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Organic Air Pollutants
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Single-ring aromatic compounds are important constituents of gasoline, although the benzene content in gasoline is restricted because of its possible health effects. Aromatic hydrocarbons are raw materials for the manufacture of monomers and plasticizers in polymers. Styrene is a monomer used in the manufacture of plastics and synthetic rubber. Cumene is oxidized to produce phenol and acetone, which are valuable by-products. Because of these applications, plus production of these compounds as combustion by-products, aromatic compounds are common atmospheric pollutants. A group of single-ring aromatic hydrocarbons that are found as urban air pollutants are those in the group known as BTEX consisting of benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene.7
Feedstock Chemistry in the Refinery
Published in James G. Speight, Refinery Feedstocks, 2020
Polycyclic naphthenes can also be converted to the corresponding aromatics by heating at 450°C (840°F) in the presence of a chromia–alumina (Cr2O3-Al2O3) catalyst. Alkyl aromatic derivatives also dehydrogenate to various products. For example, styrene is prepared by the catalytic dehydrogenation of ethylbenzene. Other alkylbenzenes can be dehydrogenated similarly; iso-propyl benzene yields α-methyl styrene.
Biomarkers in Occupational Neurotoxicology
Published in Lucio G. Costa, Luigi Manzo, Occupatinal Neurotoxicology, 2020
Styrene is a very important solvent used in the manufacture of numerous polymers and copolymers, including polystyrene, styrene — acrylonitrile or styrene — butadiene rubber.50 Like other organic solvents, acute exposure to high levels of styrene causes irritation (of both skin and respiratory tract) and central nervous system depression, while upon chronic exposure, styrene may have carcinogenic and reproductive toxicity.51,52 Styrene exposure has also been reported to cause neurotoxic effects. Indeed, a large number of studies in occupationally exposed workers have reported signs and symptoms of central nervous system toxicity,53-58 though some of these findings have been recently criticized.59
Is micronucleus assay in nasal mucosa cells an appropriate technique for detecting genotoxins by inhalation in humans? A systematic review
Published in International Journal of Environmental Health Research, 2023
Giovana Wagner Branda Drummond, Andrea Cristina de Moraes Malinverni, Ana Claudia Muniz Renno, Daniel Araki Ribeiro
Styrene is a precursor of polystyrene, used in plastic products industries (Choi et al. 2017). Exposure to this chemical compound can be either seasonal or occupational by inhalation, eye contact, or skin absorption. However, occupational exposure is more problematic due to the high levels and frequency of exposure. The International Agency for Research on Cancer (IARC) classifies styrene as a Group 2B carcinogen (Pleban et al. 2017). Godderis et al. (2004) assessed exposure to styrene and found an elevation of micronuclei in nasal cells in the exposed group. Chromium is a metal present in nature in different forms, but chromium (IV) is toxic and considered to be carcinogenic. For workers who are exposed to this element daily, the risk of developing cancer is high (Skowroń and Konieczko 2015). Burgaz et al. (2002) and Huvinen et al. (2002) analyzed the exposure to chromium: the former observed an elevation of micronuclei in the exposed group, while the latter found no statistical difference compared with the control group. Finally, Sarto et al. (1990), who assessed exposure to chromium trioxide and ethylene oxide, found an elevation of micronuclei only in the group that was accidentally exposed to EtO leakage.
Insight into single- and bi-objective optimization of industrial problems
Published in Materials and Manufacturing Processes, 2023
Styrene is produced via a reversible endothermic reaction of ethylbenzene. Due to the involvement of multiple side reactions, and multiple side products, it is important to maintain high production rate of pure styrene product. Therefore, two objectives, namely, styrene flow rate (FST) and styrene selectivity (SST) are maximized. The detailed mathematical model along with decision variables, constraints, and their ranges are taken from the literature.[30,31] The HMODE-DLS[7,33] algorithm is used in this study for multi-objective optimization, and the improved BHO algorithm is used to solve the single-objective optimization problems. In the HMODE-DLS algorithm, the MODE algorithm is hybridized with a distance learning local search algorithm. The improved BHO algorithm improves the flexibility of BHO by moving the stars in the search space. The detailed working procedure is available in the literature for both algorithms.[7,32,33] The penalty method is applied to handle the constraints.[34] The ZDT1 test problem is solved as the MOO test problem[34] to evaluate the HMODE-DLS algorithm’s performance. The problem’s name, types, case studies, objectives, decision variables and constraints are given in Table 1.
Catalytic performance of modified beta zeolite on the synthesis of styrene and xylene: a kinetic study
Published in Indian Chemical Engineer, 2020
Yashika Raparia, Gopinath Halder, RajKumar Arya, Sanghamitra Barman
At present, styrene production technologies have focused on equipment improvements, process optimisation and catalyst development. High price of feedstocks has become a major problem for conventional styrene manufacturers. On the other hand, benzene prices have a considerable hike for last few years and have reached to its highest peak making life difficult for styrene producers through the ethylbenzene route. Researchers have been attempting to develop styrene production by toluene route for the past 30 years, but it has been difficult to devise a catalyst with the yield and selectivity to make a commercially viable process. In addition, a cooperation of acid and base is required for side-chain alkylation of toluene with methanol [24,25]. Exchanging K with H+ of zeolite can provide a fine-tuning of acidity and basicity, which will deliver us more information about the exact requirements of acid–base sites density and strength for the side-chain alkylation. In the present work, a set of K-exchanged zeolites (Kβ) were prepared to have an insight into the effect of exchange on the direction to ring or side-chain alkylation and the exact requirements about acidity and basicity for the side-chain alkylation.