Aromatic by-products

Dehydrogenation is considered to occur on the corners, edges, and other crystal defect sites on the catalyst where surface vacancies aid in the formation of intermediate species capable of competing for hydrogen with ethylbenzene. The role of the potassium may be viewed as a carrier for the strongly basic hydroxide ion, which is thought to help convert highly aromatic by-products to carbon dioxide. 

In this study, synthetic aqueous solutions of phenol were treated with ozone. The reaction of ozone with phenol was investigated at several conditions, such as different phenol and ozone concentrations, and contact times. Total Organic Carbon (TOC) and UV analysis of the aromatic by-products formed during and after the ozonation reaction were employed. The reaction rates calculated from TOC analysis were investigated. 

Figure 7. Effect of aromatics by-product price structure and naphtha feed price on U.S. ethylene production costs (1000 MM Ibs/yr ethylene production from naphtha feed premium value by-products)...

Figure 8. Breakeven prices for ethane feed vs. naphtha feed in the United States. Parameter is aromatics by-product value. 1000 MM Ibs/yr ethylene production premium value byproducts.

The increased reactivity of isocyanates, relative to carbon dioxide, was reflected in the wider range of cycloaddition partners. For example, terminal diynes as well as nontethered alkynes (e.g., 3-hexyne) were also successfully converted to 2-pyridones rather than undergoing rapid telomerization to aromatic by-products. Importantly, the cycloaddition of an asymmetrical... 

Fluorescence arises from aromatic by-products which, however, can be entirely separated by careful work. Pure ac-tetrahydro-/5-naphthylamine gives no color with diazobenzene sulfonic acid. 

Typical yields for complexes using HF and solid-bed alkylation routes are shown in Table 1. This table illustrates that the yields for the two routes are similar. For constant production of LAB, paraffin use is approximately equal for both the routes. The HAB byproduct stream consists of heavy alkylate (discussed in more detail in later sections). The HAB by-product is formed in both routes and depending on the properties, may be used in applications, such as heat transfer fluids, or as enhanced oil recovery surfactants in a sulfonated form. Both routes also produce some light products in the form of off-gas and cracked product from the dehydrogenation unit. The solid-bed alkylation route also produces an aromatic by-product stream (PEP Extract in Table 1), which consists of aromatics produced in the dehydrogenation unit. While aromatics removal is possible for the HF route, it is typically not practiced. Instead, the HF route has an acid regenerator bottoms stream, which consists of by-products extracted from purification of the HF acid. Both of these by-products are typically recovered for fuel value. In the table Case-1 represents an LAB complex that includes the Pacol , DeFine , PEP, and Detal processes all licensed by UOP LLC and hereafter referred to as Pacol/DeFine/PEP/Detal complex. Case-2 represents the Pacol, DeFine, and UOP HF detergent alkylation processes, all licensed by UOP LLC and hereafter referred to as Pacol/ DeFine/HF Alky complex. ... 

Olefins will alkylate with the aromatic by-product in the alkylation unit forming a heavy alkylate... 

The following discussion will cover specific aromatic by-products, which, unlike MPC and MPK, represent a true styrene yield loss, as they are not precursors of this product. These include 2-phenylethanol (teffl-phenylethanol, BPEA), ethylphenols and phenol, benzaldehyde, benzyl alcohol, and benzoic acid. 

Process oils Lightly refined base oils or highly aromatic by-product extracts from oil manufacture are used in various industrial products, e.g. plasticisers in automotive tyres, in printing inks and in mould release oils. 

PCP is frequently used as a wood preservative, herbicide and fungicide. It has additional uses in the leather and paper industry and an estimated 17,000 workers are exposed to PCP in the United States (O Malley et al. 1990). A retrospective review of 648 medical and personnel records from individuals manufacturing PCP between 1938 and 1978 demonstrated 47 cases of chloracne occurring in a 25-year period. These workers were exposed only to PCP for 2 years prior to their diagnosis. PCP was produced by direct chlorination of phenol, monochlorophenol, dichlorophenol and/or 2,4,6-trichlorophenol in the presence of an aluminum catalyst. During the commercial synthesis of PCP, varying amounts of polychlorinated aromatic by-products, including dioxins, are produced (O Malley et al. 1990). 

As the global demand for chemicals grows, so does that for aromatics, which constitute a significant fraction of the major building blocks of the chemical industry. As petroleum is displaced by natural gas, and as decreased gasoline refining (in favor of diesel [54]) limits production of aromatic by-products, the... 

Some interesting points emerged from this systematic study (i) steric hindrance on the diynes only had a little influence on the catalytic process (ii) when starting from unsymmetrical diynes, larger substituents were introduced in the 3-position of the formed pyridone (iii) under dilute conditions, unsymmetrical diynes were converted into pyridones without telomerization to aromatic by-products and (iv) aryl- as well as alkyl-isocyanates were reactive however, electron-poor arylisocyanate required a higher reaction temperature (80 °C). 

Heating to elevated temperatures led to dehydrogenation and the corresponding arene 6 could be obtained. The Diels-Alder reaction of terminal alkynes with 1,3-dienes was described by Matsuda et al. utilizing a low-valent rhodium catalyst at ambient temperatures to afford dihydroaromatic products such as 7 and the corresponding aromatic by-product 8 upon dehydrogenation (Scheme 13.4) [3],... 

---