Highest Total Conversion Research Articles

Core-Shell Gold Nanoparticles@Pd-Loaded Covalent Organic Framework for In Situ Surface-Enhanced Raman Spectroscopy Monitoring of Catalytic Reactions.

A core-shell nanostructure of gold nanoparticles@covalent organic framework (COF) loaded with palladium nanoparticles (AuNPs@COF-PdNPs) was designed for the rapid monitoring of catalytic reactions with surface-enhanced Raman spectroscopy (SERS). The nanostructure was prepared by coating the COF layer on AuNPs and then in situ synthesizing PdNPs within the COF shell. With the respective SERS activity and catalytic performance of the AuNP core and COF-PdNPs shell, the nanostructure can be directly used in the SERS study of the catalytic reaction processes. It was shown that the confinement effect of COF resulted in the high dispersity of PdNPs and outstanding catalytic activity of AuNPs@COF-PdNPs, thus improving the reaction rate constant of the AuNPs@COF-PdNPs-catalyzed hydrogenation reduction by 10 times higher than that obtained with Au/Pd NPs. In addition, the COF layer can serve as a protective shell to make AuNPs@COF-PdNPs possess excellent reusability. Moreover, the loading of PdNPs within the COF layer was found to be in favor of avoiding intermediate products to achieve a high total conversion rate. AuNPs@COF-PdNPs also showed great catalytic activities toward the Suzuki-Miyaura coupling reaction. Taken together, the proposed core-shell nanostructure has great potential in monitoring and exploring catalytic processes and interfacial reactions.

Advances in the development of few-cycle gigawatt-peak-power mid-IR optical parametric amplifiers pumped by Cr:Forsterite laser using non-oxide nonlinear crystals

We demonstrate an experimental and theoretical comparison of non-oxide LiGaS2, HgGa2S4, and AgGaS2 crystals performance for wavelength conversion into the near and mid-IR range 1.5–8 μm in optical parametric amplifier pumped by Cr:Forsterite laser, delivering 100 fs pulses at 1.24 μm. It is shown that exceptionally high total energy conversion efficiency into the idler (4–5 μm) and signal (1.65–1.8 μm) waves up to 18% can be achieved using the HGS crystal, providing high nonlinearity, while the LGS crystal is more preferable for generating few-cycle mid-IR pulses due its unique dispersive properties. Our source features high peak power in gigawatt regime (0.4–2.4 GW) with pulse duration below 80 fs and optical synchronization with high harmonic generation (HHG) and THz beamlines, which is ideal for pump-probe experiments of nonlinear and strong-field physics.

Synthesis of an innovative SF/NZVI catalyst and investigation of its effectiveness on bio-oil production in liquefaction process alongside other parameters

Today, new energy sources alternative to fossil fuels are needed to meet the increasing energy demand. It is becoming increasingly important to constitute new energy sources from waste biomass through the liquefaction process. In this study, walnut shells (WS) were liquefied catalytically and non-catalytically under different parameters using the liquefaction method. In this process, the effect of silica fume/nano zero-valent iron (SF/NZVI) catalysts on the conversion rates was investigated. The catalyst was synthesized by reducing NZVI using a liquid phase chemical reduction method on SF. The SF/NZVI catalyst was characterized by scanning electron microscopy- energy dispersive X-ray (SEM–EDX), transmission electron microscope (TEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. The effect of various process parameters on the liquefaction process was investigated. In this context, the reaction temperature ranged from 300 to 400 °C, the solid/solvent ratio ranged from 1/1 to 1/3, the reaction time ranged from 30 to 90 min, and the catalyst concentration ranged from 1 to 6%. According to the results obtained, the most suitable operating conditions for non-catalytic experiments in liquefaction of WS were found to be temperature of 400 °C, reaction time of 60 min, and solid/solvent of 1/3. In catalytic conditions, the optimum values were obtained as temperature of 375 °C, reaction time of 60 min, solid/solvent ratio of 1/3, and catalyst concentration of 6%. The highest total conversion and (oil + gas) % conversion were 90.4% and 46.7% under non-catalytic conditions and 90.7% and 62.3% under catalytic conditions, respectively. Gas chromatography/mass spectrometry (GC/MS) analysis revealed the bio-oil was mainly composed of aromatic compounds (benzene, butyl-, indane and their derivatives,) and polyaromatic compounds (naphthalene, decahydro-, cis-, naphthalene, 1-methyl-.). The aim of increasing the quantity and quality of the light liquid product in the study has been achieved.

