Production Of Caprolactam Research Articles

Energy-efficient eco-friendly marine waste treatment: Recovery of caprolactam from fishing net waste using seashell-derived catalyst

Fishing net waste (FNW) is marine waste having significantly negative effects on the marine environment and ultimately human health. Herein, we endeavored to use a catalyst made from seashells for the recovery of caprolactam (CPL) from FNW (made of polyamide 6; free of any other materials like floats, lead lines, and sand) via a catalytic pyrolysis under CO2 atmosphere. The catalytic pyrolysis of FNW in CO2 over the seashell-derived catalyst yielded 77.7 wt% CPL at 500 °C. It was simulated on a large-scale based on data from laboratory-scale experiments, and energy analysis and life-cycle assessment (LCA) were carried out. The proposed integrated process consists of three steps: FNW-to-CPL conversion via catalytic pyrolysis, CPL recovery, and heat and power production. An effective separation process consisting of in series of flash and distillation columns was designed by considering the characteristics of resulting mixture, and the overall process allows the production of CPL from FNW with a high yield (74.3%). This value is only 3.4% point lower than the experimental yield of CPL (77.7%), and the energy requirements (0.21 MW heating energy) are met internally. The results of the LCA suggest that the proposed strategy can help solve the problem of marine pollution from debris such as FNW.

Industrial Process and Modern Technical Adaptations for Nylon 6 Monomer Caprolactam: A Mini Review

Caprolactam is in high demand in the new materials industry as a monomer for nylon and polyamides. Although the schemes of traditional processes such as hydroxylamine production (hydroxylamine sulphate oxime process, hydroxylamine phosphate oxime process, nitric oxide reduction process) and cyclohexanone production were still involved in the caprolactam production industry, the modern technical adaptations achieved higher atomic utilisation and higher selectivity. In this review, the basic traditional schemes for the production of caprolactam are for the first time presented. The modern technical adaptation, the rectification dehydrogenation of the by-product cyclohexane in cyclohexanone production, was highlighted to achieve an increase in atomic utilisation from 78 % to 98 %. The higher selectivity achieved with membrane separation resulted in a conversion of cyclohexanone of > 99.6 % and a selectivity of cyclohexanone oxime of > 99.5 %. In addition, the progress of the catalysts used in the modern technical adaptation was briefly discussed. This review highlights the modern process with atom economy and high selectivity.

Kwas benzoesowy Metoda oznaczania w powietrzu na stanowiskach pracy

Benzoic acid is an organic compound that belongs to the group of aromatic carboxylic acids. It is mainly used in the production of phenol, caprolactam and benzoic salts, as a food and pharmaceutical preservative, and in the production of herbicides, insecticides and bactericides. According to the Regulation of the European Parliament and of the Council (WE 1272/2008), benzoic acid is classified as a substance that is harmful to the lungs, irritates the skin and causes eye damage. The aim of the study was to develop a method for the determination of benzoic acid for the assessment of occupational exposure within 1/10–2 of the proposed MAC value. The method involves taking the inhalable fraction of airborne benzoic acid onto a glass fiber filter coated with sodium carbonate(IV), desorption with a solution of methanol in water and then determining the benzoic acid content of the sample by the use of liquid chromatography with diode array detector (UHPLC-DAD). Validation requirements presented in European standard PN-EN 482 were fulfilled during the tests. The method enables determination of benzoic acid in air at concentrations of 0.05 to 1 mg/m3 . The method for determining benzoic acid has been recorded in the form of an analytical procedure (see Appendix). This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.

