Selective Hydrogenation Of Benzene Research Articles

Origin of the Increase in the Selectivity of Ru Catalysts with the Addition of Amines in the Presence of ZnSO4 for the Selective Hydrogenation of Benzene to Cyclohexene

The synthesis of nylon 6 and nylon 66 can be performed, starting with the selective hydrogenation of benzene to cyclohexene, which is deemed to be environmentally friendly and cost-saving and to have higher atom efficiency. Nano-Ru catalyst was synthesized via a precipitation method. The prepared catalyst was evaluated in the selective hydrogenation of benzene toward cyclohexene generation in the presence of ZnSO4 in a liquid batch reactor. The promotion effect of the addition of amines, i.e., ethylenediamine, ethanolamine, diethanolamine, and triethanolamine, was investigated. The fresh and spent catalysts were thoroughly characterized by XRD, TEM, AES, N2-sorption, FT-IR, and TPR. It was found that the addition of amines could significantly improve the catalytic selectivity toward cyclohexene formation in the presence of ZnSO4. This was attributed to the formation of (Zn(OH)2)5(ZnSO4)(H2O)x (x = 0.5, 3 or 4) through the reaction between ZnSO4 and the amines, which could be chemisorbed on the Ru surface. This led to retarding the formation of cyclohexane from the complete hydrogenation of benzene and, thus, increased the catalytic selectivity toward cyclohexene synthesis. Therefore, with the presence of ZnSO4, the amount of chemisorbed (Zn(OH)2)5(ZnSO4)(H2O)x increased with increasing amounts of added amines, leading to a decline in the catalytic activity toward benzene conversion and selectivity toward cyclohexene generation. When 7.6 mmol of diethanolamine and 10 g of ZrO2 were applied, the highest cyclohexene yields of 61.6% and 77.0% of benzene conversion were achieved over the Ru catalyst. Promising stability was demonstrated after six runs of catalytic experiments without regeneration. These achievements are not only promising for industrial application but also beneficial for designing other catalytic systems for selective hydrogenation.

Crystal facet-controlled brookite TiO2 nanostructures coupled with Ru nanoparticles for enhancing selective hydrogenation of benzene to cyclohexene

Coupling active metal nanoparticles (NPs) with oxide nanocrystals enclosed by specific facets is a promising strategy to enhance their catalytic performances. Here, brookite TiO2 nanoplates exposed with {11 1¯} facets, nanorods enclosed by {121} facets, and nanosheets exposed with {211} facets were synthesized and coupled with Ru NPs, aiming at improving their catalytic efficiency in selective hydrogenation of benzene to cyclohexene (SHBC) and discriminating the critical roles of brookite facets. The comprehensive characterizations recognized that the successive exposure of brookite TiO2 {11 1¯}, {121}, and {211} facets resulted in a more suitable adsorption strength of C6H6 and an increment of chemisorption capacity of C6H6 on medium-strength acid sites, contributing to a promotion of the turnover frequency (TOF) of C6H6. The kinetics investigations, density functional theory (DFT) simulations, and Mulliken population analysis unveiled that the increased Ti3+ species as a result of the successive exposure of brookite TiO2 {11 1¯}, {121}, and {211} facets brought in an increment of the net production rate of C6H10 in SHBC, and the electronic interaction between C6H10 and these facets is gradually weakened, which contributed to an improvement of C6H10 selectivity. As a consequence, an initial C6H10 selectivity (S0) of 91 % and a C6H10 yield of 47 % achieved on the brookite TiO2-supported Ru catalyst enclosed by TiO2 {211} facets.

Ru-Loaded Biphasic TiO2 Nanosheet-Tubes Enriched with Ti3+ Defects and Directionally Deficient Electrons as Highly Efficient Catalysts in Benzene Selective Hydrogenation

