Diisobutylene Research Articles

A Reduced Kinetics Model for the Oxidation of Transcritical/Supercritical Gasoline Surrogate/Ethanol Mixtures Using Real Gas State Equations

ABSTRACT Efforts to combat the harmful effects of vehicle emissions on our environment and health include exhaust emissions and fuel efficiency regulations. One promising solution is direct fuel injection in supercritical conditions, where the fuel mixture is above critical temperature and pressure. This study presents a reduced kinetics mechanism (129 species and 1015 reactions) utilizing real gas equations to simulate the combustion of supercritical/transcritical gasoline surrogate/ethanol blends. It was developed by combining two reduced models – a Toluene reference fuel (TRF) with a Diisobutylene (DIB) and an ethanol model – and validated through simulations of ignition delay time (IDT). The Arrhenius parameters of key reactions for each fuel component were modified to improve accuracy. An adjusted Redlich-Kwong cubic state equation was employed to segregate each surrogate mixture tested as supercritical, transcritical, or subcritical. The new mechanism was then validated against experimental results using high-pressure conditions and the cubic Peng-Robinson and Redlich-Kwong equation of state parameters. Critical properties of each species were obtained through Joback’s Group Method and the Ambrose-Walton vapor pressure equation. The TRF/DIB/E mechanism results were consistent with shock tube experimental data at high pressure, indicating a potential for modeling combustion in ultra-high pressure direct injection engines.

ANN for the prediction of isobutylene dimerization through catalytic distillation for a preliminary energy and environmental evaluation

<abstract> <p>This study aimed to develop an artificial neural network (ANN) capable of predicting the molar concentration of diisobutylene (DIB), 3, 4, 4-trimethyl-1-pentene (DIM), and tert-butyl alcohol (TBA) in the distillate and residue streams within three specific columns: reactive (CDC), high pressure (ADC), and low pressure (TDC). The process simulation was conducted using DWSIM, an open-source platform. Following its validation, a sensitivity analysis was performed to identify the operational variables that influenced the molar fraction of DIB, DIM, and TBA in the outputs of the three columns. The input variables included the molar fraction of isobutylene (IB) and 2-butene (2-Bu) in the butane (C4) feed, the temperature of the C4 and TBA feeds, and the operating pressure of the CDC, ADC, and TDC columns. The network's design, training, validation, and testing were performed in MATLAB using the Neural FittinG app. The network structure was based on the Bayesian regularization (BR) algorithm, that consisted of 7 inputs and seven outputs with 30 neurons in the hidden layer. The designed, trained, and validated ANN demonstrated a high performance, with a mean squared error (MSE) of 0.0008 and a linear regression coefficient (R) of 0.9946. The statistical validation using an analysis of variance (ANOVA) (<italic>p</italic>-value > 0.05) supported the ANN's capability to reliably predict molar fractions. Future research will focus on the in-situ validation of the predictions and explore hybrid technologies for energy and environmental optimization in the process.</p> </abstract>

Low carbon energy technologies envisaged in the context of sustainable energy for producing high-octane gasoline fuel

With increasing issues, concerning the depletion of petroleum fossil fuels and the environment, various researchers have examined an innovative and appropriate surrogated fuel. Various advanced countries maximize alternative fuel to fight against atmospheric alteration. In this perspective, the current research aims to introduce low-carbon energy technologies envisaged in the context of sustainable energy for generating high-octane gasoline fuel. Four gasoline feedstocks were selected for investigation in the present research as materials. Particularly, these components are gasoline additives, such as bioethanol (E), di-isobutylene (DIB), and dimate (D) with baseline motor gasoline stream, like hydrocracked gasoline (HG). To execute the present work, several gasoline fuels and experimental facilities that correspond to European standard regulations were employed. Additionally, the composition of the optimum sample was 50 % of hydrocracked gasoline, 35 % of bioethanol, 10 % of di-isobutylene, as well as 5 % of dimate. Therefore, the optimal gasoline blend provided high-octane gasoline RON 98 with great ecological characteristics. Besides, the experimental results displayed that the antidetonation performance can be varied consecutively as bioethanol > di-isobutylen > dimate > hydrocracked gasoline by octane number. What’s more, the simultaneous incorporation of bioethanol, di-isobutylene, and dimate changed antiknock characteristics, in terms of vapor pressure, the distillation curve, as well as the density in a route that could impact engine operation. Conclusively, the acquired results stated that it might be merits to utilize bioethanol to provide the added value of hydrocracked gasoline, di-isobutylene, and dimate to establish an innovative high gasoline product in RON of 98 considered the restrictions for high olefins content.

