Catalysts For Higher Alcohol Synthesis Research Articles

Regulating the electronic property of iron catalysts for higher alcohols synthesis from CO2 hydrogenation

The electronic property of a catalyst is crucial to the generation of key reaction intermediates for targeted synthesis. Herein, we reported a strategy by modifying iron catalysts with sulfate and alkali metal (Li, Na, or K) to regulate the electronic property and optimize the reaction pathways for CO2 hydrogenation to higher alcohols. The characterizations demonstrated the influencing relationship between the electronic property of iron catalysts and the catalytic capabilities for CO dissociation, non-dissociated CO activation and catalytic hydrogenation, which were critical to selective synthesis of higher alcohols. Na-S modification was proven more effective to balance the multiple capabilities required for higher alcohols synthesis and the NaS-Fe catalyst gave a higher C2+OH yield in CO2 hydrogenation. DFT calculations further validated the advantage of Na-S modification from the aspects of CO adsorption and C−C coupling. This strategy provides more flexibility in site regulation and applies to catalyst design for many reactions.

Remarkably enhanced catalytic performance of three-dimensional hierarchically porous Mo2C catalysts for higher alcohols synthesis from syngas

Higher alcohols synthesis (HAS) is an important branch of syngas conversion, and Mo2C-based catalyst is a promising system for this reaction. However, the CO conversion and alcohols selectivity of current Mo2C-based catalysts are still low, which hinders their industrial application. Here, a series of Mo2C with three-dimensional hierarchically porous (3DHP) structures were prepared via a hard template method and their catalytic performance in HAS was investigated. The CO conversion and higher alcohols proportion of the optimal 3DHP catalyst were increased from 5.1 % and 60.4 % to 17.6 % and 70.5 %, respectively, compared with that of bulk Mo2C under similar total alcohols selectivity. The enhancement of the catalytic performance could be related to the increased number of active sites and the synergistic effect between multivalent Mo species. Additionally, the optimal 3DHP catalyst demonstrated good stability over a period of 200 h. This study provides a potential application for 3DHP materials and an alternative for designing efficient Mo2C catalysts for the HAS reactions.

Tuning CuO crystallite size by different solvents for higher alcohols synthesis from syngas over CuZnAl catalyst

The crystallite size effect of metal oxides plays a vital role in the field of heterogeneous catalysis research. Herein, CuZnAl catalysts with varying CuO crystallite sizes are synthesized by coprecipitation method employing various solvents. The catalytic performance of CO hydrogenation is studied and the physical and chemical properties of catalysts are characterized by XRD, H2-TPR, N2 adsorption-desorption, and NH3/CO2-TPD-MS. The results indicate that the different types of solvents can effectively regulate CuO crystallite size, thereby affecting its reducibility and catalytic activity. Most importantly, we observe that CuO crystallite size is positive correlated with reduction temperature and negative correlated with C2+OH selectivity. The catalyst employing ethanol as a solvent exhibits the highest CO conversion (22.91 %) and the optimum proportion of C2+OH in total alcohols (18.96 %), which indicates that smaller CuO crystallite size facilitates reduction of Cu species and generation of larger pore size as well as suitable acid-basic sites, thereby promoting higher alcohols formation. Therefore, these findings greatly broaden understanding the size effect of CuO, providing a new strategy for rational design Cu-based catalysts for higher alcohols synthesis.

Influence of chalcopyrite removal and mechanical exfoliation on the performance of molybdenite catalysts supported on activated bauxite for alcohol synthesis by Fischer-Tropsch process

The top-down approach was used to develop catalysts for higher alcohol synthesis by starting with low-grade molybdenite concentrate and mesoporous activated bauxite as the active metal and support, respectively. The results of the study showed that the process of chemical leaching significantly reduced copper in the form of chalcopyrite in the concentrate by over 95%. This reduction in copper content of purified catalysts led to an increase in the selectivity for C3+ alcohols compared to catalysts based on impure molybdenite. Additionally, the process of exfoliation not only reduced the particle size of the active component but also increased the selectivity for C3+ alcohols and the conversion of CO. The chemical–mechanical activation process developed in this study resulted in an improvement in catalyst activity of more than 50%.

ZrO2-Promoted Cu-Co, Cu-Fe and Co-Fe Catalysts for Higher Alcohol Synthesis.