Crystalline phase engineering is a prominent strategy for synergistically optimizing the surface–body phases of a catalyst. In this work, TiO2 nanosheets assembled into nanotubes (TNSTs) with two phases, anatase and rutile, were firstly synthesized via crystal engineering by simple thermal annealing. These were subsequently loaded with Ru nanoparticles, with a mean size of 5.0 nm, to create the efficient benzene hydrogenation catalyst Ru/TNSTs. The well-designed nanosheet-tube structure boasts a large specific surface area and excellent transmission channels, which effectively prevents the agglomeration and deactivation of loaded Ru nanoparticles, as well as promoting the internal diffusion in the reaction process of benzene hydrogenation to cyclohexene. Furthermore, titanium dioxide nanosheet-tubes contain numerous Ti3+ defects, which not only improves the overall conversion rate of cyclohexene but also enhances the suppression of cyclohexene adsorption. Most importantly, the titanium dioxide with its two-phase composition of 75 wt% anatase and 25 wt% rutile increases the ratio of electron deficiencies of Ru and promotes cyclohexene desorption. These synergistic properties enhance the selectivity and efficiency of the Ru/TNSTs catalysts, resulting in excellent performance in the hydrogenation of benzene to cyclohexene. In particular, the Ru/TNSTs-4 catalyst (annealed for 4 h), under the specific conditions of 140 °C temperature and 5 MPa hydrogen pressure for the hydrogenation process, achieves a 95% initial selectivity and 51% yield of cyclohexene in the reaction, outperforming most supported Ru-based catalysts. This work may provide new perspectives for designing efficient benzene hydrogenation catalysts via crystalline phase engineering.

Novel Reaction-Adsorption Method for Preparation of Ru–Zn–La/ZrO2 Catalysts with High Catalytic Performance for Selective Hydrogenation of Benzene

A novel wet-chemistry reaction-adsorption strategy via the facile acid–base interaction under mild conditions is demonstrated to fabricate the state-of-the-art Ru–Zn–La/ZrO2 catalysts for selective hydrogenation of benzene to cyclohexene. The catalyst preparation process is systematically investigated and verified with the combination of various characterization techniques. Preloading of lanthanide salts and alkali treatment after calcination not only favor the introduction of ruthenium and zinc species in the later stages but also help enhance the dispersion of the catalysts. The reaction rate constants (k1 and k2) decrease with the increment of the Zn/Ru molar ratio, and the selectivity at 40% conversion (S40) is positively correlated with the k1/k2 ratio, demonstrating the role of Zn species in retarding the hydrogenation activity of Ru and improvement of the selectivity to cyclohexene. In general, the catalytic behavior is dependent on the particle size of Ru, the La-to-Ru electron transfer effect, the content of Zn species, and the surface hydrophilicity of catalyst. These factors are generated by using different precursors and various predesigned La/Ru molar ratios in the preparation recipe. Moreover, a passivation treatment before the hydrogenation reaction can promote the cyclohexene selectivity of the catalyst Ru–Zn–La/ZrO2 (1.6 La/Ru) to 80.6% at a benzene conversion of 43.7%, which meets the industrial requirement. Notably, the specific activity of the catalyst is as high as 1224 gBZ·gRu–1·h–1, over 10 times higher than the industrial criterion. This work provides new insights into the design of Ru-based catalysts for benzene hydrogenation and other hydrogenation reactions as well.

Preparation of Ruthenium Hollow Spheres as Catalysts for Selective Hydrogenation of Benzene to Cyclohexene

In this paper, a simple and effective method was used to synthesize monodisperse metal Ruthenium nanospheres (Ru-HNSs), and the silicon dioxide (SiO2) nanospheres synthesized by Stober method were used as hard templates. The surface of SiO2 was double modified by γ-aminopropyltriethoxysilane (KH550) and salicylaldehyde, so that Ru3+ grew uniformly on the surface of modified SiO2 and reduced to form a stable and durable layer of Ru metal. Then the hard template SiO2 was corroded by chemical etching to obtain Ru-HNSs hollow spheres. The results show that the diameter of SiO2 microspheres was about 300nm, the wall thickness of Ru-HNSs was about 3nm, and the diameter was about 100nm.

Investigation on Ru–Pd/Al2O3 Catalyst for Deep Removal of Sulfur Compounds Potentially Used in the Process of Selective Hydrogenation of Benzene to Cyclohexene

Investigation on Ru–Pd/Al2O3 Catalyst for Deep Removal of Sulfur Compounds Potentially Used in the Process of Selective Hydrogenation of Benzene to Cyclohexene

Regulating Surface‐Interface Structures of Zn‐Incorporated LiAl‐LDH Supported Ru Catalysts for Efficient Benzene Hydrogenation to Produce Cyclohexene

