Ammoxidation Process Research Articles

Energy-Saving Ambient Electrosynthesis of Nylon-6 Precursor Coupled with Electrocatalytic Upcycling of Polyethylene Terephthalate.

Cyclohexanone oxime is an important intermediate in the chemical industry, especially for the manufacture of nylon-6. The traditional cyclohexanone oxime production strongly relies on cyclohexanone-hydroxylamine and cyclohexanone ammoxidation processes, which require harsh reaction conditions and consume considerable amounts of energy. Herein, direct electrosynthesis of cyclohexanone oxime is reported from environmental pollutants nitrite and cyclohexanone with almost 100% yield by using low-cost Cu2Se nanosheets as electrocatalysts. Combination of in situ Fourier transform infrared spectroscopy and theoretical calculations verifies that the p-d orbital hybridization between Cu and Se elements could synergistically optimize the surface electronic structure and enable improved adsorption and formation of the key active N intermediate NH2OH*, thereby enhancing cyclohexanone/nitrite-to-cyclohexanone oxime conversion over the Cu2Se nanosheets. Based on these, an efficient asymmetric co-electrolysis system is further demonstrated by coupling cyclohexanone/nitrite-to-cyclohexanone oxime conversion with the upcycling of polyethylene terephthalate plastics, achieveing energy-saving simultaneously production of value-added products (cyclohexanone oxime and glycolic acid).

Adsorption of Nitrogen Dioxide on Nitrogen-Enriched Activated Carbons.

The aim of this study was to obtain nitrogen-enriched activated carbons from orthocoking coal. The initial material was subjected to a demineralisation process. The demineralised precursor was pyrolysed at 500 °C and then activated with sodium hydroxide at 800 °C. Activated carbon adsorbents were subjected to the process of ammoxidation using a mixture of ammonia and air at two different temperature variants (300 and 350 °C). Nitrogen introduction was carried out on stages of demineralised precursor, pyrolysis product, and oxidising activator. The elemental composition, acid-base properties, and textural parameters of the obtained carbon adsorbents were determined. The activated carbons were investigated for their ability to remove nitrogen dioxide. The results demonstrated that the ammoxidation process incorporates new nitrogen-based functional groups into the activated carbon structure. Simultaneously, the ammoxidation process modified the acid-base characteristics of the surface and negatively affected the textural parameters of the resulting adsorbents. Furthermore, the study showed that all of the obtained carbon adsorbents exhibited a distinct microporous texture. Adsorption tests were carried out against NO2 and showed that the carbon adsorbents obtained were highly effective in removing this gaseous pollutant. The best sorption capacity towards NO2 was 23.5 mg/g under dry conditions and 75.0 mg/g under wet conditions.

Plastic particles affect N2O release via altering core microbial metabolisms in constructed wetlands

Constructed wetlands (CWs) have been proven to effectively immobilize plastic particles. However, little is known about the differences in the impact of varying sized plastic particles on nitrous oxide (N2O) release, as well as the intervention mechanisms in CWs. Here, we built a lab-scale wetland model and introduced plastic particles of macro-, micro-, and nano-size at 100 μg/L for 370 days. The results showed that plastic particles of all sizes reduced N2O release in CWs, with the degrees being the strongest for the Nano group, followed by Micro and Macro groups. Meanwhile, 15N- and 18O-tracing experiment revealed that the ammoxidation process contributed the most N2O production, followed by denitrification. While for every N2O-releasing process, the contributing proportion of N2O in nitrification-coupled denitrification were most significantly cut down under exposing to macro-sized plastics and had an obvious increase in nitrifier denitrification in all groups, respectively. Finally, we revealed the three mechanism pathways of N2O release reduction with macro-, micro-, and nano-sized plastics by impacting carbon assimilation (RubisCO activity), ammonia oxidation (gene amo abundance and HAO activity), and N-ion transmembrane and reductase activities, respectively. Our findings thus provided novel insights into the potential effects of plastic particles in CWs as an eco-technology.

