Performance In Conversion Of Methanol Research Articles

Insight into the effect of F− on acidity of H-SAPO-18 and its catalytic performance for conversion of methanol to olefins

In this study, F− was added to the synthesis gel to regulate the acid property of SAPO-18 molecular sieve and enhance its catalytic performance for the methanol-to-olefin (MTO) reactions. The results indicate that adding an appropriate amount of F− during synthesis can increase the crystallinity of SAPO-18 molecular sieve and reduce the overall strong acid density and external surface acid content. The H-SAPO-18-I-20-0.0025 molecular sieve exhibits a much higher catalytic lifetime (1000 min) and light olefins selectivity (45.2% to propene and 96.1% to C2-5=) in MTO at 400 °C than those of the traditional H-SAPO-18-1-0. The results of the isotope labeling experiments, GC-MS, and 13C MAS NMR results provided direct evidence that the aromatic-based cycle contributes more to the conversion of methanol into light olefins, and hexamethylbenzene serves as the most abundant hydrocarbon species that produces propene via the paring route.

Insights into the Role of Nanorod-Shaped MnO2 and CeO2 in a Plasma Catalysis System for Methanol Oxidation.

Published papers highlight the roles of the catalysts in plasma catalysis systems, and it is essential to provide deep insight into the mechanism of the reaction. In this work, a coaxial dielectric barrier discharge (DBD) reactor packed with γ-MnO2 and CeO2 with similar nanorod morphologies and particle sizes was used for methanol oxidation at atmospheric pressure and room temperature. The experimental results showed that both γ-MnO2 and CeO2 exhibited good performance in methanol conversion (up to 100%), but the CO2 selectivity of CeO2 (up to 59.3%) was much higher than that of γ-MnO2 (up to 28.6%). Catalyst characterization results indicated that CeO2 contained more surface-active oxygen species, adsorbed more methanol and utilized more plasma-induced active species than γ-MnO2. In addition, in situ Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were applied with a novel in situ cell to reveal the major factors affecting the catalytic performance in methanol oxidation. More reactive oxygen species (O22-, O2-) from ozone decomposition were produced on CeO2 compared with γ-MnO2, and less of the intermediate product formate accumulated on the CeO2. The combined results showed that CeO2 was a more effective catalyst than γ-MnO2 for methanol oxidation in the plasma catalysis system.

Control of the proximity of bifunctional zeolite@Al2O3 catalysts for efficient methanol conversion into hydrocarbons

Bifunctional catalysts are widely applied for many important reactions as the synergetic effect of two types of active sites remarkably improves catalysis performance. However, their bifunctionality has not been fully exploited since the proximity of bifunctional catalysts is hard to control. Herein, we demonstrate a bifunctional ZSM-5@Al2O3 catalyst with a core-shell structure and a nano-scale proximity by in-situ growth of γ-Al2O3 nanosheets on the surface of ZSM-5 crystals for methanol conversion. The nano-scale proximity endows the catalyst with higher reaction activity and C2–C3 olefins yield (53 %) in comparison to the catalysts with micro-scale proximity (20 %) and millimeter-scale proximity (27 %), which can be attributed to the fluent transport of the reaction intermediates between two types of active sites. This strategy for constructing bifunctional catalysts with nano-scale proximity is conducive to understanding the relationship between proximity and catalytic performance in methanol conversion.

CFD Modeling of Methanol to Light Olefins in a Sodalite Membrane Reactor using SAPO-34 Catalyst with In Situ Steam Removal.

In this work, the performance of a sodalite membrane reactor (MR) in the conversion of methanol to olefins (MTO process) was evaluated for ethylene and propylene production with in situ steam removal using 3-dimensional CFD (computational fluid dynamic) technique. Numerical simulation was performed using the commercial CFD package COMSOL Multiphysics 5.3. The finite element method was used to solve the governing equations in the 3- dimensional CFD model for the present work. In the sodalite MR model, a commercial SAPO-34 catalyst in the reaction zone was considered. The influence of key operation parameters, including pressure and temperature on methanol conversion, water recovery, and yields of ethylene, propylene, and water was studied to evaluate the performance of sodalite MR. The local information of component concentration for methanol, ethylene, propylene, and water was obtained by the proposed CFD model. Literature data were applied to validate model results, and a good agreement was attained between the experimental data and predicted results using CFD model. Permeation flux through the sodalite membrane was increased by an increase of reaction temperature, which led to the enhancement of water stream recovered in the permeate side. The CFD modeling results showed that the sodalite MR in the MTO process had higher performance in methanol conversion compared to the fixed-bed reactor (methanol conversion of 97% and 89% at 733 K for sodalite MR and fixed-bed reactor, respectively).

