Increase In Aromatic Content Research Articles

Green preparation of poly (butylene succinate-co-butylene terephthalate) foam with tunable degradability and mechanical properties by supercritical CO2

Poly (butylene succinate-butylene terephthalate) (PBST) with different chain segments was synthesized by in-situ polycondensation, and foams were prepared by supercritical CO2 foaming. The crystallinity and tensile modulus of PBST increases with the aromatic content, slowing down the diffusion of CO2 and enhancing the dimensional stability of PBST foam. The rheological analysis reveals that a higher temperature of PBST modulus platform is correlated with a higher aromatic content, which is more conducive to the cell stability. The foaming temperature window is 60 - 80 °C at 30% aromatic content, which moves to 160 - 175 °C at 70% aromatic content, and the maximum expansion ratio of PBST foam decreases from 40.7 to 9.8. With the increase of aromatic content from 30% to 70%, there is an obvious improvement in the compressive modulus of PBST foam, from 0.92 MPa to 6.65 MPa, accompanied by a reduction in the weight loss rate of degradation decreased from 10.78% to 3.04% in 10 days. Hence, there is a careful balance between degradability and foamability of PBST foams. Introducing a suitable aromatic content obtained higher strength to improve the cell stability on the premise that the strong degradability can be maintained, which provides an effective strategy to prepare PBST foams with good degradability and favorable mechanical properties.

Thermodynamic Insights into Sustainable Aviation Fuel Synthesis via CO/CO2 Hydrogenation

The transformation of CO/CO2 hydrogenation into high-density sustainable aviation fuel (SAF) represents a promising pathway for carbon emission reduction in the aviation industry but also serves as a method for renewable energy assimilation. However, current hydrocarbon products synthesized through CO/CO2 often focus on various catalytic paths with high selectivity and high conversion rates rather than the synthesis of SAFs with complex components. This study undertakes a thermodynamic investigation into the direct or indirect synthesis of SAFs from CO/CO2 hydrogenation. By analyzing the synthesis of seven aviation fuels defined by the American Society for Testing and Materials (ASTM) D7566 standard, our study reveals a temperature-dependent reduction in the reaction driving force for all products. Specifically, for CO, ΔG transitions from approximately −88.6 J/(mol·K) at 50 °C to 26.7 J/(mol·K) at 500 °C, with the switch from negative to positive values occurring around 390 °C. Similarly, for CO2, ΔG values change from approximately −66.7 J/(mol·K) at 50 °C to 37.3 J/(mol·K) at 500 °C, with the transition point around 330 °C. The thermodynamic favorability for various hydrocarbon products synthesized is also examined, highlighting a transition at temperatures of around 250 °C, beyond which the thermodynamic drive for the synthesis of aromatic compounds increasingly surpasses that of cycloparaffin synthesis. Our findings also underscore that the products with a higher aromatic content yield a lower H2/CO2 ratio, thus reducing hydrogen consumption. The influence of cycloparaffin and aromatic proportions in the typical SAF products on the ΔG is also explored, revealing that an increase in cycloparaffin content in SAFs slightly elevates the ΔG, whereas an increase in aromatic content significantly reduces ΔG, thereby markedly enhancing the thermodynamic drive of the CO/CO2 hydrogenation reaction. These findings underscore the thermodynamic preference for synthesizing SAF with a higher proportion of aromatic compounds, shedding light on potential pathways for optimizing fuel synthesis to improve efficiency. Finally, the thermodynamic challenges and potential solutions involved in synthesizing SAFs via specific intermediate compounds are discussed, presenting opportunities for more strategic process schemes in industrial scenarios.