Response of Organic Carbon Mineralization to Nitrogen Addition in Micro-aerobic and Anaerobic Layers of Paddy Soil

In field conditions, a micro-aerobic layer with 1 cm thickness exists on the surface layer of paddy soil owing to the diffusion of dissolved oxygen via flooding water. However, the particularity of carbon and nitrogen transformation in this specific soil layer is not clear. A typical subtropical paddy soil was collected and incubated with13C-labelled rice straw for 100 days. The responses of exogenous fresh organic carbon(13C-rice straw) and original soil organic carbon mineralization to nitrogen fertilizer addition[(NH4)2SO4]in the micro-aerobic layer(0-1 cm) and anaerobic layer(1-5 cm) of paddy soil and their microbial processes were analyzed based on the analysis of 13C incorporation into phospholipid fatty acid(13C-PLFAs). Nitrogen addition promoted the total CO2 and 13C-CO2 emission from paddy soil by 11.4% and 12.3%, respectively. At the end of incubation, with the addition of nitrogen, the total soil organic carbon (SOC) and13C-recovery rate from rice straw in the anaerobic layer were 2.4% and 9.2% lower than those in the corresponding micro-aerobic layer, respectively. At the early stage(5 days), nitrogen addition increased the total microbial PLFAs in the anaerobic layer with a consistent response of bacterial and fungal PLFAs. However, there was no significant effect from nitrogen on microbial abundance in the micro-aerobic layer. Nitrogen addition had no significant impact on the abundance of total 13C-PLFAs in the micro-aerobic and anaerobic layers, but the abundance of 13C-PLFAs for bacteria and fungi in the micro-aerobic layer was decreased dramatically. At the late stage(100 days), the effect of nitrogen addition on microbial PLFAs was consistent with that at the early stage. The abundances of total, bacterial, and fungal 13C-PLFAs were remarkably increased in the anaerobic layer. However, the abundance of 13C-PLFAs in the micro-aerobic layer showed no significant response to nitrogen addition. During the incubation, the content of NH4+-N in the anaerobic soil layer was higher than that in the micro-aerobic soil layer. This indicates that nitrogen addition increased microbial activity in the anaerobic soil layer caused by the higher NH4+-N concentration, as majority of microorganisms preferred to use NH4+-N. Consequently, the microbial utilization and decomposition of organic carbon in the anaerobic soil layer were accelerated. By contrast, richer available N existed in the form of NO3--N in the micro-aerobic soil layer owing to the ammoxidation process. Thus, the shortage of NO3--N preference microorganisms in the paddy soil environment prohibited the microbial metabolism of organic carbon in the micro-aerobic layer. As a whole, nitrogen fertilization enhanced organic carbon loss via microbial mineralization in paddy soil with a weaker effect in the micro-aerobic layer than that in the anaerobic layer, indicating the limited microbial metabolic activity in the surface micro-aerobic layer could protect the organic carbon stabilization in paddy soil. This study emphasizes the heterogeneity of paddy soil and its significant particularity of carbon and nitrogen transformation in micro-aerobic layers. Consequently, this study has implications for optimizing the forms and method for the application of nitrogen fertilizer in paddy cropping systems.

Environmental pollution of fluoroquinolones and its relationship with nitrogen cycling mediated by microorganisms.

Fluoroquinolone antibiotics (FQs) are one of the most widely used antibiotics, which are new pollutants with 'pseudo persistence' in the environment, causing great ecological risks. FQs could change the structure and function of microbial communities and affect nitrogen cycling mediated by microorganisms. Consequently, FQs would change the composition of various types of nitrogen in the environment and exert a significant impact on the global nitrogen cycling. We encapsulated the distribution of FQs in the environment and its impacts on nitrogen cycling mediated by microorganisms, explained the role of FQs in each key process of nitrogen cycling, aiming to provide an important reference for revealing the ecological effects of FQs. Generally, FQs could be detected in various environmental media, with significant differences in the concentration and types of FQs in different environments. Ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin are the four types of FQs with the highest detection frequency and concentration. The effect of FQs on nitrogen cycling deeply depends on typical characteristics of concentration and species. FQs mainly inhibit nitrification by reducing the abundance of amoA gene related to ammoxidation process and the abundance and composition of ammoxidation bacteria. FQs inhibits nitrification by reducing the abundance and composition of microbial communities. The denitrification process is mainly inhibited due to the reduction of the activity of related enzymes and the abundance of genes such as narG, nirS, norB, and nosZ genes, as well as the abundance and composition of denitrifying functional microorganisms. The process of anammox is restricted due to the reduction of the abundance, composition and hzo gene abundance of anaerobic anammox bacteria. FQs lead to the reduction of active nitrogen removal and the increase of N2O release in the environment, with further environmental problems such as water eutrophication and greenhouse effect. In the future, we should pay attention to the effects of low concentration FQs and complex antibiotics on the nitrogen cycling, and focus on the effects of FQs on the changes of nitrogen cycle-related microbial monomers and communities.

