Non-toxic Gas Research Articles

Starch as a Sustainable Fuel for Solution Combustion Synthesis: Nanomaterials for Energy and Environmental Applications

Background: Currently, solution combustion synthesis (SCS) is considered a reproducible, flexible, and low-cost synthesis method for the preparation of nanomaterials. A new trend in the SCS method is the use of less polluting fuels, such as starch. The use of starch as fuel in SCS is very interesting for green chemistry, as it is renewable and has several advantages, including its abundance, low-cost, and non-toxicity. Objective: This paper provides a comprehensive review of the SCS method using starch as fuel. The main advantages of using starch as fuel will be illustrated with a wide variety of examples, highlighting its impact on the preparation of nanomaterials for energy and environmental applications. Conclusion: In a combustion reaction using starch as fuel, several positive effects are expected, such as non-violent propagation, combustion with the production of non-toxic gases (mainly CO2 and H2O), and development of pores during the release of gases. For example, several macroporous metal oxide foams were prepared using the SCS method, through an appropriate combination of urea and starch fuels. With this approach, it is possible to control the structure, lattice defects, crystallite size, specific surface area, porosity, and other characteristics of the synthetized nanomaterial. For example, by combining starch with other fuels, it is possible to control the concentration of lattice defects in metal oxides and modify the optical properties of these materials. These properties are of fundamental importance for the performance of these materials and their subsequent application in electrodes, electrocatalysts, and photocatalysts in the areas of energy and environment.

Toxic and Non-Toxic Gas Detection System for Septic Tank

In septic tanks, various types of toxic and non-toxic gases are found such as Carbon-di-Oxide (CO2), Carbon-mono-Oxide (CO), Hydrogen Sulfide (H2S), Methane (CH4), and so on. In this paper, a toxic gas detection system for a septic tank has been presented, where MQ-135, MQ-136, MQ-4, and MQ-7 sensors are employed for combined detection of CO2, H2S, CH4, and CO gases respectively. With the change of concentration of gases, the sensor resistance changes, and accordingly an analog voltage is produced across the sensor. The analog voltages from the sensors are fed to a microcontroller, which reads the values and converts the values into gas concentration in PPM (parts per million). The PPM values for all four gases are displayed on an LCD, where two levels are assigned as “Safe” and “Danger” based on the concentration of each gas. “Safe” status means the concentration of gas is not harmful and “Danger” status means the concentration of gas is harmful. A buzzer will give an alarm when the gas concentration status becomes “Danger”. Furthermore, a Bluetooth device is interfaced with the microcontroller for transferring the gas concentration data to a smartphone. For the Smartphone, application software has been developed to monitor the concentration of each toxic gas. The prototype system has been developed and tested which gives satisfactory results. It is supposed to be a helpful and cost-effective system for cleaners working in septic tanks.

Remote Detection for the Presence of NH3, CO2, CH4, H2S, CO and Other Toxic Gases at Various Locations in a Sewer to Alert the User

Sewer gasis a complex mixture of toxic and nontoxic gases produced and collected in sewage systems by the decomposition of organic household or industrial wastes, typical components of sewage. Sewer gases may include Hydrogen Sulphide, Ammonia, Methane, Sulfur Dioxide, Carbon Monoxide and Nitrogen oxides. This project aims to deliver a system that will be useful in detecting and alerting the user before getting exposed to the toxic gases accumulated inside the sewer. This project uses MQ-135 and MQ-4 sensors to detect various toxic gases such as NH3, CO2, CH4, H2S and CO. This project also has a water level detection sensor which is used to detect the level of water and to reveal any blockage present inside the sewer. These detected gases are measured using the unit “parts per million (ppm)”. It is then compared with the threshold values that have been fed earlier inside the controller. If the detected values are higher than the threshold value, then a warning is sent to the user along with the ppm values. If the detected values are lower than the threshold value, then only the ppm values are shown to the user without any warnings. This project stores the values recorded in a dedicated webpage. This is where the information from our system is displayed to the user.

