Naphthenates, degradation

This is the breakdown of the percentage of paraffins, olefins, naphthenes and aromatics in gasoline. Fuel olefin content is closely monitored. High-olefin-content gasoline is unstable and can lead to various fuel problems such as deposit formation and color degradation. 

Over time, oxygen will react with fuel components to degrade the fuel into a viscous, sludgelike mass. Fuel components most susceptible to oxidation are olefins and alicyclic naphthenes. Paraffins and aromatics are less susceptible to attack but can eventually be consumed by the free-radical chain reaction process. 

Naphthenic acids and sulfur- and nitrogen-containing heterocycles and naphthenoaromatic compounds can all be found in distillate fuel fractions. Degradation through condensation type reactions rather than through free-radical-initiated polymerization can be more common in distillate fuel. Because of this, degradation products are often quite complex in nature and structurally diverse. 

Numerous bacterial and fungal genera have species able lo degrade hydrocarbons aerobically and the pathways of degradation of representative aliphatic, naphthenic and aromatic, molecules have, been well characterized in at least some species. It is a truism that the hallmark of an oil-degrading organism is its ability to insert oxygen atoms into the hydrocarbon, and... 

Cobalt complexes find various applications as additives for polymers. Thus cobalt phthalocyanine acts as a smoke retardant for styrene polymers,31 and the same effect in poly(vinyl chloride) is achieved with Co(acac)2, Co(acac)3, Co203 and CoC03.5 Co(acac)2 in presence of triphenyl phosphite or tri(4-methyl-6- f-butylphenyl) phosphite has been found to act as an antioxidant for polyenes.29 Both cobalt acetate and cobalt naphthenate stabilize polyesters against degradation,73 and the cobalt complex of the benzoic acid derivative (12) (see Section 66.4) acts as an antioxidant for butadiene polymers.46 Stabilization of poly(vinyl chloride)-polybutadiene rubber blends against UV light is provided by cobalt dicyclohexyldithiophosphinate (19).74 Here again, the precise structure does not appear to be known. 

The rest of the cyclic terpenoid sulfides are complex mixtures of partially degraded and isomerized derivatives of the terpenoid sulfides which elute on the capillary GC column as a broad, unresolved hump. On Raney nickel reduction this fraction yields a complex mixture of naphthenic hydrocarbons which cannot be resolved further by GC analysis. 

The oxidation of cyclohexane is accompanied by the oxidative degradation of the products. In other words, the products themselves undergo metal-initiated radical chain oxidation. For this reason oxidation is normally carried out at low conversions when the selectivity to the desired products is high. The catalysts used are a mixture of hydrocarbon soluble carboxylate salts of Co2+ and Mn2+ or Cr3+. Due to the better solubility properties, salts of long-chain carboxylic acids such as 2-ethyl hexanoic or naphthenic acids are favored. As already mentioned, the primary role of the metal ions is to act as catalysts for the initiation steps. In other words, the metal ions undergo redox reactions with 8.9 to give 8.10 and 8.11. 

Figure 3.10 Fractions of paraffins, olefins, naphthene and aromatic products from the catalytic degradation of plastics over spent FCC catalyst in a semi-batch reactor (400°C, P/C= 10, A/= 200 rpm) (a) HDPE (b) LDPE [70]. (Reproduced with permission from Elsevier)...

The paraffins, olefins, naphthenes and aromatics (PONA) distribution of liquid product with time on stream for thermal and catalytic degradation of waste HDPE at 430°C is shown in Figure 5.11. In the case of thermal degradation, paraffin and olefin components are the main products and aromatic componnds hardly appear, without change by increase... 

Figure 5.11 Fractions of paraffin, olefin, naphthene and aromatic products for thermal (a) and catalytic (b) degradation of waste HDPE at 430°C...

According to the increase of PS content in HDPE and PS mixture, in Eigure 5.15 the fraction of gasoline components in the liquid products was increased from about 85 wt% (pure HDPE) to about 98 wt% (pure PS) and the rest was kerosene + disel (C13-C24). No heavy oil (> 24) was detected. In the catalytic degradation of pure HDPE without PS, the major product was olefin components whereas the paraffin products as well as the aromatic and naphthene products with a cyclic structure were minor products. According as PS content in the reactant increased from 0 to 20 wt%, the fraction of paraffin... 

These oils are characterized structurally by a large number of paraffinic side chains (55% min. Cp), and thus are highly saturated. They excel in initial color. Compared to naphthenic and aromatic oils they are most resistant to oxidation and color degradation by ultraviolet light. Their resistance to oxidation increases as their molecular weight increases. SONPAR oils are de-waxed to low pour points, and their volatility is quite low compared to the naphthenics and aromatics, as indicated by their higher flash points. 

Oil accumulations can continue to undergo thermal evolution, depending on the depth of the reservoir and subsequent geothermal history. As noted in Section 4.5.2, oil becomes susceptible to thermal cracking at temperatures above 160-200 °C. For example, paraffinic-naphthenic oils (Fig. 4.22) are degraded to aromatic-naphthenic oils (with moderate S content, <1%), and aromatic-intermediate oils degrade to aromatic-asphaltic oils (with high S content, >1%). 

S-EB-S polymers are very compatible with paraffinic or naphthenic oils because of their lower midblock solubility parameter. As much as 200 parts of some of these oils can be added without bleedout. The articles have excellent heat stability, and the resistance of pigmented stocks to degradation from outdoor exposure is very good. Several compounds based on S-EB-S and S-B-S block polymers have been developed for special purposes. These include pharmaceutical goods, wire and cable coatings, and automotive applications (94). In pharmaceutical applications, the ability of some molded products to withstand steam sterilization as... 

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