Benzene Purity Research Articles

Benzene Purity Improvement and Feed Amount Reduction on Benzene Production

Global demand for benzene is expected to rise significantly. Previous research focused on extracting toluene from water, but a proposed shift towards preventive measures includes recycling toluene to avoid pollution and enhance benzene production. Emphasis on addressing separation ratios and material balance is crucial for successful simulations. Proposed innovations involve added splitters and shortcut columns for enhanced purity. Benzene production could be gained through the process of hydrodealkylation with some modifications. It shows the significant difference of the purity of benzene produced with the use of splitter and shortcut column compared to not using splitter and shortcut column. The recycling process effects the mass flow of the compound which picture the capability of a process to scale up. Through recycling the toluene, it also happens to cut or push the sum of the feed which leads the process to be more economical. Based on the modification of the benzene production it is resulted that the mass flow rate of the benzene production is significantly increased from 38.6 kg/h to 430.72 kg/h which gives possibility of the production to be higher in one go. Recycling toluene and hydrogen will also help the effectivity and efficiency of the process by its quality and specifically its quantity of the fresh feed. The modification also affects the purities of the benzene from 70.72% to 99.95%. Therefore, by doing the modification it will produce greater number of benzene with its high purities. Copyright © 2024 by Authors, Published by Universitas Diponegoro and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Flexible Luminescent Hydrogen-bonded Organic Framework for the Separation of Benzene and Cyclohexane.

A nonplanar phenothiazine derivative with three cyano moieties (PTTCN) is designed and synthesized to achieve functional crystals for absorptive separation of benzene and cyclohexane. PTTCN can crystallize into two kinds of crystals with different fluorescence colors in different solvent systems. The molecules in two crystals are in different stereo isomeric forms of nitrogen, quasi axial (ax), and quasi equatorial (eq). The crystals with blue fluorescence in ax form may selectively adsorb benzene by a single-crystal-to-single-crystal (SCSC) transformation, but separated benzene from a benzene/cyclohexane equimolar mixture with a low purity of 79.6%. Interestingly, PTTCN molecules with eq form and benzene co-assembled to construct a hydrogen-bonded framework (X-HOF-4) with S-type solvent channels and yellow-green fluorescence, and can release benzene to form nonporous guest-free crystal under heating. Such nonporous crystals strongly favor aromatic benzene over cyclohexane and may selectively reabsorb benzene from benzene/cyclohexane equimolar mixture to recover original framework, and the purity of benzene can reach ≈96.5% after release from framework. Moreover, reversible transformation between the nonporous crystals and the guest-containing crystals allows the material to be reused.

Hydrogen-bonding-driven self-assembly nonporous adaptive crystals for the separation of benzene from BTX and cyclohexane

Benzene is a volatile organic compound that can seriously harm human health, while it can serve as a precursor to produce chemicals of more complex structures in chemical industry. Capturing benzene using adsorbents is of great importance for human health, when the separation of hydrocarbons including benzene from crude oil was referred to as one of the “seven chemical separations to change the world”. In this work, we reported the efficient and selective separation of benzene from BTX and cyclohexane by hydrogen bonding self-assembly nonporous adaptive crystals AdaOH for the first time under mild and user-friendly conditions. Separation of benzene and cyclohexane (v/v = 1:1) can be achieved by AdaOH with a purity of benzene up to 96.8%. Separation of BTX (v/v; benzene:toluene:o-xylene:m-xylene:p-xylene= 1:1:1:1:1) can be achieved by AdaOH with a purity of benzene increased from 20% to 82.9%. Our results suggest that separation of benzene using the activated AdaOH as a non-porous adaptive crystal for selectively and efficiently capturing benzene can solve the challenge in separation of benzene from other chemicals such as cyclohexane in chemical industry, and can be helpful for removal of benzene that is released from the vehicles to air. The advantages of commercially availability, easy preparation, high separation efficiency and selectivity for benzene might endow this material with enormous potential for practical uses in areas like petrochemical industry.

