Direct Conversion Process Research Articles

Screening of CO2 utilization routes from process simulation: Design, optimization, environmental and techno-economic analysis

This work aims at evaluating potential direct CO2 conversion processes through systematic screening and process simulation. Fifteen direct routes converting CO2 to carbonates or carbamates, with in situ chemical dehydration using 2-cyanopyridine (2-CP) are focused. The work covers an extensive examination (and supplement) on the physical properties, selection of promising routes, process simulation, optimization, environmental, and techno-economic evaluation. Firstly, three promising routes were selected, producing dimethyl carbonate (DMC), dipropyl carbonate (DPC), and Isopropyl N-phenylcarbamate (IPPhCM), based on three criteria: azeotropic search, product selectivity and reacting conditions. Next, the corresponding processes were simulated, optimized, heat-integrated, and systematically compared with the previously-proposed diethyl carbonate (DEC) process through environmental and economic analysis. From environmental analysis, the CO2 emission rate (CO2-e, in kg/kg-product) was 0.067, 0.088, −0.040 and −0.154 for producing DMC, DPC, IPPhCM and DEC, respectively. By reducing the excess ratio used for reaction (i.e. 2-CP/alcohol or amine/alcohol), the CO2-e improved to −0.122, −0.086, and −0.117 for producing DMC, DPC and IPPhCM, respectively. Finally, the minimum required selling prices (MRSP) at 15 % internal rate of return (IRR) were determined, with the unit price of 2-CP, 2-picolinamide (2-PA), and the reactor residence time regarded as uncertainties. The MRSPs for DMC, DPC, IPPhCM and DEC are found in the range of 1.50–4.96, 2.29–4.24, 2.07–4.06 and 1.12–2.81 (all in USD/kg), respectively. Future studies exploring the commercial availability and the regeneration of 2-CP, and the feasibility of reducing the excess ratio and the reaction residence time are considered helpful.

Electrochemically Engineered, Highly Energy-Efficient Conversion of Ethane to Ethylene and Hydrogen below 550 °C in a Protonic Ceramic Electrochemical Cell

Ethylene is one of the largest building blocks in the petrochemical industry, mainly produced by steam cracking of ethane derived from naphtha or shale gas at high temperatures (>800 °C). Despite its technical maturity and economic competitiveness, the thermal steam cracking of ethane is highly energy-intensive. Herein, an electrochemically engineered direct conversion process of ethane to produce hydrogen and ethylene using a planar protonic ceramic membrane reactor with a bi-functional three-dimensional catalytic electrode is reported, with a single-pass ethane conversion of 40% and ethylene yield of 26.7% at 550 °C. Compared with the industrial ethane steam cracking, this method saves process energy input by 45.1% and improves process energy efficiency by 50.6%, based on comprehensive process simulation using Aspen Plus software. Further, steam electrolysis treatment under the solid oxide electrolysis cell mode can regenerate the system’s catalytic performance and significantly alleviate catalytic degradation by 74%, demonstrating high techno-economic viability.

Engineering PdAu Nanowires for Highly Efficient Direct Methane Conversion to Methanol under Mild Conditions

The direct conversion of methane to high-value chemical feedstock is immensely meaningful but challenging. This work reports the preparation of alloyed PdxAuy nanowires (NWs) with different Pd/Au atom ratios by using a simple and facile method. The influence of alloyed PdxAuyNWs structure and reaction conditions have been methodically studied for the direct methane conversion process. It is proposed that the proper adsorption capacity of methane and the electronic synergy effect for alloyed PdxAuy NWs are the key factors to improve methane conversion and methanol selectivity. In addition, alloyed PdxAuy NWs show an excellent selectivity over 90% for methanol product due to the special one-dimensional structure, and the Pd12Au1 NWs catalyst exhibits the highest yield of methanol product of 522.5 μmol g–1 h–1 at 70 °C with adding 500 μmol H2O2. This work demonstrates the use of alloyed PdxAuy NWs catalysts for the direct conversion of methane to methanol with high-efficiency and selectivity and offers intriguing pathways to further boost their performance in catalysis reactions.

