Methanol To Gasoline Reaction Research Articles

Enhanced methanol to gasoline performance using nanosheet-like SAPO-11 catalyst

Herein, spherical and nanosheet-like SAPO-11s were successfully synthesized hydrothermally and utilized to catalyze the methanol-to-gasoline (MTG) process. The nanosheet-like SAPO-11 (SAPO-11-A) had a thickness of about 10 nm, while the spherical SAPO-11 (SAPO-11-B) had a particle size of around 11 μm. Compared to SAPO-11-B, the property of SAPO-11-A was enhanced by 42.9% in specific surface area (SSA), 38.1% in mesopore volume (Vme) and 20.2% in acid amounts, respectively. In terms of catalytic performance during the MTG reaction, SAPO-11-A demonstrated superior results not only in the methanol conversion (95.82%), gasoline-range hydrocarbons selectivity (58.76%) and iso/nparaffin ratio (8.17) but also in suppressed coke deposition (2.56%) compared with those (90.63%, 50.95%, 4.75 and 5.73%, respectively) of SAPO-11-B. Additionally, the optimal MTG process conditions were identified utilizing SAPO-11-A, demonstrating a methanol conversion rate of 98.34%, a gasoline hydrocarbon selectivity of 67.61%, an isoparaffin selectivity of 36.01% and an iso/nparaffin ratio of 10.94 at 380 °C, weight hourly space velocity (WHSV) of 2 h−1 and 1 MPa. These results highlight the potential of nanosheet SAPO-11 to produce gasoline-range hydrocarbons rich in isoparaffins.

Rapid and low-cost synthesis of ZSM-5 zeolite nanosheet assemblies for conversion of methanol to gasoline

Nanoscale zeolites with short diffusion paths show significantly enhanced mass transportation and easier accessibility for active sites in catalysis compared to microsized zeolites. However, the high cost and complex process involved in existing synthetic methods limit their application, so the development of a rapid and low-cost synthesis technology is of great significance. Herein, ZSM-5 zeolite nanosheet assemblies (Z5-NS-t) are rapidly synthesized by a microwave irradiation (MW) assisted seed-induced method using low-cost polyhexamethylene biguanide hydrochloride (PHMB) as a crystal growth inhibitor of the b-axis. The crystallization kinetics of the resultant materials and the formation mechanism of ZSM-5 zeolite nanosheets, as well as the influence of physico-chemical properties on their catalytic performance for the methanol-to-gasoline (MTG) reaction, are systematically investigated. Compared with the ZSM-5 nanoparticle assemblies (Z5-NP-60), which are synthesized by using the same method except for the addition of PHMB, Z5-NS-180 nanosheets with an approximate density of strong Brønsted acid sites exhibit excellent catalytic performance in the MTG reaction, giving rise to a high gasoline selectivity of 73.2% at a methanol conversion of 99.9% and a large amount of external carbon deposits. This is attributed to the synergy of accessibility of acid sites located in the pore intersections and the shorter diffusion paths for coke precursors out of the zeolite channel. This study provides an effective strategy for the synthesis of ZSM-5 nanosheets as catalysts for the MTG reaction, and it is expected to be applied for the synthesis of other zeolite nanosheets for important catalytic processes.

Facile synthesis of ultrafine nanosized ZSM-5 zeolite using a hydroxyl radical initiator for enhanced catalytic performance in the MTG reaction

ZSM-5 zeolite is extensively used as a catalyst in the methanol-to-gasoline (MTG) reaction, but many secondary reactions occur because of its large grain size and strong acidity. Thus, it is vital to explore new methods for the preparation of nanosized ZSM-5 zeolite with intercrystalline mesopores to facilitate the diffusion of substances while simultaneously decreasing the acidity. Here, we present a novel procedure for the synthesis of ultrafine nanosized ZSM-5 zeolites (Z5-Sx) at a low temperature (90 °C) that includes the addition of a hydroxyl radical initiator to the initial gel. For comparison, a series of ZSM-5 zeolites (Z5-Ty) were synthesized by crystallization at 170 °C using the traditional hydrothermal method. The influence of hydroxyl radicals on the characteristic properties of the Z5-Sx zeolites was investigated by XRD, SEM, HRTEM, N2 adsorption, and 29Si and 27Al MAS NMR spectroscopy as well as NH3-TPD and Py-IR measurements. The results revealed that the Z5-Sx series samples had smaller crystal sizes and higher mesoporosity than the control samples. In particular, a high content of framework Al atoms was observed at the channel intersections of the Z5-Sx series samples, resulting in a weaker acid strength in comparison with the Z5-Ty samples. This distribution of Al atoms resulted in the excellent catalytic performance of the synthesized Z5-Sx catalysts towards the MTG reaction, and the highest gasoline yield of 65.5% with a methanol conversion of 97.2% was obtained in the reaction with the Z5-S3 catalyst. Markedly, the Z5-S3 sample showed significantly improved catalytic stability and coke tolerance than the control samples.

