R. Hughes

Enhancement of esterification reaction yield using zeolite A vapour permeation membrane

Abstract A tubular zeolite NaA membrane, prepared on a carbon/zirconia support, was tested for the removal of water from water/isopropanol and water/ethanol mixtures, in both pervaporation and vapour permeation modes, and shown to give high selectivity. The esterification of lactic acid with ethanol to give ethyl lactate was studied in a batch reactor, without catalyst and with p -toluene sulphonic acid as catalyst. The use of a zeolite A vapour permeation membrane to remove water generated by the reaction gave substantially enhanced yields of product, compared to control experiments carried out without the membrane and with the membrane but without vacuum being applied.

Computer simulation of BTEX emission in natural gas dehydration using PR and RKS equations of state with different predictive mixing rules

Abstract A typical natural gas dehydration plant, which employs triethylene glycol (TEG) as the dehydrating agent, is simulated using a steady state flowsheeting simulator (Aspen Plus). All major units were included in the flowsheet, that is: absorption column, flash unit, heat exchangers, regenerator, stripper, and reboiler. The base case operating conditions are taken to resemble field data from one of the existing dehydration units operating in the United Arab Emirates (UAE). To explore effects of the thermodynamic model employed in the simulator on the reliability of the whole simulation process, different predictive mixing rules applied to two cubic equations of state (EOS), as programmed by the simulator, have been investigated. The EOS used in the simulation is the Redlich–Kwong–Soave (RKS) and the Peng–Robinson (PR), both with Boston–Mathias (BM) alpha function. In addition to the classical empirical mixing rules, the following ones are investigated: Predictive Soave–Redlich–Kwong–Gmehling (PRKS), Wong–Sandler (WS), and Modified-Huron–Vidal (MHV2) mixing rules. These mixing rules are all predictive in nature. The plant performance criteria that have been studied for their response to changes in the solvent circulation rate include: BTEX (benzene, toluene, ethyl benzene, and xylenes) emissions rate, desiccant losses (makeup), water content in the dehumidified natural gas, purity of the regenerated TEG, and reboiler heat duty. Comparison with the field data is done. Very diverse results have been obtained from the different models and mixing rules. No one single model gives the best results for all criteria.

Combustion characteristics of crude oil-limestone mixtures

High pressure thermogravimetric analysis (HPTG) was used in order to study the oxidation of crude oil in a porous medium under pressurised conditions for simulation of in-situ combustion during oil recovery. Three distinct reaction regions were observed from the HPTG curves in an oxidising environment subjected to a constant heating rate. These were low temperature oxidation, fuel deposition and high temperature oxidation. The method of Coats and Redfern was used to obtain kinetic parameters and the results are discussed.

High pressure TGA analysis of crude oils

A high pressure thermogravimetric analyser (HPTGA) has been used to explore the effect of total pressure (100, 200 and 300 psig) on the combustion behaviour and kinetics of crude oils. In combustion with air, three different reaction regions were identified, known as low-temperature oxidation, fuel deposition and high temperature oxidation. The Coats and Redfern procedure was applied to determine the kinetic parameters of the crude oils studied.

Development of an Experimental Protocol to Evaluate FCC Stripper Performance in Terms of Coke Yield and Composition

Tests have been conducted in a microactivity test (MAT) and a fluidized bed reactor to develop an experimental protocol to determine how the yield and composition of coke and the associated catalyst surface area vary as a function of stripper conditions in fluid catalytic cracking (FCC). In both reactors, the use of rapid quenching has allowed the relatively short stripping times encountered in FCC units to be simulated. Low sulphur vacuum gas oils (VGO) with a low metal equilibrium catalyst (E-cat) were used for stripping periods of up to 20 minutes. Significant variations occur in the structure of both hard and soft coke during stripping. Although the hard coke becomes more highly condensed with prolonged stripping, the surface area reduction by the hard coke remains fairly constant for stripping periods in excess of ca. 5–10 minutes and is small (10m2 g–1) in relation to the loss of surface area from the soft coke. The use of about 70 g of catalyst in the fluidized bed provides sufficient sample for demineralization to recover sufficient of the hard coke for 13C NMR analysis after the initial extraction of the soft coke. Indeed, it has been found that a further pool of soft (chloroform soluble) coke is physically entrapped within the catalyst pore structure and is only released after demineralization. In fact, this second soft coke fraction is much more highly aromatic than the first and ultimately controls the final coke yield. For the combination of E-cat and VGOs investigated here, typically about half of the final hard coke content of nearly 1% w/w catalyst is derived from this second soft coke fraction by carbonization. The structural information obtained has been used to formulate a model for the stripping process where the soft coke II fraction undergoes cracking in competition with coke formation and evaporative removal from the catalyst.

