Octane upgrading of C-5/C-6 light naphtha by layered pressure swing adsorption

The performance of a layered pressure swing adsorption (PSA) process for the separation of high research octane number (HRON) paraffins from a C-5/C-6 light naphtha fraction is simulated with a detailed, adiabatic single column PSA model. A zeolite 5A layer is used for selective adsorption of the low RON linear paraffins, while a zeolite beta-layer is used to separate the intermediate RON 3MP from the H RON fraction. The effects of various independent process variables (zeolite 5A to zeolite beta ratio, purge to feed ratio, cycle time, operating temperature, and depressurization mode) on the key dependent process variables (product RON, H RON species recovery, HRON purity, and adsorbent productivity) are evaluated. It is demonstrated that an optimal zeolite 5A to zeolite beta ratio can improve the product average RON up to 1.0 point as compared to existing processes using zeolite 5A only. Moreover, process simulations demonstrated that increasing the operating temperature from 523 to 543 K results in an octane gain of 0.2 RON

Separation of branched hexane isomers using zeolite BEA for the octane improvement of gasoline pool

A sorption study of single, binary, ternary and quaternary mixtures of hexane (C6) isomers nhexane (nHEX), 3-methylpentane (3MP), 2,3-dimethylbutane (23DMB) and 2,2- dimethylbutane (22DMB) was performed in commercial pellets of zeolite BETA (BEA structure), covering the temperature range between 423 K and 523 K and partial pressures up to 0.3 bar. From these data, single and multicomponent adsorption equilibrium isotherms were collected. An extended tri-site Langmuir model (TSL) was developed to interpret accurately the equilibrium data, and a dynamic adsorption model was developed and tested predicting with a good accuracy the behaviour of multicomponent fixed bed experiments. At the partial pressures studied, the sorption hierarchy in the zeolite BETA is: nHEX>3MP>23DMB>22DMB. BEA structure demonstrates a significant selectivity between C6 isomers, especially at low coverage, giving a good perspective regarding future workJosé A. C. Silva acknowledges financial support from Fundação para a Ciência e Tecnologia under project EQU/60828/2004. Patrick S. Bárcia acknowledges a FCT grant (SFRH/BD/30994/2006)

Octane Upgrading of TIP Processes by Recycling in a Layered Zeolite 5A/BETA PSA

The objective of this work consists in studying the separation mono/dibranched paraffins by cyclic adsorption process using a layered bed of zeolites 5A and Beta (Figure 1). Aspen ADSIM 2006.5 (AspenTech Inc.) was used for numerically solving an adiabatic dynamic model incorporating mass, energy and momentum balance. Model parameters were taken from experimental data reported in the literature 1, 2. Parametric studies were simulated to determine how process performance is affected by purge quantity, 5A-to-Beta ratio, repressurization/blowdown schemes and operating temperature. Figure 2 shows that a combination of zeolites 5A and Beta can produce an octane gain of 1 RON at 523 K comparatively to the conventional TIP3 by reducing the monobranched C6 fraction in the product. Another advantage of this configuration is the possibility to increase the penetration distance because zeolite Beta acts like a “barrier” to the linear alkanes desorbed from zeolite 5A during the cocurrent depressurization step. It was also demonstrated that a slight increase in temperature (20 K) results in a RON benefit of 0.2 points. Several alternatives are provided to improve the performance of the existing TIP processes with this combination of adsorbents

Adsorption equilibrium and kinetics of branched hexane isomers in pellets of BETA zeolite

