CA1324897C - Method and equipment for chromatographic analysis of hydrocarbons, and hydrocarbon refining operations using same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A sample of a hydrocarbon oil containing asphaltenes is chromatographically analyzed by forming a mixture of the oil with a weak solvent.
The mixture is passed in contact with a column of a stationary phase of find solid particles of fully functionalized material, followed by a weak solvent.
The solvent, after recovery from the column, is analyzed for aromatics by UV-absorption of UV
radiation in the range 200 to 400 nm. The absorbance of the UV light by the irradiated eluents across the UV wavelength range is monitored and the integral of absorbance is derived as a function of photon energy across the wavelength range. The magnitude of the derived integral in at least one time interval corresponding with at least aromatics in the eluent from the stationary phase is measured as an indication of the level of aromatics in the oil sample. The weak solvent may be followed by a strong solvent which, in turn, may be followed by a strong solvent which is modified by the addition of a hydrogen bonding solvent. the solvents are analyzed for saturates, aromatics, polar compounds and any asphaltenic materials by the combination of the UV-absorption measurement and a mass sensitive measurement which measures the combined level of the saturates, aromatics, polars and any asphaltenic compounds present. Equipment to perform the fore-going analysis is also described. The analysis can be used for evaluation of an oil and/or on-line regulation of an oil refining process.

Description

l- 132~897 FIE~D OF THE DISCLOSURE
.
The present invention relates to a method of chromatographic analysis of a hydrocarbon oil equipment therefor, and to a proceQs for refining or upgrading a hydrocarbon feed employing ~aid method of and equipment for, chromatographic analysiis The present invention r~lates in particular to a m~ehod ~o d~te~ine t~e level o~ components pres~nt in a hydrocarbon oil, e~pecially aromaeics Chromaeogràphy is a well-documented and widely used laboratory technique for separating and ideneifying the components of a fluid mixture e g a solution, and relieQ on the diffQrent relative affinities of the compon~nts between a stationary phase and a mobile phaso which contacts the station-ary phase ~ n a typical xamplQ of chromatography, the stationary phasQ isi a suitable particulate solid mat-~ial which ii -~ubstantially uniformly packed into tub~ so a~ to form a column of the stationary phase m~t-rial Th~ mobil- phase may be the fluid under investig~tion, or more commonly, a solution of the fluid und~r inv-stigation Th- solvent us-d in the solution is usually first passed through the column of solid stationary phas- and ther-after a small sampl- compri~ing a ~olution of the fluid under investigation is passe~ through the column followed by solvent alone The ~omponents of the fluid will have diff~rent affinitie~ for the stationary phase -` 1324897 and will therefore be retained at different regions along the length of the column for different times.
For some components, the affinity will be so slight that virtually no retention is evident while for others, the affinity might be so g~eat that the compon~nts are not recovered from the column even after considerable periods of time have elapsed since they wsre introduced into the column and subjected to the poteneial eluting properties of the solvent.

BACKGROUND OE THE INVENTION

Chromatography has been employed aQ a meanQ
of analyzing mixtures of hydrocarbons and other compounds found in petroleum oil.

In Petroanalysis 81, Chapter 9, i~ is disclosed that a hydrocarbon mixture combined with a -~olvent results in an eluate being recovered from the exit end of a chromatographic column which comprises the following types of molecular species, in order, namely: saturates (e.g. paraffins and naphthenes), olefins and aromatics. ~he remaining molecular species, which are (in general) polar compounds, have a relatively high affinity Çor the solid chromato-graphic material and can only be recovered in a reasonable time and reasonably completely by inter-rupting the flow of the solvent and substituting therefor a different solvent having a relatively high affinity for, e.g., heteroaromatic compounds~ The said different solv-nt is pa~ed through the column in a direction which is opposite to that of the first ~olvent so that after a reasonable time interval of this ~o-called back-flu~h, polar compounds (resins) are pre~ent in the back-flush eluate. The change in solvent from the first -- ` 132~897 solvent, pentane, to the second solvent, methyl t-butylether, ne~essitates the use of two different eluent detectors, i.e. one using refractive index and the other using ultra-violet absorbance at 300 n:n .
.
3ackflushing is inconvenient because of the mechanical complications involved in automating a chromatography unit utilizing it and also because it, in itself, does not ensure complete recovery of chemical species which are strongly ad~orbed by the stationary phase of the column.

In Journa~l of ~iquid Chromatography, 3(2), 229-242 (1980), a hydrocarbon mixture containing asphaltenes is subjected to chromatographic analysis only after mixing the mixture with hexane to precipi-tate asphaltenes which are separated by filtration and then determined gravimetrically. The hexane solution of the remaining hydrocarbons is ehen passed through a column of particles of u-Bondapak-NH2 where it separates into an eluent compri ing, initially, saturate~ and then aromatics, as determined by the refractive index of the eluent. Resin which is retained on the column is backflushed off the column and determined by difference. The separation quality of the column is maintained by flushinq it with a ~olution of l/l methylene chloride/acetone after every 20 samples and then regenerating with methylene chloride and he~ane for repeatable retention times.
Change~ in the refractive index of the eluents, indicative of the presence of reQpective chemical specie~, are monitored and correlated with absolute amounts of the chemical species by means of a Hewlett-Packard 3354~ computer using the so-called 132~897 "Zero" type met'hod. The drawbacks of this technique are that: (1) asphaltenes a~e determined gravi~e-~rically rather than by chromatography so t'nat the technique does not lend itself readily to automatic operation; (2) backflushing is employed, and not all the material in the sample fed to the column is recovered in the eluent as is evidenced by the stated need to clean the column periodically (further reference to this significant problem will be made hereinafter); (3) the refractive index detector which is employed has a response which varies with each type of molecular group such as paraffins, naph-thenes, aromatics and resins, and therefore cannot provide a uni~ersal response for a given mass which is independent of the nature of the sample of the feedstock which is being analyzed.

In Journal of Chromatography, 206 (1981) 289-300, Bollet et al., a rapid high-performance liquid chromatography tec~nique for separating heavy petroleum products into saturated, aromatic and polar compounds is described. A column containing a stationary phase of silica bonded NH2 ("Lichrosorb NH2n) is u ed. Two chromatographic analyses are needed in order to determine the composition of a ~ample. In the first analysis, saturated compounds are separated from aromatic and polar compounds, usinq h-xane or cyclohexane as the mobile phase. In the s-cond analysis, saturated and aromatic compounds are separated from polar compounds using 85 vol %
cyclohQxane~ 15 vol % chloroform as the mobile phase.
The eluents are monitored by differential refrac-tometry for saturated, aromatic and polar compounds, and by ultraviolet photometry for polar compounds.

` ` _ 5 _ 1324897 The proportions of saturated and polar compounds are said to be determinable by these ,~onitoring tech-niques and the proportion of aromatic compounds found by difference. However, the method described, in co,nmon with all other reports o~ high performance liquid chromatography (HPLC) for analysis of samples of heavy hydrocarbon oil mixtures, is limited by the lack of a means and method for quantitative and feedstock-independent detection and monitoring. Thu8, for both refractive index (RI) and ultraviolet (UV) detectors, "response factors" must be derived by separating samples of the feedstock on a larger scale, known in the art as "semi-preparative liquid chromatography~ and then yravimetrically weighinq the recovered analyte ~after removal of the solvent(s) added to the sample for the purpose of the chromato-graphic separation). Response factors are dependent on the nature of the feedstock and its boiling range, and it is therefore essential to perform the relatively large-scale separation to obtain accurate results with the HPLC analy~i~. Thus, the potential benefits of speed and increased resolution which should be pos~ible with HPLC have not heretofore been fully realized in practice. The technique of Bollet et al is compared with the method of the invention in the Comparaeive Example given hereinafter.

