Influence of different precursors on isobutene production from bio-ethanol over bifunctional Zn1Zr10Ox catalysts

Zhao, Biao; Men, Yongfeng; Zhang, Anni; Wang, Jinguo; He, Rong; An, Wei; Li, Shenxiao

doi:10.1016/j.apcata.2018.04.003

Cited by 17 publications

(3 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Porous amorphous zirconia and the zinc–zirconia mixed oxides were synthesized using modifications of previously reported methods. ,− Amorphous zirconium oxyhydroxide (ZrO x (OH) 4–2 x ) was formed by adding ammonium hydroxide (Spectrum, 28–30%) dropwise to a stirred solution of 0.5 M zirconyl chloride octahydrate (Sigma Aldrich, 98%) at 298 K. The precipitate was filtered and rinsed with 10% ammonium hydroxide and dried at 383 K for 24 h. The zinc–zirconia mixed oxides were prepared via incipient wetness impregnation of amorphous zirconium oxyhydroxide with an aqueous solution of zinc nitrate hexahydrate (Alfa Aesar, 99%) in a mortar with varying concentrations of zinc nitrate corresponding to the target Zn weight loadings. The wetted support was ground with a mortar and pestle.…”

Section: Methodsmentioning

confidence: 99%

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over Zn_xZr_yO_z

2019

View full text Add to dashboard Cite

Isobutene is a specialty chemical used in the production of fuel additives, polymers, and other high-value products. While normally produced by steam cracking of petroleum naphtha, there is increasing interest in identifying routes to synthesizing isobutene from biomass-derived compounds, such as ethanol and acetone. Recent work has shown that zinc−zirconium mixed oxides are effective and selective catalysts for producing isobutene from ethanol. However, the reaction pathway, the roles of acidic and basic sites, and the role of water in promoting stability and selectivity are not yet clearly defined. In this study, a series of zinc− zirconium mixed oxides with tunable acid−base properties were synthesized and characterized with XRD, Raman spectroscopy, BET, CO 2 -TPD, NH 3 -TPD, and IR DRIFTS of adsorbed pyridine in order to probe the roles of acid and base sites for each step in the ethanol-to-isobutene reaction pathway. The observed reaction kinetics, supported by modeling of these kinetics, suggest that the reaction of ethanol to isobutene proceeds via a five-step sequence. Ethanol first undergoes dehydrogenation to acetaldehyde, which is then oxidized to acetic acid. This product undergoes ketonization to produce acetone, which dimerizes to form diacetone alcohol. The latter product either decomposes directly to isobutene and acetic acid or produces these products by dehydration to mesityl oxide and subsequent hydrolysis. The acetic acid formed undergoes ketonization to produce additional acetone. The dispersion of zinc oxide on zirconia was found to produce a balance between Lewis acidic and basic sites that prevent the loss of ethanol via dehydration to ethylene and promote the cascade reactions of ethanol and acetone to isobutene. Water, while inhibiting both isobutene and mesityl oxide formation, improves isobutene selectivity by suppressing side reactions such as unimolecular dehydration, acetone decomposition, and deactivation due to coke formation.

show abstract

Section: Methodsmentioning

confidence: 99%

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over Zn_xZr_yO_z

2019

View full text Add to dashboard Cite

show abstract

“…Bioethanol is a widely produced renewable feedstock (∼86 million tons per year worldwide in 2018) that can be valorized into key short-chain (C 3 –C 6 ) olefin intermediates (e.g., propene, 1-butene, isobutene), a class of critical precursors for oligomerization into middle-distillate-range hydrocarbons and commodity chemical production . Direct conversion of ethanol to C 3+ olefins is typically accomplished over either Brønsted acid zeolites , or metal oxides − with limited olefin selectivities due to the formation of aromatics and paraffins, − ethylene, oxygenates, or other side products including CO 2 . , Therefore, a strong need remains for an approach to selective C 3+ olefin production for economically viable liquid renewable fuel generation without significant carbon losses, especially since carbon conversion efficiency is a primary cost driver for renewable fuel production …”

