MTG Process Research Articles

Design, thermodynamic and economic evaluation, and optimization of gasoline production from refinery furnaces flue gas

In this paper, the conversion of refinery furnaces’ flue gas into gasoline through the MTG process is investigated. This approach not only reduces greenhouse gas emissions, but also produces a high-value product, providing economic incentives to adopt this technology. The proposed integrated system comprises an organic Rankine cycle, an amine-based carbon capture unit, a methanol synthesis unit, and an MTG unit. In this study, we evaluated the technical and economic aspects of this conversion process, including the thermodynamic and cost analysis, to assess its viability as a sustainable solution for mitigating CO2 emissions from refineries. Also, using response surface methodology combined with the Box-Behnken design, the proposed integrated system was optimized to minimize the gasoline production cost. The thermodynamic assessment concludes that the energy and exergy efficiencies of the overall system are 73.12% and 85.24%, respectively. The proposed system yields an annual gasoline production rate of >184 million liters. The estimated total capital investment for the proposed system is 172.16 M$, which the methanol synthesis unit with a share of 48.65% is the most expensive one. The results give a gasoline production cost of 1.58 $/kg or 4.28 $/gal for the optimized case. Also, hydrogen has the highest contribution in the production cost, so with a 20% decrease in the price of hydrogen, the production cost of gasoline decreases by 18.71%. With this rate of technological improvement, reductions in the price of hydrogen seem inevitable in not-so-distant years, which makes the proposed system of converting refinery furnaces’ flue gas into gasoline became desirable.

Steam-assisted methanol conversion to green fuel over highly efficient hierarchical structured MFI/BEA composite zeolite synthesized by incorporation method

In this study, we have investigated the effect of water co-feeds on products distribution and coking behavior of a new composite catalyst in the MTG process. A novel ZSM-5/Beta bi-phase composite catalysts were synthesized via a hydrothermal crystallization method. Catalysts were all characterized by considering their crystallinity (XRD analysis), morphology (FE-SEM analysis), surface area, pore volume (N2 adsorption/desorption technique), and acidity (NH3-TPD analysis). The catalytic performance of the synthesized catalysts was tested by the MTG reaction in WHSV of 20 h−1, the temperature of 400 °C, atmospheric pressure, and water content of 0, 10, and 20%. Over the ZSM-5/Beta composite catalyst, the methanol diluted with 10% water resulted in a 29% yield of gasoline compared with 21% over ZSM-5 and 66% selectivity to alkylated aromatics compared with 45% over ZSM-5. Adding water to the methanol had a key role in improving catalysts lifetime so that by using the feed with 10 wt% water, a lifetime about two times longer than pure methanol was observed. The higher activity over the ZSM-5/Beta sample co-feed with 10% water, was ascribed to overcoming the diffusion limitations and retarding catalyst deactivation in the presence of water.

A green approach for template free synthesis of Beta zeolite incorporated in ZSM-5 zeolite to enhance catalytic activity in MTG reaction: Effect of seed nature and temperature

A new composite zeolite, ZSM-5/Beta, was developed by incorporating Beta zeolite into the synthesis gel of ZSM-5 zeolite. Beta and ZSM-5 zeolite have been prepared from rice husk ash without using an organic template. First, the effect of synthesis temperature and seeding agent on structural properties of Beta zeolite was investigated. Then, prepared Beta zeolite was added to the ZSM-5 structure with the hydrothermal method. The prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, N2 physical adsorption, and temperature-programmed ammonia desorption techniques. Results indicated that the synthesis at a temperature of 150 °C and using Na-Beta seeds showed suitable crystallinity as well as textural properties. Furthermore, the crystalline structure of ZSM-5 wasn't damaged by the addition of Beta zeolite. The incorporation of Beta zeolite into the ZSM-5 structure increased the total pore volume by 45%. The micropore volume and the mesopore volume also increased by 2% and 300%, respectively. Using composite zeolite led to tuning the catalyst acidity. The catalytic activity of this new ZSM-5/Beta composite structure was evaluated in the MTG process at 400 °C, WHSV of 20 h−1 and atmospheric pressure. The results illustrated that over this composite catalyst, the selectivity to alkylated aromatics increased by almost 13% compared to the initial ZSM-5 zeolite. Furthermore, gasoline production yield and catalyst lifetime also increased by 9% and 61% respectively compared to the initial ZSM-5 zeolite. The better performance of the composite zeolite can be ascribed to its higher mesoporous volume and lower acidity. The composite catalyst has a lower number of acid sites, especially the number of strong acid sites that are one of the main factors in coke deposition.