A review on gas-generants for application in exploding fire extinguisher balls

Fire is a highly exothermic reaction caused due to the rapid oxidation of a flammable substance. The mechanism of fire can be explained well with the help of a Fire Triangle comprised of the Source, Heat and Oxygen. Fire is complete and active only when all these three components are present simultaneously. There are numerous methods employed to extinguish fire, by depriving the fire of one or more of the components of the fire triangle. Recent technologies have emerged which makes use of a solid chemical mixture, placedinside a shell, which explodes when the chemical decomposes on being thrown into a fire and floodsthe fire surface with an inert gas which is a product of the decomposition. The chemical decomposes by absorbing heat from fire. Nitrogen or other non-toxic gases gets released and puts out the fire by rapidly expanding and forming a blanket around the source of fire replacing Oxygen. The light weight, portability, easy and quick deployment and the release of non-toxic by-product are the advantages of the Fire Extinguishing Shells over the conventional ones. This paper presents a review of various chemicals that can be used can potentially be used in such fire extinguishing shells.

Postsynthetically Modified Polymers of Intrinsic Microporosity (PIMs) for Capturing Toxic Gases.

Polymers of intrinsic microporosity (PIMs) are promising materials for gas adsorption because of their high surface area, processability, and tailorable backbone. Specifically, nitrile groups on the backbone of PIM-1, an archetypal PIM, can be converted to other functional groups to selectively capture targeted gas molecules. Despite these appealing features of PIMs, their potential has mainly only been realized for the separation of nontoxic gases. Here, we prepared PIM-1 materials modified with carboxylic acid and amidoxime functional groups and investigated their performance as adsorbents for the capture of ammonia (NH3) and sulfur dioxide (SO2) gases. After determining the Brønsted acidity or basicity of the PIMs from potentiometric acid-base titrations, which can be correlated with affinity for acidic or basic toxic gases, we explored the uptake capacity toward NH3 and SO2, respectively. Gas sorption studies revealed that the carboxylated PIM showed higher affinity toward NH3 through the incorporation of Brønsted acid sites, while the amidoxime functionalized PIM exhibited affinity toward SO2 through the installed of slightly basic functional groups. Overall, this study highlights new insight into PIMs as solid sorbent materials for capturing toxic gases, which can be transferred to their potential use in practical applications, such as personal protective equipment or air filtration.

A comparative study between vapor phase polymerized PPy and PEDOT - Thermoplastic polyurethane composites for ammonia sensing

In this study, in situ vapor phase polymerization (VPP) of (1) 3,4-ethylenedioxythiophene (EDOT) and (2) pyrrole (Py) on an oxidant-impregnated thermoplastic polyurethane (TPU) substrate was conducted to produce a (1) PEDOT-TPU hybrid film and (2) PPy-TPU hybrid film. Scanning electron microscopy, atomic force microscopy, and energy dispersive x-ray spectroscopy confirmed the formation of uniform, rough surfaces of PPy and PEDOT on the TPU matrix. Both PPy-TPU and PEDOT-TPU films showed excellent thermal stability across the temperature range of 300 °C–400 °C and enhanced mechanical properties, depicted by very high stress and strain values. The performance of these hybrid films to detect ammonia (NH3) gas was investigated and then optimized under the effects of varying temperature, ammonia concentration, and monomer type used. The PEDOT-TPU and PPy-TPU showed remarkable sensitivity to NH3 gas, with coefficients of variation of 0.9858 and 0.9653, respectively. Particularly, the PEDOT-TPU sensor showed higher responsiveness to NH3 at higher operating temperatures owing to its higher surface roughness and thermal stability. These flexible, stretchable, smart conducting polymer composite materials fabricated using VPP are therefore potential candidates for monitoring toxic and non-toxic gases.

Preparation and characterization of nanofibrous metal-organic frameworks as efficient catalysts for the synthesis of cyclic carbonates in solvent-free conditions.

Environmental concerns, particularly global warming, represent serious threats to public health globally. Metal-organic frameworks (MOFs) are innovative materials with prominent features such as ultrahigh surface area, high porosity and tunable cavities, which make them unique materials both in adsorption of carbon dioxide and catalysis. The design of new nanocomposites by using metal-organic frameworks as building materials has received broad attention recently. Here, nanocrystals of two unique MOF structures (UiO-66 and ZIF-67) were incorporated into electrospun polyvinyl alcohol (PVA) and polystyrene (PS) fibers (noted as MOFibers) by an ex situ method, to transform non-toxic, abundant, economical and renewable CO2 gas to cyclic carbonates in a solvent-free medium. In order to improve the composites' performance, different electrospinning parameters, including applied voltage, flow rate, collection distance, PVA and PS weight fraction in solution, and MOF weight fraction relative to the polymer, were intensively investigated. The synthesized samples were characterized by multiple techniques, such as FTIR, XRD, SEM, UV-vis and TGA, as well as N2 and CO2 adsorption measurement. It was found that all of the composites show properties combining the advantages of MOFs and polymers, such as thermal, chemical, and mechanical stability, structural flexibility, lightweight, adsorption performance and catalytic properties. Additionally, all systems were environment-friendly and the PVA/MOF fibers were easily separated and recycled for consecutive cycles.