Reference is also made to Rlevens and Platt, J. Chem. Phys. 17:470 (1949~. Similarities are reported in the total oscillator strength for -electronic transition~ of cata-condensed aromatic~.
However, the article doe~ not relate to HPLC
analysis, nor does it recognize or suggest that a UV
detector operating in a specific wavelength range can be used in HPLC to derive an integrated oscillator strength output which quantifies the aromatic carbon - 6 - 132~8~7 in pet~oleum and shale oil feedstocks Furthermore, cata-condensed aromatics constitute only a minor fraction of the various aromatics in a hydrocarbon feedstock such as petroleum Other aromatics, including ~ara-condensed aromatics, alkyl aromatics, and thiophenic aro~atics which behave spectro-scopically differently from cata-condensed aromatics, are also generally present in a hydrocarbon feed-stock SUMM~RY OF THE INVEN~ION

It is an object of th~ present invention to provide a simpler, more comprehensive and more accurate method of, and equipment for, analyzing mixtures of compounds (particularly, but not exclusively, mixtures of hydrocarbons) by liquid chromatography, It is an object of the invention to provide a process for refining and/or upgrading hydrocarbons usinq novel chromatographic method and equipment to regulate and/or optimize said process It is a further objective of the invention to solve th- problem of how to quantify aromatics in hydrocarbon oil lt is another objective of the present invention to quantify not only the aromatics but also th- saturates and polars in the hydrocarbon oil and, further, to use this information, along with the qualitative levels of aromatics, to determine the extent o ~aturated Qubstitu~ion of aromatic and polar components of hydrocarbon oils .
~`

_ 7_ 132~897 Accordi.ng to the present invention from one aspect there is provided a method for the chromato-graphic analysis of hydrocar~on oil, co~prising the --teps of:

- ~a) passing a mixture o~ the hydrocarbon oil and a carrier pbase in contact with a chromatographic stationary phase over a first time interval so as to retain components of said hydrocarbon oil on said stationary phase;

~b) passing a mobile phase in coneact with said stationary phase after seep (a) over a second time interval, for eluting dif-ferent retained components of said oil from said stationary phase at different time intervals, and recoverinq the mobile phase which has contacted the stationary pha~e together with the components eluted from the stationary phase;

(c) irradiating the recovered mobile phase - with UV light having a wavelength range of which at least a part is within about 200 nm to about 400 nm over a sufficient ti~e period that the recovered components in the recovered mobile phase are sub-~ect~d to said irradiation, said mobile phase being substantially transparent to UV light within ~aid wavelenqth range;

.

d) monitoring the absorbance o~ said UV
light by said irradiated components across said wavelength r3nge and deriving the integral o~ absorbance as a function of photon energy across said wavelength range; and (e) measuring the magnitude of said derived integral in at least one selected time interval corresponding with the elution of one or more components The mo~ile phase and the carrier phase can be liquids or gases or supercritical fluids Usu~lly they will be liquids In a preferred way of performing the inveneion the recovered mobile phase from the stationary phase is irradiated with W light having a wavelength range within the range 230 to 400 nm A
scaling factor of 2 is applied to the derivation of the integral of absorbance so that the magnitude of Qaid derived integral of absorbance is doubled and said magnitude i~ mea-Qured in step (e) in a time interval corresponding with polar components in said mobile phase recovered from the stationary phase In a preferred way of putting the invention into effect the absorbance of said W light by said irradiat-d components is monitored using a diode array det-ctor Th- present invention is also concerned with calibration so as to determine the different ring-numbers of aromatics present in the hydrocarbon oil Calibration is achieved essentially by testing .
.

,~ .

. ., , ~ . . . . :. . .

9 13248~7 a sample of hydrocarbon oil according to the method as disclosed herein having known aromatic rings present, so as to associate the different times at which the different aromatics elute ~rom the station-ary phase with the ring-numbers of those different aromatics. This technique is described in ~ore detail below.

According to the invention from another aspece there is provided a process for refining or upgrading a petroleum hydrocarbon feed, in which samples of hydrocarbon oil produced in the process are each chromato~raphically analyzed by a method as defined above to detarmine the level present of at least one component in the oil, and in which the operation o the process is controlled in dependence upon the determined level present of said at least one component.

Usually but not nece~sarily the control of the operation of the process is ~uch as to oppose any rise in value of the level present of said at least one component above a predQtermined value.

One preferred way of performing the present invention provides a method of chromatographic analysi of a hydrocarbon oil, which may or may not contain a~phaltene-Q, comprising the steps of: -(a) for~ng a mixture of a sample of the oil with a weak solvent having a solubility param-ter in the range of rom 7.6 to 8.8 cal,.S cm-l.S;

' lo- 1~2~897 b) passins~ the said ~ixture in contact with a solid chro~atographic stationary phase selected from:

(i) a solid chromatographic stationary phase having surface hydroxyl groups of which substantially all have been substantially fully functionalized by at lQast one functionalizing group selected from at least the following functional-izing qroups: -NH2, -CN, -N02, a charge-transfer adsorbent, a charge-transfer ad~orbent func-tionalized with trinieroanilino-propane or tetranitrofluorenone, a homologue of any one of the fore-going, and a combination of two or more of ehe forgoing;

(ii) a solid chromatoqraphic stationary phase having a coronene capacity factor, with a mobile phase com-prisinq cyclohexane and 0.03 vol %
isopropanol, not exceeding 5.0 tpreferably 2.5 or less~; and (iii~ a solid chromatographic phase comprising a combination of fea-tures of (i) and (ii);

(c) passing in contact with the said solid chromatographic stationary phase a weak solvent (preferably cyclohexane) having a solubility parameter in the range of from 7.6 to 8.8 cal~S cm~l-5 for a first time `' '`

period a~t least during and after step (b) and reco~ering t~e weak solvent which has contacted the solid-stationary phase;

(d) monitorin~ the weak solvent recovered in step (c) fo~ a second time period com-prising at least a time interval after - the first time period to detect eluent comprising any aromatic hydrocarbons;

(e) monitoring the weak solvent recovered in step (c) to detect eluent comprising any saturated hydrocarbons simultaneously with step ~d)~ and after step ~d);

(f) passing in contact with the said Qolid chromatographic stationary phase a QtrOng solvent having a solubility parameter in the range of fro~ 8.9 to 10.0 for a third time period which is at lea~t after the second time period and recovering strong sol~ent which ha~ contacted the said stationary phase;

(g) monitoring the strong solvent recovered in seQp (f) to detect eluent comprising any heteroaromatic compound~, polar com-pounds and asphaltenic materials;

(h) passing in contact with the said solid chro~atographic ~tationary pha<e for a fourth time period which is at least after ehe third time period a strong solvent modified with a hydrogen-bonding solvent (~uch as an alcohol) which is miscible with the strong solvent, and recovering strong modified solvent which has contacted the said stationary phase;
and (i) monitoring the recovered strong modified solvent recovered in step (h) to detect any eluen~ comprising moieties selected ~ from at least one of the group consisting of pola~ compounds and asphaltenic materials Preferably, the change from ~ea~ solvent to strong solvent is e~Fected over a finite poriod of time, i e there i~ a progressive change in solvent rather than a step change It is found that ~uperior separation is achieved in this way With reference to seep (h), the strongly polar solvent and/or hydrogen-bonding solvent preferably has the following propertiQs li) It must be capabl~ of dissolving polar compounds and asphal-tenes of th~ typ~s found or anticipated in the sample. At a rule of t~uab, a solvont or combination of solvonts having a polarity between those of toluene and carbon disulfide will satisfy this requirement, and dichloromethane is a convenient and preferrod ~olvent meeting this criterion (ii) It mu~t be capable of displacing the most polar heavy oil molecules from the solid adsorbent material ~he addition to the solvent of one or more alcohols miscible therewith provides this property, and when the solvent is based on dichloromethane, a convenient and preferred alcohol is isopropanol in volume con-centrations in the range of from 1 to 50~, e g 10 vol % or thereabouts (iii) If ultraviolet spec-troscopic analysis is ~mployed for mass detection, as - ~,. . ~
' ' : . ` ;. ~

` -- 13 _ 1324897 explained herein, the solvent ~or combination solvent) must be transparent to uv radiation in the wavelength r~nge employed. (iv) If a ~ass detection step is used (e.g., gravimetric, flame ionization, inter alia) in which the ~enoval of the solvent is necessary, the solvent must be relatively volatile for easy separation of solvent-free eluent, and the solvent must not associate too strongly with polar molecules in the eluent.

Preferably, step (j) is effected after step li) by passing a weak solvent in said one direc-tion in contact with the said stationary phase ~or a fifth ti~e period which is at least after the fourth time period, said weak solvent prefe~ably being the same as, or fully miscible with, the weak solvent of step ~c). Preferably after step (j), steps (a) to ~j) are repeated as described herein using another oil sample in step ~a).