Separation of toluene from benzene derivatives and extraction of toluene from water based on a flexible naphthalene diimide coordination network

The separation of toluene derivatives from each other is an important, challenging, and energy exhaustive process in chemical industry. Here we report a new flexible coordination network, [Cu(4-pmntd)2(NO3)2](4-pmntd = N, N’-Bis(4-pyridymethy)naphthalene diimide), that exhibits not only selective separation of toluene over benzene and xylene, but also can straight extract toluene from water. The high performance for selective adsorption of toluene was validated by single-crystal XRD, vapor sorption isotherms, and NMR. The detailed structural information discloses that the naphthalene diimide derivative ligand can form intermolecular charge-transfer interactions with toluene, and thus highly selective capture toluene with its derivatives. Naphthalene diimide ligand engenders favorable aromatic π interactions for its electron-deficient and planar aromatic surface. The electron giving substituents on aromatic ring cause an overall change in the cloud density, which can be employed in separating toluene derivatives. When 1:1 toluene/benzene mixture pass through a fixed-bed packed column with this coordination network, 96% purity of benzene can be directly produced during the first adsorption cycle. The outlet xylene purity was raised from 50% to 85% when 1:1 toluene/xylene mixture pass through the porous materials. The separation performance of the coordination network could be used for industrial separation of toluene derivatives with a low energy cost at room temperature.

Control and Optimization of Aromatic Compounds in Multivariable Distillation Column

Product separations in petroleum refineries depend significantly on distillation process, which is known to be challenging to be optimally managed, especially when multiple products with variety of purity requirements are involved due to nonlinear dynamics and high degree of process interactions. In this paper, control and optimization aspects of a multivariable distillation process are discussed. A mathematical model of the system is simulated in MATLAB programming environment, and analyses of process behavior and control performances are carried out. The controllers are tuned using conventional Ziegler-Nichols method and L-V control configuration was adopted. The results on disturbance rejection and set point tracking capabilities, in order to maintain the purity of benzene in the distillate above 98.5 % are discussed. Based on these insights, the optimum operating conditions were determined, which serves as a good starting point for further works in addressing variety of problems related to process operations.

Improvement of the Benzene Yield During Pyrolysis of Terephthalic Acid Using a CaO Fixed-Bed Reactor

Effects of pyrolysis temperature and terephthalic acid (TPA) gas concentration on TPA degradation as a model substance for poly(ethylene terephthalate) (PET) degradation products were investigated with emphasis on benzene yield and decrease of carbonaceous residue. TPA was decarboxylated using a spiral tube reactor filled with CaO. The best results were achieved at 600 °C and TPA gas load of 28 mg L–1, yielding 84% benzene. Of the initial carbon, 29% remained in the reactor, consisting of carbonate and carbonaceous residue. Benzene purity was more than 97 wt % under all reaction conditions. Low TPA gas loads and high gas velocities resulted in good benzene yields and purities because TPA gas deeply penetrated the CaO fixed bed before adsorption. This resulted in lower TPA concentration at the CaO surface, reducing the interference between neighboring TPA molecules and limiting carbonaceous residue formation.

Precoking selectivation for improving benzene product purity in heavy aromatics transalkylation

A precoking selectivation technique is developed to improve the benzene purity in the heavy aromatics transalkylation over Pt/ZSM-12. The effect of precoking is selective to coking condition. Precoking in hydrogen can significantly improve benzene product purity. In contrast, precoking in helium results in severe deactivation of catalytic activity and deteriorates benzene product purity. For Pt/ZSM-12 at a platinum content of 200 pm as an example, subject to precoking treatment in hydrogen at a coke content of ca. 15.8 wt%, the benzene product purity can be improved up to the industrial specification of 99.85%.

Metal zeolites for transalkylation of toluene and heavy aromatics

The fabrication and modification of metal zeolite catalysts for the conversion of heavy aromatics were investigated. The catalytic performances for various metal-free 12-MR zeolites were evaluated in terms of conversion, product yields, benzene purity and reaction network analyses using transalkylation of toluene and 1,3,5-trimethylbenzene as the test reaction. The effects of metal content, feed impurity, and steaming treatment on the catalytic performances of Pt/mordenite zeolites prepared by different metal incorporation methods were also examined. A sulfuration technique for fine tuning the catalytic activity of the metal catalyst while sustaining desirable stability and performance was developed and its application for transalkylation of heavy aromatics was illustrated by Pt/ZSM-12 catalyst.