THE ECONOMIC AND ENVIRONMENTAL BENEFIT FROM OF USING NATURAL GAS IN CARS AS AN ALTERNATIVE TO TRADITIONAL ENERGY

THE ECONOMIC AND ENVIRONMENTAL BENEFIT FROM OF USING NATURAL GAS IN CARS AS AN ALTERNATIVE TO TRADITIONAL ENERGY

Sodium Azotetrazolate: A Novel Environmental-friendly Hydrogen-free Gas-Generating Pyrotechnics

Gas-generating pyrotechnics are widely used in airbag inflator, pre-tensioner seat belt, deep-water salvage, fire extinguishing bomb, etc. However, for maintaining prolonged high-pressure, specific gas-generating pyrotechnics are required that are capable of producing water-vapor-free gaseous products to avoid the decrease of pressure caused by the condensation of water vapor. Currently, only sodium azide (NaN3)-based gas-generating pyrotechnics can meet the demand, but its application is limited due to its toxic effects. In this work, a sodium-azotetrazolate-based (STZ-based) eco-friendly and hydrogen-free gas-generating pyrotechnics was presented. A typical STZ-based gas-generating pyrotechnics was NaNO3/STZ gas-generating pyrotechnics, which could generate 321.04 L/kg clean and non-toxic gas composed of N2 and CO2 without any water vapor. The burning characteristics, including the ignition delay, maximum pressure and burning time of NaNO3/STZ gas-generating pyrotechnics was determined by conducting a closed vessel test. NaNO3/STZ gas-generating pyrotechnics showed a stable combustion process, lower ignition delay, higher burning rate, and the maximum pressure produced is 1.7 times of that of NaN3/Fe2O3. Thus, STZ exhibited great potential as gas-generating pyrotechnics, which could be applied, especially where a stable pressure is required for a long time.

Hydrogen medicine: A rising star in gas medicine

Gas medicine, including O2, NO, H2S, CO, CH4, has played important roles in prevention and treatment of diseases for a long time. Molecular hydrogen (H2), the smallest diatomic molecule in nature, has become a rising star in gas medicine in the past decades. Many studies have shown that H2 has preventive and therapeutic effects on various diseases through its selective antioxidant activity. H2, as a non-toxic gas for the human body and convenience to obtain, has provided a great possibility to be used widely. Currently, the main difficulties in hydrogen medicine are lack of definitive clinical evidence and the molecular basis of hydrogen effects. In this paper, the authors have conducted a comprehensive review and analysis of these issues, and also proposed the possibility of developing Hydrogen Biology and Hydrogen Medicine as new disciplines of biology and medicine.

Sequence structure control of CO<sub>2</sub>-based copolymer and the relationship between structure and properties

