Hydroisomerization Of N-heptane Research Articles

Synthesis of bimetallic Ni-Pt/SAPO-11 composite and the catalytic application in n-heptane hydroisomerization

The monometallic Pt/SAPO-11 and bimetallic Ni-Pt/SAPO-11 catalysts were synthesized with Instant Exactness Synthesis (IES) method and characterized by XRD, nitrogen adsorption–desorption, SEM, TEM, FT-IR, Py-IR, NH3-TPD and XPS, and their properties were evaluated for the n-heptane hydroisomerization. The catalysts had spherical structure and moderate acid strength, and exhibited good n-heptane conversion and catalytic selectivity toward n-heptane isomers. Typically, Ni-Pt/SAPO-11 exhibited an isomer selectivity of 80.9% with a conversion of 69.9% at 310 °C, which was obviously better than Pt/SAPO-11 (isomer selectivity of 75.1% with a conversion of 60.6% at 310 °C). Moreover, the Ni-Pt/SAPO-11 catalyst displayed higher percentage of i-heptane (79%) and lower percentage of n-heptane (6%) than Pt/SAPO-11. The continuous test of 360 min indicated Ni-Pt/SAPO-11 catalyst had good catalytic stability. Bimetallic Ni-Pt alloy loaded on SAPO-11 had significantly effect on catalytic properties of n-heptane hydroisomerization.

Unusual roles of ceria as the support of a single-atom catalyst in hydroisomerization of n-heptane: Phase boundary acts as transport channels between different active centers

Hydroisomerization of n-alkanes plays an important role in fuel and lubricants processing. Bifunctional catalysts with ultralow platinum loading have recently been reported successively for hydroisomerisation. Herein, the catalysts were prepared successfully with different methods to improve the catalytic performance. The conversion of 0.01%Pt1@CeOx/SAPO-11 prepared by co-calcination method (0.01%Pt1@CS-c) is 71.4%, 25% higher than the other prepared by precipitation method. The turnover frequency per active surface platinum site (TOFPt) of 0.01%Pt1@CS-c is as high as 13115 h–1. Revealed by the X-ray photoelectron spectroscopy (XPS) results, the quality of phase boundary/intersurface between ceria and zeolite is found significantly different. The conjunction quality of phase boundary directly affects the spillover rate of intermediate species, which further leads to an apparent activity difference. In addition, the possible role of ceria in the reaction is discussed, rather than just as a carrier for the active metal atoms.

Enhanced hydroisomerization of n-heptane over bifunctional catalysts with highly dispersed Pd nanoparticles supported on H-Yβ composite zeolite

Enhanced catalytic hydroisomerization efficiency and iso-alkanes selectivity by exploring the bifunctional zeolite-supported metal catalysts at the nanoscale are of great important in petrochemical and coal chemical industries. Herein, we develop a simple two-step strategy for introducing intracrystalline and intercrystalline mesopores in H-Yβ by in-situ compositing and loading Pd nanoparticles (NPs, ∼2.2 nm) through an incipient wetness impregnation process followed by mild oxidation–reduction treatment. Especially, the Pd@H-Yβ catalyst with synergistic acid sites and highly dispersed Pd NPs inherits the large surface area, high crystallinity and graded mesoporous channels, and strong thermal and hydrothermal stability. As a demonstration, Pd@H-Yβ with extremely low Pd NPs loading amount of 0.2 wt% used for catalytic hydroisomerization of n-heptane (n-C7) by cascade dehydrogenation and hydrogenation on Pd NPs and isomerization on accessible acid sites, and exhibits an extraordinarily yield of i-heptane (i-C7,74.7 %) compared to the conventional Pd@H-Y (49.1 %) and Pd@H-β (33.7 %) at 280 °C for 3 h under 1 MPa initial hydrogen pressure (IHP). Furthermore, first-principle calculations reveal that the high catalytic activity of Pd@H-Yβ originates from the active hydrogen (H…H and/or H+) transfer by the facile H2 dissociation. The diffusion limitations of intermediates and secondary cracking reactions are effectively weakened due to intrinsic mesoporous channels in Pd@H-Yβ, which still maintains high catalytic activity after 5 times recycles. These findings provide a rational design strategy of bifunctional catalysts with adjustable metal–acid active sites for low-molecular reactants hydroisomerization in industrial application.