Study on direct conversion of Naomaohu coal pyrolysis heavy oil to aromatics

The pyrolysis tar from Naomaohu coal was separated by distillation apparatus. Four components of heavy oil above 320°C were analyzed. The result showed the colloid content was 28.84% and the asphaltene content was 35.12%, and both were difficult to convert in hydrogenation. 13C-NMR results showed that the relative molar ratio of aromatic carbon in heavy oil was 71.16%, which indicated that aromatic compounds in heavy fraction were dominant. The heavy fraction was treated by suspension bed and fixed bed cracking. The asphaltene and colloid were almost completely converted. The yield of naphtha with boiling point below 180°C was 66.95%, and the diesel with boiling point higher than 180°C was 17.84%. Oxygen, nitrogen and sulfur contained in heteroatoms were almost completely removed. Catalytic reforming of naphtha was carried out. The results showed that the number of cycloalkanes decreased by 60.23%, and the number of aromatics increased by 65.8%, which indicated that the dehydrogenation and aromatization of cycloalkanes occurred mainly. While the number of n-alkanes decreased by 13.42%, which indicated that the isomerization and cyclization of n-alkanes occurred simultaneously. The catalytic reforming oil contained more benzene, toluene, xylene and ethylbenzene, and the contents were 11.97%, 23.15%, 21.43% and 3.48% respectively. In the direct conversion process of heavy oil from coal pyrolysis, the transmissibility of basic structural units of coal was significantly reflected.

Direct conversion of methane to oxygenates on porous organic polymers supported Rh mononuclear complex catalyst under mild conditions

Converting CH4 to value-added products has been attracting more and more attention. However, most routes for CH4 catalytic conversion are performed at high temperature. Here we report a direct catalytic conversion process of CH4 on a Cu species promoted Rh mononuclear complex catalyst embedded on porous organic polymers (Rh1-Cu/POPs) under the atmosphere of CH4, CO and O2 at 150 °C in the aqueous solution. Through the combined characterization, mononuclear complex of (CH3)RhX(CO)(PPh3)2 was considered as the stay species, X denoted Cl or I. The iodine species participated the coordination of Rh mononuclear carbonyl complex and further promoted the transformation of CH3 to produce more oxygenated products, especially for the acceleration of acetic acid production. The space time yield of total oxygenated products, including CH3OH, HCOOH, HOCH2OH and CH3COOH, on iodine species promoted Rh1-Cu/POPs catalyst reached as high as 289.3 g/(kgcat ⋅h), recycled for five times without obvious decay.

Robust Multi-Objective Optimization for Response Surface Models Applied to Direct Low-Value Natural Gas Conversion Processes

The high proportion of CO2/CH4 in low aggregated value natural gas compositions can be used strategically and intelligently to produce more hydrocarbons through oxidative methane coupling (OCM). The main goal of this study was to optimize direct low-value natural gas conversion via CO2-OCM on metal oxide catalysts using robust multi-objective optimization based on an entropic measure to choose the most preferred Pareto optimal point as the problem’s final solution. The responses of CH4 conversion, C2 selectivity, and C2 yield are modeled using the response surface methodology. In this methodology, decision variables, e.g., the CO2/CH4 ratio, reactor temperature, wt.% CaO and wt.% MnO in ceria catalyst, are all employed. The Pareto optimal solution was obtained via the following combination of process parameters: CO2/CH4 ratio = 2.50, reactor temperature = 1179.5 K, wt.% CaO in ceria catalyst = 17.2%, wt.% MnO in ceria catalyst = 6.0%. By using the optimal weighting strategy w1 = 0.2602, w2 = 0.3203, w3 = 0.4295, the simultaneous optimal values for the objective functions were: CH4 conversion = 8.806%, C2 selectivity = 51.468%, C2 yield = 3.275%. Finally, an entropic measure used as a decision-making criterion was found to be useful in mapping the regions of minimal variation among the Pareto optimal responses and the results obtained, and this demonstrates that the optimization weights exert influence on the forecast variation of the obtained response.

Direct Conversion of Human Fibroblasts to Induced Neurons.

Progressive aging is a physiological process that represents a central risk factor for the development of several human age-associated chronic diseases, including neurodegenerative diseases. A major focus in biomedical research is the pursuit for appropriate model systems to better model the biology of human aging and the interface between aging and disease mechanisms. Direct conversion of human fibroblasts into induced neurons (iNs) has emerged as a novel technology for the in vitro modeling of age-dependent neurological diseases. Similar to other cellular reprogramming techniques, e.g., iPSC-based cellular reprograming, direct conversion relies on the ectopic overexpression of transcription factors, typically including well-known pioneer factors. However, in contrast to alternative technologies to generate neurons, the entire process of direct conversion bypasses any proliferative or stem cell-like stage, which in fact renders it the unique aptitude of preserving age-associated hallmarks from the initial fibroblast source. In this chapter, we introduce direct conversion as a practical and easy-to-approach disease model for aging and neurodegenerative disease research. A focus here is to provide a stepwise protocol for the efficient and highly reproducible generation of iNs from adult dermal fibroblasts from human donors.