Effect of acidic properties of hierarchical HZSM-5 on the product distribution in methanol conversion to gasoline

Hierarchical ZSM-5 zeolites with different SiO2/Al2O3 ratio but similar crystal size were directly synthesized by a single-template hydrothermal method, and the intrinsic effect of acidic properties on their catalytic performance in methanol to gasoline (MTG) reaction was comprehensively investigated. The physicochemical properties of HZSM-5 zeolites were characterized by XRD, N2 adsorption-desorption, SEM, NH3-TPD, FTIR, and TGA techniques. The results show good linear correlations between the yields of gasoline components and the relative content of Bronsted acid sites, and the hierarchical HZSM-5 zeolite with SiO2/Al2O3 molar ratio of 200 was firstly found to exhibit high reactivity, excellent product distribution and superior stability in MTG reaction, which can be attributed to its appropriate acid distribution with moderate Bronsted acid sites and proper B/L ratio, predominantly promoting gasoline range hydrocarbons production and inhibiting side reactions.

Dimethyl ether to hydrocarbons over ZSM-5: Kinetic study in an external recycle reactor

DME provides advantages in the valorization of feed streams of low H2/CO ratio, which are formed from feedstocks such as biomass or coal.It is currently accepted that the conversion of oxygenates, such as DME or methanol, to hydrocarbons proceeds via the dual-cycle mechanism.After inspection of several kinetic models developed for the methanol-to-gasoline (MtG) reaction, we show in this investigation that they have limited applicability when dimethyl ether (DME) is used as feedstock. Therefore, the development of a kinetic model able to represent the DME-to-hydrocarbons (DtH) over a ZSM-5 catalyst was necessary.In this research, we have developed a new kinetic model that considers main steps of the dual cycle mechanism, including: (i) formation of aromatic intermediates (polymethylbenzenes); (ii) dealkylation of the intermediates to produce ethylene and propylene; (iii) methylation of small olefins to increase the chain size of the hydrocarbons; (iv) hydrogenation of ethylene, propylene and butenes to produce the corresponding saturated compounds; and (v) dimerization reactions between propylene and butenes to produce higher hydrocarbons. Moreover, the kinetic parameters of this new model were estimated from regression analysis using kinetic data measured under gradientless conditions in a fixed-bed external recycle reactor over a wide range of conditions, with temperatures from 325 to 375 °C, weight hourly space velocities (WHSV) from 25 to 125 h−1, a total pressure of 1 bar and undiluted DME as feed. The newly developed model allowed a good description of the experimental results, showed better performance than models available in literature for the MtG reaction, and rendered kinetic parameters that met physicochemical and statistical constraints, showing good agreement with results from DFT calculations reported by other authors.

Facile One-Pot Synthesis of ZSM-5 Aggregates with Inter- and Intra-Crystalline Mesopores for Methanol to Gasoline Conversion

ZSM-5 aggregates consisting of superfine and hierarchical nanocrystals (combined with micropores and intra-crystalline mesopores) with an average size of 30 nm were prepared through one-pot synthesis with the assistance of anionic polyacrylamide (APAM). The resultant zeolites (AHN-ZSM-5) were characterized by XRD, ICP-OES, SEM, TEM, BET, NH3-TPD, Py-IR, and TG analyses and evaluated in the methanol to gasoline (MTG) reaction. Characterization results show that the hierarchical ZSM-5 aggregates possessed two kinds of mesopores, namely inter- and intra-crystalline mesopores. The amount of APAM considerably influenced the mesoporosity and textural properties of AHN-ZSM-5 zeolites. With the addition of APAM in the synthesis, the AHN-ZSM-5 zeolites exhibited large mesopore volume, large external surface area, and appropriate acidity. When applied in the MTG reaction, AHN-ZSM-5 demonstrated a catalytic lifetime that was 1.6 times longer than that of conventional ZSM-5 synthesized in the absence of APAM.