<p indent=0mm>Carbon dioxide-based (CO₂-based) copolymer is an attractive environment-friendly material with excellent biodegradability and using non-toxic, abundant and cheap carbon dioxide gas as one of its raw materials. Since CO₂ is generated as a waste gas in many economic activities leading to global warming, chemical fixation of CO₂ can be a developing and effective mean to reduce evironmental and energy pressures. Among all the CO₂-based copolymers, the aliphatic polycarbonates obtained by the copolymerization of CO₂ and epoxides are the most widely studied materials due to their excellent biocompatity, transparency as well as water and oxygen barrier properties, especially poly(propylene carbonate)(PPC). However, undesirable thermal and mechanical properties limit their practical applications. For examples, PPC has a low <italic>T</italic>_g (35–40°C) close to room temperature, which is easy to bond into blocks during long-term storage and transportation after granulation, leading to the difficulty in subsequent processing. Much efforts have been devoted to tailor the structures of CO₂-based polycarbonates to obtain desirable peoperties profile. A feasible approach is to control the configurations of synthesized polycarbonates, which can greatly improve the thermal peoperties. Another effective way is to inrtoduce a third monomer into the CO₂/epoxides copolymerization to endow copolymers with tunable properties by easily changing the monomers and controlling polymer units. Herein, this article summarizes the methods for controlling the sequence structure of CO₂-based copolymers. Four kinds of CO₂-based copolymers are included: (1) Fully alternating polycarbonates with <italic>regio</italic>- and <italic>stereo</italic>-chemistry configurations. In this part, the efforts on the stereochemistry control of polycarbonates are highlighted and the crystallinity of polycarbonates are emphatically introduced. Isotactic polycarbonates have the higher glass transition temperature than the amorphous one and some of them are crystalline. Even though no cystallinity can be observed in isotactic PPC, the <italic>T</italic>_g was 35–40°C higher than the atactic one. (2) Terpolymers prepared from the copolymerization of CO₂ with different epoxides are introduced. Since the activity of different epoxides copolymerized with CO₂ varied greatly, especially the electron-withdrawing and electron-donating epoxides, the control on the compositions and connetions of CO₂/different epoxides terpolymers is a big challenge. Highly effective metal-based catalysts were designed to sucessfully synthesize defined random terpolymers. Moreover, block polycarbonates can only be synthesized by subsequent monomer additions which requires the completely removal or consumtion of the first monomer. CO₂-besed polycarbonates with high added value are desirable today. Hence, the efforts on the post-functionalization of polycarbonates are also highlighted. (3) Terpolymers of CO₂, epoxide and cyclic anhydride. The difference in the rates of CO₂/epoxides and cyclic anhydrides/epoxides copolymerization determines the microstructure of CO₂/epoxides/cyclic anhydrides terpolymers. Therefore, copolymers with random/gradient or block structures can be easily prepared by choosing the right catalysts. Note that, some attempts to improve copolymers’ properties by introducing the crosslinked sturctures were also successful. (4) Terpolymers of CO₂, epoxide and cyclic ester. Random poly(ester-carbonate)s can be generated via one-pot/one-step strategy by using heterogenous catalysts. However, synthesis of block CO₂/epoxides/cyclic esters terpolymers usually requires multi-step operations. The good news that one-pot chemical selective polymerization of mixed monomers can be fufilled by designing the catalysts, which can tune the sequence structures of copolymers by a switch. Multiblock terpolymers are also presented. Finally, the thermal, thermal, mechanical and degradation properties of CO₂-based terpolymers are reviewed in each part to varify the relationships between structures and properties. In a summary, inserting a third monomer into the polycarbonate backbone through terpolymerization is a robust tool to tune polymers’ performances. The development directions of CO₂-based copolymers are prospected in the end.

Thermo-kinetic studies on azodicarbonamide/potassium periodate airbag gas generants

In this study, thermal characterisation of stoichiometric azodicarbonamide/potassium periodate (C2H4O2N4/KIO4) fuel/oxidizer mixtures were systematically carried out for potential application as non azide non-toxic airbag gas generants. The onset temperature of the mixture was found to be 190°C. The thermo-kinetic studies of the mixture and pure azodicarbonamide compositions at different heating rates were also carried out using Ozawa and Kissinger method and the Arrhenius parameters were computed. The activation energy of the C2H4O2N4/KIO4 mixture by Ozawa method was found to be 81.5kJ mol−1 and 78.9kJmol−1 by Kissinger method. It was found that the activation energy of the pure azodicarbonamide was higher compared to the mixture. Ballistic tank tests to obtain the pressure Vs time plots were also done and the mixture gave time response of 45.2ms and 55.54ms to peak pressure. The experimental results have shown that C2H4O2N4/KIO4 mixture can be used as a replacement to existing azide based airbag gas generant compositions. Thus, the paper attempts to thermally characterize a non-toxic C2H4O2N4/KIO4 airbag gas generant mixture which can replace toxic azide based airbag gas generants and thereby facilitate safer driving.

Direct sulfonamidation of (hetero)aromatic C-H bonds with sulfonyl azides: a novel and efficient route to N-(hetero)aryl sulfonamides.

N-Aryl sulfonamides belong to a highly important class of organosulfur compounds which are found in a number of FDA-approved drugs such as dofetilide, dronedarone, ibutilide, sotalol, sulfadiazine, sulfamethizole, vemurafenib, and many more. There is therefore continuing interest in the development of novel and convenient protocols for the preparation of these pharmaceutically important compounds. Recently, direct sulfonamidation of (hetero)aromatic C–H bonds with easily available sulfonyl azides has emerged as an attractive and powerful strategy to access N-(hetero)aryl sulfonamides where non-toxic nitrogen gas forms as the sole by-product. This review highlights recent advances and developments (2012–2020) in this fast growing research area with emphasis on the mechanistic features of the reactions.