Study on the preparation and n-heptane isomerization performance of MoOx-Pd/Ce-MCM-48 catalyst.

A Ce-MCM-48 molecular sieve was prepared by the hydrothermal synthesis method. Using Ce-MCM-48 as the support, a series of MoOx Pd/Ce-M catalysts were prepared by the impregnation method by introducing MoOx and Pd. XRD, N2 adsorption desorption, SEM, TEM, NH3-TPD, Py-IR, FT-IR, and ICP-MS were used to characterize the physicochemical properties. The performance of n-heptane isomerization in a micro fixed bed device was evaluated. The results showed that the synthesized Ce-MCM-48 was mesoporous, with a spherical particle morphology, a long-range ordered pore structure, weakly acidic sites on the surface, and an increase of B and L acids. The 2% MoOx-Pd/Ce-M catalyst was used for the probe reaction of n-heptane hydroisomerization; when the reduction temperature was 400 °C, the reduction time was 2 hours, the reaction temperature was 300 °C, the WHSV was 7.6 h-1, the conversion rate was 58.7%, the selectivity was 91.2%, and the maximum yield was 53.5%. The product distribution of multiple C7 isomers increased the selectivity of multi branched isoheptane. The addition of an appropriate amount of MoOx would improve the performance of n-heptane isomerization.

Experimental and Kinetic Study of the Catalytic Behavior of Sulfate-Treated Nanostructured Bifunctional Zirconium Oxide Catalysts in n-Heptane Hydroisomerization Reactions

In this study, a mono-functional ZrO2 nanomaterial was treated with sulfur and loaded with two different percentages of platinum metals (i.e., 0.5 and 1 wt%) to generate an acidic bi-functional Pt/SZrO2 nanocatalyst for the purpose of increasing the catalytic activity and selectivity together. This work aims to determine the least amount of the costly platinum metal that can be added to the catalyst to achieve the appropriate balance between the acidic and metallic sites. Both rapid deactivation of the super-acid nanaocatalyst and fast cleavage of the zero-octane n-heptane chain can consequently be prevented throughout the reaction. This can be achieved by accelerating the hydroisomerization reactions at a pressure of 5 bar to reach the highest selectivity towards producing the desired multi-branched compound in fuel. Several characterization techniques, including XRD, SEM, EDX, BET, and FTIR, have been used to evaluate the physical properties of the catalysts. The best reaction product was obtained at 230 °C compared to the other tested temperatures. The conversion, selectivity, and yield of reaction products over the surfaces of the prepared catalysts followed this order: 0.5 wt% Pt/SZrO2 > 1 wt% Pt/SZrO2 > 0.5 wt% Pt/ZrO2 > 1 wt% Pt/ZrO2 > SZrO2 > ZrO2. The highest conversion, selectivity, and yield values were obtained on the surface of the 0.5 wt% Pt/SZrO2 catalyst, which are 69.64, 81.4 and 56.68 wt%, respectively, while the lowest values were obtained on the surface of the parent ZrO2 catalyst, which are 43.9, 61.1 and 26.82, respectively. The kinetic model and apparent activation energies were also implemented for each of the hydroisomerization, hydrogenation/dehydrogenation, and hydrocracking reactions, which track the following order: hydroisomerization < hydrogenation/dehydrogenation < hydrocracking. The lowest apparent activation energy value of 123.39 kJ/mol was found on the surface of the most active and selective 0.5% Pt/SZrO2 nanocatalyst.

