Effect of preparation method and CuO promotion in the conversion of ethanol into 1,3-butadiene over SiO₂-MgO catalysts

A DFT study of the aldol condensation reaction in the processing of ethanol to 1,3-butadiene on a MgO/SiO2 surface

The ETB process on different sites of MgO/SiO2.

The Importance of Thermal Treatment on Wet-Kneaded Silica-Magnesia Catalyst and Lebedev Ethanol-to-Butadiene Process

The Lebedev process, in which ethanol is catalytically converted into 1,3-butadiene, is an alternative process for the production of this commodity chemical. Silica-magnesia (SiO2-MgO) is a benchmark catalyst for the Lebedev process. Among the different preparation methods, the SiO2-MgO catalysts prepared by wet-kneading typically perform best owing to the surface magnesium silicates formed during wet-kneading. Although the thermal treatment is of pivotal importance as a last step in the catalyst preparation, the effect of the calcination temperature of the wet-kneaded SiO2-MgO on the Lebedev process has not been clarified yet. Here, we prepared and characterized in detail a series of wet-kneaded SiO2-MgO catalysts using varying calcination temperatures. We find that the thermal treatment largely influences the type of magnesium silicates, which have different catalytic properties. Our results suggest that the structurally ill-defined amorphous magnesium silicates and lizardite are responsible for the production of ethylene. Further, we argue that forsterite, which has been conventionally considered detrimental for the formation of ethylene, favors the formation of butadiene, especially when combined with stevensite.

High-throughput development of highly active catalyst system to convert bioethanol to 1,3-butadiene

The development of highly active catalysts for the conversion of ethanol to 1,3-butadiene using high-throughput catalyst preparation and evaluation systems.

Recent Advances in Catalysts for the Conversion of Ethanol to Butadiene

Butadiene is an important monomer for synthetic rubbers. Currently, the annual demand of ∼16 million tonnes is satisfied by butadiene produced as a byproduct of steam naphtha cracking where ethylene and propylene are the main products. The availability of large amounts of shale gas and condensates in the USA since about 2008 has led to a change in the cracker feed from naphtha to ethane and propane, affecting the amount of butadiene obtained. This has provided the impetus to look into direct processes for butadiene production. One option is the eco-friendly conversion of (bio) ethanol to butadiene (ETB). This process had been developed in the 1930s in the then Soviet Union. It was operated on a large scale in USA during World War II but has since been abandoned in favour of petroleum-based processes. The current trend, driven both by the availability of the raw material and ecological considerations, may make this process feasible again, particularly if the catalytic systems can be improved. This critical review discusses recent catalysts for the ETB process with special focus on the development since 2014, benchmarking them against earlier systems with a large database of operational experience.

Ethanol-to-butadiene: the reaction and its catalysts

Catalytic conversion of ethanol is a promising technology for producing sustainable butadiene. This paper reviews the reaction and its catalysts, and discusses the challenges their development faces.

Fundamental roles of ZnO and ZrO2 in the conversion of ethanol to 1,3-butadiene over ZnO–ZrO2/SiO2

ZnO and ZrO₂ sites in the ZnO–ZrO₂/SiO₂ catalyst act cooperatively to catalyze different steps of the conversion of ethanol to 1,3-butadiene.

Ethynylation of Formaldehyde over CuO/SiO2 Catalysts Modified by Mg Species: Effects of the Existential States of Mg Species

The highly effective catalytic synthesis of 1,4-butynediol (BD) from the Reppe process is a fascinating technology in modern chemical industry. In this work, we reported the effects of the existential states of Mg species in the CuO/silica-magnesia catalysts for the ethynylation of formaldehyde in a simulative slurry reactor. The physichemical properties of the supports and the corresponding catalysts were extensively characterized by various techniques. The experimental results indicated that the introduced Mg species in the form of MgO particles, MgO microcrystals, or Si-O-Mg structures effectively resulted in an abundance of medium-strong basic sites, which can synergize with the active Cu⁺ species, facilitate the activation of acetylene, and improve the ethynylation activity. For the CuO/MgO-SiO₂ catalyst, the existence of Si-O-Mg structures strengthened the Cu–support interaction, which were beneficial to improving the dispersion and the valence stability of the active Cu⁺ species. The highly dispersed Cu⁺ species, its stable valence state, and the abundant medium-strong basic sites enhanced the synergistic effect significantly, leading to the superior activity and stability of CuO/MgO-SiO₂. The insights into the role of the existential states of Mg species and the revelation of the synergistic effect between active Cu⁺ species and basic sites can provide theoretic guidance for future rational design of catalysts for the ethynylation reation.