The development of efficient catalysts for the direct synthesis of higher alcohols (HA) via CO hydrogenation has remained a prominent research challenge. While modified Fischer-Tropsch synthesis (m-FTS) systems hold great potential, they often retain limited active site density under operating conditions for industrially relevant performance. Aimed at improving existing catalyst architectures, this study investigates the impact of highly dispersed metal oxides of Co-Cu, Cu-Fe, and Co-Fe m-FTS systems and demonstrates the viability of ZrO2 as a general promoter in the direct synthesis of HA from syngas. A volcano-like composition-performance relationship, in which 5-10 mol % ZrO2 resulted in maximal HA productivity, governs all catalyst families. The promotional effect resulted in a 2.5-fold increase in HA productivity for the optimized Cu1Co4@ZrO2-5 catalyst (Cu:Co = 1:4, 5 mol % ZrO2) compared to its ZrO2-free counterpart and placed Co1Fe4@ZrO2-10 among the most productive systems (345 mgHA h-1 gcat-1) reported in this category under comparable operating conditions, with stable performance for at least 300 h. ZrO2 assumes an amorphous and defective nature on the catalysts, leading to enhanced H2 and CO activation, facilitated formation of metallic and carbide phases, and structural stabilization.

Cerium doped Co/AC catalysts for higher alcohols synthesis from syngas

Higher alcohols synthesis (HAS) from CO hydrogenation has attracted a considerable attention owing to their utilization in fuels and chemical intermediates. However, it is still very difficult to improve the selectivity of higher alcohols via the Fischer-Tropsch process. Based on the understanding of the current research progress, in the present work, a series of the Ce doped activated carbon loaded Co catalysts were prepared and characterized by XRD, XPS, N2 adsorption-desorption, H2-TPR, and CO2-TPD-MS etc. It was found that there is a linearly positive correlation between the selectivity of total alcohols and oxygen vacancies, so the improvement of the selectivity to total alcohols can be achieved by increasing the number of oxygen vacancies on the catalyst surface. The Co-7.5Ce/AC catalyst showed the maximum oxygen vacancy ratio (46.5%), exhibiting the best total alcohols selectivity (23.5%). This work revealed the roles of oxygen vacancies in the synthesis of higher alcohols from syngas and provided a new idea for the development of Co-based catalysts for the process.

Identifying Descriptors for Promoted Rhodium-Based Catalysts for Higher Alcohol Synthesis via Machine Learning.

Rhodium-based catalysts offer remarkable selectivities toward higher alcohols, specifically ethanol, via syngas conversion. However, the addition of metal promoters is required to increase reactivity, augmenting the complexity of the system. Herein, we present an interpretable machine learning (ML) approach to predict and rationalize the performance of Rh-Mn-P/SiO2 catalysts (P = 19 promoters) using the open-source dataset on Rh-catalyzed higher alcohol synthesis (HAS) from Pacific Northwest National Laboratory (PNNL). A random forest model trained on this dataset comprising 19 alkali, transition, post-transition metals, and metalloid promoters, using catalytic descriptors and reaction conditions, predicts the higher alcohols space-time yield (STYHA) with an accuracy of R 2 = 0.76. The promoter's cohesive energy and alloy formation energy with Rh are revealed as significant descriptors during posterior feature-importance analysis. Their interplay is captured as a dimensionless property, coined promoter affinity index (PAI), which exhibits volcano correlations for space-time yield. Based on this descriptor, we develop guidelines for the rational selection of promoters in designing improved Rh-Mn-P/SiO2 catalysts. This study highlights ML as a tool for computational screening and performance prediction of unseen catalysts and simultaneously draws insights into the property-performance relations of complex catalytic systems.

Insight into the role of lanthanum-modified Cu[sbnd]Co based catalyst for higher alcohol synthesis from syngas

A series of lanthanum oxide modified CuCo based catalysts for the direct conversion of syngas to higher alcohols were synthesized via the coprecipitation method. The influence of lanthanum on the textural properties and catalytic performance was investigated. It was found that lanthanum-modified CuCo based catalysts possessed a novel nanosheet structure to form more oxygen vacancies. Compared with CuCo catalyst, the dissociative CO adsorption and associative CO adsorption capacities of LaxCuCo catalysts were improved markedly, and formate and methoxy intermediates were more easily formed on the surface of LaxCuCo catalysts, which is attributed to the proper synergy of the surface active sites (Cu0, Co0, and oxygen vacancies). In particular, the addition of lanthanum species reduced the thickness of the nanosheets and facilitated the high dispersion of LaxCuCo after reaction by acting as isolation islands to restrain the aggregation and growth of crystal grain. The evaluation results showed that optimized La0.3CuCo catalyst exhibited the highest CO conversion of 25.4%, superior total alcohols selectivity of 61.4%, and C2+ alcohols selectivity of 79.03% among the total alcohol products, and excellent stability.