THE SCIENTIFIC BASIS OF INDUSTRIAL APPLICATION OF THE PROCESS OF SELECTIVE HYDROGENATION OF BENZENE IN DIFFERENT CATALYTIC SYSTEMS

Pollution of the environment with substances obtained in the production of oil and other products in various industries forces us to take measures to solve environmental problems that have become relevant in recent years. Arenes, belonging to the class of petroleum-derived aromatic hydrocarbons, are very life-threatening substances due to their carcinogenic effects. In this regard, one of the important issues is the release of benzene, a special representative of arenes, from its carcinogenic effect as a toxic and volatile compound, and its use in the production of cyclohexane, which is the main raw material for the production of caprolactam and nylon. The selectivity of the hydrogenation of benzene and the high yield of cyclohexane, the target product, depend on the reaction conditions and the choice of catalysts. In recent years, the application of polymer and zeolite nanocomposite catalysts, as well as modified metal polymer-based catalysts, in obtaining highly active and selective catalysts for the purpose of effective implementation of aromatic hydrocarbon hydrogenation processes is of great interest. Thus, naphthenic hydrocarbons are considered the main starting materials for the synthesis of various classes of compounds. Derivatives of these compounds are used in the pharmaceutical industry as special-purpose caprolactam, adipic acid, cyclohexanone, as a solvent for essential oils, varnishes, paints, as an extractant, etc. are used in synthesis. As a result of investigating the catalytic properties of polymer-mineral catalysts in the benzene hydrogenation reaction, it was determined that these reactions show selectivity in the direction of cyclohexane formation in narrow-pore zeolites (mordenite, clinoptilolite)In the presented work, the main information was collected by analyzing the literature on the work carried out in this direction

Electrocatalytic Synthesis of Nylon‐6 Precursor at Almost 100 % Yield

AbstractSynthesis of cyclohexanone oxime via the cyclohexanone‐hydroxylamine process is widespread in the caprolactam industry, which is an upstream industry for nylon‐6 production. However, there are two shortcomings in this process, harsh reaction conditions and the potential danger posed by explosive hydroxylamine. In this study, we presented a direct electrosynthesis of cyclohexanone oxime using nitrogen oxides and cyclohexanone, which eliminated the usage of hydroxylamine and demonstrated a green production of caprolactam. With the Fe electrocatalysts, a production rate of 55.9 g h−1 gcat−1 can be achieved in a flow cell with almost 100 % yield of cyclohexanone oxime. The high efficiency was attributed to their ability of accumulating adsorbed hydroxylamine and cyclohexanone. This study provides a theoretical basis for electrocatalyst design for C−N coupling reactions and illuminates the tantalizing possibility to upgrade the caprolactam industry towards safety and sustainability.

Electrocatalytic synthesis of nylon-6 precursor at almost 100% yield.

The application of the cyclohexanone-hydroxylamine process using preformed hydroxylamine is widespread in the caprolactam industry, a crucial step to produce nylon-6. However, with strict demands on sustainability and safety, two shortcomings in this process-harsh reaction conditions and the potential danger posed by explosive hydroxylamine-need to be urgently overcome. In this study, we presented a direct electrosynthesis method for cyclohexanone oxime using nitrogen oxides and cyclohexanone with almost 100% yield, which eliminated preformed hydroxylamine and demonstrated a simple strategy for green production of caprolactam. Combining theoretical calculations and in situ characterizations, the high efficiency of electrocatalysts is attributed to their ability to accumulate adsorbed hydroxylamine and cyclohexanone. Fe electrocatalysts can meet the above requirements and achieve a production rate of 55.9 g h-1 gcat-1 in a flow cell with almost 100% yield of cyclohexanone oxime. Beckmann rearrangement of the resulting cyclohexanone oxime produced 8.6 g/cycle of caprolactam. This study not only provides a theoretical basis for electrocatalyst design for C-N coupling reactions but also illuminates the tantalizing possibility to upgrade the caprolactam industry toward safety and sustainability through direct electrosynthesis of cyclohexanone oximes.

Epsilon-Caprolactam- and Nylon Oligomer-Degrading Bacterium Brevibacterium epidermidis BS3: Characterization and Potential Use in Bioremediation.

