Selective Hydrogenation Process Research Articles

Catalytic Application of Atomically Precise Metal Clusters in Selective Hydrogenation Processes

Catalytic Application of Atomically Precise Metal Clusters in Selective Hydrogenation Processes

Cu-Doped CoZn@NC promotes catalytic activity of furfural hydrogenation at low temperature: Regulation of copper

The low-cost Cu-based catalysts have excellent selectivity in biomass hydrogenation, but it is challenging to improve their catalytic activity at low temperature. Herein, the trimetallic CuxCoZn@NC (where x = 0.1, 0.3, 0.5 mmol is the molar mass of Cu) were prepared by in suit pyrolysis using trimesic acid with stronger coordination ability. When it was applied to the furfural (FF) selective hydrogenation process, the catalytic yield of the optimal Cu0.3CoZn@NC reached >99 % under mild condition of 90 °C, which was 29 times superior to that of the CoZn@NC without Cu doping. The results demonstrate that the doping of Cu reduces the activation energy of CuxCoZn@NC and increases the catalytic activity at low temperature relative to CoZn@NC. The characterizations and density functional theory (DFT) calculations show that the incorporation of suitable Cu content enhances the interaction between Cu and Co. The amount of surface-active Co0 and the electron density are significantly enhanced, which effectively stimulates the dissociation of hydrogen. Moreover, the Lewis acid content is significantly increased to facilitate the adsorption and activation of FF. Meanwhile, the impact of Cu content variation on the performance of the multi-metal catalyst is discussed. This work is promising to establish a foundation for the accurate design of polymetallic catalysts through adjusting the Cu content to regulate the reaction activity and selectivity.

Mechanistic and Compositional Aspects of Industrial Catalysts for Selective CO2 Hydrogenation Processes

The characteristics of industrial catalysts for conventional water-gas shifts, methanol syntheses, methanation, and Fischer-Tropsch syntheses starting from syngases are reviewed and discussed. The information about catalysts under industrial development for the hydrogenation of captured CO2 is also reported and considered. In particular, the development of catalysts for reverse water-gas shifts, CO2 to methanol, CO2-methanation, and CO2-Fischer-Tropsch is analyzed. The difference between conventional catalysts and those needed for pure CO2 conversion is discussed. The surface chemistry of metals, oxides, and carbides involved in this field, in relation to the adsorption of hydrogen, CO, and CO2, is also briefly reviewed and critically discussed. The mechanistic aspects of the involved reactions and details on catalysts’ composition and structure are critically considered and analyzed.

Catalytic Conversion of Lignin into Valuable Chemicals: Full Utilization of Aromatic Nuclei and Side Chains.

ConspectusIn recent years, significant efforts have been directed toward achieving efficient and mild lignocellulosic biomass conversion into valuable chemicals and fuels, aiming to address energy and environmental concerns and realize the goal of carbon neutrality. Lignin is one of the three primary building blocks of lignocellulose and the only aromatic renewable feedstock. However, the complex and diverse nature of lignin feedstocks, characterized by their three-dimensional, highly branched polymeric structure and intricate C-O/C-C chemical bonds, results in substantial challenges. To tackle these challenges, we carried out extensive research on selectively activating and transforming chemical bonds in lignin for chemical synthesis. In this Account, we discuss our recent progress in catalytic lignin conversion.Our work is focused on two main objectives: (i) achieving precise and selective transformation of C-O/C-C bonds in lignin (and its model compounds) and (ii) fully utilizing the aromatic nuclei and side chains present in lignin to produce valuable chemicals. Lignin consists of interconnected phenylpropanoid subunits linked by interlaced C-C/C-O bonds. To unlock the full potential of lignin, we propose the concept of "the full utilization of lignin", which encompasses both the aromatic nuclei and the side chains (e.g., methoxyl and polyhydroxypropyl groups).For the conversion of aromatic nuclei, selective activation of C-O and/or C-C bonds is crucial in synthesizing targeted aromatic products. We begin with model compounds (such as anisole, phenol, guaiacol, etc.) and then transition to protolignin feedstocks. Various reaction routes are developed, including self-supported hydrogenolysis, direct Caryl-Csp3 cleavage, coupled Caryl-Csp3 cleavage and Caryl-O hydrogenolysis, and tandem selective hydrogenation and hydrolysis processes. These tailored pathways enable high-yield and sustainable production of a wide range of aromatic (and derived) products, including arenes (benzene, toluene, alkylbenzenes), phenols, ketones, and acids.In terms of side chain utilization, we have developed innovative strategies such as selective methyl transfer, coupling depolymerization-methyl shift, selective acetyl utilization, and new activation methods such as amine-assisted prefunctionalization. These strategies enable the direct synthesis of methyl-/alkyl-derived products, such as acetic acid, 4-ethyltoluene, dimethylethylamine, and amides. Additionally, aromatic residues can be transformed into chemicals or functionalized ingredients that can serve as catalysts or functional biopolymer materials. These findings highlight promising opportunities for harnessing both the aromatic nuclei and side chains of lignin in a creative manner, thereby improving the overall atom economy of lignin upgrading.Through innovative catalyst engineering and reaction route strategies, our work achieves the sustainable and efficient production of various valuable chemicals from lignin. By integrating side chains and aromatic rings, we have successfully synthesized methyl-/alkyl-derived and aromatic-derived products with high yields. The full utilization of lignin not only minimizes waste but also opens up new possibilities for generating chemical products from lignin. These novel approaches unlock the untapped potential of lignin, expand the boundaries of lignin upgrading, and enhance the efficiency and economic viability of lignin biorefining.