Zeolite-based catalysts for exergy efficiency enhancement: The insights gained from nanotechnology

The need for optimization of energy consumption and its efficient utilization has become a serious challenge in recent years; hence, several groups from all around the world are attempting to find new ways for efficient usage and storage of energy. Various methods have been developed to save the energy through the most optimal routes. In this way, the use of inorganic materials and applying them as and/or with catalysts has taken a new pathway in scientific works. Nano-size HZSM-5 lies in a special class of zeolite-based catalysts which can be synthesized from diatomite as silica source using hydrothermal procedure. The impact of such catalysts on exergy efficiency enhancement in gasoline production from methanol or MTG process has been studied in this work. It was found that the exergy efficiency improves in the heat exchangers with the aid of HZSM-5 nano-size catalysts, and 210 °C was found as the optimum temperature in the towers at which the highest exergy efficiency and the least lost work in the process was achieved. Moreover, it was found that by increasing the pressure, hydrocarbons output rate in the tower increases continuously. Moreover, operating conditions of distillation column were studied to be optimized in order to enhance the exergy efficiency of fractionation unit. These all are gained from nano-scale catalysts synthesized in this work. Changing the feed injection tray improved the exergy efficiency of the distillation column. In the light of results, it was demonstrated that nano ZSM-5 catalyst increases the exergy efficiency of MTG process through a time- and cost-effective route.

The effect of HZSM-5 catalyst particle size on gasoline selectivity in methanol to gasoline conversion process

Experimental parameters were optimized by the analysis of variance (ANOVA) by D-optimal experimental design using three levels of pressure, temperature, weight hourly space velocity (WHSV) and catalyst particle size. The effects of the above parameters on the gasoline selectivity in methanol to gasoline conversion (MTG) were studied. Given the effect of catalyst particle size on MTG process, three HZSM-5 catalysts with particle sizes of 90, 2000 and 4000nm were synthesized and the effect of this important parameter was studied along with those of other parameters. Fischer test results showed that catalyst particle size and temperature are the most and least effective parameters, respectively, in the ranges studied. The most important two-way interaction variable was that of temperature and WHSV. The optimal conditions to achieve maximum gasoline selectivity in maximum conversion are pressure=9.40bar, temperature=392°C, WHSV=1h−1 and particle size=994nm. In addition, by implementing industrial conditions in the equation proposed by the experimental design, the optimal catalyst particle size was found to lie in the 2500–3300nm range.

The catalytic properties evolution of HZSM-5 in the conversion of methanol to gasoline

Catalytic properties evolution of HZSM-5 in MTG process was demonstrated basing on the analysis of spent catalysts with characteristic reaction.

The effect of HZSM-5 catalyst particle size on kinetic models of methanol to gasoline conversion

In chemical reactions, a principal and influential parameter is particle size. The effect of HZSM-5 catalyst particle size on the kinetics of methanol conversion to gasoline has been investigated in this work. Three catalysts of 90nm (Z1), 1μm (Z2) and 4μm (Z3) containing Si/Al ratios of 25, and a 90nm sized with a Si/Al ratio of 50 (Z4) were prepared. The experiments were performed at temperatures of 598, 623 and 648K at different feed rates. Chen and Schipper kinetic models, credible models for MTG process, were chosen to study the catalyst particle size effect on MTG process kinetics. R2 adj. values for each of the models show that the experimental data are in relatively good agreement with Chen and Schipper models. In order to check the results of modeling with experimental data, objective function parameter was applied as a criterion and Z1 catalyst showed the best performance using Chen model, closely followed by Z2.

Low cost rapid route for hydrothermal synthesis of nano ZSM-5 with mixture of two, three and four structure directing agents

This article aims at investigating the effect of different structure directing agents such as TPAOH, TPABr, EDA and ethanol solely or as dual, triple or quad mixture on the synthesis and characteristics of nano ZSM-5 zeolite such as crystallinity and crystal size, and also its catalytic properties in MTG process. It is found out that application of a quad mixture of different structure directing agents not also reduces the synthesis cost compares to samples synthesized with one template but also ZSM-5 with small particle size, high crystallinity and improved catalytic properties will be obtained in a short crystallization period.