Comparison of Vanadium Oxide Catalysts for Synthesis of Benzene: Benzene Purity, Yields and Reconditioning Methods

This study compares vanadium oxide catalysts from three different sources: Noakes (N), Harshaw Chemical (H) and Kh. Arslanov at the St. Petersburg State University, Russia (R). The catalysts are used to convert acetylene to benzene in the last step of benzene synthesis. The organic purity of benzene in all three catalysts is high; 99.91–99.93% for (N) and (H) and 99.87% for (R). The benzene yields range from 90.0 to 94.3%. (N) averaged 92.6%, (H) averaged 91.1% and (R) averaged 92.0%. A conversion residue in the catalysts was analyzed for δ13C and found to be isotopically lighter relative to acetylene by −2.2% for (N) and (H) and −3.9% for (R). Benzene yields were studied on different reconditioning methods applied to all catalysts: heating to 400° in air averaged 92.3%; the same temperature with a half and half mixture of O2 and Ar averaged 91.9%, adding a half and half mixture of H2 and Ar at 200° to the end of this treatment averaged 91.8%. Based on this research, the obvious difference seen between the catalysts is in their trace by-products.

Influence of Chromium Endowment and Surface Area of Silica-Alumina Catalysts and of Reaction Conditions on Benzene Synthesis

Radiocarbon laboratories using liquid scintillation counting depend on the availability of a catalyst for benzene synthesis. One of the two commonly used is a commercially available chromium-activated silica-alumina catalyst, PKN/D1. As this catalyst will no longer be produced, we have tested similar catalysts as possible replacements. We measured benzene purity by gas chromatography and mass spectrometry, and found that chromium endowment was crucial for a proper catalyst function. The surface area of the catalyst also significantly affected benzene yield and purity. We also studied the effects of different reaction conditions of acetylene absorption and benzene desorption on benzene purity. A catalyst with half of the Cr endowment and doubled specific surface area created yield and purity comparable to PKN/D1.

Liquid Scintillation Counter Characterization, Optimization and Benzene Purity Correction

In liquid scintillation counting (LSC), small variations in benzene purity can cause 14C pulse-height spectra to move with respect to the counting window. Thus, one must carefully monitor the purity of each benzene sample and apply corrections for spectral shifts. I describe here the techniques used at Queen's University Belfast for deriving correction factors for observed small variations in benzene purity. I also describe the methods used at our laboratory to fine-tune our Quantulus LS counters for high-precision dating. The tuning of the instruments minimizes the effect of fluctuations in gain that may occur during the long counting periods required for high-precision dating. Any remaining influences on efficiency owing to gain changes are corrected for, along with the purity correction, by continuous monitoring of the spectrum produced by the external source.

New selective solvents of aromatic hydrocarbons based on petroleum sulphoxides

Effective extraction agents were proposed for the recovery of benzene and toluene from hydrocarbon mixtures during extractive rectification. Petroleum sulphoxides and their synergistic mixtures with diethylene glycol and dimethylformamide, enabled benzene and toluene to be recovered to the extent of 91–99% with a purity of 92–98%; when recovery is from a mixture enriched with benzene purity increases to 99·5%.

Recent improvements in benzene chemistry for radiocarbon dating

Benzene radiocarbon dating is discussed in view of recent improved chemistry. A high yield benzene catalyst is described which eliminates concern for carbon isotope fractionation, benzene purity and extensive sample preparation time.

Comparison of cryoscopic determinations of purity of benzene by thermometric and calorimetric procedures

Workers at the National Bureau of Standards and elsewhere have been conscious of the discordant results sometimes yielded by two methods for determining purity employing the same physical principle. A comparison was made on samples of benzene by the thermometeric method, by which a stirred sample is frozen at nearly constant rate, and by the calorimetric method, by which a frozen sample is melted in stages by the addition of accurately controlled increments of energy under adiabatic conditions. Benzene, purified by single crystal formation and of very high purity, was contaminated in known amounts by n-heptane and samples of the same level of purity determined by both procedures. Great care was taken to submit samples of the same composition to the different groups employing the two different methods. Further, the actual degree of contamination of the benzene was unknown to both groups until final values of the purity were submitted. Results of this comparison showed that the large divergence between the two methods that had characterized earlier comparisons is not displayed. The differences between the analyses on all three samples are roughly of the order of the statistically estimated uncertainties of the averages and less than deviations between individual experiments by one method. Comparison of the methods with absolute values of purity could not be made because of contamination of the highly purified sample of benzene with supposedly chemically adsorbed water from the borosilicate glass walls.

(92)ベンゾールの高圧空気酸化に関する研究(第1報)フェノール生成に対する作業因子及び原料純度の影響

(92)ベンゾールの高圧空気酸化に関する研究(第1報)フェノール生成に対する作業因子及び原料純度の影響