Relative contribution of ammonia-oxidizing bacteria and denitrifying fungi to N2O production during rice straw composting with biochar and biogas residue amendments

Nitrous oxide (N2O) production is associated with ammonia-oxidizing bacteria (amoA-AOB) and denitrifying fungi (nirK-fungi) during the incorporation of biochar and biogas residue composting. This research examined the relative contribution of alterations in the abundance, diversity and structure of amoA-AOB and nirK-fungi communities on N2O emission by real-time PCR and sequence processing. Results showed that N2O emissions showed an extreme relation with the abundance of amoA-AOB (rs = 0.584) while giving credit to nirK-fungi (rs = 0.500). Nitrosomonas and Nitrosospira emerged as the dominant genera driving ammoxidation process. Biogas residue changed the community structure of AOB by altering Nitrosomonadaceae proportion and physiological capacity. The denitrification process, primarily governed by nirK-fungi, served as a crucial pathway for N2O production, unveiling the pivotal mechanism of biochar to suppress N2O emissions. C/N and NH4+-N were identified as significant parameters influencing the distribution of nirK-fungi, especially Micromonospora, Halomonas and Mesorhizobium.

Effects of Dam Building on Niche Differentiation of Comammox Nitrospira in the Main Stream of the Three Gorges Reservoir Area

Complete ammonia oxidizers (comammox) can completely oxidize ammonia to nitrate, and the various habitats of comammox Nitrospira are an important guarantee for their survival. The construction of the Three Gorges Dam, China, made it easier for nitrogen to stay in the reservoir area, which may have caused the niche differentiation of comammox, thereby affecting the natural transformation process of nitrogen in the reservoir area. This study investigated comammox in river sediments in the Three Gorges Reservoir area. Comammox clade A and comammox clade B were detected in all samples, and comammox clade A was dominant. The number of dominant OTUs (Operational Taxonomic Unit) in comammox clade A.1 accounted for 18.69% of the total number of OTUs, followed by comammox clade A.2 (18.58%) and clade B (14.30%). The indicated abundance of comammox Nitrospira clade A and clade B amoA genes in the main stream of the Three Gorges Reservoir increased along the length of the river and reached the maximum in the middle part of the reservoir area. The highest abundance of ammonia-oxidizing archaea (AOA) amoA genes appeared in the upper stream section of the reservoir area. Comammox Nitrospira clade A exhibited the highest abundance (3.00 × 104 ± 8782.37 copies/g), followed by comammox Nitrospira clade B (1.83 × 103 ± 1019.82 copies/g), ammonia-oxidizing bacteria (AOB) (1.28 × 103 ± 574.69 copies/g), and AOA (1.73 × 102 ± 48.05 copies/g). The abundances of both comammox clades A and B were positively correlated with sediment pH, indicating that pH is an important environmental factor affecting the growth of comammox bacteria. Additionally, the relative abundances of both comammox clade A.2 and clade B were significantly correlated with overlying water dissolved oxygen (DO) in the reservoir area. This study thus indicated that there exists a niche differentiation of comammox Nitrospira in the main stream of the Three Gorges Reservoir area. The potential changes in the ammoxidation process and the environmental effects caused by this niche differentiation need further attention.

Using ferric tannate as catalyst to drive a new anammox-like process for ammonium removal

A normative ‘nitrogen removal process’ was established through partial nitrification coupled with ammox-like process of the ferric tannate (TA-Fe). Compared with traditional ammoxidation process, TA-Fe used here was more available in practice, there is no need to deliberately adjust the process parameters to meet the growth of functional microorganisms, which made NH4+-N remove effectively and economically in a single reactor. Results indicated that the removal efficiency of NH4+-N reached 80% after adding TA-Fe. In the meantime, the NO2--N and NO3--N accumulation rate declined sharply to 2.33% and zero. Both Fourier transform infrared spectrometry (FTIR) and X-ray diffraction (XRD) results indicated that Fe2O3 and Fe3O4 existed in TA-Fe. The X-ray photoelectron spectroscopy (XPS) spectra revealed Fe(III) and Fe(II) existed on the surface of TA-Fe. High-throughput sequencing results indicated that TA-Fe had appreciable effect on microbial diversity in the biofilm reactor. Furthermore, the material species analysis further indicated that the relative abundance of the Anammox related bacteria (Candidatus Brocadia fulgida) up to 96.7% implied that the improvement of nitrogen removal was due to synergistic effect of TA-Fe and biological denitrification. Results of this project will provide scientific basis for the development of new theory of nitrogen removal from wastewater.