Relation of Catalytic Performance to the Aluminum Siting of Acidic Zeolites in the Conversion of Methanol to Olefins, Viewed via a Comparison between ZSM-5 and ZSM-11

ZSM-5 and ZSM-11 zeolites are similar in their crystalline framework structure, acidity, morphology, and textual properties but considerably different in their catalytic performance for conversion of methanol to olefins (MTO). Such an unexpected but exciting finding was extensively explored by various techniques and density functional theory calculations. A detailed investigation shows that it is the different Al distribution in the ZSM-5 and ZSM-11 framework that causes the significant difference in MTO catalytic performance. In ZSM-5, Al atoms are enriched in the intersection, whereas in ZSM-11, the Al atoms are concentrated in the straight 10-membered ring channel. The acid sites located in the intersection enhance the arene-based cycle that generates more ethene, alkanes, and aromatics. Nevertheless, these hydrocarbon molecules can easily diffuse out of the zeolite channel, hence retarding the deposition of carbonaceous materials and increasing catalytic stability. However, the acid sites located in t...

High Zn/Al ratios enhance dehydrogenation vs hydrogen transfer reactions of Zn-ZSM-5 catalytic systems in methanol conversion to aromatics

Two series of Zn-ZSM-5 catalysts were prepared by ion exchanging two commercial zeolites with different Si/Al ratios (40 and 15) with increasing Zn loadings. The nature of the Zn sites in the zeolite was studied by spectroscopy using laboratory and synchrotron techniques. All the evidences suggest that catalytic activity is associated with [Zn(H2O)n(OH)]+ species located in the exchange positions of the materials with little or no contribution of ZnO or metallic Zn. The effect of Zn/Al ratio on their catalytic performance in methanol conversion to aromatics has been investigated. In all cases, higher Zn content causes an increase in the yield of aromatics while keeping the production of alkanes low. For similar Zn contents, high densities of Al sites favour the hydrogen transfer reactions and alkane formation whereas in samples with low Al contents, and thus higher Zn/Al ratio, the dehydrogenation reactions in which molecular hydrogen is released are favoured.

Synthesis of SAPO-34 catalysts via sonochemically prepared method and its catalytic performance in methanol conversion to light olefins

Methanol-to-olefin (MTO) reaction was investigated over sonochemically (SAPO-34-U40, SAPO-34-U70, SAPO-34-U100) and hydrothermally (SAPO-34-HT) prepared nanocatalysts. The catalytic performance of prepared samples was investigated over all samples at 450 °C and over SAPO-34-U40 at 350–450 °C temperature range. The higher yield ~ 97 wt% (31.4 wt% C2=, 49.4 wt% C3= and 16.1 wt% sumC4=) of light olefins was obtained at 375 °C on SAPO-34-U40. Physico-chemical properties of catalysts were characterized by XRD, SEM, BET, ICP techniques. XRD analysis showed suitable crystalline structure and SEM images confirmed perfect crystallinity of sonochemically prepared samples. BET analysis indicated remarkable surface area of SAPO-34-U40. The amount of carbon deposits and character of coke was determined by TPO analysis. The higher amount of coke was determined over SAPO-34-HT in comparison to another’s at 450 °C. The character of coke deposited over SAPO-34-U40 was similar for 375–425 °C temperatures.

Synthesis of SAPO-34 Molecular Sieves via Novel Intermittent Hydrothermal Treatment and Its Effect on the Crystallization and Product Properties

Intermittent hydrothermal treatment was introduced into the synthesis of SAPO-34 molecular sieves to control the nucleation and the growth in the crystallization. The effect of the crystallization time, the order of long-time and short-time crystallization in two-stage crystallization, and frequency in multi-stage crystallization on synthesis, physicochemical properties and catalytic performance for conversion of methanol to light olefins (MTO) has been studied. The results show that pure SAPO-34 can be obtained with increasing crystallization time. The interruption of the initial crystallization is more beneficial for improving the Si distribution and the MTO catalytic performance of SAPO-34 molecular sieves. The sample obtained by repeatedly alternating heating and cooling during crystallization shows smaller particle size, higher acidity, longer lifetimes and higher yields of ethylene than that obtained by the conventional continuous crystallization at high temperature.

Insight into the effect of incorporation of boron into ZSM-11 on its catalytic performance for conversion of methanol to olefins

The MTO catalytic performance of ZSM-11 can be finely tuned by incorporating boron through regulation of aluminum location in the framework.

