Izomerizacijom n-heksana dobivaju se izomeri s visokim vrijednostima oktanskog broja koji se, kao ekološki prihvatljive komponente, koriste za namješavnje motornih benzinskih goriva. Jedan od ...modernih katalizatora koji se koristi u rafinerijskim procesima izomerizacije je Pt/SO42-/ZrO2 katalizator čija katalitička aktivnost ovisi o sastavu sirovine i procesnim uvjetima u sustavu. Povećana potražnja za derivatima nafte u posljednjih nekoliko godina dovodi do potrebe za obradom sirovine manje kvalitete, sa sadržajem spojeva koji negativno utječu na kinetiku i termodinamiku procesa. U ovom radu je proučavan utjecaj sadržaja benzena na proces izomerizacije n-heksana. Kao sirovina za proces pripravljane su otopine benzena u n-heksanu u masenom udjelu od 1, 2, 3 i 4 %. Temperaturni raspon u kojem su vođena ispitivanja je 130-170 °C. Kao dodatni parametri čijom se promjenom pratila učinkovitost procesa bili su omjer vodika kao plina nosioca i sirovine, te prostorna brzina protoka sirovine, odnosno volumni protok sirovine po volumenu katalizatora (eng. LHSV). Dobiveni rezultati ukazuju na smanjenje konverzije n-heksana s povećanjem udjela benzena u sirovini, poglavito pri nižim temperaturama i višim vrijednostima prostornih brzina i omjera vodika i sirovine.
1, 3-Bis (methacryloyloxyethyloxy) benzene (RDMA) was prepared to improve the mechanical properties of dental composite resins. We could polymerize more readily at room temperature with chemical and ...photo initiations than widely used Bis-GMA or TEGDMA. Amounts of monomer eluted from resin made with RDMA was lower than those made with Bis-GMA. It is excellent in hydrophobicity. Combination of mixtures of RDMA and TEGDMA with TMPT filler, which is an reactive organic composite filler, improved the mechanical properties of composite resin such as hardness, compressive strength and amount of uptaken water.
Hlapljivi aromatski spojevi benzen, toluen, etilbenzen i izomeri ksilena (BTEX) rasprostranjeni su u biosferi. Glavni su sastojci benzina i u atmosferu uglavnom dolaze iz ispušnih plinova automobila. ...Dodatni važni izvor izloženosti BTEX-u je pušenje. Opća populacija je više ili manje trajno izložena tim spojevima. U radu je opisana raspodjela BTEX-a u okolišu, metode određivanja BTEX-a u biološkim uzorcima i dosad objavljene koncentracije BTEX-a u krvi i urinu opće populacije. Navedeni su i toksični učinci BTEX-a na zdravlje ljudi, ali povezani samo s profesionalnom izloženošću.
Koncentracije BTEX-a u biološkim uzorcima opće populacije odražavaju onečišćenost okoliša tim spojevima.
Benzén má hematotoxické účinky, poškodzuje centrálnu nervovú sústavu a imunitný systém, je karcinogénom kategórie 1 a mutagénom kategórie 2. Expozícia benzénu je limitovaná hygienickými predpismi. V ...súbore 99 pracovníkov exponovaných benzénu a 19 neexponovaných (kontrolná skupina) boli v moči stanovené dva biomarkery benzénovej expozície rôznymi analytickými metódami. Kyselina trans,trans-mukonová bola stanovená chromatograficky a fenol spektrofotometricky. Cieľom štúdie bolo porovnať mieru ich vylučovania v oboch sledovaných skupinách a dokázať vhodnosť chromatografického stanovenia kyseliny trans,trans-mukonovej v moči ako rýchly a spoľahlivý biomonitoring pracovného prostredia. Priemerná koncentrácia fenolu v oboch skupinách sa pohybovala na fyziologickej úrovni. V skupine exponovaných benzénu bola priemerná koncentrácia fenolu vyjadrená ako Priemer (SD) 11,07 (8,51) mg.g-1 kreatinínu, v kontrolnej skupine bola 12,16 (11,42) mg.g-1 kreatinínu. Priemerná koncentrácia kyseliny trans,trans-mukonovej exponovaných pracovníkov bola 0,64 (0,95) mg.g-1 kreatinínu, v porovnaní s kontrolnou skupinou 0,29 (0,24) mg.g-1 kreatinínu, jej obsah v moči exponovaných pracovníkov nepresahoval doporučenú hodnotu koncentračného limitu pre úroveň technickej smernej hodnoty benzénu v zmysle legislatívy platnej v SR, ale prekračoval doporučenú biologickú medznú hodnotu podľa Americkej rady vládnych hygienikov pre priemysel. Štatisticky t-testom bol potvrdený signifikantný rozdiel v nameraných hodnotách vylučovanej kyseliny trans,trans-mukonovej medzi kontrolnou skupinou pacientov a pracovníkov exponovaných benzénu, dokazujúci vhodnosť jej stanovenia ako rýchly a spoľahlivý biomonitoring pracovného prostredia.