Continuous-Flow Ammoxidation of 2-Methylpyrazine to 2-Cyanopyrazine with High Space-Time Yield in a Microreactor.

A microreactor (MR) with a vaporization microchamber and a sinusoidal wave microchannel was fabricated to synthesize 2-cyanopyrazine (CP) directly with an aqueous 2-methylpyrazine (MP) solution. A continuous-flow process with high space-time yield was achieved under the premise of strong exothermality of this ammoxidation reaction. The vanadium metal oxide catalysts with four different supports (α-Al2O3, γ-Al2O3, ZSM-5(50), ZSM-5(80)) were evaluated by simply stacking in the wave microchannel from 350 to 540 °C. The process parameters (temperature, reactant ratio, and size of catalysts) were optimized with the selected CrVPO/γ-Al2O3 catalyst, and an optimal ammoxidation process with MP conversion (XMP) of 71.5% and CP selectivity (SCP) of 93.7% was obtained by a volume space velocity (GHSV) of 13 081 h–1 at 480 °C. Correspondingly, the space-time yield of CP (STYCP) was 1724–77 082 gCPkgcat–1h–1, which was the highest value ever reported for this reaction. Meanwhile, the ammoxidation reaction showed a great continuous-synthesis stability of 50-h running in the microreactor with the CP yield (YCP) remaining 56%–68%.

Ozonation with ammoxidation as a method of obtaining O, N-doped carbon electrode material to electrochemical capacitors

This paper discusses the electroactivity of carbon materials doped by heteroatoms. Activated carbons were modified by the reaction with an ammonia solution followed by ozone treatment. Ozone treatment allows the introduction of not only oxygen functionalities but also nitrogen functional groups through the ammoxidation process. The modified and unmodified carbon materials were used as electrode materials of an electrochemical capacitor. To determine the processes occurring at the electrode/electrolyte interface, a broad physicochemical and electrochemical analysis was performed. The electrical characteristic of supercapacitors was measured in two- and three-electrode cells assembled in a Swagelok® system in aqueous electrolytes. The electrochemical properties were examined by cyclic voltammetry and electrochemical impedance spectroscopy.

Improvement of fish production and water quality in a recirculating aquaculture pond enhanced with bacteria-microalgae association

Intensive aquaculture plays an essential role in meeting human beings' growing demand for aquatic products. Recirculating pond has been considered as an effective approach for water and energy saving, but its wastewater also causes severely impair to aquatic animal health in some extent due to residual noxious nitrogen compounds (such as ammonia and nitrite) which are derived from mineralisation and break-up of uneaten feed and fish faeces. In order to purify water efficiently, biological processes are combined with recirculating pond such as using biological filtration, adding probiotics and so on. In this study, a field experiment was conducted to evaluate the potential of a closed recirculating aquaculture pond enhanced with bacteria-microalgae association in improving fish production and water quality. The results showed that the concentrations of total nitrogen (TN), total ammonia-N (TAN) and nitrite-N in the group of bacteria-microalgae with biofilm carriers were reduced by 29.15%, 51.28% and 33.48%, respectively, compared with treatment without any bioaugmentation. Meanwhile, the fish production was significantly improved (13.3%). Microbial community analysis (qPCR and high-throughput sequencing of 16 s and 18 s rRNA genes) suggested that the application of bacteria-microalgae with biofilm carries reduced the abundance of chiA gene (83.19%) which convert organic nitrogen into ammonia-N and increased the abundance of ammonia-monooxygenase (amoA) gene carried by ammonia-oxidizing bacteria (330.75%) and copper-containing nitrite reductase (nirK) gene (464.44%), indicating that the conversion of organic nitrogen to inorganic nitrogen was reduced and the denitrification process was increased. At the initial period, most of nitrogenous compounds were assimilated by microalgae. Along with the experiment, the bacteria community relative to nitrification and denitrification was also increased in bacteria-microalgae with biofilm carriers group compared with CK, such as Delftia (500%) and Acidovorax (450%) in ammoxidation process.