The monitoring for eluents in steps (e), ~g) and li) is effected by W absorption employing UV
of selected wavelength(~), the solvents used in steps la), (c), (f) and th) preferably being transparent to UV of the ~elected wavelength(s). A highly signifi-cant benefit of employing UV absorption to monitor the eluent~ is that it can be employed for the accurate determination of the mass of aromatic carbon th-rein, as described hereinbelow~

Aromatic compounds of differing ring numbers and ~ubstitution ~how differing ultraviolet absorbance ~pectra. It i~ therefore not possible to choo~e a sinqle wavelength to determine all of them.
Each aromatic type haa a different intrinsic absorb-ance per unit molar concentration (the extinction coefficient) at: any given wavelength, and in a complex mixture it is not possible to assign a constant resQOnSe factor which will relate t~e absorbance to the ~ass eluting from the colu~n To overcome this limitation, a preferred way of perform-ing the invention has been devised. The new method utilizes full UV absorbance spectra in the region 200 to 400 nm. Spectra can be taken rapidly on the oil components eluting from a chromatography column with a diode array detector. There have been published examples of these detectorQ in oil analysis (c.g., by K.N. Jost et al in Erdol und Kohle-Erdgas -~etrochemie 37(4):l78(19a4)), but no reports of the quantitative measurement of aromatic carbon from UV
spectra. It has been discovered by the present inventor that a mathematically derived quantity, termed the integrated oscillator strength ~Q), calculated from tbe full absorbance spectrum is directly proportional to the level of aromatic carbon. The quantity Q is defined as:

Q t A () here: A ~ absorbance photon energy and the integral is taken over the region from 200 to 400 nm.

To derive the mass of aromatic carbon ~luting from tbe column in any time period which defin-s an oil component, the quantity Q is simply integrated ovQr that time period and then multiplied by an appropriate constant which reflects the light pathlength, integration time, etc.

~ ~ .

- ' -- 15 - 132~8~7 one way in which Q can be determined will now be described, in the case of a diode array detec-tor. Each detector produces an output signal proportional to the intensity, I, of the light it detects. A computer converts each detector output to a quantity A(~) -- i.e. absorbance, where ~ repre-sents wavelength -- where A ~ -loglo(I ), Io being the intensity of the UV source. The bandwidth ~A, received by each individual detector in the detector array, is the same (e.g. 2 nm) but the wavelength varies ~by an increment or decrement equal to the bandwidth) from each detector to the next.
Therefore, the computer multiplies the guantity A(~) by a weighting factor E (A) ~ hc [A - 0.5 (~A) A + 0.5 (~A) and sums across the UV spectrum to derive the integrated oscillator strength Q.

~ he validity and accuracy of this approach has been establiQhed by comparison to model compo-nents which have been injected at known weights into the chromatography system~ Some examples are given in ~able I.

e 13 2 ~18 9 7 "~ o ~

3 3~ ~s - Q

K S ~ a z O

c~ ~. ,~ O O c~.

The measured integrated oscillator strength (Q) on polar compounds is multiplied by ~
factor of about 2.0 (or tbe integrated oscillator strength is multiplied by a factor of aoout 2.0 be~ore it is ~easured) to derive the aromatic carbon because a part of the spectral region cannot be measured due to solvent (e.g., dichloromethane) absorbance. The accuracy of the integrated oscilla-tor strength method or technique ha~ also been demonstrated on whole oils by comparison to the determination of aromatic carbon by Nuclear Magnetic Resonance (NMR~ in various oil samples, as shown in Figure 1 o~ the drawings wherein the abscissa gives the 13C-~MR results in units of weight percent aromatic car~on and the ordinate gives the predicted values in the same units, the predicted values having been derived from the inteqral of A ~ d E. The straight-line graph illustrating the linear corre-lation of the NMR values and the integrated oscillator strength values re~prèsents parity. The data fits the parity line even for oils of very di~ferent degree of saturated -QubQtitution, such a-~vacuum qas oils and coker ~as oils, and oils of very different polar content, such as hydrotreated gas oils and vacuum residua. The theoretical basis for the independence of thi-Q quantity to aromatic type is not completely understood.

The total mass of components eluting from th- column may be determined by, for example, dif-ferential refractometry, solvent evaporation followed by flame ionization of the oil, or ~olvent evapora-tion followed by light ~cattering off the remaining oil droplets. There are commercially available detectors for each of these procedures. Differential refractometry has the drawbacks that the refractive .
.

index of a component varies with its aromaticity and with the degree to which the saturated carbon is paraffinic or naphthenic These dra~backs lead to ~he need to use feedstock-type-dependent response factors to relate the measured refractive index to the mass of component eluting, Accordingly, it is preferred, according to a preferred way of performing the invention, to use solvent evaporation followed by either flame ionization or light scattering to measure the total mass of oil components indepen-dently of the feedstock composition or the feedstock type Tn the case of flame ionization, the parti-cular instrument used (the flame ionization equipment described by J B Dixon of Tracor Instruments in paper No 43 at the 1983 Pittsburgh Conference on Analytical Chemistry) has been found to cause some volatilization of lower boiling range oils along with the solvent evaporation, so it was most useful with vacuum distillation residua In the case of light scattering, ie is recognized that the light scatter-ing response is a complicated function of the mass of solute eluting, and an appropriate calibration func-tion must be derived A recent publication ( ~ . H . Mourey and L E Oppenheimer, Analytical Chemistry, 56 242~-2434(1984)) addresses the use of a light scattering detector for HPLC of polymers It ha-~ been demonstrated by the inventor of the present inv-ntion that for oil system~, this detector may be u~ed to m-aQure total component masses independently of feedstock type Th- calibration functions are l9 1324897 Mass = Kl * (response)X (2) where x ~ 1 at low response intensities; and Mass s K2 * ( response)X - (3) where y 3 1 at high response intensities.
Kl and K2 are constants The combination of using one detector to measure aromatic carbon mass and another to measure total mass allows the saturated carbon substitution to be determined by difference (or ratio). It is believed that this is a totally new concept in HPLC.
Its validity has been established by comparisons of HPLC to mass spectroscopic analyses and by showing that the aromaticity of individual aromatic and polar components increases as expected during thermal treatment.

The invention, according to a preferred application, provides a method of evaluating the quality of a hydrocarbon mixture comprising analyzing at least one sample of the hydrocarbon mixture by the method as herein de~cribed and thereby determining the proportions of species ~elected from at least one of the following: saturates, aromatics, polynuclear-aromatics, polar compounds, asphaltenes and a mixture comprising at least two of the foregoing. The hydro-carbon mixture may be a feedstock for a refining process or an intermediate processed oil between two refining ~teps. The evaluation performed by this prefQrred method of the invention enables the refining process or processe~ to be adjusted as nece~sary (within their permi~sible operating limit~) to produce a product and/or intermediate product .

having a composition which matches or closely approximates to the oQtimum specification ~or the product and/o~ inter~ediate product.

The invention, in one application, also provides a ~rocess for refining or upgrading 3 petroleu~ hydrocarbon feed containing as~haltenic materials in which the feed is passed to a fractiona-tion unit having a temperature and pressure gradient thereacross for separation into components according to the boiling ranges thereof, said components being recovered from respective regions of the fractiona-tion unit and including a gas oil component boiling in a gas oil boiling range Which iS recovered from a gas oil recovery region of the unit, wherein discrete samples o~ gas oil fraction are taken from the recovered gas oil fraction at intervals and each analyzed by the method as herein described, and wherein a signal representative of the amount of asphaltenic material present in each sample is generated and employed to modulate the operation of the Eractionation unit ~o that the amount of polar component in the gas oil component is maintained below a predetermined amount.

The invention, in another application, further provides a process for refining or upgrading a petroleum hydrocarbon feed ~e.g., boiling in the gas oil boiling range) in which the feed is passed to a catalytic cracking unit and converted to cracked product~ including upgraded hydrocarbon materials, wherein discrete samples of the feed passing to the catalytic cracking unit are taken at intervals and each analyzed by the method as described herein, and a signal representative of the amounts of polar components and aromatic components having at least : ~ ............ ,.. : ~

.

- 21 - 1 32~8g7 three rings ("3~ring aromatics") is generated, and the feed is either blended with a higher quality ~eed or subjected to a catalytic hydrogenation treatment or both blended and catalytically hydrogenated if and/or when said signal corresponds to amounts of 3+ring aromatic components and polar components in excess of predetermined amounts, the amount of blending and/or the intensity of said catalytic hydrogenation treatment bein~ increased and ~ecreased with respective increases and decreases in the magni-tude of the said signal.

