Isobutane/2-Butene Alkylation Using Large-Pore Zeolites: Influence of Pore Structure on Activity and Selectivity

Catalytic performance and industrial test of HY zeolite for alkylation of naphthalene and α-tetradecene

The service life of HY zeolite is 480 h under industrial conditions, and it can be regenerated by roasting.

Preparation of CuHY catalyst via solid-state ion exchange method and its catalytic performance in isobutane/2-butene alkylation

CuHY samples prepared by solid-state ion exchange of HY zeolite with CuCl were used as catalysts in isobutane/2-butene alkylation. The results show that both the addition amount of CuCl and the calcination temperature affect the ion exchange degree. Cu⁺ can be introduced into Y zeolite by replacing H⁺ in the HY zeolite after the solid-state ion exchange, causing a decrease of the amount of Brønsted acid sites and an increase of that of Lewis acid sites. When taking CuHY as the catalyst in isobutane/2-butene alkylation, the 3d¹⁰4s⁰ valence electron configuration of Cu⁺ makes it favorable for inhibiting the oligomerization of 2-butene and accelerating the hydride transfer reaction rate by indirectly increasing the local isobutane/olefin ratio around the acid sites of the catalyst. As a result, the selectivity of C8 and trimethylpentanes over CuHY in alkylate are improved compared with those of HY.

Efficient continuous-flow synthesis of long-chain alkylated naphthalene catalyzed by ionic liquids in a microreaction system

A microreaction system for the synthesis of long-chain alkylated naphthalene is presented, indicating a high yield of alkylated naphthalene (>99%) could be obtained in 60 s at mild temperature (30 °C) within 5 cycles of ionic liquid catalyst reuse.

The Role of CO2 as a Mild Oxidant in Oxidation and Dehydrogenation over Catalysts: A Review

Carbon dioxide (CO2) is widely used as an enhancer for industrial applications, enabling the economical and energy-efficient synthesis of a wide variety of chemicals and reducing the CO2 levels in the environment. CO2 has been used as an enhancer in a catalytic system which has revived the exploitation of energy-extensive reactions and carry chemical products. CO2 oxidative dehydrogenation is a greener alternative to the classical dehydrogenation method. The availability, cost, safety, and soft oxidizing properties of CO2, with the assistance of appropriate catalysts at an industrial scale, can lead to breakthroughs in the pharmaceutical, polymer, and fuel industries. Thus, in this review, we focus on several applications of CO2 in oxidation and oxidative dehydrogenation systems. These processes and catalytic technologies can reduce the cost of utilizing CO2 in chemical and fuel production, which may lead to commercial applications in the imminent future.

A facile way to improve zeolite Y-based catalysts' properties and performance in the isobutane-butene alkylation reaction

Different amounts of SiO₂ were added to the Al₂O₃ binders to investigate the binder effect on zeolite Y-based catalysts. The added SiO₂ improved the mesopore volume and acidity of the catalysts. Characterization results showed that the catalysts' acid amount increased with increasing the SiO₂ amount in the binder, which achieved maximum value when 12% SiO₂ was added to the binder. The doped SiO₂ in Al₂O₃ binders improved the Al₂O₃ phase transformation temperature, which is crucial for Al species to break out of the phase energy and migrate into the zeolite. The lifetime of catalyst Y-Al₂O₃-12SiO₂ is 3.7 times higher than that of Y-Al₂O₃-0SiO₂, and the selectivity of the target products simultaneously improved by 7 percentage point. This work should bring some inspiration to the design and application of zeolite-based catalysts.

Mechanism of byproducts formation in the isobutane/butene alkylation on HY zeolites

Submicron-size HY zeolites with a particles size of 200–700 nm were synthesized employing a crystal precipitation method in this study. The catalytic activity for the isobutane/butene alkylation was evaluated. The results indicated that butene conversion was above 90% and the selectivity of expected products (C8) was nearly at 90% within 72 h. The micropores-blocking and coverage of acid sites resulting from high hydrocarbons increased the difficulty for the diffusion of products to the bulk and inhibited the adsorption of reactant on activity sites, which caused deactivation of catalyst. The ultimate C12 content in alkylate oil, stemmed from trimerization of butene, was reduced via the addition reaction with butene to C16 and the cracking to C5–C7. The formation mechanisms and transformation processes of byproducts in alkylate oil revealed that the source of C9–C11 switched from cracking of C16+ to the addition of C5–C7 carbocations with butene when acid sites concentration was reduced by accumulating oligomers.