The effect of doping and steam treatment on the catalytic activities of nano-scale H-ZSM-5 in the methanol to gasoline reaction

In the transformation of methanol to gasoline (MTG), the selectivity to gasoline and the aromatic content in the produced gasoline are important factors. The catalytic activities of steam-treated and non-steam-treated nano-scale H-ZSM-5 (NHZ5) catalysts impregnated with Ag(I), Zn(II) or P(V) have been investigated in a continuous flow fixed bed reactor. The NH3-TPD results showed that after impregnation, the Ag/NHZ5, Zn/NHZ5 and P/NHZ5 catalysts contained comparatively more strong, medium-strong and weak acid sites, respectively. Treatment with steam decreased the number of acid sites in all the catalysts, but the pore volumes in the catalysts were larger which improved carbon deposition resistance resulting in prolonged lifetimes. After 6 h of MTG reaction, the selectivity to gasoline for the steam-treated catalysts, $$Ag_{H_2 O} /NHZ5$$ , $$Zn_{H_2 O} /NHZ5$$ and $$P_{H_2 O} /NHZ5$$ were 70.5, 68.4 and 68.7 wt-%, respectively, whereas their respective aromatic contents in the produced gasoline were 61.9, 55.4 and 39.0 wt-%. Thus $$P_{H_2 O} /NHZ5$$ is the most promising catalyst for MTG applications which can meet the China IV gasoline standard that the amount of aromatics in gasoline should be less than 48 wt-%.

Solvent‐Free Synthesis of c‐Axis Oriented ZSM‐5 Crystals with Enhanced Methanol to Gasoline Catalytic Activity

AbstractZSM‐5 crystals with controllable c‐axis length were successfully synthesized through a one‐pot solvent‐free route, with urea as an additive. X‐ray diffraction patterns (XRD) show that the prepared samples exhibit high crystallinity. N2 adsorption–desorption isotherms and mercury intrusion porosimetry (MIP) analysis together with TEM observations indicate that micro‐, meso‐, and macropores exist in the obtained samples. Catalytic tests for the methanol to gasoline (MTG) conversion showed that the prepared c‐axis oriented hierarchical ZSM‐5, which allow fast mass transfer, exhibited both 100 % methanol conversion and far longer lifetime (900 h) than those of ZSM‐5 with conventional morphology (350 h) in the MTG reaction. The enhanced MTG performance by the c‐axis oriented zeolite under one‐pot solvent‐free synthesis is of great importance as it is easily scaled‐up for industrial applications.

Selective conversion of small bio-oxygenates into high quality gasoline precursors over deactivated ZSM-5 in MTG reaction

Selective conversion of two small bio-oxygenates (i-propanol and propanal) into high quality gasoline precursors over deactivated ZSM-5 in methanol to gasoline (MTG) reaction was investigated in this paper. The deactivated ZSM-5 catalyst exhibited a perfect catalytic performance and lifetime for converting i-propanol and propanal to branched olefin and/or oxygenates by oligomerization. NH3-TPD and FT-IR analyses indicated that the deactivated ZSM-5 catalyst still retained a mild acidity, which was strong enough for conversion of i-propanol and propanal due to their own high reactivity. An integration scheme of high quality and aromatic free bio-gasoline production with MTG process was thus proposed, requiring no additional investments on infrastructure and catalyst.

