 97.8 % for 80 hours and a maximum propylene selectivity of 49.1 %. This paper proposes an Ethanol-Seed-CTAB synthesis method for producing petal-shaped ZSM-5 zeolite with a unique morphology. This approach does not require the use of complex gemini quaternary ammonium surfactants in the synthesis process, greatly promoting the application and dissemination of nanosheets zeolites.

Comparative study of the catalytic performance of physically mixed and sequentially utilized γ-alumina and zeolite in methanol-to-propylene reactions.

This study aimed to investigate the catalytic performance of H-ZSM-5 zeolite compared with physically mixed and sequentially used synthesized γ-alumina and zeolite in the methanol-to-propylene (MTP) reaction. A facile, green and cost-effective method was first applied to prepare a mesoporous γ-Al2O3 support using a combination of sol-gel and hydrothermal methods via a few consecutive steps. This process was carried out using aluminium nitrate and polyethylene glycol with different molecular weights as non-ionic surfactants. X-ray diffraction, transmission electon microscopy, thermogravimetric analysis, ammonia temperature programmed desorption and Brunauer-Emmett-Teller analysis were then used to characterize the prepared γ-Al2O3 catalyst. Afterwards, the catalytic activity of the commercial H-ZSM-5 zeolite (Si/Al = 200) and the effect of the presence of the γ-alumina physically mixed and unmixed with the zeolite were also researched in the MTP reaction. Accordingly, methanol conversion and product selectivity were monitored via gas chromatography. The physically mixed mesoporous γ-Al2O3 and H-ZSM-5 zeolite exhibited the highest catalytic activity in terms of both conversion and selectivity at 400°C. To our knowledge, this research represents the first documented use of γ-alumina and zeolite simultaneously as catalysts in the MTP reaction within the English literature. It is hoped that this work will offer valuable insights for advancing the development of catalytic systems in methanol conversion processes.

Disassembly-reassembly-phosphating strategy to fabricate hydrothermally-stable hierarchical P@ZSM-5 zeolite for efficient methanol-to-propylene

Available hierarchization and phosphorization of ZSM-5 zeolite as one of methanol-to-propylene (MTP) catalysts have improved reactive stability and propylene selectivity, but are subjected to the problems of poor phosphorus stabilization efficiency and inhomogeneous dispersion. Herein, we fabricate a series of hierarchical P@ZSM-5 zeolites via one-step disassembly-reassembly-phosphating strategy of ZSM-5 zeolite using successfully self-created asymmetric quaternary phosphonium hydroxides and elucidate the mechanism of mesoporous formation and the interaction of phosphorus with framework aluminum. Delightfully, reconstructively tetracoordinated PIV-O-AlIV structure endows excellent hydrothermal and Brønsted acid stability of hierarchical P@ZSM-5 zeolites. The MTP tests show that the P@ZSM-5(TBuCP) catalyst prepared by disassembly-reassembly-phosphating of tributylhexadecylphosphine hydroxide (TBuCPOH) exhibits superior propylene selectivity (48.9 %) and remarkedly long lifetime (32.5 h, WHSV=6h−1). Such enviable MTP performance is benefited from the join hands of the zeolitic hierarchization and suitable Brønsted acid strength conferred by its phosphorus-aluminum interaction that are conducive to olefinic cycle process. These findings afford value-filled opportunities in novel MTP catalysts with high reactive stability and propylene selectivity, and the understandings for phosphorus-zeolite chemistry.

γ-aminobutyric acid-assisted fabrication of plate-like ZSM-5 zeolite for efficient propylene production from methanol conversion

Plate-like ZSM-5 zeolites offering a short diffusion pathway along the b-axis are highly desirable catalyst for methanol to propylene (MTP) reaction. Herein, we successfully developed a simple synthetic strategy toward reducing the thickness along b-axis of ZSM-5 zeolite by combing a preliminary aging process and the addition of γ-aminobutyric acid. In particular, γ-aminobutyric acid adopted as a zeolite growth modifier was firstly proposed to prepare plate-like ZSM-5 zeolite with a short thickness of b-axis, and the minimum thickness can reach ∼50 nm. The shortened diffusion length in plate-like ZSM-5 zeolites could significantly improve the transport efficiency of molecules to and away from the active sites and finally leads to a better catalytic performance in the MTP reaction. Particularly, the plate-like ZSM-5 zeolite with an impressively shortened diffusion length (P-ZSM-5–0.3#0.3) displayed greatly improved catalytic performances (higher propylene selectivity and longer lifetime) than conventional ZSM-5 with a thicker dimension along the b-axis.