Methoxycarbonylation of diisobutylene into methyl isononanoate catalyzed by cobalt complexes supported with porous organic polymers

Porous organic polymers (POLs) bearing pyridine or imidazole onto which a single-Co-site catalyst (Co@POLs) was embedded ionically were evaluated in heterogeneous diisobutylene (DIB) methoxycarbonylation. In this study, structural characterization of POLs was characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and N2 adsorption–desorption isotherms. In addition, the catalytic activity of Co@POLs in DIB methoxycarbonylation with CO and methanol was investigated. In particular, Co2(CO)8@VPy–DVB(2:1) exhibited increased DIB conversion (89.3%), methyl 3,3,5-trimethylhexanate selectivity (92.2%) at 8.0 MPa and 150 °C for 12 h, Additionally, Co2(CO)8@VPy–DVB(2:1) was utilized as a catalyst to investigate the impact of various parameters on the reaction, the catalyst exhibited high recovery ability and thermostability.

The impact of fuel and injection strategy on combustion characteristics, emissions and efficiency in gasoline compression ignition operation

Gasoline compression ignition in diesel engines has been proposed in order to meet increasingly stringent emission regulations without sacrificing efficiency. In this study, a six-cylinder heavy-duty diesel engine was operated in a mixing controlled gasoline compression ignition mode to investigate the influence of fuels and injection strategies on the combustion characteristics, emissions, and thermal efficiencies. Fuels, including ethanol (E), isobutanol (IB), and diisobutylene (DIB), were blended with a gasoline fuel to form E10, E30, IB30, and DIB30 based on volumetric fraction. These four blends along with gasoline formed the five test fuels. With these fuels, three injections strategies were investigated, including late pilot injection, early pilot injection, and port fuel injection/direct injection. The impact of moderate exhaust gas recirculation on nitrogen oxides and soot emissions was examined to determine the most promising fuel/injection strategy for emissions reduction. In addition, first and second law analyses were performed to provide insights into the efficiency, loss, and exergy destruction of the various gasoline fuel blends at low and medium load conditions. Overall, the emission output, thermal efficiency, and combustion performances of the five fuels were found to be similar and their differences are modest under most test conditions. E30 with the port/direct fuel injection strategy obtained the peak brake thermal efficiency (46.9%) and gross indicated thermal efficiency (52.2%) at 14 bar. At 7 bar, the peak brake thermal efficiency (44.2%) and gross indicated thermal efficiency (52.5%) also belonged to E30 with the late pilot injection strategy. The second law analysis revealed that exergy destruction was mostly influenced by the fuel type and not by the injection strategy for the 14 bar operating conditions. However, the opposite trend was observed for the 7 bar case. In addition, port fuel injection in combination with oxygenated fuel blends was found to be helpful to suppress soot emissions for operation with exhaust gas recirculation.

Evaluating the effects of olefin components in gasoline on GDI engine combustion and emissions

Olefins are part of the most important components in gasoline fuel. In this paper, olefin component diisobutylene (DIB), 1-pentene and 1-hexene are involved into research. Three quinary gasoline model fuels containing each of these three olefins are used to support this research. Results prove these three olefins exhibit comparable effects on engine combustion and regulated emissions. However, their differences in affecting VOC and particulate matter emissions are of great significance. DIB leads to higher ethane emission while 1-hexene results in remarkably lower acetylene emission. 1-pentene generally leads to lower formaldehyde and acetaldehyde emissions. Nevertheless, these three olefins lead to comparable total VOC emissions. Further analyses show that alkane, olefin and aromatics take the most part of VOCs while olefin in emission take the most responsibility of ozone formation potential. Although 1-pentene in gasoline does not lead to the lowest VOC emissions, it results in the lowest OFP value when compared with DIB and 1-hexene. Such a finding signifies that gasoline with more 1-pentene content help to alleviate emission photochemical effect when compared with olefin content DIB or 1-hexene, which hints that gasoline with C5 olefin might be favorable than C6 olefin content when OFP of engine VOC emission is considered.

