Showing papers by "Mexican Institute of Petroleum published in 2021"

Particle-bound PAHs and Chemical Composition, Sources and Health Risk of PM2.5 in a Highly Industrialized Area

Abstract: PM2.5 monitoring campaigns were conducted in 2006, 2010, and 2011 in Tula, Hidalgo, Mexico, a highly industrialized area which includes a refinery, a thermoelectric power plant, five cement plants, limestone mining, and industrial waste combustion. These data establish baselines and trends against which later concentrations can be compared as emission reduction plans are implemented. PM2.5 mass, chemical composition, and 15 particle-bound polycyclic aromatic hydrocarbons (PAHs) were measured at two sites. PM2.5 masses ranged from 26 to 31 µg m–3. Carbonaceous aerosols were the largest PM2.5 component, accounting for 47–57% of the mass. Approximately 40–51% of the carbonaceous aerosol was attributed to secondary organic carbon. Ionic species accounted for 40–44% of PM2.5, with sulfate being the dominant ion. The sum of particle-bound PAH concentrations ranged from 14–31 ng m–3. Six factors derived from Principal Component Analysis (PCA) explained ~85% of the PM2.5 variance. The derived factors were associated with sources based on marker species resulting in heavy-oil combustion (22% of variance), vehicle engine exhaust (13–19% of variance), fugitive dust (18% of variance), biomass burning (9–13% of variance), secondary aerosols (14% of variance), and industrial emissions (6–10% of variance). Combustion of solid waste (e.g., tires and industrial waste) of the recycling cement kilns and incinerators resulted in elevated toxic species such as, Cd, and Sb in the range of 0.02–0.3 µg m–3. A health risk assessment of carcinogenic trace elements was performed showing that the total cancer risk decreased for both children and adults in 2010/2011 (ranging from 3.5 × 10–6 to 6.0 × 10–5) as compared to 2006 (ranging from 8.6 × 10–7 to 5.7 × 10–6). The inhalation life-time cancer risk (ILCR) for particle-bound PAHs ranged from 8.6 × 10–5 to 1.2 × 10–4. Air quality can be improved by switching to cleaner fuels and benefit from the use of natural gas instead of fuel oil in the power plant.

Effect of Acicular Ferrite and Bainite in API X70 Steel Obtained After Applying a Heat Treatment on Corrosion and Cracking Behaviour

Abstract: The effect of acicular ferrite (AF) and bainite (B) obtained by heat treatment (HT) applied to an API X70 steel on corrosion resistance and stress corrosion cracking (SCC) susceptibility was evaluated through polarization curves and slow strain rate tests respectively, in NS4 solution and congenital water (CW). The HT was carried out at 1050 °C for 15 and 30 min followed by water quenching. Change of ferrite–perlite to AF and B was observed as result of heat treatment applied to X70 steel. Effect of HT time in terms of microstructure obtained was analysed. The mechanical properties obtained by the HT are higher than X100 steel. HT-30 min improve the corrosion resistance of X70 steel exposed to both solutions, which are related to coarse and homogeneous microstructure of AF and B. Localized corrosion was observed in the steel exposed to both solutions. HT-15 min improve mechanical properties and higher content of fine AF, but decreases SCC resistance. Steel with higher content of fine AF microstructure is more susceptible to SCC. SCC indexes revealed that the heat-treated steel could be susceptible to SCC in CW confirmed by the secondary cracks observed. The SCC mechanism was hydrogen embrittlement. Meanwhile, steel HT by 15 min exposed to NS4 solution could be susceptible to SCC. Crack growth rate was higher in steel HT by 15 min, which are related to more fine and brittle AF microstructure.

DEMS and RAMAN study of the monatomic hydrogen adsorption during electro-reduction of NO3- and NO2- at Pt nanoparticles supported at W18O49-ZrO2-C nanocomposite

Abstract: A multifunctional hybrid material composed of W18O49 nanobelts (NBs), zirconium oxide, and Vulcan carbon (W18O49-ZrO2-C) has been used as support for platinum nanoparticles (PtWZC). For comparison, platinum supported on Vulcan carbon (PtC) was also synthesized. These catalysts were evaluated in the NO3- and NO2- (NOx) reduction reactions. The addition of W18O49 and ZrO2 to the carbon improved the size and distribution of the platinum nanoparticles. The electrochemical results showed that enhanced electrocatalytic activity for the NOx reduction was obtained on the PtWZC catalyst compared to PtC synthesized by the same technique and PtEtek from a commercial source. Our findings suggest that the adsorbed monatomic hydrogen (Hads) over platinum inhibits the reduction of nitrates and nitrites. Therefore, these reactions need a material that removes Hads from the surface or modifies it for the NOx reduction. The WZC support adsorbed monatomic hydrogen from water to form active bronze species (Hx-W18O49) that interacted with the NO3- and NO2- ions enabling their reduction, in accord with the results from in-situ Raman spectroscopy and Tafel slopes. N2, NO, NH3, and N2H4 products were detected in nitrite ion reduction by the Differential electrochemical mass spectrometry (DEMS) technique on the PtWZC catalyst. The production of N2 dominated in the cathodic and anodic scan. Hence, the novel catalyst can follow the indirect pathway, where the reduction process involves adsorption of NHx and adsorption of NO. The higher electrocatalytic activity obtained by the PtWZC catalyst was attributed to the uniform distribution of platinum on the support, the increased electrical conductivity produced by the W18O49 nanobelts, and the modulation of Hads on the surface.