Synthesis of hierarchical ZSM-11 and its catalytic performances during methanol to propylene

To solve the easy deactivation of zeolite catalyst in methanol to propylene (MTP) reaction, hierarchical ZSM-11 zeolite composed of loosely aggregating ultra-small nanocrystals (∼10 nm) were prepared using vinyltrimethoxysilane-methyl methacrylate (VTMS-MMA) copolymer latex as a “bond blocker”. The structure and texture properties of the as-synthesized zeolite were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption desorption, NH3-TPD, and thermogravimetric analysis (TG). The results showed that as compared with the parent ZSM-11-0 without adding the latex, the hierarchically porous ZSM-11-x (1 ≤ x ≤ 3) zeolite synthesized with VTMS-MMA copolymer latex had a higher surface area, mesopore volume, and moderate acidity. Due to the nanocrystallization of the primary grain in the polycrystalline aggregates, the micropores channels in the as-synthesized ZSM-11-x (1 ≤ x ≤ 3) were effectively shortened and abundant intercrystalline mesopores resulted from loosely aggregating of the ultrasmall primary crystals were therefore introduced, which offered the optimized ZSM-11-1 catalysts with a longer catalyst life (46 h) and a higher propylene yield (∼40.5 %) in MTP.

Controlling the morphologies and crystal growth orientations of H-ZSM-5: their impact on the structure-diffusion-performance relationship in the methanol-to-propylene reaction

The superior performance of the nano-sheet ZSM-5 was attributed to its higher distribution ratio of framework Al in the straight and sinusoidal channel, faster higher diffusion rate along the b axis orientation, and fewer framework defects.

Preparation of H-[B]- ZSM -5 zeolites by hydrothermal method as a highly stable and selective catalyst for methanol to propylene (MTP) conversion

A series of high-silica boron-containing H-ZSM-5 zeolites were prepared employing the hydrothermal method. Subsequently, the physico-chemical characteristics of prepared catalysts were comprehensively studied through diverse analytical methods, followed by evaluation of catalytic performance in the methanol-to-propylene (MTP) reaction. The results demonstrated that incorporation of boron into the H-ZSM-5 zeolite induced the reduction in the total surface area and pore volume, accompanied by a raise in the density of weak acid sites. Also, the optimal point for boron content has been recognized at molar coefficient of B2O3/SiO2 = 0.025 for obtaining the highest H-[B]-ZSM-5 performance in MTP process. In comparison to unmodified H-ZSM-5, the optimized H-[B]-ZSM-5 yielded the higher selectivity towards propylene (42.9 % versus 40.1 %) and total light olefins (72.1 % versus 69.5 %), as well as propylene to ethylene ratio (8.1 versus 7.8) with a considerable reduction in selectivity toward C1–C4 alkanes (3.9 % versus 4.2 %) and heavy hydrocarbons (24.1 % versus 26.4 %). Also, the optimized H-[B]-ZSM-5 catalyst exhibited an extended lifetime of 988 h in the MTP process, surpassing the lifetime of unmodified H-ZSM-5 (936 h). These results suggest the optimal point for boron content at B2O3/SiO2 = 0.025 to attain the superior catalytic performance, specifically in terms of propylene yield and catalyst lifetime during MTP process.

Promoting Syngas to Olefins with Isolated Internal Silanols-Enriched Al-IDM-1 Aluminosilicate Nanosheets.

Selective conversion of syngas to value-added olefins has attracted considerable research interest. Regulating product distribution remains challenging, such as achieving higher olefin selectivity, propylene/ethylene (P/E) and olefin/paraffin (O/P) ratios. A new pentasil zeolite Al-IDM-1 with recently approved -ION structure, composed of 17-membered-ring (MR) extra-large lobed pores and intersected 10-MR medium pores, shows a C2-6 = selectivity up to 85 % and a high O/P value of 14 in the conversion of syngas when being combined with Zna Alb Ox oxide. Moreover, for the high-silica Al-IDM-1 with Si/Al ratio of 400, the selectivity of propylene and butene accounts for 88 % in C2-4 = , resulting in high P/E (>4) and butene/ethylene (B/E >3) ratios. The high C3-4 = selectivity is contributed by two main reasons, that is, the relatively weak acidity of Al-IDM-1 zeolite enhances the olefin-based cycle revealed by the probe reactions of methanol-to-propylene (MTP) and 1-hexene cracking, and the rich isolated internal SiOH groups in Al-IDM-1 promote the desorption of C3-4 = , once they are formed inside zeolite pores.