Numerical Investigation of a Central Fuel Property Hypothesis Under Boosted Spark-Ignition Conditions

AbstractIn the present work, a central fuel property hypothesis (CFPH), which states that fuel properties are sufficient to provide an indication of a fuel’s performance irrespective of its chemical composition, was numerically investigated. In particular, the objective of the study was to determine whether Research Octane Number (RON) and Motor Octane Number (MON), as fuel properties, are sufficient to describe a fuel’s knock-limited performance under boosted spark-ignition (SI) conditions within the framework of CFPH. To this end, four TPRF-bioblendstock surrogates having different compositions but matched RON (=98) and MON (=90), were first generated using a non-linear regression model based on artificial neural network (ANN). Three unconventional bioblendstocks were included in the analysis: di-isobutylene (DIB), isobutanol, and Anisole. Skeletal reaction mechanisms were generated for the TPRF-DIB, TPRF-isobutanol, and TPRF-anisole blends from a detailed kinetic mechanism. Thereafter, numerical simulations were performed for the fuel surrogates using the skeletal mechanisms and a virtual cooperative fuel research (CFR) engine model, under a representative boosted operating condition. In the computational fluid dynamics (CFD) model, the G-equation approach was employed to track the turbulent flame front and the well-stirred reactor model combined with the multi-zone binning strategy was used to capture auto-ignition in the end-gas. In addition, laminar flame speed (LFS) was tabulated for each blend as a function of pressure, temperature, and equivalence ratio a priori, and the lookup tables were used to prescribe laminar flame speed as an input to the G-equation model. Parametric spark timing sweeps were performed for each fuel blend to determine the corresponding knock-limited spark advance (KLSA) and 50% burn point (CA50) at the respective KLSA timing. It was observed that despite same RON, MON, and engine operating conditions, the TPRF-anisole blend exhibited markedly different knock-limited performance from the other three blends. This deviation from the octane index (OI) expectation was shown to be caused by differences in laminar flame speed. However, it was found that relatively large fuel-specific differences in LFS (>20%) would have to be present to cause any appreciable deviation from the OI framework. Otherwise, RON and MON would still be robust enough to predict a fuel’s knock-limited performance.

Elucidating the differences in oxidation of high-performance \u03b1- and \u03b2- diisobutylene biofuels via Synchrotron photoionization mass spectrometry

Biofuels are a promising ecologically viable and renewable alternative to petroleum fuels, with the potential to reduce net greenhouse gas emissions. However, biomass sourced fuels are often produced as blends of hydrocarbons and their oxygenates. Such blending complicates the implementation of these fuels in combustion applications. Variations in a biofuel’s composition will dictate combustion properties such as auto ignition temperature, reaction delay time, and reaction pathways. A handful of novel drop-in replacement biofuels for conventional transportation fuels have recently been down selected from a list of over 10,000 potential candidates as part of the U.S. Department of Energy’s (DOE) Co-Optimization of Fuels and Engines (Co-Optima) initiative. Diisobutylene (DIB) is one such high-performing hydrocarbon which can readily be produced from the dehydration and dimerization of isobutanol, produced from the fermentation of biomass-derived sugars. The two most common isomers realized, from this process, are 2,4,4-trimethyl-1-pentene (α-DIB) and 2,4,4-trimethyl-2-pentene (β-DIB). Due to a difference in olefinic bond location, the α- and β- isomer exhibit dramatically different ignition temperatures at constant pressure and equivalence ratio. This may be attributed to different fragmentation pathways enabled by allylic versus vinylic carbons. For optimal implementation of these biofuel candidates, explicit identification of the intermediates formed during the combustion of each of the isomers is needed. To investigate the combustion pathways of these molecules, tunable vacuum ultraviolet (VUV) light (in the range 8.1–11.0 eV) available at the Lawrence Berkeley National Laboratory’s Advanced Light Source (ALS) has been used in conjunction with a jet stirred reactor (JSR) and time-of-flight mass spectrometry to probe intermediates formed. Relative intensity curves for intermediate mass fragments produced during this process were obtained. Several important unique intermediates were identified at the lowest observable combustion temperature with static pressure of 93,325 Pa and for 1.5 s residence time. As this relatively short residence time is just after ignition, this study is targeted at the fuels’ ignition events. Ignition characteristics for both isomers were found to be strongly dependent on the kinetics of C4 and C7 fragment production and decomposition, with the tert-butyl radical as a key intermediate species. However, the ignition of α-DIB exhibited larger concentrations of C4 compounds over C7, while the reverse was true for β-DIB. These identified species will allow for enhanced engineering modeling of fuel blending and engine design.

