Methanol Synthesis Catalyst Research Articles

Crystallographic Orientation Dependence of Surface Segregation and Alloying on PdCu Catalysts for CO2 Hydrogenation.

The influence of the crystallographic orientation on surface segregation and alloy formation in model PdCu methanol synthesis catalysts was investigated in situ using near-ambient pressure X-ray photoelectron spectroscopy under CO2 hydrogenation conditions. Combined with scanning tunneling microscopy and density functional theory calculations, the study showed that submonolayers of Pd undergo spontaneous alloy formation on Cu(110) and Cu(100) surfaces in vacuum, whereas they do not form an alloy on Cu(111). Upon heating in H2, inward diffusion of Pd into the Cu lattice is favored, facilitating alloying on all Cu surfaces. Under CO2 hydrogenation reaction conditions, the alloying trend becomes stronger, promoted by the reaction intermediate HCOO*, especially on Pd/Cu(110). This work demonstrates that surface alloying may be a key factor in the enhancement of the catalytic activity of PdCu catalysts as compared to their monometallic counterparts. Furthermore, it sheds light on the hydrogen activation mechanism during catalytic hydrogenation on copper-based catalysts.

Methanol Synthesis with Steel Mill Gases: Performance Investigations in an On‐Site Technical Center

AbstractAn on‐site laboratory with direct access to cleaned and conditioned steel mill gases was recently put into operation. The long‐term performance and stability of Clariant's MegaMax®800 methanol synthesis catalyst utilizing steel mill gases is currently being investigated. First test results revealed that in order to investigate deactivation mechanisms arising from particular properties of the cleaned steel mill gases, the overlaying effect of thermal deactivation of the catalyst has to be minimized.

MCM-41-supported tungstophosphoric acid as an acid function for dimethyl ether synthesis from CO2 hydrogenation

We mixed an MCM-41-supported tungstophosphoric acid (TPA) catalyst with a commercial CuO–ZnO–Al2O3 methanol synthesis catalyst (MSC) and optimized the mixing ratios/reaction conditions towards high performance in dimethyl ether (DME) synthesis by CO2 hydrogenation. First, a series of TPA/MCM-41 catalysts were synthesized at a TPA loading of 30, 40, 60, and 80 wt% and characterized by combining various techniques. The results of X-ray fluorescence spectroscopy confirmed the loading of stoichiometric TPA amounts in each TPA/MCM-41 catalyst, while the N2 adsorption-desorption measurements and the scanning transmission electron microscopy images were showing the decoration of MCM-41 pores with TPA clusters. X-ray diffraction and infrared spectroscopy results identified some structural distortions in TPA clusters especially at relatively low loadings and the results of temperature programmed desorption of ammonia measurements quantified the consequences of these changes in TPA structure on the acid properties. The optimized TPA loading in TPA/MCM-41 was 60 wt% with CuO–ZnO–Al2O3:TPA/MCM-41 = 4:1 at 40 000 mL CO2 gcat−1 h−1 and H2:CO2 = 3:1 at 250 °C and 45 bar. At these conditions, the rate was 1551.5 gDME kgcat−1 h−1, to the best of our knowledge, the highest rate for the direct DME synthesis from CO2 hydrogenation in a single-pass reactor. This performance was originated from the high density of acid sites in TPA/MCM-41 owing to exceptionally high surface area of MCM-41 offering a monolayer dispersion of TPA even at a TPA loading of 60 wt%. These results present a broad potential of TPA/MCM-41 as an acid function in the catalyst mixture for the single-pass DME synthesis from CO2 hydrogenation, especially if used together with an MSC specifically designed for CO2 hydrogenation.