The invention, in yet another application, also provides a process for refining and upgrading a petroleum hydrocarbon feed containing undesirable contaminating components selected from asphaltenic materials, aromatic components containing at least three conjugated aromatic rings ("3~aromatics"), polar components and mixtures of at least two of said contaminating components comprising the steps Of mixing a stream of the hydrocarbon feed with a stream of a selective refining agent at ~elected refining conditions and separately recovering from the resulting mixture (i) a hydrocarbon raffinate stream having a reduced content of polar components and aromatic components; and tii) a stream of a mixture containing solvent and at lea t one of said contami-nating components, wherein discrete samples of the raffinate stream are taken at intervals and each analyzed by the method as herein described and wherein a signal representative of the amount of contaminating component is derived, the signal being employed directly or indirectly to vary or resulate - 22 - 1~2~897 the said refining conditions so as to maintain the amount of contaminating component in the raffinate below a selected amount.

DESCRI5~TrON OF THE DRAWINGS

The invention i~ now further described by way of example with reference to the drawings in which:

Figure 1 is a regression-analysis graph of t~e weight percent of aromatic carbon in various hydrocarbon oil samples by NMR (on the abscissa) versus the predicted total aromatic carbon weight percent in tbe eluent as derived from the integrated oscillator strength; `

Figure 2 is a schematic diagram showing one form of apparatus for use according to one way of performing the method of the invention;

Figure 3 is a graph showing compositicnal data on the ordinate versu~ time on the abscissa for an analy~is carried out using the apparatus of Figure 2;

Figure ~ shows in graph~ (a), (b) and (c) absorbance versus time of eluents recovered during a repetition of the method described by Bollet et al in J. Chromatography ~1981), 206 289-300; and .

Figure ~ is a chemical engineering flow sheet of a process and regulating equipment therefor, wherein the regulating equipment embodies apparatus for ~se according to one way of perfor~ing the Det~od of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the particular description herein, only those features which have a direct bearing on the disclosed embodiments of the invention will be m~ntioned; features which will be well-known to those skilled in the art will not bè referred to.

Figure 1 was obtained by NMR determiQations and integrated oscillator strengths ~ on sample~ of 6 virgin gas oils lVGO), 1 heavy coker gas oil (H~GO), 3 deasphalted oils ~Dao)~ 5 heavy Arabian vacuum reQidua (HAVR) fractions and 4 vacuum residua, and the predicted aromaticitie~ were obtained from ehe integraeed oscillator strengths. The measured polar aromatic cores were multiplied by a factor of 2Ø It is evident that this approach to UV detec-tion provides a quantitative measurement of aromatics which is independent of feedstock type. The need for response faceors is thus eliminated.

Referring now to Figure 2, the apparatus 10 compris-s a chromatographic column 11 having an internal diameter of 4.6 mm and an overall length of 25 cm. The column 11 i~ packed by the well-known slurry method with a commercially available ~tation-ary phase consi-Qting of substantially fully NH2-functionalized silica in finely divided form, ,~
- -, . . . .

-^ - 132~897 having a mean particle size in the range suitable for high performance liquid chromatograpny ( HPLC), e g s to 10 um A conduit 12 extends from the upstream end of the column to a sample injection valve 11 and samples are injected into the valve 13 and conduit 12 from a sample injection line 14 a solvent pipe 15 extends from the upstream end of the valve 13 to the downstream end of a solvene mixing chamber 16 which is connected to two solven~ tu~es 17, 18 to receive different solvents -~ro~ respective suitable pumps 19 20 Thè opera-tions of the pumps 19 20 are regulated by micro-processors lnot shown) Each pump 19 20 is connected to recei`ve a respective solvent from a source thereof ~not shown) A third pump may optionally be added or a single pump with propor-tioning inlet valvés to different solvent reservoirs may be employed At the downstream end of the column 11, a conduit 21 conduc~s solvent(s) and eluents from the colqmn to a variable wavelength ultra-violet detector 22 and ehencefrom to a mass-sensitive or mass-responsive detector 23 and thereafter to a sample disposal point and/or recovery and~or separation unit (not Qhown) Tbe ma~s-sensitive or mass-responsive detector 23 may be a deteceor which monitors or produces a signal in respon-~e to refractive index flame ionization or light-scattQring ~after evapora-tion of solvent from the sample) ., , ~,~

' - 2s - 132~897 During the analysis, the ~icroprocessor controllers regulate operation of the two pumps 19, 20 to maintain a substantially constant flow rat~
t:~rough colu~n Ll of from o.s to 2.0 ~1 ~er minute.
Initillly, a weak solvent is employed whic~ is substantially transparent to uv radiation and has a sufficient solubility parameter to dissolve all components of the sample to be introduced into the column but of wbich the solubility parameter is not so high that relatively sharp discrimination between diEferent chemical types in the sample by HP~C will nGt be possible. ~he solubility parameter, delta, is the square root of the quotient of the energy of vaporization divided by itS molecular volume ~see C.A. Hansen et al., Encyclopedia of Chemical Technology by Kirk and Othmer, 2nd edition, Supplement, pages 889 to 910~; i.e. delta (Ev/Vm)0~5. The solubility parameter of the weak solvent should be in the range of from 7.6 to 8.8 cal.0-5cm~l-5 and a preferred weak solvent is cyclo-hexane which dis~olves all hydrocarbon components of hydrocarbon oil sample-~ without causing precipitation of asphaltene~. Other weak solvents which may be used in place of cyclohexane are nonane, decane, dodecane, hexadecane, eicosane and methylcyclohexane, and combinations of at` least two of the foregoing.
Preferably, the solvent used is cyclohexane containing a trace proportion of a polar solvent in order to maintain the adsorption properties of the stationary pbase at a constant value by deactivating any re~idual silanol groups on the stationary phase.
~he preferred polar -~olvent for this purpose is an alcohol, particularly 2-propanol, and preferably a , ,., ' ' ' '' ' .
'~ ' ' . ' . ' , .

- 26 - 132~897 mixture of 99.99 volumes cyclohexane and 0.01 volumes 2-propanol is pumped by pump 19 to the column 11 during a first time period of operation.

During the first time period of operation, a sample of the hydrocarbon which is to be analyzed is passed via line 14 into injector valve 13 at a datum time where it co-mingles with the weak solvent from pump 19 to form a substantially uniform solution which is free of precipitated material such as asphaltenes. The magnitude of the sample is not critical within the limits which are conventional for high perfonmance li~id chromatography, and a sample of 0.4 mg is usually satisfactory. The resulting solution passes into the upstream end of the column 11. In an alternative embodiment, a sample comprising a solution of the hydrocarbon in which the solvent is a weak solvent (conveniently but not necessarily the same solvent as is delivered by the pump 19) is introduced through injector valve 13 as a "slug" which is propelled through the column by urther weak solvent from pump 19.

The liquid which emerges from the downstream end of the column 11 is constantly moni-tored in W detector 22 and mass-sensitive detector 23. Th- W-monitoring detector 22 and mass-sensitive detector 23 operate by the principles described herein. The response of these detectors may be digitized and automatically converted into levels or proportion~ of the various components in the oil sample.

The response in the mas~-sensitive detector will typically start before the absorption of UV is detected due to the lower retentivity of saturated 13248~7 hydrocarbons than aromatics by the stationary packing material in the col~mn 11 and will tend to overlap in time the UV absorption ~eriod as some aromatic hydro-carbon ~olecules ~ass throug;~ 'he UV detector at the same time as more diffusive Iromatic molecules are passing through the Dass-sensitive detector.

The diffusivity or rate of elution of molecules containing aromatic rings, as manifested by their rate of passage through the column 11, depends to a major extent on the number of aromatic rings in the molecules~ Molecules having a single aromatic ring are eluted relatively rapidly while molecule containing two or more aromatic rings are eluted more slowly. Thus, by calibrating the column 11 with molecules containing different numbers of aromatic rings, it is possible to characterize eluted mole-cules in accordance with the time they have taken to pass through the column 11. Calibration is suitably effected with, e.q. toluene (one aromatic ring), anthracene (three condensed aromatic rings) and coronene ~six condensed aromatic ring~ he cali-bration may be effected with additional multi-ring compounds and/or different multi-ring compounds.

