Loss In Conversion Research Articles

Pt supported nitrogen doped hollow carbon spheres for the catalysed reduction of cinnamaldehyde

Carbon and nitrogen coated Stöber silica spheres were prepared by a standard procedure using acetonitrile at different CVD temperatures (800–1000°C) and as a function of time (1–4h). HF treatment was used to remove the silica from the carbon coated silica to give monodispersed nitrogen doped hollow carbon spheres (N-HCSs; shell thickness=50nm). The surface areas of the N-CSs increased significantly after removal of the SiO2 core (N-HCS=47m2/g). Platinum nanoparticles, prepared by a [Pt(COD)Cl2] deposition method were dispersed (d=2.8±0.4nm) on the N-HCS supports. Thermal treatment of the Pt/N-HCS900-4 (prepared at 900°C for 4h) in a 5% H2/Ar atmosphere at 120°C (Pt/N-HCS900-4-120) and 300°C (Pt/N-HCS900-4-300) gave metallic Pt (2.48%) which was confirmed by XRD and XPS studies. The XPS N1s spectra of Pt/N-HCS900-4-120 showed the presence of quaternary, pyridinic and pyrollic nitrogen atoms. These nitrogen doped carbon supported Pt nanoparticle catalysts were observed to reduce cinnamaldehyde to the unsaturated alcohol, cinnamyl alcohol (isopropanol/30bar H2/80°C) with >99% conversion and selectivity. The catalyst used in the reduction of cinnamaldehyde to cinnamyl alcohol could be recycled 12 times with minimal loss in conversion and this correlated with the small amount of Pt leaching or physical loss of catalyst (<2%). The corresponding Pt/catalyst made on undoped HCSs showed a much greater loss of activity with recycling. It is seen that N doping of carbon is an effective method to bind Pt to carbon.

Dynamic iteration stopping algorithm for non-binary LDPC-coded high-order PRCPM in the Rayleigh fading channel

This paper mainly studies the association between non-binary low-density parity-check codes and high-order partial response continuous phase modulation, which prevents information loss in the mutual conversion of bit and symbol probabilities. Although the iterative detection and decoding technique applied in this system can obtain good performance/complexity tradeoff, the iterative process still encounters the problems of positive feedback and relatively large decoding delay, similar to other iterative coded modulation systems. The inhibitory effects of different extrinsic information exchange methods on positive feedback under different signal-to-noise ratio (SNR) conditions are investigated in this work to address this issue. Two dynamic iterative stopping algorithms, namely, cross entropy and hard decision aided combined with weighted extrinsic information exchange for cases with medium and high SNRs, are then proposed. Extrinsic information exchange between the demodulator and the decoder is conducted in the two algorithms through weighted processing. Iterative detection is subsequently performed based on two stopping criteria of dynamic iterative decoding. Theoretic analysis and simulation results for the Rayleigh fading channel show that the combination of weighted extrinsic information exchange and the two dynamic iterative stopping algorithms effectively resists positive feedback and improves the convergence of iterative detection and bit error rate performance. Such a combination also reduces the average iteration number to improve the real-time performance of iterative detection and decoding.

Investigation of Sawmill Management and Technology on Waste Reduction at Selected Sawmills in Moratuwa, Sri Lanka

The demand for sawn timber and wood-based products is rising steadily with new developments and the growing domestic consumption in Sri Lanka. Therefore, it is important to strike a balance between the increasing demand and consumption of forest resources. Thus, the key objective of this study was to investigate the effects of sawmill management and technological parameters on loss in conversion from logs to sawn timber and to compare the sawmill efficiency in private sawmills with the state timber corporation sawmill.Sawmill management and technological parameters were studied in 21 private sawmills and State Timber Corporation sawmill in Kaldemulla to evaluate the effects on loss in conversion. The selected sawmills represent all types available in Sri Lanka, i.e., frame saw, circular saw and band saw mills. Based on the results, mean percentage loss in conversion of teak and mahogany timber for all sawmills (private and State Timber Corporation) in Moratuwa found to be 53.10%. Significant differences were observed in loss in conversion values between the three categories of private sawmills as well as within sawmills of the same category. It was shown that loss in conversion values also varied with sawmill management and technological parameters such as type of machinery employed, sharpening frequency and sawyer’s experience, saw setting, availability of log alignment equipment and saw guards, oversizing and sawn timber sizes.

