Michael B. Cutlip

Study of blend membranes consisting of NafionR and vinylidene fluoride–hexafluoropropylene copolymer

An attempt to modify membranes for direct methanol fuel cells by blending NafionR with a (vinylidene fluoride)–hexafluoropropylene copolymer (VDF–HFP copolymer) from their solutions is reported. The purpose of this work was to reduce the methanol transport while still retaining the essential proton conductivity in a water-containing environment. The apparent conductivity, methanol barrier property, and equilibrium contact angle as a function of the membrane compositions are discussed. The blend membranes were also investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Compared with the pure NafionR membrane, the NafionR/VDF–HFP copolymer blend membrane with 62.5 vol % of the VDF–HFP copolymer shows a decrease in the apparent conductivity by about 2 orders of magnitude, and the methanol barrier properties increase substantially when only 25 vol % of the VDF–HFP-copolymer is incorporated. The equilibrium contact angles of water drops on the NafionR/VDF–HFP copolymer blend membranes as a function of the VDF–HFP copolymer content are rather similar to the plot of the advancing angle versus the percentage of the lower-surface-energy phase. X-ray diffraction studies indicate that these two polymers crystallize separately when blended and cast from their solutions, and the crystallization behavior is equivalent to that of the unblended state. DSC reveals that when the VDF–HFP copolymer is mixed with NafionR in their solution forms, an interdiffusion or other interaction takes place at the interfaces between their noncrystalline regions.

Photoassisted catalytic oxidation of alcohols and halogenated hydrocarbons with amorphous manganese oxides

Abstract This manuscript discusses the synthesis of Amorphous Manganese Oxide (AMO) materials that are used for efficient photoassisted catalytic oxidation of alcohols and halogenated hydrocarbons. Characterization studies suggest that oxygen is lost from AMO very readily under illumination, creating oxygen vacancies that may be important in photooxidation reactions. Alcohols are converted to ketones such as acetone from isopropanol with 100% selectivity at room temperature. These AMO systems have turnover numbers that are over one order of magnitude greater than TiO 2 systems for isopropanol oxidation and over an order of magnitude greater than for TiO 2 systems in decomposition of halogenated hydrocarbons. In addition the TiO 2 systems are poisoned much faster than the AMO materials, especially in degradation of halogenated hydrocarbons. The same high activity and selectivity occur for the total oxidation of halogenated hydrocarbons such as methyl bromide which is converted into CO 2 , H 2 O and Br 2 . The synthesis, characterization, and photoactivity of these materials will be discussed. AMO photocatalysts are also active in the decomposition of methyl choride and methyl iodide.

Open architecture modelling and simulation in process hazard assessment

Abstract Dynamic modelling and simulation of a chemical process in emergency conditions is considered. Such modelling and simulation often requires rapid implementation of model changes by the process engineer followed by simulation runs. A simulator with an open architecture structure is presented where the model components (equations) are stored in an object-oriented form in a database, enabling rapid and easy modification of the model. A general-purpose numerical solver is used for solving the model and plotting the pertinent results. An example is presented, where the use of the proposed simulator enables a rapid identification of the right strategy to prevent development of runaway temperature conditions in a reactor.

A web-based library for testing performance of numerical software for solving nonlinear algebraic equations

Abstract An extensive test problem library of nonlinear algebraic equations (NLE) has been created and implemented on the World Wide Web. This web-based test problem library contains complete problem descriptions with the following information: the model equations in the same form as the input for the numerical solver, the explicit definitions of constraints on the variables, the initial estimates and function values at the initial estimates, and the variable values and function values at the solution. All variables and function values are reported with the full precision of the numerical solution. This library improves upon existing test problem collections regarding the type of information included and the form in which this information is stored and presented. The NLE library can be accessed through the Web site: http://www.polymath-software.com/library. It contains presently over 70 problems of various dimensions on lower, average, and higher difficulty levels. Some of the problems exhibit multiple solutions in the feasible and/or the infeasible subspaces, discontinuities, and false solutions that are identified as true solutions by most numerical solvers. This library can be of significant benefit to users and developers of NLE solvers for verifying the robustness and reliability of NLE solvers.