Solution Combustion Synthesis of Transparent Conducting Thin Films for Sustainable Photovoltaic Applications

Sunlight is arguably the most promising continuous and cheap alternative sustainable energy source available at almost all living places of the human world. Photovoltaics (PV) is a process of direct conversion of sunlight into electricity and has become a technology of choice for sustainable production of cleaner and safer energy. The solar cell is the main component of any PV technology and transparent conducting oxides (TCO) comprising wide band gap semiconductors are an essential component of every PV technology. In this research, transparent conducting thin films were prepared by solution combustion synthesis of metal oxide nitrates wherein the use of indium is substituted or reduced. Individual 0.5 M indium, gallium and zinc oxide source solutions were mixed in ratios of 1:9 and 9:1 to obtain precursor solutions. Indium-rich IZO (A1), zinc-rich IZO (B1), gallium-rich GZO (C1) and zinc-rich GZO (D1) thin films were prepared through spin coating deposition. In the case of A1 and B1 thin films, electrical resistivity obtained was 3.4 × 10−3 Ω-cm and 7.9 × 10−3 Ω-cm, respectively. While C1 films remained insulating, D1 films showed an electrical resistivity of 1.3 × 10−2 Ω-cm. The optical transmittance remained more than 80% in visible for all films. Films with necessary transparent conducting properties were applied in an all solution-processed solar cell device and then characterized. The efficiency of 1.66%, 2.17%, and 0.77% was obtained for A1, B1, and D1 TCOs, respectively, while 6.88% was obtained using commercial fluorine doped SnO2: (FTO) TCO. The results are encouraging for the preparation of indium-free TCOs towards solution-processed thin-film photovoltaic devices. It is also observed that better filtration of precursor solutions and improving surface roughness would further reduce sheet resistance and improve solar cell efficiency.

An integrated methane dehydroaromatization and chemical looping process

Most of the natural gas co-produced in oil wells is flared due to the high transportation costs of bringing it to market. Onsite upgrading of natural gas to liquid products could address this issue but there are few processes for effective direct conversion of natural gas to liquid products. Methane dehydroaromatization (DHA) over Mo/H-ZSM-5 offers a potential route to a value-added liquid product, however, DHA conversion is severely limited by thermodynamics at most industrially relevant temperatures. Here we propose an integrated process coupling methane DHA, chemical looping for selective hydrogen oxidation, and subsequent water removal to achieve higher yields of aromatic products limited by the thermodynamics in one-pass systems. We validate this process via the construction and operation of a one-of-a-kind multibed recirculating reactor, and achieve a combined aromatics yield of 42%. Detailed technoeconomic analysis of the process for mobile applications show that such a process could be economically viable under certain circumstances.

Facile two-step synthesis of innovative anode design from tin-aminoclay (SnAC) and rGO for Li-ion batteries

A tin-aminoclay/reduced graphene oxide (SnO2-SnAC/rGO) electrode with significantly enhanced electrochemical performance was successfully fabricated by a facile two-step method entailing microwave treatment (1st step) and heat treatment (2nd step) synthesis processes. In step 1, the complete reduction of GO to rGO by microwave ensures the removal of most oxygen-containing functional groups on the material surface leading to improvement of its electrical conductivity along with the formation of SnO2 dots of 3–4 nm diameter. In step 2, the tin crystals are formed more stably in the SnAC/rGO framework by the heat-treatment process under Argon (Ar) gas via the direct conversion process of Sn2+ active sites within the SnAC structure. With this two-step process, the synthesized material possesses many unique synergistic effects, all leading to beneficial features (i.e., improved specific capacity, high rate capability, and long cycle life stability compared with SnO2-SnAC and pure rGO electrodes) for application to battery electrodes. Especially, SnO2-SnAC/rGO-500 °C (1:1) exhibits outstanding performance in terms of cyclic performance (650 mAh g−1 after 100 cycles at 100 mA g−1) and rate capability.

Manganese Metaphosphate Mn(PO3)2 as a High‐Performance Negative Electrode Material for Lithium‐Ion Batteries

AbstractWe report a novel negative conversion electrode material, manganese (II) metaphosphate Mn(PO3)2. This compound can be synthesized by a facile solid‐state method, and after carbon‐coating delivers an attractively high reversible capacity of 477 mAh/g at 0.1 C and 385 mAh/g at 1 C. We investigated the reaction mechanism with a combination of ex situ X‐ray absorption spectroscopy, in situ X‐ray diffraction, and high‐resolution transmission electron microscopy. We observed a direct conversion process by monitoring the first discharge in operando, in which Mn(PO3)2 reacts with Li to give fusiform Mn nanograins a few Ångstroms in width, embedded in a matrix of lithium conducting LiPO3 glass. Due to the fine nanostructures of the conversion products, this conversion reaction is completely reversible.