Promoting Syngas to Olefins with Isolated Internal Silanols‐Enriched Al‐IDM‐1 Aluminosilicate Nanosheets

AbstractSelective conversion of syngas to value‐added olefins has attracted considerable research interest. Regulating product distribution remains challenging, such as achieving higher olefin selectivity, propylene/ethylene (P/E) and olefin/paraffin (O/P) ratios. A new pentasil zeolite Al‐IDM‐1 with recently approved −ION structure, composed of 17‐membered‐ring (MR) extra‐large lobed pores and intersected 10‐MR medium pores, shows a C2–6= selectivity up to 85 % and a high O/P value of 14 in the conversion of syngas when being combined with ZnaAlbOx oxide. Moreover, for the high‐silica Al‐IDM‐1 with Si/Al ratio of 400, the selectivity of propylene and butene accounts for 88 % in C2–4=, resulting in high P/E (>4) and butene/ethylene (B/E >3) ratios. The high C3–4= selectivity is contributed by two main reasons, that is, the relatively weak acidity of Al‐IDM‐1 zeolite enhances the olefin‐based cycle revealed by the probe reactions of methanol‐to‐propylene (MTP) and 1‐hexene cracking, and the rich isolated internal SiOH groups in Al‐IDM‐1 promote the desorption of C3–4=, once they are formed inside zeolite pores.

Plantwide Simulation and Operation of a Methanol to Propylene (MTP) Process

BackgroundMethanol to propylene (MTP) process is considered as one of the most important methods for propylene production. The MTP process consists of four sections: conversion of reactants to products, cooling, compression and products separation. In this process, is utilized from multi-stage fixed bed reactors. Due to high exothermicity of the MTP reactors, and existence of recycle loops, a plant-wide control structure is required to be designed for stable, safe and maximum production of propylene. MethodModeling and simulation of the heterogeneous fixed bed MTP reactors with interphase and intra-particle mass and heat transfer were carried out in Aspen Custom Modeler. Steady-state simulations of the MTP process were carried out in Aspen Plus. A simple control strategy was proposed to achieve maximum propylene production with temperature control of the MTP multi-stage reactors by splitting the cold oxygenate feed and the recycled hydrocarbons among the reactor beds. The performance of the proposed control strategy was tested against several disturbances including change in flowrate and composition of feed, using dynamic simulations by Aspen Plus Dynamics. Significant findingDynamic simulation results revealed that simultaneous control of the split range for the 5th and 6th reactor beds and cascade temperature of other reactor beds, could be a suitable temperature control strategy for the reaction section of the MTP process.

Seed-assisted H-[B]-ZSM-5 borosilicate: Investigating the effect of promoter level on catalytic production of propylene from methanol

Boron was implemented to promote the catalytic behavior of H-ZSM-5 zeolite in methanol to propylene (MTP) process. A series of crystalline borosilicates with different boron contents were synthesized using a seed-assisted hydrothermal technique and characterized well. Results revealed that increasing the boron coefficient improved lifetime and propylene productivity of zeolite by 20 and 24%, respectively. Hierarchal micro-mesoporosity and the distribution of acid sites made a substantial contribution to H-[B]-ZSM-5 performance in MTP. Boron played a significant role in tuning the acidity of the catalyst and improved its stability by controlling the formation of heavy hydrocarbons (C5+) in the MTP reaction.

Modified seed-induced synthesis of ZSM-5 aggregates and their catalytic performance in methanol to propylene conversion: Co-effect of ball milling and alkaline treatment of seed

Industrial ZSM-5 catalysts suffer from coke deposition and loss of activity in methanol to propylene conversion. Developing zeolites with a better diffusion path, which is essential for the design of high-efficiency catalysts, is still a challenge to be achieved. The synthesis of seed-induced ZSM-5 zeolite with a short diffusion path could be a solution to reduce coke accommodation and have a higher catalytic lifetime. However, it would not be beneficial with current methods as far as the industrial aspect. Herein, we have proposed a successful and industrially-feasible approach for decreasing the costs of seed-induced ZSM-5 synthesis as well as improving the lifetime and catalytic performance of ZSM-5 zeolites in the methanol to propylene (MTP) reaction. This modified seeding route includes a physical factor (ball milling) and a chemical factor (alkaline treatment). Compared to a conventional seed-induced route, this new technique allowed us to increase catalyst lifetime (from 159 h to 265 h), propylene/ethylene selectivity (from 5.23 to 8.19), and amount of produced propylene per gram of catalyst (from 182 gC3H6/gcat to 443 gC3H6/gcat). This modified seed has a high potential for use on an industrial scale, based on the results.

Design of an Organic Template for Synthesizing ITR Zeolites under Ge-Free Conditions.