Benzene has hematoxic effects, causes damage to the central nervous system and immune system, is classified as a Category 1 carcinogen, and a Category 2 mutagen. Benzene exposure is limited by public health legislation. A total of 99 biological samples of benzene-exposed workers and 19 biological samples of non-exposed patients in a control group were examined. Concentration determination of two selected biomarkers of benzene exposure was performed using two different analytical methods. Trans,transmuconic acid was determined by chromatography and phenol was determined by spectrophotometry. The purpose of the study was to compare their excretion rate in both monitored groups, and to prove appropriateness of chromatographic determination of trans,trans-muconic acid in urine for quick and reliable biomonitoring of the working environment. The average phenol concentration in both groups varied at physiological levels: mean (SD) was 11.07 (8.51) mg.g-1 creatinine for a benzene-exposed group, and 12.16 (11.42) mg.g-1 creatinine for a control group. As for trans,trans-muconic acid, the average concentration was 0.64 (0.95) mg.g-1 creatinine in case of benzene-exposed workers compared to 0.29 (0.24) mg.g-1 creatinine for a control group. Concentration of trans,trans-muconic acid in urine from exposed workers did not exceed a recommended concentration limit for Threshold Limit Value level for benzene, but exceeded a recommended Biological Exposure Indices value set by the American Conference of Governmental Industrial Hygienists. A statistic t-test revealed a significant difference in measured values of excreted trans,transmuconic acid between a control group of patients and benzene-exposed workers proving appropriateness of determination for quick and reliable bio-monitoring of the working environment.
Ivica Bajusová, Peter Kolarčik, Michal Ihnatko, Tatiana Kimáková, Ľubomír Legáth
Literatura Ivica Bajusová, Peter Kolarčik, Michal Ihnatko, Tatiana Kimáková, Ľubomír Legáth: Porovnanie miery vylučovania vybraných biomarkerov expozície benzénu. Hygiena, 2013, roč. 58, č. 2, str. 70-74.
Štetni agensi pri proizvodnji anoda Doko Jelinić, Jagoda; Lasić, Ivo; Nola, Iskra Alexandra ...