AbstractIn the heterogeneous catalysis, adsorption and desorption behaviors of reactants and products on the surface of catalysts can remarkably impact their catalytic activities and product selectivities. Here, series of Ru‐based catalysts supported on Zn‐incorporated Li−Al layered double hydroxides (Ru/LDH) were developed and employed in the selective benzene hydrogenation to produce cyclohexene without the use of any additional zinc salt additives. It was demonstrated that as‐constructed supported Ru catalyst bearing a Zn/(Li+Zn) molar ratio of 0.075 in the LDH support gave a higher cyclohexene yield of 43.2 % than those over other Ru‐based ones. Combining structural characterizations and catalytic hydrogenation reactions with temperature‐programmed desorption and in situ Fourier transform infrared spectroscopy of benzene and cyclohexene, it was revealed that the generation of appropriate surficial/interfacial Ru0/Ruδ+−O−Zn structures, as well as the existence of abundant hydroxyl groups on LDH supports, could facilitate the benzene adsorption and the cyclohexene desorption, thereby remarkably promoting the formation of cyclohexene. The present findings not only give a profound insight into the roles of surface‐interface structures of supported Ru catalysts for efficient benzene hydrogenation to produce cyclohexene but also simultaneously provide a promising guide to design high‐performance Ru‐based catalysts.

Catalyst Design for Selective Hydrogenation of Benzene to Cyclohexene through Density Functional Theory and Microkinetic Modeling

Catalyst Design for Selective Hydrogenation of Benzene to Cyclohexene through Density Functional Theory and Microkinetic Modeling

Hydrogenation of a Benzene‐Toluene Mixture Using Metal Nanoparticles Stabilized by a Hyper‐Crosslinked Aromatic Polymer

AbstractHydrogenation of aromatic compounds is a widely used catalytic process in modern industry. Selective hydrogenation of benzene (BZ)‐toluene (TL) mixtures is an important industrial process as it allows the purification of BZ for further synthetic purposes. In this work, the hydrogenation of a BZ‐TL mixture (at a molar ratio close to 1) was studied for varying reaction parameters (temperature in the range of 100–180 °C and pressure in the range of 1–7 MPa) using Pt‐, Pd‐, and Ru‐containing nanoparticles stabilized by an amino‐functionalized hyper‐crosslinked aromatic polymer (HAP). Among the synthesized catalytic systems, Ru/HAP containing ruthenium(IV) oxide was shown to be the most active and selective one, allowing 44 % selectivity with respect to cyclohexane at nearly 100 % of BZ conversion.

Optimization of Solvent and Extractive Distillation Sequence Considering Its Integration with Reactor

The integration of reaction and extractive distillation system is beneficial for reducing the process cost. A systematic method is proposed to identify the optimal solvent, solvent-to-feed ratio, extractive distillation sequence and reactor operating conditions based on the integration of reactor and extractive distillation. The non-key component matrix method is used to generate the extractive distillation sequences. The proposed method can be used to evaluate different solvents, solvent-to-feed ratios, as well as the extractive distillation sequences; the optimal extractive distillation parameters corresponding to the minimum total annualized cost (TAC) can be identified considering different operating conditions. For the selective hydrogenation of benzene to cyclohexene process, the minimum total annualized cost of unit desired product, 4.01 $·kmol−1, is achieved when the reactor’s inlet temperature is 333 K, solvent N-Formylmorpholine and sequence S2 are employed, and the solvent-to-feed ratio is 4.

Selective hydrogenation of benzene over Ru supported on surface modified TiO2

A series of catalysts with ruthenium nanoparticles (NPs) loaded on the binary oxide TS (TiO2-SiO2) support were prepared by facile sol-gel method for benzene selective hydrogenation. Different mole ratios of Ti/Si were investigated. The catalytic structure, composition, hydrophilicity, electronic state and acidity were characterized. The results indicate that the acidity of the samples increases gradually with the increase of the SiO2 amount. The dispersion of ruthenium nanoparticles was improved on binary oxide support compared with TiO2 and an obvious Ru size effect appeared with the increase of Ti/Si molar ratio. It was also found that the hydrophilicity of the supports could be efficiently improved by introducing a small amount of SiO2 to TiO2, which may be due to the large amount of surface hydroxyl groups on the binary oxide samples after SiO2 introduction. This result was consistent with the increasing trend of cyclohexene yield, indicating that the surface hydroxyl groups play a significant role in the motivation of cyclohexene desorption. Ru/TS (7: 1) showed the best catalytic performance of 38.2% yield to cyclohexene with the highest initial selectivity to cyclohexene (S0) of 87.3%. The catalytic stability experiments showed that the yield of cyclohexene could maintain at 30% after five cycles.