The Synthesis of a Pt/SAPO-11 Composite with Trace Pt Loading and Its Catalytic Application in n-Heptane Hydroisomerization

n-Alkane hydroisomerization over bifunctional catalysts is an effective approach for clean fuel production. However, achieving metal–acid synergy and enhancing the catalytic performance by the preparation of bifunctional catalysts with suitable proximity between the metal sites and Brønsted acid sites are still challenging. In this work, a series of Pt/SAPO-11 catalysts with different Pt loading applied in n-heptane hydroisomerization was synthesized. SAPO-11 was synthesized by the Instant Exactness Synthesis (IES) method, which, with unique morphology and pore structure, was chosen as support for the hydroisomerization catalysts; Pt/SAPO-11 was synthesized with the impregnation method, Pt nanoclusters with trace loading were fabricated over the SAPO-11 support, and the as-synthesized catalysts with different Pt loading were labeled as xPt/SAPO-11 (x = 0.1, 0.3, 0.5, 0.8 and 1.0). Various characterizations, including XRD, nitrogen adsorption–desorption, SEM, TEM, NH3-TPD and XPS, were carried out on catalysts to obtain deep insights into the microstructure and valence states of xPt/SAPO-11. The catalytic performance of xPt/SAPO-11, including catalytic selectivity and conversion, was investigated in the n-heptane hydroisomerization in detail. Pt loading affected the catalytic properties of xPt/SAPO-11 in the hydroisomerization of n-heptane. The selectivity of 0.5Pt/SAPO-11 toward isomers was about 65% with a conversion of 77% at 310 °C, which was obviously higher than other xPt/SAPO-11 catalysts.

Synthesis of ZSM-22 with Enhanced Acidity Using Alcoholamine as a Structure-Directing Agent to Promote the Hydroisomerization of n-Heptane

The physiochemical properties and catalytic performance of zeolite rely on the judicious selection of organic structure-directing agents (OSDAs), among which alcoholamines are rarely used. Here, we report that 6-amino-1-hexanol (AH) can be used as an OSDA for the generation of commercially viable ZSM-22 with a Si/Al ratio window of 35–150. Compared with ZSM-22 derived from commonly used 1,6-diaminohexane (DAH), the samples generated using AH possess improved crystallinity and more intermediate-to-strong acid site, which can be attributed to the stronger host–guest interactions between AH and zeolite framework. In addition, the crystallization process can be accelerated by the use of AH. ZSM-22 catalysts derived from AH outperform the counterpart generated from DAH in hydroisomerization of n-heptane, and improved catalytic activity and isomer yield can be achieved thanks to the presence of abundant acid sites and high crystallinity.

Modeling and Simulation of the Isomerization of n-Heptane over a Molybdenum Oxycarbide Catalyst for Elucidation of the Bifunctional Mechanism

In this work, the rates of reaction in the hydroisomerization of n-heptane over a molybdenum oxycarbide catalyst were formulated in terms of the transition state theory by applying the single-event kinetic modeling approach. The isomerization reaction was carried out between 603 and 643 K at 18.5 bar on a feedstock of n-heptane (8.3 mol %) and hydrogen (91.7 mol %). A bifunctional mechanism was shown to predominate at the rather high reaction temperature, and the reaction network was described by a bifunctional mechanism using 16 independent kinetic parameters, obtaining a good reproduction of the experimental data. On the acid sites, elementary steps such as (de)protonation, PCP isomerization, β-scission, methyl shift, and hydride shift were taken into account. On the metal sites, (de)hydrogenation and hydrogenolysis were accounted for. By applying the model to the simulation of a fixed bed reactor, an optimum volumetric yield of 95.43 vol % with an RON increase of 36.7 was obtained at 643.15 K. The low cracking selectivity of molybdenum oxycarbide makes it a potential catalyst for the isomerization of n-heptane and heavier paraffins.