Hydrothermal synthesis of nanocrystalline H[Fe, Al]ZSM-5 zeolites for conversion of methanol to gasoline

Nanocrystalline H[Fe, Al]ZSM-5 zeolites with different Fe content were synthesized by hydrothermal method with tetrapropylammonium hydroxide (TPAOH) as structure-directing agent (SDA), in which tetraethyl orthosilicate (TEOS) and sodium aluminate (NaAlO2) were used as Si and Al sources, respectively. The prepared samples were characterized by means of techniques such as XRD, SEM, N2 adsorption–desorption, ICP-AES, UV–Vis, NH3-TPD, pyridine-FTIR and FT-IR. The results indicated that Fe species could be incorporated into ZSM-5 zeolite framework in the forms of isolated Fe3+ and small oligomeric FexOy clusters, resulting in the formation of some new active sites and the lower Brønsted acid sites content. The catalytic performances of prepared nanocrystalline H[Fe, Al]ZSM-5 zeolites were evaluated by methanol to gasoline (MTG) reaction in a fixed bed stainless-steel reactor. The catalytic results illustrated that the incorporation of Fe enhanced the activity and stability of nanocrystalline H[Fe, Al]ZSM-5 catalysts in MTG reaction and reduced the yield of aromatics in gasoline. The methanol conversion was higher than 99% for about 110h by optimizing the Fe content, meanwhile, the gasoline yield reached up to 32.7%, the aromatics and durene selectivity were controlled to a low level of 38.7% and 0.47%, respectively.

Synthesis of C2+ hydrocarbons by CO2 hydrogenation over the composite catalyst of Cu–Zn–Al oxide and HB zeolite using two-stage reactor system under low pressure

The combination of methanol synthesis and methanol-to-gasoline (MTG) reaction is a beneficial process to produce particular C2+ hydrocarbons from CO2 and H2, because MTG reaction can produce C2+ hydrocarbons selectively without the formation of methane. However, the composite catalysts consisting of methanol synthesis catalyst and zeolite previously reported have produced C2+ hydrocarbons in poor yields especially under low pressure conditions. This paper reports the high yield production of C2+ hydrocarbons by CO2 hydrogenation using a two-stage reaction system consisting of a Cu–Zn–Al oxide catalyst in the first reactor and a composite catalyst of the Cu–Zn–Al oxide and HB (zeolite beta) in the second reactor. The key points of this system are reversed water-gas-shift (RWGS) reaction in the first reactor and the following H2O removal before the second reactor. The gas mixture supplied to the second reactor containing much amount of CO and little H2O enhanced the methanol synthesis and suppressed the methanol decomposition to CO over the Cu–Zn–Al oxide catalyst in the composite catalyst, promoting the MTG reaction to produce C2+ hydrocarbons over HB zeolite. The highest yield of C2+ hydrocarbons reached to approximately 15C-mol% under 0.98MPa.

Modification of nanocrystalline HZSM-5 zeolite with tetrapropylammonium hydroxide and its catalytic performance in methanol to gasoline reaction

Nanocrystalline ZSM-5 zeolite was modified with tetrapropylammonium hydroxide (TPAOH) solution. The effect of the TPAOH treatment time on the catalytic performance of HZSM-5 was investigated in methanol to gasoline (MTG) reaction. The modified samples were characterized using X-ray diffraction, scanning electron microscopy, 27 Al and 29 Si magic-angle spinning nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, N 2 adsorption, and NH 3 temperature-programmed desorption. The HZSM-5 structure was basically unchanged after modification, but the relative crystallinity increased and the crystal morphology was more regular. The Brunauer-Emmett-Teller surface area, the micropore surface area, the surface Si/Al ratio, and the amount of strong acid sites increased; this might be caused by desilication and dealumination, and secondary crystallization of the zeolite during the treatment. The stability of the catalyst was significantly improved after modification, as reflected by the increased lifetime from 70 h to above 170 h in MTG reaction. The catalyst lifetime increased with increasing TPAOH treatment time. Hydrogen transfer reactions became faster and led to more isoparaffins and less olefins in the liquid products. 采用四丙基氢氧化铵(TPAOH)溶液对纳米ZSM-5分子筛进行改性, 运用X射线衍射/扫描电镜/ 27 Al和 29 Si固体核磁/X射线光电子能谱/N 2 物理吸附脱附法和NH 3 程序升温脱附等手段对所制样品进行了表征, 并评价了其催化甲醇制汽油反应性能. 结果表明, 改性后的HZSM-5相对结晶度增加, 晶体形貌更加规整, 表面硅铝比增加, 比表面积和微孔表面积增大, 强酸位酸量增多. 同时, TPAOH改性不仅可以使分子筛脱硅脱铝, 而且伴有二次晶化补硅补铝, 改变了分子筛的硅铝分布. 改性的HZSM-5在甲醇制汽油反应中的稳定性大幅度提高, 其寿命由70 h增至170 h以上, 随着TPAOH处理时间的增加, 催化剂寿命增加, 氢转移反应加快, 导致油相产品中异构烷烃增多, 烯烃减少. Tetrapropylammonium hydroxide treatment of the HZSM-5 zeolite improved the diffusion capacity and coke tolerance through desilication, dealumination, and secondary crystallization, reflected by the significantly increased catalyst lifetime.