Effects of magnesium and chromium addition on stability, activity and structure of copper-based methanol synthesis catalysts

Cu/ZnO/Al2O3-based catalysts for methanol synthesis are prepared through co-precipitation by addition of Mg and Cr. Precursors are characterized by XRD and Air-TGA. Catalysts, calcined at 450 °C, are examined by XRD and BET. Reduction characteristics of the catalysts are analyzed via H2-TPR and H2-TGA. Surface acidity of the catalysts is determined by TPAD-TGA. Addition of Mg and Cr causes formation of smaller CuO crystallite size, and increases surface area of catalysts by improving dispersion of CuO. Cr also improves stability of the catalysts against ambient conditions and prolongs their shelf life. The catalyst containing 6.4 mol % Cr has a methanol selectivity of 83.5% and a catalytic activity of 14.2 g methanol production which is the highest among other synthesized catalysts. High Cr loadings (32 mol %) reduce the catalytic activity. Cr containing catalysts continue to produce the highest amounts of methanol as compared with the catalysts without Cr where Cr prevents deactivation and sintering.

Relations between Surface Oxygen Vacancies and Activity of Methanol Formation from CO2 Hydrogenation over In2O3 Surfaces

As a promising catalyst for methanol synthesis from CO2 hydrogenation, In2O3 has attracted considerable interest due to its high methanol selectivity. Understanding the structure–activity relations...

Influence of Reaction Temperature on CO2-to-methanol Hydrogenation over MZrOx (M = Al, Mn, Cu, Zn, Ga, and In)

Abstract To open up the possibility of synthesizing useful substances from CO2, we have developed new catalysts that hydrogenate CO2 to methanol with high yield at 300 °C and higher. In this study, methanol synthesis via CO2 hydrogenation at 250–350 °C and 10 bar was investigated using Zr-based metal oxide catalysts, MZrOx (M = Al, Mn, Cu, Zn, Ga, and In). The different metals (M) determined the suitable reaction temperature wherein the maximum yield of methanol was obtained. CuZrOx was a suitable catalyst for low-temperature methanol synthesis because the yield decreased with increasing reaction temperature from 250 °C to 350 °C. In contrast, ZnZrOx, GaZrOx, and InZrOx were suitable for methanol synthesis at 300 °C and higher. In particular, ZnZrOx afforded the highest yield of methanol (60 mLSTP h−1 g−1 at 300 °C) among the prepared MZrOx catalysts.

Inverse ZnO/Cu catalysts for methanol synthesis from CO2 hydrogenation

A series of inverse ZnO/Cu catalysts were prepared with varied Zn/Cu ratios using a microemulsion method. The catalysts were tested for CO2 hydrogenation to methanol and the structure was characterized by nitrogen physisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), Scanning electron microscope (SEM), H2 temperature-programmed reduction (H2-TPR) and H2 temperature-programmed desorption (H2-TPD). On the inverse samples, less amount of highly dispersed Cu was observed than that of the conventional Cu/ZnO catalysts. Thus, the inverse ZnO/Cu catalysts showed a lower CO selectivity and a higher methanol selectivity. CuZn alloy was formed in the samples, in which ZnO/Cu(4:6) had the most amount of the CuZn alloy. A linear relationship between the methanol yield and the CuZn alloy content can be found for the ZnO/Cu catalysts. Among all the catalysts, ZnO/Cu(4:6) exhibited the highest CH3OH yield (2.8 mmol g−1 h−1) at 2.0 MPa and 250 °C, much higher than the conventional Cu/ZnO catalyst with the same composition. Moreover, microemulsion method is a very effective method to tune particle size of the catalysts.

Boosting the synthesis of value-added aromatics directly from syngas via a Cr2O3 and Ga doped zeolite capsule catalyst.

Even though the transformation of syngas into aromatics has been realized via a methanol-mediated tandem process, the low product yield is still the bottleneck, limiting the industrial application of this technology. Herein, a tailor-made zeolite capsule catalyst with Ga doping and SiO2 coating was combined with the methanol synthesis catalyst Cr2O3 to boost the synthesis of value-added aromatics, especially para-xylene, from syngas. Multiple characterization studies, control experiments, and density functional theory (DFT) calculation results clarified that Ga doped zeolites with strong CO adsorption capability facilitated the transformation of the reaction intermediate methanol by optimizing the first C–C coupling step under a high-pressure CO atmosphere, thereby driving the reaction forward for aromatics synthesis. This work not only reveals the synergistic catalytic network in the tandem process but also sheds new light on principles for the rational design of a catalyst in terms of oriented conversion of syngas.