During operation of the method as disclosed herein, ~ub~tantially all single-aromatic molecules will ~lute wiehin a time span comparable with that of toluene, three-ring molecules will elute within a time ~pan comparable with that of anthracene after the time ~pan of the single-aromatic molecules, and ~ix-aromatic ring compound~ will elute after the time ~pan of anthracene during a time span comparable with that of coronene Molecules having numbers of aromatic rings between those of toluene and anthra-cene and between anthracene and coronene will elute after time periods between the respective pairs of molecules used for the calibration When substantially all the saturated and aromatic hydrocarbon mol~culQs havo been eluted from the column 11 by th~ weak solvent, a-~ ~videnced by a declin~ in th~ W absorption and refractiv- ind~x to virtually th-ir base values with the ~olvent only, a strong solvent (i e a solvent having relatively high polarity) is passed into the colu~n by pump 20 at a progressively increasing rate while the weak solvent is pumped by pump 19 at a corrQspondinq progressively rQducing rate so that the total volume-rat~ of solvent is substantially unaltered After a selected third time period, thQ w~ak solvent is totally absQnt and the only solvQnt pas~ing to th- upstrea~ ~nd of the column 11 i~ the strong solv~nt Th~ <trong solv-nt ha~ a solubility param t-r in th- rang~ o~ Srom 8 9 to 10 0 cal0 5 c~-1 5 and i~ transparent to W A suitable strong solvont mu~t bo tran~parent to W radiation at as low a wavel ngth as possible to facilitate c~lcul~tion o~ the o~cillator strenqth The strong solvent must have a polarity between those of toluen- and carbon disulfide, and is suitably dichlorom thane The dichlorom thane may contain an alcohol in ord-r to anhanc- it~ ~bility to elute polar high mol~cular w~ight molQcules~ Suitably, the alcohol i~ 2-propanol, and th- ~trong solvent may consi~t of 90 ~ol% dichlorom-thane and 10 vol%
2-propanol In a modification of the apparatua of Figure 2 as so far described, pumps 19 and 20 may be employed respectiv~ly for passing the weak and ~trong solvents (e g , cyclohexane and - 132~897 dichloromethane) via respective tubes 17 and 18 into the mixing chamber 16, and there may be an addi-tional tube 18a for conducting the alcohol or other high polarity eluting material from a respective third pump (not shown) to the mixing chamber 16 The third pump is preferably microprocessor con-troll2d in relation to pumps 19 and 20 according to a predetermin~d s~qu~nce or program in a manner which is known in the art If the alco~ol or other hiqhly polar solvent modifier has not been introduced with the strong solvent in the ~hird time period, it is introduc~d over a fourth time period te g of five minutes or thereabouts) In either case, the alcohol or other highly polar solvent modifier is introduced in steadily increasing rate with a correspondingly reducing rate for tho strong sol-vont T~o ~odifi d ~trong ~olvent only i~ passed into th~ ~olumn 11 for a flfth tim- period to elute highly polar molecule~ from the column The elution of polar ~olecule~ is detected by both detectors ~he polar ~olecul-s of a typical hydrocarbon sample which contain~ a~phalt~nQs are virtually completely ~lut~d within a fifth time period of about 10 min~to~, according to the relatively rapid decline in W ab~orption atter 3 to 10 minute~ from the time wh-n ~trong moditi-d ~olv-nt only i~ pumped into the column ~ hen the elution of polar molecules is substantially completed, the strong solvent is progres~ively replaced by the weaX solvent (i e 99 99 vol% cyclohexane with 0 01 vol% 2-propanol) ~, ' over a sixth time period. Suitably, the sixth time period can be in the ranqe from 1 to 10 minutes.

The weak solvent may be replaced by first interrupting the addition of the alcohol modifier to the strong solvent and then by progressively replac-ing the strong solvent by the wea~ solvent. The next hydrocarbon sample may then be passed into the column from injector valv~ 13 with woak solvent.

Reference is now made to Figure 3 o~ the drawings in which the upper graph 30 -ahows the variation wi~h ~im~ of thQ rèsponse o~ the material passing t~rough the mass-sensitlve evaporative light-scattering detector 23: and the lower graph 31 shows the variation with time of the W oscillator strength of the material passing through the W
detector 22.

on th~ abscissa, the time is given in 3-second intervals or increm-nts th~reinarter termed "channel~ from tim to time) from a datum time '0' which is 40 channels after th sample is in~ected.

Tho sample was 0.4 mg of heavy Arab vacuum rosiduum. The solvents werQ pumped by pumps 19, 20 Qith~r togQth-r in progressively changing propor-tion~ or individually to provide a constant solvent flow rat~ through th~ column 11 o~ 1.0 ml per minute.

In the initial tim~ intarval preceding the datum timQ, weak solvent only was passed from the pump 19 at the afor~said rate of 1.0 ml/minute, and the light-scattering signal and W oscillator strength were at constant 1eVQ1S during this time interval. The weak solvent alon~ was delivered by 132~897 pump 19 through injector valve 13 for 7 minutes, from the time of injection of the hydrocarbon oil sample Immediately thereafter, the strong solvent was progressively substituted for the weak solvent at a uniform rate (i e linearly over a period of 2 minutes) The strong solvent alone was then delivered by pump 19 through injector valve 20 for a period of 4 0 minutes, at which time it was progres-sively replaced over a period o~ 0 1 minutes by tho modified strong solvent whose flow was thereafter maintained for a period of 12 9 minute~ ~n each case, a tima lag arises, from the time of passing through th~ in~ection valv~ 13, for the sample or each solvent to reach tha column and pass through it At tha datum time, -40 channels, the 0 4 mg sample of vacuum rosiduum was in~ected from sampl- in~ection line 14 into in~-ction valve 13 Due to th- tim lag, for th first 40 channels thereaft-r noither detector showad any d-viation from tha st-ady basaline b-for ~ample in~ection After 11 channels later, the light-sc~ttering signal as detected by detector 23 showed changes which com-pri~od a sharp increase in response from the ba~olino 32 to a maximum point tpoint 33) followed by a progressive decrQase towards the solvent-only valuo, interrupted at int-rvals by one or mor~
incr-a~-~ in rosponse The light-scattering ~ignal r spondod to the olution of 40 microgra~ of b-nz(alpha)anthracene which was included as an int-rnal standard, and indicated by peak 34 The olution o~ polar h~teroaromatic spocios due to a solvent change to dichloromethane was indicated by peaX 35, and the elution of strongly polar hetero-aromatic SpQCioS due to a chango in solvent to 90%

1 32~897 dichloromethane, 10% isopropanol was indicated by peak 3 6 .