Effect of ZnO on acid–base properties and catalytic performances of ZnO/ZrO2–SiO2 catalysts in 1,3-butadiene production from ethanol–water mixture

The effect of ZnO and the preparation method of ZnO/ZrO₂–SiO₂ catalysts on their acid–base properties and catalytic performances in the conversion of diluted ethanol mixtures into 1,3-butadiene (BD) is presented.

The deactivation of a ZnO doped ZrO2–SiO2catalyst in the conversion of ethanol/acetaldehyde to 1,3-butadiene

A deactivation study on the ethanol/acetaldehyde conversion to 1,3-butadiene over a ZnO promoted ZrO₂–SiO₂ catalyst prepared by a sol–gel method was performed. The samples were characterized by N₂ adsorption–desorption isotherms, scanning electron microscopy (SEM), NH₃ temperature programmed desorption (NH₃-TPD), X-ray powder diffraction characterization (XRD), thermogravimetric analyses (TGA), Fourier transform infrared resonance (FT-IR), ¹³C magic-angle spinning nuclear magnetic resonance (¹³C NMR) and X-ray photoelectron spectroscopy (XPS). The pore structure characteristics and surface acidity of Zn_0.5–Zr–Si catalysts were largely decreased with time-on-stream and no crystal structure was formed in the used catalyst, indicating that the deactivation was caused by carbon deposition. Two main types of carbon deposition were formed, namely low-temperature carbon deposition with the oxidation temperature of around 400 °C and high-temperature carbon deposition with the oxidation temperature of 526 °C. The carbon species were mainly composed of graphitized carbon, amorphous carbon, carbon in C–O bonds and carbonyls. The deactivated catalyst could be regenerated by a simple oxidation process in air. Adding a certain amount of water into the feed had a positive effect on reducing the carbon deposition.

Deactivation study on the ethanol/acetaldehyde conversion to 1,3-butadiene over a ZnO–ZrO₂–SiO₂ catalyst.

Ethanol/acetaldehyde conversion into butadiene over sol–gel ZrO2–SiO2 catalysts doped with ZnO

High performance and stability of a ZnO/ZrO₂–SiO₂ catalyst prepared via a sol–gel method in ethanol and acetaldehyde conversion into 1,3-butadiene process.

A DFT study on the aldol condensation reaction on MgO in the process of ethanol to 1,3-butadiene: understanding the structure–activity relationship

The mechanism of aldol condensation on MgO surfaces with different structures was investigated to illustrate the structure–activity relationship.

Surface chemistry of MgO/SiO2 catalyst during the ethanol catalytic conversion to 1,3-butadiene: in-situ DRIFTS and DFT study

1,3-Butadiene is an important commodity chemical and new, selective routes of catalytic synthesis using green feedstocks, such as ethanol, is of interest.

Highly active and selective binary MgO–SiO2 catalysts for the production of 1,3-butadiene from ethanol

Wet-kneaded binary MgO–SiO₂ composite catalysts gave exceptionally high productivity of butadiene governed by a subtle balance of acid–base sites in relation to the formation of an interfacial Si–O–Mg linkage and by varying preparation methods and MgO to SiO₂ ratios.

Designed synthesis of MOx (M = Zn, Fe, Sn, Ni, Mn, Co, Ce, Mg, Ag), Pt, and Au nanoparticles supported on hierarchical CuO hollow structures