Improved methanol synthesis performance of Cu/ZnO/Al2O3 catalyst by controlling its precursor structure

Methanol, a versatile chemical, fuel additive and potential H2 carrier, has attracted great attention. Despite of the wide industrialization, improvement of Cu-based methanol-synthesis catalysts is highly anticipated. Accordingly, a series of Cu/ZnO/Al2O3 with designed precursor structures were prepared, and its structure–function relationship was investigated to make progress on this area. Results showed the catalyst derived from highly zinc-substituted malachite demonstrated the best catalytic performance in this work. It was found that the well-behaved catalyst possessed relatively high Cu specific surface area and exposed Cu concentration, and the well Cu/ZnO synergy. CuZn alloy was found by In-situ XRD tests, and its effect on the catalyst's thermostability was discussed. Fractional precipitation, which facilitated the Cu2+ substitution by Zn2+ in malachite lattice, could be an efficient preparation method of the Cu/ZnO/Al2O3 catalyst.

Unravelling the Structural Modification (Meso-Nano-) of Cu/ZnO-Al2O3 Catalysts for Methanol Synthesis by the Residual NaNO3 in Hydroxycarbonate Precursors

The effects of residual NaNO3 on the modification of Cu/ZnO-Al2O3 catalysts have been extensively documented, but the modification mechanism is so far unclear. This work studies in detail the influence of the residual sodium nitrate present in the hydroxycarbonate precursors on their decomposition during calcination and how it affects to the formation and configuration of the final active sites of the Cu/ZnO-Al2O3 catalysts. Different samples with varying sodium content after washing (from 0.01 to 7.3 wt%) were prepared and studied in detail after calcination and reduction steps. The results of this work demonstrated that NaNO3 affects the decomposition mechanism of the hydroxycarbonate precursors during calcination and produces its decarbonation at low temperature. The enhancement of the decarbonation by NaNO3 leads to segregation and crystallization of CuO and ZnO with loss of mesostructure and surface area in the calcined catalysts. The loss of mesostructure in calcined catalysts affects the subsequent reduction step, decreasing the reducibility and damaging the nanostructure of the reduced catalysts forming large Cu particles in poor contact with ZnOx that results in a significant decrease in the intrinsic activity of the copper active sites for methanol synthesis.

Inverse ZrO2/Cu as a highly efficient methanol synthesis catalyst from CO2 hydrogenation

Enhancing the intrinsic activity and space time yield of Cu based heterogeneous methanol synthesis catalysts through CO2 hydrogenation is one of the major topics in CO2 conversion into value-added liquid fuels and chemicals. Here we report inverse ZrO2/Cu catalysts with a tunable Zr/Cu ratio have been prepared via an oxalate co-precipitation method, showing excellent performance for CO2 hydrogenation to methanol. Under optimal condition, the catalyst composed by 10% of ZrO2 supported over 90% of Cu exhibits the highest mass-specific methanol formation rate of 524 gMeOHkgcat−1h−1 at 220 °C, 3.3 times higher than the activity of traditional Cu/ZrO2 catalysts (159 gMeOHkgcat−1h−1). In situ XRD-PDF, XAFS and AP-XPS structural studies reveal that the inverse ZrO2/Cu catalysts are composed of islands of partially reduced 1–2 nm amorphous ZrO2 supported over metallic Cu particles. The ZrO2 islands are highly active for the CO2 activation. Meanwhile, an intermediate of formate adsorbed on the Cu at 1350 cm−1 is discovered by the in situ DRIFTS. This formate intermediate exhibits fast hydrogenation conversion to methoxy. The activation of CO2 and hydrogenation of all the surface oxygenate intermediates are significantly accelerated over the inverse ZrO2/Cu configuration, accounting for the excellent methanol formation activity observed.