Hydrothermal carbon spheres produced from glucose, cyclodextrin, and starch

The production of hydrothermal carbons from glucose, cyclodextrin, and starch was reported at 180 °C and 200 °C for 24 hr, both with and without 2-chloro propionic acid. The yields of hydrothermal carbons varied depending on the feedstock and temperature. At the lowest temperature, glucose gave the highest yield of hydrochar, while at 200 °C, the yields did not differ significantly among the three feedstocks, with the highest yield obtained for cyclodextrin-derived hydrochars. The use of a catalyst not only decreased the yield of hydrothermal carbons but also resulted in an increase in the diameter of hydrochars for all saccharides. When compared to raw saccharides, the O/C and H/C ratios of hydrothermal carbons were significantly lower, suggesting that significant deoxygenation and dehydration occurred after the HTC processing. In the non-catalytic runs, hydrochars for each feedstock showed an increase in aromatic content when the temperature was increased from 180 °C to 200 °C. The size of the carbon spheres was significantly influenced by various factors including the operating conditions, the type of saccharide used, and the pH of the aqueous solutions. The diameters of carbon spheres produced in runs with catalysts were larger when compared to their corresponding hydrothermal carbons from the non-catalyst runs.

Aromatic dialdehyde-based bisbenzoxazines: The influence of relative position of oxazine rings

Polybenzoxazines are known to have superior thermal stability. Especially, the use of aromatic aldehydes instead of formaldehyde for the synthesis of benzoxazines monomers could improve this stability. However, the increase in aromatic content of the monomer can prevent the processability. The objective of this article is to understand the relationships between the conformation of an aromatic dialdehyde and its thermal properties. Two benzoxazine monomers were synthesized, based on salicylaldehyde, furfurylamine and respectively terephthalaldehyde (TPA, para configuration) and isophthalaldehyde (IPA, meta). Structural characterizations showed differences in intramolecular interactions between the two isomers. The melting transition of “meta” isomer was 50 °C lower than for “para” monomer, whereas polymerization temperatures and enthalpies were nearly the same. Volatile compounds released during the polymerization were the same in both cases, as investigated by mass spectrometry (Py-GC/MS). Curing kinetics using model-free kinetic methods revealed that the E-dependency follows the same trend for both monomers. Finally, thermal degradation monitored by thermogravimetric analysis under inert atmosphere was similar, with high degradation temperatures and high char yields (64%).

Effects of gasoline composition on engine performance, exhaust gases and operational costs

New technologies to improve the performance and efficiency of internal combustion engines are related to enhance knock resistance in fuels. Aromatics, Paraffins and Lead-based additives in gasoline are used to increase octane rating, but some of these are toxic, carcinogenic or expensive. Nowadays, several alternatives for octane boosting is considered and oxygenated compounds are attracting interest, as ethanol. This compound is a renewable energy source, which can reduce the oil dependence and also can be appropriately used in gasolines as a blend. Ethanol use, widely noticed in Brazil and United States, increase octane rating, thermal efficiency and engine power due to the charge cooling effect and molar expansion capacity. For the same engine and operation conditions, octane rating and engine performance are directly correlated. The present study discusses about the influence of gasoline blend composition on the engine performance by the combustion process analysis. For this, samples of gasoline blends with different RON numbers were experimentally evaluated on a single cylinder research engine in high load and speed conditions. These conditions were selected as they are potential operation points for knock occurrence. The results show that despite the increase in aromatic content of gasoline samples and consequently the improvements in octane rating and engine performance, it is not compensated by the cost. For instance, the use of gasoline blend with higher ethanol percentage, resulted in reduction of more than 23% in net power (kW) cost and up to 32% of NOx specific emission.