Low-Temperature H&lt;sub&gt;2&lt;/sub&gt;S Sensors Based on Si-Coated SnO&lt;sub&gt;2&lt;/sub&gt; Nanowires

To attain high life standards, it is important to develop high-performance non-toxic gas sensors for public safety, environmental pollutant control, industrial processes, etc. Because reports on single element semiconductor-coated semiconducting metal oxides for sensing applications are rare, we synthesized SnO2 nanowires and coated them with a 5 nm-thick or 10 nm-thick Si layer for H2S gas sensing studies. SnO2 nanowires were successfully synthesized using a highly pure metallic Sn powder at high temperature in a tube furnace by the vapor-liquid-solid method and Si was deposited on the nanowires by the sputtering technique. The desired morphology and composition of the synthesized nanowires were confirmed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. Moreover, the gas sensing characteristics of pristine and Si-coated SnO2 nanowires toward H2S, CO, H2, C6H6, C2H5OH and C6H7 gases were investigated. The sensing results revealed a good response to H2S at the optimum operational temperature of 100 °C. Notably, Si-coated SnO2 nanowire sensors showed a better response to H2S than pristine SnO2 nanowires. The mechanism of H2S sensing is discussed in detail here. This study shows that the Si coating on the SnO2 nanowire enhances its sensing performance and decreases the sensing temperature required for H2S gas detection. (Received May 3, 2019; Accepted September 7, 2019)

MOLECULAR HYDROGEN: BIOLOGICAL EFFECTS, POSSIBILITIES OF APPLICATION IN HEALTH CARE. REVIEW

Hydrogen (H2) is the lightest and most common element in the universe. In molecular form, (H2) is a colorless, odorless, tasteless and non-toxic gas. For a long time, hydrogen was considered physiologically inert until its ability to reduce the intensity of the negative effect of oxidative stress was detected. According to modern concepts, oxidative stress affecting cells and tissue to be damaged, aged and causing a number of diseases - cardiovascular, rheumatic, gastrointestinal, neurodegenerative, oncological, metabolic and other. Antioxidants, however, have had limited use in the prevention and treatment of oxidative stress-related diseases due to the high toxicity and low efficacy of many of them. Therefore, it remained necessary to identify effective antioxidants with little-to-no side effects. Since 2007, discovery molecular hydrogen (H2) to possess selective antioxidant properties, multiple studies have demonstrated H2 to show beneficial effects in diverse human disease (such as digestive, cardiovascular, central nervous, respiratory, reproductive, immune, endocrine systems diseases, cancer, metabolic syndrome, and aging). H2 is a specific scavenger of •OH, which is a very strong oxidant that reacts with nucleic acids, lipids, and proteins, resulting in DNA fragmentation, lipid peroxidation, and protein inactivation. Fortunately, H2 does not appear to react with other ROS having normal physiological functions in vivo. Due to its mild but effective antioxidant properties, H2 can reduce oxidative stress and cause numerous effects in cells and tissues, including anti-apoptosis, anti-inflammatory, anti-allergic and metabolic effects. This review discusses H2 biological effects, describes effective H2 delivery approaches and summarizes data on the results and prospects of H2 applications in the prevention of human diseases and therapy.

Numerical Analysis on Cone Length and its Effect on Performance of an Automotive Catalytic Converter

Internal combustion engines are one of the major contributors of air pollution. Exhaust gas from these engines contains HC, CO, NOx, PM and smoke which are the harmful pollutants to humans as well as to the environment. The stringent norms enforced by governments has necessitated in improving the after-treatment processes of these exhaust gas. A three-way catalytic converter is one of the most effective devices in treating the HC, CO and NOx pollutants into non-toxic gases. In this paper, numerical investigation is carried out by using commercial CFD code, ANSYS Fluent to analyse the effect of cone length on the conversion efficiency of the Catalytic Converter (CC). Pressure drop, back pressure and temperature are the parameters which are monitored in this study. The cone length of the CC is varied from 70mm to 90mm in steps of 10mm. All the CCs are analysed for identical test conditions. It is observed that temperature and pressure showed an appreciable decrease with increase in cone length to 90mm. On the other hand, velocity increases with increase in cone length to 90mm. A lower pressure drop and temperature is observed for the CC with cone length of 90mm. As conversion efficiency of the CC is dependent on the lower pressure drop, lesser back pressure and lower temperature, the CC with cone length of 90mm is found to be the apt choice.

