Effect of metal precursors on the performance of Pt/ZSM-22 catalysts for n -hexadecane hydroisomerization

Mild Hydrogenation of 2-Furoic Acid by Pt Nanoparticles Dispersed in a Hierarchical ZSM-5 Zeolite

Hydrogenation of biobased compounds can add value to platform molecules obtained from biomass refining. Herein, we explore the hydrogenation of 2-furoic acid (2-furancarboxylic acid, FCA), a derivative of furfural, with H2 generated in situ by NaBH4 hydrolysis at ambient conditions. Nearly complete conversion of FCA was obtained with tetrahydrofuroic acid (THFA) and 5-hydroxyvaleric acid (5-HVA) as the only two reaction products over Pt nanoparticles supported on hierarchical ZSM-5. Small Pt nanoparticles (2 to 3 nm) were stabilized by ZSM-5 nanosheets. At an optimized Pt loading, the Pt nanoparticles can catalyze the hydrolysis of NaBH4 and the subsequent hydrogenation of FCA with the assistance of Brønsted acid sites. Nanostructuring ZSM-5 into nanosheets and its acidity contributes to the stability of the dispersed Pt nanoparticles. Deactivation due to NaBO2 deposition on the Pt particles can be countered by a simple washing treatment. Overall, this approach shows the promise of mild hydrogenation of biobased feedstock coupled with NaBH4 hydrolysis.

Shape selectivity of zeolite for hydroisomerization of long-chain alkanes

The matching degree between the zeolite channel size and the isomer size determines the product distribution of dodecane hydroisomerization.

Soot Combustion over Cu-Co Spinel Catalysts: The Intrinsic Effects of Precursors on Catalytic Activity

In this work, a series of CuCo₂O₄-x (x = N, A and C) catalysts were synthesized using different metal salt precursors by urea hydrothermal method for catalytic soot combustion. The effect of CuCo₂O₄-x catalysts on soot conversion and CO₂ selectivity in both loose and tight contact mode was investigated. The CuCo₂O₄-N catalyst exhibited outstanding catalytic activity with the characteristic temperatures (T₁₀, T₅₀ and T₉₀) of 451 °C, 520 °C and 558 °C, respectively, while the CO₂ selectivity reached 98.8% during the reaction. With the addition of NO, the soot combustion was further accelerated over all catalysts. Compared with the loose contact mode, the soot conversion was improved in the tight contact mode. The CuCo₂O₄-N catalysts showed better textural properties compared to the CuCo₂O₄-A and CuCo₂O₄-C, such as higher specific surface areas and pore volumes. The XRD results confirmed that the formation of a CuCo₂O₄ crystal phase in all catalysts. However, the CuO crystal phase only presented in CuCo₂O₄-N and CuCo₂O₄-A. The relative contents of Cu²⁺, Co³⁺ and O_ads on the surface of CuCo₂O₄-x (x = N, A and C) catalysts were analyzed by XPS. The CuCo₂O₄-N catalyst displayed the highest relative content of Cu²⁺, Co³⁺ and O_ads. The activity of catalytic soot combustion showed a good correlation with the order of the relative contents of Cu²⁺, Co³⁺ and O_ads. Additionally, the CuCo₂O₄-N catalyst exhibited lower reduction temperature compared to the CuCo₂O₄-A and CuCo₂O₄-C. The cycle tests clarified that the copper-cobalt spinel catalyst obtained good stability. In addition, based on the Mars-van Krevelen mechanism, the process of catalytic soot combustion was described combined with the electron transfer process and the role of oxygen species over CuCo₂O₄ spinel catalysts.

Toward n-Alkane Hydroisomerization Reactions: High-Performance Pt-Al2O3/SAPO-11 Single-Atom Catalysts with Nanoscale Separated Metal-Acid Centers and Ultralow Platinum Content

Long-chain n-alkane hydroisomerization reaction plays a vital role in petrochemical and coal chemical industries, which could produce high-quality hydrocarbon fuels and lubricant base oils for modern transportation and mechanical drive. However, minimizing precious metal usage while maintaining the catalyst performance remains a great challenge. Herein, a novel bifunctional catalyst toward n-alkane hydroisomerization reactions, Pt-Al₂O₃/SAPO-11 (Pt-A/S11) featuring nanoscale separated metal-acid active centers has been synthesized via a simple two-step procedure. In detail, Pt species was first loaded on the nanometer-sized alumina matrices through an incipient wetness impregnation method and then mixed with SAPO-11 molecular sieve to form the composite catalyst. Importantly, 0.015Pt-A/S11 catalyst with the ever-reported lowest Pt loading amount of 0.015 wt % exhibits an extraordinarily high isomer yield of 85.8% compared to previous published results and the traditional Pt-SAPO-11/Al₂O₃ (Pt-S11/A) catalyst accompanying with the direct contact between metal and acid sites (65.6%). It has been confirmed that the Pt species in 0.015Pt-A/S11 samples exist in single-atom form, leading to an excellent hydroisomerization performance. The possible reaction processes have been discussed to elucidate the exemplary catalytic performance of the synthesized Pt-A/S11 catalysts with nanoscale intimacy of metal-acid sites.

