Liquid-phase Alkylation Of Benzene Research Articles

Synthesis of Modified Catalyst for Liquid Phase Alkylation of Benzene with Ethylene

Highly efficient binder-free catalysts, based on zeolite Y, for the liquid-phase alkylation of benzene with ethylene have been synthesized. The catalysts have been modified by treating with aqueous solutions of hydrochloric and citric acids to remove extra-framework aluminum formed during the partial dealumination of zeolite Y. The synthesized catalysts have been tested in the alkylation of benzene with ethylene at a temperature of 200°C, a pressure of 2.5 MPa, a benzene : ethylene molar ratio of 5 : 1, and a benzene feed space velocity of 5 h−1. Over the modified catalyst, the ethylbenzene (EB) content in the alkylate increases by 27% and the EB selectivity increases by 5% compared to the initial Y zeolite.

MCM-56 stabilization synthesis using auxiliary tetraethylammounium ions: Its role to inhibit surface Si-O-Al bridged linkage and retain highly delaminated structure

MCM-56 is one important member of MWW type zeolites, which possesses an unique 2D framework structure consisting of one or two MWW monolayers. Due to its high external surface area and large external acid concentration, MCM-56 zeolite exhibits excellent potential catalytic performance in alkylation of aromatics. However, it's a transient product and momentarily convert into MCM-49 zeolite. Herein, we present a facile strategy for stable synthesis of highly delaminated MCM-56 zeolite, denoted MCM-56(D), by using the dual-template system composed of hexamethyleneimine (HMI) and tetraethylammonium hydroxide (TEAOH). The characteristics of extended stable period and higher delamination degree distinguish MCM-56(D) from traditional MCM-56. The phase stabilization period is prolonged by two days or more, which is dependent on the increase of TEAOH amount. The results indicate that HMI acts as a directing agent to promote crystallization of MWW topology, while TEAOH has been proven to be a crystallization regulator by hindering Si-O-Al bridges formation in interlayers, thus forming a highly exfoliated MCM-56(D). Compared with the traditional MCM-56, the external surface area and mesoporous volume (213.6 m2/g, 1.20 cm3/g) of MCM-56(D) increased by more than 60% and 183%, respectively, naturally possessing more accessible Brønsted acid sites favourable for bulky molecule reaction, so it shows a high conversion in cracking of 1, 3, 5-triisopropylbenzene. In the liquid-phase alkylation of benzene with ethylene, MCM-56(D) performs higher reactivity and slower deactivation than MCM-22 and MCM-49 under a WSHV (Ethylene) of 2 h−1. This dual-template method ensures MCM-56(D) a practicable catalyst for processing bulky molecules in petrochemical industry.

Development of a Catalyst and a Process for Liquid-Phase Benzene Alkylation with Ethylene and the Ethane–Ethylene Hydrocarbon Pyrolysis Fraction

The base catalyst HY-BS, which is binder-free zeolite Y in the acid H+ form, has been synthesized and modified with hydrochloric and citric acid solutions. It has been shown that all the obtained catalysts exhibit high activity and selectivity in the reaction of liquid-phase alkylation of benzene with ethylene. It has been first found that the ethylbenzene concentration in the alkylate and the selectivity for ethylbenzene in the liquid-phase benzene alkylation reaction on the catalyst modified with 0.3 N hydrochloric acid are higher when either the hydrogenated or the nonhydrogenated ethane–ethylene fraction of pyrolysis is used as an alkylating agent instead of polymerization-grade ethylene.