Formation of Effective Copper-Based Catalysts of Methanol Synthesis

The regularities of formation of the composition and structure of a highly efficient catalyst for methanol synthesis have been revealed. The catalyst was obtained by thermal treatment of the combined CuZnAl(Cr) hydroxocarbonate followed by the reductive activation of the anion-modified zinc oxide precursor. The composition and structure of hydroxocarbonate are determined by the nature of components and their ratio. The thermal decomposition of hydroxocarbonates at 550–650 K formed the oxide catalyst; at higher temperatures, the product was an inactive mixture of oxides. The oxide catalyst is mixed zinc oxide containing the Cu2+ and Al or Cr3+ cations and residual (СО3)2– and ОН– anions, i.e., the anion-modified oxide.

Interplay between carbon dioxide enrichment and zinc oxide promotion of copper catalysts in methanol synthesis

Methanol synthesis over Cu/ZnO/Al2O3 is a key industrial reaction. Typically, a ZnOx promoter and CO2 enrichment of the feed are applied to maximize the syngas conversion. However, understanding the effects of these additives on the performance of the Cu catalysts is obscured by the strong interaction between the ZnOx promoter and oxidic supports. Here, we use Cu nanoparticles on graphitic support to study the interplay between CO2 concentration and ZnOx promotion. CO2 enrichment enhanced the activity with an optimum at 3 vol% in the feed, but only if the ZnOx promoter was present, demonstrating the intricate interaction between the two. Interestingly, not only the activity but also the methanol selectivity was enhanced by CO2 enrichment, and even further by the addition of ZnOx. Understanding not only the role of the individual components, but also the interaction between them, is important to design catalysts for processes with more flexible feed compositions.

Effect of lanthanum group promoters on Cu/(mixture of ZnO and Zn-Al-spinnel-oxides) catalyst for methanol synthesis by hydrogenation of CO and CO2 mixtures

Improvement of copper-based catalyst activity as an industrial catalyst for methanol production from synthesis gas has a great impact on the economy and environmental aspects of this process. CO2 utilization in this research will improve the sustainability of the methanol process using the science of nanocatalysts. For this purpose, a new mixture of ZnO and Zn-Al-Oxides spinel with a Zn/Al ratio of 3 was developed and optimized. This support was synthesized by the co-precipitation method and calcined at temperatures of 110, 300, 500, 700, and 900 °C. The results show that the best calcination temperature is 500 °C (coded as ZA500). Then, Cu-X/ZA500 (X = empty, La, Ce, or Sm) catalysts were synthesized by the co-precipitation-deposition method. Developed supports and catalysts were characterized by N2-physisorption, H2-TPR, XRD, and HRTEM, XPS, TGA, H2-TPD, EXAFS, and XANES techniques. The results show that adding a small amount of CO2 to the syngas (H2 & CO) improves the catalyst activity. When a mixture of CO/CO2 was used, a comparison of catalysts shows that Cu/ZA500 has the highest CO2, CO, and carbon conversions among all samples at 250 °C that prove the role of support and its interaction with copper active sites. Adding La, Ce, or Sm to the Cu-X/ZA500 catalysts enhanced the CO2 conversion in comparison to Cu/ZnO/Al2O3 as a reference catalyst. It was found that the La promoter can enhance the sintering resistivity of the copper catalyst. Cu-La/ZA500 has the highest CO2 conversion of around 25% with methanol selectivity of 54.0% at 250 °C and 40 bar for CO2 hydrogenation (without CO).