Reprogramming the Transition States to Enhance C-N Cleavage Efficiency of Rhodococcus opacusl-Amino Acid Oxidase.

l-Amino acid oxidase (LAAO) is an important biocatalyst used for synthesizing α-keto acids. LAAO from Rhodococcus opacus (RoLAAO) has a broad substrate spectrum; however, its low total turnover number limits its industrial use. To overcome this, we aimed to employ crystal structure-guided density functional theory calculations and molecular dynamic simulations to investigate the catalytic mechanism. Two key steps were identified: S → [TS1] in step 1 and Int1 → [TS2] in step 2. We reprogrammed the transition states [TS1] and [TS2] to reduce the identified energy barrier and obtain a RoLAAO variant capable of catalyzing 19 kinds of l-amino acids to the corresponding high-value α-keto acids with a high total turnover number, yield (≥95.1 g/L), conversion rate (≥95%), and space-time yields ≥142.7 g/L/d in 12-24 h, in a 5 L reactor. Our results indicated the promising potential of the developed RoLAAO variant for use in the industrial production of α-keto acids while providing a potential catalytic-mechanism-guided protein design strategy to achieve the desired physical and catalytic properties of enzymes.

Highly transient stimulated Raman scattering in SrMoO4 under ultrafast laser pumping with a controllable chirp.

For the first time, to the best of our knowledge, we demonstrate highly transient, multiwavelength, single-pass Raman generation with combined frequency shifts on two Raman modes of an SrMoO4 crystal with high total Raman conversion efficiency of up to 48% in conditions of competition with self-phase modulation (SPM). A 58-mm-long SrMoO4 crystal was used as the active medium under pumping by the 1030-nm, 40-µJ laser pulses with controllable dispersive stretching in a range of 0.25-6 ps at negative and positive chirping. The pump pulse chirping was optimized for both high- and low-frequency Raman shifts on the primary (888 cm-1) and secondary (327 cm-1) Raman modes of the crystal. At the optimal conditions, four Stokes components of stimulated Raman scattering (SRS) radiation with high- and low-frequency Raman shifts at the wavelengths of 1066, 1134, 1177, and 1261 nm were efficiently generated.

Direct liquefaction of low rank lignite with peach seed kernel and waste polypropylene for alternative fuel production

In this study, alternative fuel potentials to petroleum were investigated by direct liquefaction of peach seed kernel (PSK), Muğla-Yatağan lignite (MYL) and waste polypropylene (wPP) separately and together. The effects of PSK and wPP on the yield and selectivity of oil products obtained by direct liquefaction of MYL were also examined. Direct liquefaction experiments were performed in a batch reactor at 1/3 solid/solvent, reaction temperature of 400 °C and reaction time of 60 min. The highest total conversion and oil + gas yield were 95% and 85% direct liquefaction of wPP, respectively. According to the calorific value analysis of the chars, the highest gross calorific value of chars was 7709 cal/g in the liquefaction of PSK, and the lowest net calorific value was 2783 cal/g in the liquefaction of MYL. PSK and wPP increased oil yield of MLY from 28% to 60% and 68%, respectively. According to the GC-MS analysis of oils (light liquid products), alternative fuels to gasoline can be produced by direct liquefaction of PSK, wPP and wPP/MYL. Alternative fuels to diesel can be produced by direct liquefaction of MYL and PSK/MYL. The co-liquefaction of MYL with wPP and PSK improved the yield and product components of the oils. The oil + gas yield of MYL was approximately increased PSK by 12% and wPP by 6%.

