Process Chemistry Feeds, Products and Reactions

No commercial process is offered at this time for side chain alkylation of toluene with methanol for styrene and ethylbenzene production. In the literature the reaction is typically carried out at toluene to methanol molar ratios from 1.0 7.5 to 5 1 from 350 to 450 °C at atmospheric pressures. In some cases inert gas is introduced to assist vaporizing the liquid feed. In other cases H2 is co-fed to improve activity, selectivity and stability. Exelus recently claimed 80% yields in their ExSyM process at full methanol conversion using a 9 4 toluene methanol feed ratio at 400-425 °C and latm (101 kPa) in a bench-scale operation. This performance appears to be 

The catalyst consists of basic and acid sites in a microporous structure provided by zeolite and microporous materials [58-62]. Basic sites are provided by framework oxygen and/or occluded CsO. Acid sites are provided by the Cs cation and, possibly, additives such as boric and phosphoric acids. The addition of Cu and Ag increased the activity [63, 64]. Incorporation of li, Ce, Cr and Ag also has been shown to increase the styrene to ethylbenzene product ratio [65]. The reactivity of catalysts is sensitive to the presence of occluded CsO, which is in turn influenced by the preparative technique as shown by Lacroix and co-authors [64] and pointed out by Lercher [61]. 

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Since the reactor feed may contain inert species (e.g., nitrogen and solvents) and since there may be unconverted feed and by-products in the reactor effluent, a number of unit operations (distillation, filtration, etc.) may be required to produce the desired product(s). In practice, the flow of mass and energy through the process is captured by a process flow sheet. The flow sheet may require recycle (of unconverted feed, solvents, etc.) and purging that may affect reaction chemistry. Reactor design and operation influence the process and vice versa. 

To illustrate the concept of combining analytics to improve process understanding an example chemical reaction was run using a Cellular Process Chemistry Systems (CPC) continuous feed micro reactor. This microreactor is configured to operate as a small-scale chemical production plant. It has two reactant input lines and two solvent/wash lines. The thermally controlled microreactor block of the continuous feed reactor has a total internal volume of 50 pL. The reactor system contains active control for both temperature and feed rate of the two reactants. The system flows product from the microreactor block to a residence time module (12 mL volume) and then out of the reactor for product collection and work-up. 

Protein conformational stability Is not only of fundamental Interest for protein chemistry, but also relevant to questions of food safety and quality. High stability of proteinase Inhibitors may necessitate use of conditions for their Inactivation that denature other proteins first and lead to other reactions that have undesirable consequences for protein digestibility (Richardson, 1977). In discussing Inactivation of enzymes during food processing. Balls (1942) stated, "Until we know more about It, we shall probably overheat our products rather than underheat them, just to be safe. When we know more about It we may be able to moderate our enthusiasm and our technique". Basic studies on stabilities of protein enzyme Inhibitors and lectins, as well as enzymes, can contribute to development of methods that avoid overheating or underheating food or feed products. 

Traditional hydrocarbon conversion process models have implemented lumped kinetics schemes, where the molecules are aggregated into lumps defined by global properties, such as boiling point or solubility. Molecular information is obscured due to the multi-component nature of each lump. However, increasing environmental concerns and the desire for better control and manipulation of the process chemistry have focused attention on the molecular composition of both the feedstocks and their refined products. Modeling approaches that account for the molecular fundamentals underlying reaction of complex feeds and the subsequent prediction of molecular properties require an unprecedented level of molecular detail. 

Much of the complexity of these models is better considered bookkeeping than fundamental. That is, there are only roughly 10 different types of reactions or reaction operators underl5dng the process chemistry, which can comprise thousands of literal reactions because of the statistical or combinatorial explosion of matching these reaction operators with all of the feed and product molecules susceptible to each. A related simplification is... 

Research in analytical chemistry is clearly an area where automation has a significant role to play. It is important that research data is fuUy validated and as accurate as possible. While it is not always possible to automate entire processes, the use of automated carousels to feed samples into a reaction system is an obvious area to improve the quality and rate of generation of data. It wiU also allow the researchers to quickly validate their proposed methodology on real-world samples and optimize the performance characteristics. This naturally requires a very close relationship between the researchers and the ultimate end-users of the analytical product. Given a good return for the investment, I am sure that the initial investment to automate the research activity will be justified and forthcoming. 

In general, we have outlined how the conversion of isobutane on sohd acid catalysts takes place according to well-established carbenium ion transition state chemistry. The difficulty with using isobutane conversion as a probe of catalyst performance is that many combinations of oligomcrization// -scission processes with isomerization steps are possible, resulting in a wide variety of adsorbed species and observable reaction products. For example, the following products are observed from isobutane conversion in the presence of ultrastable Y zeolite at temperatures near 520 K (where the reaction is initiated by the addition of isobutylene to the feed) ... 

The appropriate selection of hydroprocessing catalysts depends on a careful inspection of the chemical properties of the feedstock and the expected products. For conventional distillate HDT (naphtha, kerosene, and gas oil), the specific surface area and the composition of the active phase are the most relevant features. CoMo-based catalysts are the traditional HDS catalysts used in the industry. NiMo catalysts are better for saturation reactions and HDN due to their higher hydrogenation power. Therefore, Ni-promoted catalysts are preferred over CoMo catalysts when the chemistry of the process proceeds through the hydrogenation route (i.e., gas oil feeds containing aromatic S- and N-compounds). NiW catalysts exhibit remarkable hydrogenation properties, but they are rarely used in... 

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