The integration of process safety into a chemical reaction engineering course: Kinetic modeling of the T2 incident†

The explosion and subsequent death of four people at the T2 Laboratories, chemical facility in Jacksonville, Florida, USA, in 2007 has resulted in the United States Chemical Safety Board finding that undergraduate chemical engineering students do not receive adequate knowledge in the hazards associated with chemical processing. This article summarizes the events that led up to the T2 tragedy. A reactor engineering analysis of the event is presented that can be used in a chemical reaction engineering classroom to demonstrate the hazards involved when dealing with exothermic reactions and methods to mitigate.

A collection of 10 numerical problems in chemical engineering solved by various mathematical software packages

Current personal computers provide exceptional computing capabilities to engineering students that can greatly improve speed and accuracy during sophisticated problem solving. The need to actually create programs for mathematical problem solving has been reduced if not eliminated by available mathematical software packages. This article summarizes a collection of 10 typical problems from throughout the chemical engineering curriculum that require numerical solutions. These problems involve most of the standard numerical methods familiar to undergraduate engineering students. Complete problem solution sets have been generated by experienced users in six of the leading mathematical software packages. These detailed solutions including a writeup, and theelectronic files for each package are available through the Internet at www.che.utexas.edu/cache, and via FTP from ftp.engr.uconn.edu/pub/ASEE/. The written materials illustrate the differences in these mathematical software packages. The electronic files allow hands‐on experience with the packages during execution of the actual software packages. This article and the provided resources should be of considerable value during mathematical problem solving and/or the selection of a package for classroom or personal use.

Replacing graph paper with interactive software in modeling and analysis of experimental data

The techniques presented in introductory engineering textbooks for modeling and analysis of experimental data nowadays are essentially the same as the ones that were presented over 35 years ago. Considerable potential now exists for dramatic improvements in data correlation and analysis because of the introduction of personal computers along with user-friendly interactive software which performs linear and nonlinear regressions and yields standard statistical results. This article presents some basic statistical concepts which are required to understand the results obtained from a regression package and demonstrates, using an example of vapor pressure correlation the proper technique for modeling and analysis of experimental data. Our experience and student performance has indicated that a 1st-year course for engineering students can effectively introduce students to the correlation and the modeling of experimental data. This capability can be given to students during two lectures and a 1-hour computer laboratory period plus an appropriate assignment, provided that an interactive regression package Polymath or EZfit, for example or a spreadsheet program with multiple linear regression capabilities is available.

Selecting the appropriate numerical software for a chemical engineering course

Abstract Criteria for evaluating mathematical software packages and the results of a recent comparison of such packages are briefly reviewed. A benchmark problem that was developed based on the results of this comparison is presented. This problem can be used in various courses, representing various levels of knowledge in chemical process analysis, mathematical modeling and numerical methods where the solution is achieved using the software most appropriate to the objectives of the particular course. This work demonstrates and illustrates the conclusion that the most educational benefits can be gained by using several packages throughout the chemical engineering curriculum. The software that is most appropriate for a particular course must be determined according to the course objectives and the previous exposure of the students to mathematical models, numerical algorithms and computer programming.

What is “in” and what is “out” in engineering problem solving

Abstract The introduction of mathematical software packages as effective and efficient means for engineering problem solving, allows the retirement of many calculational methods and the application of efficient computer-based techniques that are enabled by effective software. This paper discusses the following issues: analytical versus numerical solution techniques, graphical versus numerical solution techniques, teaching numerical methods and programming, validation and comparison of regression models, and determination of the number of significant digits in the reported results of numerical solutions.

Modeing nucleophilic substitution reactions to investigate the feasibility of elution processes

A mathematical model was developed to investigate the efficacy of nucleophilic substitution reactions to enhance contaminant mobility during elution processes. The model describes the hydrolysis (SN2 reaction) of N‐2,4,6‐tetranitro‐N‐methylaniline (tetryl), adsorbed onto soil. The reaction products include picrate, methylamine, and nitrite. Picrate the major hydrolysis product (88%) is considerably more soluble than tetryl as well as being biodegradable. Tetryl is recalcitrant to biodegradation. A model was developed to provide a basis for the design of an experimental protocol to investigate the feasibility of this process. The model describes a continuously stirred batch reactor and provides temporal profiles of the contaminant concentrations in both the aqueous and solid phases under a variety of conditions. Although somewhat preliminary in nature, the results indicate that the use of nucleophilic substitution reactions may substantially enhance the efficacy of elution processes for hydrophobic contami...