Section: Introductionmentioning

confidence: 99%

Selective Butene Formation in Direct Ethanol-to-C₃₊-Olefin Valorization over Zn–Y/Beta and Single-Atom Alloy Composite Catalysts Using In Situ-Generated Hydrogen

et al. 2021

View full text Add to dashboard Cite

The selective production of C3+ olefins from renewable feedstocks, especially via C1 and C2 platform chemicals, is a critical challenge for obtaining economically viable low-carbon middle-distillate transportation fuels (i.e., jet and diesel). Here, we report a multifunctional catalyst system composed of Zn–Y/Beta and “single-atom” alloy (SAA) Pt–Cu/Al2O3, which selectively catalyzes ethanol-to-olefin (C3+, ETO) valorization in the absence of cofed hydrogen, forming butenes as the primary olefin products. Beta zeolites containing predominately isolated Zn and Y metal sites catalyze ethanol upgrading steps (588 K, 3.1 kPa ethanol, ambient pressure) regardless of cofed hydrogen partial pressure (0–98.3 kPa H2), forming butadiene as the primary product (60% selectivity at an 87% conversion). The Zn–Y/Beta catalyst possesses site-isolated Zn and Y Lewis acid sites (at ∼7 wt % Y) and Brønsted acidic Y sites, the latter of which have been previously uncharacterized. A secondary bed of SAA Pt–Cu/Al2O3 selectively hydrogenates butadiene to butene isomers at a consistent reaction temperature using hydrogen generated in situ from ethanol to butadiene (ETB) conversion. This unique hydrogenation reactivity at near-stoichiometric hydrogen and butadiene partial pressures is not observed over monometallic Pt or Cu catalysts, highlighting these operating conditions as a critical SAA catalyst application area for conjugated diene selective hydrogenation at high reaction temperatures (>573 K) and low H2/diene ratios (e.g., 1:1). Single-bed steady-state selective hydrogenation rates, associated apparent hydrogen and butadiene reaction orders, and density functional theory (DFT) calculations of the Horiuti–Polanyi reaction mechanisms indicate that the unique butadiene selective hydrogenation reactivity over SAA Pt–Cu/Al2O3 reflects lower hydrogen scission barriers relative to monometallic Cu surfaces and limited butene binding energies relative to monometallic Pt surfaces. DFT calculations further indicate the preferential desorption of butene isomers over SAA Pt–Cu(111) and Cu(111) surfaces, while Pt(111) surfaces favor subsequent butene hydrogenation reactions to form butane over butene desorption events. Under operating conditions without hydrogen cofeeding, this combination of Zn–Y/Beta and SAA Pt–Cu catalysts can selectively form butenes (65% butenes, 78% C3+ selectivity at 94% conversion) and avoid butane formation using only in situ-generated hydrogen, avoiding costly hydrogen cofeeding requirements that hinder many renewable energy processes.

show abstract

“…Bio‐ethanol has emerged as a chemical feedstock available from biomass and could provide alternative routes to producing value‐added chemicals, such as acetaldehyde,ethyl acetate, acetic acid, and lower olefins over various catalysts. Upgrading bio‐ethanol to C4‐olefins has been recognized as one of the most important strategic reactions to produce highly valuable chemicals .…”

Section: Methodsmentioning

confidence: 99%

Tailoring the Selectivity of Bio‐Ethanol Transformation by Tuning the Size of Gold Supported on ZnZr₁₀O_x Catalysts