The influence of iso-butene kinetics on the reactivity of di-isobutylene and iso-octane

The continuous development of a core C0 – C4 kinetic mechanism generally involves updating it using reliable kinetics and thermodynamics and may also involve the inclusion of missing reaction pathways to improve the integrity, prediction accuracy and applicability of the mechanism over a wider range of combustion relevant conditions. Accurate kinetic descriptions of the core mechanism can have a substantial influence on accurate predictions of higher hydrocarbon combustion models as the consumption of these larger species rely heavily on the core mechanism. This study is motivated by a severe under prediction in the reactivity of the high temperature experimental targets of di-isobutylene (DIB), an important component used in surrogate fuel formulations. It is worth noting that isobutene (iC4H8) laminar burning velocities are also severely under-predicted in the recent publication of Zhou et al. [1], which is regarded as a critical fragment formed in the decomposition of DIB, that dictates its fate. We discuss the latest developments to the isobutene kinetics and illustrate the influence that these updates have on the oxidation of higher order hydrocarbons, such as DIB and iso-octane (iC8H18). Improving the kinetic accuracy of the C0 – C4 core mechanism improved not only the iC4H8 predictions but also the predictions of higher hydrocarbons which hierarchically rely on it, for instance, the peak flame speeds for specific cases of iso-octane, iso-butene and di-isobutylene have improved by 3, 6, 12 cm s–1, respectively. In addition, the new iC4H8 model is in excellent agreement with the new laminar burning velocity measurements taken in this study at 1 atm and 428 K. The contribution of the new iC4H8 kinetics alone for the improvement in the LBV predictions is significant, in particular the Ċ3H5-t + ĊH3 = iĊ4H7 + Ḣ and iC4H8 = iĊ4H7 + Ḣ reactions are very sensitive at high temperatures. In addition, the new isobutene model is in very good agreement with experimental ignition delay times and species profiles measured during pyrolysis and oxidation conditions.

RON and MON chemical kinetic modeling derived correlations with ignition delay time for gasoline and octane boosting additives

For regulatory and certification purposes the indices that characterize the ignition propensity for a fuel, Research Octane Number (RON) and Motor Octane Number (MON), are measured in a Cooperative Fuel Research (CFR) engine. In an effort to reduce the cost and time of CFR engine testing, computer simulation based work capable of predicting the octane numbers for any fuel blend has received increased attention. Notably, the works of Westbrook et al. [1], Badra et al. [2], and Kim et al. [3] simulated the second stage hot ignition delay time (IDT) for fuels and correlated their ignition delay time with experimental RON/MON measurements to determine the relationship between calculated IDT and RON/MON, thereby providing a means to analytically assess the apparent RON/MON and octane sensitivity (OS=RON-MON) values for the fuel. Using a similar methodology, the current study investigated RON-like and MON-like simulated engine compression histories calculated using GT-Power. The current work's calculated IDTs were determined for mixtures of primary reference fuel (PRF) gasoline and major blending components (i.e., iso-octane, n-heptane, ethanol, and toluene), and neat octane boosting additives (e.g., ethyl-benzene, iso-butanol, di-iso-butylene (DIB)) using 0-D closed homogeneous reactor chemical kinetic simulations driven by volume-time and pressure-time compression profiles. The primary goal of the current work was to explore any possible dependence of the fuel's predicted octane number with the compression profile used (i.e., volume-time profile and pressure-time profile). To investigate any possible dependence, the calculated IDTs for both the volume profile and pressure profile driven simulations were used to develop RON and MON correlation curves based on the PRF and neat fuel experimental literature data from McCormick et al. [16]. The model derived RON and MON correlation curves were used to analytically assess the octane numbers of PRFs, toluene PRFs (TPRFs), and both PRFs and TPRFs blended with ethanol for comparison with experimental data from Foong et al. [13]. The simulations indicated a synergistic blending effect on octane number for ethanol blended with PRFs and TPRFs. Overall, the volume profile driven RON/MON/OS assessments had less difference from the experimental PRFs and TPRFs data (i.e., on the order of approximately +/- 2-6 ONs) than the pressure profile driven RON/MON/OS assessments (i.e., greater than approximately +/- 6 ONs). Lastly, the volume and pressure profile driven RON and MON assessments for selected mixtures were compared to the RON and MON assessments completed in [1] which were determined with pressure profile driven simulations.