Preparation of hierarchical mesoporous Zn/HZSM-5 catalyst and its application in MTG reaction

Abstract The hierarchical mesoporous Zn/ZSM-5 zeolite catalyst was prepared by NaOH treatment and Zn impregnation, and its application in the conversion of methanol to gasoline (MTG) was studied. N 2 adsorption-desorption results showed that the mesopores with sizes of 2-20 nm in HZ5/0.3AT was formed by 0.3 M NaOH alkali treatment. The zeolite samples after modification were also characterized by XRF, AAS, XRD, SEM and NH 3-TPD methods. Zn impregnated catalyst Zn/HZ5/0.3AT exhibited dramatic improvements in catalytic lifetime and liquid hydrocarbons yield. The selectivity of aromatic hydrocarbons was also improved after Zn impregnation. It is suggested that the mesopores of Zn/HZ5/0.3AT enhanced the synergetic effect of Zn species and acid sites and the capability to coke tolerance, which were confirmed by the results of catalytic test and TGA analysis, respectively.

Hierarchical ZSM-5 prepared by guanidinium base treatment: Understanding microstructural characteristics and impact on MTG and NH 3-SCR catalytic reactions

An H-ZSM-5 zeolite sample consisting of large particles (5–15 μm) was synthesized and base treated using sodium hydroxide, guanidinium hydroxide and guanidinium carbonate to create a hierarchical pore system. In the case of sodium hydroxide as demetallation agent a high degree of mesoporosity was achieved and with guanidinium hydroxide, mesoporosity was observed after prolonged treatment. All samples were tested in the methanol-to-gasoline (MTG) reaction and iron-impregnated samples were tested for selective catalytic reduction of NO with ammonia (SCR). In the MTG reaction an improved catalyst lifetime was observed which has been correlated to the creation of mesopores. In the SCR reaction improved NO conversion was observed for all base treated samples. In accordance with spectroscopic results this has been attributed to a higher abundance of active and dispersed Fe sites in the base treated samples. All samples were characterized by a multitude of experimental techniques including physisorption measurements, electron microscopy and spectroscopic methods.

Assessing the acid properties of desilicated ZSM-5 by FTIR using CO and 2,4,6-trimethylpyridine (collidine) as molecular probes

A series of desilicated ZSM-5 catalysts previously shown to have improved catalytic performance in the MTG (methanol-to-gasoline) reaction [M. Bjørgen, F. Joensen, M.S. Holm, U. Olsbye, K.-P. Lillerud, S. Svelle, Appl. Catal. A 345 (2008) 43] was subjected to thorough examination using FTIR. Clearly, defects represented by internal Si-OH sites are removed upon NaOH treatment. In a parallel manner, free Si-OH sites increase in concentration and the results point to a selective mechanism for formation of mesopores as the framework dissolution preferentially takes place at defective sites in the crystallites. The acid properties of the desilicated materials were investigated by applying CO and collidine (2,4,6-trimethylpyridine) as molecular probes. Monitoring the induced frequency shifts upon CO adsorption at liquid N2 temperature revealed that the desilication procedure did not alter the acid strength of the Brønsted sites significantly. This weakens the explanation linking improved catalytic behaviour, such as increase in both catalyst activity and hydrogen transfer activity, to modified Brønsted acid strength. Simultaneous to the mesopore formation resulting from the desilication, strong Lewis acid sites were generated, presumably from dislodged framework aluminium. Collidine, which is too bulky to enter the micropore system of ZSM-5, could access Lewis acidity, suggesting that these sites were predominantly generated on the external surface or in the newly created mesopores. Additionally, by first saturating the zeolite surface with collidine and subsequently adsorbing CO, we show that barely any Lewis acidity was uncoordinated post-collidine saturation while the Brønsted acidity continuously was protected behind the micropore system. It is hypothesized from the present study that the desilication procedure can lead to a slight dealumination of the samples while forming Lewis acidity preferentially at the crystal surface.