Construction of Synergistic Co and Cu Diatomic Sites for Enhanced Higher Alcohol Synthesis

Construction of Synergistic Co and Cu Diatomic Sites for Enhanced Higher Alcohol Synthesis

Lamellar-Structured Silicate Derived Highly Dispersed CoCu Catalyst for Higher Alcohol Synthesis from Syngas

Lamellar-Structured Silicate Derived Highly Dispersed CoCu Catalyst for Higher Alcohol Synthesis from Syngas

Self-optimized and renewable Ni–Co alloy@Co–Co2C catalyst for higher alcohols synthesis from syngas

Higher alcohols synthesis (HAS) from syngas (CO/H2) has attracted widespread attention, while the low selectivity and poor stability of the catalysts mainly stumbled its industrial application. In the work, Ni–Co alloy nanoparticles (NPs) derived from Co1-xNixAl2O4 loaded on the SiO2 with large specific surface area were prepared; and during reaction, the highly dispersed Ni–Co alloys were self-optimized to Ni–Co alloy@Co–Co2C. Importantly, Ni–Co alloy@Co–Co2C can be regenerated through oxidation - reduction - self-optimization process. Characteristic results indicated that the structural liberalization during the reaction process inhibited the loss of Ni, regulated and balanced the dual active sites of the catalyst and the Ni–Co alloys were regenerated after the re-oxidation and re-reduction process. The optimized catalyst exhibited excellent catalytic performance, including a high total selectivity to alcohols of 39.3% and an excellent catalytic stability at 250 °C, 3.5 MPa (H2/CO = 2) and a space velocity of 6000 mL (gcat h)−1. In addition, the Ni–Co alloy@Co–Co2C catalyst after stability test could recover its original catalytic performance after re-oxidation and re-reduction. The renewable characteristics and superior catalytic performance of Ni–Co alloy@Co–Co2C made the catalyst to be one of the potential industrial catalysts for HAS.

CoFe alloy carbide catalysts for higher alcohols synthesis from syngas: Evolution of active sites and Na promoting effect

Higher alcohols synthesis (HAS) from syngas is quite attractive but still challenging due to the unsatisfied product selectivity and stability. Here, we prepared a series of CoFe bimetallic carbide catalysts and investigated the evolution of active species. The catalysts reduced above 300 °C could ensure an adequate interdiffusion between Co and Fe species to form CoFe alloy and then achieved a high fraction of ε'-(CoxFe1-x)2.2C species during HAS reaction, which exhibited excellent catalytic performance and stability over 200 h. The ε'-(CoxFe1-x)2.2C, acting as uniformly atomic neighboring CoxC-FexC dual sites, facilitated the synergy between CO nondissociative adsorption and CO dissociation, thus boosting the selective production of higher alcohols. It is also demonstrated that adding proper content of Na (0.25 wt%) can enhance the formation of ε'-(CoxFe1-x)2.2C as well as modulate the surface concentration of intermediates. These results may provide new idea for the design of high-performance catalysts for HAS.

Oxygen vacancies boosted Co-Co2C catalysts for higher alcohols synthesis from syngas