Chemical Kinetic Model of Multicomponent Gasoline Surrogate Fuel with Nitric Oxide in HCCI Combustion.

This study presents a simplified mechanism of a five-component gasoline surrogate fuel (TDRF–NO) that includes n-heptane, isooctane, toluene, diisobutylene (DIB) and nitric oxide (NO). The mechanism consists of 119 species and 266 reactions and involves TDRF and NO submechanisms. Satisfactory results were obtained in simulating HCCI combustion in engines. The TDRF submechanism is based on the simplified mechanism of toluene reference fuel (TRF) and adds DIB to form quaternary surrogate fuel for gasoline. A simplified NO submechanism containing 33 reactions was added to the simplified mechanism of TDRF, considering the effect of active molecular NO on the combustion of gasoline fuel. The ignition delay data of the shock tube under different pressure and temperature conditions verified the validity of the model. Model verification results showed that the ignition delay time predicted by the simplified mechanism and its submechanics were consistent with the experimental data. The addition of NO caused the ignition delay time of the mechanism simulation to advance with increasing concentration of NO added. The established simplified mechanism effectively predicted the actual combustion and ignition of gasoline.

Construction and Validation of a Five-Component Fuel Simplification Mechanism for Homogeneous Charge Compression Ignition Engine

The detailed chemical kinetics of ethanol was reduced by means of path analysis and sensitivity analysis. The important components and reaction pathways of ethanol combustion were sorted out, and a reduced chemical kinetics model of ethanol containing 37 components and 78 reactions was developed. On the basis of the reduced mechanism of the gasoline surrogate [iso-octane, n-heptane, toluene, and diisobutylene (DIB)], the reduced mechanism of ethanol was then coupled. A reduced chemical kinetic model of a five-component (iso-octane, n-heptane, toluene, DIB, and ethanol) fuel containing 124 components and 244 reactions and suitable for homogeneous charge compression ignition (HCCI) combustion was finally obtained. Simulation results of the five-component reduced mechanism are compared with the ignition delay of four different components of gasoline surrogate under a shock tube. These results well matched the experimental value. At the same time, the simulation results of the model well matched the experimen...

Evaluation of Adding an Olefin to Mixtures of Primary Reference Fuels and Toluene To Model the Oxidation of a Fully Blended Gasoline

The impact of adding an olefin to ternary mixtures of toluene and primary reference fuels to mimic the oxidation of a fully blended gasoline was examined with kinetic modeling. Reactions for the oxidation of 2,4,4-trimethyl-1-pentene (DIB-1), which is the major constituent in diisobutylene (DIB), were added to a previously developed semidetailed mechanism for ternary mixtures. The merged kinetic mechanism was revised and successfully checked for validity against data for neat fuel components as well as fuel mixtures at conditions relevant to engine combustion. The validated kinetic model was then used to model a fully blended research gasoline. By using a nonlinear-by-volume blending model for octane numbers, a four-component surrogate fuel was formulated which consisted of 51% isooctane, 18% n-heptane, 26.4% toluene, and 4.6% DIB-1 by liquid volume. The surrogate fuel reflected molecular-structure class composition, research octane number, motor octane number, density, and H/C ratio of the target gasolin...