With reference to the w oscillator strengt~ graph 31, it will be observed that an increase in absorbance from the baseline began at about 15 channels and attained a peak (point 37) at about 24 channels The peak value of absorbance was maintained for a short time and therea~ter main-tained a height above the baseline indicative of the aromatic~ eluting at each particular timQ At point 38, the response of the internal standard is appar-ent At 219 channels, corresponding approximately with th~ time of complete substitution Or strong solvent for weak solvent in the column, there was a steep rise in W absorbance which rose to a peak (point 39) due to polar compounds and thereafter exhibited a relatively rapid decline The small additional peak 40 represents elution of highly polar compound~ in the strong solvent .
Wh n the strong solvent, dichloromethane, wa~ modified in the column by the addition of 10 vol% isopropanol, the additional peak was observed and recorded Finally, th~ detector response r-turn d to a value very clo~e to its initial ba~-lin~ at point 42, ~t which time data collecting wa~ caa~-d T~- relation~hip of the variations in light-~c~tt~ring r-~ponse and W o~cillator strength with solv nt type i9 as follow~ th- initial change in light Qcatt-ring correspond~ with the elution of saturated hydrocarbons and a small proportion of aromatic hydrocarbons The saturated hydrocarbons cause th- peak at point 33, and the decline in light scattering thereafter is indicative of the ~324897 relatively compl~te elution of saturates and an associated contribution from ~luted aromatics ~he relatively abrupt rise in w absorbance leading to point 37 is attributed to the elution of aromatic hydrocarbons in the weak solvent Aromatic species having proqressively increasing numbers of rings, as shown in part by the internal standard, continue to elute from the column with weak solvent The steep rise in W absorption which commences shortly after the start of tho progressive change from weak to strong solvent and which culminates in the peak absorbance (point 39) after the compo~ition of the moving p~ase has chang~d to ~trong solvent only is attributed to t~e elution of polar compounds Polar compounds ~re eluted relatively rapidly and ef f i-ciently (having regard to their relatively high molecular weights and physico-chemical properties) by the strong solvènt until they are substantially wholly r-moved from th~ column The elution of highly polar substance~, 6vid-nc d by p-ak~ 40 and 41, lead~ to complete recovery o~ t~e oil which wa~ in~ected into the column During the succeeding 38 minutes while the stationary phase in the column is subjected to equilibration with weak solvent (i e from 26 minutos to 60 minutes from the instant of sample introduction), th- initial properties of the stationary phas~ ar- r g-n~rat-d and a second cycle Or analysis can be impl~m nted by in~ecting the next sample Thu~, th- overall cycl- time is 60 minutes The overall cycle time may be reduced by increasing the flow rate of solvents through the column and/or by starting the introduction of the strong and modified strong solvent~ at earlier times ' The proportions of each hydrocarbon type or component in a sample are obtained by converting the light-scattering response to a linear function of total mass, and the W oscillator strength to a function of the mass of aromatic carbon, as described ~erein, and integrating each over a retention time interval components are defined by retention time intervals Thus, saturates may be defined, determined or consid-red as those compounds Qluting in t~e range betwe-n g and 16 channels, single-ring aro~aties a~ those eompounds Qluting in thQ range from 16 to 24 ehannels, 2-ring aromaties as thosa elutinq at from 24 to 40 channels, 3-ring aromaties as those Qluting at from 40 to 75 channels, 4-ring aromatics as those eluting at from 75 to 200 ehannels, weak polar eomponents as those elutinq at from 200 to 300 channels, and strong polar COmpOn-ntQ as those eluting at from 300 to 400 ehann-l~ The UQ- of the model eompounds to define the eomponents is d~scribed her-in (e g , with referenee to Figure 12) T~e quality of ~ column is mea~ured by chromatographing a "eocktail" containing toluene, anthraeene, and eoronene in eyelohexan- The column is run i~oeratieally with eyelohexan- and 0 01%
2-propanol Th- eapaeity faetors are 0 1, 0 5, and 2 0 for tolu-ne, anthraeene, and eoronen-, respec-tively, where the eapaeity faetor is the quantity ratantion volu~e minus void volume divided by the void volume of the stationary paeking pha~- in the eolumn ll Chromatl~graphy of thi~ mixture is found to give a good indieation of the quality of the column If a colu~n is eontaminated with retained polar~, or excessively aged, the capaeity factors inerea~- It i~ also found that eolumns from different manufaeturers display widely different _ 35 _ i324 897 capacity factor and separation per~ormanees, sven though they are all nominally NH2 bonded silica. A
summary of capacity factor data for different sources of adsorbent is given in Tabl~ 2. Columns with eapacity factors for coronene greater than 5 gave poor separations due to low yields of aromatics and polar eomponents.

Table 2 Capaeity FaetorQ, R(l) for ~k Funetional~zed Silieas Ad~ ent Tol~n~ AnthraCene CF
M~rck "Lic~rosorb NH2" 0.1 0.5 2.0 M~rek "Lie~rosorb NH2" 0.1 0.6 4.3 (aged)(2) Merek nLiehroprep NH2n 0.1 0.~ 2.~
Dupont "2Orbax NH2n(3) 0.35 2.9 >11 Waters ~Energy ~n~lysis 0.2 0.9 5.4 Colu~nn Notes:

(1) R eguals RetentinvVidUv 1- Void Volume (2) Ag~d eolumn wa~ run with 50 eyeles at s-mi-prQparative seale loading (4 mg).

(3) CoronenQ elution required 40% strong solvent.

The separation achiQved with eyelie s-mi-preparativ~ wale u~e of this pxoe-dure shows good selQctivity ~or miero-Conradson earbon residue (MCR), whieh is a measure o~ the eoXe forming tendeney, and exeellent seleetivity ~or metallo-porphyrins.

132~897 In a practical test o~ the method as disclosed her~ein, Cold ~ake bitumen was separated into 65% non-polars (saturates and aromatics) showing an MCR of 2.7 and 3~% polars with an MCR of 34 wt%. The whole bitumen had a MCR of 14.3 wt%.
Heavy Arabian Vacuum Resid was separated into a~
non-polar fraction of 53%-58% with an MCR of 9 and a polar fraction with yield of 43%-47% and an MCR of ~5%-47%. The whol- r-sid had an MCR Or 23 wt%.
ThQre were no metalloporphyrins detectable by vis~ble spectro~copy (~l ppm) in the non-polar fractions. These data indicate that tha refractory components (i.e., materials which are con~idered to ba detrim~ntal to the quality of a hydrocarbon sample andJor which adversely affect its subsequent usage) are concentrated in the polars fraction and that a hig~ yield, selective separation of nonpolars and polar~ has been achi~ved. The procedure retains aromatics a~ a function of their d~grea of con~uqa-tion~ In all analy~es using tha mae~od and eguip-m nt of tha invantion, 99~% of th~ saturates, aromatics, polar molacul-s and asphaltena ~ractions i~ recovar d within a relatively short analysis cycl- (e.g. 30 minutes). This contrasts with open column such as tho~e used in pursuance of ASTM D-4003 prior methods in which sampla recovery is incoopl-t-, typically about 9S% and wherein the ~nalysis r-guires relatively large samples (e.g. of th- ordar of 3 gra~s) and a r~latively long sampling ti~ (a.g. ~bout 8 hours).

Tha r g~n-r~bility ot th- ~tationary phase has b-an amply de~onstrated in practical tests.
Individual columns 11 hav- each b-en usQd for wall over 100 analytical cycles with 4 mg loadings before any significant loss of p~rformance has been observed. Th- chromatographic method and eguipment - ...
.... . . . ...

