China
Africa
Explore chapters and articles related to this topic
Catalytic Applications of Zeolites in Industrial Processes
Published in Subhash Bhatia, Zeolite Catalysis: Principles and Applications, 2020
In a manner similar to styrene production, toluene may be alkylated with ethylene to produce ethyltoluene (ET). An unmodified catalyst gives a near equilibrium mixture of isomers, similar to solution reactions with AlCl3. HCl catalysts. Physical treatment of the ZSM-5 catalyst with stream or coking or modification with metal salts produces catalysts which give a whole spectrum of isomeric mixtures containing up to 99% p-ethyltoluene in the product as shown in Table 20.
Evaluating potential human health risks from modeled inhalation exposures to volatile organic compounds emitted from oil and gas operations
Published in Journal of the Air & Waste Management Association, 2019
Chris Holder, John Hader, Raga Avanasi, Tao Hong, Ed Carr, Bill Mendez, Jessica Wignall, Graham Glen, Belle Guelden, Yihua Wei
At 500 ft from each individual development pad, the highest estimated 1-hour exposures exceeded criteria values for four VOCs (benzene, 2- and 3-ethyltoluene, and toluene) at the selected receptors, which were locations more often downwind from the emissions (Table 2). Particularly: maximum acute HQs were > 10 at 500 ft for 2-ethyltoluene (during flowback at the GC sites) and benzene (during drilling and flowback at the NFR site), and also at 2,000 ft for benzene during flowback at NFR. Table 2 also identifies the critical-effect groups with maximum HIs > 1 (hematological, respiratory, and neurotoxicity) and > 10 (hematological) for one or more O&G activities. We provide in Supplementary Section H the HQs and HIs for individual chemicals and critical-effect groups associated with different pad sizes, at all modeled distances and sites. Generally, large pad sizes were associated with somewhat lower HQs and HIs (sometimes ≥ 2 fold) vs. small pads because the plume from a larger source is less concentrated than one from a smaller source (when emission mass is constant).
Indoor air quality and wildfire smoke impacts in the Pacific Northwest
Published in Science and Technology for the Built Environment, 2018
W. Max Kirk, Madeline Fuchs, Yibo Huangfu, Nathan Lima, Patrick O'Keeffe, Beiyu Lin, Tom Jobson, Shelley Pressley, Von Walden, Diane Cook, Brian K. Lamb
Prior to these measurements, H2 and H3 were equipped with occupancy sensors on the exterior doors and windows to indicate when each was opened or closed, as well as indoor motion and temperature sensors for assessing occupant activities. Blower door tests at 5–50 Pa were performed on H2 and H3 to determine air exchange per hour (ACH50) using standard industry practices. The so-called air exchange per hour natural (ACH50, natural), estimated via logarithmic extrapolation at 0 Pa pressure difference, can be used to characterize house tightness (see Table 1). Both outdoor and indoor trace gases and PM were monitored at each site, along with outdoor meteorological conditions. Additionally, carbon dioxide (CO2) tracer tests were conducted throughout each measurement period to determine air exchange rates. Table 2 summarizes the variables monitored and the instrumentation used for each house. Volatile organic compounds (VOCs) were measured with a Proton Transfer Reaction Mass Spectrometer (PTR-MS, Ionicon Analytik GmbH) that allows for high time resolution monitoring (∼1 min) of a range of compounds including known air toxics (Jobson and McCoskey 2010). Compounds monitored included acetonitrile (a wood smoke tracer), formaldehyde, acetaldehyde, methanol, acetone, benzene, toluene, and C2-alkylbenzenes (i.e., sum of xylenes and ethylbenzene), C3-alkylbenzenes (i.e., sum of trimethylbenzene, ethyltoluene, and propylbenzene isomers), and C4-alkylbenzenes (i.e., sum of tetramethylbenzene and its isomers).
Targeted GC-MS analysis of firefighters’ exhaled breath: Exploring biomarker response at the individual level
Published in Journal of Occupational and Environmental Hygiene, 2019
M. Ariel Geer Wallace, Joachim D. Pleil, Karen D. Oliver, Donald A. Whitaker, Sibel Mentese, Kenneth W. Fent, Gavin P. Horn
Targeted analysis was performed using a previously developed selected ion monitoring (SIM)/scan method to quantify VOCs in breath samples. Procedures for preparation of VOC standards, instrument calibration and analysis can be found in Wallace et al. 2017.[24] Briefly, benzene, toluene, ethylbenzene, m,p-xylene, styrene, o-xylene, 4-ethyltoluene, and 1,3,5-trimethylbenzene were all targeted in the method using selected target and qualifier ions. A gaseous TO-14A 43 Component Mixture at 1 part-per-million (ppm) in nitrogen was purchased from Linde Electronics & Specialty Gases (Stewartsville, NJ). Calibration levels of 0, 0.5, 1.0, 2.0, 5.0, 10.0, 25.0, and 50.0 parts per billion by volume (ppbv) were achieved by varying the flow rates of the TO-14A calibrant gas and a dilution gas, humidified air, to deliver a constant volume of 200 mL of gas onto each sorbent tube in triplicate using an Easy VOC syringe at 50% relative humidity and 20 °C. PAHs were also calibrated for using a stock 16 component 2000 ng/µL Restek Corporation (catalog no. 31011, Bellefonte, PA) calibration mixture at levels of 0, 0.02, 0.05, 0.10, 0.20, 0.50, 1.0, and 2.0 ng/µL in methanol and were loaded onto sorbent tubes in 1 µL volumes. PAHs are not reported herein due to issues with desorption from Carbograph 2TD/1TD sorbent tubes. The VOCs and PAHs were loaded onto the same sorbent tubes for calibration using a dual loading procedure that is described in detail elsewhere.[24] The VOC and PAH standards were paired from low concentration to high during loading (e.g., 0.5 ppbv VOC with 0.02 ng/uL PAH). The samples were analyzed with a series of three calibrations. Instrument drift was monitored by analyzing calibration check standards after every 13 samples, and the instrument was recalibrated when the area counts of the VOCs fell out of a range of +/- 30% of the calibration value. A detailed description of calibration preparation, standard loading parameters, and method variability can be found in Geer Wallace et al. 2017.[24]