epsilon-Caprolactam (Caprolactam, CAP), a monomer of the synthetic non-degradable polymer nylon-6, is the major wastewater component in the production of caprolactam and nylon-6. Biological treatment of CAP, using microbes could be a potent alternative to the current waste utilization techniques. This work focuses on the characterization and potential use of caprolactam-degrading bacterial strain BS3 isolated from soils polluted by CAP production wastes. The strain was identified as Brevibacterium epidermidis based on the studies of its morphological, physiological, and biochemical properties and 16S rRNA gene sequence analysis. This study is the first to report the ability of Brevibacterium to utilize CAP. Strain BS3 is an alcalo- and halotolerant organism, that grows within a broad range of CAP concentrations, from 0.5 up to 22.0 g/L, optimally at 1.0-2.0 g/L. A caprolactam biodegradation experiment using gas chromatography showed BS3 to degrade 1.0 g/L CAP over 160 h. In contrast to earlier characterized narrow-specific CAP-degrading bacteria, strain BS3 is also capable of utilizing linear nylon oligomers (oligomers of 6-aminohexanoic acid), CAP polymerization by-products, as sole sources of carbon and energy. The broad range of utilized toxic pollutants, the tolerance for high CAP concentrations, as well as the physiological properties of B. epidermidis BS3, determine the prospects of its use for the biological cleanup of CAP and nylon-6 production wastes that contain CAP, 6-aminohexanoic acid, and low molecular weight oligomer fractions.

Dynamics of Pressure Variation in Closed Vessel Explosions of Diluted Fuel/Oxidant Mixtures

Nitrous oxide is widely used as oxidizer or nitriding agent in numerous industrial activities such as production of adipic acid and caprolactam and even for production of some semiconductors. Further, it is used as an additive in order to increase the power output of engines, and as an oxidizer in propulsion systems of rockets, because it has a large heat of formation (+81.6 kJ mol−1). N2O is highly exothermic, and during its decomposition a supplementary heat amount is released, so it needs special handling conditions. The combustion of fuels in nitrous oxide atmosphere can lead to high unstable and turbulent deflagrations that speedily self-accelerate and therefore a deflagration can change to a detonation. The peak explosion pressure and the maximum rate of pressure rise of explosions in confined spaces are key safety parameters to evaluate the hazard of processes running in closed vessels and for design of enclosures able to withstand explosions or of their vents used as relief devices. The present study reports some major explosion parameters such as the maximum (peak) explosion pressures pmax, explosion times θmax, maximum rates of pressure rise (dp/dt)max and severity factors KG for ethylene-nitrous oxide mixtures (lean and stoichiometric) diluted with various amounts of N2, at various initial pressures (p0 = 0.50–1.50 bar), in experiments performed in a spherical vessel centrally ignited by inductive-capacitive electric sparks. The influence of the initial pressure and composition on pmax, θmax and (dp/dt)max is discussed. The data are compared with similar values referring to ethylene-air mixtures measured in the same initial conditions. It was found that at identical C/O ratios with ethylene-air, ethylene-N2O-N2 mixtures develop higher explosion pressures and higher rates of pressure rise, due to the exothermic dissociation of N2O under flame conditions.

Effects of Caprolactam Wastewater on Algal Growth and Nutrients Removal by Arthrospira platensis

Caprolactam wastewater (WCP), which is generated during the production of caprolactam, contains high contents of NO3− and inorganic P and is considered to be difficult to treat. In this study, Arthrospira platensis was used to remove N and P from WCP. Culture conditions and wastewater addition were optimized to relieve the inhibition effects of WCP. The results show that A. platensis growth and photosynthetic activity were inhibited depending on WCP concentrations. The inhibition rates were enhanced as the culture time increased under batch mode. However, the fed-batch mode significantly minimized the negative impact on A. platensis, which is beneficial for removing N and P from WCP by Arthrospira. After 10 d of cultivation of A. platensis in a 25 L circular photobioreactor in fed-batch addition of WCP (1.25% mixed WCP (v/v) each day), the average biomass productivity reached 17.48 g/(m2·d), the maximum protein content was 69.93%, and the N and P removal ratios were 100%. The accumulation effect of WCP inhibition on algal growth was not observed under this culture condition. Fed-batch cultivation of A. platensis is a promising way for bioremediation of WCP with high N and P removal efficiencies and high value-added biomass production.

Features of The Processes of Clinker Formation When Using Solid Waste From Caprolactic Production As A Mineralizer

The possibility of using a soda-sulfate mixture - an alkaline waste from the production of caprolactam, as a mineralizing additive in a Portland cement raw mixture containing, as a silica-containing component, flotation tailings of the lead-concentrating plant of Almalyk MMC, has been studied. The effect of this additive on the processes of mineral formation during the synthesis of Portland cement clinker is shown. The possibility of additional recovery of residual non-ferrous metals - lead and copper - by sublimation and trapping of their chlorides has been established.