Germanosilicate zeolites with various structures have been extensively synthesized, but the syntheses of corresponding zeolite structures in the absence of germanium species remain a challenge. One such example is an ITR zeolite structure, which is a twin of the ITH zeolite structure. Through the modification of a classic organic template for synthesizing ITH zeolites and thus designing a new organic template with high compatibility to ITR zeolite assisted by theoretical simulation, we, for the first time, show the Ge-free synthesis of an ITR structure including pure silica, aluminosilicate, and borosilicate ITR zeolites. These materials have high crystallinity, corresponding to an ITR content of more than 95%. In the methanol-to-propylene (MTP) reaction, the obtained aluminosilicate ITR zeolite exhibits excellent propylene selectivity and a long lifetime compared with conventional aluminosilicate ZSM-5 zeolite. The strategy for the design of organic templates might offer a new opportunity for rational syntheses of novel zeolites and, thus, the development of highly efficient zeolite catalysts in the future.

A Nanostrips-Assemble Morphology of ZSM-5 Zeolite for Efficient Propylene Production from Methanol Conversion

Turning the morphology and orientated growth of zeolite crystals is essential to alter their catalytic performances. MFI-type ZSM-5 nanostripes (named as D-Z5) with a sea-urchin-like overall morphology were directly synthesized with a commercially available and small-molecular organic structure-directing agent (OSDA) of 1-butyl-1-methylpyrrolidinium hydroxide. Their nanostrip crystals exhibited a unique dioriented morphology with thin thicknesses of ∼8 nm and ∼70 nm along the a-axis and b-axis, respectively. The dealuminated D-Z5 displayed higher propylene selectivity (∼57%), longer lifetime (60 h) and much higher propylene-to-ethylene ratio (>12) in methanol-to-propylene (MTP) reaction than those conventional ZSM-5 with known crystal morphologies. Computational simulation and experimental measurements provided solid proof that the diorientated crystals decreased the bulky molecular diffusion resistance, postponed the secondary reaction and then promoted propylene to diffuse rapidly out of two sets of micropores in zeolites. This unusual diorientation phenomenon is not only beneficial for improving the MTP catalytic performance of ZSM-5, but also expected to be versatile to develop other useful zeolite catalysts.

Realizing of ZSM-5 microspheres with enhanced catalytic properties prepared from iron ore tailings via solid-phase conversion method.

The comprehensive utilization of iron ore tailings (IOTs) not only resolved environmental problems but also brought huge economic benefits. In this study, the synthetic route presented herein provides a novel method for the synthesis of ZSM-5 microspheres from IOTs. The effects of Si/Al molar ratios and the pH of the precursor solution on the formation of zeolite was evaluated by various analytical methods. The catalytic performance of the catalyst prepared by the solid-phase conversion method (denoted as MP-ZSM-5) was evaluated by methanol-to-propylene (MTP) reaction. Compared with the zeolite catalyst that synthesized via the conventional hydrothermal method (denoted as HM-ZSM-5), MP-ZSM-5 not only prolongs catalytic lifetime from 18.7 to 36.0h but also has higher selectivity for propylene by MP-ZSM-5 (43.7%) than that for HM-ZSM-5 (38.6%). In addition, Kissinger-Akahira-Sunose (KAS) model is applied to the TG result to study the template removal process kinetics. The average activation energy values required for the removal of CTAB and TPABr are 201.11 ± 13.42 and 326.88 ± 16.91kJ∙mol-1, respectively. Furthermore, this result is well coupled with the model-free kinetic algorithms to determine the conversion and isoconversion of the TPABr and CTAB decomposition in ZSM-5, which serves as important guidelines for the industrial production process.

Directing Highly a-Axis-Oriented ZSM-5 Nanosheets with Pre-estimated Bifunctional Imidazole Cations.

An MFI-topology nanosheet zeolite with a highly a-axis-oriented structure has rarely been reported but with a great potential for industrial applications. Theoretical calculations on the interaction energies between the MFI skeleton and ionic liquid molecules indicated the possibility of preferential crystal growth along a specific direction, according to which highly a-oriented ZSM-5 nanosheets were synthesized from commercially available 1-(2-hydroxyethyl)-3-methylimidazolium and layered silicate sources. The imidazolium molecules directed the structure formation and meanwhile acted as zeolite growth modifiers to restrict the crystal growth perpendicular to the MFI bc plane, which induced unique a-axis-orientated thin sheets with ∼12 nm thickness. The a-oriented ZSM-5 exhibited more competitive propylene selectivity and longer lifetime than bulky crystals in methanol-to-propylene (MTP) reaction. This research would provide a versatile protocol for the rational design and synthesis of shape-selective zeolite catalysts with promising applications.

