Process real-time composition

PAT was able to provide an insight into the process that gave information on real-time composition and concentrations. It is also a very valuable way to study reaction pathways and reaction kinetics for the purpose of understanding the reaction mechanisms. This has proven to be very important to developing an effective process control system. As the desired needs of measurement in the production environment became understood, technology has been developed to respond to this need, without... 

The objective ia any analytical procedure is to determine the composition of the sample (speciation) and the amounts of different species present (quantification). Spectroscopic techniques can both identify and quantify ia a single measurement. A wide range of compounds can be detected with high specificity, even ia multicomponent mixtures. Many spectroscopic methods are noninvasive, involving no sample collection, pretreatment, or contamination (see Nondestructive evaluation). Because only optical access to the sample is needed, instmments can be remotely situated for environmental and process monitoring (see Analytical METHODS Process control). Spectroscopy provides rapid real-time results, and is easily adaptable to continuous long-term monitoring. Spectra also carry information on sample conditions such as temperature and pressure. 

Other synonyms for steady state are time-invariant, static, or stationary. These terms refer to a process in which the values of the dependent variables remain constant with respect to time. Unsteady state processes are also called nonsteady state, transient, or dynamic and represent the situation when the process-dependent variables change with time. A typical example of an unsteady state process is the operation of a batch distillation column, which would exhibit a time-varying product composition. A transient model reduces to a steady state model when d/dt = 0. Most optimization problems treated in this book are based on steady state models. Optimization problems involving dynamic models usually pertain to optimal control or real-time optimization problems (see Chapter 16)... 

Cost reductions usually arise out of improvements to the process control for both continuous and batch processes. Process analyzers enable chemical composition to be monitored essentially in real time. This in turn allows control of the process to be improved by shortening start-up and transition times (for continuous processes) or batch cycle times (for batch processes). This is accomplished by improving the ability to respond to process disturbances, by enabling process oscillations to be detected and corrected, and by reducing product variability. Real-time monitoring of chemical composition in a process allows a manufacturing plant to ... 

First and most importantly, real-time NIR monitoring enabled real-time control of the process. For a given product, the molecular weight and end-group balance in the prepolymer exiting the front end or melt part of the process must be controlled at specified levels in order for the back end or solid-phase part of the process to successfully produce the intended polymer composition. In addition, the variability in prepolymer composition must be controlled with very tight tolerances to keep the variation in final product composition within specification limits. Since the process dynamics in the front end were more rapid than those in conventional PET processes, the conventional analytical approach involving off-line analysis of samples obtained every 2-A hours was not sufficient to achieve the desired product quality. 

Figure 5.28. In situ wet-ETEM of real-time catalytic hydrogenation of nitrile liquids over novel Co-Ru/Ti02 nanocatalysts, (a) Fresh catalyst with Co-Ru clusters (arrowed at C). The support is marked, e.g., at u. (b) Catalyst immersed in adiponitrile liquid and H2 gas in flowing conditions growth of hexamethylene diamine (HMD) layers (at the catalyst surface S in profile, arrowed) at 81 °C, confirmed by composition analysis and mass spectrometry, (c) ED pattern of HMD in (b) in liquid environments. Further growth is observed at 100 °C. The studies show that wet-ETEM can be used to design a catalytic process (after Gai 2002). (d) Scaled up reactivity data for novel Co-Ru/Ti02 nanocatalysts confirming wet-ETEM studies of high hydrogenation activity of the nanocatalyst (2). Plots 1 and 3 are the data for Raney-Ni complexes and Ru/alumina catalysts, respectively.

Coordinate Representation. A coordinate representation of a chemical substance is a recording of the atoms and bonds of that substance with an indication of their relative position in a plane. This coordinate representation provides a valuable form to facilitate on-line, real-time manipulation of the structure diagram and to store the diagram for subsequent composition in journals, handbooks, and search output. Because this representation is difficult to manipulate, it is typically converted to some other form for other information system functions. Farmer and Schehr [11] describe the approaches and capabilities used at CAS for representing and processing a coordinate form of structure diagrams. 

Chemical sensing is part of an information-acquisition process in which an insight is obtained about the chemical composition of the system in real-time. In this process, an amplified electrical signal results from the interaction between some chemical species and the sensor. Generally, the interaction consists of two steps recognition and amplification. One common example is the measurement of pH with a glass electrode (Fig. 1.1). 

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