_ 37 _ 1 32~ 897 herein described can readily be adapted to operate automatically The complete analytical sequence as described by way of non-limitative example with reference to Figures 2 and 3 takes 30 minutes, although it can obviously taka a different time, and within the overall time of each cycle, the operation of the pumps for the weak and strong solvents, the timing of tAe injection of the oil 3ample and the recording of w absorption data (and mass d~tector data, if required) can all b- controlled by auto-matic ~gu~ncing equipment Sinc~ sucA automatic ~equencing Qquipment is well Xnown in thQ art and readily available from commercial manufacturer~, and, moreover, since it doe~ not form a direct part of the invention but only a convent~onal item of equipment, no description th~reof will be furnished h~r~in Tho chromatographic method and equipment Aoroin do~crib d can bo employ~d for th~ ovaluation of a hydrocarbon mixtur~ or in the regulation or optimization Or proces~-~ for refining or upgrading a ~ydrocarbon f-ad, for example in the fractional distillation of hydrocarbon feeds, in tha prepara-tion of f od~ for catalytic cracking wherein at l-a~t a portion of th- ~eed is subject~d to catalyt~c hydrogenat~on to reduc~ its refractory natur , ~nd in -~olvent r ~ining (e g deasphalt;ng) of hydrocarbon ~ixture~, int-r alia In the article in J Chromatography (1981) ~Q~, 289-300, C ~ollet et al de~cribe a high performancQ liquid chromatography (HPLC) technique that i~ ~aid to b~ capabl- of analyzing a vacuum re~idue (boiling range abov- 53SC) for saturates, 132~897 aromatics, and polar compounds The technique employs two procedures In the first procedure, saturates are separated from aromatics and polars using a stationary phase of 10 micrometer silica-bonded alkylamine in a column 20 em long by 4 8 mm internal diameter The mobile phase used was n-hexane, and it i9 stated that for asphaltene-containing samples, eyelohexane should be used as the mobile ph~Q to avold precipitation of asphal-tenQ~ T~ artiele doe~ not state that there i~
eomplete r-eov-ry of the sample in the eluent, but th~ artie~e eould b- int~rpret~d a~ i~plying that thQr~ iQ in faet 100~ sample reeovery Aeeording to the saeond procedure of Bollet et al , in whieh separation of saturates togethor with aromatie eompoundQ from polar com-pounds is e~rried out u~ing a ~oro polar solvent, a chromatographie eolumn paeked with Merek Liehrosorb-NH2 funetionalized sil$ea was equilibrat d with a ~olvent eomprised of 85% eyelo-hexane and 15% chloroform at a flow rate of 2 0 ~l/~in 120 mierogram of an Arabian heavy vacuum distillation reQidue ~950lF, 510~C) was injected into th eolumn in 20 ~ieroliter Or cyelohexane solution D~teet$on was by mon~toring W absorbanee at 25~, 280, and 330 nm Th~ ehromatogram generated (at 280 n~) is -~hown in Flgure 4a and indicatas the dilution of saturat-~ and aro~atics The ~low was th-n r-vor--d (baekflush) Polar eompounds eluted o~or th- n xt 10 minutos by whieh time a stable bas-line wa~ r-aehod This i~ shown in Figure 4B
(W absorbanee monitor~d at 280 nm) A sharp peak a~ report d by Bollet et al was not round This completed the Bollet et al analysis _ 39 - 1 32~897 ThQ method described by Bollet et al was compared with the mQthod disclosed herein and, as will be seen from the following results, the Bollet et al method leaves a considerable amount of the sample material, principally polar compounds, in the column, whereas 100% recovery (or essentially 100%
recovery) is achieved by the present mQthod To show that polars rocovery was inco~plete, and as an Qxa~ple o~ one way of performing th~ method of the invention, the flow was reversed to its normal (forward) direction and a solvent of 90% dichloromQthane and 10% l~opropanol wa~ introduced in a ~olvent gradient over 10 minute~ T~ absorbance was ~easur~d for 20 minutes during which time an additional peak due to ~trongly rQtain~d polars ~merged at about 8 minute~ ~Figure 4, which shows tha ab~orbance at 280 nm) Thus, th~ Bollet at al m~thod leaves some of tha polar material on the column Th- absorbance ~n aach of Figur~s 4a to 4c wa~ intagrat~d ov-r time to obtain ~ maa~ur~ of how much mat~rial was removed from t~ colu~n in each st~p The results are _ 40 _1324897 Normalized Area ~%~
- Forward Flow Cyclohexane Chloroform (85 15) 79 5 - Eluent Saturates and Aromatics - BacXflush Cyclohexane Chloroform (85 15) 8 4 - Eluent Polars - Forward Flow DichloromethanQ
Isopropanol (90 10) 12 1 - Eluent Additional Polars The amount of ~aterial which th~ BO11Qt et al method leaves on the column is about 12% of the vacuum residue sample This creates several problems which are avoided or overcom- by the method disclosed herein, namely - The mat~rial left on the column is not prop~rly accounted for in the compositional analysis - The material l-ft on the column creat~s adsorbing sit-s for subseguent analysis, giving irr-producible results - Tha mat-rial left on the column can ~v-ntually block the flow, causing high back pres~uro and 109s of operatlon In order to achieve good recovery of residual oilQ fro~ an HPLC column, the solid adsorbent mat-rial must be functionalized to shield the inorganic oxides and hydroxyls The final eluting solvent mu~t display solubility for asphal-tenes and hav- a hydrogen bonding functionality 132~897 and/or ot~er highly polar functionality to neutralize the surface polarity of the adsorbent The preferred combination is to use primary amine-functionalized silica as the adsorbent and a mix of dichloromethane and isopropanol, where the isopropanol is present at volume concentrations in the range of from 1 to 5G%, most preferably 10%, as the final solvent in the elution of the oil This solvent may be introduced either in forward flow or backflush It is th~ solubility and polarity aspects of the solvent which ~re important, not the flow direction In a modification o~ the ~epàration, a three pump system is employed T~e first pump delivers cyclohexane, the second dichloromethane, and the third isopropanol The delivery rates are varied in time CyclohexAne i~ used to elute saturates followed by aromatics, weakly polar compounds are th-n eluted with dichloromethane, and, finally, strongly polar mol~cul-s arc eluted with 10% isopropanol in dichloromathanQ~ ThQ exac~
solvent composition program is not critical to obtaining information, since component assignments can be varied It is important to increase the solubility paramet-r of the solvent as the chroma-tography proc~eds, so that oil components of suc-c-ssiv ly increasing solubility parameter can be d-sorbed and measured Preferably, the solubility par~m t~r of the solvent is increased progrQssively, rather than as a st-p chang However, a st~p chang~ may be used and is within the acope of the pres-nt invention as d-~in-d by the appended claim~

The distinction of being able to accurately analyze re~idua is among the more important advantage~ which the method disclosed .: --herein provides over the prior art. There are, however, several other advantages in the present method versus the prior art of Bollet et al., namely:

- Only a one-step procedure is used instead of two procedures, making the present ~ethod simpler - The aro~atic~ are separated by th-ir numbQr of condensed aromatic rings, thus giving additional co~positional information - A new d~tection sc~em~ as described herein ~llows quanti~ication of oil components without thc need to obtain re~ponse factors for each compound type In each one of th- refining or upgrading process-s h reinbofore m ntioned (i.Q., di-~tilla-tion, solv nt refining and catalytic cracking or coking), the present chromatographic method and equipm-nt m~y b- u~ed to detect unacceptable levels of a particular type of hydrocarbon or other m~terial, ~nd upon such detection, a signal is d riv d or produced fro~ which the operation of the proc-ss, and/or a step associat-d with the process, ~ay b~ modulated in order to reduc- the level of the undesirable hydrocarbon or other material to below th- unacc-ptable l-v l Thus, referring to each of the said for going proc--s-s in turn, th- following are th principal ob~ectives and the mann-r in which they ar- achiev~d pursuant to thQ invention -- : -132~897 1 Distilla1~iQ~

In the distillation of hydrocarbon feeds containing asphaltenic material (hereinafter termed ~asphaltenes" for brevity) a number of ~actors can lead to an excecsive amount of entrainment or carryover of asphalten~ into the distillate frac-tions particularly the gas oil Sraction~ Such factors include but are not limited to excessive stripping steam rat~s excessively high heat input to thQ bottom recyclQ stroa ; excessively high f~ed rat~

sincQ thQ presQnce of eXCQSSiVQ
asphalt~ne~ in a `distillato is u~ually detrimental to the quality of tha distillate and/or its oubse-quent us-, tho utilization of t~e ~quip~ent and method disclosed hQr~in to det~ct excessive a~phalt ne~ r~pr~s~nt~ an important step forward in optimizing tho oporation Or a distillation column According to thi~ aspect, 0 4 mg samples of gas oil from th- di~tillation column at a suit-abl~ standardiz~d tempQrature (e g 25C) are in~ect-d via valvQ 13 into the equipment of Figure 2 and ~ub~ ct d to th- chromatographic analysis da~crib d with r-~-rence to Figures 2 and 3 The a~phalt nos are highly polar and their concentration in t~- ga~ oil ~ampl- can readily be a~certained fro~ tho ar~a bonoath th~ W oocillator ~trength curve during olution with th~ ~trong ~olvont (e g botwe n point~ 38 and 42 of Figur- 3) The area ben~ath tho W o~cillator strongth curve i~ deter-min~d in accordanc~ with any of thQ well known conventional technique~ for ~o doing and where the area is in exce~ of an acceptable area any one or more o~ th~ known exp~di-nt~ to reducQ a~phaltQne . .
~, . .

132~897 entrainment in the distillation tower may be impl8-mented SincH it is not usually desirable to reduce the feed rate to`the tower, the expedient which may be employed first is to reduce the rate of stripping steam ThQ reduction in heat input to the tower may be compensated for by increasing the temperature of the bottoms reflux temperature rather than the feed temperature to regulate asphaltenes carryover, as will be known to those ~kill-d in thi~ field The requlation of the operation of the distillation tower in accordance with tha asphaltenQs as deter-mined by th~ chromatographic method disclosed herein may be ~ff~cted by manual ad~ustment, by operatives based on th~ output Of thB c~omatograph, or auto-matically, al~o -ba~ed on ths output of the chromatograph 2 ~olvent R~ining In solvent refining, a feedstock is intimat-ly contacted with a solvent havinq a selec-tiv~ ~olv ncy or affinity for a particular type of mat-rial in the f-ed and the resulting solution is separat d from the rQmaining raffinate In solvent deasphalting a feQd containing asphaltenic mat-rial~, her-inafter termed asphaltenes for br~vity, i~ ~ix d with a short chain n-paraffin, ~uch a~ n-propane, which i~ completely miscible with non-a-phalt nes but imoi~cibl- with asphaltenes ~h-r-by th~ latter rOrm a ~acond, heavier phase and can bc r nov d by ~uitable separation techniques, e g , d~cantation If the d-asphalting operation is per~or~ d at an exces~iv-ly high rate for the separation Or the asphaltene ~rom the solvent-oil solution to occur in the available equipment, asphaltene will be enerained into the otherwise deasphalted solution . . . .... ,. . ~ . ~ ..