Co-Co2C catalyst has attracted much attention as the catalyst for higher alcohols synthesis due to comparatively high C2+OH selectivity. Herein, oxygen vacancies boosted Co-Co2C catalysts were fabricated via an in-situ reduction and topochemical carbonization process of La0.9K0.1CoxFe1-xO3/ZrO2. The results indicated that abundant oxygen vacancies were introduced into perovskite with the addition of Fe into the B site of perovskite. Under syngas atmosphere, part of Co0 was topochemical carbonized into Co2C, and Co-Co2C/LaFeO3-ZrO2 catalyst promoted by oxygen vacancies and K2O-La2O3 could be fabricated. No CO adsorption behaviors on Co2C were detected by in-situ CO-DRIFT and a linear correlation between alcohol selectivity and surface oxygen vacancies was observed, which verified that oxygen vacancies were the key active sites for alcohols formation on Co-Co2C catalyst. TPD results indicated that oxygen vacancies provided additional adsorption sites for CO and adjusted the adsorption forms of CO. Under the synergism effect between Co, Co2C and oxygen vacancies, Co-Co2C catalyst with abundant oxygen vacancies exhibited an excellent alcohol selectivity of 57.1 % and an outstanding stability. This work not only verified the in-situ conversation process of perovskite during reduction and reaction, but also revealed the catalytic mechanism of oxygen vacancies promoted Co-Co2C catalyst for higher alcohol synthesis.

Cobalt Carbide Nanocatalysts for Efficient Syngas Conversion to Value-Added Chemicals with High Selectivity.

Syngas conversion is a key platform for efficient utilization of various carbon-containing resources including coal, natural gas, biomass, organic wastes, and even CO2. One of the most classic routes for syngas conversion is Fischer-Tropsch synthesis (FTS), which is already available for commercial application. However, it still remains a grand challenge to tune the product distribution from paraffins to value-added chemicals such as olefins and higher alcohols. Breaking the selectivity limitation of the Anderson-Schulz-Flory (ASF) distribution has been one of the hottest topics in syngas chemistry.Metallic Co0 is a well-known active phase for Co-catalyzed FTS, and the products are dominated by paraffins with a small amount of chemicals (i.e., olefins or alcohols). Specifically, a cobalt carbide (Co2C) phase is typically viewed as an undesirable compound that could lead to deactivation with low activity and high methane selectivity. Although iron carbide (FexC) can produce olefins with selectivity up to ∼60%, the fraction of methane is still rather high, and the required high reaction temperature (300-350 °C) typically causes coke deposition and fast deactivation. Recently, we discovered that Co2C nanoprisms with preferentially exposed facets of (020) and (101) can effectively produce olefins from syngas conversion under mild reaction conditions with high selectivity. The methane fraction was limited within 5%, and the product distribution deviated greatly from ASF statistic law. The catalytic performances of Co2C nanoprisms are completely different from that reported for the traditional FT process, exhibiting promising potential industrial application.This Account summarizes our progress in the development of Co2C nanoprisms for Fischer-Tropsch synthesis to olefins (FTO) with remarkable efficiencies and stability. The underlying mechanism for the observed unique catalytic behaviors was extensively explored by combining DFT calculation, kinetic measurements, and various spectroscopic and microscopic investigation. We also emphasize the following issues: particle size effect of Co2C, the promotional effect of alkali and Mn promoters, and the role of metal-support interaction (SMI) in fabricating supported Co2C nanoprisms. Specially, we briefly review the synthetic methods for different Co2C nanostructures. In addition, Co2C can also be applied as a nondissociative adsorption center for higher alcohol synthesis (HAS) via syngas conversion. We also discuss the construction of a Co0/Co2C interfacial catalyst for HAS and demonstrate how to tune the reaction network and strengthen CO nondissociative adsorption ability for efficient production of higher alcohols. We believe that the advances in the development of Co2C nanocatalysts described here present a critic step to produce chemicals through the FTS process.

CuCo alloy nanonets derived from CuCo2O4 spinel oxides for higher alcohols synthesis from syngas

Porous CuCo alloy nanonets were used as superior catalysts for higher alcohol synthesis from syngas. The catalyst was fabricated via structural topological transformation of CuCo2O4 spinel precursor.

Mechanistic Aspects of the Role of K Promotion on Cu–Fe-Based Catalysts for Higher Alcohol Synthesis from CO2 Hydrogenation

Direct CO2 hydrogenation to higher alcohols (HAs) is a promising way to achieve the conversion of CO2 to high-value chemicals. Alkali metals as promoters are generally crucial for Cu–Fe-based catal...