Single-layer stanane as potential gas sensor for NO2, SO2, CO2 and NH3 under DFT investigation

The monolayer stanane in chair form is reported to be a novel sensor for environmentally toxic and non-toxic gas molecules for the first time. The structure, electronic and vibrational properties of all three possible conformations (chair, stirrup and boat) of stanane are studied in detail using density functional theory (DFT) based on an ab-initio technique. The interactions and charge transfer of environmentally toxic (NO2, SO2 and NH3) and non-toxic (CO2) gas molecules on the dynamically most stable hexagonal chair type hydrogenated stanene, viz. stanane has been investigated in detail. The most stable configuration, electronic properties, adsorption energies and charge transfer of these gases on stanane are systematically studied and discussed. The band gap of the pure stanane (0.52 eV) is noticed to be changed after interaction with gases. Moreover, the changes in the energy band gap and charge density is observed upon adsorption of NO2, SO2, NH3 and CO2 gases on p-type stanane based material. The results show that the selectivity of hydrogenated stanene based gas sensors is very important to enhance their sensitivity. It is found that all the gas molecules act as charge donors in which NO2 gas shows maximum adsorption on the stanane surface along with the maximum charge transfer. The nontrivial affectability and selectivity of stanane demonstrate its potential application in the field of gas sensors and superior impetuses.

Task-Specific Ionic Liquid Functionalized–MIL–101(Cr) as a Heterogeneous and Efficient Catalyst for the Cycloaddition of CO2 with Epoxides Under Solvent Free Conditions

A novel heterogeneous catalyst was synthesized by immobilization of a carboxylic acid- and imidazolium-based ionic liquid on the mesoporous MIL–101(Cr) (MIL–101(Cr)–TSIL) and used to convert abundant, nontoxic, economical and renewable CO2 gas to cyclic carbonates without the need for a cocatalyst or a solvent. The catalyst was characterized in detail by multiple techniques such as XRD, TEM, SEM, EDX, DR-FTIR, solid-state NMR, as well as N2 and CO2 adsorption measurements. The catalytic properties were studied by varying different parameters including amount of catalyst and epoxide, temperature, pressure, and reaction time. Under optimal conditions (100 mg catalyst, 15 mmol epoxide, 2.0 MPa CO2 pressure, 110 °C and 2 h reaction time) various cyclic carbonates were obtained with high yield and selectivity. MIL–101(Cr)–TSIL catalyst displayed good thermal stability and could be reused after simple separation without a significant decrease in its catalytic activity. Due to synergetic effect of the hydrogen b...

Light-enabled metal-free pinacol coupling by hydrazine.

Efficient carbon-carbon bond formation is of great importance in modern organic synthetic chemistry. The pinacol coupling discovered over a century ago is still one of the most efficient coupling reactions to build the C-C bond in one step. However, traditional pinacol coupling often requires over-stoichiometric amounts of active metals as reductants, causing long-lasting metal waste issues and sustainability concerns. A great scientific challenge is to design a metal-free approach to the pinacol coupling reaction. Herein, we describe a light-driven pinacol coupling protocol without use of any metals, but with N2H4, used as a clean non-metallic hydrogen-atom-transfer (HAT) reductant. In this transformation, only traceless non-toxic N2 and H2 gases were produced as by-products with a relatively broad aromatic ketone scope and good functional group tolerance. A combined experimental and computational investigation of the mechanism suggests that this novel pinacol coupling reaction proceeds via a HAT process between photo-excited ketone and N2H4, instead of the common single-electron-transfer (SET) process for metal reductants.

Scalable Continuous Flow Process for the Synthesis of Eflornithine Using Fluoroform as Difluoromethyl Source

The development of a scalable telescoped continuous flow procedure for difluoromethylation of a protected amino acid with fluoroform (CHF3, R-23) gas and subsequent high temperature deprotection to provide eflornithine, an important Active Pharmaceutical Ingredient (API), is described. Eflornithine is used for the treatment of sleeping sickness and hirsutism, and it is on the World Health Organization’s list of essential medicines. Fluoroform is produced in large quantities as a side product in the manufacture of polytetrafluoroethylene (PTFE, Teflon). Fluoroform is an ozone-benign and nontoxic gas, but its release into the environment is forbidden under the Kyoto protocol owing to its high global warming potential. The existing manufacturing route to eflornithine uses chlorodifluoromethane (CHClF2, R-22) which will be phased out under the Montreal protocol; therefore, the use of the fluoroform presents a viable cost-effective and more sustainable alternative. The process parameters and equipment setup we...