Effect of zeolite pore morphology on solvent-less alkylation of benzene with 1-hexene

In an attempt to convert the carcinogenic benzene which is almost restricted for its use in gasoline, alkylation reaction with olefin 1-hexene has been conducted on various zeolites. Four zeolites having different pore topology and pore size have been applied as solid acid catalysts for effective production of alkylate in a liquid phase, solvent-less low temperature reaction. The textural properties of all the four zeolites (ZSM-5, MOR, BEA, HY) have been characterized for crystal morphology by TEM, crystal structure by XRD and FTIR, BET for surface area, N2 sorption for porosity and TPD for acidity. Among the zeolite, BEA possessed high surface area (600.61 m2/g) and enhanced meso pores volume (0.3956 cm3/g) as compared to other zeolite samples. The performance of BEA was also observed to be superior in the liquid phase alkylation of benzene with 1-hexene in a batch reactor under autogenous pressure without using any solvent. At the optimum reaction conditions, the benzene conversion was 86.6 wt% and 3-Phenylhexane, 2-Phenylhexane yield were about 47.9 wt% and 38.7 wt% respectively on this catalyst. The BEA also exhibited longer time-on-stream and reusability performance, thus offers an attractive route for converting benzene into valuable (3-Phenylhexane, 2-Phenylhexane) alkylate product useful for the manufacturing of fine chemicals, dyestuff, detergents and scents.

Adsorption and catalytic properties of sulfated aluminum oxide modified with cobalt ions

The adsorption properties of sulfated aluminum oxide (9% SO 4 2- /γ-Al2O3) and a cobalt-containing composite (0.5%Сo/SO 4 2- /γ-Al2O3) based on it are studied via dynamic sorption. The adsorption isotherms of such test adsorbates as n-hydrocarbons (C6–C8), benzene, ethylbenzene, chloroform, and diethyl ether are measured, and their isosteric heats of adsorption are calculated. It is shown that the surface sulfation of aluminum oxide substantially improves its electron-accepting properties, and so the catalytic activity of SO 4 2- /γ-Al2O3 in the liquid-phase alkylation of benzene with octene-1 at temperatures of 25–120°C is one order of magnitude higher than for the initial aluminum oxide. It is established that additional modification of sulfated aluminum oxide with cobalt ions increases the activity of this catalyst by 2–4 times. It is shown that adsorption sites capable of strong specific adsorption with both donating (aromatics, diethyl ether chemosorption) and accepting molecules (chloroform) form on the surface of sulfated γ-Al2O3 promoted by cobalt salt.

Shape selectivity of beta and MCM-49 zeolites in liquid-phase alkylation of benzene with ethylene

NH3, pyridine and 2,4,6-trimethyl-pyridine were selected as the base probes to characterize the different pore acidity of H-beta and H-MCM-49 zeolites, revealing the essence in their catalytic performance from the view of shape selectivity in different pore systems. Based on the size of base probes, reactants, product, transition states and pore channels, the difference in catalytic performance over H-beta and H-MCM-49 was investigated. Easy diffusion of reactants into and long diffusion distance for ethylbenzene escaping out of confined space within beta are the main reason for superior activity and poorer ethylbenzene (EB) selectivity. As for H-MCM-49, acid sites located in 10 MR channels contributed little to the formation of EB due to transition state selectivity; Acid sites located in 12 MR cups on the outer surface with little restriction on the diffusion of reactant/product toward/from the active centers were the major active centers for EB formation, which could be detected by 2,4,6-trimethyl-pyridine; There was diffusion limitation on reactant/product in 12 MR supercages through 10 MR windows to influence activity/selectivity. The enhancement in activity and selectivity in liquid-phase alkylation of benzene with ethylene over MWW zeolites should be mainly focused on transforming confined 12 MR supercages into 12 MR cups with improved openness.

Increasing the Efficiency of Liquid Phase Alkylation of Benzene with Propylene Using the Method of Mathematical Modeling

In this study the existing problems of liquid-phase alkylation of benzene with propylene problems are indicated. The paper describes the stages alkylation of benzene with propylene mathematical model development. The model allows to define the composition of the product stream under changing of plant process parameters: temperature, benzene/propylene molar ratio and feed space velocity. The error of the model does not exceed 7.5%. «Alkylation» computer modeling system is developed in Borland Delphi 7 and the optimization module of the process parameters is called «Optimization». In Aspen HYSYS the technological scheme of rectification products alkylation of benzene with propylene using aluminum chloride catalyst was developed. Integration of computer models allowed to determine the technological modes of production, providing isopropylbenzene outlet with higher quality.