Recent Progress in CO Hydrogenation over Bimetallic Catalysts for Higher Alcohol Synthesis

AbstractThe conversion of carbon monoxide and hydrogen, generally called synthesis gas, to higher alcohols has gained recent attention. Alcohols can be either transformed into other value‐added products such as ethers or used directly as fuels or fuel additives. Various types of catalysts have been prepared and investigated for the hydrogenation of CO to higher alcohols and improvements are in progress to find a robust catalyst with high activity and selectivity towards higher alcohols. In particular, the role of the bimetallic catalyst having two active sites contributing efficiently to higher alcohol synthesis has been a focus in recent years. Herein, the recent development in bimetallic catalyst preparation and the investigations of the reaction mechanism in CO hydrogenation have been reviewed.

Preparation and evaluation of highly dispersed HHSS supported Cu-Fe bimetallic catalysts for higher alcohols synthesis from syngas

Porous carriers play an important role in the catalytic transformation of syngas into higher alcohols, which promises higher sustainability in C1 chemistry. In this work, a series of hierarchical hollow silica spheres (HHSS) supported Cu-Fe bimetal catalysts were successfully prepared through ultrasonic-assisted impregnation for higher alcohols synthesis from syngas. Structural characterization results indicate that the hierarchical hollow structure of HHSS support can be maintained and the Cu-Fe bimetallic nanoparticles are highly dispersed on HHSS surface. The catalytic performances of samples in the test of CO hydrogenation for higher alcohols synthesis were investigated. The results revealed that the conversion rate of CO and the selectivity of C2+OH alcohol increased first and then decreased with the decrease of the amount of Cu content in the CuxFey@HHSS catalyst. The highest CO conversion, alcohol selectivity and STYROH over Cu-Fe@HHSS catalyst are 65.1 %, 46.6 %, and 118.1 gkg−1 h−1, respectively. It was found that a large number of CuFe2O4 were formed in Cu-Fe@HHSS catalyst and also confirmed that the CuFe2O4 spinel and CuO-CuFe2O4 were converted to Cu-Fe5C2 composite in the spent Cu-Fe@HHSS catalyst, which can enhance the synergy between Cu-Fe bimetals. Furthermore, copper and iron are highly dispersed on HHSS after the reaction, which enhances the structural stability of the catalyst. Based on the development and utilization of low-cost catalysts and the production of clean liquid fuels, HHSS has a great prospect of catalyst support in the energy field.

Syngas to higher alcohols synthesis over 3D printed KMoCo/ZSM5 monolith

The catalytic conversion of syngas into high carbon number alcohols (ethanol, propanol, butanol) has opened an avenue for the development of sustainable aviation fuels. The commercial production of higher alcohols from syngas remain challenging because of several constraints including poor selectivity, harsh operating conditions, and unavailability of suitable technology. The present study is based on metal impregnated zeolite-based catalysts for catalytic conversion of syngas into higher alcohols. Following the superior catalytic performance of powdered ZSM5 (Si/Al 100), a structured monolith was engineered via 3D printing (Hyrel 3D – Engine SR). The catalyst precursors (K–Mo–Co) were in situ grown (by hydrothermal treatment) onto channels of zeolite monolith. A comparison between monolithic and powdered structures revealed a similar catalytic performance at lower space velocities (< 3000 h−1). With an increasing space velocity at 6000 h−1 and above, the structured catalyst retained its catalytic performance, whereas, carbon monoxide conversion dropped significantly (~20%) over powdered catalyst. Moreover, the by-products formation (methane and carbon monoxide) were reduced over structured monolith. The development of zeolite-based monolith has provided an opportunity to overcome diffusional limitations for better utilization of intrinsic kinetics of Mo-Co based catalysts for higher alcohols synthesis.

The Study on Higher Alcohols Synthesis from Syngas over CuZnAl Catalysts Derived from Hydrotalcite‐Like Precursors

AbstractA series of CuZnAl catalysts with different Al contents were derived from hydrotalcite‐like precursors prepared by the coprecipitation method. Activity evaluation of the catalyst for higher alcohols synthesis from syngas was investigated, and the catalysts were characterized by XRD, BET, H2‐TPR, CO2‐TPD‐MS and CO‐TPD‐MS. The results revealed that different Al content showed an influence on the dispersion of the reducible Cu species, the specific surface area, the surface alkali strength and the adsorption capacity of CO, which affecting the CO conversion and the selectivity of higher alcohols. Catalysts with strong interaction between CuO and Al species, more medium and strong basic sites, and adequate CO dissociation adsorption benefited production of higher alcohols.