Submicron-size HY zeolites with a particles size of 200–700 nm were synthesized employing a crystal precipitation method in this study.

Shape-selective methylation of naphthalene with methanol over SAPO-11 molecular sieve modified with hydrochloric acid and citric acid

Herein, a series of SAPO-11 molecular sieves were modified by hydrochloric acid and citric acid.

Solid acids: potential catalysts for alkene–isoalkane alkylation

Production of high-octane gasoline is important to improve upon the performance and hence economics of oil companies worldwide.

Adsorption Kinetics at Silica Gel/Ionic Liquid Solution Interface

A series of imidazolium and pyridinium ionic liquids with different anions (Cl(-), Br(-), BF₄(-), PF₆(-)) has been evaluated for their adsorption activity on silica gel. Quantification of the ionic liquids has been performed by the use of RP-HPLC with organic-aqueous eluents containing an acidic buffer and a chaotropic salt. Pseudo-second order kinetic models were applied to the experimental data in order to investigate the kinetics of the adsorption process. The experimental data showed good fitting with this model, confirmed by considerably high correlation coefficients. The adsorption kinetic parameters were determined and analyzed. The relative error between the calculated and experimental amount of ionic liquid adsorbed at equilibrium was within 7%. The effect of various factors such as initial ionic liquid concentration, temperature, kind of solvent, kind of ionic liquid anion and cation on adsorption efficiency were all examined in a lab-scale study. Consequently, silica gel showed better adsorptive characteristics for imidazolium-based ionic liquids with chaotropic anions from aqueous solutions in comparison to pyridinium ionic liquids. The adsorption was found to decrease with the addition of organic solvents (methanol, acetonitrile) but it was not sensitive to the change of temperature in the range of 5-40 °C.

Synthesis of methylal from methanol and formaldehyde catalyzed by Brønsted acid ionic liquids with different alkyl groups

The carbon chain length of ILs has an effect on its catalytic activity. The ionic liquid of [C₆ImBS][HSO₄] shows the best catalytic performance which is near that of concentrated sulfuric acid and p-toluene sulfonic acid.

Studies on Synthesis and Properties of Hydrophobic Brønsted Acidic Ionic Liquid

A hydrophobic Brønsted acidic ionic liquid 1-octyl-3-(butyl-4-sulfonate) imidazolium hydrogen sulfate ([BsImR8][HSO4]) was synthesized and characterized by fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), electron spray ionization mass spectrometry (ESI-MS) and thermogravimetry (TG). [BsImR8][HSO4] was used as an efficient catalyst for esterification of oleic acid with methanol to biodiesel. It was founded that [BsImR8][HSO4] exhibited high catalytic activity, which is near to that of H2SO4.It was ascribed to its strong Brønsted acidity. The catalyst could maintain high activity after five cycles of use.

Probing the Structural and Electronic Factors Affecting the Adsorption and Reactivity of Alkenes in Acidic Zeolites Using DFT Calculations and Multivariate Statistical Methods

Quantum mechanical (QM) cluster calculations have been performed on a model of ZSM-5 at DFT and MP2 levels. We investigated how the adsorption energies and the energetics of alkoxide intermediate formation of six different alkene substrates, ethene, propene, 1-butene, cis/trans butene, and isobutene, vary in this zeolite model. An analysis of the DFT geometric, electronic, and energetic parameters of the zeolite-substrate complexes, transition states, and alkoxide intermediates is performed using principal components analysis (PCA) and partial least squares (PLS). These deliver an insight into the correlated changes that occur between molecular structure and energy along the reaction coordinate between the physisorbed and chemisorbed species within the zeolite. To the best of our knowledge, this is the first occasion multivariate techniques such as PCA or PLS have been employed to profile the changes in electronics, distances, and angles in QM calculations of catalytic systems such as zeolites. We find the calculated adsorption and the alkoxide intermediate energies correlate strongly with the absolute charge on the substrate and the length of the substrate double bond. The transition states' energies are not affected by the zeolite framework as modeled, which explains why they correlate strongly with the gas-phase substrate protonation energy. Our cluster results show that for ethene, propene, 1-butene, and isobutene, the relative energetics associated with the formation of the alkoxide intermediate in ZSM-5 follow the same trends as calculations where the effects of the framework are included.