Experimental and Kinetic Study of the Effect of using Zr- and Pt-loaded Metals on Y-zeolite-based Catalyst to Improve the Products of n-heptane Hydroisomerization Reactions

The escalating cost of Pt metal has prompted researchers to incorporate other metals into Pt/catalysts to reduce the amount of Pt. In this work, several bimetallic Pt-Zr/HY-zeolite catalysts were prepared by incorporating small amounts of the inexpensive Zr into the Pt/HY-zeolite to form an active and selective catalyst. Results showed that although half of the required platinum metal was used, the catalytic activity of the prepared Pt-Zr/HY bimetallic catalyst was higher than that of the monometallic (Pt or Zr)/HY catalysts, as a result of the improved Lewis acidity of that catalyst that resulted from the addition of the Zr metal; additionally, the branched alkanes' yield also increased. The optimum catalyst was bimetallic, containing 0.5 wt% Pt + 0.5 wt% Zr, which achieved the highest yield of isomers at 70.2 mol%, along with 82.61 and 84.98 mol% for conversion and selectivity, respectively, under 1 MPa and 250°C reaction conditions. In addition, the hydroisomerization reaction kinetic model was achieved, giving good predicted results in agreement with the experimental calculations, with an acceptable relative error. It was found that lower activation energies (about 44.5 kJ/mol) were needed for olefin hydrogenation to iso-paraffins, while higher activation energies were required for i-paraffin hydrocracking (about 138.1kJ/mol).

Hydroisomerization of n-Heptane in a Fixed-Bed Reactor Using a Synthesized Bimetallic Type-HY Zeolite Catalyst

The synthesis of NaY-zeolite was performed hydrothermally. The preparation of the bifunctional catalysts was achieved by loading NH4Y-zeolite with a cheap Zr metal, as a second loading metal, with tiny amounts of Pt to compose a Pt-Zr/Y-zeolite catalyst. Different characterization methods (i.e., XRD, SEM, EDX, BET, and AFM) were used to investigate the catalyst properties. The catalytic performance was studied by performing the hydroisomerization of n-heptane in a gas phase at a temperature of 275°C and atmospheric pressure in a fixed-bed reactor. The GC-FID results of the products confirmed the positive role of Zr in enhancing the catalytic features, as reflected by the increase in the isomerized products and the decrease in the unwanted by-products. Incorporating 1.0wt%Zr with 1.0wt% of Pt significantly improved the activity and selectivity and increased the yield of branched alkanes. This was achieved because the addition of zirconium provided an extraordinary Lewis acidity to the zeolite-framework structure and simultaneously took advantage of the electronic and catalytic properties of Zr and Pt metals to enhance its novel catalytic features. This reduced the amount of Pt metal and halved the cost of the catalyst. In addition, the bimetallic catalyst (HY-zeolite loaded with 1wt%Pt & 1wt%Zr) achieved values of 74.2, 78.8, and 58.5mol% for conversion, selectivity, and yield, respectively. The conversion was improved to a level close to 2wt% Pt/HY-zeolite catalyst, while selectivity was not significantly decreased from that of 2wt% Zr/HY-zeolite catalyst, reaching a yield level of isomers close to that of 2wt% Pt/HY-zeolite catalysts.

Promoting hydroisomerization selectivity using channel axis reduced ZSM-48 fabricated by a combined bead-milling and porogen-assisted recrystallization method