Preparation and Performance of the Lipid Hydrodeoxygenation of a Nickel-Induced Graphene/HZSM-5 Catalyst

Graphene-encapsulated nickel nanoclusters are a feasible strategy to inhibit the nickel deactivation of nickel-based catalysts. In this work, graphene-encapsulated catalysts (Ni@C/HZSM-5) were prepared by a compression forming process, using pseudo-boehmite, Al2O3, and ZrO2 as binders. The pseudo-boehmite was gradually transformed from amorphous to crystalline alumina at high temperatures, which destroyed the nucleation of Ni@C. In contrast, the crystal-stabilized zirconia was more favorable for the nucleation of Ni@C. The extensive dispersion of alumina on the surface of HZSM-5 covers the acid sites of HZSM-5. In contrast, when zirconia was used as the binder, the binder existed in the form of the direct aggregation of ~100 nm zirconia spheres; this distribution form reduced better the damage of the binder to the acid site of the catalyst. Furthermore, the particle size of Ni crystals in the graphene-encapsulated catalysts decreased significantly (mostly <11 nm), and no evident agglomeration of nickel particles appeared. It was found that the stabilization of the metal interface delayed, to an extent, the accumulation rate of carbon deposits and, thus, postponed the deactivation of the acid sites. After 8 h of continuous reaction, the conversion of the traditional catalyst Ni/Z5+Zr dropped significantly to 60%. In contrast, the conversion of Ni@C catalysts prepared with ZrO2 remained above 90%. The regeneration test shows that air roasting could effectively remove carbon deposits and restore the catalyst activity.

Hydrogen production from the catalytic dehydrogenation of dodecahydro-N-ethylcarbazole: effect of Pd precursor on the catalytic performance of Pd/C catalysts

In this paper, Pd/C catalysts are synthesized via Ar glow-discharge plasma reduction using activated carbon as the support and Pd(acac)₂, Pd(NO₃)₂, K₂PdCl₄, and H₂PdCl₄ as the Pd precursors, and their catalytic performances are investigated by hydrogen production from dodecahydro-N-ethylcarbazole (H12-NEC). Pd/C-A, prepared from Pd(acac)₂, which has the smallest palladium nanoparticles (1.7 nm), the highest dispersion (34%) and no residue of inorganic ions, exhibits the best catalytic activity with a hydrogen release of 5.28 wt.%, which is 2.2 times that of Pd/C-H. The order of the apparent activation energies of the prepared Pd/C catalysts, according to the kinetics of the H12-NEC dehydrogenation reaction, is as follows: Pd/C-A ≈ Pd/C-N < Pd/C-K < Pd/C-H. When Pd(acac)₂ with a large ligand acts as a cation Pd precursor, the effect of coulombic attraction to Pd²⁺ during the plasma reduction process makes it difficult for Pd nanoparticles (NPs) to migrate, which leads to the formation of ultrafine Pd NPs.

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 (n_Pt/n_A = 0.08 mol/mol, where n_Pt is the number of Pt surface sites and n_A 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 (n_Pt/n_A = 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 n_Pt/n_A 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 n_Pt/n_A 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 n_Pt/n_A 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.

Sinter-resistant platinum nanocatalysts immobilized by biochar for alkane hydroisomerization

The supported platinum nanocatalysts synthesized by the first proposed biochar-assisted strategy exhibited excellent catalytic performance and metal stability in n-alkane hydroisomerization.

Transition Metal Sulfides- and Noble Metal-Based Catalysts for N-Hexadecane Hydroisomerization: A Study of Poisons Tolerance

Bifunctional catalysts on the base of transition metal sulfides (CoMoS and NiWS) and platinum as noble metal were synthesized via wetness impregnation of freshly synthesized Al2O3-SAPO-11 composites, supported with favorable acidic properties. The physical-chemical properties of the prepared materials were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), low-temperature N2 adsorption and high resolution transmission electron microscopy (HR TEM) methods. Catalytic properties were studied in n-hexadecane isomerization using a fixed-bed flow reactor. The catalytic poisons tolerance of transition metal sulfides (TMS)- and Pt-catalysts has been studied for sulfur and nitrogen, with the amount of 10–100 ppm addition to feedstock. TMS-catalysts show good stability during sulfur-containing feedstock processing, whereas Pt-catalyst loses much of its isomerization activity. Nitrogen-containing compounds in the feedstock has a significant impact on the catalytic activity of both TMS and Pt-based catalysts.

Design of Pt/SAPO-11 bifunctional catalyst with superior metal–acid balance constructed via a novel one-step pre-loading strategy for enhancing n-dodecane hydroisomerization performance

This novel pre-loading method is a simple method for the design of bifunctional catalysts with high product yield, which exhibits superior metal–support balance, liquid yield of 99% and isomer yield of 84% on n-dodecane hydroisomerization.

