Technical process development

Although the Langmuir theory of adsorption is used frequently for technical process development it is a crude approximation, as surface reconstruction frequently occurs. Adsorbed molecules change the structure of the surface layer and the catalytic properties of surface sites are not equal in the ability to bind chemisorbed molecules. The rate is dependent on spatial arrangement and the heat of adsorption depends on coverage (Figures 2.27, 2.28). 

Interestingly already in the 50-60s there was an understanding that the formulation of the rate expressions based on the original theory of Langmuir adopted by Hinshelwood and widely applied in this form for technical process development is a crude approximation. 

The synthetic method presented in Scheme 9.2 was scaled-up for industrial production of 1,000 tons/year of (—)-menthol. It represents a brilliant application of (—)-BlNAP as a chiral ligand in organometaUic catalysis [15]. The technical process development required, among other factors, enhancement of catalyst productivity, expressed as... 

The purpose of the systems engineering technical process Develop Specification Trees and Specifications is to translate identified needs into system solutions composed of specified elements of hardware and software that may be implemented... 

In this book we have decided to concentrate on purely synthetic applications of ionic liquids, just to keep the amount of material to a manageable level. FFowever, we think that synthetic and non-synthetic applications (and the people doing research in these areas) should not be treated separately for a number of reasons. Each area can profit from developments made in the other field, especially concerning the availability of physicochemical data and practical experience of development of technical processes using ionic liquids. In fact, in all production-scale chemical reactions some typically non-synthetic aspects (such as the heat capacity of the ionic liquid or product extraction from the ionic catalyst layer) have to be considered anyway. The most important reason for close collaboration by synthetic and non-synthetic scientists in the field of ionic liquid research is, however, the fact that in both areas an increase in the understanding of the ionic liquid material is the key factor for successful future development. 

The trends dcinoiistratc the capability of industiy to improve energy efficiency when it has the incentive to do so. Energy requirements can be cut by new process development. In addition, the amount of raw materials demanded by a society tends to decline as countries reach certain stages of industrial development, which leads to a decrease in industrial energy use. The accounting of trends in structural shift, material intensity, and technical energy efficiency... 

The ultimate goal of process development is to achieve feasibility where it is possible to produce amino adds on a large scale at a production cost per kg of amino add comparable to, or cheaper than, the processes currently used by other companies. If we presume that the technical performance (fermentation and recovery) are sorted out on a laboratory scale and scaling up looks promising, then it is time to find out whether it is possible to operate economically on a large scale. 

Faraday, in 1834, was the first to encounter Kolbe-electrolysis, when he studied the electrolysis of an aqueous acetate solution [1], However, it was Kolbe, in 1849, who recognized the reaction and applied it to the synthesis of a number of hydrocarbons [2]. Thereby the name of the reaction originated. Later on Wurtz demonstrated that unsymmetrical coupling products could be prepared by coelectrolysis of two different alkanoates [3]. Difficulties in the coupling of dicarboxylic acids were overcome by Crum-Brown and Walker, when they electrolysed the half esters of the diacids instead [4]. This way a simple route to useful long chain l,n-dicarboxylic acids was developed. In some cases the Kolbe dimerization failed and alkenes, alcohols or esters became the main products. The formation of alcohols by anodic oxidation of carboxylates in water was called the Hofer-Moest reaction [5]. Further applications and limitations were afterwards foimd by Fichter [6]. Weedon extensively applied the Kolbe reaction to the synthesis of rare fatty acids and similar natural products [7]. Later on key features of the mechanism were worked out by Eberson [8] and Utley [9] from the point of view of organic chemists and by Conway [10] from the point of view of a physical chemist. In Germany [11], Russia [12], and Japan [13] Kolbe electrolysis of adipic halfesters has been scaled up to a technical process. 

Bayer MaterialScience (Germany) in the Project "Dream Production" combines part of waste streams of coal-fired power plants, CO2, with the production of polymers. The target is the design and development of a technical process able to produce C02-based polyether polycarbonate polyols on a large scale. The first step was to convert the C02 in new polyols, and these polyols showed similar properties such as products already on the market and can be processed in conventional plans as well (Figure 22). 

To our knowledge, none of the developed SLP and SAP catalysts made their way into a technical process. Obviously, the possibility of using a supported liquid catalyst in a continuous liquid phase reaction is generally very restricted. The reason is that a very low solubility of the liquid in the feedstock/product mixture is enough to remove the catalyst from the surface over time (due to the very small amounts of liquid on the support). Even worse, the immobilised liquid film can be removed from the support physically by the mechanical forces of the continuous flow even in the case of complete immiscibility. 

A technical process was developed by Lonza for the Ir-catalyzed hydrogenation of an intermediate of dextromethorphan (Fig. 34.9) which was carried out on a > 100-kg scale [70]. Important success factors were ligand fine tuning and the use of a biphasic system chemoselectivity with respect to C=C hydrogenation was high, but catalyst productivity rather low for an economical technical application. Satoh et al. reported up to 90% ee for the hydrogenation of an intermediate of the antibiotic levofloxacin using Ir-diphosphine complexes. Best results were obtained with bppm and a modified diop in the presence of bismuth iodide at low temperature [71]. 

Since the first production processes were implemented by Monsanto and Sumitomo in the early 1970s, the number of production processes has grown rather slowly and comprises today (only) about 15 to 20 entries. Of these, 11 are medium to large scale, while all of the others are applied on a scale of 11 y-1 or less, and several of them are no longer in operation. On the positive side, many more processes developed to the pilot or bench scale are, in principle, ready for technical application. 

The book is directed to those persons involved in research, process development, pilot plant scale-up, process design, and commercial plant operations. It is important for technical people considering alternative process routes to know the potential hazards from the main reactions and from the unwanted side reactions in each case so that the hazards of reactivity are included in the factors reviewed in developing and selecting the final process route. 

The oxidation of carbohydrates at the nickel hydroxide electrode has been addressed in only a few papers [195]. Seiler and Robertson [197,198] developed a technical process, which allows the oxidation of 2,3,4,6-di-o-isopropylidene-L-sorbose (18, DAS) to protected gulonic acid (19). The acid, an intermediate of the vitamin C-synthesis, can be produced in a scale of two tons per day at the nickel hydroxide electrode. 

In the chloride process, developed in about 1960, the titanium in the ore is converted to titanium(IV) chloride by heating it to 800 °C with chlorine in the presence of carbon, which combines with the released oxygen. The purified chloride is then oxidised to titanium dioxide at 1000 °C and the chlorine formed is recycled. Technical problems arise because the oxidation of titanium(IV) chloride is not sufficiently exothermic to make the reaction self-sustaining but these can be overcome by pre-heating the reactants and by burning carbon monoxide in the reactor to raise the temperature. By careful control of the conditions, it is possible to produce pure rutile particles of a mean size of 200 nm. 

The first technical process involved heating phthalonitrile with copper bronze or copper(I)chloride at 200 to 240°C in copper pans. Several variations of this technique were developed in Germany prior to the Second World War. The reaction was performed either without or in the presence of a solvent. A basic distinction is commonly made between the baking process and the solvent process both may be carried out either by continuous or by batch technique. 

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