Men

Liu

et al. 2018

ChemCatChem

Self Cite

View full text Add to dashboard Cite

The selective bio-ethanol cascade transformation to hydrocarbons over multifunctional catalysts is a highly promising sustainable pathway to high-value chemicals and fuels. However, principles to control the selectivity of the bio-ethanol transformation using the effects of the size of nanoparticle catalysts have remainedlargely unexplored. Here, using bioethanol transformation reactions catalyzed by Au/ZnZr 10 O x as examples, we demonstrate that changing the fashion of gold loading enables control over product distribution. Our results reveal that larger gold particles tendto show much higher selectivity for 1,3-butadiene, whereas smaller gold nanoparticles favor the formation of acetaldehyde.This study uncovers general principles for tailoring the selectivity of bio-ethanol transformation by carefully engineering the size of gold. It opens a new avenue for the rational design of multifunctional catalysts to enhance the production of desired reaction products in complex cascade reaction sequences.Bio-ethanol has emerged as a chemical feedstock available from biomass and could provide alternative routes to producing value-added chemicals, [1] such as acetaldehyde, [2] ethyl acetate, [3] acetic acid, [4] and lower olefins [5] over various catalysts. Upgrading bio-ethanol to C4-olefins has been recognized as one of the most important strategic reactions to produce highly valuable chemicals. [6] Direct conversion of bioethanol into 1,3-butadiene (1,3-BD) (Lebedev process; Scheme 1) is quite complex because of the nature of the cascade reaction. [7] Mixed metal oxides with multiple catalytic functionality, in particular MgO-SiO 2 binary composite oxides, have been found to be very effective for the Lebedev process. [8] It is generally accepted that the crucial factor affecting BD formation is a subtle optimal ratio of acid-to-base sites to enhance the reactivity. [9] Since the pioneering work showing exceptional catalytic activity of gold in low-temperature oxidation of CO by Haruta, and in hydrochlorination of ethylene by Hutchings, [10] the catalytic activity of supported nanosize gold catalysts has become a fascinating fundamental issue and attracted a great deal of attention in heterogeneous catalysis. [11] Recent progress in nanocatalysis based on sizing and shaping gold nanoparticles provides new approaches for tuning catalytic reactivity and stability. [12] Hensen et al. reported a ternary spinel (MgCuCr 2 O 4 )-supported gold catalyst for aerobic oxidation of ethanol to acetaldehyde that is capable of achieving unprecedented reactivity of~100 % ethanol conversion with~95 % acetaldehyde selectivity at 250 8C. [13] Flytzani-Stephanopoulos et al. showed that atomically dispersed nanosize gold on a ZnZrO x support was very active in achieving low-temperature ethanol dehydrogenation exclusively to acetaldehyde and hydrogen. [2] Recently, Bell et al. showed that gold supported on MgO : SiO 2 is an active catalyst for converting ethanol to 1,3-BD; and gold improved the dehydrogenation activity, resulting in i...

show abstract

Influence of different precursors on isobutene production from bio-ethanol over bifunctional Zn1Zr10Ox catalysts

Cited by 17 publications

References 63 publications

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over Zn_xZr_yO_z

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over Zn_xZr_yO_z

Selective Butene Formation in Direct Ethanol-to-C₃₊-Olefin Valorization over Zn–Y/Beta and Single-Atom Alloy Composite Catalysts Using In Situ-Generated Hydrogen

Tailoring the Selectivity of Bio‐Ethanol Transformation by Tuning the Size of Gold Supported on ZnZr₁₀O_x Catalysts

Contact Info

Product

Resources

About

Influence of different precursors on isobutene production from bio-ethanol over bifunctional Zn1Zr10Ox catalysts

Cited by 17 publications

References 63 publications

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over ZnxZryOz

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over ZnxZryOz

Selective Butene Formation in Direct Ethanol-to-C3+-Olefin Valorization over Zn–Y/Beta and Single-Atom Alloy Composite Catalysts Using In Situ-Generated Hydrogen

Tailoring the Selectivity of Bio‐Ethanol Transformation by Tuning the Size of Gold Supported on ZnZr10Ox Catalysts

Contact Info

Product

Resources

About

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over Zn_xZr_yO_z

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over Zn_xZr_yO_z

Selective Butene Formation in Direct Ethanol-to-C₃₊-Olefin Valorization over Zn–Y/Beta and Single-Atom Alloy Composite Catalysts Using In Situ-Generated Hydrogen

Tailoring the Selectivity of Bio‐Ethanol Transformation by Tuning the Size of Gold Supported on ZnZr₁₀O_x Catalysts