Efficient conversion of carbohydratesto ethoxymethylfurfural and levulinic acid ethyl ester under the catalysis of recyclable DMSO/Brønsted acids

This paper presents a novel and environment‐friendly process for the dehydration of carbohydrates to ethoxymethylfurfural (EMF) and levulinic acid ethyl ester (LAEE) under the catalysis of DMSO/H2SO4. The catalyst was recycled efficiently and easily over seven times without any significant loss in fructose conversion. For the conversion of fructose and inulin, EMF and LAEE were obtained in 83% and 80% total yields, respectively. The effects of catalyst loading, reaction temperature, and reaction time on dehydration reaction were investigated.

Interplay between zirconium addition and morphology/catalytic performance of HPW/PEHA/SBA-15 composites towards selective oxidation of benzyl alcohol

A series of HPW/PEHA/ZrSBA-15 catalysts with varied Zr contents were synthesized and used for the selective oxidation reaction of benzyl alcohol. The catalysts were characterized by N2 adsorption–desorption, XRD, SEM, TEM, XPS, FT-IR and ICP-AES analysis techniques. It was found that, through simply tuning the initial molar ratios of Zr/Si, both the morphology and catalytic performance of resultant catalysts can be tailored. More interestingly, the incorporation of zirconium ions, which can endow the ordered framework with enhanced acidity, can effectively stabilize loaded pentaethylenehexamine (PEHA) and facilitate a higher dispersion and attraction of HPW clusters. By carefully screening the catalytic results of the selective oxidation of benzyl alcohol, an optimal value of Zr/Si molar ratio was found to be 0.05, under which platelet ZrSBA-15 with ordered framework can be facilely obtained, leading to a maximum catalytic activity with negligible loss in selectivity and conversion even after five times of recycling test.

Multi-factor controls on terrestrial carbon dynamics in urbanized areas

Abstract. As urban land expands rapidly across the globe, much concern has been raised that urbanization may alter the terrestrial carbon cycle. Urbanization involves complex changes in land structure and multiple environmental factors. Little is known about the relative contribution of these individual factors and their interactions to the terrestrial carbon dynamics, however, which is essential for assessing the effectiveness of carbon sequestration policies focusing on urban development. This study developed a comprehensive analysis framework for quantifying relative contribution of individual factors (and their interactions) to terrestrial carbon dynamics in urbanized areas. We identified 15 factors belonging to five categories, and we applied a newly developed factorial analysis scheme to the southern United States (SUS), a rapidly urbanizing region. In all, 24 numeric experiments were designed to systematically isolate and quantify the relative contribution of individual factors. We found that the impact of land conversion was far larger than other factors. Urban managements and the overall interactive effects among major factors, however, created a carbon sink that compensated for 42% of the carbon loss in land conversion. Our findings provide valuable information for regional carbon management in the SUS: (1) it is preferable to preserve pre-urban carbon pools than to rely on the carbon sinks in urban ecosystems to compensate for the carbon loss in land conversion. (2) In forested areas, it is recommendable to improve landscape design (e.g., by arranging green spaces close to the city center) to maximize the urbanization-induced environmental change effect on carbon sequestration. Urbanization-induced environmental change will be less effective in shrubland regions. (3) Urban carbon sequestration can be significantly improved through changes in management practices, such as increased irrigation and fertilizer and targeted use of vehicles and machinery with least-associated carbon emissions.