Optimization of process parameters at direct liquefaction of waste PETs

Waste polyethylene terephthalate (wPET) was converted to liquid fuel by direct liquefaction method. Additionally, how the catalyst (sodium borohydride) and microwave pre-treatment affect the total conversion and the char yield were investigated. Direct liquefaction experiments were carried out in a batch reactor under non-catalytic/catalytic conditions, and reaction temperature of 325–425 °C, and solid/solvent ratio of ¼, and reaction time of 15–90 min, and microwave pre-treatment time of 3–10 min, and an initial nitrogen pressure of 20 bar. Both the microwave pre-treatment and sodium borohydride (NaBH4) increased the total conversion in the direct liquefaction of wPETs. According to fourier transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) analysis of char samples obtained in the direct liquefaction process, the NaBH4 was converted to sodium borate (Na2B8O13). NaBH4 made both hydrogen (H) donating and catalytic effect. The highest total conversion in direct liquefaction of wPETs, which has at the reaction time of 30 min, and the reaction temperature of 400 °C, and in presence of NaBH4, and the microwave pre-treatment of 3 and 8 min, was 62%. The optimum process parameters in direct liquefaction of wPETs are the reaction time of 30 min, and reaction temperature of 400 °C, and the microwave pre-treatment time of 3 min.

Co-liquefaction of Tunçbilek lignite with algae (spirulina species): Effect of process parameters and characterization of chars and oils

Nowadays, to reduce the cost of coal liquefaction and to produce a new liquid fuel alternative to petroleum, it is considered a more convenient method to liquefy coal and biomass together instead of solely coal liquefaction. Liquefaction experiments were carried out by changing the solvent/solid ratio of 1/1–5/1, reaction temperature 320–400 °C, reaction time 30–90 min, and algae/lignite ratio in the range of 1/1–5/1. As a result of this study, the most suitable process parameters obtained by considering total conversion are; solvent/solid ratio 3/1, reaction time 60 min, algae/lignite ratio 4/1, and reaction temperature 380 °C. Under these conditions, the highest total conversion is approximately 80% and 77% in catalytic and non-catalytic conditions, respectively. Under non-catalytic conditions of co-liquefaction experiments due to the GC-MS results, cyclopentane (raw material of motor oil), pentadecane, 2-methyl-naphthalene, octa-ethylene glycol, ethylene oxide heptamer are the main products of optimum parameters aforementioned for oil. They are mainly used in fuel technology and used in the chemical industry as raw materials mean low-cost production as well.

Two-Step Dry Gel Method Produces MgAPO-11 with Low Aspect Ratio and Improved Catalytic Performance in the Conversion of Methanol to Hydrocarbons

In this article, the synthesis, characterization and catalytic performance of three MgAPO-11 catalysts with distinct crystal morphologies (sunflower, ball and candy) are presented. Among the three samples, the candy-like MgAPO-11-C, with high crystallinity and uniform particle size (of about 1 µm), was synthesized for the first time by using a unique two-step dry gel method. Despite the similar acid strength of the three samples, the different and distinct morphologies of the catalysts resulted in very different methanol-to-hydrocarbons (MTH) performances. In particular, the candy-like MgAPO-11-C presented the best MTH performance with the highest total conversion capacity (4.4 gMeOH·gcatalyst−1 h−1) and the best selectivity to C5+ aliphatics (64%).

Effect of precipitating agents for the preparation of Fe-based catalysts on coal pyrolysis: Effect of Ba and Mg additives

In this work, the effect of Fe catalysts prepared with four precipitating agents (ammonia, urea, KOH and NaOH) on the catalytic pyrolysis of coal (BC) was investigated using a fixed-bed reactor under 0.1 MPa N2 and 700 °C. The results indicated that the precipitating agent significantly affected the activity of the Fe catalyst (5 wt%). Concretely, the Fe catalysts obtained with ammonia (Fe-X1) and urea (Fe-X2) as precipitating agents showed low activity was attributed to the small size of the particles blocked the pores of the coal, making it difficult for Fe species to be reduced. The Fe catalysts obtained with NaOH (Fe-X3) and KOH (Fe-X4) as precipitating agents showed good catalytic activity. However, the final metal Fe phase in Fe-X3 catalyst had a large particle size and aggregation. The Fe-X4 catalyst facilitated the preferential consumption of small defective structures and the removal of small aromatic rings, and the catalyst particles were uniformly dispersed and showed the best catalytic activity. Accordingly, the Fe-X4 catalyst had the highest total conversion (56.79 wt%) and H2 yield (93.66 ml/g) in coal pyrolysis. Moreover, Mg and Ba enhanced the activity of the Fe catalyst, which was attributed to the fact that Mg and Ba promoted the dispersion of Fe and prevented the formation of Fe-O-Si from the original Si in the coal, and the effect of Mg was greater than that of Ba.