Despite intensive research into support substrates for the dispersal of nanoparticles and their applications, there has been a lack of general methods to produce metal oxide hollow substrates supporting a wide range of metal and metal oxides. Herein, a synthetic protocol for the preparation of CuO hollow structure-supported MO_x (M = Zn, Fe, Ni, Sn, Mn, Co, Ce, Mg, and Ag) and noble metals (Pt and Au) with the desired properties and shell structure, such as CuO/Fe₂O₃, CuO/ZnO, CuO/SnO₂, CuO/MgO, CuO/NiO, CuO/Mn₂O₃, CuO/CoO, CuO/CeO₂, CuO/Ag₂O, CuO/Pt, CuO/Au hollow cubes, CuO/ZnO double-shell hollow cubes, CuO/SnO₂ double-shell hollow octahedra, CuO/SnO₂/Fe₂O₃ and CuO/Mn₂O₃/NiO double-shell hollow cubes, was developed based on controlled calcination and etching. These hybrid hollow structures were employed not only as support substrates but also as active constituents for catalytic reactions. As an example, we demonstrated that CuO/ZnO hollow cubes are remarkably efficient in converting solid chitin biomass to liquid chemicals in methanol. In addition, CuO/ZnO double-shell hollow cubes were highly effective in the oxidation of benzyl alcohol in the presence of H₂O₂, whereas CuO/Pt and CuO/Au hollow cubes promoted the oxidation of benzyl alcohol in pure O₂. The strategy developed in this work extends the controllable fabrication of high-quality CuO hollow structure-supported nanoparticles using various compositions and shell structures, paving the way to the exploration and systematic comparison of these materials in a wider range of applications.

Catalytic Activity of Bimetallic Cu-Ag/MgO-SiO2 Toward the Conversion of Ethanol to 1,3-Butadiene

In the present work, the catalytic conversion of ethanol to 1,3-butadiene (1,3-BD) was studied over monometallic of Cu and Ag, and bimetallic Cu-Ag supported on MgO-SiO2 (with MgO/SiO2 ratio of 2.0) under the temperature range from 250 to 325 °C. All catalysts were prepared by 4 different techniques including (i) conventional impregnation, (ii) microwave-assisted method, (iii) polyvinyl alcohol/sodium borohydride (PVA/NaBH4) assisted method, and (iv) benzoxaxine-assisted method to elucidate the effect of catalyst preparation method on their catalytic performance. All fresh and spent catalysts were also characterized by X-ray diffraction (XRD), N2 adsorption and Temperature-programmed reduction (TPR) techniques to understand the relation between their physical/chemical properties and catalytic performance. From the reaction test, it was found that 5 %Ag/MgO-SiO2 showed greater activity towards 1,3-BD production than 5 %Cu/MgO-SiO2; nevertheless, higher deactivation after 6 h of operation was observed from 5 %Ag/MgO-SiO2. Importantly, this study revealed that bimetallic 2.5 %Cu-2.5 %Ag/MgO-SiO2 enhanced significantly higher activity and stability towards the reaction than monometallic catalysts. In addition, 2.5 %Cu-2.5 %Ag/MgO-SiO2 prepared by benzoxaxine-assisted method enhanced significantly higher reaction activity and stability than other preparation techniques, from which 1,3-BD yield of 46.40 % after 6 h of operation can be achieved. From the characterization, the good activity of this catalyst is mainly due to the dispersion improvement of metal over MgO-SiO2 support.

From Sugars to Wheels: The Conversion of Ethanol to 1,3-Butadiene over Metal-Promoted Magnesia-Silicate Catalysts

1,3-Butadiene (1,3-BD) is a high-value chemical intermediate used mainly as a monomer for the production of synthetic rubbers. The ability to source 1,3-BD from biomass is of considerable current interest because it offers the potential to reduce the life-cycle greenhouse gas (GHG) impact associated with 1,3-BD production from petroleum-derived naphtha. Herein, we report the development and investigation of a new catalyst and process for the one-step conversion of ethanol to 1,3-BD. The catalyst is prepared by the incipient impregnation of magnesium oxide onto a silica support followed by the deposition of Au nanoparticles by deposition-precipitation. The resulting Au/MgO-SiO2 catalyst exhibits a high activity and selectivity to 1,3-BD and low selectivities to diethyl ether, ethylene, and butenes. Detailed characterization of the catalyst shows that the desirable activity and selectivity of Au/MgO-SiO2 are a consequence of a critical balance between the acidic-basic sites associated with a magnesium silicate hydrate phase and the redox properties of the Au nanoparticles. A process for the conversion of ethanol to 1,3-BD, which uses our catalyst, is proposed and analyzed to determine the life-cycle GHG impact of the production of this product from biomass-derived ethanol. We show that 1,3-BD produced by our process can reduce GHG emissions by as much as 155 % relative to the conventional petroleum-based production of 1,3-BD.