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Economic and environmental aspects render nitrogen removal from oil loads increasingly more necessary. Studies have proven that it is possible to achieve high selectivity to quinoline hydrodenitrogenation products using PtMo bimetallic catalysts supported on zeolites. However, the reaction follows the route of higher hydrogen consumption. The main products in this reaction are propylcyclohexene, propylbenzene, and propylcyclohexane, being more selective for propylcyclohexane, which is directly related to increased hydrogen consumption. Therefore, the identification of the best conditions of temperature and hydrogen flow to make the process more selective for propylbenzene is of interest. The study conducted in UniSim® Software showed considerable improvements in selectivity with increasing the temperature of reaction between 450 and 500 °C. Additionally, the catalytic tests confirmed that the bimetallic catalyst reached higher selectivity when the temperature of 460 °C was used, as determined by simulation. The experimental results and the simulation analysis showed that molybdenum in catalysts is essential for HDN reactions and that temperature is a key factor toward propylbenzene selectivity. [ABSTRACT FROM AUTHOR]

Livestock wastewater contains a large amount of nutrients that are available for recovery. In this study, a proof of concept process based on forward osmosis (FO) was proposed and investigated for in situ formation of struvite from digested swine wastewater. This FO system took advantage of a drawback – reverse solute flux (RSF) and used the reverse-fluxed Mg 2+ for struvite precipitation, thereby accomplishing recovery of both water and nutrient. With 0.5 M MgCl 2 as a draw solution, high-purity struvite formed spontaneously in the feed solution and the water flux through the FO membrane reached 3.12 LMH. The precipitated struvite was characterized and exhibited a similar composition to that of commercial struvite. The FO system achieve >50% water recovery and >93% ammonium nitrogen removal from the digested swine wastewater; in particular, it obtained >99% phosphate recovery, much higher than 60.7% removal via direct MgCl 2 addition (without FO treatment). The recovered products (both struvite and water) could potentially generate a value of 1.35 $ m −3 . The results of this study have demonstrated the feasibility of nutrient recovery from livestock wastewater promoted by FO treatment. [ABSTRACT FROM AUTHOR]

To elucidate the catalytic mechanism and nitrogen transfer behavior of sewage sludge (SS) during catalytic fast pyrolysis (CFP), product distributions and nitrogen transformation from SS and amino acids during CFP were investigated on a drop tube quartz reactor at various temperatures and HZSM-5 catalysts. Phenylalanine (Phe), proline (Pro), leucine (Leu) and aspartic acid (Asp) were employed as model compounds with different chemical structures for protein-rich SS to help analyze catalytic cracking behavior of SS. During CFP of SS, the maximum aromatics yield of 16.4% was obtained over HZSM-5 with Si/Al ratio of 25 at 500 °C, and increasing temperature promoted the conversion of nitrogen to NH 3 . Amino acids with aromatic ring or saturated hydrocarbon side chain such as Phe and Leu in SS favored the formation of aromatics and NH 3 . Amino acids of N -ring structure in SS promoted the formation of N -containing heterocyclic compounds, which were prone to coke on catalyst and inhibited the catalytic cracking of SS to produce more aromatics and NH 3 . In addition, excessive Asp of short chain dibasic acid structure in SS was not conducive to the complete thermal decomposition of SS under the optimum pyrolysis condition. A general catalytic mechanism of SS was proposed to provide support for the resource reuse of SS. [ABSTRACT FROM AUTHOR]

This study investigated the effect of N-acyl-L-homoserine lactones (AHLs) and EPS on anammox activity, and identified the relationship between AHLs and EPS. The effects of AHLs and different EPS fractions (loosely bound (LB) and tightly bound (TB) EPS) from denitrification sludge (DS) and perchlorate reducing sludge (PRS) on anammox activity were conducted by batch experiments. Compared with the control experiment, the nitrogen removal rate was increased by 82.0%, 73.9% and 73.0%, respectively, when adding DS-EPS (integral DS EPS), PRS-EPS (integral PRS EPS) and DS-LB in anammox biomass. EPS fractions of DS and PRS contained the same kinds of AHLs, including C4-HSL, C6-HSL and C8-HSL, as identified by HPLC-MS. C4-HSL and C6-HSL at 0.1 mg L −1 concentration effectively improved the nitrogen removal rate by induceing the expression of anammox active genes during the anammox process. This study provides a new idea for efficient nitrogen removal from anammox bacteria. [ABSTRACT FROM AUTHOR]