Effect of ZSM-5 crystal size on its catalytic properties for conversion of methanol to gasoline

Four-sized monodispersed ZSM-5 crystals, being 70, 200, 400 and 650 nm, were hydrothermally synthesized by changing the H2O/Si molar ratio in the synthesis gel, and characterized with XRD, TEM, BET and NH3-TPD techniques. The crystal size effect of ZSM-5 on its catalytic performance for conversion of methanol to gasoline (MTG) was investigated. It was shown that the external surface area of the sample decreased with its crystal size, while the acid site amount firstly increased, and then kept almost constant. Nevertheless, 650 nm ZSM-5 crystals attaching small particles exhibit large external surface area and strong acidity. The catalytic stability and the liquid hydrocarbon yield decreased with increasing crystal size. The sample with a crystal size of 70 nm shows a catalytic lifetime of 96 h and a gasoline yield of 30.8%. The large external surface area and relatively strong acidity endow the sample with a crystal size of 650 nm also has a catalytic lifetime of 91 h, indicating that synthesis of large ZSM-5 crystals with small crystallites adhered to their surface could be a potential way to improve the catalytic performance.

Structural features of core–shell zeolite–zeolite composite and its performance for methanol conversion into gasoline and diesel

Abstract

One-pot hydrothermal synthesis of nanostructured ZrAPSO-34 powder: Effect of Zr-loading on physicochemical properties and catalytic performance in conversion of methanol to ethylene and propylene

Nanostructured ZrAPSO-34 catalyst was successfully synthesized via hydrothermal method and Zr isomorphously was substituted into the framework of SAPO-34. The effect of various Zr loadings on the physicochemical properties and catalytic performance was investigated. The structure of the synthesized catalysts was characterized using XRD, FESEM, EDX, BET, FTIR, NH3-TPD and DR-UV-Vis techniques. For samples with low Zr content, relative crystallinity increased and intact CHA structure produced. However, by further Zr loading, relative crystallinity strongly reduced. Acidity results confirmed that Zr incorporation led to increase in both acid sites concentration and strength. Characterization results confirmed the successful incorporation of Zr into SAPO-34 framework. ZrAPSO-34 and SAPO-34 catalysts were applied in methanol to olefins reaction. The Zr incorporation and Zr content have significant effects on the lifetime and product selectivity. For the samples with low Zr content, catalytic lifetime was prolonged compared to the sample synthesized without metal. However by increasing Zr loading, it was reduced and methane selectivity was increased.

Coupling Conversion of 1-butylene and Methanol to Propylene over Superfine HZSM-5 Catalysts

Superfine HZSM-5 zeolites were synthesized by different methods, and their catalytic performance for the coupling conversion of methanol and 1-butylene to propylene was investigated. In addition, these catalysts were characterized by XRD, SEM, N2 isothermal adsorption-desorption, and NH3-TPD. Z5-A catalyst showed the highest reactivity among these catalysts and could keep good stability, due to its superfine particle size, large surface area and proper acidity.

Methanol Conversion to Propylene over Mo-HZSM-5 Zeolite

A series of Mo-ZSM-5 zeolites have been synthesized by in site hydrothermal method and their catalytic performance for methanol conversion to propylene was tested in a fixed bed reaction at WHSV=4 h-1, pressure of 1 atm, and MeOH/H2O (mol) ratio of 1. The effect of Mo and Al content on the structure and acidity of Mo-ZSM-5 zeolites were characterized by nitrogen adsorption and NH3-TPD. The results showed that Mo incorporation gradually decreased the BET surface area and weaken the strong acidity on the surface of the zeolites. At 470 °C, the maximum selectivity of propylene and the P/E (Propylene to Ethane) ratio were achieved 45.04 % and 7.30, which were higher than those over Mo free HZSM-5 by 4.12% and 3.47, respectively. Mo-ZSM-5 zeolites are promising catalysts for methanol conversion to propylene with a high P/E.

Effect of calcination temperature of starch-modified silica on the performance of silica supported Cu catalyst in methanol conversion

A series of starch-modified SiO2 (SSi-temp) were obtained by calcining the extrudate of SiO2 and starch at different temperatures and used as the support to prepare Cu catalysts (Cu/SSi-temp, 10%) by the impregnation method. The Cu catalysts were characterized by N2 sorption, FT-IR, TG, XRD, SEM and H2-TPR; their catalytic performance in methanol conversion was investigated in a fixed bed reactor. The results indicated that starch can reduce the removal rate of silanol groups (Si-OH) from the surface of the support during calcination and the surface silanol groups are beneficial to the dispersion of Cu species. The calcination temperature of starch-modified SiO2 exhibits a significant influence on the surface silanol (Si-OH) concentration, the surface area and porous structure of the support; as a result, it may be used to adjust the size of supported CuO crystal grains and dispersion of Cu species, which determine the performance of the silica supported Cu catalysts in methanol conversion.

