Catalyst For Dimethyl Ether Synthesis Research Articles

Dehydration of methanol over Nordstrandite based catalysts for dimethyl ether synthesis

This study focused on the investigation of Nordstrandite as a catalyst for dehydration of methanol to dimethyl ether synthesis. The structure phase of Nordstrandite has been changed to boehmite and γ-Al 2O 3 in sequence via calcinations at various temperatures. Moreover, the properties of the samples have been varied significantly with heat treatment. The number of acid sites of Nordstrandite was much higher than the other aluminas. However, the catalytic activity of Nordstrandite was comparable to the other catalysts with fewer amounts of acid sites. This means that structure phase is one of the most important factors for catalytic performance in this reaction.

Effect of surfactant on structure and performance of catalysts for DME synthesis in slurry bed

The Cu–Zn–Al slurry catalysts prepared via modified sol–emulsion–gel method by adding different water-soluble surfactants were studied for CO hydrogenation to produce dimethyl ether (DME) in slurry bed reactor. The results indicated that the catalyst adding Tween80 or PEG600 had higher activity than the catalyst with the PVP additive. All the catalysts had good stability. X-ray diffraction (XRD) results showed that Cu and Cu 2O existed in the pre-reduced Cu–Zn–Al catalysts, while ZnO did not appear. Nitrogen adsorption studies showed that the catalyst prepared with the additives of PEG600 or Tween80 was mesoporous structure with higher specific surface area compared with the one prepared with the additive of PVP. X-ray photoelectron spectroscopy (XPS) results indicated that the Cu/Zn ratio on the surface of all catalysts increased after subject to reduction and reaction. The morphology and size of the catalyst particles could be adjusted by adding water-soluble surfactants.

Attrition resistant catalyst for dimethyl ether synthesis in fluidized-bed reactor

Fluidized-bed reactor is a candidate for dimethyl ether (DME) synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0∼20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller (BET), X-ray powder diffraction (XRD) and temperature programmed reduction (TPR).

Study on deactivation of hybrid catalyst for dimethyl ether synthesis in slurry reactor

Deactivation of composite catalyst for one-step dimethyl ether (DME) synthesis in slurry reactor was studied under reaction conditions of 260°C and 5.0 MPa. It was found that instability of Cu-based methanol synthesis catalyst led to rapid deactivation of the composite catalyst. Deactivation rate of the Cu-based catalyst in slurry reactor was compared with that in fixed-bed reactor. The results indicated that harmfulness of water, which is formed in the synthesis of DME, caused the Cu-based catalyst to deactivate at a high rate in slurry reactor. Techniques of TPR, XRD, and SEM-EDS were used to characterize the reduction behaviors, crystal structures, and surface properties of the catalyst. The results showed that carbon deposition and grain growth of Cu were important reasons for the rapid deactivation of the Cu-based catalyst, and no obvious metal loss of Cu was found.

Cu–Zn–Cr2O3 Catalysts for Dimethyl Ether Synthesis: Structure and Activity Relationship

The CuO dispersed on ZnCr2O4 catalysts derived from Cu–Zn–Cr hydrotalcite like layered double hydroxide precursors with varying Zn/Cr ratios have been synthesized, characterized by BET—Surface area, X-ray diffraction (XRD), temperature programmed reduction (TPR), electron spin resonance (ESR), N2O titrations and the activities were evaluated for single step dimethyl ether (STD) synthesis from syngas. It is observed that the copper species were in highly dispersed state over Cu–ZnO–Cr2O3 at high Zn/Cr ratios while the copper cluster were present at low Zn/Cr ratios. The ESR analysis revealed signals due to isolated Cu2+ at high Zn/Cr ratios and clustered Cu2+ at low Zn/Cr ratio in fresh catalysts and only Cr3+ species in used catalysts. The TPR results indicated that the reduction peak shifted to high temperatures with an increase in chromium content due to large copper crystallites, which was supported by XRD analysis. The conversion of syngas to DME was well correlated with the copper metal surface areas, indicating that STD synthesis can be controlled by methanol synthesis rate.

Effects of ZrO 2 on the Performance of CuO-ZnO-Al 2O 3/HZSM-5 Catalyst for Dimethyl Ether Synthesis from CO 2 Hydrogenation

A series of composite catalysts were prepared by the wet mixing method, and the mass ratio of CuO-ZnO-Al 2O 3-ZrO 2 component to HZSM-5 zeolite (molar ratio of SiO 2 to Al 2O 3 being 25) was 2:1. The CuO-ZnO-Al 2O 3-ZrO 2 (CuO/ZnO/Al 2O 3=3/6/1 by weight) component was prepared by a modified ‘two-step’ co-precipitation method. The effects of ZrO 2 on the performance of CuO-ZnO-Al 2O 3/HZSM-5 catalyst for dimethyl ether synthesis from CO 2 hydrogenation were investigated. It was found that ZrO 2 improved the properties of CuO-ZnO-Al 2O 3/HZSM-5 as a structural promoter.

Modification of Cu-based methanol synthesis catalyst for dimethyl ether synthesis from syngas in slurry phase

The Cu-based methanol synthesis catalyst was modified with Mn to improve its activity and stability for dimethyl ether (DME) synthesis from syngas in slurry phase. Mn was added by impregnating co-precipitated CuZnAl catalyst with aqueous solution of manganese nitrate (Mn/CuZnAl) or co-precipitation of the nitrates of Cu, Zn, Al and Mn (CuZnAlMn). The catalyst characterizations by H 2-TPD and XRD showed that CuO in CuZnAlMn catalyst was easily reduced, and Cu particles were well dispersed. XRD results indicated that the eutectic CuZn existed only over CuZnAlMn catalyst, and the promoter MnO did not appear over both of Mn/CuZnAl and CuZnAlMn catalysts. In DME synthesis reaction, it was found that Mn-modified CuZnAl catalyst have high activity and good stability. The proper content of Al and Zn can enhance the DME yield.