Simultaneous production of hydrogen and acrylonitrile in a new bifunctional micro-reactor, mathematical modeling and optimization study

In the last decade, there have been numerous investigations toward enhancing the efficiency of hydrogen production methods, as well as improving their operational variables. In this work, hydrogen and acrylonitrile are produced in a bench-scale concept by steam reforming of glycerol and ammoxidation of propane, respectively. Based on the present micro-reactor configuration, the needed heat, which is vital for the advancement of the endothermic glycerol steam reforming process in the outer tube, is supplied with the produced heat in the propane ammoxidation reactions in the inner tube. Consequently, in spite of the conventional steam reforming and ammoxidation process, the cooler and furnace are not required. As a result, appropriate energy-saving has been made, along with the reduction of the emission of hazardous greenhouse gases. Adequate improvement can be noticed in the performance of the reactor in which the glycerol conversion has improved from 53.32% to 87.11%. Also, to investigate the impact of the operating condition on the behavior of the proposed reactor configuration, a sensitivity analysis in the case of inlet flow rate, inlet feed composition, and inlet temperature is implemented. It is worth highlighting that the optimization scheme is applied in order for governing the best solution for the suggested configuration within the defined ranges. Optimization outputs established 3.97%, 1.41%, 4.93%, and 3.01% augmentation in the glycerol conversion, hydrogen yield, propane conversion, and acrylonitrile yield, respectively.

Abundance and community structure of ammonium monooxygenase (amoA) genes in the wet season of liaohe estuary sediments

Ammonia oxidation is an important part of the global nitrogen cycle. Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) are important players in the ammoxidation process. In this study, 13 sediment samples from the Liaohe estuary were collected in the wet season. The abundances of 16S rRNA and amoA genes were detected by real-time fluorescence quantitative PCR. The diversity and community structure of AOA and AOB were investigated by constructing clone libraries. The AOA and AOB amoA gene abundances ranged from 3.10 × 106–2.85 × 107 and 6.59 × 105–1.20 × 107 copies/g wet deposit, respectively. At all sites, AOA abundance was greater than AOB (AOA: AOB = 2.2–86.5). The ratio of AOA: archaeal 16S rRNA gene abundances and AOB: bacterial 16S rRNA gene abundances were 4.6 × 10−3–1.5 × 10−2 and 1.5 × 10−6–1.0 × 10−4. Phylogenetic analysis showed that the AOA amoA sequences were mainly Nitrosophaera and Nitrosopumilus, and most of the AOB amoA sequences belong to unclassified bacteria, which mainly were detected in estuarine sediments and wetland soils. AOA and AOB community had an obvious spatial heterogeneity. In addition, canonical correspondence analysis showed that the salinity, ammonia, total phosphorus, total organic carbon, sand, and silt content were the main driven factors of AOA and AOB community structure, in which the sand and silt content had a significant contribution.

Emergency shutdown of fluidized bed reaction systems

With several industrial applications of fluidized bed technology recently commercialized worldwide, it becomes essential to develop safe operation methods for fluidized bed reaction systems (FBRSs) to prevent any influence on their process values, which lead to accidents. To preventing any disaster or malfunction in an FBRS, an emergency shutdown system (ESD) is initiated, closing the reaction system in case of any abnormality by effectively isolating the flammable gas. However, an ESD is also prone to the “inactivation problem,” in which in the case of failure it initiates the emergency shutdown, even when the operating conditions of the reaction system are abnormal. It is also vulnerable to a “malfunction problem,” where the emergency shutdown is performed even when the operating conditions of the reaction system are normal. In this study, these problems were solved by investigating a reaction system through the monitoring of appropriate parameters and setting up of trigger levels, which reflect the uniqueness of an FBRS using an ESD. The parameters were identified by analyzing the scenario leading to an accident. The trigger levels were determined as the points at which the loss is smaller in the presence of an ESD, as compared to the value of the loss function in the presence or absence of an ESD. Furthermore, the ESD design model was applied as a case study in the ammoxidation process of propylene. The results showed that an ESD can prevent an approximately 8 billion yen of loss due to accidents in plant operations, against an investment of 200 million yen.