ZSM-48 is a unidimensional zeolite that is frequently used as acid component of bi-functional hydroisomerization catalyst. As selectivity towards unwanted cracking products increases with retention time of isomerized products inside micropores, shortening their retention time inside the micropores by reducing channel length offers an effective way to improve isomerization selectivity. Direct synthesis of unidimensional zeolitic crystals with reduced channel axis is particularly difficult, since they habitually grow into rod-like shape along their channel direction. Post-synthetic bead-milling is a cost effective, mechanochemical method to decrease crystal size of zeolites from micro meter to nano meter scale, but suffers from amorphization or partial destruction of zeolitic crystals. Consequently, a post-milling recrystallization process is often entailed to remedy the destructed domains, which, nonetheless, readily causes secondary crystal growth and formation of bulky crystals that compromises the effect of bead-milling. Here, we show that porogen-assisted recrystallization can overcome the problem to fabricate channel axis reduced ZSM-48 nanocrystals. The Si/Al ratio is tunable between 30 and 200 and the acidity is largely preserved after recrystallization. The catalytic advantages of the obtained material are demonstrated in catalytic n-heptane hydroisomerization. The obtained ZSM-48 nanocrystal with Si/Al ratio of 100 outperforms the rest samples and shows enhanced isomerization yield (72% vs 62%) with respect to the parent sample. By combined diagnoses of the impact of diffusion length on product selectivity (product shape selectivity) and kinetic studies, selectivities to monomethyl branched isomers (2-methyl hexane and 3-methyl hexane) and small bulky dimethyl branched isomers (2,3- and 2,4-dimethyl pentane) are attributed to product shape selectivity, whereas the formation to bulky dimethyl branched isomers (2,2- and 3,3-dimethyl pentane) is hindered mainly by transition-state shape selectivity. The combined destructive-constructive synthetic protocol and the revelation of the origin of shape-selectivity in n-heptane hydroisomerization are useful for hydroisomerization catalyst design.

Modification of SBA-15 mesoporous silica as an active heterogeneous catalyst for the hydroisomerization and hydrocracking of n-heptane.

In this study, a mesoporous SBA-15 silica catalyst was prepared and modified with encased 1% platinum (Pt) metal nanoparticles for the hydrocracking and hydroisomerization of n-heptane in a heterogeneous reaction. The textural and structural characteristics of the nanostructured silica, including both encased and non-encased nanoparticles, were measured using small-angle X-ray diffraction (XRD), nitrogen adsorption-desorption porosimetry, Brunauer–Emmett–Teller (BET) surface area analysis, Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Catalytic testing was carried out in a plug-flow reactor under highly controlled operating conditions involving the reactant flow rate, pressure, and temperature. Gas chromatography was used to analyze the species as they left the reactor. The results demonstrated that 1% Pt/SBA-15 has a high n-heptane conversion activity (approximately 85%). Based on the results of this experimental work, there is no selectivity in the SBA-15 catalysts for isomerization products because they are inactive at the relatively low temperature that is essential for hydroisomerization. On the other hand, the SBA-15 catalysts have a considerable selectivity for products that have cracks, owing to their ability to withstand extremely high temperatures (300–400 ​°C) as well as the availability of Lewis acid sites within the catalyst structure.

Generating TON zeolites with reduced [0 0 1] length through combined mechanochemical bead-milling and porogen-directed recrystallization with enhanced catalytic property in hydroisomerization

Mechanochemical bead-milling of micron-meter sized zeolites to nanometers provides an effective route to enhance their diffusion and catalytic properties. This post-synthetic method is particularly important to reduce crystals of unidimensional zeolites preferentially along their channel direction, as direct synthesis is difficult to achieve since they habitually grow into rod-like crystals. The milling process is often escorted by surface amorphorization and structure degradation, hence, a subsequent recrystallization is often entailed to restore crystallinity. Herein, taken ZSM-22 as an example, it is demonstrated that secondary crystal growth and coalescence during recrystallization, a process that often offset the effect of milling, could be suppressed by the introduction of porogens in the post-milling recrystallization process. The combined bead-milling and porogen-directed recrystallization method allows the preparation of highly crystalline TON crystals with an axis length of largely 100–300 nm, which is record short in axis [001] channel length. The Si/Al ratio could be manipulated between 40 and 300, permitting the influence of acidity and diffusion to be evaluated. The catalytic assessments in n-heptane hydroisomerization demonstrate that isomer yields can be enhanced from 56% for parent material to up to 74% for an optimized catalyst with Si/Al of 200. Correlating of zeolite structure, kinetic studies and catalytic behavior discloses that low acid site density and improved diffusion property are critical factors to decrease cracking probability and improve isomerization selectivity. This study opens new ways to tailor diffusion properties of unidimensional zeolites, and are potentially extendable to other zeolites.