Temperature-controlled phase-transfer hydrothermal synthesis of MWW zeolites and their alkylation performances

MWW zeolites have been synthesized with hexamethyleneimine/aniline as the structure-directing/promoting agent. High conversion is achieved in the liquid-phase alkylation of benzene with ethylene above 210 °C for MCM-56.

One-pot synthesis of nano-crystalline MCM-22

Nano-crystalline MCM-22 zeolite was synthesized in a one-pot procedure by the use of an organosilane (dimethyl-octadecyl-(3-trimethoxysilylpropyl)-ammonium chloride, TPOAC) in the zeolite synthesis gel. This crystal growth inhibition procedure introduced mesopores in the MCM-22 crystallites. The lower mechanical stability of the nano-crystalline MCM-22 zeolite compared with bulk MCM-22 can be countered to some extent by pillaring. The increased external surface of the microporous zeolite domains resulted in increased accessibility of the Brønsted acid sites, as followed from the better performance in liquid-phase benzene alkylation with propylene as compared with bulk MCM-22. The increased accessibility of the internal acid sites in Mo-loaded hierarchical MCM-22 was also evident from the improved benzene selectivity during methane aromatization. Silylation of hierarchical Mo/MCM-22 was detrimental for the catalytic performance in MDA. The nano-crystalline MCM-22 has physico-chemical and catalytic properties intermediate between those of MCM-22 and ITQ-2 with the benefit over ITQ-2 that it can be synthesized in a single step.

Simultaneous recrystallization and post-synthesis of MCM-49 zeolite by TEAOH/piperidine: Implication on the acidity and catalytic alkylation performance

Incompletely crystallized MCM-49 was recrystallized and post-synthesized in tetraethylammonium hydroxide solution with piperidine as a protective and structure-directing agent. The morphology of post-synthesized MCM-49 has been tailored from rose-like shape to small MWW sheets packed disorderly. The surface areas have been improved from 387 m2 g−1 (parent MCM-49) to 475 m2 g−1 (TPMP-16) and 492 m2 g−1 (TPMC-16). The number of total acid sites determined by Py-FTIR has been enhanced significantly from 464 μmol g−1 (parent MCM-49) to 873 μmol g−1 (H-TPMP-16) and 780 μmol g−1 (H-TPMC-16). Importantly, post-synthesized catalysts showed superior ethylene conversion and ethylbenzene selectivity during liquid-phase alkylation of benzene with ethylene.

Directing gel: An effective method tailoring morphology of MWW zeolites and their catalytic performance in liquid-phase alkylation of benzene with ethylene

The directing gel method was developed to tailor morphology, textural property, acidity and catalytic performance of MWW catalysts. Directing gel was defined as large amounts of crystal precursors without any typical diffraction peaks corresponding to MWW zeolites. The synthesis of directing gel was stopped at the end of induction period, and then additional materials were added to further crystallization. Via directing gel method, not only did the final MWW zeolites possess high crystallinity, but also the morphology were remarkably changed into irregular MWW sheets packed in disorder, which was completely different from rose-like shape of the reference MCM-22 via conventional hydrothermal synthesis. Besides morphology tailoring, the textural property (esp. external surface area and pore volumes) and acid sites of final MWW zeolites were also improved. The increases of ethylene conversion of directing gel catalysts were attributed to the better accessibility of active centers jointly induced by their morphology, textural property and acidity.