Improvement of light olefins selectivity and catalyst lifetime in MTO reaction; using Ni and Mg-modified SAPO-34 synthesized by combination of two templates

SAPO-34 catalysts were synthesized by the hydrothermal method using morpholine and/or TEAOH templates. The sample prepared by the combination of TEAOH and morpholine exhibited more crystallinity and smaller particle size. Furthermore, SAPO-34 was modified with Ni and Mg to improve its performance for conversion of methanol to olefin. These catalysts were characterized by XRD, SEM, EDX, BET, FTIR and NH 3-TPD techniques. The catalytic performance of catalysts was studied in MTO reaction at 673 K and atmospheric pressure by a feed WHSV of 8.7 h −1 in a fixed bed reactor. The modified catalysts showed higher selectivity to light olefins and longer lifetime. NiAPSO-34 catalyst showed the best performance; the yield of ethylene and propylene was determined to be 94 wt.% with 100% methanol conversion.

Hydrogen Production by Steam Reforming of Methanol over a Ag/ZnO One Dimensional Catalyst

One dimensional (1-D) and three dimensional (3-D) ZnO were growth by a hydrothermal method. ZnO 1-D was employed as a support for silver nanoparticles in order to design a new catalyst and used on the steam reforming of methanol (SRM) reaction for H2 production. The catalytic activity of the Ag/ZnO sample with low content of Ag showed better performance on the SRM reaction than on high silver loading catalyst. So, the sample with small Ag particle size showed best performance in methanol conversion than catalyst with big Ag particle size, this finding could be attributed to the high ZnO/Ag ratio. According to results of SEM and TEM techniques the catalytic activity: methanol conversion, H2 and low CO production observed on the Ag/ZnO 1-D catalyst occurs in the edge sites rather than the rim sites. The role of Ag is to accept the hydrogen to be released to the gas phase. In addition, the 1.5Ag/ZnO 1-D catalyst showed good stability during the reaction.

Methanol conversion over acid solid catalysts

A molecular sieve SAPO-34 with high density of strong acid sites was synthesized and its performance in methanol conversion was compared with the performances of ZSM-5, mordenite and beta commercial zeolites. Each catalyst was characterized by X-ray diffraction, X-ray fluorescence, textural analysis (BET method), and temperature programmed desorption of ammonia. The effects of temperature and time of reaction on methanol conversion were evaluated. Among the studied catalysts, SAPO-34 showed the highest initial selectivity to C 2 and C 3 compounds at 450 °C; however, it seems that the high density of strong acid sites of SAPO-34 resulted in an extremely fast deactivation of these sites, giving insignificant light olefins production after 1.5 h of reaction and turning the catalyst highly selective to dimethyl ether. Mordenite showed high selectivity towards C 2 and C 3 compounds at low temperatures, but underwent fast deactivation of its strong acid sites at high temperatures. ZSM-5 and beta zeolites were much more stable and also selective towards C 2 and C 3 compounds, proportionally to their densities of strong acid sites.

Preparation of Cu/ZnO for Fabrication of a Micro Methanol Reformer

Three synthesis procedures of Cu/ZnO catalyst for steam reforming of methanol were tested for loading in a micro reactor. The best procedure that resulted in the strong adhesion to the wafer was determined out of the tested procedures. The molecular structure of the synthesized catalyst was examined by XRD and its performance in methanol conversion was measured. A micro fabrication method that incorporates the catalyst loading and micro structure processing was developed. A MEMS methanol steam reformer was built by this process and the completed device resulted in methanol conversion of 93%.

Methanol Oxidative Dehydrogenation in a Catalytic Packed-Bed Membrane Reactor: Experiments and Model

Abstract Methanol oxidative dehydrogenation to formaldehyde over a Fe–Mo oxide catalyst was studied experimentally in three reactor configurations: the conventional fixed-bed reactor (FBR) and the packed-bed membrane reactor (PBMR), with either methanol (PBMR-M) or oxygen (PBMR-O) as the permeating component. The kinetics of methanol and formaldehyde partial oxidation reactions were determined independently from FBR experiments. A steady state plug-flow PBMR model, utilizing these kinetics and no adjustable parameters, fit the experiments accurately. It is shown experimentally and in accordance with the model that for given overall feed conditions, the reactor performance for methanol conversion and formaldehyde yield is in the order PBMR-M