Thermal and catalytic cracking of whole crude oils at high severity

The catalytic and thermal cracking of three types of whole crude oils, having API gravity at 34° (AL), 39° (AXL) and 51° (ASL), were investigated via a fixed-bed micro-activity test (MAT) unit at high temperature between 600 and 650 °C. Equilibrium FCC catalyst (E-Cat)/ZSM-5 additive was used for catalytic cracking tests at 30 s and catalyst/oil (C/O) ratio of 2.0–6.0. For both thermal and catalytic cracking of all crude oils, the increase in reaction temperature resulted in higher conversion and enhanced yields of C2-C4 light olefins, LPG, coke, and dry gas at the expense of naphtha, heavy cycle oil (HCO), and light cycle oil (LCO). In thermal cracking, the yields of C2-C4 olefins at 650 °C were as follows: AL (22.8 wt.%) > AXL (19.0 wt.%) > ASL (18.8 wt.%) associated with naphtha yields of 34.4, 38.1 and 48.0 wt.%, respectively. Compared with thermal, catalytic cracking over E-Cat/ZSM-5 enhanced conversion, doubled the yields of light olefins and showed an increase in aromatics content of naphtha fraction. Contrary to thermal cracking, the yields of C2-C4 olefins in catalytic cracking were as follows: ASL (42.9 wt.%) > AXL (41 wt.%) > AL (39.1 wt.%) associated with naphtha yields of 31.7, 27.5, and 23.0 wt.%, respectively.

Important role of aromatic hydrocarbons in SOA formation from unburned gasoline vapor

Gasoline emissions are the largest source of urban atmospheric VOCs, which are critical precursors of ozone (O3) and secondary organic aerosol (SOA). Besides vehicle exhaust, emissions from gasoline evaporation also have a potentially significant effect on SOA formation. However, there are still few studies on the relationship between gasoline vapor composition and SOA formation, especially for gasoline in China. In this study, SOA formation from three unburned gasoline vapors were investigated in a 30 m3 indoor smog chamber. The experimental results showed that with the increase of aromatic content (especially toluene and C2 benzenes) in gasoline from 23% to 50%, the SOA yield was significantly enhanced by a factor of 4.0–6.7. This phenomenon might be related to the higher amounts of intermediate volatility organic compounds (IVOCs) and semi-volatile organic compounds (SVOCs) formed, which promoted the gas-particle partitioning and SOA formation. Additionally, the synergistic effects between precursors in the mixtures might also be a key factor, which could be supported by the higher SOA yield accompanied by a higher ratio of toluene/benzene. Meanwhile, there were more oxygenated organic aerosols (OOA) observed when using high-aromatic gasoline. This work will help in understanding the effect of aromatic content or gasoline quality on the SOA formation from gasoline evaporation emissions, and in providing the scientific basis for taking corresponding control measures to relieve haze events in China.

Hydrodeoxygenation of fatty acid methyl ester in gas oil blend–NiMoS/alumina catalyst

AbstractHydrotreating of 10% fatty acid methyl ester (FAME) blended in gas oil was carried out by an NiMo-S/alumina catalyst and performed at an elevated temperature (300–400°C), a space velocity of 0.7–1.5 1/h and pressure 5 MPa. The gas oil was a straight run North Sea crude oil containing 295 ppm sulfur content which was desulfurized in a hydrotreating upgrading process. The physicochemical properties following hydroprocessing of FAME showed that sulfur content was reduced to 3 ppmw, with an increase in aromatic content and cloud point. It was confirmed that decarboxylation depends on temperature and space velocity and decarbonylation depends on temperature, but not on space velocity of feed. High sulfur content in the feedstock supports slow deactivation of the catalyst and low coke formation.

Catalytic cracking of crude oil to light olefins and naphtha: Experimental and kinetic modeling