Manganese (III) Salen Supported Onto Hydrous Zirconia: Synthesis, Characterization, and Solvent Free Aerobic Oxidation of Styrene

Solid catalysts comprising manganese salen and hydrous zirconia were synthesized and characterized, and catalytic activity was evaluated by carrying out solvent-free liquid phase aerobic oxidation of styrene. As solid catalysts show high conversion of styrene with good selectivity toward benzaldehyde and styrene epoxide. The recovery of the catalyst was readily accomplished by simple filtration. The recycled catalyst can be used up to four cycles without any loss in conversion as well as selectivity.

Modified Montmorillonite clay catalyzed regioselective ring opening of epoxide with amines and alcohols under solvent free conditions

Modification of Montmorillonite by acid treatment depletes the layered structure and generates micro- and mesopores. The catalytic activity of naturally occurring Montmorillonite clay modified by acid treatment is reported for the reactions of epoxides with nucleophiles such as amines and alcohols at ambient temperature and solvent-free condition. The solid acid catalyst of the present study is reusable and exhibits significantly higher catalytic activities than known catalysts for the opening of the oxirane ring with nitrogen (aromatic as well as aliphatic amines) and oxygen (aromatic as well as aliphatic alcohols). A wide range of β-amino alcohols and β-alkoxy alcohols are synthesized with high epoxide conversion of excellent regioselectivity. The modified catalyst is recycled up to five times without significant loss in conversion and selectivity.

Selective Green Esterification and Oxidation of Glycerol over 12-Tungstophosphoric Acid Anchored to MCM-48

12-Tungstophosphoric acid anchored to mesoporous material (MCM-48) was synthesized and characterized by thermogravimetric–differential thermal analysis, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, 29Si nuclear magnetic resonance, X-ray diffraction, and transmission electron microscopy. The efficacy for the esterification of glycerol with acetic acid was investigated and 50% selectivity toward diacetyl and 30% for triaceyl glycerol was obtained under mild reaction conditions. The kinetic study was carried out, and it was found that esterification of glycerol follows first-order kinetics, and the rates are not mass transfer limited. As a cleaner alternative to traditional procedures, environmentally benign oxidation of glycerol was investigated with H2O2, and 40.5 and 33.6% selectivity for dihydroxyacetone and glyceraldehyde was obtained, respectively. The catalyst can be used up to four cycles without significant loss in conversion.

Fischer–Tropsch synthesis: Effect of catalyst particle (sieve) size range on activity, selectivity, and aging of a Pt promoted Co/Al2O3 catalyst

Abstract The effect of cobalt–alumina catalyst particle (sieve) size range on the performance of a traditional cobalt catalyst (platinum promoted cobalt/alumina) was investigated during Fischer–Tropsch synthesis (FTS) using a continuously stirred tank reactor (CSTR). In this study, the catalyst was sieved into four different size ranges: 20–63, 63–106, 106–180 and 180–355 μm. CO conversion varied with varying sieve size range under similar reaction conditions. With increasing catalyst sieve size, the CO conversion decreased, except for the smallest sieve size range (20–63 μm). These results are consistent with the view that, for the larger sieve size range, losses in CO conversion beyond catalyst aging may be explained by filling of the interior of the catalyst particle with heavy wax, thereby blocking available catalytically active sites. The adverse selectivities are directly the result of significant deactivation, since in FT synthesis, selectivity is a function of CO conversion. The loss in CO conversion for the 20–63 μm range catalyst was higher compared to the other three catalysts; due to the presence of heavy wax (Polywax 3000), the results suggest that the small particles tended to flocculate to larger clusters or were small enough to move at the speed of the liquid.