Sorption equilibrium and kinetics of hexane isomers: n-hexane (nHEX), 3-methylpentane (3MP), 2,3-dimethylbutane (23DMB) and 2,2-dimethylbutane (22DMB) were studied in commercial pellets of zeolite BETA in the form HBEA with a SUM ratio of 150, between temperatures of 423 and 523 K and partial pressures up to 0.3 bar. Four different models were used to interpret the equilibrium data, named: Langmuir, multi-site Langmuir, dual-site Langmuir and Toth. The affinity to the adsorbent measured by the Henry's constants decreases with the degree of branching, with selectivities that can reach a value of 8.8 between nHEX and 22DMB. The heats of adsorption at zero coverage decrease with the degree of branching, being: 63.4 kJ/mol for nHEX, 59.7 kJ/ mol for 3MP, 57.1 kJ/mol for 23DMB and 53.6 kJ/mol for 22DMB. However, the isosteric heat of sorption changes with coverage with a different behavior for the three isomers. Sorption kinetics studied by the Zero Length Chromatography (ZLC) technique allowed us to find the nature of controlling the diffusion mechanism (macropore or micropore); for nHEX and 3MP macropore diffusion is controlling with activation energies similar to the heats of sorption at zero coverage. For 23DMB and 22DMB, the controlling mechanism changes, being the system governed apparently by both macropore and micropore diffusion. Data from this work are also compared with those reported in literature for both zeolite BETA and silicalite. (c) 2004 Elsevier Inc. All rights reserved

Separation of light naptha by adsorption processes

In this work we studied the separation linear/mono/di-branched paraffins in a cyclic Pressure Swing Adsorption process using a layered bed of zeolites 5A and Beta (Figure 1). Zeolite Beta proved to be an efficient separator of mono-branched from di-branched paraffins [3]. Aspen ADSIM (AspenTech Inc.) was used for numerically solve an adiabatic dynamic model incorporating mass, energy and momentum balances. Model parameters were taken from experimental data obtained in our lab. The studies were performed with the objective to determine how process performance is affected by purge quantity, 5A-to-Beta ratio, repressurization/blowdown schemes and operating temperature which are typical operating parameters of PSA processes. Figure 2 shows the product average RON as a function of the zeolite 5A layer length and purge-to-feed ratio at T = 523 K, where it can be seen that RON is above 90 when the ratio of the layered bed is nearly 0.6. It was also demonstrated that a slight increase in temperature (20 K) results in a RON benefit of 0.2 points. Several alternatives are also provided to improve the performance of the existing TIP processes with this combination of adsorbents [4]

Separation by fixed-bed adsorption of hexane isomers in zeolite BETA pellets

An experimental study of single and binary fixed-bed adsorptions of hexane isomers n-hexane (nHEX), 3-methylpentane (3MP), 2,3-dimethylbutane (23DMB) and 2,2-dimethylbutane (22DMB) was performed in commercial pellets of zeolite BETA, covering the temperature range between 423 and 523 K and partial pressures up to 0.3 bar. The effect of partial pressure and temperature on the shape of the breakthrough curves was addressed. From these data, single and binary adsorption equilibrium isotherms were collected. On the basis of the analysis of sorption events at the molecular level, two different models were used to interpret, with good accuracy, the equilibrium data: dual-site Langmuir (DSL) for nHEX and 3MP and multisite Langmuir (MSL) for 23DMB and 22DMB. Thereafter, a dynamic adsorption model was developed and tested, predicting with good accuracy the behavior of the fixed-bed experiments. At the partial pressures studied, it was found that the affinity of the isomers to the zeolite is nHEX > 3MP > 23DMB > 22DMB. The selectivity between the isomers is higher at low partial pressures, decreasing as the amount adsorbed increases. The Ideal Adsorbed Solution Theory using the DSL model to describe the pure component equilibrium of nHEX and 3MP and the MSL model for the dibranched isomers 22DMB and 23DMB gives a good prediction of the mixture adsorption data

Upgrading of the light naphata fraction with zeolite beta

Multicomponent adsorption of alkanes in the C5-C6 range was investigated in a sample of zeoliteBETA. 6-components breakthrough experiments were performed showing interesting properties forthe separation of the light naphtha fraction. The lower adsorption enthalpy of C5 alkanes was explored by a temperature sensibility analysis demonstrating that at 583 K C5/C6 equimolar mixture can be separated in a single step into low and high octane number (RON) fractions. The separation 23DMB/3MP can not be achieved in the case of mixtures with the typical composition of the isomerization products, but zeolite BETA still selective for 22DMB resulting in a slight increase of the RON comparatively to the final isomerate from the conventional processes