Treatment wetlands have been proved to be more effective than conventional treatment processes in case of high-strength wastewater containing high concentrations of ammonium nitrogen and recalcitrant organic matter. In this study nitrogen removal processes and reliability of nitrogen removal at two identical pilot-scale multistage treatment wetlands (MTWs) receiving real, non-synthetic wastewater were discussed. The wastewater discharged to pilot-scale subsurface flow MTWs contained high ammonium nitrogen concentrations and limited biodegradable organic matter (OM) concentrations. One of the pilot MTWs was fed with landfill leachate (LL) and another one with reject water from sewage sludge centrifugation (RW). In the first season of operation both MTWs reached very high (95–99%) efficiency of total nitrogen (TN) removal, which was explained by adsorption to the substrate. In the later period, TN was removed in a sequence of nitrification and denitrication processes with lower efficiency (40–86%). The denitrification process was the limiting one at the LL treating site because of too low carbon supply. Still, during the whole investigation period TN outflow concentrations were at the level that allows for co-treatment of the effluent in municipal wastewater treatment plants without risk for biological treatment processes. In 90% of samples TN concentration was below 200 mg/l and in 60% of samples it was below 145 mg/l. [ABSTRACT FROM AUTHOR]

The short-cut nitrification (SCN) performance of an airlift reactor (ALR) was investigated under increasing bicarbonate condition. The sequential increase of bicarbonate from 2.5 to 7.0 g/L accelerated the nitrite accumulation and improved the NAP to 99 %. With the increase of bicarbonate dose to 11 g/L, the ammonium removal efficiency and the ammonium removal rate (ARR) were improved to 95.1 % and 0.57 kg/m/day, respectively. However, the elevation of bicarbonate concentration from 11.0 to 14.0 g/L gradually depreciated the nitrite accumulation percentage to 62.5 %. Then, the reactor was operated in increasing ammonium strategy to increase the nitrogen loading rate (NLR) to 1.1 kg/m/day under 700 mg/L influent ammonium concentration. The ARR and nitrite production rate were elevated to 1.1 and 0.9 kg/m/day, respectively. The SCN performance was improved to 1.8 kg/m/day (NLR) by the subsequent progressive shortening of HRT to 4.8 h at ammonium concentration of 350 mg/L, which was 1.6 times higher than that of the increasing ammonium strategy. Chemical analysis with EDS, FTIR and XRD confirmed the presence of CaCO precipitates on biomass surface during the long-term operation under high bicarbonate conditions. The attachment of precipitates to the SCN sludge helped to improve the biomass settleability and finally enhanced the SCN performance of the ALR. [ABSTRACT FROM AUTHOR]

This work presents a theoretical investigation of the use of nanoporous carbon membranes for the separation of nitrogen from natural gas. A mathematical model to predict the performance of the membrane is developed. The model is a combination of the well known dusty gas model, which describes the transfer of multi-components mixture in porous media, together with a surface diffusion model. The model is first validated using the literature results for the separation of hydrogen from hydrocarbons mixture. The model is then applied to the nitrogen-hydrocarbons system. The membrane performance is evaluated in terms of nitrogen recovery, methane loss, nitrogen purity, as well as hydrocarbons compositions in both permeate and retentate sides. The model calculation methods are applied for both co-current and counter-current flow configurations. A parametric study is also carried out to investigate the effects of membrane parameters such as feed and permeate pressures and porosity on the membrane performance. The developed model is general and can be applied to various nanoporous membrane flow patterns. [ABSTRACT FROM AUTHOR]

Functionalized polymers, which consist of polymer support, linker, and π-acceptor, have shown promising results in removing nitrogen and sulfur compounds from heavy gas oil via charge transfer complex (CTC) mechanism. In this work, the effect of polymer support in the efficiency and selectivity of the functionalized polymers toward nitrogen removal was studied by synthesizing three different polymers, consisting of hydrophilic and hydrophobic polymer supports, with the same linker and π-acceptor. Hydrazine (-H 2 N-NH 2 ) and 2,4,5,7-Tetranitro-9-fluorenone (TENF) were chosen as the common linker and π-acceptor, respectively. The polymer supports were: polyacrylamide (PAM), polystyrene-co-divinylbenzene (PS-DVB), and polyglycidyl methacrylate-co-ethylene glycol dimethacrylate (PGMA-co-EGDMA). In the first stage, the functionalized polymers, PGMA-NN-TENF, PS-NN-TENF, and PAM-NN-TENF, were synthesized and characterized using different methods and techniques including Fourier Transform Infrared Spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis/Differential Thermal Analysis (TGA/DTA), CHNS elemental analysis, and Nuclear Magnetic Resonance (NMR) spectroscopy. A Nitrogen/Sulfur analyzer was used to determine total nitrogen and sulfur adsorption by the synthesized polymers in 4 different feeds: model compound (MC), light gas oil (LGO), heavy gas oil (HGO), and a blend of heavy and light gas oil (BGO). Results have shown that PGMA was the best polymer support with LGO, HGO, and BGO feeds, while PS-DVB showed the highest nitrogen removal with MC feed. The higher efficiency and selectivity of PGMA-NN-TENF toward nitrogen species, in the presence of sulfur and other aromatic species in the feed, were due to the combination of hydrophilic nature and high surface area of PGMA-NN-TENF compared to other polymers. Modifying the pretreatment conditions of the polymers with BGO feed showed that increasing temperature, contact time, and polymer to oil ratio increased the efficiency of the PGMA-NN-TENF polymer. [ABSTRACT FROM AUTHOR]