Catalytic Performance of Pd/Al2O3 Catalyst in the Presence of HHDMA Ligand in Acetylene Selective Hydrogenation Process

A series of Pd-HHDMA/Al2O3 catalysts were prepared with various Pd and hexadecyl-2-hydroxyethyldimethylammonium dihydrogen phosphate (HHDMA) amounts by the reduction-deposition method. The catalysts were characterized by N2-physisorption, FE-SEM, CO-TPD, TG and FT-IR techniques. Performance tests for tail-end semi-hydrogenation of acetylene to ethylene were performed in a fixed-bed reactor at 60 °C, 10 bar and GHSV=4000 h-1 . All catalysts exhibited egg-shell Pd distribution which is beneficial for selective semihydrogenation reaction. The BET surface area and pore volume of the catalysts decreased with increasing HHDMA content for a given Pd loading. The conversion of acetylene increased with Pd loading and decreased with HHDMA content. The ethylene production increased with HHDMA whereas that of undesirable C4+ oligomerization products (“green oil”), which are coke precursors, was effectively suppressed.

Regulating metal-support interactions of Pd/MgAl2O4 for efficient selective hydrogenation of acetylene

Selective hydrogenation of a trace amount of acetylene to ethylene is a green and economical process to purify the ethylene stream in the olefin industry. Pd-based catalysts are widely explored for this process due to their excellent H2 and C2H2 activation abilities. However, the strong adsorption of C2H4 on metallic Pd sites often leads to the undesired over-hydrogenation product (i.e., ethane). Herein, we fabricated Pd/MgAl2O4 catalysts with tunable metal-support interactions by changing calcination temperatures to efficiently modify the electronic structure of Pd species. The Pd/MgAl2O4 with the optimized calcination temperature exhibits 96 % acetylene conversion and enhanced ethylene selectivity of 87 % due to weak adsorption of intermediates at 120 ℃, and shows excellent stability with negligible activity decay during a 50 h test. This work provides a strategy for designing catalysts with regulated metal-support interactions for selective hydrogenation processes.

Enhanced Stability for Chemoselective Hydrogenation of Nitroarenes by Carbon Layer Coated Ni‐Fe Alloy Catalyst

AbstractNon‐noble bimetallic alloys serve as an alternative catalytic material for noble metal‐based catalysts that could be applied in selective hydrogenation of unsaturated compounds. However, maintaining the catalytic stability for bimetallic nanoparticles in the selective hydrogenation process remains a substantial challenge, due to its high tendency to structural transformation upon reactive circumstances. Herein, this problem is solved by constructing carbon‐protected catalytic sites within carbon layer‐coated Ni−Fe nanoalloy composite via pyrolysis of NiFex(OH)2/glucose precursor. The optimized NiFe0.06@C catalyst exhibits excellent stability and selectivity to aminostyrene (>97 %) in the chemoselectivity hydrogenation of 3‐nitrostyrene reaction. Various characterization indicates that the enhancement in stability originates from the protective effect of the carbon layer, which prevents the oxidation and aggregation of Ni−Fe nanoparticles during the reaction process. This work greatly advances non‐noble metal‐catalyzed selective hydrogenation of nitroarenes and helps the rational design of bimetallic catalysts.