Homogeneous functionalization of light alkanes

Light alkanes are the most abundantly available carbon-based feedstocks on earth and as major constituents of natural gas and oil-associated gas. Compared with oil, natural gas is considered a greener fuel and promising alternative for energy and chemical production. However, the grand challenge in the chemistry of light alkanes utilization is the development of an efficient method for the selective activation C–H bond. The transportation issue comes from the low boiling point. On the other hand, these unactivated molecules are hard to be activated under mild conditions because of their high bond dissociation energy and low acidity. Moreover, the functionalized products, such as ethylene or methanol, have higher reactivity than light alkanes. Due to these challenges, it is vital that develop efficient processes to achieve value-added convert under economic and green reaction conditions. In this review, we summarized the recent progress in the field of homogeneous functionalizations of light alkanes and was subtitled to four different aspects according to the mechanism, including electrophilic substitution, oxidative addition, carbene insertion, and free radical substitution. However, developing a new, lower temperature, economic, and green direct light alkanes conversion process is still needed to address.

Preparation of bimetal-based FeNi-N/C catalyst and its electrocatalytic oxygen reduction performance

A kind of bimetal-based FeNi-N/C catalysts were prepared by combining ultrasonic reaction and high temperature heat treatment using dicyandiamide (DCD) as nitrogen source, FeCl3·6H2O and Ni(OAc)2·4H2O as bimetal source, BP2000 as carbon carrier. The composition and structure of the catalysts as-prepared were characterized by XRD, FT-IR and XPS. The catalytic activity of the catalysts on the oxygen reduction reaction(ORR) under alkaline conditions were tested by using linear sweep voltammetry (LSV) with a rotating disk electrode, and the prepared conditions, active site composition, the stability and methanol resistance of the as-prepared catalysts and the kinetic ORR mechanism were studied successively. The results show that the best FeNi-N/C-800 catalytic activity for ORR with the onset potential of 0.965 V (vs. RHE). The number of transferred electrons in catalytic ORR process is between 3.59 and 3.98, indicating the 4e− dominated ORR mechanism and a direct conversion process from O2 into H2O. The nature of the metal and the heat treatment temperature are important key factors in the preparation of the catalyst. From this work, Ni can be regarded as a catalyst for N and metal Fe atoms into the carbon support, and Fe-Nx-C (Fe bonds with pyridine-N) is the main active sites of the catalyst FeNi-N/C and a synergistic effect of the two sites of Fe-Nx-C and Ni-Nx-C enhances their catalytic activity for ORR further.

Advanced X‐ray Absorption Spectroscopy Analysis to Determine Structure‐Activity Relationships for Cu‐Zeolites in the Direct Conversion of Methane to Methanol

AbstractAn industrial process for direct conversion of methane to methanol (DMTM) would revolutionize methane as feedstock for the chemical industry and it would be a cherished contribution to climate change mitigation. At the present stage, it is a rather remote perspective, but the search for the materials that would make it possible and economically viable, is very active. Cu‐exchanged zeolites have been shown to cleave the C−H bond of methane at low temperatures (≤200 °C), and has been extensively studied for the stepwise DMTM conversion over the last decades. The determination of the speciation of CuxOy‐species in zeolites and the understanding of their role in the reaction mechanism has been heavily debated. Lately, advanced X‐ray absorption spectroscopy (XAS) analysis has been standing out as a powerful technique for investigating the behavior of Cu in zeolites. In this review we focus on thein situandoperandostudies of changes in the electronic and structural properties of Cu, during the different steps of the DMTM conversion uncovered by XAS, which have led to new and insightful information about the complex behavior of Cu‐zeolites in the DMTM process.