Characterization of products obtained of waste polyethylene terephthalate by pyrolysis

AbstractIn this study, waste polyethylene terephthalate (wPET) was converted to liquid fuel by the pyrolysis method. It was also investigated both effects of microwave pre‐treatment and catalyst (sodium borohydride) on total conversion and oil + gas yield. The reaction temperature of 375–425°C and the reaction time of 30 min are sufficient for the pyrolysis of waste plastic samples in a batch reactor. In the pyrolysis of wPETs, the highest oil + gas yield of 45% was obtained under the conditions of reaction temperature of 425°C and reaction time of 30 min. The highest total conversion was 62% of microwave pre‐treated wPETs under catalytic conditions. It can be argued that microwave pre‐treatment and NaBH4 influence the oil + gas yield in pyrolysis experiments. According to the gas chromatography–mass spectrometry (GC–MS) analysis results of the oil products, they consist of aromatic, mono and multi‐ring aromatic compounds and polyaromatic compounds. Higher heating values of the solid products obtained in pyrolysis are approximately 4000–6000 cal/g. According to X‐ray diffraction analysis (XRD) of the solid products, they consist largely of crystalline terephthalic acid (C8H6O4).

Efficient short-time hydrothermal depolymerization of sugarcane bagasse in one-pot for cellulosic ethanol production without solid-liquid separation, water washing, and detoxification

In these studies, a low-cost and energy efficiency production of cellulosic ethanol from sugarcane bagasse (SCB) using one-pot without solid-liquid separation, water washing, and detoxification was performed. Firstly, SCB was pretreated using liquid hot water as the only reagent at 210 °C for a short time (0 min), and the solid liquid ratio (SLR) was 1:20 (w/v). Then, the whole slurry of pretreated SCB was enzymatically hydrolyzed and fermented for cellulosic ethanol in one-pot. The results indicated that the one-pot preparation for ethanol achieved a high total fermentable sugar conversion of 84.52 ± 1.24%, containing 88.61 ± 1.57% of glucose and 78.01 ± 1.63% of xylose. Moreover, the ethanol yield reached 257 ± 5.51 mg/g SCB, which was 77.56 ± 1.64% of the theoretical ethanol conversion from SCB. Importantly, there was no wastewater discharge in the whole process. Overall, the present work provides an economically feasible method for ethanol production.

Phosphotungstic acid on activated carbon: A remarkable catalyst for 5-hydroxymethylfurfural production

Phophotungstic acid (HPW) supported on activated carbon (AC) was prepared and used for dehydration of fructose to 5-hydroxymethylfurfural (HMF), a biomass-derived precursor for chemicals and fuels. Different characterization techniques showed that Keggin structure of HPW was maintained after impregnation process by incipient wetness method with ethanol as solvent. The high mass content of the active phase (50 wt%) on the support resulted in accessible acid sites and high acid density, important for the dehydration reaction. The effects of reaction time, catalyst amount, and temperature were investigated. The catalytic system with dimethyl sulfoxide (DMSO) as solvent provided an efficient transformation of fructose to HMF, resulting in high HMF yields (99.3 %) and total fructose conversion after 30 min of reaction at 140 °C. Fructose conversion was not significantly affected by the catalyst amount. On the other hand, the increase in temperature resulted in greater and faster conversion. HMF yield was deeply affected by all reaction variables. Moreover, HPW/AC was reused five times without significant loss of activity. Additionally, a kinetic evaluation was performed and the activation energy of fructose conversion to HMF was 109.4 kJmol−1.

