Robert B. Long

Factors influencing the separation of asphaltenes from heavy petroleum feedstocks

Abstract Several methods have been advocated as a means of asphaltene separation prior to characterization studies. However, each of these methods may suffer from some deficiency which renders it unsuitable for universal application. Elements of the separation, such as precipitant/oil ratio, precipitant-type and ageing time are important variables which can greatly influence the character of the asphaltenes. Recommendations are made for the separation of asphaltenes from heavy feedstocks which ensures minimal entrapment of ‘resin’ (i.e., precipitant soluble) material.

THE CONCEPT OF ASPHALTENES REVISITED

ABSTRACT Petroleum asphaltenes are defined as material insoluble in pentane or heptane and the nature of the molecular species that constitute asphaltenes has been a well researched subject over the past three decades. These investigations have led to a general consensus of the majority of researchers that asphaltenes contain condensed aromatic systems carrying alkyl, cycloalkyl, and heteroatom substituents. A variety of molecular models has been developed which have been used to explain the behavior of asphaltenes in feedstocks during recovery and processing operations However, an alternate concept introduced the idea that asphaltenes can be defined as a complex mixture of organic compounds of varying molecular weight and polarity. This allows asphaltenes to be described more fully in terms of their behavior during processes and properties in products, such as asphalt Thus, the concept can be used to explain, even predict, the incompatibility of asphaltenes with the other petroleum constituents as well a...

Coal Science: Basic Research Opportunities

More fundamental knowledge of coal (knowledge of its structure and its behavior during conversion processes) is essential before we can generate new technologies necessary for the efficient use of coal in the future. Herein are suggested specific basic research opportunities in the areas of coal characterization, gasification, combustion, and liquefaction, along with an assessment of the impact such research programs could have. Critical characterization needs include qualitative and quantitative determination of the chemical forms of carbon, oxygen, nitrogen, and sulfur and reliable methods for the measurement of surface area, pore volume, and weight-average molecular weights. Mechanistic studies aimed at increasing understanding of the thermal breakdown of the functionalities in coal, the behavior of coal in the presence of molecular and donor hydrogen environments, and carbon gasification and hydrocarbon synthesis reactions starting from carbon monoxide and hydrogen will lay the scientific foundation for the development of new processes for converting coal into clean usable fuels and chemicals.

A new technique for the acid/base separation of petroleum and coal-derived fractions

Abstract A new method for the acid/base fractionation of asphaltenes and other petroleum and coal-derived materials has been developed. This technique, which employs a strong, solid acid, has been shown to separate on the basis of acidity or basicity and to fractionate in a fashion similar to hydrogen chloride precipitation. In addition, the yields of fractions were shown to depend on the acidity of the separating medium. Basic and non-basic fractions were characterized by elemental analysis, e.s.r., n.m.r., interfacial tension, mass spectrometry, molecular weight, u.v.-visible spectrophotometry, and silylation. These data provide detailed information on the elemental distributions, functional group types, carbon and hydrogen types, and vanadium environments in the two fractions. The findings indicate that basic nitrogen is concentrated in the basic fraction while non-basic nitrogen and hydroxyl are mainly in the non-basic fraction. Although total nitrogen was concentrated in the basic fraction from coal asphaltenes, this was not the case for petroleum asphaltenes.

Spectroscopy and Asphaltene Structure

The spectroscopic (and chemical) methods used to determine the “structure” of petroleum asphaltenes, coal and coal asphaltenes have added valuable information about the character of these materials. Nevertheless, attempts to be too literal in the interpretation of the data and the continued insistence that these complex materials have a well-defined molecular structure is of questionable value to fossil fuel technology and is certainly beyond the scope of the available methods to derive such a formula. In fact, petroleum, coal and coal asphaltenes would best be described in terms of several structural types rather than definite molecular structures.