Regulating the catalytic activities of Ni and Pd through doping on Fe2O3HT for selective hydrogenation of conjugated aldehyde (citral) in lemongrass essential oil to organoleptically superior monoterpene alcohols (geraniol/nerol)

Fe2O3 was modified by doping Ni and Pd to obtain 3%Ni-1.5%Pd/Fe2O3HT catalyst via the hydrothermal process for selective hydrogenation of citral to nerol and geraniol. This catalyst was prepared by different techniques like co-precipitation, wet impregnation, and hydrothermal process, and their activity towards citral hydrogenation was thoroughly studied. The prepared catalysts were thoroughly characterized. Various parameters such as pressure, temperature, reaction time, and metal weight (%) have been optimized through the RSM-BBD module to attain high selectivity towards nerol and geraniol. The optimal reaction conditions of 6.45 bar pressure, 3%Ni-1.5%Pd loading at 72.1 °C for 84 min, the citral (>99%) was converted to nerol/geraniol with 97.2% of selectivity. The modified catalyst activated the oxygen species of the carbonyl atom and thus favours the selective hydrogenation of the CO bond without reducing the CC bond. This process is very effective for the selective transformation of citral (75%) in lemongrass essential oil to organoleptically superior nerol/geraniol-rich oil using 3%Ni-1.5%Pd/Fe2O3HT catalyst.

Electrochemistry-assisted selective butadiene hydrogenation with water

Alkene feedstocks are used to produce polymers with a market expected to reach 128.4 million metric tons by 2027. Butadiene is one of the impurities poisoning alkene polymerization catalysts and is usually removed by thermocatalytic selective hydrogenation. Excessive use of H2, poor alkene selectivity and high operating temperature (e.g. up to 350 °C) remain the most significant drawbacks of the thermocatalytic process, calling for innovative alternatives. Here we report a room-temperature (25~30 °C) electrochemistry-assisted selective hydrogenation process in a gas-fed fixed bed reactor, using water as the hydrogen source. Using a palladium membrane as the catalyst, this process offers a robust catalytic performance for selective butadiene hydrogenation, with alkene selectivity staying around 92% at a butadiene conversion above 97% for over 360 h of time on stream. The overall energy consumption of this process is 0.003 Wh/mLbutadiene, which is thousands of times lower than that of the thermocatalytic route. This study proposes an alternative electrochemical technology for industrial hydrogenation without the need for elevated temperature and hydrogen gas.

Вовлечение бутадиенсодержащих фракций в сырье производства метил-трет-бутиловый эфира и олигомеризации

The paper considers the possibility of involving additional butane-butylene feedstock in the MTBE synthesis and oligomerization unit. An important factor is the content of diene hydrocarbons in BBF, which negatively affects the activity of the catalyst and accordingly the product yield of the unit. In this connection possibility of implementation of selective hydrogenation process was analyzed in order to improve quality of feedstock in terms of target components of MTBE and oligomerizate synthesis. Calculations of process in specialized software were carried out.

Increasing the Distance of Adjacent Palladium Atoms for Configuration Matching in Selective Hydrogenation.

Precisely tailoring the distance between adjacent metal sites to match adsorption configurations of key species for the targeted reaction pathway is a great challenge in heterogeneous catalysis. Here, we report a proof-of-concept study on the atomically sites-tailored pathway in Pd-catalyzed acetylene hydrogenation, i.e., increasing the distance of adjacent Pd atoms (dPd-a-Pd ) for configuration matching in acetylene semi-hydrogenation against coupling. dPd-a-Pd is identified as a structural descriptor for describing the competitiveness for reaction pathways, and the increased dPd-a-Pd prefers the semi-hydrogenation pathway due to simultaneously promoted C2 H4 desorption and the destabilized transition state of the C2 H3 * coupling. Spectroscopic, kinetics and electronic structure studies reveal that increasing dPd-a-Pd to 3.31 Å delivers superior selectivity and stability due to energy matching and appropriate hybridization of Pd 4d with In 2s and, especially, 2p orbitals.