Experimental study and kinetic modeling of methanol conversion to propylene with co-feeding of C4 and C5/C6 hydrocarbon cuts over a ZSM-5 catalyst.

Extensive experimental data were used to develop a comprehensive kinetic model for the methanol to propylene (MTP) process over a ZSM-5 catalyst. Preliminary experiments were performed to determine the reaction conditions that would ensure the absence of external (film) and internal mass transfer resistances. The kinetic experiments were subsequently carried out at 420-500 °C under conditions where mass transfer limitations were absent. A detailed reaction network was proposed for the MTP process based on the experimental product distribution and various reported kinetic models in the literature. According to the first series of experiments (without C4 and C5/C6 recycle streams) conducted at various temperatures, the best yield for propylene production was achieved at 480 °C with a water to methanol ratio of 0.7. Subsequently, kinetic experiments were performed at 480 °C and a water to methanol ratio of 0.7 using feeds with different amounts of C4 and C5/C6 hydrocarbons as recycle streams. Species material balances for the integral tubular reactor along with power-law rate functions and the Arrhenius equation for rate constants were employed in an optimization algorithm to obtain the kinetic parameters. The predictive ability of the model was checked against experimental data, and the kinetic parameters were validated by additional experiments.

Facile fabrication of a plate-like ZSM-5 zeolite as a highly efficient and stable catalyst for methanol to propylene conversion

Zeolite catalysts with high propylene selectivity and superior stability are highly desirable in the methanol to propylene (MTP) conversion. Herein, plate-like MFI zeolites with different Si/Al (Ga) ratios were successfully prepared via a fluoride assisted strategy and applied in the MTP reaction. The influences of the zeolite morphology, acid density, and strength on the MTP activity as well as the reaction mechanism were clarified by combining spectroscopic and catalytic results. The plate-like MFI zeolites with lower acid density could efficiently suppress the aromatic-based cycle and promote the olefin-based cycle and thus exhibited a remarkable catalytic performance in the MTP conversion. However, owing to occurrence of irreversible hydrolysis of the Si-OH-Ga group during the MTP conversion, the catalytic activity of the Ga-MFI catalyst was not recyclable. On the contrary, the plate-like ZSM-5 catalyst shows excellent stability and recyclability in the MTP conversion.

Machine learning‐assisted multiscale modeling of an autothermal fixed‐bed reactor for methanol to propylene process

AbstractThe current commercial multistage reactor for methanol to propylene (MTP) process suffers from poor propylene selectivity and catalyst efficiency, mainly because of the low inlet methanol concentration and long residence time. In this work, we proposed an autothermal co‐current flow reactor for MTP process, where the reaction heat is continuously removed through heat exchange with cold reactants, thus single‐stage reactor can be used with higher methanol inlet concentration. The reactor feasibility was investigated by a three‐dimensional multiscale model, in which the diffusion–reaction interaction inside catalyst particle was described by a neural network model trained by machine learning. With the feeding methanol fraction increasing to 30%, propylene selectivity reaches 82.27% while the space velocity approaches 2.68 gMeOH gcat−1 h−1 at 99.97% methanol conversion, about 1.4 and 3.8 times those of a commercial multibed reactor, respectively. With proper catalyst bed dilution, the reaction temperature is well controlled between 700 and 754 K.

Xylene and n-Hexane Adsorption Performance of a Waste Methanol-to-Propylene Catalyst under Acid-Base Treatment

Spent methanol-to-propylene (MTP) catalysts have a large specific surface area and high porosity but are usually directly disposed of in landfills, and recycling is rare. In this study, spent MTP catalyst was moderately dealuminized with acids and etched with an alkali solvent to increase its specific surface area. A novel adsorbent was obtained. XRD, SEM, FT-IR, XRD, XRF, and MAS-NMR characterization shows that the adsorbent maintains a typical ZSM-5 zeolite structure, and the dealumination effect of H2C2O4 is better than that of HCl. HCl mainly removes the framework aluminum of the molecular sieve; H2C2O4 not only removes the framework aluminum but also dissolves some of the nonframework aluminum, which increases the BET-specific surface area and pore diameter. The spent catalyst maintains an irregular ellipsoidal shape. After alkali treatment, the surface of the spherical particles becomes rough. With increasing alkali concentration, the damage degree increases. After treatment with 4 mol/L H2C2O4 and 0.1 mol/L NaOH, the p-xylene and n-hexane adsorption capacities reach the maximum, with values of 141.04 mg/g and 106.87 mg/g, respectively, 20.7% and 16.2% greater than those before treatment. These findings indicate that modified spent MTP catalyst has the potential for application in the removal of VOCs from the air.