Model hydrocarbon total oxidation

The time-series analysis results of Merz et were expressed in first-order empirical formulas for the most part. Forecasting expressions were developed for total oxidant, carbon monoxide, nitric oxide, and hydrocarbon. Fitting correlation coefficients varied from 0.547 to 0.659. As might be expected, the best results were obtained for the primary pollutants carbon monoxide and nitric oxide, and the lowest correlation was for oxidant. This model relates one pollutant to another, but does not relate emission to air quality. For primary pollutants, the model expresses the concentrations as a function of time. 

Continuous analysis instruments equipped with flame ionization, chemiluminescence, and infrared detectors were used to measure the concentrations of total hydrocarbons, nitrogen oxides and carbon monoxide, respectively. The concentration of total hydrocarbons was measured by a JUM FID 3-300 hydrocarbon analyzer with a flame ionization detector. NO, NO2 and NOx was measured by an ECO Physics CLD 700 EL-ht chemiluminescence detector. CO was measured with either a Beckman Industrial Model 880 non-dispersive infrared instrument or an NDIR instrument from Maihak (UNOR 6N). 

On-line analysis of the effluent gases was conducted using a gas chromatograph (Hewlett Packard model 5890 Series H), equipped with FID and TCD detectors. A DB-624 fused silica capillary column was used for the hydrocarbon separation. The carbon monoxide and carbon dioxide were separated using molecular sieves (5A) and Hayesep R columns. Tlie effluent gases were analyzed for the unconverted VOCs, partial oxidation products such as chloroform and 1,1,2-trichlorocthanc, and total oxidation products (CO and COj). The HO and Clj analysis was performed using Drager tubes. The total conversion is based on total cartoon atoms in the feed. 

A model for a similar membrane reactor, shown schematically on the top of Figure 5.15, has been developed by Harold et al [5.54] to simulate reactant and products concentrations in parallel-consecutive reaction networks. The membrane reactor compartments on either side of the membrane were assumed to be completely stirred with no pressure gradient across the membrane. The model reaction studied is of relevance to hydrocarbon partial oxidation reactions, where the intermediate oxidation product can further react with oxygen to produce the undesirable total combustion products. Here the goal is to maximize the yield of the intermediate desired product. The calculation results... 

Langhendries et al [5.74] analyzed the liquid phase catalytic oxidation of cyclohexane in a PBMR, using a simple tank-in-series approximate model for the PBMR. In their -reactor the liquid hydrocarbon was fed in the tubeside, where a packed bed of a zeolite supported iron-pthalocyanine catalysts was placed. The oxidant (aqueous butyl-hydroperoxide) was fed in the shellside from were it was extracted continuously to the tubeside by a microporous membrane. The simulation results show that the PBMR is more efficient than a co-feed PBR in terms of conversion but only at low space times (shorter reactors). A significant enhancement of the organic peroxide efficiency, defined as the amount of oxidant used for the conversion of cyclohexane to the total oxidant converted, was also observed for the PBMR. It was explained to be the result of the controlled addition of the peroxide, which gives low and nearly uniform concentration along the reactor length. 

Estimates of annual amounts of emissions released into the earth s atmosphere are remarkably different from each other, depending on the choice of balance models [5-24]. For the anthropogenic sources, the following substances may be listed in decreasing order of importance carbon dioxide, carbon monoxide, sulphur oxides, hydrocarbons, nitrogen oxides and liquid and solid particles. A summary of relative contributions of these substances to total emissions of main types of anthropogenic sources is given in Table 5.8. 

An interesting point regarding OCM is that the membrane material itself may act as a total oxidation catalyst, thus unintentionally turning the PBMR into a PBCMR. Lu et pre-treated their dense membrane with an OCM catalyst to prevent contact between hydrocarbons and the membrane oxide material. Coronas et al. carried out experiments to estimate the contribution from the membrane and used it to modify their model of OCM in a porous membrane. They found that the predicted advantage of the membrane reactor was decreased if the catalytic activity of the membrane was taken into account, and suggested the development of inert membrane reactor materials, and more active OCM catalysts, as possible remedies. 

Ndifor, E.N., Garcia, T., Solsona, B., and Taylor, S.H. (2007) Influence of preparation conditions of nano-crystalline ceria catalysts on the total oxidation of naphthalene, a model polycyclic aromatic hydrocarbon. Appl. Catal B Environ., 76 (3 4), 248 256. 

Using cobalt nitrates as precursor, the possible cobalt insertion in the srrrface ceria lattice leads to a synergistic coupling of the redox properties of ceria and C03O4. By the addition of ethylenediamine during the catalyst preparation, Co species do not enter in the ceria due to the preliminary formation of Co-ethylenediamine complex, but rather contribute to well dispersed C03O4 phase after activation treatment. Consequently CoEn is more active than CoNit in the propylene (model molecule to mimic the total catalytic oxidation of a VOC of hydrocarbon type) total oxidation the T50 is lowered by 20°C. 

In this chapter a two a selectivity model is proposed that is based on the premise that the total product distribution from an Fe-low-temperature Fischer-Tropsch (LIFT) process is a combination of two separate product spectrums that are produced on two different surfaces of the catalyst. A carbide surface is proposed for the production of hydrocarbons (including n- and iso-paraffins and internal olefins), and an oxide surface is proposed for the production of light hydrocarbons (including n-paraffins, 1-olefins, and oxygenates) and the water-gas shift (WGS) reaction. This model was tested against a number of Fe-catalyzed FT runs with full selectivity data available and with catalyst age up to 1,000 h. In all cases the experimental observations could be justified in terms of the model proposed. 

The detailed model was constructed as described by Carslaw et al. (1999, 2002). Briefly, measurements of NMHCs, CO and CH4 were used to define a reactivity index with OH, in order to determine which NMHCs, along with CO and CH4, to include in the overall mechanism. The product of the concentration of each hydrocarbon (and CO) measured on each day during the campaign and its rate coefficient for the reaction with OH was calculated. All NMHCs that are responsible for at least 0.1% of the OH loss due to total hydrocarbons and CO on any day during the campaign are included in the mechanism (Table 2). Reactions of OH with the secondary species formed in the hydrocarbon oxidation processes, as well as oxidation by the nitrate radical (NO3) and ozone are also included in the... 

DOCs are important for reducing the emissions of CO and hydrocarbons from diesel vehicles (Clerc, 1996). Furthermore, these catalysts are active for the oxidation of NO to N02, which can be used in downstream systems, such as SCR and filters, where N02 concentration can be key to the total system performance. Modelling can play a role in designing optimum systems for CO, HC and NO oxidation. 

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