The use of thermal analysis techniques to obtain information relevant to the in-situ combustion process for enhanced oil recovery

Thein-situ combustion technique of enhanced oil recovery may be used for the recovery of heavy oil deposits. In order to predict when this process may be used computer-based simulators are being developed. The data required by these simulators are currently available from two sources: (i) combustion tubes; these are complex, expensive and time consuming to run; (ii) thermal analysis techniques; these are fast, small-scale and relatively inexpensive. Thermal analysis literature relevant to the process is reviewed and related thermal analysis studies being conducted at Salford University are described.ZusammenfassungDiein-situ-Verbrennungstechnik der verbesserten Ölrückgewinnung kann zur Rückgewinnung von Schwerölrückständen verwendet werden. Um die Einsatzmöglichkeiten dieses Prozesses zu ergründen, werden computergestützte Simulatoren entwickelt. Die für diese Simulatoren notwendigen Daten können aus zwei Quellen gewonnen werden: (i) Verbrennungs-rohre; ihre Anwendung ist kompliziert, teuer und zeitaufwendig; (ii) thermo-analytische Methoden; diese sind schnell, kleinangelegt und relativ nicht teuer Es wird ein kurzer Überblick über die auf diesen Prozeß bezogene Thermoanalysen-Literatur gegeben und es werden verwandte, an der Salford-Universität durchgeführte thermoanalytische Untersuchungen beschrieben.

The reduction of iron ores by hydrogen and carbon monoxide and their mixtures

Abstract Experimental measurements of the rate of reduction of particles of Carol Lake and Kiruna ores have been made using pure hydrogen and pure carbon monoxide and mixtures of these two gases. The temperature range covered was 773–1143 K and throughout this range the reduction rate with hydrogen was greater than that with carbon monoxide. A retracting core model was found to best fit the experimental data even when granules of 9 × 10−4 m diameter were used. Reduction with gas mixtures of hydrogen and carbon monoxide give rates intermediate between those of the pure gases.

A Fundamental Study of The Deactivation of Fcc Catalysts: A Comparison of Quinoline and Phenanthrene as Catalysts Poisons

The effects of quinoline and phenanthrene as additives to the feedstock of the FCC reaction over a standard FCC type catalyst are described and discussed. The studies were carried out using hexadecane as a model feedstock to enable the efforts of these additives on the product distribution to be readily determined. Phenanthrene and quinoline (10% in hexadecane) both lead to an overall loss in conversion. The amount of coke deposited under standard conditions decreases in the order: phenanthrene > hexadecane > quinoline and the coke selectivity varies in the order: phenanthrene > quinoline > hexadecane Characterisation of the coke indicates that the initial coke formed from hexadecane is aliphatic in nature. Quinoline is considered to act as solely as a catalyst poison and does not participate in coke formation. However, phenanthrene does participate in coke formation and the coke becomes more aromatic in nature and hence phenanthrene is considered to act as a coke inducer.

An Experimental Study of CO2 Separation Using a Silica Based Composite Membrane

In this investigation, the preparation and gas selectivity characteristics of an ‘ultrafine’ composite ceramic membrane are reported. A dip-coating technique was used to prepare a thin selective membrane on a commercially available ceramic macroporous filter (SCT, France). The permeabilities of H2, N2 and CO2 were measured at temperatures of 25–470°C and average pressures of 1–2 bar. The separation of CO2/N2 binary mixtures was also performed. The separation factors for CO2 were found to be higher than that of the Knudsen separation mechanism at room and high temperature. The potential applications of these membranes to CO2 separation at these temperatures are discussed on the basis of measured selectivity values.

The Efficient Combustion of O-Xylene in a Knudsen Controlled Catalytic Membrane Reactor

Catalytic inorganic membrane preparation and the catalytic oxidation of o-xylene contained in air streams on catalytic membrane tubes are presented in this study. Boehmite prepared sols were deposited onto porous alumina tubes from the outside using a filtration coating technique. The coatings were characterized by nitrogen gas permeations at the same temperatures used for the o-xylene experiments. Single gas permeabilities indicated a best separation factor for the modified membrane for H 2 /N 2 of 3.6, which is very close to the Knudsen value. Pt loading was estimated as 1.6%w/w based on membrane material weight by using both weighing and atomic absorption spectrophotometry (AAS) methods. O-xylene catalytic oxidation of o-xylene contained in air streams with concentrations between 0.146–0.220% (v/v) was carried out in a catalytic membrane reactor at temperatures between 150–290°C and 97% conversion was achieved for 0.146% o-xylene in air at a temperature of 285°C.