Investigation of n-heptane hydroisomerization over alkali-acid-treated hierarchical Pt/ZSM-22 zeolites

Various hierarchical structures and morphologies of Pt/ZSM-22 zeolites are attempted through a post-treatment using alkali-acid to achieve better performance for n-heptane hydroisomerization.

PtSn supported on hierarchical mesoporous SAPO-11: Synthesis, characterization and catalytic evaluation in n-heptane hydroisomerization

Traditional microporous SAPO-11 molecular sieve was synthesized in Al2O3-P2O5-Dipropylamine-H2O system. To improve the mesoporosity aiming to overcome the diffusion limitations of zeolite, Hierarchical mesoporous SAPO-11 molecular sieve was synthesized via adding SAPO-11 seed into the Al2O3-P2O5-Dipropylamine-H2O system. Nitrogen physisorption analysis indicated that the synthesized SAPO-11 via seeding approach has additional mesoporosity with a mesopore volume of 0.11 cm3/g and average pore diameter ∼ 4 nm. Also, HR-TEM analysis proofed the formation of hierarchical mesoporous SAPO-11 as spherical aggregate particles in contrast to rectangular block crystals in the form of large particle aggregates showed by traditional micro-SAPO-11. To investigate the effect of the created mesoporosity on the catalytic performance toward n-heptane hydroisomerization, Hierarchical mesoporous SAPO-11support was employed to prepare PtSn (x) bimetallic bifunctional catalysts. Compared to PtSn(2)/micro-SAPO-11 catalyst, the PtSn(2)/meso‑ SAPO-11 catalyst exhibited higher isomerization selectivity, attributed to their excellent diffusion properties resulting from the hierarchical pore network, which is beneficial for catalytic reactions.

Promotional Effect of Pd Addition on the Catalytic Activity of Composite Pt-Pd/AlSBA-15–β Catalyst for Enhanced n-Heptane Hydroisomerization

Hierarchical AlSBA-15–zeolite materials were utilized as a supports for preparing hydroisomerization catalysts. Detailed consideration was given to: (i) the effect of the zeolite type introduced into AlSBA-15–zeolite composites (where zeolite is β, mordenite or ZSM-5) as well as (ii) the promotion effect of Pd addition. The composites showed higher activity in isomerization as compared to Pt/AlSBA-15. The enhanced isomerization efficiency were explained by the appropriate metallic and acidic function as well as suitable transport properties. The modification of the hydrogenating function by Pd incorporation increases the hydroisomerization efficiency of Pt-Pd/AlSBA-15–β catalyst. Over bimetallic Pt-Pd/AlSBA-15–β, the high yields of isomers (68 wt%) with respect to 50 wt% for a control catalyst. The most promising Pt-Pd/AlSBA-15–β catalyst allows to improve research octane number from 0 to the 74 value.

Control and Impact of Metal Loading Heterogeneities at the Nanoscale on the Performance of Pt/Zeolite Y Catalysts for Alkane Hydroconversion.

