Propylene Research Articles

Effect of gas composition on the performance and emissions of a dual-fuel diesel-natural gas engine at low load conditions

Areas located at or near natural gas (NG) well or storage sites can use NG to partially or totally replace the diesel fuel used to power equipment or for local transportation. This study investigated a dual-fuel diesel-NG engine operating at low load conditions, as literature shows that such conditions are the most sensitive to NG composition. Part of the diesel fuel was replaced with four different gas blends containing methane, ethane, and propane. No EGR was employed to avoid it interfering with the individual fuel component evaluation. Results show up to 80% higher rates of pressure rise compared to the diesel baseline, which limited the diesel substitution rate to 40% without EGR. While pure methane affected the most the diesel fuel vaporization and ignition delay, important differences were seen during the late-stage fuel oxidation. The location and magnitude of the 2nd heat release peak changed with gas composition, with propane gas mixtures showing the largest and most advanced peak. In-cylinder pressure correlated with the gas mixture’ autoignition temperature. As a result, the mixtures with propane had the best performance and gaseous fuel oxidation, with opposite results for the methane-only gas. As propane gas mixtures performed better than mixtures with ethane, it suggests maintaining a higher propane fraction in the NG for dual-fuel operation. CO2 and NOx emissions reduced up to 6.8% and 20%, respectively. However, the reduction was offset by the large increase in CO and HC emissions, which could require after-treatment modifications. Finally, the results suggest that the switch from diesel only to low-load dual-fuel operation can be performed without major modifications in terms of engine control and aftertreatment changes, at least for the low load conditions and NG compositions used here.

Evaluating the Energy Efficiency and Environmental Impact of COVID-19 Vaccines Coolers through New Optimization Indexes: Comparison between Refrigeration Systems Using HFC or Natural Refrigerants

COVID-19 vaccines are used worldwide to promote immunity and, in that sense, vaccination is a step forward toward ending the pandemic. Nevertheless, current vaccines must be ultra-cold or cold-stored. Vaccine coolers’ energy demand and greenhouse gas emissions lead to a significant environmental impact. This article predicts the environmental and energy impacts of some COVID-19 vaccines: Moderna, Janssen, CoronaVac, Pfizer, AstraZeneca–Oxford–Covishield, and Sputnik V, in terms of carbon dioxide emissions using a new approach for the TEWI (Total Equivalent Warming Impact) methodology, with several options of refrigerants from halogenated to natural fluids such as propane, which is natural gas with low GWP (global warming potential). Through the application of new optimization indexes, it is concluded that the evaporation temperature of the refrigerant gas has a great influence on the sizing of the coolers. For example, for the same number of vaccines, the thermal load of Pfizer is more than double that of AstraZeneca–Covishield, CoronaVac, or Janssen, while the direct environmental impact is seven times greater. Another relevant factor is the choice of refrigerant. For example, the greenhouse effect varies greatly for the same brand of vaccine. The Moderna vaccine’s global warming potential (GWP) is 776 times higher using R-449A gas than using R-290 (propane gas). In Brazil, the refrigerators used to store the Pfizer vaccine have a total TEWI almost two times higher than the total TEWI of refrigerators using propane to store the Janssen vaccine. At this time of the pandemic, these optimization indexes can be used to support important decisions regarding the future selection of vaccine brands considering the energy consumption and environmental impact required for their storage.

A stochastic approach to evaluating the economic impact of disruptions in feedstock pipelines on downstream production

Reliability of feedstock supply is an important consideration for enhancing the safety and continuous operation of chemical plants. A critical component of the chemical and refining sectors is the extensive pipeline network which transports natural gas and hydrocarbon liquids from producing areas to refineries and chemical plants. Incidents involving spills or releases and shutdowns of those pipeline can occur due to a number of causes including corrosion, equipment malfunction, and excavation damage. These incidents involve economic, environmental, and safety consequences such as the cost of asset damage, lost commodities, cleanup requirement, and operational disruption. In this work, an appropriately developed stochastic framework is presented to determine the disruption impact of pipeline incidents on downstream chemical production. Incident data are statistically analyzed to determine meaningful distributions for incident rates, spill/release quantities, and pipeline shutdown durations. A case study on the production of propylene via three different pathways (crude oil, propane, and natural gas) is presented to illustrate the methodology and underline the variability of the process production impact due to variations in risk occurrence characteristics. Using specific process chemistry and mass balances, more precise risk profiles for the product shortfall and cost of lost sales can be generated.