Evaluation of Asphaltene Stability of a Wide Range of Mexican Crude Oils

Abstract: Appropriate prediction of asphaltene stability can anticipate operational problems such as plugging of lines and process equipment (pumps, heat exchangers, separation tanks, among others), thus ass...

Discerning the Metal Doping Effect on Surface Redox and Acidic Properties in a MoVTeNbO x for Propa(e)ne Oxidation.

Abstract: Adding a small quantity of K or Bi to a MoVTeNbO x via impregnation with inorganic solutions modifies its surface acid and redox properties and its catalytic performance in propa(e)ne partial oxidation to acrylic acid (AA) without detriment to its pristine crystalline structure. Bi-doping encourages propane oxydehydrogenation to propene, thus enlarging the net production rate of AA up to 35% more. The easier propane activation/higher AA production over the Bi-doped catalyst is ascribed to its higher content of surface V leading to a larger amount of total V5+ species, the isolation site effect of NbO x species on V, and its higher Lewis acidity. K-doping does not affect propane oxydehydrogenation to propene but mainly acts over propene once formed, also increasing AA to a similar extent as Bi-doping. Although K-doping lowers propene conversion, it is converted more selectively to acrylic acid owing to its reduced Bronsted acidity and the presence of more Mo6+ species, thereby favoring propene transformation via the π-allylic species route producing acrylic acid over that forming acetic acid and CO x via acetone oxidation and that yielding directly CO x .

Synthesis and characterization of highly dispersed bimetallic Au-Rh nanoparticles supported on titanate nanotubes for CO oxidation reaction at low temperature

Abstract: Low-temperature CO oxidation was carried out by using rhodium incorporated into titanate nanotubes (Rh/NTs) prepared by the sol-gel and hydrothermal methods; otherwise, gold nanoparticles were deposited homogeneously onto the Rh/NT surface through the deposition-precipitation with urea (DPU) method. The Au-Rh/NT sample exhibited high metal dispersion (55%), outstanding CO oxidation at low temperature, and better resistance to deactivation than the monometallic Rh/NT and Au/NT samples. The characterization of bimetallic samples, with particle sizes from 1 to 3 nm, revealed the remarkable presence of interacting Au and Rh species in metallic state. In this way, Au0 and Rh0 were answerable for the higher catalytic activity observed in the bimetallic samples. The interaction between Au and Rh in the nanoparticles of Au-Rh/NT promoted a synergistic effect on the CO oxidation reaction, explained by the creation of new CO adsorption sites.

Effect of the catalyst in the BTX production by hydrocracking of light cycle oil

Abstract: Catalysts to produce the important petrochemicals like benzene, toluene, and xylene (BTX) from refinery feedstocks, like light cycle oil (LCO) are reviewed here by covering published papers using model mixtures and real feeds. Model compounds experiments like tetralin and naphthalene derivatives provided a 53–55% total BTX yield. Higher yields were never attained due to the inevitable gas formation and other C9+-alkylbenzenes formed. For tetralin, the best catalysts are those conformed by Ni, CoMo, NiMo, or NiSn over zeolite H-Beta. For naphthalene derivatives, the best catalysts were those conformed by W and NiW over zeolite H-Beta silylated. Real feeds produced a total BTX yield of up to 35% at the best experimental conditions. Higher yields were never reached due to the presence of other types of hydrocarbons in the feed which can compete for the catalytic sites. The best catalysts were those conformed by Mo, CoMo, or NiMo over zeolite H-Beta. Some improvements were obtained by adding ZSM-5 to the support or in mixtures with other catalysts.

Ultrasound-Assisted Hydrothermal Synthesis of V2O5/Zr-SBA-15 Catalysts for Production of Ultralow Sulfur Fuel

Abstract: This work reports the results of the ultrasound-assisted hydrothermal synthesis of two sets of V2O5 dispersed on SBA-15 and Zr doped SBA-15 catalysts used for the oxidation of dibenzothiophene (DBT) in a model diesel via the combination of oxidation, catalysis, and extraction technical route. These catalysts contained Lewis acidity as major and Bronsted acidity as minor. The amount of acidity varied with the content of vanadia and zirconium doping. It was found that DBT conversion is very sensitive to the Lewis acidity. DBT conversion increased by increasing the vanadium content and correlated well with the amount of surface Lewis acidity. Under the optimal experimental condition (Reaction temperature: 60 °C, reaction time 40 min, catalyst concentration: 1 g/L oil; H2O2/DBT mole ratio = 10), the 30% V2O5/SBA-15 and 30% V2O5/Zr-SBA-15 catalysts could convert more than 99% of DBT. Two reaction pathways of DBT oxidation involving vanadia surface structure, Lewis acidity, and peroxometallic complexes were proposed. When the vanadia loading V2O5 ≤ 10 wt%, the oxidative desulfurization (ODS) went through the Pathway I; in the catalysts with moderate vanadia content (V2O5 = 20–30 wt%), ODS proceeded via the Pathways II or/and the Pathway I.

The Helicenes: Potential Carriers of Diffuse Interstellar Bands

Abstract: In this work, the helicenes are postulated as potential carriers of the diffuse interstellar bands, DIBs. The helicenes are nonplanar cata-condensed molecules structurally related to the polyacenes...