The direct catalytic cracking of three light crude oils have been evaluated over an equilibrated FCC catalyst (E-Cat) blended with MFI zeolite in a microactivity test unit at 550°C and catalyst/oil ratio between 1 to 4. At 60% conversion, the Super Light (ASL) crude oil yielded about 10wt.% C2–C4 olefins and 60wt.% naphtha over E-Cat, Extra Light (AXL) crude oil yielded 13wt.% light olefins and 52wt.% naphtha, while for Arab Light (AL) crude oil, light olefins and naphtha produced were 12 and 51wt.%, respectively. The addition of MFI with varying Si/Al molar ratio (Z30, Z280 and Z1500) to E-Cat increased the yield of light olefins with a maximum at 21.3wt.% for AXL over E-Cat/Z280. PIONA analysis of co-produced naphtha showed an increase in aromatics content over all additives with a maximum obtained from the cracking of AL over Z30 (91wt.%). Steam treatment of Z280 led to a slight change in the yield of light olefins and reduction of naphtha aromatics for the three types of crude oils. A four-lump kinetic model accurately predicted experimental yields of AL cracking over E-Cat and E-Cat/Z280 between 500°C and 550°C. From the kinetic model, the apparent activation energy for the conversion of naphtha to gases decreased from 21.2kcal/mol over E-Cat to 16.2kcal/mol over E-Cat/Z280 which indicates that Z280 facilitated the increased cracking of naphtha-range species to light olefins

Pyrolytic degradation of polyethylene in autoclave under high pressure to obtain fuel

The availability of waste polyethylene in abundance has made it a potential source of valuable hydrocarbons. A process being widely investigated is the thermocatalytic decomposition of polyethylene as pure thermal degradation at atmospheric pressure produces highly olefinic product, which as such is not suitable as a fuel. A catalyst is usually required to initiate further molecular transformations to produce fuel like hydrocarbons. In the present work high density polyethylene has been degraded in an autoclave with the objective of studying the effect of pressure in a closed system towards composition of the degraded product. It has been observed that degradation of HDPE in a closed reactor in the temperature range of 410–430°C and under pressure in the range of 11–36bar, even without the use of catalyst, leads to a decrease in the olefinic content and simultaneous increase in aromatic content and more branched and cyclo paraffins in the liquid product, thereby making it more suitable to be used as fuel.

Study of the co-pyrolysis of biomass and plastic wastes

This work aimed to study the recovery of two types of waste by the process of pyrolysis. The obtained results show that the adding of a plastic mix improves the overall efficiency of the slow pyrolysis of pine. Therefore, it was possible to achieve higher liquid yields and less solid product than in the classic slow pyrolysis carbonization of biomass. The obtained liquids showed heating values similar to that of heating fuel oil. The gas products had energetic contents superior to that of producer gas, and the obtained solid fractions showed heating values higher than some coals. There were also identified some typical products of fast biomass pyrolysis used as raw material in several industries. The effects of experimental conditions in product yield and composition were also studied. The parameters that showed higher influence were (with its increase): reaction time on gas product composition (increase of the alkane content) and on liquid composition (increase in aromatics content); reaction temperature on product yield (decrease of liquid yield with increase of solids and gases) and on gas product composition (increase in alkane content); initial pressure on liquid composition (increase in the aromatics content) and mainly the pine content of the initial mixture on products yield (increase of gas and solid yield with a decrease in liquids) and on the gas product composition (favouring CO and CO2 formation).

Enzymic hydrolysis of phthalic unit containing copolyesters as a potential tool for block length determination

The hydrolysis of poly(1,2-propanediyl fumarate), poly(1,2-propanediyl phthalate) and poly(1,2-propanediyl fumarate-co-phthalate)s was studied. In the absence of the lipase from Chromobacterium viscosum, all the samples exhibit a weight loss indicating that uncatalyzed hydrolysis and/or solubilization of shortest chains take place. In the presence of the enzyme, the weight loss is much higher except when the sample is poly(1,2-propanediyl phthalate), which means that the enzyme does not catalyze the hydrolysis of the phthalate functions. SEC and 1H-NMR analyses of the hydrolysis residues of copolymers with various aromatic unit contents showed that the weight loss is accompanied by both molecular weight decrease and aromatic content increase. The enzyme specificity was tested on a phthalic model and the results confirmed the assumption of a selective action of the lipase from Chromobacterium viscosum. If the non-specific uncatalyzed hydrolysis is controlled, the selective enzymic degradation of copolyesters will give a good opportunity to study the copolyester sequences by means of hydrolysis residue analysis.

