DPEP

Fig. 6.11 Characteristic frequencies from the long chain diblock (sample IV dPEP-hPEE) at 533 K (upper data) and 473 K (lower data). The solid lines represent the RPA predictions for the collective mode based on structural and homopolymers data. (Reprinted with permission from [44]. Copyright 1999 American Institute of Physics)...

Similarly, the results on dPEP-hPEE already exhibit deviations from the RPA-Rouse regime around QRg=7 (T=533 K). Thereby, the experimentally observed rates differ from the predicted rates by up to more than one order of magnitude (see Fig. 6.11). At the phase transition temperature (Todt=473 K), however, the effect is greatly reduced and a general slowing down of the fluctuations is found, though some deviations persist. 

EXAFS with [VO(OEP)] and [VO(DPEP)] gave V=0 and V—N bond lengths almost equal... 

Fic. 2. Porphyrin skeletal structure and metalloporphyrins found in petroleum (a) por-phine, (b) DPEP, (c) etioporphyrin, (d) Rhodo-DPEP, (e) Di-DPEP, (f) Rhodo-Etio. 

Asphaltenes may contain both porphyrin and nonporphyrin metals, depending upon the origin of the crude oil. Yen et al. (1969) characterized the vanadium complexes in a petroleum asphaltene by mass spectroscopy, optical spectroscopy, and ESR. Porphyrins (Etio and DPEP), acid-resistant porphyrin macrocycles of increased aromaticity (Rhodo), and nonporphyrins with mixed donor complexes were identified. Baker (1966) and Baker et al. (1967) extracted porphyrins from Boscan crude oil asphaltenes and also found Etio and DPEP as the two major porphyrin series. These homologous series range in molecular weight by 7 to 18 methylene groups. Gallegos (1967) observed by mass spectroscopy that asphaltenes and maltenes from a Boscan crude oil had nearly identical porphyrins in terms of mass distribution. 

Diffusion and adsorption studies with Boscan VO-porphyrin extracts and pure VO-TPP in C0M0/AI2O3 catalysts have been reported by Morales and co-workers (Galiasso and Morales, 1983 Morales and Galiasso, 1982 Andreu et al., 1981 Morales et al., 1984). The Boscan extract contained up to 30 wt. % vanadyl DPEP and vanadyl etioporphy-rin. Effective diffusion coefficients at 300°C in a catalyst with an average pore diameter of 150 A (A < 0.1) are on the order of 10-5 cm2/sec. Configurational effects are minor for this system. 

Fig. 33. a Volume fraction of deuterated poly(ethylenepropylene), dPEP (full dots) and pro-tonated PEP (open circles) versus depth, for a degree of polymerization N-2300 for both constituents, after a 4 h quench to T=294 K (Tcb 365 K). Profiles are obtained with the time of flight forward recoil spectrometry (TOF-FRES). The dashed line indicates the surface domain thickness l(t). b Plot showing the growth of the surface domain thickness (t) vs t1/3. From Krausch et al. [136]... 

Common Name Dipentyl phthalate Synonym DPeP, di-n-amyl phthalate... 

DPEP/etio Weighted av. mass (X) Band width (o-) Alkylation index (AI) Mode ... 

Immature free base or metalloporphyrin of DPEP series Metallated porphyrin under mild thermal stress Dealkylated porphyrin Transalkylated porphyrin Petroporphyrin... 

Mass spectrometric parameters of a typical immature metallopor-phyrin fraction are given in Table II. These parameters were used to interpret mass spectra of porphyrin samples recovered within known distances from a 13.5 m diabase sill (Table IV). The complexity imposed by temperature-controlled reactions (transalkylation and conversion of DPEP to etio series) can cloud trends within an individual parameter, but used together, the parameters permit definition of these reactions. As the sill is approached, tihe DPEP/etio ratio approaches zero for both... 

The distribution of vanadyl vs. nickel porphyrins is noteworthy (Table IV). An overview of the data from Site 368 shows that normal porphyrin diagenesis has progressed to the nickel DPEP porphyrin stage at + 15.87 m (IS). At greater depth, the normal process is interrupted by high thermal stress with concomitant formation of vanadyl porph)u is and decomposition of the native nickel porphyrins. Further below the sill (—8.39 m) only slightly altered nickel porph)rins, again predominantly... 

The combination of two techniques that measure independent components of the same geological environment permits more dependable interpretations than when used separately. The changes in mass spec-trometric parameters, particularly an increase in band width and A.I. and a decrease in DPEP/etio ratio, as well as changes in the EPR signal can be used collectively to discern onset through completion of thermally dependent reactions. While the mass spectral method gives a detailed resolution of many of the specific reactions involved, EPR provides a better overall view of maturation and covers some areas inaccessible to the former. 

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