Surface acidity and the dehydration of methanol to dimethyl ether

Microcalorimetry and infrared spectroscopy for ammonia adsorption have been used to study the nature, strength and number of surface acid sites of H-ZSM-5, steam de-aluminated H-Y zeolite (SDY), γ-Al 2O 3 and Ti(SO 4) 2/γ-Al 2O 3 catalysts for the dehydration of methanol to dimethyl ether (DME). The conversion of isopropanol was also performed as a probe reaction to characterize the acid strength. The H-ZSM-5 and SDY possessed strong Brønsted acidity and exhibited high activity for the conversion of methanol to DME at relatively low temperatures, but they did not seem to be suitable as the dehydration component of the hybrid catalyst for the direct synthesis of DME from syngas since the two zeolite catalysts produced hydrocarbons and coke from methanol at temperatures higher than 513 K. The coke was serious over the two zeolite catalysts at 553 K. The dehydration of methanol to DME on γ-Al 2O 3 was found to be low at the temperatures below 573 K though the DME selectivity is high. The modification of the γ-Al 2O 3 by Ti(SO 4) 2 greatly enhanced the surface Brønsted acidity and also the reaction activity for the dehydration of methanol to DME. In addition, no detectable hydrocarbon by-products and coke were formed on the Ti(SO 4) 2/γ-Al 2O 3 catalyst in the temperature range of 513–593 K. Thus, the Brønsted acid sites with suitable strength may be responsible for the effective conversion of methanol to DME with high stability.

Effect of the Addition of Manganese and Zinc on the Properties of Copper-Based Catalyst for the Synthesis of Syngas to Dimethyl Ether

A series of copper-based catalysts supported on zeolite-Y were prepared through a coprecipitation impregnation method and used for the synthesis of dimethyl ether (DME) directly from synthesis gas (syngas) in a fixed-bed reactor. The conversion of CO and the selectivity of DME increased from 7.7% and 5.9% on Cu/zeolite-Y to 53.6 mol % and 63.5 mol % on Cu−Mn−Zn/zeolite-Y, respectively. The results of X-ray diffractometry (XRD), temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD) showed that the reducibility, dispersion, and acid properties of Cu/zeolite-Y were strongly dependent on the addition of manganese and zinc, which affected the “synergistic effect” of the consecutive methanol synthesis from syngas and the steps for its dehydration to DME. The higher activity of Cu-Mn-Zn/zeolite-Y catalyst for DME synthesis was due to the good synergistic effect of the catalyst.

A novel catalyst for DME synthesis from CO hydrogenation: 1. Activity, structure and surface properties

The effect of manganese on the dispersion, reduction behavior and active states of surfaces of γ-Al2O3 supported copper catalysts was investigated by X-ray powder diffraction (XRD), temperature-programmed reduction (TPR) and XPS technologies. The relationship between the area of metallic copper and the activity of dimethyl ether (DME) synthesis from CO/H2 was also investigated. The catalytic activity over Cu-MnOx/γ-Al2O3 catalyst for CO hydrogenation is higher than that of Cu/γ-Al2O3. The adding of manganese increases the dispersion of the supported copper oxide. For the CuO/γ-Al2O3 catalyst, there are two reducible copper oxide species; α- and β-peaks are attributed to the reduction of highly dispersed copper oxide species and bulk CuO species, respectively. For the CuO-MnOx/γ-Al2O3 catalyst, four reduction peaks are observed. The α-peak is attributed to the reduction of high dispersed copper oxide species; β-peak is ascribed to the reduction of bulk CuO; γ-peak is ascribed to the high-dispersed CuO interacting with Mn; and δ-peak is attributed to the reduction of the manganese oxide interacting with copper oxide. XPS results showed that Cu+ mostly existed on the working surface of the Cu-Mn/γ-Al2O3 catalysts. Cu promoted the catalytic activity with positive charge, which was formed by means of long path exchange function between CuOMn. These results indicate that there are synergistic interactions between the copper and manganese oxide, which are responsible for the high activity of CO hydrogenation.

Development of Cu/ZnO/Ai2O3 Catalyst for Dimethyl Ether Synthesis from CO-CO2-H2 Mixture.

The objective of this study is to develop a catalyst for direct synthesis of dimethyl ether ((CH 3 ) 2 O, DME) from a CO-CO 2 -H 2 mixture such as blast furnace gas. For this purpose, precipitated Cu-ZnO-X (X=Al 2 O 3 , Cr 2 O 3 , ZrO 2 or Ga 2 O 3 ) were systematically prepared by changing chemical composition and their catalytic activity was measured. For Cu-ZnO-Al 2 O 3 catalyst, compositional research was on two parameters, namely Cu/ZnO ratio (3/7-5/5) and content of Al 2 O 3 (0-33.0 mol%). The influence of each parameter was estimated by DME and MeOH yields for the same catalyst mass. Some Cu-ZnO-Al 2 O 3 catalysts synthesized DME more than MeOH, in which the DME activity was related to specific surface area and existence of broadened ZnO peaks in XRD patterns. In contrast, three other Cu-ZnO catalysts including another oxide (Cr 2 O 3 , ZrO 2 or Ga 2 O 3 ) synthesized only MeOH without DME. Content of Al 2 O 3 was more influential on DME synthesis than Cu/ZnO ratio. In conclusion, the most active composition of Cu-ZnO-Al 2 O 3 catalyst for DME synthesis was Cu/ZnO = 4/6 with 14.3 mol% Al 2 O 3 and interestingly this composition was included within the range of usual MeOH synthesis catalysts.