Synthesis of gasoline fractions from CO and H2 through oxygenates

The technology for the manufacturing of gasoline fractions (synthetic hydrocarbons) from synthesis gas (syngas) on zeolites through the oxygenate production step as developed at the Topchiev Institute of Petrochemical Synthesis, differs from the classical MTG process of ExxonMobil in that the oxygenate and gasoline production steps are integrated in one circuit. In the new technology, the synthetic hydrocarbons contain 6 to 27 wt % aromatic hydrocarbons (benzene and durene ≤2 wt %) depending on the H2/CO ratio in syngas. When syngas with H2/CO ≤ 3.5 in the vapor-gas mixture arriving at the gasoline production stage is used, an increased methanol (MeOH) content is observed and the MeOH conversion is incomplete with the exhaustive conversion of dimethyl ether (DME). To increase the involvement of MeOH in the synthesis of the gasoline fraction, the influence of various parameters on the conversion of MeOH and DME has been studied. It has been shown that a change in the composition of fresh syngas has a more significant effect notably on the MeOH, rather than the DME conversion into synthetic hydrocarbons and is enhanced with an increase in the MeOH weight hourly space velocity (WHSV). If the vapor-gas mixture arriving from the oxygenate production reactor at the step of production of the gasoline fraction contains more than 50 wt % MeOH, in order to improve the selectivity for the gasoline fraction, the synthesis should be conducted at a lower WHSV of oxygenates than in the case when the vapor-gas mixture contains DME alone.

Deactivation by coke deposition on the HZSM-5 catalysts in the methanol-to-hydrocarbon conversion

HZSM-5 used to be the main catalyst component for the MTG process of Exxonmobil Co. Catalyst deactivation by coke in methanol-to-hydrocarbon (MTH) over HZSM-5 was studied in a fixed-bed reactor by observing the activity and selectivity with time-on-stream at 500°C and WHSV=4.25h−1. The HZSM-5 with SiO2/Al2O3 ratios of 40 and 280 were synthesized and characterized with XRD, N2 adsorption/desorption and NH3-TPD. The used catalysts were investigated by N2 adsorption/desorption, XRD, elemental analysis (EA) and UV–vis spectroscopy to identify the nature of coke. If the acidity of HZSM-5 is low (SiO2/Al2O3=280), the coke deposited is mainly mono- or bi-aromatic which did not affect the catalyst activity significantly. On the other hand when the acidity is high (SiO2/Al2O3=40), the coke deposited is polycyclic aromatics with 3 or 4 fused rings which leads to significant deactivation after 24h. It is presumed that the coke on the HZSM-5 with low acidity must be located inside the pores and/or in the framework, since the coke particles without polycyclic aromatics should be small. The deactivation of HZSM-5 with high acidity is mainly caused by the bulky coke molecules, most probably inducing the topological blocking of the zeolite pores and channels.

Design of microporous materials: A novel generation of solid acids

Abstract ZSM-5 zeolite materials were synthesized under acidic conditions using a fluoride-mediated route. Our approach consisted in changing the nature of the silica source in the starting synthesis gel via two different pathways: (i) polymeric silica having different surface specific areas (aerosils 130, 200 and 300); and (ii) dissolution–recrystallization of a thin silica upper layer of a silicon carbide substrate. The zeolites were characterized by XRD, SEM, and H/D exchange titration methods. 27 Al MAS NMR analysis revealed that all aluminum was present in a tetrahedral coordination, thus being present inside the zeolite framework. A complete self-transformation of aerosils 130, 200 and 300 sources into highly crystalline ZSM-5 material was achieved, thus leading to a star-like morphology for the MFI crystals. Hence, this study reports the first observation of this unusual star-like morphology for zeolite crystals. It is therefore possible to synthesize zeolites having properties tailored at the microscopic level. Finally, these structured materials were both active and selective catalysts in the conversion of methanol-to-gasoline (MTG process).

Autoassembly of Nanofibrous Zeolite Crystals via Silicon Carbide Substrate Self-Transformation

ZSM-5 zeolite nanofibers with a size of 90 nm and lengths up to several micrometers were prepared via in-situ silicon carbide support self-transformation. The morphology and aggregation degree of these zeolite nanofibers could be modified by adjusting the pH conditions, the nature of the mineralizer (OH- or F-), or the synthesis duration. The novelty consists of the preparation of zeolite nanowires without the use of any organogelating agent, along with controlled macroscopic shapes (extrudates, foam monolith) for direct use as a structured reactor. Finally, these materials are catalytically active in the conversion of methanol to gasoline range hydrocarbons (MTG process) and hence exhibit the typical solid acidity of zeolitic materials.