Synthesis of isoalkanes over Fe–Zn–Zr/HY composite catalyst through carbon dioxide hydrogenation

The reaction path of isoalkanes formation via CO2 hydrogenation was studied over the Fe–Zn–Zr/HY composite catalyst, which gives high selectivity to isoalkanes. The results indicate that the reverse water–gas shift reaction is not the indispensable step for the synthesis of hydrocarbons. And i-C4 (iso-butane) is formed from propylene and methanol through MTG (methanol to gasoline) reaction and i-C5 (iso-pentane) obtained from the reaction of C2 and C3 through the additive dimerization. A part of C1, C4 is formed on the sole Fe–Zn–Zr catalyst from methanol for the CO2 hydrogenation over Fe–Zn–Zr/HY composite catalyst.

Different behaviors of HZSM-5 zeolites synthesized in different procedures in loading of MoCl5 and methanol to gasoline (MTG) reaction

MoCl5 was loaded on the HZSM-5 samples synthesized with or without organic template. Besides differences in their surface migration and catalytic properties in MTG reaction, the Al species in the former is found to be more stable than that of the latter.

Change of catalytic properties of Fe [sbnd]ZnO/zeolite composite catalyst in the hydrogenation of carbon dioxide

The hydrogenation of carbon dioxide was examined using the composite catalysts which were obtained by the physical mixing of Fe ZnO and HY zeolite. Fe ZnO was a typical F-T (Fischer-Tropsch) catalyst and Fe ZnO/HY is a composite catalyst which is able to induce a combined methanol synthesis and MTG (Methanol-to-Gasoline) reaction. To study these unique catalytic behaviors of Fe ZnO/HY, the adsorption and the dissociation of carbon monoxide on Fe ZnO as well as TPR measurements were carried out. Fe ZnO is able to produce hydrocarbons by F-T reaction and methanol. In the absence of zeolite, Fe ZnO exerts its ability for F-T reaction. However, HY diminishes the activity for F-T reaction and hydrocarbons were obtained via methanol formed over the modified Fe ZnO

Hydrogenation of carbon dioxide over copper-pyrochlore/zeolite composite catalysts

The hydrogenation of CO 2 was studied over composite catalysts obtained by mixing Cu-based methanol synthesis catalyst and HY zeolite. A mechanism associating methanol synthesis and MTG (methanol to gasoline) reaction allowed the formation of C 1-C 4 hydrocarbons. It was found that the catalytic behaviors of the composite catalysts were favorably influenced by the characteristics of the methanol synthesis catalysts. The Cu-La 2Zr 2O 7 catalyst we recently developed associated with HY zeolite exhibited interesting performances in hydrocarbon synthesis. The addition of ZrO 2 to CuLa 2Zr 2O 7/HY enhanced the ability to produce hydrocarbons. Comparing composite catalyst systems prepared with different Cu-based methanol synthesis catalysts, the effect of Na contamination on methanol and hydrocarbon formation over composite catalysts were also discussed.

Effects of Sulfur-containing Compounds on Methanol to Conversion over ZSM-5 Cataiyst

Methanethiol was completely decomposed to form hydrocarbons and hydrogen sulfide (H2S)during the MTG (Methanol To Gasoline) reaction on H-ZSM-5 under pressurized conditions. Sulfur-containing compounds in the feed suppressed the gas formation and promoted the C4+ aliphatics while keeping the aromatics formation constant.Although the pulse treatment of the H-ZSM-5 with H2 showed no effect on the products distribution under atmospheric conditions, the low concentration of hydrogen sulfide (105ppm)in the feed promoted the olefin contents in lower hydrocarbons while keeping the selectivities of C-C3 hydrocarbons, C4+ aliphatics, and aromatics unchanged. Hydrogen sulfide was assumed to suppress the transfer hydrogenation of olefins by surface hydrogen which was produced during the aromatization of olefins.