Effect of Metal Precursors on the Performance of Pt/SAPO-11 Catalysts for n-Dodecane Hydroisomerization

Pt(NH₃)₄(NO₃)₂, Pt(NH₃)₄(Ac)₂, (NH₄)₂PtCl₄, and H₂PtCl₆ were used to prepare Pt/SAPO-11 catalysts to investigate the effect of Pt precursors on the hydroisomerization of n-dodecane. The catalyst derived from Pt(NH₃)₄(NO₃)₂ displays the best hydroisomerization activity and selectivity among these precursors. The hydroisomerization conversion of n-dodecane is affected by the platinum particle size, platinum dispersion, the location of platinum, and the valence state of platinum. The selectivity of n-dodecane is determined by the number of Brønsted acid sites and Pt crystal planes. These conclusions are verified by combining transmission electron microscopy, high-resolution transmission electron microscopy, hydrogen temperature programmed reduction, NH₃-temperature programmed desorption, and Py-IR studies. The catalyst prepared with Pt(NH₃)₄(NO₃)₂ as the precursor exhibits the smallest platinum particle size and the highest platinum dispersion. Most of the platinum particles are supported on the external surface of SAPO-11 with the Pt(111) crystal face. Such a catalyst also possesses a suitable number of Brønsted acid sites and then displays the best catalytic performance. Obviously, the use of various precursors for the Pt-based catalyst can significantly affect the performance of Pt/SAPO-11 for the hydroisomerization of n-dodecane.

Bifunctional catalysts for the hydroisomerization of n-alkanes: the effects of metal–acid balance and textural structure

The summary of recent advances reveals excellent potentials for the preparation of novel bifunctional catalysts with excellent catalytic performances for n-alkane hydroisomerization.

New trends in tailoring active sites in zeolite-based catalysts

This review discusses approaches for tailoring active sites in extra-large pore, nanocrystalline, and hierarchical zeolites and their performance in emerging catalytic applications.

Catalytic Hydroisomerization of Long-Chain Hydrocarbons for the Production of Fuels

Hydroisomerization of long chain paraffins for the production of branched alkanes has recently been intensively studied due to a large availability of these compounds. The most interesting research topics have been the development of novel bifunctional catalysts to maximize the yield of isomers and to suppress the cracking reactions. Since both of these reactions are catalyzed by Brønsted acid sites, the optimum catalyst exhibits equal amounts of metal and acid sites, and it facilitates rapid mass transfer. Thus, several hierarchical and nano-shaped zeolites have been developed, in addition to composite catalysts containing both micro- and mesoporous phases. In addition to catalyst development, the effect of the reactant structure, optimal reaction conditions, catalyst stability and comparison of batch vs continuous operations have been made.

Enhanced n-dodecane hydroisomerization performance by tailoring acid sites on bifunctional Pt/ZSM-22 via alkaline treatment

Acidity controlled Pt/ZSM-22 catalysts for n-dodecane hydroisomerization were explored through a simple and efficient post-treatment with different NaOH concentrations, and then the resulting samples were characterized.

Acidic Mesoporous Zeolite ZSM-5 Supported Cu Catalyst with Good Catalytic Performance in the Hydroxysulfurization of Styrenes with Disulfides

Development of highly active heterogeneous catalysts is an effective strategy for modern organic synthesis chemistry. In this work, acidic mesoporous zeolite ZSM-5 (HZSM-5-M), acidic-free mesoporous zeolite TS-1 (TS-1-M), and basic ETS-10 zeolite supported metal Cu catalysts were prepared to investigate their catalytic performances in the hydroxysulfurization of styrenes with diaryl disulfides. The effect of pore size and acidities of the supports, as well as the Cu species electronic properties of the catalysts on reaction activity were investigated. The results show that Cu⁺ and Cu²⁺ binded on HZSM-5-M show the highest activity and product selectivity for the desired β-hydroxysulfides compounds.

Acidic hierarchical zeolite ZSM-5 supported Ru catalyst with high activity and selectivity in the seleno-functionalization of alkenes

The acidic hierarchical zeolite ZSM-5 (HZSM-5-H) was synthesized for preparation of a supported Ru catalyst that was applied in the eleno-functionalization of alkenes with high efficiency.

Controllable deposition of Pt nanoparticles into a KL zeolite by atomic layer deposition for highly efficient reforming of n-heptane to aromatics

Small-sized Pt particles inside KL zeolite channels are supposed to facilitate the dehydrogenation and cyclization of n-heptane.

Synthesis of a multi-branched dandelion-like SAPO-11 by an in situ inoculating seed-induced-steam-assisted conversion method (SISAC) as a highly effective hydroisomerization support

A dandelion-like SAPO-11 with multiple branches was fabricated by seed-induced-steam-assisted conversion, which combined an in situ inoculating seed method (the initial gel pre-crystallized at 433 K for 24 h) and steam-assisted conversion process.