Paul N. Sharratt

Catalytic degradation of high density polyethylene: An evaluation of mesoporous and microporous catalysts using thermal analysis☆

Abstract Catalytic degradation of waste polymers offers the potential for the selective recovery of useful chemical fractions by influencing the product distributions. Thermogravimetric analysis has been used to investigate the activity of various aluminosilicate catalysts in the degradation of high density polyethylene (HDPE). Amorphous silica-alumina significantly reduced the apparent activation energy as compared with uncatalysed thermal processes. Zeolites Y and ZSM-5 further reduced the activation energy resulting in more rapid degradation. Aluminium containing MCM-41 was found to be active in the degradation of HDPE at a rate similar to that of HZSM-5, confirming the potential of this family of materials in the cracking of heavier hydrocarbons.

Deactivation of US-Y zeolite by coke formation during the catalytic pyrolysis of high density polyethylene

Abstract Catalytic pyrolysis of waste polymers over zeolitic catalysts has the potential to recover valuable hydrocarbons. Thermogravimetric analysis has been used as a tool to characterise the activity, regenerability and deactivation behaviour of zeolite US-Y in the degradation of high density polyethylene (HDPE). Deactivation of the catalyst occurs due to the deposition of coke. Analysis of the TGA results allowed a relationship between catalyst activity and coke content to be derived. The catalyst activity was found to fall exponentially with coke content.

A life-cycle framework to analyse business risk in process industry projects

Abstract The chemical and related process industries are particularly exposed to high environmentally related costs arising from normal operation and accidents, not only of their own processes but also other processes in their supply chains. A methodology (Process environmental risk assessment—PERA) is presented for the assessment of all such risks during the design of new processes. This can be seen as a project-centred risk assessment that seeks potential problems along the whole supply chain. Each activity, resource use or waste source along the supply chain represents a potential interaction between the supply chain and the environment. These potential interactions are identified systematically using a life-cycle based assessment. To assess the risk to the project or process supply chain arising from those interactions the relevant stakeholders must be identified. Their likely response can then be considered and ranked according to the risk it poses. The methodology facilitates the management and communication of risk, and is illustrated by application to some aspects of the manufacture of PVC. The method could equally be applied to the assessment of existing processes.

Environmental criteria in design

Abstract The representation of process environmental performance in the modelling of chemical processes is considered. The wide range of environmental effects associated with chemical processes is discussed. Selection of appropriate representations depends on the stage of design, the effects to be considered and the nature of the design decisions to be supported. The objective of the paper is to provide guidelines for the modeller to support the selection of appropriate measures of environmental performance.

Pharmaceutical process validation: An overview:

Abstract Drugs are critical elements in health care. They must be manufactured to the highest quality levels. End-product testing by itself does not guarantee the quality of the product. Quality assurance techniques must be used. In the pharmaceutical industry, process validation performs this task, ensuring that the process does what it purports to do. It is also a regulatory requirement. This paper presents an introduction and general overview of this process, with special reference to the requirements stipulated by the US Food and Drug Administration (FDA).

Zeolite A membranes for use in alcohol/water separations. Part I: Experimental investigation

Controlled hydrothermal growth on an ultrasonically-anchored nanocrystal precursor layer has provided a route to coherent zeolite A membranes on sintered stainless steel supports. High water selectivity is demonstrated in measurements of fluxes through the membrane using 80–98 mass % ethanol/water mixtures at temperatures of 25–60°C. The use of the hydrophobic/hydrophilic properties of molecular sieve zeolites to separate alcohol water mixtures is discussed.

Influence of Initial Dissolved Oxygen Concentration on Fenton's Reagent Degradation

The effect of initial dissolved oxygen concentration (IDOC) on Fentons reagent degradation of a dyestuff, Reactive Black 5 was explored in this study. The study was designed, conducted and analysed based on Central Composite Rotatable Design using a 3-l lab-scale reactor. The participation of O2 in the process was experimentally observed and appears to be affected by the dosage of the reagents used in the study. The IDOC was found to have a significant influence on the process. Reducing the IDOC from 7.5 mg l−1 to 2.5 mg l−1 increased the removal of TOC by an average of about 10%. Reduction of IDOC from 10 mg l−1 to 0 mg l−1 enhanced the TOC removal by about 30%. The negative influence of IDOC is likely to be caused by the competition between the O2 and the reagents for the organoradicals. A model describing the relationship between initial TOC removal, reagent dosage and IDOC has also been developed.

Fenton oxidation of Reactive Black 5: effect of mixing intensity and reagent addition strategy.

This study investigates the effect of mixing intensity and reagents addition strategy on Fentons reagent degrading a common reactive diazo type dyestuff, Reactive Black 5. Within the experimental conditions used in the study, the effect of mixing intensity on TOC removal was observed to be both significant and complex. Using factorial analysis, it was found that if the reagents are added near to each other, higher mixing intensity will enhance the effectiveness of the degradation process. However, a very high mixing level may cause reduction in performance. It was also observed that the mixing intensity effect interacts with Fe2+ or/and H2O2 dosage. The benefit of increasing mixing intensity appears to be higher for lower reagents dosage. The effect of reagents addition strategy was found to be inter-dependent with mixing intensity level. It was also deduced that proper chemical addition strategy could be used to reduce the mixing intensity requirement of the process.

Molecular dynamics methodology for the study of the solvent effects on a concentrated Diels-Alder reaction and the separation of the post-reaction mixture

A molecular dynamics methodology for the analysis of the effect of solvents on reaction kinetics and post reaction separation is presented. A model reaction between cyclopentadiene and methylacrylate is used to illustrate key issues such as product selectivity, rate enhancement and the post reaction separation of the product using liquid-liquid extraction techniques. Using Transition State theory as a basis, NVT ensembles are used to calculate excess Gibbs free energies and activity coefficients. The advantages and disadvantages of the use of this technique for a chemical engineering design tool are discussed and preliminary results for the separation stage are given.

ENVIRONMENTAL OPTIMISATION OF RELEASES FROM INDUSTRIAL SITES INTO A LINEAR RECEIVING BODY

Abstract Changes to environmental legislation are setting new challenges to both operators and regulators. Optimisation tools can help to turn subjective standards such as Best Practicable Environmental Option (BPEO) (HMIP, 1994: Sharratt, 1995) into more objective ones. Mixed Integer Non Linear Programming (MINLP) is used in this work to optimise overall environmental performance for a group of plants. These plants discharge their final effluents to the same receiving body — a river. The optimisation considers not only the possible configurations within each plant but also the behaviour of the receiving body. A two-stage optimisation is used. Examples illustrate the features of the model.