The preparation of zeolite-based bifunctional catalysts with low noble metal loadings while maintaining optimal performance has been studied. We have deposited 0.03 to 1.0 wt % Pt on zeolite H-USY (Si/Al ∼ 30 at./at.) using either platinum(II) tetraammine nitrate (PTA, Pt(NH3)4(NO3)2) or hexachloroplatinic(IV) acid (CPA, H2PtCl6·6H2O) and studied the nanoscale Pt loading heterogeneities and global hydroconversion performance of the resulting Pt/Y catalysts. Pt/Y samples prepared with PTA and a global Pt loading as low as 0.3 wt % Pt (nPt/nA = 0.08 mol/mol, where nPt is the number of Pt surface sites and nA is the number of acid sites) maintained catalytic performance during n-heptane (T = 210–350 °C, P = 10 bar) as well as n-hexadecane (T = 170–280 °C, P = 5 bar) hydroisomerization similar to a 1.0 wt % Pt sample. For Pt/Y catalysts prepared with CPA, a loading of 0.3 wt % Pt (nPt/nA = 0.08 mol/mol) sufficed for n-heptane hydroisomerization, whereas a detrimental effect on n-hexadecane hydroisomerization was observed, in particular undesired secondary cracking occurred to a significant extent. The differences between PTA and CPA are explained by differences in Pt loading per zeolite Y crystal (size ∼ 500 nm), shown from extensive transmission electron microscopy energy-dispersive X-ray spectroscopy experiments, whereby crystal-based nPt/nA ratios could be determined. From earlier studies, it is known that the Al content per crystal of USY varied tremendously and that PTA preferentially is deposited on crystals with higher Al content due to ion-exchange with zeolite protons. Here, we show that this preferential deposition of PTA on Al-rich crystals led to a more constant value of nPt/nA ratio from one zeolite crystal to another, which was beneficial for catalytic performance. Use of CPA led to a large variation of Pt loading independent of Al content, giving rise to larger variations of nPt/nA ratio from crystal to crystal that negatively affected the catalytic performance. This study thus shows the impact of local metal loading variations at the zeolite crystal scale (nanoscale) caused by different interactions of metal precursors with the zeolite, which are essential to design and synthesize optimal catalysts, in particular at low noble metal loadings.

Influence of Nanoscale Intimacy and Zeolite Micropore Size on the Performance of Bifunctional Catalysts for n-Heptane Hydroisomerization.

In this study, Pt nanoparticles on zeolite/γ-Al2O3 composites (50/50 wt) were located either in the zeolite or on the γ-Al2O3 binder, hereby varying the average distance (intimacy) between zeolite acid sites and metal sites from “closest” to “nanoscale”. The catalytic performance of these catalysts was compared to physical mixtures of zeolite and Pt/γ-Al2O3 powders, which provide a “microscale” distance between sites. Several beneficial effects on catalytic activity and selectivity for n-heptane hydroisomerization were observed when Pt nanoparticles are located on the γ-Al2O3 binder in nanoscale proximity with zeolite acid sites, as opposed to Pt nanoparticles located inside zeolite crystals. On ZSM-5-based catalysts, mostly monobranched isomers were produced, and the isomer selectivity of these catalysts was almost unaffected with an intimacy ranging from closest to microscale, which can be attributed to the high diffusional barriers of branched isomers within ZSM-5 micropores. For composite catalysts based on large-pore zeolites (zeolite Beta and zeolite Y), the activity and selectivity benefitted from the nanoscale intimacy with Pt, compared to both the closest and microscale intimacies. Intracrystalline gradients of heptenes as reaction intermediates are likely contributors to differences in activity and selectivity. This paper aims to provide insights into the influence of the metal–acid intimacy in bifunctional catalysts based on zeolites with different framework topologies.

Bifunctional molybdenum oxide/acid catalysts for hydroisomerization of n-heptane

Numerus research studies focus on replacing scarce noble metals by non-noble transition metals in solid catalysts. The (de)hydrogenation function in bifunctional catalysts for hydroisomerization and hydrocracking of alkanes is usually performed by a precious metal such as Pt, or a metal sulfide such as MoS2. In this study, we investigated the possibility of replacing Pt with a non-sulfided MoOx catalyst in combination with a mesoporous solid acid for the hydroisomerization of n-heptane. MoOx particles size as well as the preparation techniques were varied in order to identify the Mo active phase for (de)hydrogenation. We demonstrated that an optimized non-precious metal MoOx catalyst can perform similarly to its Pt counterpart in the n-heptane conversion when used in combination with a mesoporous solid acid.

N-Heptane Hydroisomerization over a SO42–/ZrO2@SAPO-11 Composite-Based Catalyst Derived from the Growth of UiO-66 on SAPO-11

A novel SO42–/ZrO2@SAPO-11 (SZ@SA-11) composite was synthesized via a two-step method, and the corresponding SZ@SA-11 supported Pt catalyst was applied to catalyze n-heptane hydroisomerization. Fir...