A drug-discovery-oriented non-invasive protocol for protein crystal cryoprotection by dehydration, with application for crystallization screening.

In X-ray macromolecular crystallography, cryoprotection of crystals mounted on harvesting loops is achieved when the water in the sample solvent transitions to vitreous ice before crystalline ice forms. This is achieved by rapid cooling in liquid nitro-gen or propane. Protocols for protein crystal cryoprotection are based on either increasing the environmental pressure or reducing the water fraction in the solvent. This study presents a new protocol for cryoprotecting crystals. It is based on vapour diffusion dehydration of the crystal drop to reduce the water fraction in the solvent by adding a highly concentrated salt solution, 13 M potassium formate (KF13), directly to the reservoir. Several salt solutions were screened to identify KF13 as optimal. Cryoprotection using the KF13 protocol is non-invasive to the crystal, high throughput and easy to implement, can benefit diffraction resolution and ligand binding, and is very useful in cases with high redundancy such as drug-discovery projects which use very large compound or fragment libraries. An application of KF13 to discover new crystal hits from clear drops of equilibrated crystallization screening plates is also shown.

Merging Carbonyl Addition with Photocatalysis.

The carbonyl group stands as a fundamental scaffold and plays a ubiquitous role in synthetically important chemical reactions in both academic and industrial contexts. Venerable transformations, including the aldol reaction, Grignard reaction, Wittig reaction, and Nozaki-Hiyama-Kishi reaction, constitute a vast and empowering synthetic arsenal. Notwithstanding, two-electron mechanisms inherently confine the breadth of accessible reactivity and topological patterns.Fostered by the rapid development of photoredox catalysis, combing well-entrenched carbonyl addition and radicals can harness several unique and increasingly sustainable transformations. In particular, unusual carbon-carbon and carbon-heteroatom disconnections, which are out of reach of two-electron carbonyl chemistry, can be conceived. To meet this end, a novel strategy toward the utilization of simple carbonyl compounds as intermolecular radical acceptors was developed. The reaction is enabled by visible-light photoredox-initiated hole catalysis. In situ Brønsted acid activation of the carbonyl moiety prevents β-scission from occurring. Furthermore, this regioselective alkyl radical addition reaction obviates the use of metals, ligands, or additives, thus offering a high degree of atom economy under mild conditions. On the basis of the same concept and the work of Schindler and co-workers, carbonyl-olefin cross-metathesis, induced by visible light, has also been achieved, leveraging a radical Prins-elimination sequence.Recently, dual chromium and photoredox catalysis has been developed by us and Kanai, offering a complementary approach to the revered Nozaki-Hiyama-Kishi reaction. Leveraging the intertwined synergy between light and metal, several radical-to-polar crossover transformations toward eminent molecular motifs have been developed. Reactions such as the redox-neutral allylation of aldehydes and radical carbonyl alkylation can harvest the power of light and enable the use of catalytic chromium metal. Overall, exquisite levels of diastereoselectivity can be enforced via highly compact transition states. Other examples, such as the dialkylation of 1,3-dienes and radical carbonyl propargylation portray the versatile combination of radicals and carbonyl addition in multicomponent coupling endeavors. Highly valuable motifs, which commonly occur in complex drug and natural product architectures, can now be accessed in a single operational step. Going beyond carbonyl addition, seminal contributions from Fagnoni and MacMillan preconized photocatalytic HAT-based acyl radical formation as a key aldehyde valorization strategy. Our group articulated this concept, leveraging carboxy radicals as hydrogen atom abstractors in high regio- and chemoselective carbonyl alkynylation and aldehyde trifluoromethylthiolation.This Account, in addition to the narrative of our group and others' contributions at the interface between carbonyl addition and radical-based photochemistry, aims to provide core guiding foundations toward novel disruptive synthetic developments. We envisage that extending radical-to-polar crossovers beyond Nozaki-Hiyama-Kishi manifolds, taming less-activated carbonyls, leveraging multicomponent processes, and merging single electron steps with energy-transfer events will propel eminent breakthroughs in the near future.