A conceptual comparison between potential configurations in the thermal coupling of naphtha reforming with propane ammoxidation

Abstract In order to achieve a proper temperature profile and consequently a higher production rate, the conventional catalytic naphtha reforming process (CNR) was coupled thermally with the propane ammoxidation process as a heat source through a novel bifunctional reactor. Propane ammoxidation is a highly exothermic process that occurs on the reactor tube side to supply the required heat for naphtha reforming reactions on the shell side. In this study, the performance of the novel reactor with different types of feeding has been investigated. Two possible counter-current configurations of Series-Naphtha-Parallel-Ammoxidation (SNPA) and Parallel-Naphtha-Parallel-Ammoxidation (PNPA) have been compared with four possible co-current configurations of SNPA, PNPA, Series-Naphtha-Series-Ammoxidation (SNSA), and Parallel-Naphtha-Series-Ammoxidation (PNSA). Among the co-currents, PNPA showed the highest production. The counter series feeding of propane ammoxidation (SNSA and PNSA) was not possible due to the exothermic side's temperature runaway. The results showed that the counter-current SNPA arrangement significantly boosts the heat transfer between the endothermic and the exothermic sides, improving the product yields more than other arrangements and CNR. For counter-current SNPA 42% yield of aromatics was achieved, which is 5% and 7% more than the co-current PNPA and CNR, respectively. In addition, co-current and counter-current configurations were investigated in terms of temperature uniformity. The best configurations in co-current and counter-current were co-SNSA and count-SNPA, respectively. Also, optimization of counter-current SNPA was examined and its results compared with non-optimized results. It was observed that in optimized reactors, the yield of aromatics and the overall yield of acrylonitrile (ACN) were increased to 45% and 41%, respectively.

Technical and economic analysis of acrylonitrile production from polypropylene

In this research, we investigate the propylene ammoxidation process, which is under the license of Sohio Company, as well as its supply and demand, production method, and economical analysis of acrylonitrile production process. Acrylonitrile is a key material in textile, plastic, and packaging industries as well as automobile manufacturing. This research studies the economic aspects of its production process. Over time, the need for this product has become more sensible due to the enhancement of production and autarky. We do not have any acrylonitrile production unit in Iran at this time. Some acrylonitrile process simulations and its economic analysis have been carried out with HYSYS and Icarus software, respectively, then we compared the results with those obtained from COMFAR software in the Persian Gulf Petrochemical Holding. Results indicated that this process is economically feasible only in large scale production. It is very important to take precautions since hazardous precursors are used in this process. Hydrogen cyanate is an extremely hazardous material that is produced as a by-product in this process. There is not any solution for disposal or any usage for this byproduct in Iran. Results obtained from Icarus software were more precious and promising compared to desk calculations. Comparison of these two production units, with different production capacities, has indicated that reduction in production rate of return was lower in the large unit and it is better to establish a smaller unit for acrylonitrile production.

Interaction between 17β-estradiol degradation and nitrification in mariculture wastewater by Nitrosomonas europaea and MBBR

This study investigated the relation between 17β-estradiol (E2) degradation and nitrification in synthetic mariculture wastewater by ammonia oxidizing bacterium Nitrosomonas europaea and moving bed biofilm reactor (MBBR). Batch experiments showed that E2 degradation by N. europaea in wastewater followed zero-order reaction kinetics (r2 = 0.944, 4.07 μg/ L h−1) when ammonia presented. Nitrite yield in N. europaea inoculation decreased by 77.8% exposed to 1 mg/L E2. The inhibitory impact on ammonia oxidation was enhanced with increasing E2 dosage from 50 ng/L to 1 mg/L. Notably, E2 as low as 50 ng/L still had significant interference with nitrite production, bacterial density and ammonia monooxygenase (AMO) activity of N. europaea. Still, the following continuous 68-day degradation test revealed that 84.5%–98.7% E2 could be removed by a bench-scale MBBR. Whereas, ammonia removal remarkably decreased from 94.7% ± 2.1% to 85.6% ± 2.1% (p < .05) along with the enhanced E2 removal (from 84.5% ± 2.0% to 98.7% ± 0.4%, p < .05) when inlet E2 increased from 10 μg/L to 1 mg/L, indicating the great role of heterotrophs in E2 degradation. In contrast, nitrite oxidation was not affected upon E2 exposure irrespective of E2 concentrations. In summary, nitrification was effective in removing E2, while E2 interfered with ammoxidation process, but this interference was negligible at the reactor level given the low level of E2 in practical field conditions.