Reversing the Catalytic Selectivity of Single-Atom Ru via Support Amorphization.

Supported single-atom catalysts (SACs), with the extremely homogenized active sites could achieve high hydrogenation selectivity toward one of the functional groups coexisting in the reactant molecule. However, as to the target group, the control of selective recognition and activation by SACs still remains a challenge. Herein, the phase engineering of the support is adopted to control the chemo-recognition behavior of SACs in selective hydrogenation. Single-atom Ru on amorphous porous ultrathin TiO2 nanosheets (Ru1/a-TiO2) is constructed, in which Ru is more positively charged than that in the crystalline counterpart (Ru1/c-TiO2). Moreover, in the nitro/vinyl selective hydrogenation process, Ru1/a-TiO2 shows superior nitro selectivity, opposite to the vinyl selectivity of Ru1/c-TiO2. Density functional theory calculations for single-atom Ru of different charge states show that the reactant adsorption configuration could be inverted in the amorphous TiO2, accounting for the chemo-recognition behavior controlled by the phase of support.

Hierarchical ZnIn2S4 microspheres as photocatalyst for boosting the selective biohydrogenation of furfural into furfuryl alcohol under visible light irradiation

Photocatalyst-enzyme coupling process for visible light driven biotransformation holds promise in producing solar chemicals. In this work, aiming to produce furfuryl alcohol, the important bulk chemical that is typically derived from renewable lignocellulose, a highly selective furfural hydrogenation process is proposed by coordinating the alcohol dehydrogenase with the ZnIn2S4 assistant reduced form of nicotinamide adenine dinucleotid (NADH) regeneration. Results indicated that under visible light irradiation, the hierarchical ZnIn2S4 microspheres exhibited excellent holes and electrons separating efficiency, affording to high NADH regeneration (yield of 90.2±3.28%). When adopting the photo-biocoupled reduction process in furfural transformation, a furfuryl alcohol yield of 79.4±1.95% was achieved under the optimized conditions. The photocatalyst-enzyme coupling process also showed good stability, exceeding 70% of catalytic activity was reserved after reusing the catalysts for 10 cycles. The novel photo-biocoupled system showed promising in extending to the highly selective hydrogenation of other biochemicals from lignocelluloses.

Vegetable oils as Triple Bottom Line compliant lubricants

Metal working fluids represent a threat for workers and for the environment. In this paper an innovative technological and preventive approach is presented relying on the substitution of the base fluids with natural vegetable oil based esters. The results confirmed similar or better technical features of these fluids and a significant reduction of air pollution in particular for polycyclic aromatics.An innovative selective hydrogenation process to improve the oxidative stability of rapeseed oil is also presented. In this way a very significant increase in the oxidative stability of the parent oil, determined by Rotary Bomb Oxidative Test, was observed. The hydrogenated oil is even more stable than High Oleic Sunflower Oil while keeping acceptable cold properties.

Homogeneous-like Alkyne Selective Hydrogenation Catalyzed by Cationic Nickel Confined in Zeolite

The selective hydrogenation of alkynes to their corresponding alkenes is an important type of organic transformation, which is currently accomplished by modified palladium catalysts. Herein, we rep...

The Effect of Addition Method of Impregnation Solution on Properties and Performance of Pd-Ag/Al2O3 Catalyst in Tail-End Acetylene Selective Hydrogenation

The impregnation of alumina support with PdCl2 solution was investigated in batch and semi-batch operation modes using a recycle packed-bed reactor. UV-visible analysis was used to evaluate the kinetics of Pd adsorption on alumina support. Transient palladium adsorption data showed that Pd adsorption was very rapid completing within few minutes. Bi-metallic Pd-Ag/Al2O3 catalysts were synthesized by sequential impregnation method. CO-chemisorption, CO-TPD and FE-SEM tests were used to characterize the synthesized bi-metallic samples. Catalytic performance of the samples was evaluated for tail-end acetylene selective hydrogenation process in a fixed-bed reactor. Moreover, the deactivation of the catalysts was evaluated mathematically by integral method of analysis, considering reaction kinetics as power laws in terms of nth orders in H2 and C2H2 partial pressures. It was observed that by batch-wise addition of Pd precursor solution, a sample was obtained with lowest amount of Pd dimmers that had highest ethylene selectivity and lowest hydrogenation reaction rate.