Mathematical model for describing the influence of initial pressure on the flammability limits of light hydrocarbons at subatmospheric pressures

Fuel in aircraft fuel tanks, as well as some industrial processes, are under conditions of reduced pressure. However, few models have been proposed for estimating the influence of the initial pressure on flammability limits at subatmospheric pressures. A model to describe this influence was derived in this study according to the assumption that the heat release rate is equal to the heat loss rate. Several assumptions used in the model simplification process were verified to accord with real situations. The experimental data on seven gaseous fuels, namely methane, ethane, ethylene, propane, propylene, n-butane, and n-butylene, were analysed to validate the proposed model. In general, the simulation results accord well with the data on flammability limits measured at subatmospheric pressures. In its extension to systems functioning at elevated pressures, the proposed model accurately estimated the lower flammability limit data for atmospheric pressures up to 30 MPa and the upper flammability limit (UFL) for atmospheric pressures from 0.1 to 0.9 MPa. However, large deviations were noted between the estimated and actual UFLs for atmospheric pressures from 0.1 to 24.9 MPa. Nevertheless, the proposed model accurately describes the variation trends of flammability limits over a wide pressure range.

Benchmark study of combustion model of premixed gas by using LBM

The propane gas combustion in a combustor was calculated using a two-dimensional LBMmethod that used pressure, temperature, and the distribution function fp of chemicalcomponents: fT, fC3H8, fO2, fCO2, fN2, and fH2O. WOLFRAM MATHEMATICA was used inthe calculation and three cases were calculated Case1: one dimension combustion flameof a uniform mixed gas (Re = 124) to obtain an average reaction rate omega; Case2: A twodimensional problem, without the influx, where ignition occurred in the center of the area; and Case3: calculate the combustion of the air-fuel mixture from fuel jets ejected from both upper and lower boundary. The flow field simulation area in the axial symmetry was 1/4. The shape of the flame front consisted of a curved surface, and then a nearly horizontal flame front was formed at the end of the simulation. For the one-dimensional case, the propagation speed was 0.25m/sec, which was larger than the results reported by Huidan Yue [9]. The flame propagation speed roughly matched that of the two-dimensional simulation by Yamamoto.

Synthesis and Application of β‐Alkynyl‐γ,γ‐Difluoroallylboronates for Metal‐Free Allylation of Aldehydes in Water

Abstractβ‐Alkynyl substituted γ,γ‐difluoroallyl‐boronates were prepared via defluorination under basic condition. Allylation reaction of aldehydes with gem‐difluoroallylboronates under metal‐free condition in water was developed. As the sole solvent, water dramatically improved the efficiency of the reaction, and afforded the desired products in 48–92% yields. The corresponding difluorinated alcohols were smoothly transformed into the 3,3‐difluoro‐4‐methylene‐3,4‐dihydro‐2H‐pyran derivatives in the presence of gold catalyst.magnified image

Kinetic Investigation of Propane Gas Hydrate Formation by Tracking Particle Size Evolution in the Presence of THF

Kinetic Investigation of Propane Gas Hydrate Formation by Tracking Particle Size Evolution in the Presence of THF

Metabolic Investigation on the Interaction Mechanism between Dietary Dihydrochalcone Intake and Lipid Peroxidation Product Acrolein Reduction.