Cu-SSZ-13/cordierite monolithic catalyst was prepared by in situ hydrothermal synthesis method. The physicochemical properties of the as-prepared Cu-SSZ-13/cordierite were investigated by X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, N 2 -adsorption, inductively coupled plasma, X-ray photoelectron spectroscopy, and solid-state NMR techniques. The removal of nitrogen oxides (NO x ) from simulated diesel vehicle exhaust gas was performed using fixed-bed reactor. The effects of crystallization time and addition of HF during hydrothermal synthesis, reaction space velocity, and aging treatment of catalyst on the catalytic performances of NO x reduction reactions were investigated. The results indicate that the optimum crystallization time was 72 h. Highly crystalline structure of zeolite Cu-SSZ-13 was formed, in a close combination with a carrier, via one step hydrothermal process. Cu-SSZ-13/cordierite showed excellent DeNO x performance for selective catalytic reduction (SCR) and anti-aging properties in a simulated diesel exhaust gas under a high space velocity. At a high space velocity of 72,000 h −1 , the highest conversion and N 2 selectivity of 94% and 90%, respectively, were achieved. After the aging for 50 h at 720 °C, NO x reduction rate was still >80% in the temperature range of 350–550 °C. The larger height to diameter ratio of the same catalysts enhanced the NH 3 -SCR catalytic activity and broadened the active temperature window. The addition of HF increased the catalytic activity and anti-aging performance of the sample. [ABSTRACT FROM AUTHOR]

Under laboratory conditions, nitrogen adsorption from the coking wax oil was studied respectively by D72 and D001-CC cationic activation resins as adsorbents in a continuous fixed bed reactor. Micro reaction system of fluid catalytic cracking unit was used to study the catalytic racking reaction performance of coking wax oil after denitrification. Adsorption properties of two kinds of activation resin were compared by studing the adsorption breakthrough curve in the fixed bed, the dynamic adsorption properties of alkaline nitrogen compounds in the coking wax oil and the affect of the adsorption temperature on the removal rate of basic nitrogen compounds. Catalytic cracking performances of coking wax oil before and after denitrification were finally compared with catalytic cracking experiments. Results of experiments showed that the optimum adsorption temperature of D001-CC activation resin was 70 °C, the adsorption capacity was saturated 6 hours later, and the saturated adsorption capacity is 19. 35 mg/g. The optimum adsorption temperature of D72 activation resin was 60 °C,the adsorption capacity was saturated 5 hours after, and the saturated adsorption capacity was 7. 75 mg/g. The degree of catalytic cracking of coking wax oil deepened and the conversion rate improved after dealing with the resin denitrification. When the reaction temperature was 400 °C, the conversion rate of coking wax oil without denitrification was 44%. The conversion rate of coking wax oil reached 81. 5% after 30 minute's adsorption denitrification treatment. The influences of alkaline nitrogen content on catalyst activity were more sensitive at higher reaction temperature. The more substantially decrease of alkaline nitrogen content in the coking wax oil, the more significantly increases of catalytic cracking conversion rates. [ABSTRACT FROM AUTHOR]

The influence of the metal ion in the mesoporous metal trimesate MIL-100(Al3+, Cr3+, Fe3+, V3+) on the adsorptive removal of N/S-heterocyclic molecules from fuels has been investigated by combining isotherms for adsorption from a model fuel solution with microcalorimetric and IR spectroscopic characterizations. The results show a clear influence of the different metals (Al, Fe, Cr, V) on the affinity for the heterocyclic compounds, on the integral adsorption enthalpies, and on the uptake capacities. Among several factors, the availability of coordinatively unsaturated sites and the presence of basic sites next to the coordinative vacancies are important factors contributing to the observed affinity differences for N-heterocyclic compounds. These trends were deduced from IR spectroscopic observation of adsorbed indole molecules, which can be chemisorbed coordinatively or by formation of hydrogen bonded species. On the basis of our results we are able to propose an optimized adsorbent for the deep and selective removal of nitrogen contaminants out of fuel feeds, namely MIL-100(V). [ABSTRACT FROM AUTHOR]

Highlights: [•] CH4 molecules can only form weak interactions with B12 cluster, α-B12 and γ-B28 surfaces. [•] N2 forms relative strong interaction with these boron adsorbents. [•] These boron adsorbents have very high selectiveness to capture N2 from natural gas. [•] The boron adsorbents can be promising materials for natural gas purification. [ABSTRACT FROM AUTHOR]

The coke wax oil is treated by PDN denitriying agent, the rate of removing nitrides is 64. 3% and the yield of the denitrifying wax oil is 97. 3% when dose -- oil ratio is 1 : 100. The evaluation results of small -- scale unit of FCC indicate that the yield of the light fuel oil distillate increased by 7. 65% and the total yield of the liquid fuel oil distillate increased by 9. 80% at the same condition by comparing combined process of the complex denitrifying and FCC with the pure FCC treating. Treating coke wax oil by complexing denitrifying reaction, it decreases the poison of FCC catalysts and increases the yield of the light fuel oil. [ABSTRACT FROM AUTHOR]