Prospects of the use of solar water heaters in demand side management in Uganda

Izael Pereira Da Silva, Patrick Mugisha, Makerere University, Kampala, Uganda.The commercial sector in Uganda accounts for about 20% of the total electrical energy consumed in the country, with about 50% consumed in the domestic sector and the remaining 30% to the industrial sector. As the economy continues to grow due to attraction of foreign investment and improvement in local production, more challenges now come up in terms of sustaining the already-attained levels of development and social transformation. It is known that Uganda has only 300 MW of installed electric power capacity. This power is insufficient and could be used better - it is estimated that about 40 MW of the total load is allocated to water heaters. Among the energy-saving schemes being implemented in the commercial sector to avoid or reduce load shedding and to reduce the use of costly generators is the use of Solar Water Heaters (SWHs). A case study on the use of solar water heating in a three-star hotel as a means of implementing an energy saving scheme is presented and an economic analysis of the project is given. Finally, future prospects of use of solar thermal technologies in the commercial sector as a means of energy conservation and as a solution to some of the environmental concerns under Clean Development Mechanisms (CDM) are presented.The commercial sector in Uganda accounts for about 20% of the total electrical energy consumed in the country, with about 50% consumed in the domestic sector and the remaining 30% to the industrial sector. As the economy continues to grow due to attraction of foreign investment and improvement in local production, more challenges now come up in terms of sustaining the already-attained levels of development and social transformation. It is known that Uganda has only 300 MW of installed electric power capacity. This power is insufficient and could be used better - it is estimated that about 40 MW of the total load is allocated to water heaters. Among the energy-saving schemes being implemented in the commercial sector to avoid or reduce load shedding and to reduce the use of costly generators is the use of Solar Water Heaters (SWHs). A case study on the use of solar water heating in a three-star hotel as a means of implementing an energy saving scheme is presented and an economic analysis of the project is given. Finally, future prospects of use of solar thermal technologies in the commercial sector as a means of energy conservation and as a solution to some of the environmental concerns under Clean Development Mechanisms (CDM) are presented

In Vitro and In Vivo Trypanosomicidal Action of Novel Arylimidamides against Trypanosoma cruzi

ABSTRACT Arylimidamides (AIAs) have been shown to have considerable biological activity against intracellular pathogens, including Trypanosoma cruzi , which causes Chagas disease. In the present study, the activities of 12 novel bis-AIAs and 2 mono-AIAs against different strains of T. cruzi in vitro and in vivo were analyzed. The most active was m -terphenyl bis-AIA (35DAP073), which had a 50% effective concentration (EC 50 ) of 0.5 μM for trypomastigotes (Y strain), which made it 26-fold more effective than benznidazole (Bz; 13 μM). It was also active against the Colombiana strain (EC 50 = 3.8 μM). Analysis of the activity against intracellular forms of the Tulahuen strain showed that this bis-AIA (EC 50 = 0.04 μM) was about 100-fold more active than Bz (2 μM). The trypanocidal effect was dissociated from the ability to trigger intracellular lipid bodies within host cells, detected by oil red labeling. Both an active compound (35DAP073) and an inactive compound (26SMB060) displayed similar activation profiles. Due to their high selectivity indexes, two AIAs (35DAP073 and 35DAP081) were moved to in vivo studies, but because of the results of acute toxicity assays, 35DAP081 was excluded from the subsequent tests. The findings obtained with 35DAP073 treatment of infections caused by the Y strain revealed that 2 days of therapy induced a dose-dependent action, leading to 96 to 46% reductions in the level of parasitemia. However, the administration of 10 daily doses in animals infected with the Colombiana strain resulted in toxicity, preventing longer periods of treatment. The activity of the combination of 0.5 mg/kg of body weight/day 35DAP073 with 100 mg/kg/day Bz for 10 consecutive days was then assayed. Treatment with the combination resulted in the suppression of parasitemia, the elimination of neurological toxic effects, and survival of 100% of the animals. Quantitative PCR showed a considerable reduction in the parasite load (60%) compared to that achieved with Bz or the amidine alone. Our results support further investigations of this class with the aim of developing novel alternatives for the treatment of Chagas disease