Characterization of oxide-supported Cu by infrared measurements on adsorbed CO

Infrared spectroscopy on CO chemisorbed on Raney Cu and materials with Cu dispersed as nanoparticles on oxide supports was used to evaluate support effects on the Cu surface properties. The C-O frequency (νC-O) is sensitive to the charge on the adsorption site with νC-O being high on Cu+, intermediate on Cu0, and low on Cu−, whereby this method can probe the charging state of the Cu surface. The Raney Cu reference demonstrates the complex analysis of the IR band intensity, which can be susceptible to dipole coupling. This means that the most intense IR bands may be higher frequency bands strengthened by such coupling effects rather than the bands arising from the most abundant sites. The νC-O of the major band attributable to CO adsorbed on the metallic surface follows the order: Cu/SiO2 > Raney Cu > Cu/Al2O3 > Cu/TiO2. Given the charge-frequency relationship these support-dependent frequency shifts are attributed to changes in the charging of the Cu surface caused by support effects. The Cu surface is more electron deficient for Cu/SiO2 and electron enriched for Cu/TiO2. For the Cu/ZnO(/Al2O3) samples, which are important as industrial methanol synthesis catalysts, band assignments are complicated by a low νC-O on Cu+ sites connected to the ZnO matrix. However, Cu/ZnO(/Al2O3) has a spectral feature at 2065-68 cm−1, which is a lower frequency than observed in the Cu single crystal studies in the literature and thus indicative of a negative charging of the Cu surface in such systems. Experiments with co-adsorption of CO and electron-withdrawing formate on Cu/ZnO and Cu/SiO2 show that νC-O in the adsorbed CO shifts upwards with increasing HCOO coverage. This illustrates that the surface charge is donated to the electron-withdrawing formate adsorbate, and as a result co-adsorbed CO experiences a more charge depleted Cu surface that yields higher νC-O. The support-dependent surface charging may thus affect the interaction with adsorbates on the metal surface and thereby impact the catalytic properties of the Cu surface. Dilution of the samples in KBr, which has been used in many studies in the literature, had pronounced effects on the spectra. The presence of KBr leads to an increase in νC-O indicative of an electron depleted surface attributed to transfer of electron-withdrawing bromine species from KBr to the sample.

Tuning surface-interface structures of ZrO2 supported copper catalysts by in situ introduction of indium to promote CO2 hydrogenation to methanol

Currently, highly efficient catalytic CO2 hydrogenation to produce methanol is attracting intensive attention. However, constructing high-performance catalysts for methanol synthesis that can be operated under mild reaction conditions is a challenging task. In this work, a series of indium-doped ZrO2 supported copper-based catalysts for CO2 hydrogenation were constructed via one-pot hydrogen bubble-assisted approach. It was manifested that the in situ introduction of indium facilitated the generation of interfacial defects in the form of Zr-Vo-In3+ structure (Vo: oxygen vacancy) and interfacial Cu+ sites, as well as surface basic sites originating from In-O pairs, and the catalytic performance of as-constructed In-doped Cu/ZrO2 catalysts could be efficiently promoted by tuning the indium content. Specifically, the Cu-based catalyst bearing the indium content of 4.0 wt% afforded the quite high space-time yield of methanol (0.398 gMeOH h−1·gcat−1) at 270 °C, while the one with the indium content of 8.0 wt% yielded an increased methanol selectivity by 1.8 times at 250 °C, compared with undoped one. Combining the structural characterizations with catalytic results, it was found that surface medium-strength and strong basic sites together with the contribution from interfacial defective oxygen vacancies and Cu+ sites played key promotional roles on the synthesis of methanol. This finding enables us to design new high-performance Cu-based catalysts for CO2 hydrogenation by finely turning their surface-interface structures.