The molecular weight range of pyrolytic oils derived from tyre waste

Pyrolysis oils obtained from the batch pyrolysis of tyre waste were analysed for their molecular weight (MW) distribution using a small molecule, size exclusion chromatography (s.e.c.) system with a dual ultraviolet and refractive index detection system. The tyres were pyrolysed in a nitrogen purged static batch stainless steel reactor heated at 20°C min −1 to a final temperature of 450°C. The evolved pyrolysis vapours were passed directly to a second reactor heated to higher temperatures of 500, 560, 600, 640, 700 and 712°C. The derived oil after secondary cracking was collected in a condensation trap. The analytical system was characterised in terms of the influence of mobile phase flow rate and column temperature on column efficiency, and the behaviour of model hydrocarbons compared to the ideal behaviour of the standard polystyrene calibration curve. The optimum practical operating conditions were 0.26 ml min −1 flow rate and 0°C column temperature. The pyrolytic oil had a MW range from a nominal 50 to 1200. The oils showed a decrease in MW as the secondary reactor temperature was increased. The oils were fractionated in terms of their chemical classes using liquid chromatography, and each fraction was also analysed using the s.e.c. system. The oils showed an increase in aromatic content and decrease in aliphatic content as the secondary reactor temperature was increased. The aromatisation of the oils was due to a Diels-Alder type reaction involving pyrolysis of alkanes to alkenes, and subsequent cyclisation to aromatic and polycyclic aromatic compounds. The millivolt output of each detector was compared and gave a measure of the aromaticity of the oils when compared to the chemical class fractionation.

Concentrations of particulate and gaseous polycyclic aromatic hydrocarbons in London air following a reduction in the lead content of petrol in the United Kingdom

The environmental importance of tropospheric polycyclic aromatic hydrocarbons (PAH) is reviewed. The impact of reducing lead on airborne PAH is indicated and the importance of monitoring both particulate and gaseous-phase PAH is demonstrated. A Brief description of a sampling regime performed from 1985 to 1987 is given. Sampling of 18 PAH was performed and particulate lead concentrations at the kerbside were measured concurrently. Measurements indicate that there is a pronounced seasonality in PAH concentrations and in the distribution of PAH between particulate and gaseous phases. On average, 47% of the PAH measured were in the gaseous phase, indicating the importance of measuring the volatile fraction. The dominance of the common variation of each PAH was also investigated using principal components analysis. An uneven spread of data prior to and following the reduction in lead content, hindered a thorough examination of the effect of this change on PAH concentrations. However, they appeared to indicate only a small change in PAH concentration and this was linked to an increase in aromatic content of the petrol, which was much less than expected.

Maturity of kerogen and asphaltenes determined by partial-least-squares (PLS) calibration and target projection of diffuse reflectance Fourier transformed infrared spectra

Maturation of sedimentary organic matter expressed as: (1) vitrinite reflectance; (2) depth within the same geological formation; and (3) pyrolysis temperature in hydrous pyrolysis experiments is assessed by diffuse reflectance i.r. spectroscopy either using an index defined from intensities of specific peaks or through a multivariate calibration of the spectral profiles with their respective maturation indicators as dependent variables. The samples were of three kinds: (a) kerogen samples (46) of varying maturity from the North Sea; (b) asphaltene samples (108) prepared from sediments obtained from two different wells and a reservoir from the North Sea; and (c) asphaltene samples prepared from hydrous pyrolysate of a sediment containing type II kerogen. The spectra show that the following chemical processes take place during maturation: (i) elimination of carbonyl groups; (ii) depletion of aliphatic chains; and (iii) increase in aromatic content. The univariate index, although sensitive to changes in organic facies, seems applicable within the oil window with the best results obtained for type III kerogen. Multivariate calibration of kerogen samples reveals the capability of the PLS method for predicting vitrinite reflectance. Target projections of the PLS components provide validated spectral profiles, related to the collective changes taking place during both natural and simulated evolution.