Kinetics of liquid phase alkylation of benzene with dodecene over mordenite

This paper presents the kinetics investigation of liquid phase alkylation of benzene with dodecene using mordenite having Si/Al = 20. The models are developed based on physicochemical characterization of the catalyst and a laboratory scale fixed bed reactor data. The FTIR analysis shows that approximately 90 % of the acidic sites are Brønsted acid type while the remaining 10 % are Lewis acid type. The kinetic experiments are conducted with 6:1 molar ratio of benzene to dodecene at four different temperature levels between 80 to 140 °C. The product analysis shows that the main alkylation product is 2‐phenyldodecane. At lower temperature, the concentration of dodecene isomers is significant. On the other hand at higher temperature linear alkylbenzene isomers are the dominating products. The kinetic models are formulated considering simultaneous dodecene isomerization and benzene alkylation. The reaction rate parameters are estimated by fitting of the experimental data implemented in MATLAB. The adequacy of the estimated model parameters are verified by thermodynamic consistency and statistical fitting indicators. The activation energy for protonation of 1‐dodecene to 2‐dodecene found to be significantly lower (34 kJ/mol) than that of the 2‐dodecene to 3‐dodecene reaction (51 kJ/mol). The activation energies of surface alkylations of benzene to 2‐phenyldodecane and 3‐phenyldodecane are 49 kJ/mol and 66 kJ/mol, respectively.

Enhancing activity without loss of selectivity – Liquid-phase alkylation of benzene with ethylene over MCM-49 zeolites by TEAOH post-synthesis

Abstract As-synthesized and calcined MCM-49 zeolites were post-synthesized by tetraethylammonium hydroxide to tailor their morphology, texture properties, acid sites and catalytic performances. With post-synthesis by tetraethylammonium hydroxide, both as-synthesized and calcined MCM-49 zeolites have showed remarkable morphology change from rose-like shape into disorderly packed irregular MWW sheets, and improved surface areas, pore volumes and acid sites without obvious loss of crystallinity. The samples before and after tetraethylammonium hydroxide treatment were used as catalysts in liquid-phase alkylation of benzene with ethylene. Importantly, a prominent increase in ethylene conversion was observed without loss of ethylbenzene selectivity over post-synthesized MCM-49 catalysts in liquid-phase alkylation of benzene with ethylene.

Positive effect of secondary structure creation in mordenites on alkylation of benzene with 1-tetradecene

The liquid-phase alkylation of benzene with 1-tetradecene was realized over dealuminated mordenites with different mesoporous surface areas and three different levels of acidity. The mordenite catalysts were characterized by N2-sorption, FTIR pyridine adsorption, and TPDA. The number of Brønsted acid sites decreases; however, it represents a higher proportion of the total acidity. Alkylation results demonstrated that the mordenite activity in alkylation accelerated with increasing mesoporous surface area in spite of the lower total acidity. This fact indicates that the accessibility of acid sites and the internal mass transport in mordenite channels play a significant role in liquid-phase alkylation of aromatics with 1-alkenes.

Size-controlled synthesis of MCM-49 zeolites and their application in liquid-phase alkylation of benzene with ethylene

Size-controlled synthesis of MCM-49 zeolites was achieved via topology reconstruction from NaY zeolites with different sizes.

The Application of Silica-Supported Preyssler HPA as a Heterogeneous and Green Catalyst for the Alkylation of Benzene

Liquid-phase alkylation of benzene with 1-decene for the production of linear alkylbenzene (LAB) was investigated with silica-supported Preyssler heteropoly acid as the catalyst. Catalyst loading, Bz/C10 molar ratio, and catalyst weight percentage were investigated. Catalyst with 30% loading, Bz/C10 molar ratio of 17, and catalyst weight percentage of 2.6 showed 1-decene conversion of 100% and 2-phenyl decane selectivity of 27.2% at 80°C and 2-hr reaction.

Benzene reduction in gasoline by alkylation with propylene over MCM-22 zeolite with a different Brønsted/Lewis acidity ratios

In this work, the liquid phase alkylation of benzene with propylene was carried out over MCM-22 zeolite treated thermally in a flow of air and nitrogen for activation. Such activation procedures led to changes in the Brønsted/Lewis acidity ratio of the samples, but not in textural properties. The alkylation reaction was conducted using as a feed a benzene-enriched sample of reformate heart cut containing ca. 20wt% benzene. The experimental reaction was performed in a batch reactor at 220°C adjusting the amount of propylene for a molar ratio of benzene to propylene in the feed of 2. Benzene conversion versus time profiles consisted of three regions wherein (i) the aromatic conversion decreased very slightly, (ii) it diminished drastically, and (iii) it continued dropping with time, but to a lesser extent than in (ii). MCM-22 sample containing a higher Brønsted acidity exhibited a larger resistance to deactivation during benzene alkylation experiments, as severe deactivation starts after 19h of time on stream. Concerning products distribution, the presence of bulky (poly) alkylated products declined as the MCM-22 became more deactivated.