Acrolein (ACR), a lipid peroxidation product, pathologically participates in various chronic diseases. In vitro evidence suggestes that dietary dihydrochalcones (DHCs) potentiate safe and alternative therapeutics to synthetic pharmaceuticals for ACR scavenging. Here, to investigate whether ingested DHCs could trap ACR and thereof result in reductions in endogenous ACR in mice is aimed. Three doses of phloretin (25, 100, and 400mgkg-1 ), a major dietary DHC, are orally administrated to mice and 24h urine and fecal samples are collected, respectively. High-resolution MS-based targeted metabolomics reveal for the first time that phloretin and its oxidized metabolite are able to trap endogenous ACR via formation of ACR conjugates. Quantification further demonstrate that a) more than 13% of ingested phloretin can dose-dependently trap 0.77-9.92nmol of ACR within 24h; b) phloretin ingestion leads to marked reductions in both free ACR and ACR metabolites in mouse urine compared to control; and c) trapping reactions by phloretin can account for up to 20.1% of the total decreases in endogenous ACR, depending on the administration doses. Findings from this study indicate that regular consumption of DHCs-rich diets holds great promise to alleviate the development of ACR-associated chronic diseases.

Bispalladacycle Catalyzed Nucleophilic Enantioselective Allylation of Aldehydes by Allylstannanes

AbstractEnantiopure homoallylic secondary alcohols are very important synthetic building due to the versatility of the hydroxyl and olefin moieties. A key strategy to prepare them is by nucleophilic allylation of aldehydes. A large number of catalyst concepts emerged that allow for high enantioselectivity. Still, in many target‐oriented syntheses of complex structures stoichiometric methods are preferred over catalytic ones. The need for high catalyst loadings and long reaction times, plus unsatisfying reproducibility and substrate scopes are reasons for that. In the present study we report the first palladium catalysts capable of controlling asymmetric nucleophilic allylations of aldehydes with allyltributyltin. TONs up to 620 were achieved, which is significantly higher than for any other reported catalyst. The method is also tolerating electronically and sterically unfavorable substrates. We show that a transmetallation occurs, favoring an η1‐allyl coordination mode with the bispalladacycles. In contrast, for the corresponding monopalladacycle an unproductive η3 coordination is dominant.

Review: Cinque viaggi (1990–98), by Guido Guidi

Review: <i>Cinque viaggi (1990–98)</i>, by Guido Guidi

Heat transfer and wetting behaviour of falling liquid films in inclined tubes with structured surfaces

This study examines wetting behaviour and evaporation heat transfer of a falling liquid film inside a circular tube carrying grooves at its internal surface. The experiments include five different structures (four helical, one longitudinal) and one smooth tube (Cu, d i ≈ 27 mm ) with counter-current flow of liquid (downwards) and vapour (upwards). Results are obtained for liquid propane films ( P r = 2 . 79 , R e smooth tube = 160 − 645 ) at different twisting angles and height of the grooves, tube inclination angles ( β = 0° − 20° from the vertical), mass flow rates (from 5 kg/h up to 20 kg/h) and driving temperature differences (2 K, 3 K and 4 K) mainly at a film inlet temperature of 293.15 K. For wetting behaviour investigations the liquid film is visually observed at the lower end of the tube. The experiments reveal that the internal structures used lead to a strong improvement in both wetting behaviour and heat transfer, even up to inclination angles of 20° . The amount of capillary transported liquid within the grooves coupled with groove geometry itself are the main impacts on wetting behaviour and will be discussed within this paper. • Helically twisted structures resulting better wetting and heat transfer. • Greater groove mass flow rate supportive for greater heat transfer. • High aspect ratios supportive for high heat transfer. • Driving temperature difference influences wetting and heat transfer. • Small inclination with small influence on heat transfer.

Rh-Catalyzed Coupling of Aldehydes with Allylboronates Enables Facile Access to Ketones.

We present herein a novel strategy for the preparation of ketones from aldehydes and allylic boronic esters. This reaction involves the allylation of aldehydes with allylic boronic esters and the Rh-catalyzed chain-walking of homoallylic alcohols. The key to this successful development is the protodeboronation of alkenyl borylether intermediate via a tetravalent borate anion species in the presence of KHF2 and MeOH. This approach features mild reaction conditions, broad substrate scope, and excellent functional group tolerance. Mechanistic studies also supported that the tandem allylation and chain-walking process were involved.