STEP polymer degradation: Solar thermo-coupled electrochemical depolymerization of plastics to generate useful fuel plus abundant hydrogen

A global goal is to call for common solutions to the challenge of environmental conservation. The cheap, clean and green energy and processes help to beat the hazardous pollution of plastics. An action of the STEP (Solar Thermal Electrochemical Process) on the polymer is to create a novel vision of the depolymerization of plastics to generate valuable fuels plus abundant hydrogen. In this paper, a solar thermo-coupled electrochemical system was first designed and employed to realize the plastics depolymerization to useful fuels for enhanced the solar utilization and the chemical polymer conversion. Exemplified by polypropylene (PP), the plastics were efficiently converted to light fuel and hydrogen via the solar-driven electrolysis coupled with pyrolysis. The results demonstrated that the depolymerization temperature was greatly lowered compared to conventional pyrolysis. The STEP conversion rates increased with a lift of the temperature and current. The high total conversion rate was significantly achieved by reaching 68.48% at 350 °C, including the solid phase of 31.52%, the liquid phase of 7.85% and the gas phase of 60.63% (w/w), which was compared to the 28.39% of the sole pyrolysis. The hydrogen was evolved during the process in the final volume of 72.5 ml, which was about 9.3 times more than that of the pyrolysis at 400 °C. In the outdoor experiments, the total conversion reached 66.64% at 350 °C, which was compared to 26.37% of the pyrolysis only. The light hydrocarbons were richly produced in the distribution of C1–C5 hydrocarbons while only tiny amounts of methane and ethane were probed in the pyrolysis. The common mechanism and pathways can be tentatively proposed in a mode of the radically initiated thermochemical reactions and electrochemical redox by the induction of the solar thermo-coupled electrolysis.

Effect of the preparation method on particle size and reaction selectivity on naphthalene hydrogenation over Ni/H-MOR catalysts

Three Ni catalyst supported on mordenite zeolite with the same content of nickel, ∼2 wt.%, were prepared by incipient wetness impregnation (IWI), ionic exchange (IE), and deposition-precipitation (DP) methods. The catalysts were characterized by, X-ray diffraction (XRD), textural properties, temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and scanning electron microscopy / energy-dispersive spectroscopy (SEM/EDS). For all the catalysts conversion and selectivity were studied in naphthalene hydrogenation without or with thiophene in the feedstock. Despite the low nickel content, the three preparations showed a high initial total naphthalene conversion up to 94%. The Ni-IWI catalyst exhibited high selectivity to tetralin and deactivated very fast. Ni-IE catalyst had good activity; however, it shows deactivation and the main products are related to acid reactions. The Ni-DP shows high hydrogenation activity and was the most active catalyst, it generated decalins, especially cis-decalin and at a long reaction time on stream, the catalyst remains active. TEM and TPR results suggest that this behavior is related to the crystal sizes which in turn is conected with the preparation method. In presence of thiophene, all the catalysts deactivate; but the Ni-DP deactivation was slower.

Cylindrical thermoelectric generator with water heating system for high solar energy conversion efficiency

Thermoelectric generator (TEG) with water heating system, which utilizes solar energy with a high total energy conversion efficiency, is promising environmental technology for eco-housing and factories to reduce their carbon footprints. In this study, a newly developed cylindrical TEG consisting of ring-disk thermoelectric material is proposed showing that the total energy conversion efficiency is higher than that of a conventional pillar-type TEG. The cylindrical TEG is implemented using high-performance CoSb3-based filled skutterudite thermoelectric materials and a unique 45Ni-55Fe electrode as the hot-side junction. The solar TEG performance is demonstrated under the real sunlight, which is concentrated by a Fresnel lens. The maximum thermoelectric efficiency of the presented solar TEG is 1.8%, with a water heating efficiency of 59% when the temperature difference across the TEG is 428 °C. Further improvement should be achieved by lowering the internal resistance of the TEG and increasing the average dimensionless figure of merit of the thermoelectric materials.