Selective Hydrogenation of Furfural over the Co-Based Catalyst: A Subtle Synergy with Ni and Zn Dopants.

A multimetal doping strategy has aroused extensive attention in promoting a non-noble catalyst for selective hydrogenation reaction. Herein, a multimetallic catalyst (NiCoZn@CN) with excellent catalytic performance for hydrogenation of furfural (FAL) to furfuryl alcohol (FOL) is prepared through a facile, inexpensive, and efficient pyrolysis method. Using H2 as a H donor, extremely high selectivity (>99%) with 100% conversion is attained over the optimal NiCoZn@CN-600 catalyst. The subtle synergy between Co and Ni, Zn dopants, which remarkably promotes the performance of the Co-based catalyst, is revealed. In the NiCoZn@CN system, Co0 is proven to be the main active site, whose content is greatly improved by Ni and Co dopants. Additionally, the Ni dopant could also benefit activation of H2 and the Zn dopant could enhance metal nanoparticle dispersion and the porous structure of the catalyst. In situ FTIR indicates that the vertical adsorption mode of FAL with the Oaldehyde terminal on NiCoZn@CN-600 ensures a selective hydrogenation process. With a N-doped carbon matrix, NiCoZn@CN-600 shows good cycling stability in five times run. NiCoZn@CN-600 is also competent in the catalytic transfer hydrogenation (CTH) of FOL, affording >99% yield with 2-propanol as a H donor. This study opens an avenue toward rational design of multimetallic doping catalysts with high selectivity for challenging reactions in the conversion of biomass-derived compounds.

Design of hypercrosslinked poly(ionic liquid)s for efficiently catalyzing high-selective hydrogenation of phenylacetylene under ambient conditions

In this study, a series of hypercrosslinked poly(ionic liquid)s (HCPILs) formed from imidazolium tetrachloropalladate were successfully fabricated for selective hydrogenation of phenylacetylene. Its textural properties can be tuned by the different molar ratios of reactants, thereby adjusting its active sites. The synthetic HCPILs were analyzed using various characterization techniques. Due to the constraint of the microporous structure and the charge effect of ionic liquid moieties in the HCPILs, palladium nanoparticles generated from HCPILs were reduced in situ during hydrogenation of phenylacetylene and highly dispersed. Amongst which catalyst a-4 with the largest pore-volume performed the best selectivity (97.3 %) to styrene at 96 % phenylacetylene conversion under the conditions of 308 K and 1 atm H2 pressure. Furthermore, the activity and selectivity of the catalyst did not change considerably in solvents with different polarities. Even after repeated the catalytic experiments for five times, the catalyst displayed no significant loss for activity and selectivity. This work shows industrial application potential and a developing direction in the selective hydrogenation process.

Combined Selective Hydrogenation and Catalytic Cracking Process for Efficient Conversion of Heavy Cycle Oil to High Octane Number Gasoline

Heavy cycle oil (HCO) is difficult to be converted into gasoline via fluid catalytic cracking (FCC) or hydrotreating. Abundant polycyclic aromatic hydrocarbons in HCO lead to condensation coke and ...

Three-Phase Reactor Model for Simulation of Methylacetylene and Propadiene Selective Hydrogenation Process

AbstractIn this study, an effort was performed to improve methylacetylene and propadiene (MAPD) hydrogenation process with investigation of operating conditions which significantly influence the reactor performance. For this purpose, the operational parameters including concentration of components in the feedstock as well as hydrogen and diluent (recycle stream) flow rates were optimized via differential evolution (DE) technique to maximize propylene (PR) production, to minimize green oil formation as well as to control PR selectivity. Then a comparison was made between the optimized and non-optimized (design) conditions. The results indicate that in optimal conditions, PR production rate increases 5.3 ton/day, while the green oil formation as well as propane (PN) production, as unwanted byproducts are reduced to 0.05 and 0.85 ton/day in comparison with the design conditions. Reduction of undesirable byproducts and enhancement of propylene production rate, demonstrate superiority of the optimized conditions to design conditions.