Synthesis and Characterization of Tungstophosphoric Acid/Pentaethylenehexamine/ZrSBA‐15 and Its Use in the Selective Oxidation of Benzyl Alcohol under Solvent‐Free Conditions

AbstractA layer‐by‐layer deposition strategy was employed for the immobilization of tungstophosphoric acid (HPW) onto a pentaethylenehexamine (PEHA)‐grafted ZrSBA‐15 framework to a give HPW/PEHA/ZrSBA‐15 composite. The resulting composite was characterized by XRD, SEM, TEM, FTIR, thermogravimetric analysis, N2 sorption, and X‐ray photoelectron spectroscopy, and these methods showed that the composite was stable in polar environments. These properties were attributed to the method of preparation, which ensured that a dense and stable array of HPW was encapsulated within the pores of PEHA‐modified ZrSBA‐15. In the H2O2‐mediated oxidation of benzyl alcohol, the 25 % HPW/PEHA/ZrSBA‐15 catalyst exhibited high selectivity (&gt;99 %) for benzaldehyde. Moreover, the oxidation reaction was performed under solvent‐free conditions, and the catalyst was recycled several times with negligible loss in selectivity and conversion. This HPW‐based catalyst was also efficient at selectively oxidizing other benzylic and alkyl alcohols to the corresponding aldehydes.

12-Tungstophosphoric acid supported on mesoporous molecular material: synthesis, characterization and performance in biodiesel production

Abstract 12-Tungstophosphoric acid (TPA) supported on mesoporous molecular material (Mobile Composition of Matter – MCM-48) was synthesized, characterized and its use as a heterogeneous catalyst was explored for biodiesel production via oleic acid esterification with methanol. The effect of various reaction parameters such as molar ratio, mass of catalyst, reaction time and reaction temperature was evaluated. The catalyst shows excellent activity (95% conversion) towards biodiesel production. The kinetic study revealed that the esterification of oleic acid follows the first order rate law with activation energy of 40.3 kJ mol−1. The catalyst was recyclable after simple regeneration without significant loss in conversion. The excellent catalytic activity over the present catalyst was extended to transesterification reaction for biodiesel production from waste cooking oil and jatropha oil, as low cost feedstock. The physicochemical properties of the produced biodiesel were further studied and the results show that the obtained properties are comparable with the ASTM specifications. Scale up procedure shows excellent conversions. A single step production procedure was also suggested for biodiesel production.

Investigation of Sawmill Management and Technology on Waste Reduction at Selected Sawmills in Moratuwa

The demand for sawn timber and wood-based products is rising steadily with newdevelopments in the country apart from the growing domestic consumption. Therefore it isimperative to strike a balance between the increasing demand and the optimum utilisation ofthe available forest resources.Thus the key objective of this study was to investigate the effects of sawmilling managementand technological parameters on loss in conversion from logs to sawn timber. A sample oftwenty one sawmills was selected out of 206 registered private sawmills in Moratuwaaccording to the sampling percentages determined from an initial survey. Based on the resultsmean percentage loss in conversion of private sawmills in Moratuwa was 56.9%. Significantdifferences were observed in loss in conversion values of both Teak and Mahogany speciesbetween the three categories of sawmills (frame sawmill, band sawmill and circular sawmill)as well as within the sawmills of the same category. Highest wastage was recorded in thecircular saw which was 64.4%. Percentage loss in conversion values were relatively low inframe saw and band saw which were 54.3% and 46.0% respectively. The results proved thatthe percentage loss in conversion varied between Teak and Mahogany species whereMahogany sawn in circular saw showed the highest percentage loss in conversion andMahogany sawn using the horizontal band saw showed the lowest percentage loss inconversion. The study further revealed that the loss in conversion values of private bandsawmills did not significantly vary with the State Timber Corporation band sawmills inKaldemulla.The reasons for variation in loss in conversion values can be attributed to sawyer’sexperience, the state of saw doctoring (saw sharpening and maintenance), cutting pattern,availability of log alignment equipments and saw guards and feed speed. It was observed thathigh wastage was caused by using thick tungsten carbide tipped blades used in circularsawmills. In contrast lowest loss in conversion was showed in band sawmills with thinflexible cutting blades. Through and through sawing method was found to be the only sawingmethod employed by all the selected sawmills. However it was identified that this methodcannot be recommended for all logs especially for defective logs. As a mix of sizes isproduced from a log in these sawmills cant sawing can be suggested as an efficient sawingmethod.