Arhiv za higijenu rada i toksikologiju,
06/2008, Volume:
59, Issue:
2
Paper
Open access
Cilj je rada procijeniti učinak modernizacije tehnološkog procesa u Tvornici anoda na prisutnost i razinu koncentracije prašine i plinova štetnih za zdravlje radnika u radnom okolišu, kao i na ...poslove s velikim potencijalom za izloženost zaposlenih. U tu svrhu uspoređivani su rezultati obveznih periodičkih mjerenja kemijskih čimbenika provedeni prije i nakon modernizacije. Mjerenja su provedena na istim radnim mjestima i istim metodama tijekom radnih smjena i uspoređeni sa sadašnjim nacionalnim Standardom. Prije modernizacije, koncentracije ukupne prašine i plinova: ugljikova(II) oksida, ugljikova(IV) oksida, sumporova(IV) oksida, fluorovodika, benzena i fenola prelazile su preporučene vrijednosti u 56,9 % uzoraka, a nakon modernizacije u 12,3 % (21/171) uzoraka. Prije modernizacije radnici su istodobno na velikom broju radnih mjesta svih odjela bili izloženi prekomjernim koncentracijama štetnih kemijskih čimbenika. Nakon modernizacije prašina je i dalje prisutna u visokim koncentracijama pri pečenju anoda (GM=22,1 mg m-3), kao i pri zalijevanju anoda (GM=22,1 mg m-3), a geometrijska sredina koncentracije fluorovodika pri zalijevanju anoda iznosi 4,2 mg m-3, dok je sumporov(IV) oksid prisutan u svim fazama proizvodnje anoda u koncentracijama štetnim za zdravlje radnika. Modernizacijom tehnološkog procesa smanjene su prisutnost i koncentracije kemijskih čimbenika u radnom okolišu. Međutim, izloženost prašini, sumporovu(IV) oksidu i fluorovodiku samo je djelomično smanjena.
Synthesis gas conversion on hybrid catalysts composed of a physical mixture of methanol synthesis catalyst (Pd/SiO2) and acid treated or steam treated mordenites, was studied. Acidic properties of ...the zeolites which are summarized in Table 1 show that aluminium contents and acidities of acid treated mordenite, DAM-1 and DAM-2, are much smaller than those of their parent mordenite, H-M. This fact indicates that aluminium was extracted from H-M by the acid treatment to destroy mainly Brönsted acid site. Also, the treatment caused an increase in the fraction of strong acid site (fraction of acid site which holds ammonia up to 300°C or above). In contrast, remarkable amount of acid site was destroyed by steam treatment 450°C, 2h) supposedly by hydrolysis whereas little aluminium was extracted. For instance, the aluminium content of St. DAM-1 is on the same level of that of DAM-1 but the acidity of St. DAM-1 is one third of that of DAM-1. IR spectra of adsorbed pyridine on zeolites (Figs. 3-6) show that hydrogen bonded pyridine (H-acid) was increased by either the acid treatment or the steam treatment. The H-acid site, on which ammonia is not chemisorbed, is most favorably attributed to a silanol group which is formed by the hydrolysis of the structure of Al-O-Si or Si-O-Si. Results of synthesis gas conversion on the hybrid catalysts containing the modified mordenites (Table 3) is characterized by the products being mostly composed of light paraffins and polymethylbenzenes. While the selectivities to aromatic hydrocarbons plus coke on the hybrid catalyst are on the same level (ca. 35%) for all catalysts tested, the selectivities to coke on the hybrid catalyst containing DAM-1 and especially St. DAM-1 are much smaller than those on the hybrid catalyst containing H-M or DAM-2 (Fig. 9). The fact indicates that aromatic hydrocarbons are formed simultaneously with aliphatic hydrocarbons then they are converted successively to coke. The reductions of coke formation on zeolites by either the acid treatment or the steam treatment are most likely attributed to the reduction of the affinity of the zeolite for aromatic hydrocarbons (Fig. 8), which are caused by the decrease in the acidity and the increase in the hydroxyl group.
The ultimate biodegration of linear alkylbenzene sulfonate (LAS) in the act ivated sludge process has been studied using the 14C ring-labeled LAS. By using the methylene blue method and the tracer ...method, primary degradation and benzene ring degradation were evaluated respectively. In batch experiments, 30-40% of ring carbon was converted to carbon dioxide after 24 hrs' aeration in the acclimated system, but only 2-10% in the unacclimated system. 14CO2 evolution and primary degradation proceeded simultaneously, but the rate of 14CO2 evolution was slow. In 24 hrs, primary degradation proceeded completely, 46-52% of ring carbon remained in the sludge and 14-18% in the solution in the acclimated system. 14CO2 evolution rate was affected by addition of glucose and initial concentration of LAS. This study shows the biodegradation mechanism of LAS in the activated sludge process.
PDF
