China 
Africa 
Explore chapters and articles related to this topic
Organic Chemicals
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
William J. Rea, Kalpana D. Patel
Trimethylbenzenes are used as chemical intermediates for paint thinners, perfumes, dyes, and fuel additives. Seven-and-a-half percent of the chemically sensitive studied at the EHC-Dallas had trimethylbenzene in their blood, suggesting that, for some reason, these carcinogens and others may bioaccumulate in susceptible patients and thereby play a role in the induction and/or propagation of chemical hypersensitivity. Low levels can cause headache, fatigue, drowsiness, irritation of the skin, and chemical pneumatics.
Effect of pseudo-boehmite on the aromatization performance of Zn-P-Al/ZSM-5 catalysts
Published in Petroleum Science and Technology, 2022
Jing Zhu, Yuying Yang, Wentao Wu, Shuyao Li
A comparison of aromatics distribution in liquid products during aromatization on three catalysts is shown in Table 1. As can be seen from Table 1, the contents of B (benzene), T (toluene) and X (xylene) in products increased while the contents of EB (ethylbenzene), MEB (methylethyl benzene), TMB (trimethylbenzene) and C9+ aromatic decreased when modified ZSM-5 catalyst was used. For aromatization of hydrocarbons, dehydrogenation is carried out in L acid center, while cracking, cyclization and hydrogen transfer are carried out in B acid center (Yang et al. 2016), The aromatization reaction is completed by synergistic action of B acid and L acid, so it is necessary to adjust the ratio of B acid and L acid. The addition of Zn, P and pseudo-boehmite can adjust the ratio of L acid to B acid and change the total acid content. Therefore, the selectivity of the modified catalyst to the first three products was increased, while that to the last four products was decreased. Especially the Zn-P-Al/ZSM-5 catalyst has the highest selectivity to B, T and X, and the total content of BTX is up to 82.73%.
The organic coating unit, an all-in-one system for reproducible generation of secondary organic matter aerosol
Published in Aerosol Science and Technology, 2022
Alejandro Keller, Daniel M. Kalbermatter, Kate Wolfer, Patrik Specht, Peter Steigmeier, Julian Resch, Markus Kalberer, Tobias Hammer, Konstantina Vasilatou
The PID sensors report the concentration of precursor substance in mV. For calibration, a 100-ppm isobutylene–air mixture was measured at regular intervals. The manufacturer provides a list of 916 substances, many of them atmospherically relevant (e.g., benzene, cyclohexene, isoprene, toluene, and 1,3,5-trimethylbenzene among many other), and their response factor compared to isobutylene. Using the response factor provided by the manufacturer (e.g., 0.34 for α-pinene) and the measurement of the isobutylene calibration mixture, which per definition has a response factor of 1, the PID signal can be converted from mV to mixing ratios (ppm). The corresponding mass concentrations can be calculated using the ideal gas law (see section S4 for more details). For best results, calibration should be performed directly using the relevant substance as standards and considering specific components of the carrier gas mixture which absorb UV light and may thus interfere with the PID signal during the experiment.
Catalytic performance of IM-5 zeolite with high xylene selectivity in benzene alkylation with methanol. An alternative to ZSM-5 zeolite
Published in Petroleum Science and Technology, 2020
Xuan Meng, Dezhi Yi, Li Shi, Naiwang Liu
The products distribution of benzene alkylation with methanol on different catalysts are obtained as shown in Supplementary material Table S2. The main products of benzene alkylation with methanol included toluene, ethylbenzene, xylene, methyl-ethylbenzene, trimethylbenzene, tetramethylbenzene, etc. As important chemical raw materials, toluene and xylene were selected as the objective products. Compared with H-ZSM-5, H-IM-5, and H-IM-5(DS) exhibited higher benzene conversion. Meanwhile, H-IM-5 and H-IM-5(DS) had significantly higher xylene selectivity than ZSM-5. Moreover, the content of ethylbenzene on H-IM-5 zeolite decreased to 1.01% and the H-IM-5(DS) exhibited even lower ethylbenzene selectivity, indicating that the H-IM-5 zeolite could suppress the side reaction of methanol more effectively. With the side reaction of methanol suppressed, more proportion of methanol was indeed converted into alkylaromatics on the H-IM-5 and H-IM-5(DS).