Влияние способа приготовления катализатора Au-Rh / ASA на реакцию гидрирования бензола

Бензол мен толуолдың жоғары меншікті бетке ие аморфты синтетикалық алюмосиликат (ASA, саудалық атауы Siral-40) тасымалдағышына отырғызылған родий және алтын катализаторын қолданып, этанолда, сутек қысымында гидрлену нәтижесі салыстырылды. Катализаторлар екі түрлі әдіспен дайындалды: ылғал сыйымдылығы бойынша сіңіру және коллоидтық әдіс. Сондай-ақ, катализаторлар сіңдіру арқылы екі нұсқада дайындалды: родий мен алтын тұздарын бір уақытта сіңдіру және алдымен бір металдың тұзын, содан кейін екінші металды ретімен сіңіру. Катализаторлар индуктивті байланысқан плазма-оптикалық эмиссиялық спектроскопия (ICP-OES) әдісімен зерттелді. Бензолды селективті гидрлеу үшін ылғал сыйымдылығы бойынша сіңдіру арқылы дайындалған катализаторлар ең тиімді екендігі анықталды. Катализатордың белсенділігі катализатор бетіндегі бензол мен толуолды белсендіру үшін қатетті родий мөлшеріне байланысты. Коллоидтық әдіспен дайындалған катализаторларда белсенді родий металы кеуектердің ішіне еніп, алтын катализатордың бетінде қалатындықтан оның белсенділігі төмен, ал сіңдіру арқылы дайындалған катализаторлардың бетіндегі родий мөлшері теориялық мүмкіндікке жақын. Аталмыш соңғы катализаторда толуол қатысында бензолды гидрлеудің селективтілігі 84% құрайды.

Ru/TiO2 catalyst for selective hydrogenation of benzene: Effect of surface hydroxyl groups and spillover hydrogen

Three Ru/TiO2 catalysts were prepared via an impregnation-chemical reduction method by supporting Ru on three different TiO2 supports, namely TiO2-A (anatase), TiO2-R (rutile) and TiO2-A-750 (annealing TiO2-A at 750 °C). The amount of surface hydroxyl groups in the TiO2 supports and Ru/TiO2 catalysts is evaluated by the FTIR technique, which is found to be affected by crystal and textural property of TiO2. It is found that, for the Ru/TiO2 catalyst, the presence of more spillover hydrogen, and more hydroxyl groups that lead to stronger surface hydrophilicity and lower benzene diffusion rate, thereby improve its catalytic activity and selectivity towards selective hydrogenation of benzene. For the Ru/TiO2-A catalyst, it has much more spillover hydrogen and hydroxyl groups than the other two, hence showing the best catalytic activity (TOF of 0.8 s−1) and cyclohexene selectivity (66%) at a benzene conversion of 50%.

Promoting the Performances of TiO2 Submicrosphere-Embedded Ru Nanoparticles in Benzene Selective Hydrogenation by Morphology Manipulation

We embedded Ru nanoparticles into mesoporous TiO2 submicrospheres (MTSSs) with tunable morphologies for benzene selective hydrogenation (BSH). It was identified that the TiO2 precursor prepared by ...

Activity and Stability Evaluation of Nickel Supported over Al‐Meso‐Microporous Hybrids in Selective Hydrogenation of Benzene

AbstractBenzene selective hydrogenation has very important due to the need to reduce the carcinogenic effects of benzene as a toxic and volatile compound and production of cyclohexane as a green solvent for the production of nylons. Nickel loaded composites were prepared by the wet‐impregnation method. These catalysts were characterized using Fourier‐transform infrared, X‐ray powder diffraction, scanning electron microscope, and N2 adsorption‐desorption techniques. The aim of this study is to evaluate the catalytic performance as a function of zeolite nature, reaction temperature and relative pressure of the reactants. The obtained results confirm that the nickel nanoparticles supported on Al‐MCF‐Zeolites hybrids have acceptable performance. Also, the best activity and high selectivity were obtained for Ni/Al−M‐MOR at all temperatures (150‐210 °C) and Ni/Al−M‐13X about 83% at 170 °C.

