Asphaltene precipitation is considered a precursor of the plugging of oil wells and subsurface equipment and is a topic of continuous interest among companies and academic institutions. Numerous models to predict asphaltene precipitation at reservoir conditions have emerged over the years, and some have been dropped for several reasons. One particular case is the utilization of cubic equations of state such as Peng–Robinson (PR) and Soave–Redlich–Kwong (SRK), which although are relatively simple to code and utilize, have not been as effective in predicting asphaltene precipitation as compared to other models such as the perturbed chain version of the statistical associating fluid theory equation of state (PC-SAFT EOS). However, we have found that after improving the crude oil characterization procedure to obtain a proper set of simulation parameters from the available experimental data, the cubic equation of state can show excellent predictive capabilities in modeling asphaltene onset pressure under gas injection. In this work, we develop a characterization methodology based on the contents of Saturates–Aromatics–Resins–Asphaltenes (SARA) that can be used with PR EOS. Several case studies with published data from six crude oils are conducted to assess the predictive capability of the new approach in modeling asphaltene onset pressure under gas injection. Comparisons are made with PC-SAFT EOS to highlight the advantages and disadvantages of each model. Also, the modeling approach is tested against high-pressure and high-temperature data from four wells from the Middle East that have not been previously published in the literature. The results indicate that PR EOS yields results that are at least as good as those obtained from PC-SAFT in predicting the onset of asphaltene precipitation in crude oil under various amounts and types of gas injection.

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The compound [PtMe2(bps)] (1; bps = bis(2-pyridyl)dimethylsilane) undergoes easy oxidative addition with bromine, iodine, methyl iodide, or methyl triflate to give [PtBr2Me2(bps)], [PtI2Me2(bps)], [PtIMe3(bps)], or [PtMe3(OH2)(bps)][OTf], respectively. The complex [PtIMe3(bps)] is slowly hydrolyzed in solution, with cleavage of the pyridyl–silicon bonds, to give [PtIMe3(py)2] and (Me2SiO) n . In contrast, oxidation of 1 with oxygen/CF3CH2OH, hydrogen peroxide, or dibenzoyl peroxide/H2O occurs with cleavage of a methyl–silicon bond to give [PtMe(bps)-μ-{κ3 N,N,O-OSiMe(2-C5H4N)2PtMe3][CF3CH2OB(C6F5)3], [PtMe3{κ3 N,N,O-(2-C5H4N)2SiMeO}], or [PtMe3{κ3 N,N,O-(2-C5H4N)2SiMeOH}][PhCOO], respectively. Mechanistic studies indicate that this methyl transfer from silicon to platinum occurs after oxidation to platinum(IV) and is induced by hydroxide attack at silicon.

The reaction of [PtMe2(dpe)], dpe=1,2-di-2-pyridylethane, with hydrogen peroxide occurs with ligand loss to give [{PtMe2(OH)2}n], but the reaction mixture then slowly yields crystals of [{PtMe3OH.PtMe2(OH)2}2][PtMe2(CO3)(dpe)]2, in which the central cluster has an unexpected structure based on a face-bridged double cubane.

The oxidation of the complex [PtMe(2)(bps)], bps = bis(2-pyridyl)dimethylsilane, by oxygen, hydrogen peroxide or dibenzoyl peroxide in the presence of water or alcohol gives the complex cation, [PtMe(3)(kappa(3)-N,N,O-HOSiMe(2-C(5)H(4)N)(2))](+), in a reaction involving easy cleavage of a methylsilicon bond.

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The title compound [PtMe2(bpe)], 1, bpe = 1,2-bis(2-pyridyl)ethane, is easily oxidized to give octahedral organoplatinum(IV) complexes, and the subsequent chemistry is profoundly influenced by the accompanying strain induced in the seven-membered Pt(bpe) chelate ring. In reactions with bromine or iodine, X2, the platinum(IV) complexes [PtX2Me2(bpe)] are formed initially, but they decompose primarily by reductive elimination of MeX to give ultimately the platinum(II) complexes [PtX2(bpe)]. When X = I, a minor reaction occurred to give the first example of metalation of a CH2 group of the bpe ligand. On reaction of 1 with HCl, the initial product [PtHClMe2(bpe)] undergoes reductive elimination of methane to form [PtClMe(bpe)]. In contrast, methyl iodide reacts with 1 to give [PtIMe3(bpe)], and this decomposes by loss of the bpe ligand to give the cubane [(PtIMe3)4] and not by reductive elimination. Finally, a new class of platinum(IV) double cubane clusters was obtained on oxidation of complex 1 either with hydrogen peroxide to give [Pt4(μ-OH)4(μ3-OH)2Me10], as a mixed complex with [PtMe2(CO3)(bpe)], or with oxygen in methanol to give [Pt4(μ-OH)2(μ-OMe)2(μ3-OMe)2Me10].

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