An Experimental Examination on Ice Pattern for Casting Process

The casting process has come to wide range of use in manufacturing process. Wooden, aluminum and wax are mostly used materials for pattern in the casting. However, it contains some limitations such as expansion of wax pattern, cracks in ceramic, complexity limitation in wooden pattern and removal of wooden pattern from sand mold etc., in the light of this, the work attempts to use ice pattern for mold making and sublimating ice pattern to create cavity in the mold for pouring. Ice pattern can be produced with aid of rapid freeze prototyping (RFP) or by traditional ice mold method. Integration of RFP/Traditional ice mold method with sublimated ice in casting process allows the quick creation of complex metal parts. Here, mold is produced by ice pattern and then ice pattern is removed by sublimation process (sublimation is the process of direct conversion of solid phase to vapor phase of matters) to create cavity. The advantages of no parts geometric complexity problems , No need of parting line design, less complex limitation, sound casting, clean and less cost of process operation, and better performance. This paper will present our creation study on sublimation of ice pattern in greensand for mold making for casting, and results of the cast piece obtained from sand casting process.

Water Molecules Facilitate Hydrogen Release in Anaerobic Oxidation of Methane to Methanol over Cu/Mordenite

Development of a suitable mild-condition process for direct conversion of methane to methanol faces multiple challenges, the principal ones being the higher reactivity of the primary oxidation prod...

Energy and exergy equilibrium analysis of Stirling-type thermal compressor (STC)—The core part in thermal-driven Vuilleumier machines

The Stirling-type machines show high-potential efficiency in energy conversion process. The direct conversion process from heat at relative high temperature to cooling power can be realized by the thermal-driven Stirling refrigerator, so called Vuilleumier refrigerator. However, the relative low efficiency of the actual Vuilleumier machine (including refrigerator and heat pump) caused by various losses hinders itself further development. The Stirling-type thermal compressor (STC) is the core heat-work conversion part in the Vuilleumier machine and most exergy loss is concentrated here. For better understanding the internal heat-work conversion and loss process in STC, firstly, the thermodynamic equilibrium relationships of energy and exergy in STC were discussed. Secondly, a reliable three-order model of STC was built and the RC-load operation and no-load operation were compared under the instruction of the equilibrium relationships above. Thirdly, detailed parameter effects on the output performance, loss composition, exergy efficiency and thermal-driven characteristic were carried out. At last, the optimization principle of external loss in STC was studied, which could improve the STC’s exergy efficiency to 60%.

(Cu, Ag)-DOPED ZnS WITH WIDE VISIBLE LIGHT RANGE ABSORPTION FOR WATER SPLITTING: A THEORETICAL AND EXPERIMENTAL STUDY

Photocatalytic water splitting using a semiconductor photocatalyst is a promising process for direct solar energy conversion. In this study, the feasibility of the photocatalytic H2 evolution on (Cu, Ag)- doped ZnS catalysts under visible light irradiation has been investigated by using first-principles density functional theory calculations and experimental studies. The present results reveal that (Cu, Ag)-doped ZnS structures have relatively small formation energy, implying that they are more easily obtained in experiment. Moreover, the absorption is enhanced obviously in the visible-light region for (Cu, Ag)-doped ZnS, but their energy levels are still suitable for water splitting to generate H2, which means that (Cu, Ag)-doped ZnS structures are promising candidate photocatalyst materials for H2 production driven by visible light. ZnS and (Cu, Ag)-doped ZnS were prepared using chemical precipitation method. (Cu, Ag)-doped ZnS samples showed an improved photocatalytic activity compared with undoped ZnS. Ag-doped ZnS (0.15 g L[Formula: see text] has the highest hydrogen evolution rate of 794.6 [Formula: see text]mol[Formula: see text] h[Formula: see text] [Formula: see text] g[Formula: see text] at pH 3 (0.1 M Na2S solution as a sacrificing agent).

Cascade Process for Direct Transformation of Aldehydes (RCHO) to Nitriles (RCN) Using Inorganic Reagents NH2OH/Na2CO3/SO2F2 in DMSO.

A simple, mild, and practical process for direct conversion of aldehydes to nitriles was developed feathering a wide substrate scope and great functional group tolerability (52 examples, over 90% yield in most cases) using inorganic reagents (NH2OH/Na2CO3/SO2F2) in DMSO. This method allows for transformations of readily available, inexpensive, and abundant aldehydes to highly valuable nitriles in a pot, atom, and step-economical manner without transition metals. This protocol will serve as a robust tool for the installation of cyano-moieties to complicated molecules.

Numerical Model of the Simple Thermophotovoltaic Structure

Thermophotovoltaic (TPV) belongs to the third generation of photovoltaics. It is a direct energy conversion process from heat to electricity via photons. This technique works on the principle of an effect of use as much of the radiation spectrum for optimal system operation. These systems have great potential application in commerce, military and aerospace industry. This article deals with thermal simulation, which includes the radiation effect model, of the thermophotovoltaic emitter and its influence on the simple photovoltaic system.