A semi-detailed chemical kinetic model of a gasoline surrogate fuel for internal combustion engine applications

A semidetailed chemical kinetic mechanism (473 species and 1267 reactions) to describe the oxidation of a gasoline surrogate fuel consisting of n-heptane, iso-octane, toluene and diisobutylene (DIB) is developed. The model shows generally good agreement with the experimental ignition delay times measured in shock tubes for not only individual components but also their various mixtures over a wide range of temperatures and pressures. Although both simulations and experiments indicate toluene has a promoting effect on the auto-ignition of iso-octane in a specific region, the effect of toluene addition to isooctane is still not fully resolved. Nonetheless, it is found that the reactions of benzyl radical with allene are not important for the kinetic interactions. The measured laminar burning velocities of a research gasoline fuel, CR-87, can be well reproduced by using a TRF+DIB mixture (C6H5CH3/iC8H18/nC7H16/JC8H16, 45/25/20/10% by liquid volume) as a surrogate. In a homogeneous charge compression ignition (HCCI) engine, the model can capture the shift in resistance to auto-ignition for such TRF+DIB fuel when the operating conditions change. A sensitivity analysis shows the chemical origin of such shift cannot be solely explained based on the extent to which NTC (negative temperature coefficient) behavior is absent. The effect of decreasing the inlet temperature and increasing the inlet pressure is a result of the concerted action of manifold factors.

Catalytic etherification of glycerol to produce biofuels over novel spherical silica supported Hyflon® catalysts

Etherification of glycerol (GLY) with isobutylene (IB) to produce biofuels was investigated in liquid phase using spherical silica supported Hyflon® catalysts (SSHC). As reference catalyst, Amberlyst® 15 (A-15) acid ion-exchange resin was used. Experiments were carried out in batch mode at a reaction temperature ranging from 323 to 343K. SSHC were found to be very effective systems in etherification of glycerol with IB, providing cumulative di- and tri-ethers yields higher than that obtained by using A-15 catalyst. Furthermore, such catalysts were stable and easily reusable; no leaching of active phase was observed. The formation of poly-substituted ethers, suitable additives for conventional fuels, was favored by operating at an isobutylene/glycerol molar ratio >3 and low reaction time (<6h); however, the concentration of mono-ether reached values lower than 3wt.% only when SSHC catalyst was used. Turnover frequency of glycerol (TOFGLY) highlighted that SSHC systems were much more active than A-15 catalyst: the accessibility and nature of active sites and the surface properties of catalysts were indicated as the main factors affecting the catalytic behavior. A lower acid site density of SSHC than that of A-15 catalyst was decisive in preventing the occurrence of oligomerization reaction which leads to the formation of di-isobutylene (DIB), precursors of gummy products.

Synthesis of polysulfides using diisobutylene, sulfur, and hydrogen sulfide over solid base catalysts

A series of solid base catalysts were prepared with several alkali and alkaline earth metal species. The catalysts were used in one-stage synthesis processes of polysulfides using diisobutylene (DIB), sulfur, and hydrogen sulfide (H 2S). The possibility of using solid base catalyst as an alternative for a liquid amine catalyst and the effects of preparation conditions on the catalytic activity were discussed. Alumina-supported potassium catalysts showed a catalytic activity comparable to that of dicyclohexylamine. The alkali metal catalysts proved to be more effective than alkaline earth metal catalysts. Further, a three-stage mechanism for polysulfide synthesis using the system of diisobutylene, sulfur, and hydrogen sulfide in the presence of solid base catalysts was suggested. Moreover, a novel [ 14 C ]CO 2 radioisotope pulse tracer method was developed to determine the amount of CO 2 adsorption on solid base catalysts at the temperatures between 100–400 °C and under 0.6–3.1 MPa. The relationship between the uptake amount of CO 2 on the alkali metal catalysts and the catalytic activity in syntheses of polysulfides was discussed.

ChemInform Abstract: Alkylation of Substituted Phenols with Olefins and Separation of Close Boiling Phenolic Substances via Alkylation/Dealkylation.