Liquid-phase alkylation of benzene with octenes over Y zeolites: Kinetic modeling including acidity descriptors

A fundamental microkinetic model is presented for the alkylation of benzene with octenes in liquid phase over Y zeolites with Si/Al ratios 5.8, 13, and 30. The model describes simultaneously the olefin isomerization and benzene alkylation reactions on the fresh catalysts, that is, in the absence of coke formation. The reaction mechanism considers adsorbed octenes reacting with benzene from the liquid phase. Protonation of phenyloctanes are considered quasi-equilibrated. Protonation of olefins and surface alkylations are considered as non-quasi-equilibrated. Activation energies of 46kJmol−1 and 70kJmol−1 are obtained for olefin protonation and surface alkylation, respectively. Standard protonation enthalpies of −33kJmol−1 and −92kJmol−1 are obtained for the protonation of 1-octene and 2-phenyloctane, respectively. Introduction of two catalyst descriptors allows to describe the influence of the acid properties of the Y zeolites on conversion and product yields. The concentration of acid sites is obtained from ammonia TPD. The change in standard protonation enthalpy relative to a reference Y zeolite, Δ(ΔHpro), accounts for the effect of the zeolite’s average acid strength on the stability of the intermediates and the activation energies and is estimated by regression to experimental data. For the three Y zeolites, a variation in standard protonation enthalpy of 7kJmol−1 is found.

Liquid-phase alkylation of benzene with ethylene over postsynthesized MCM-56 analogues

MCM-56 analogues were postsynthesized via a mild acid treatment technique from hydrothermally synthesized MCM-22 lamellar precursors with Si/Al ratios of 15–45. The physicochemical properties of MCM-56 were characterized by XRD, SEM, N2 adsorption, XPS, 29Si and 27Al MAS NMR, NH3-TPD and pyridine adsorption IR techniques. In comparison to MCM-22 with 3-dimensional MWW topology, the postsynthesized MCM-56 showed a broad X-ray diffraction of emerged 101 and 102 reflections and possessed a structural disorder along the layer stacking direction. Composed of partially delaminated MWW nanosheets, MCM-56 analogues had a larger external surface than MCM-22. The MCM-56 and MCM-22 catalysts were employed in the liquid-phase alkylation of benzene with ethylene. MCM-56 analogues exhibited a higher yield of ethylated benzenes and a higher catalytic stability than MCM-22, proving to serve as promising solid-acid catalysts for processing bulky molecules in petrochemical industry.

Alkylation of Benzene with 1-Decene Using Silica Supported Preyssler Heteropoly Acid: Statistical Design with Response Surface Methodology

The response surface method (RSM) was applied to study the liquid phase alkylation of benzene with 1-decene catalyzed by means of silica supported Preyssler heteropoly acid. A three step experimental design was developed based on the central composite design (CCD). Catalyst loading, catalyst mass percent, and benzene to 1-decene molar ratio were used to optimize 1-decene conversion and linear alkylbenzene (LAB) yield. The results indicated that the quadratic model was significant for these two responses. The experimental results revealed that all variables had positive effect on 1-decene conversion. While increasing the catalyst loading tends to decrease LAB yield. Benzene to 1-decene molar ratio was found to be the most important factor that influenced LAB yield with a positive effect. Design expert software suggested several optimized solutions, among them the best choice was to use 31% catalyst loading, benzene to 1-decene molar ratio of 13, and catalyst percent of 3.6 wt% for obtaining 100% conversion and 88% LAB production yield.