ROLE OF WATER IN THE KINETIC MODELING OF METHANOL TRANSFORMATION INTO HYDROCARBONS ON HZSM-5 ZEOLITE

The attenuating effect of reaction-medium water (feed and/or reaction product) on the kinetics of the steps of methanol transformation into hydrocarbons on a HZSM-5 zeolite catalyst was studied by means of a kinetic model. In this model, the effect of water was quantified in all the steps of the kinetic scheme by means of a kinetic parameter, which is constant with temperature under the conditions of the MTG process. At low temperature, under conditions in which only methanol dehydration occurs, the kinetics of this reaction is attenuated by the presence of water, and the coefficient that quantifies the attenuation decreases as temperature is increased. In addition to considering the effect of water content in the reaction medium, another innovation of the kinetic model proposed, compared to those proposed in the literature consisting of lumps, is the fact that the higher reactivity of dimethyl ether over methanol is taken into account. A step of cracking of gasoline lump hydrocarbons to produce light olefins (ethene and propene) was also taken into account. The kinetic model proposed was verified by using the results obtained in an integral isothermal fixed bed reactor, in the 573–723 K range, for an ample range of space time values. The results revealed that the effect of water is due to its adsorption on the active sites by competition with the intermediate compounds of the kinetic scheme.

Study of oxygenation process during the preparation of single domain YBCO bulk superconductors

The oxygenation process is an important step during the preparation of YBCO bulk superconductors by the MTG process. A high pressure oxygenation device has been built by our group. High pressure oxygen has been used in annealing. It is found that different oxygenation processes would lead in the different results. In comparison with the oxygenation process by flowing oxygen, the high pressure oxygenation technique has many more advantages. For example the capacity of the oxygen gas can be saved and the efficiency of oxygenation can be raised greatly.

Study of the regeneration stage of the MTG process in a pseudoadiabatic fixed bed reactor

The regeneration stage of a catalyst (prepared based on an HZSM-5 zeolite) has been studied in the process of transformation of methanol into hydrocarbons in a fixed bed reactor. The simulation of the operation requires knowledge of the longitudinal profile of coke content in the reactor at the end of the reaction stage. Longitudinal profiles of temperature, coke content and activity during the regeneration are calculated by solving the energy conservation equation in the reactor together with the kinetic equation for coke combustion and with the kinetic equation for reactivation (activity–coke content relationship). The results of the simulation have been experimentally verified in a laboratory unit provided with a pseudoadiabatic fixed bed reactor.

Role of water in the kinetic modeling of catalyst deactivation in the MTG process

AbstractA kinetic model is proposed for deactivation by coke of a HZSM‐5 zeolite catalyst used in the transformation of methanol into hydrocarbons in the 573–723 K range. The attenuating effect on coke deposition due to the presence of water in the reaction medium was quantified by a parameter that increases with reaction temperature. The slower deactivaton of the methanol dehydration step compared to the formation steps of olefin and gasoline lumps is taken into account. In view of the results, water content in the reaction medium is an efficient variable for controlling the results of activity–selectivity–deactivation. This model is not applicable for a temperature of 723 K when water content in the reaction medium is high, due to the fact that under these conditions the zeolite is subjected to irreversible deactivation.

Modern solid state double resonance NMR strategies for the structural characterization of adsorbate complexes involved in the MTG process

The reaction pathways in the methanol to gasoline conversion process are still not well understood. Although recent years have witnessed remarkable progress in recent years in the in situ characterization of these reactions, the nature of the bonding of the intermediates to the Bronsted acid sites of the zeolite catalyst is still the subject of intense debate. Our approach is to study the geometry of the binding of the methanol molecule to the zeolite surface using modern double resonance NMR spectroscopy. As model systems we chose the host/guest complexes formed in the systems zeolite NaX loaded with 13CH3I and zeolite HZSM-5 loaded with 13CH3OH, treated at various temperatures. By exploring the dipolar coupling strength between 13C and 27Al or 1H and 27Al using 1H–{27Al} and 13C–{27Al} rotational echo adiabatic passage double resonance (REAPDOR) NMR and simulation of the resulting dipolar evolution curves we have been able to determine carbon–aluminium and hydrogen–aluminium internuclear distances and thus to identify the nature of the adsorbate–zeolite complexes formed as a function of the processing conditions.