An experimental study on the intermittent flame ejecting behavior and critical excess heat release rate of carriage fires in tunnels with longitudinal ventilation

This paper describes the quantitative study on the effects of tunnel longitudinal ventilation velocities on the critical excess heat release rate and intermittent flame ejecting behaviors of carriage fires. Experiments were carried out in a 1/8 model tunnel with the dimensions of 22 m × 1.2 m × 0.8 m (length × width × height). 442 repeatable test conditions contained gas fuel (propane) and solid fuel (corrugated paperboard), including variations on fuel supply rates, tunnel opening sizes, and longitudinal ventilation velocities. The intermittent flame ejecting behaviors were expressed as the flame ejection probability in carriage fires, which was characterized by image statistical processing. The results showed that the flame ejection probability was positively correlated with the fire heat release rate, but it was negatively correlated with the ventilation factors of carriage opening and longitudinal ventilation velocities. New non-dimensional correlations between the critical excess heat release rate and the longitudinal ventilation velocities are proposed. Moreover, a piecewise equation is proposed to describe flame ejection probability that is affected by longitudinal ventilation velocities for the first time. All the proposed correlations are found to fit well with the experimental data, which established an essential foundation to quantify the critical heat release rate and intermittent flame ejecting behaviors of carriage fire in various longitudinal ventilation velocities. Finally, the some limitations of propane gas fuel are analyzed. Moreover, this paper depicted the flame ejecting behaviors induced by gas fuel and solid fuel, and reveal the difference and relationship between them.

Recent Progress in Chromium-Mediated Carbonyl Addition Reactions

AbstractOrganochromium(III) species are versatile nucleophiles in complex molecule synthesis due to their high functional group tolerance and chemoselectivity for aldehydes. Traditionally, carbonyl addition reactions of organochromium(III) species were performed through reduction of organohalides either using stoichiometric chromium(II) salts or catalytic chromium salts in the presence of stoichiometric reductants [such as Mn(0)]. Recently, alternative methods emerged involving organoradical formation from readily available starting materials (e.g., N-hydroxyphthalimide esters, alkenes, and alkanes), followed by trapping the radical with stoichiometric or catalytic chromium(II) salts. Such methods, especially using catalytic chromium(II) salts, will lead to the development of sustainable chemical processes minimizing salt wastes and number of synthetic steps. In this review, methods for generation of organochromium(III) species for addition reactions to carbonyl compounds, classified by nucleophiles are described.1 Introduction2 Alkylation2.1 Branch-Selective Reductive Alkylation of Aldehydes Using Unactivated Alkenes2.2 Linear-Selective Alkylation of Aldehydes2.2.1 Catalytic Decarboxylative Alkylation of Aldehydes Using NHPI ­Esters2.2.2 Catalytic Reductive Alkylation of Aldehydes Using Unactivated Alkenes2.2.3 Alkylation of Aldehydes via C(sp3)–H Bond Functionalization of Unactivated Alkanes2.3 Catalytic α-Aminoalkylation of Carbonyl Compounds3 Allylation3.1 Catalytic Allylation of Aldehydes via Three-Component Coupling3.2 Catalytic Allylation of Aldehydes via C(sp3)–H Bond Functionalization of Alkenes4 Propargylation: Catalytic Propargylation of Aldehydes via Three-Component Coupling5 Conclusion

Effects of Low-Cost Repair Techniques on Restoration of Mechanical Properties of Fire-Damaged Concrete

Researchers have conducted numerous investigations on various repair techniques to restore the mechanical properties of fire-damaged concrete. However, most of the techniques are either expensive or require high technical skills. As a continuous work, this study involved an experimental investigation of the effects of various low-cost repair techniques to restore the mechanical properties of fire-damaged concrete. Sixty cylindrical concrete samples were subjected to heat ranging from 400°C to 800°C in a propane gas furnace. The samples were categorized into six groups, including the following: undamaged, fire-damaged, and fire-damaged and repaired using water curing; fire-damaged and repaired using cement-based slurry injection; re-curing fire-damaged and repaired with steel wire mesh along with epoxy resin wrapping; and fire-damaged and repaired using epoxy injection. The samples were tested for non-destructive and destructive tests, including ultrasonic pulse velocity, rebound hammer, and compressive strength. The results showed that the use of cement-based slurry injection along with the water-curing repair technique could regain almost 90% of its ultimate strength and secant stiffness, making it the most effective low-cost repair technique for fire-damaged concrete exposed up to 700°C.