Production of hydrogen from algae: Integrated gasification and chemical looping

Due to their high potential and beneficial characteristics, algae is considered as very promising energy source in future. In this study, an integrated conversion system of algae to hydrogen is proposed with the objective of high total energy conversion efficiency. The proposed system mainly covers algal drying, gasification, and chemical looping. To facilitate optimum heat circulation throughout the proposed system, enhanced process integration is adopted. It combines exergy recovery and process integration technologies in order to achieve a wasted energy, hence the total energy efficiency can be improved significantly. In the proposed system, to convert algae to hydrogen, steam gasification and syngas chemical looping are integrated as the main conversion. Iron oxide is employed as the oxygen carrier, and is circulated among the reactors in the chemical looping module. Process modeling and calculation is performed using ASPEN Plus, and the total energy efficiency, including hydrogen production and power generation, is evaluated. Several operating parameters including target moisture content in drying, steam-to-biomass ratio in gasification, and chemical looping pressure, are observed. From the results, it is shown that the proposed system is potential to convert algae to hydrogen with high total energy efficiency, which is higher than 70%. Both target moisture content and steam-to-biomass ratio influence strongly the total energy efficiency. On the other hand, chemical looping pressure show insignificant effect to total energy efficiency.

Co-liquefaction of Elbistan Lignite with Manure Biomass; Part 2 - Effect of Biomass Type, Waste to Lignite Ratio and Solid to Liquid Ratio

Most coal hydrogenation processes require a large quantity of hydrogen. In general, a coal derived liquid such as anthracene oil was used as a hydrogen donor solvent. Tetralin, partially hydrogenated pyrene, phenantrene and coal-derived solvents, which contain hydroaromatic compounds, are efficient solvents to donate hydrogen. In an attempt to reduce the high cost of hydrogen, part of the hydrogen was replaced by a low cost hydrogen donor solvent. This must be hydrogenated during or before the process and recycled. To reduce the cost of hydrogen donor vehicles instead of liquids recycled from the liquefaction process or several biomass types, industrial by products, liquid fractions derived from oil sands bitumen were successfully used to solubilize a coal from the past. In an attempt to reduce the high cost of hydrogen, part of the hydrogen was replaced by a low cost hydrogen donor solvent. However, when hydrogen is supplied from the hydroaromatic structures present in the solvent, the activity of coal minerals is too low to rehydrogenate the solvent in-situ. Nevertheless, a decrease of using oxygen, in addition to enhanced usage of the hydrogen supply by using various waste materials might lead to a decrease of the cost of the liquefaction procedure. So instead of using tetralin another feeding material such as biomass is becoming another solution improving hydrogen donor substances. Most of the liquefaction process were carried out in a batch reactor, in which the residence time of the liquefaction products is long enough to favour the retrogressive reactions, early studies which are related to liquefaction of coal with biomass generally focus on the synergetic effects of coal while biomass added. Early studies which are related to liquefaction of coal with biomass generally focus on the synergetic effects of coal while biomass added. Alternatively, to understand the hydrogen transfer from biomass to coal, in this study, Elbistan Lignite (EL) with manure, tea pulp and waste plastic liquefied and to understand hydrogen quantity change after liquefaction, (H/C)atomic ratio of products obtained. Due to the highest oil conversion of manure biomass and highest (H/C)atomic ratio results show manure is the favourable biomass for EL amongst the other biomass used. And liquid/solid ratio optimized. About high total conversion of oil products the optimum ratio obtained as 3/1. And also EL with manure liquefied with the w/EL ratio between 0:1 to 1:1. As a result, by thinking about the yield values obtained, the optimum waste to lignite ratio found to be 1:1.

Influence of Operating Parameters on Biomass Conversion under Sub‐ and Supercritical Water Conditions

AbstractThe influence of reaction pressure, reaction time, reaction temperature, and biomass‐to‐water mass ratio R on the conversion of miscanthus biomass to biofuels under sub‐ and supercritical water (SCW) conditions was investigated. The highest total conversion was obtained under SCW conditions and the heating value increased under subcritical and SCW conditions. The findings herein show that near‐supercritical and supercritical water at 400 °C and high pressure can be an effective reaction medium for converting biomass to oils with relatively low oxygen contents in high yields.

Heterocyclic bismuth(iii) compounds with transannular N→Bi interactions as catalysts for the oxidation of thiophenol to diphenyldisulfide

Aerial oxidation of thiophenol to diphenyl disulfide proceeds with high reaction rates, total conversion and selectivity in ionic liquids by using diorganobismuth(iii) catalysts.