Selective benzene reduction from gasoline using catalytic hydrogenation reactions over zeolite Pd/13X

In this study, the selective hydrogenation of benzene in a mixture of benzene and normal heptane was investigated by 13X zeolite modified with Pd as catalyst (Pd/13X). The modification of 13X zeolite was carried out using a specified amount of Pd (NO3)2 in the solution and the experimental tests were conducted in the catalyst evaluation set-up (Cata-test). The characterizations of 13X and Pd/13X were studied by XRD, FTIR, SEM, TEM and BET. Several variables affecting the catalyst performance such as temperature, pressure, WHSV and H2/HC mole ratio were investigated and optimized. It was found that the conversion of benzene was equal to 95% at the operating conditions of T = 200 °C, p = 1 MPa, WHSV = 20 h−1 and H2/HC molar ratio of 1.3.

Electrospun Immobilized Ruthenium Salen Complex on FeNi3 Nanofiber for Selective Hydrogenation of Benzene to Cyclohexene

Electrospun Immobilized Ruthenium Salen Complex on FeNi3 Nanofiber for Selective Hydrogenation of Benzene to Cyclohexene

Selective Hydrogenation of Benzene: Progress of Understanding for the Ru-Based Catalytic System Design

Selective hydrogenation of benzene toward cyclohexene is an economically interesting and technically challenging reaction, and catalytic system design is the kernel for selective hydrogenation of b...

Engineering the exposed facets and open-coordinated sites of brookite TiO2 to boost the loaded Ru nanoparticle efficiency in benzene selective hydrogenation

Engineering the crystal facets and the proportion of edge and corner atoms of brookite TiO2 to expose more coordinatively unsaturated (cus) atoms and open-coordinated sites is of significant importance in boosting the loaded metal nanoparticle (NP) efficiency in heterogeneous catalysis, but suffering tremendous challenge owing to the low structural symmetry and thermodynamic metastability of brookite TiO2. Herein, we prepared brookite TiO2 with nanoflower (NF), nanorod (NR), and nanosheet (NS) shapes, which increased in the catalytically active cus Ti atoms on high-energy facets and the open-coordinated sites on edge and corner atoms. These increments were found to boost the loaded Ru NPs efficiency in selective hydrogenation of benzene to cyclohexene both in activity and selectivity. Combined with comprehensive characterizations, the increased turnover frequency of benzene was ascribed to the increment in the amount and strength of benzene adsorbed on the above catalytically active sites of brookite TiO2, which reacted with spillover hydrogen (Hso) dissociated from Ru NPs. For the improvement in cyclohexene selectivity, it was speculated to be originated from the elevation of the hydrogenation rate constant ratios of benzene to cyclohexene and cyclohexene to cyclohexane steps and the acceleration of cyclohexene desorption once it is formed on the catalyst by the cus Ti atoms and the open-coordinated sites on brookite TiO2.

Ru nanoparticles on TiO2 with various anatase-to-rutile ratios tuned by selective chemical dissolution: Effect of support polymorph composition on selective benzene hydrogenation

Using P25 TiO2 as the precursor, phase-pure anatase and rutile TiO2 as well as TiO2 with tunable anatase-to-rutile molar ratios (nA/nR) were prepared via a facile “selective chemical dissolution” approach. The Ru/TiO2 catalysts were then synthesized and comprehensively characterized by spectroscopic techniques and transmission electron microscopy. It is confirmed that these catalysts possessed similar physicochemical parameters and hydrophilicity, but different Ru sizes (2.3–4.5 nm). Ru nanoparticles (NPs) supported on TiO2 with nA/nR of 2.66 (Ru/TiO2-1.5%HF) exhibited moderate size of 3.4 nm and electron-deficient state, which was originated from the unique Ru-on-anatase/rutile junction structure. In selective benzene hydrogenation, the turnover frequencies of benzene of the mixed phase TiO2-supported Ru catalysts were similar irrespective of the nA/nR ratios and ranged between phase-pure anatase and rutile TiO2-supported Ru catalysts, which can be ascribed to the size effect of Ru. For the cyclohexene selectivity, Ru NPs supported on TiO2 with nA/nR of 0.88–2.66 exhibited higher S0 (92–95%) than Ru NPs on TiO2 with other nA/nR ratios, in which the Ru/TiO2-1.5%HF catalyst displayed a maximum of 95%. We demonstrated that in addition to the proper Ru size, the electron-deficiency of Ru on the Ru/TiO2-1.5%HF catalyst contributed greatly to the highest selectivity since it can promote the desorption of cyclohexene to avoid suffering over-hydrogenation.