Upcycling of waste teabags via catalytic pyrolysis in carbon dioxide over HZSM-11

Disruptive impact of everyday waste on the environment makes it a serious growing concern. Even though disposal and reclaim strategies are firstly considered to overcome this problem, upcycling of the waste via thermochemical transformations (e.g., pyrolysis) will eventually be essential to reconvert massive quantities of waste materials. Here, to seek a method to valorize everyday waste, the effects of CO2 and HZSM-11 catalyst on pyrolytic products produced via pyrolysis of waste teabag were investigated. For non-catalytic pyrolysis of waste teabag, CO2 increased the yield of pyrolytic gases and suppressed the formation of benzenes, phenolics, and polycyclic aromatic hydrocarbons, compared to N2. For catalytic pyrolysis of waste teabag over HZSM-11 more CO2 was transformed to CO than non-catalytic pyrolysis. The extent of CO2 conversion into CO was greater in CO2 environment than in N2 environment. A synergistical use of CO2 and HZSM-11 in pyrolysis of waste teabag enhanced the production of caprolactam (6.8 wt% yield), a value-added nylon monomer. The char derived from waste teabag via the pyrolysis in CO2 over HZSM-11 had higher heating value of 26 MJ kg−1 comparable to HHV of coal. The synergistical employment of HZSM-11 catalyst and CO2 pyrolysis medium has a significant feature of upcycling everyday waste such as waste teabag.

Identification, Characterization, and Application of a Highly Sensitive Lactam Biosensor from Pseudomonas putida.

Caprolactam is an important polymer precursor to nylon traditionally derived from petroleum and produced on a scale of 5 million tons per year. Current biological pathways for the production of caprolactam are inefficient with titers not exceeding 2 mg/L, necessitating novel pathways for its production. As development of novel metabolic routes often require thousands of designs and result in low product titers, a highly sensitive biosensor for the final product has the potential to rapidly speed up development times. Here we report a highly sensitive biosensor for valerolactam and caprolactam from Pseudomonas putida KT2440 which is >1000× more sensitive to an exogenous ligand than previously reported sensors. Manipulating the expression of the sensor oplR (PP_3516) substantially altered the sensing parameters, with various vectors showing Kd values ranging from 700 nM (79.1 μg/L) to 1.2 mM (135.6 mg/L). Our most sensitive construct was able to detect in vivo production of caprolactam above background at ∼6 μg/L. The high sensitivity and range of OplR is a powerful tool toward the development of novel routes to the biological synthesis of caprolactam.

Thermal Analysis of Waste Fishing Nets for Polymer Recovery

Waste fishing gear is a major source of water pollution that causes serious environmental problems. As an example, nets and ropes are produced using different polymers, which are exposed to mechanical stress, oxygen, salt water, ultraviolet radiation, etc. Moreover, their polymeric chains decompose and are eroded releasing various chemical species. Due to these reasons they must be properly disposed of. In this work, there was analysed the decomposition process of substances and characterised the produced chemical compounds. Thermal analysis has demonstrated that the largest part of material is decomposed to volatile monomers within the range of 400–440 °C at different heating rates of 5, 15, 20 and 30 °C/min. Based on ATR-FTIR results, the main polymer of fishing nets was found to be Nylon 6. In addition, spectroscopic FTIR 3D analysis of gases confirmed that decomposition of Nylon 6 corresponds to the spectrum of caprolactam during the most intense decomposition. Evolved gas analysis of waste fishing nets showed that pyrolysis of Nylon 6 results in the reduction of the material into monomers, and indicates significant potential for the use of the material and process in the production of caprolactam. This study proposes an innovative waste recycling technique enabling to reduce the volume of waste dumped into landfills.