MTG Process in a Fixed-Bed Reactor. Operation and Simulation of a Pseudoadiabatic Experimental Unit

A simulation model has been proposed and used to predict the behavior of a laboratory pseudoadiabatic reactor for the transformation of methanol into hydrocarbons. The model incorporates recent advances in the kinetic modeling of the main reaction steps and of the deactivation by coke of the catalyst in the 350−450 °C range and is efficient for analyzing the effect of process conditions (space time, water content and inert gas in the feed, and inlet temperature) on the evolution with time on stream of the temperature profile along the reactor and on the yields of the product lumps.

Applications of In Situ NMR in Catalytic Processes of Organic Reactions

In situ MAS NMR has been demonstrated to be a superior technique for analyzing desorbed reactants, reacting adsorbates, intermediates and products. The results are useful for getting deeper insights into catalytic processes and reaction kinetics, and for re vealing the mechanisms of organic reactions. The utility of in situ NMR spectroscopy has demonstrated that this technique is an important means for the studies of catalytic organic reactions. The objective of this paper is to give a review on the generatio n of apparatus for in situ MAS NMR experiments, and to illustrate the applications of the in situ MAS NMR techniques in various important organic reactions catalyzed by solid catalysts. The typical reactions studied by in situ MAS NMR techniques include conversion of methanol to hydrocarbons (MTG process), aromatization of methane, ethylbenzene reaction over zeolite HMOR, observation of carbenium intermediates formation, and photocatalytic organic reaction.

IR Spectral Investigation of the Multistage Single Catalytic Process of CH4 Conversion into Higher Hydrocarbons over HZSM-5 Structurally Modified with an Oxidative Element

7The acidic zeolite HZSM-5 is modified by partial isomorphous substitution of the framework aluminum (Al) with an oxidative element during the zeolite synthesis. This is to develop an oxidative-acidic mediated catalyst suitable for the direct conversion of methane (or natural gas) into higher hydrocarbons in a multistage single catalytic process. The pure and modified ZSM-5 materials are highly crystalline of high morphology, which is shown by XRD and SEM. Pure ZSM-5 shows a single decomposition TGA band for the TPA + cations associated with the anionic framework Al. Besides, modified ZSM-5 shows a lower temperature band revealing weaker interaction of TPA + cations with the modifier element. The infrared spectrum of modified ZSM-5 shows a high frequency 3685 cm -1 band assigned to Bronsted sites weakly interacting with the modifier in addition and compared to the well-established more acidic Al-associated Bronsted sites absorbing at 3610 cm -1 . Thus, XRD, TGA, and IR show evidence of incorporating the modifier element in the framework. The modifier site catalyzes the CH 4 oxidation into H 2 C=O using molecular O 2 near 1 bar and 373 K. This is explicit in the spectral appearance of υ C=O at 1711 cm -1 and δ C-H at 1420 and 1375 cm -1 . This stage of the catalytic conversion is so peculiar to modified ZSM-5 that can never be catalyzed at any circumstance over ordinary ZSM-5. Bronsted sites associated with Al and modifier element interact strongly with H 2 C=O yielding unsaturated species defined by the weak υ C=C at 1675 cm -1 . Evidence of such interaction is shown as a downward shift of 23 cm -1 in the υ C=O of the gaseous H 2 C=O at 1734 cm -1 to 1711 cm -1 on the surface and absence of the Bronsted sites absorbing at 3610 and 3685 cm -1 . In effect, the latter Bronsted bands recover at the end of the catalytic process. The unsaturated species are higher aldehydes equilibrated in a keto-enol tautomeric structure. They eventually decompose in the temperature 473-573 K range into a mixture of hydrocarbons identified by υ C-H at 2960, 2935, 2913, and 2868 cm -1 and δ C-H at 1469 and 1385 cm -1 (aliphatics) and by υ ring at 1600 and 1510 cm -1 (aromatics). The IR spectral profile of the products is similar to that of Mobil methanol-to-gasoline MTG process. The mechanistic implications of this process are proposed on the basis of the IR spectral findings observed in the reaction gas phase and on the surface that shows no evidence for the MTG route, however.