FORMULASI KATALIS BIFUNGSIONAL SINTESA DME SATU TAHAP

This research is aiming to formulate the most appropriate catalyst which is expected to be able to directthe reaction to form Dimethyl Ether (DME) in direct synthesis process using dual catalyst. It iscommonly known that DME can be formulated from synthetic gasses reaction, H2 and CO. Theprocess might be gone through indirect synthesis, methanol synthesis and dehydration, or directsynthesis in which both rections take place in one reactor. Both processes, indirect or direct synthesis,each would be needed the right catalyst. Dual catalyst is prepared by mixing physically methanolsynthesis catalyst and methanol dehydration to form DME.As methanol dehydration catalyst, we makeuse of HZSM-5 with Si/Al ratio of 25 and 90. This HZSM-5 is firstly calcined for 6 hours at 500°C. Thetemperature is raised to 500°C from ambient with pace of 5°C/min. The methanol synthesis catalyst isbased on CuZnAl, made by copresipitation method from Cu(NO3)2.3H2O; Zn(NO3)2.4H2O andAl(NO3)2.9H2O. The catalyst was then calcined at 350 ° C for 6 hours, then reduced by hydrogen 10 ml /minute and nitrogen 90 ml / min at 240 ° C, atmospheric pressure for 10 hours to remove the Ocomponent in the catalyst. The catalyst that has been prepared is CuZnAl with a ratio of 4: 3: 1; 5: 3: 1and 6: 3: 1. The ratio of the two catalysts is 2: 1 for Cu / Zn / Al2O3: HZSM-5. The catalytic activity test iscarried out using a continuous tubular fixed-bed microactivity reactor. The reaction is carried out at apressure between 3 - 4 MPa and a temperature in the range of 200 - 300 ° C. T The flow rate of thereactant gas is controlled by a mass flow controller, with a mass of 1 g of catalyst. Through the catalyticactivity test, the best methanol synthesis was given by CuZnAl catalyst with a 5: 3: 1 molar ratio, whichresulted in a CO conversion of 19.66% greater than the commercial catalyst of CZA-Sudchemie of15.62%. As for dehydration of methanol, the best result was given by Sudchemie-ZSM-5 catalyst withSi /Al 25 ratio resulting in higher DME concentration (0.90%) than Si /Al 90 ratio (0.45%).Keywords : direct synthesis, methanol synthesis, methanol dehydration, dual catalyst, CO conversion

Niobium-based solid acids in combination with a methanol synthesis catalyst for the direct production of dimethyl ether from synthesis gas

The production of dimethyl ether (DME) as compared to methanol from synthesis gas allows for increased conversions in a single pass. A challenge in this process is the combination of methanol synthesis and dehydration functionalities in a single catalyst without mutual negative interference of their performances. Here, we studied the use of hydrated niobium pentoxide (Nb2O5·nH2O) and niobium phosphate (NbOPO4) in combination with a copper-based methanol synthesis catalyst in the direct synthesis of DME, while gamma-alumina (γ-Al2O3) was used as a reference material. The three solid acids combined with the copper-based catalyst proved active and selective in the production of DME, however all of them showed some degree of deactivation throughout the reaction. Characterization of the used catalysts pointed out that while the γ-Al2O3-based mixture deactivated most likely due to coke deposition on the alumina and structural changes in the methanol synthesis catalysts, the Nb2O5·nH2O and NbOPO4-based catalysts lost activity probably as a result of copper migration from the methanol synthesis catalyst to the acid component. In view of the high volume-based activity of the Nb-based solid acids it is concluded that these are promising components for the direct catalytic conversion of synthesis gas to DME.

Supported indium oxide catalyst and process for methanol synthesis using the same

Supported indium oxide catalyst and process for methanol synthesis using the same

Atomically dispersed Ptn+ species as highly active sites in Pt/In2O3 catalysts for methanol synthesis from CO2 hydrogenation

Hydrogenation of CO2 into methanol using the H2 produced from renewable energy is a promising way for carbon capture and utilization. Therefore, the methanol synthesis catalysts with high methanol selectivity are highly desired. In this work, we found that the methanol selectivity of In2O3 catalyst can be significantly enhanced by introducing a small amount of Pt. Methanol selectivity can be increased from 72.2% (In2O3) to 91.1% (0.58 wt.% Pt/In2O3) at 220 °C. The introduced Pt atoms are doped into the In2O3, forming atomically dispersed Ptn+ species, most of which are stable under working conditions. It is proposed that the atomically dispersed Ptn+ species are responsible for the enhanced methanol selectivity, while Pt nanoparticles on In2O3 mainly boost the reverse water-gas shift reaction (CO2 + H2 → CO + H2O).