An overview of caprolactam synthesis

ABSTRACTCaprolactam is the precursor of many industrial chemical productions as in nylon industry, plastic industry, paint industry, lysine synthesis and cross-linking for polyurethanes. The production of caprolactam has been focus much from last three decades among the scientific community to fulfill the industrial need under environment precautions. Herein a sequential and explanatory review broadly covering the transformation of a different substrate as cyclohexanone oxime, cyclohexanone, cyclohexanol, cyclohexane, and biorenewable sources into caprolactam is presented. For every substrate, a wide range of catalyst including homogeneous as well as the heterogeneous system has been deeply considered. This study will be helpful for developing alternative industrial route for production of caprolactam.

Artificial Caprolactam-Specific Riboswitch as an Intracellular Metabolite Sensor.

Caprolactam is a monomer used for the synthesis of nylon-6, and a recombinant microbial strain for biobased production of nylon-6 was recently developed. An intracellular biosensor for caprolactam can facilitate high-throughput metabolic engineering of recombinant microbial strains. Because of the mixed production of caprolactam and valerolactam in the recombinant strain, a caprolactam biosensor should be highly specific for caprolactam. However, a highly specific caprolactam sensor has not been reported. Here, we developed an artificial riboswitch that specifically responds to caprolactam. This riboswitch was prepared using a coupled in vitro- in vivo selection strategy with a heterogeneous pool of RNA aptamers obtained from in vitro selection to construct a riboswitch library used in in vivo selection. The caprolactam riboswitch successfully discriminated caprolactam from valerolactam. Moreover, the riboswitch was activated by 3.36-fold in the presence of 50 mM caprolactam. This riboswitch enabled caprolactam-dependent control of cell growth, which will be useful for improving caprolactam production and is a valuable tool for metabolic engineering.

Catalytic Condensation of Carbonyl Compounds during the Synthesis of Cyclohexanone in the Production of Caprolactam

Kinetic features of the condensation processes of carbonyl and unsaturated impurities in cyclohexanone have been studied using model mixtures in a heterophase system in the presence and absence of phase-transfer catalysts. It has been shown that linear aldehydes are condensed with cyclohexanone in the heterophase system in the presence and absence of phase-transfer catalysts under mild conditions (30–50°C). Noncarbonyl unsaturated compounds (e.g., 2-cyclohexene-1-ol) can be removed only at temperatures above 100°C in the presence of acidic catalysts (e.g., high-temperature sulfonated cation-exchange resins). Unsaturated cyclic ketones are characterized by both alkylation reactions over acid catalysts and aldol condensation reactions in the presence of an alkali, thereby suggesting the possibility of their elimination at different cyclohexanone purification steps. The theoretical models built can be used to develop an effective cyclohexanone purification technology that will substantially enhance the manufacturability of high-purity caprolactam and polyamide.

Liquid-phase oxidation of cyclohexane. Elementary steps in the developed process, reactivity, catalysis, and problems of conversion and selectivity

The literature data concerning features of the kinetics and mechanisms of elementary steps of liquid-phase oxidation of cyclohexane and its oxygen derivatives are considered and analyzed. A comparison of rates of intermolecular and intramolecular reactions of cyclohexylperoxyl radicals under the industrial conditions indicated a necessity to take into account intramolecular interactions. The occurrence of cross recombination of hydroperoxyl and α-hydroxyperoxyl radicals without chain termination in the course of cyclohexanol and 2-hydroxycyclohexanol oxidation was proved. A significance of degenerate branching reactions involving cyclohexyl hydroperoxide in the industrial process of cyclohexane oxidation at 423 K was evaluated. The influence of the electron-withdrawing functional groups on the reactivity of carbon–hydrogen bonds of organic compounds in the reactions with electrophilic peroxyl radicals was studied. The low conversion of a substrate in the industrial process are mainly caused by the radicalchain oxidation of cyclohexanone leading only to by-products. The catalysts of cyclohexane oxidation, viz., compounds of variable valence metals, affect the reaction rate and ratio of the yields of the target products (cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone) but exert no effect on their relative reactivity. The use of the catalytic additives increasing the yield of cyclohexanone in the step of cyclohexane oxidation in the production of caprolactam is revealed to be inexpedient.