A green and sustainable approach for esterification of glycerol using 12-tungstophosphoric acid anchored to different supports: Kinetics and effect of support

Environmentally benign solid acid catalysts consisting of 12-tungstophosphoric anchored to MCM-41 and zirconia were synthesized and characterized. The efficacy for the esterification of glycerol, a value added byproduct from biodiesel production was investigated. Conditions for maximum conversion was optimized by varying different reaction parameters, such as, glycerol/acetic acid mole ratio, amount of the catalyst, reaction time and reaction temperature. The kinetic study was carried out, and it was found that esterification of glycerol follows first order kinetics and the rates are not mass transfer limited. Also activation energy and ΔG was determined. The difference in % conversion as well as selectivity was correlated with the nature of supports, value of activation energy as well as ΔG. The catalysts showed potential of being used as recyclable material after simple regeneration without significant loss in conversion.

Bifunctional Catalytic Activity of 12-Tungstophosphoric Acid Impregnated to Different Supports for Esterification and Oxidation of Benzyl Alcohol: A Comparative Study on Catalytic Activity and Kinetics

The bifunctional catalytic activity of 30% 12-tungstophosphoric acid impregnated to MCM-41 (TPA3/MCM-41) and zirconia (TPA3/ZrO2) was explored for acid catalysis as well as oxidation reactions. The effect of various reaction parameters such as molar ratio, amount of catalyst, time, and temperature was studied to optimize the conditions for maximum conversion. The catalysts show the potential of being used as recyclable catalytic materials after simple regeneration without significant loss in conversion. TPA3/MCM-41 shows high activity in terms of % conversion toward esterification as well as oxidation reaction as compared to that of TPA3/ZrO2. High catalytic activity of TPA3/MCM-41 may be due to its porosity and higher surface area as well as high total acidity.

EVALUATION OF THE SAWMILLING WASTAGE OF SAWMILLS IN WESTERN PROVINCE OF SRI LANKA

The main objective of this study is to find the amount of sawmilling wastage of popularsawn timber species used in the sawmills situated in the Western Province of Sri Lanka.Fifteen sawmills were selected out of 345 registered sawmills in the western province byusing a random sampling method. The selected sawmills represent all types of sawmillmachinery available in Sri Lanka, (Horizontal band saws, vertical band saws, circular sawsand frame saws). Twelve common timber species were also selected. One hundred andsixty five logs representing the selected twelve species were measured and sawn at theselected fifteen sawmills. For each log, length and under bark mid girth were measured tocalculate log volume. Sawn timber produced from each log was also measured and volumewas calculated. Percentage loss in conversion was calculated.The percentage loss in conversion of sawmills in Western Province is 55.7%. Percentageloss in conversion varies with the type of sawing machine. The most wasteful machine isthe inserted tooth circular saw (percentage loss in conversion is (54.1 %). Percentage lossin conversion values are respectively lower in circular saw (53.2%), vertical band saw(47.8%), horizontal band saw (44.4%) and horizontal frame saw (42.4%).Percentage loss in conversion of the selected 12 timber species varied; jak when sawnusing a circular saw gave the highest percentage loss in conversion (60.8%), followed byAlbizia when sawn using inserted tooth circular saw (59.2%). Mahogany when sawnusing a horizontal band saw, showed the lowest percentage loss in conversion (33.6%).Saw gauge does not significantly affect the loss in conversion.The value of the sawmill machines is Rs.250,000/ and up. The value of the raw materialsshows wide variation: log price Rs.60 per cu.ft.(rubber) to Rs.550 per Cu.ft.(Teak). Mostsawmills cannot work throughout the year due to lack of raw materials and financialproblems. Generally workers are hired on daily paid basis and their salaries vary from Rs.150 to Rs.350 per day which depends on the timber species, machinery used and endproducts (Rs. 25 per.cu.ft. to Rs.40 per cu.ft.).Major causes for wastage can be attributed to technological problems such as adopting athrough and through sawing method to produce the widest boards, rather than sawing toproduce a mix of sizes, use of bad sawing practices such as poor log alignment andimproper log turning, use of low gauge wide diameter saws to cut small diameter logswhich could be converted by small diameter high gauge saws, inefficient and inadequatesaw maintenance (saw doctoring) and use of out-dated machinery. Improper buckingpractices at the logging sites, log defects and inefficient sawmill management are the otherfactors which cause higher wastage.