The alkylation of substituted phenols, such as, m- and p-cresols and 2,4-, 2,5-, and 2,6-xylenols, with olefins such as α-methylstyrene (AMS) and diisobutylene (DIB) in the presence of homogeneous catalyst p-toluenesulfonic acid (pTSA) and heterogeneous catalyst Amberlyst 15 was studied in the temperature range 60-160°C. The relative rates of alkylation of various substituted phenols with AMS and DIB under different operating conditions and the ortho/para product distribution were determined. A separation strategy based on alkylation, separation of the alkylated products by dissociation extraction and their subsequent decomposition, is presented for the separation of industrially important close boiling isomeric/nonisomeric substituted phenols, such as, m- and p-cresols, 2,5- and 2,4-xylenols, and p-cresol/2,6-xylenol. A new method of refining technical grade 2,6-xylenol containing p-cresol impurity through the acid-catalyzed O-alkylation of p-cresol with isobutylene is presented

Alkylation of substituted phenols with olefins and separation of close-boiling phenolic substances via alkylation/dealkylation

The alkylation of substituted phenols, such as, m- and p-cresols and 2,4-, 2,5-, and 2,6-xylenols, with olefins such as α-methylstyrene (AMS) and diisobutylene (DIB) in the presence of homogeneous catalyst p-toluenesulfonic acid (pTSA) and heterogeneous catalyst Amberlyst 15 was studied in the temperature range 60-160°C. The relative rates of alkylation of various substituted phenols with AMS and DIB under different operating conditions and the ortho/para product distribution were determined. A separation strategy based on alkylation, separation of the alkylated products by dissociation extraction and their subsequent decomposition, is presented for the separation of industrially important close boiling isomeric/nonisomeric substituted phenols, such as, m- and p-cresols, 2,5- and 2,4-xylenols, and p-cresol/2,6-xylenol. A new method of refining technical grade 2,6-xylenol containing p-cresol impurity through the acid-catalyzed O-alkylation of p-cresol with isobutylene is presented

Selective dimerization of diisobutylene by oxo acids: Synthesis of isobutylene tetramer

Isobutylene tetramers (IB4) were obtained in high yield by the cationic dimerization of commercial diisobutylene (DIB) (2,4,4-trimethyl-1-pentene with isomeric impurities) with CF3SO3O3H or CH3COClO4 as catalyst. The best IB4 yields (80–90%) were achieved at 0–30°C in nonpolar solvents (n-hexane and CCl4). The major components in the IB4 produced under these conditions were 2,2,6,6,8,8-hexamethyl-4-methylenenonane (8) and 2,2,4,6,6,8,8-heptamethyl-4-nonene (9) that arose via simple linear dimerization of DIB. The yield of IB4 was almost independent of the monomer concentration ranging from 10 to 50 vol % at 0°C, but decreased at higher temperatures (>50°C) or in a polar solvent [(CH2Cl)2] because of the formation of higher oligomers and side reactions such as cracking. A Lewis acid catalyst (AlEtCl2) resulted in a very complex mixture of C12–C20 hydrocarbons at 0°C in CCl4; the yield of IB4 was less than 40%. The catalytic difference between oxo acids and metal halides is discussed.

Destructive Alkylation of Phenol with Diisobutylene

4-t-Butyl phenol (4-TBP) was synthesized from diisobutylene (DIB) and phenol (PhOH) using aluminum chloride as catalyst, and this reaction steps were discussed.The conditions of the reaction were as follows: temperature 120°C, DIB/PhOH mole ratio 0.4, reaction time 1hr, and aluminum chloride 5wt% (based on feed PhOH). The yield of 4-TBP was 96.3% (based on feed DIB) and 62% (based on feed PhOH) and other alkyl phenol content was 1.8%.The reaction was consecutive, in which t-octyl-phenol (TOP) was first formed from DIB and PhOH, and then t-butyl phenol (TBP) was produced through the reaction of TOP and PhOH, where the reaction of TOP and PhOH was a rate determining step. The result of the alkylation of PhOH with DIB could be expressed by the 1st order rate equation in terms of DIB concentration, and the activation energy was calculated to be 20.2kcal/mole. In the reaction of TOP and PhOH, the rate was proportional to the 1st order with respect to the concentration of TOP.