Hybrid Separation Scheme for Azeotropic Mixtures –Sustainable Design Methodology

Distillation has been the first choice among the numerous separation techniques employed by chemical industries, primarily because of its inherent advantages. About 80% of industrial separations involving vapour – liquid phases are performed by distillation, in spite of its low thermal efficiency and highly energy intensive nature. More than 50 % of the total energy consumed in distillation, is spent for enriching the product purity from 80-90% to close to 100 %. However, a conventional distillation process operating at normal conditions is ineffective for separating azeotropic mixtures. In this work, a methodology has been proposed to explore the possibility of integrating distillation with membrane separation technique to separate azeotropic mixtures. These units will be operated at their maximum driving force for separation in the proposed hybrid schemes. The designed optimal hybrid schemes result in energy efficient separations compared to conventional distillation processes. The effectiveness of the proposed methodology is demonstrated with the help of two case studies. In the first case study, a well-known example of benzene - cyclohexane separation is presented, while production of 99.9 mole % pure acetonitrile from an ethanol ammoxidation process is discussed in the second case study. Both these systems form azeotropes at atmospheric pressure.

Ammoxidation of polyethylene: A new route to carbon

Carbon fibers boast excellent mechanical properties, but widespread adoption into everyday composite materials is limited by their high cost. Polyethylene seems like an ideal low-cost precursor based on its high carbon content, low cost, and melt-processability, but as a saturated hydrocarbon it is functionally far removed from the graphitic structure. Here, we report that after crosslinking, the oxidation of polyethylene can be performed in a controlled manner to provide significant yields of oxidized black solid that resembles its original shape and can be subsequently heated under inert atmosphere to yield a carbonaceous solid in 10–30% carbon yield. When oxidation is conducted in the presence of ammonia, nascent carboxylic acids en route to CO2 evolution are intercepted to provide up to 70% carbon yield. This ammoxidation process was characterized by solid-state nuclear magnetic resonance, infrared spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy to contain various nitrogen containing functional groups, including amides, lactams, imides, and pyridines. The resulting carbonaceous structures were characterized by Raman spectroscopy, elemental analysis, high resolution transmission electron microscope and selected area electron diffraction to be consistent with a highly disordered wavy lattice carbon structure.

Valorization of coffee grounds to biochar-derived adsorbents for CO2 adsorption

Global warming is mainly caused by the continuous increase of CO2 concentration from the enormous utilization of fossil fuels in the environment. To circumvent this problem, it is crucial to develop an efficient and economic method to capture CO2 from large stationary sources, such as coal-fired power plants, cement, steel factories, and so on. In this study, the CO2 adsorbents are prepared with biomass wastes (coffee grounds) by combining ammoxidation process (via three different methods) and potassium hydroxide activation. Various spectroscopic and analytical techniques, such as high resolution scanning electron microscope, nitrogen adsorption-desorption isotherms, elemental analysis, Fourier-transformed infrared spectroscopy and X-ray photoelectron spectroscopy are used to study the physicochemical properties of various adsorbents. Carbon dioxide adsorption capacities of prepared adsorbents are measured by using a thermogravimetric analyzer at atmospheric pressure. Furthermore, we test the stability and selectivity of adsorbents by measuring ten CO2 adsorption-desorption cycles and selectivity of CO2 and N2. Results obtained from this study reveal that the adsorbents which are nitrogen-doped by melamine from ammoxidation treatments, followed by potassium hydroxide chemical activation, have highly developed microporosity, high amounts of N-doping and more pyrrolic nitrogen (active adsorption sites), resulting in the highest CO2 uptake of 2.67 mmol CO2 g−1sorbent at 35 °C. Most importantly, these biochar-derived adsorbents have excellent selectivity ([CO2/N2] = 74.2) for CO2N2 separation and good cyclic stability of CO2 adsorption-desorption process, which may be suitable for practical applications in capturing CO2 emitted from coal-fired power plant.