Analyses of entropy generation and heat entransy loss in heat transfer and heat-work conversion

Heat entransy loss is defined and both the concepts of entropy generation and heat entransy loss are applied to the analyses of heat-work conversion and heat transfer processes in this paper. In heat-work conversion, it is found that the minimum entropy generation rate relates to the maximum output power under the conditions of the prescribed heat absorption and the equivalent thermodynamic forces corresponding to the heat absorption and release of the system, while the maximum heat entransy loss relates to the maximum output power under the conditions of the prescribed heat absorption and the equivalent temperatures corresponding to the heat absorption and release of the system. In heat transfer, the maximum entropy generation rate is consistent with the maximum heat transfer rate with prescribed equivalent thermodynamic force difference, while the minimum entropy generation rate corresponds to the minimum equivalent thermodynamic force difference with prescribed heat transfer rate. Furthermore, when the concept of heat entransy loss is used, the maximum heat entransy loss rate corresponds to the maximum heat transfer rate with prescribed equivalent temperature difference, while the minimum heat entransy loss rate corresponds to the minimum equivalent temperature difference with prescribed heat transfer rate. The numerical results of some examples verify the theoretical analyses.

Minimization of U-232 content in advanced high-conversion multirecycling thorium reactors by blanket fragmentation

The handling of recovered Th-232 is perhaps the most important problem in thorium breeder reactors due to the presence of the undesirable nuclide U-232 and its daughter Th-228. In advanced multirecycling reactors with high conversion ratios, the amount of this nuclide might reach 5000 ppm after several rounds of recycling, an amount that is almost 50-fold higher than that in conventional PWRs resulting in very high remote reprocessing costs. A reduction of U-232 via a reduction of the fast neutrons available for the (n,2n) reaction by increasing the moderator is not a feasible option in advanced reactors because of the loss in conversion. In this paper the possibility to minimize U-232 by blanket fragmentation while maintaining both the fuel-to-volume moderator volume ratio and amount of material is analyzed. The result show that reductions of up to 10% are feasible with an associated -reduction of the reprocessing cost.

Symmetrical and unsymmetrical Brønsted acidic ionic liquids for the effective conversion of fructose to 5-hydroxymethyl furfural

Symmetrical and unsymmetrical Bronsted acidic Ionic Liquids (ILs) have been synthesized via a one-pot halogen-free route and characterized by TGA-DTA and DSC to compare their stability and activity. The acidities of the four ILs have also been tested by the Hammett method. These ILs were utilised as catalysts for the dehydration of fructose to 5-hydroxymethylfurfural (HMF) in the presence of dimethylsulphoxide (DMSO) as solvent. The effects of reaction time, temperature and catalyst concentration were studied. The ILs are very efficient for the reaction at relatively lower temperature with very good HMF yield and selectivities. The used ILs could be easily recycled without any significant loss in fructose conversion and HMF yield.

A New Maximum Power Point Tracking Control Scheme in Photovoltaic Systems for Energy Saving

Maximum power point tracking (MPPT) control could significantly increase the overall reliability and conversion efficiency of grid-connected photovoltaic (PV) systems, so it can reduce energy loss in the photoelectric conversion. In this paper, a new MPPT (Zero Average Incremental Conductance) control algorithm is proposed. This method has the advantages of traditional IncCond MPPT. Moreover, it is stable against interference and not sensitive to system models. Therefore the proposed algorithm could be available and widely used in practical MPPT systems. A 200W grid-connected PV system prototype is built in lab. Experiment results verify the effectiveness of the proposed MPPT method.