Nickel‐Mediated Enantioselective Photoredox Allylation of Aldehydes with Visible Light

AbstractHere we report a practical, highly enantioselective photoredox allylation of aldehydes mediated by chiral nickel complexes with commercially available allyl acetate as the allylating agent. The methodology allows the clean stereoselective allylation of aldehydes in good to excellent yields and up to 93 % e.e. using a catalytic amount of NiCl2(glyme) in the presence of the chiral aminoindanol‐derived bis(oxazoline) as the chiral ligand. The photoredox system is constituted by the organic dye 3DPAFIPN and a Hantzsch's ester as the sacrificial reductant. The reaction proceeds under visible‐light irradiation (blue LEDs, 456 nm) at 8–12 °C. Compared to other published procedures, no metal reductants (such as Zn or Mn), additives (e.g. CuI) or air‐sensitive Ni(COD)2 are necessary for this reaction. Accurate DFT calculations and photophysical experiments have clarified the mechanistic picture of this stereoselective allylation reaction.

Nickel-Mediated Enantioselective Photoredox Allylation of Aldehydes with Visible Light.

Here we report a practical, highly enantioselective photoredox allylation of aldehydes mediated by chiral nickel complexes with commercially available allyl acetate as the allylating agent. The methodology allows the clean stereoselective allylation of aldehydes in good to excellent yields and up to 93 % e.e. using a catalytic amount of NiCl2 (glyme) in the presence of the chiral aminoindanol-derived bis(oxazoline) as the chiral ligand. The photoredox system is constituted by the organic dye 3DPAFIPN and a Hantzsch's ester as the sacrificial reductant. The reaction proceeds under visible-light irradiation (blue LEDs, 456 nm) at 8-12 °C. Compared to other published procedures, no metal reductants (such as Zn or Mn), additives (e.g. CuI) or air-sensitive Ni(COD)2 are necessary for this reaction. Accurate DFT calculations and photophysical experiments have clarified the mechanistic picture of this stereoselective allylation reaction.

Rheology investigation of propane gas hydrate crystallization in water/asphaltene-resin-wax deposit emulsions

Hydrates and asphaltene-resin-wax deposits are increasingly concerned as a terrible problem in the field of offshore oil and gas production and transportation. The rheological property of propane gas hydrate in the water-in-asphaltene-resin-wax deposit (W/ARWD) emulsion was in situ characterized by experiments in a stress-controlled rheometer with particular focus on the effects of pressure, emulsion component ratio, and deposit composition. Results demonstrated that the higher pressure could accelerate hydrate formation and aggregation in a shorter time, and exhibit more obvious shear-thinning behavior of hydrate slurry. The emulsion component ratio was positive correlation with the hydrate slurry viscosity and the yield stress, was negative correlation with the hydrate crystallization time. Asphaltene and wax occupied more nucleation sites on water droplets and formed physical barriers to hinder the hydrate crystallization. The promoting effect of resin on hydrate crystallization was stronger than inhibiting effect. With the increase of asphaltene, resin, and wax contents, the yield stress of hydrate slurry gradually increased, and the effect of wax on the yield stress was stronger than asphaltene and resin, which was associated with the multiple effects of capillary bridge between hydrate particles and spatial network of wax crystals. Furthermore, the coupling effect of pressure, emulsion component ratio, and deposit composition on the rheological properties of hydrate slurry had been studied. This study is significant in that it can helpfully support the development of subsea multiphase flow assurance in petroleum production.