Cyclohexanone ammoximation over TS-1 catalyst without organic solvent in a microreaction system

We herein propose a highly efficient technology for the synthesis of cyclohexanone oxime, a key intermediate for the production of caprolactam. The classical cyclohexanone ammoximation over TS-1 catalyst needs t-butanol as the organic solvent to change the reaction system from liquid-liquid-solid to liquid-solid for much better reaction performances, which greatly increases the reactor size and the downstream separation cost. In this work, a solvent-free liquid-liquid-solid heterogeneous reaction was successfully implemented in a microreaction system containing two T-junction microreactors. The effects of temperature, pressure, residence time, concentrations of reactants and catalyst on the reaction performance were systematically investigated. This developed technology resulted in a 99.87% conversion of cyclohexanone and nearly 100% selectivity to cyclohexanone oxime within 3 min. These results indicate that the new process could provide a more environmental friendly and economic approach to caprolactam industry.

Electrochemical Reduction of Greenhouse Gas with Couette-Taylor Flow (CTF) Mixer

N2O, a greenhouse gas like CO2 or CH4, has 268 times greater global warming potential (GWP) than CO2. Even though the volumetric portion of N2O among the greenhouse gases is merely 6%, the potential of N2O to exert a greenhouse effect is equivalent to 3 billion ton of CO2, which is similar to 50% of total car emissions worldwide. In addition, N2O plays a significant role in depleting ozone layer. The concentration of such N2O has been increasing, due to manufacturing, transportation, and agricultural activities [1]. Various chemical methods such as a thermal decomposition, a high/medium temperature catalytic decomposition, and a selective catalytic reduction have been adopted in order to reduce N2O [2]. They have been applied to industrial fields: massive production of nitric acid, adipic acid, and caprolactam because wasted heat could be used to elevate temperature up to a point, whereupon thermal decomposition of N2O takes place. However, such high-temperature methods are inadequate for reduction of N2O, which is typically emitted from room-temperature process, such as biological or medical process. Furthermore, given that the high-temperature methods require an enormous amount of energy, the successful electrochemical reduction of N2O at room temperature with a simple apparatus could be an effective alternative. Although N2O is very stable in the atmosphere, it could be electrochemically reduced into N2 in an aqueous electrolyte solution [3]. The rate of electrochemical N2O reduction could be enhanced by adopting adequate catalysts and gas-dissolution system. In this study, Couette-Taylor flow (CTF) mixer with electrochemical system was developed for effective N2O reduction. It consists of a stationary outer cylinder and a rotating inner cylinder, which are working and counter electrodes used for an electrochemical reaction. The gas injected into the solution present between two cylinders could form micro bubbles with great gas pressure and gas-liquid interfacial area than bulk gas due to the Taylor vortices in the CTF mixer [4]. The application of the CTF mixer resulted in the enhanced N2O solubility and rapid dissolution. Based on the improved N2O dissolution, high N2O conversion over 90% was obtained. In this presentation, we will focus on the optimization of operating condition of CTF mixer such as catalyst, rotational speed of inner cylinder, gas flow rate, and liquid circulation rate for efficient N2O reduction. The optimized system was also applicable to electrochemical reduction of CO2 not only N2O.

Metabolic engineering of Escherichia coli for the production of four-, five- and six-carbon lactams

Microbial production of chemicals and materials from renewable sources is becoming increasingly important for sustainable chemical industry. Here, we report construction of a new and efficient platform metabolic pathway for the production of four-carbon (butyrolactam), five-carbon (valerolactam) and six-carbon (caprolactam) lactams. This pathway uses ω-amino acids as precursors and comprises two steps. Activation of ω-amino acids catalyzed by the Clostridium propionicum β-alanine CoA transferase (Act) followed by spontaneous cyclization. The pathway operation was validated both in vitro and in vivo. Three metabolically engineered Escherichia coli strains were developed by introducing the newly constructed metabolic pathway followed by systems-level optimization, which resulted in the production of butyrolactam, valerolactam and caprolactam from renewable carbon source. In particular, fed-batch fermentation of the final engineered E. coli strain produced 54.14g/L of butyrolactam in a glucose minimal medium. These results demonstrate the high efficiency of the novel lactam pathway developed in this study.