-_ 45 _ 132~897 In order to monitor the asphaltene content of the deasphalted solution, a sample of the latter is passed at a suitable standard temperature into chromatographic equipment of the type described with reference to Figure 2, and thQ area under the W
oscillator strength curve during elution with ~trong solvent (corresponding to the area under curve 31 from points 38 to 40 in Figure 3) is determined by any of the known technigues If the area is in exc~ss of the area representativ- of an acceptable amount of entrained asphaltenes, the feed rate is reduced either by manual intervention or automati-cally until an acceptable asphaltene entrainment level is attained 3 Pre~ara~lon of Ca~aly~s~ Cracker Feeds fan~Uor u~ ng_Qr Ga$_Q11) C~talytic crack~r fQQdstocks in particular, and gas oils in g~neral, tend to contain proportion~ Or mol-cul-s containing one or more aromatic rings and also polar mol-cules The multi-aro~atic mol~cul~s t-nd to r~ist cracking during th~ir passag~ through a catalytic cracking unit and th-refore tend to be concentrated in the crack d products, while polar molecules tend to d-compos- during cracking to give relatively large carbonac~ous deposits on the catalyst, thereby impairing th- catalytic activity of the latter Mor~ov~r, gas oil and oth~r fraction~ containing multi-ring aromatic structur~s t-nd to produc~ smoke on combustion, and, for at lQast the foregoing consid-rations, it is d~sirabl~ to be able to control thQ levels of multi-aromatic molecules and polar molecules in gas oils and other hydrocarbon fractions .
' one method by which the concentration o~
asphaltenes, resins and multi-aromatic ring mole-cules in a distillate fraction such as gas oil may be regulated is to control the cut-point of the fraction during distillation, and the method for doing this has already been described herein in relation to distillation When the concentration of asphaltenes and multi-aromatic ring molecules in a distillat- fraction from a distillation unit is found to be in excess of a deQired maximum concen-tration using the chromatographic Qquipment and method as disclosed herei~, signals repre~entative of th~ W-absorption characteristics of a-~phaltenes and multi-aromatie ring mol~eul~s and indicativQ of the excese concentrations thQreof are derivQd and employed to control the operation of the distilla-tion unit until the concentration of such molecules is reducQd to an acceptablQ level in th~ distillate fraction In tha eont-xt of catalytic eracking, one method of r dueing th- t-nd-ney of aromatic mole-cul-s (including multi-aromatic moleculeQ) to be concentrat d in the cracked products is to hydrogenate th~m since the resulting naphthenic structure~ (i e cycloparaffinic structure~) crack relativoly r-adily Hydrogenation also tends to r dueo th- concQntration of polar compounds The hydrog nation i~ promoted by mean~ of a suitable hydrog nation catalyst, g a coibination of metals fro~ Group~ VI and V~I of th- P-riodie TablQ te g Mo and Co) on a low-acid carrier such a~ alumina In relativQ term~, hydrogen is an expensive commodity and therefore it is highly desirable from ~h- economics viewpoint to hydrogenat- only that s-lect-d proportion of the . - : .

.

- 132~897 hydrocarbon material whose hydrogenation will result in the production of cracked products of an accept-able quality The proportion which is hydrogenated may be selected by diverting the desired proportion to a hydrogenatinq unit or passing all the feed through the hydrogenating unit and varying the hydrogenating conditions to effect the desired proportion of hydrogenation, or by a combination of both of the forQgoing expedients in appropriate degrees Gan~rally spQaking, the catalytic hydro-treatmQnt of multi-aromatic molecules results in the hydrogenation of only one at a time of the aromatic ring~ in thQ molecules pQr hydrotr~atmQnt ThQ
hydrogenated ring i~ cracked upon paSSagQ ~hrough the catalytic cràcker and the resulting molecule with one less aromatic ring may be further hydrogenatod to facilitate the cracking of an additional saturated aromatic ring upon each subse-guQnt passag~ through the catalytic cracker until tho cont~nt of re~ractory aromatic molQcules in the cracked product~ i~ r duc-d to an accoptable 1eVQ1~

Catalytic hydrog-nation of polar molecules is al~o practiced to the ext-nt necessary to enhance tha guality of the hydrocarbon fraction to a level suitable for it~ subsequent use, e g in catalytic cracking ~ By way Or oxample, roferQnce is now made to Figure 5 which ~hows, in a block chemical engin~ering flow diagram, the principal featuro~ of a catalytic hydrotroatment unit 50 embodying process control In this non-limitativ- example, the unit is for onhancing th~ quality of a catalytic cracker feedstock, but it will be appreciated by those skilled in the art that it can be used to enhance tho quality of fe~dstocks for other purposes , ' 13248g7 ; - 48 -Thls unprocessed feed (~ g a gas oil fraction from a vacuum distillation tower) passes via line 51 to a sampling point 52 at which the main flow passes via line 53 to a catalytic hydrogenation facility, hereinafter termed "hydrotreater" 54 for ~revity Alternat~vely, product leaving the hydro-treater 54 via line 59, which passes to a catalytic crac~ing unit (not shown) via lin~ 60, may b~
sampled via line 57 and valve 56 An utomatic high performance iiquid chromatoqraphic (~PLC) analyzing and control unit 16, embodying equipment of the type d~scrih~d here~n with particular reference to Figure 2, analyzes the sa~plQs of unproces~ed feQd from line s5 or processQd fQed from linQ 57, and regulates the operation of the hydrotreat~ent unit 50 so that the feed in lino 60 ha~ an acceptable quality Used samples aro discharged via line 62 Tho HPLC unit 61 has a regulatory in~luence on at least the following (int~r alia) (a) t~e flow rate of feQd through the hydrotreater and th~reby the residence tim or spac- volocity;

(b) th- ratio of hydrogen to feed in the hydrotr~ater 54 as det-rmined ~y a hydrog n control unit 63 As has already baon ~tat d h rein, hydrog-n i~ r-lativ-ly xpen~ive and an conomic balance is pr~f-rably to b- struck by comparing the cost of hydrogen usage with the increased ~alu- of hydrogenatQd fQedstock The hydrogen control unit 63 plays a part in achi-ving thi3 economic balancQ

.

(c) thQ operating temperatures of the hydrotr~eater 54 as determined by a tem-perature control unit 64 Higher operating temperatures increase the removal of heteroatoms (such as nitrogen) in polar molecules which tend to reduce the activity of the catalytic cracXing unit while lowcr operating te~peraturQs increase the saturation of aromatic rings in mol~cules containing them An economic balance must b~ ~truck bstween tho value of a processed ~Qedstock of r~duc~d polar molecule content and the value of th~
procQs~Qd feedstock of lower saturated aromatic ring contQnt ThQ temperatur~
control unit 64 play~ a part in achieving this ov~rall balanca Th~ sotting~ of each of tho feed rate, the hydrogen control unit 63 and the temperature control unit 64 ~ay oac~ b~ ad~u~t d by manual operation or by auto atic operation or by a combination of ~anual and auto~atic op ration Wh n automatic control of ono or ~or s-tting~ i~ employed, the control may be by mean~ of a computer (not shown) of conventional typ- Sultable program~ for a control computer to gov-rn part or all of tho oporations of unit SO can b- d-~i~-d by any comp tent programm r Neither the control co~put-r nor th- ~oftwar- thorefor will be d-scrib d b cause both fall within the present ~tate of th- art and noith r i- dir-ctly g-rman- to the pro~-nt invention a~ d-fin-d by the appended claims Th- op~ration of th- catalytic hydrotr-at~nt unit 50 i~ now de~cribed with parti-cular ref-rence to preparing an upgraded catalytic ' .. ~
, ;~ . , . ~", ` t .

132~897 -- so --cracker feedstock from a feed obtained ~rom a vacuum distillation tower (not shown) The raw feed in line 51 is initially passed, at least in a major proportion, via line 53 to the hydrotreater, and then via line 59 to the cat cracker feedlinQ 60. Sa~ples of th~ feed in line 55 and the product in lin~ 57 are pa~sed pQriodically (e g onc~ every 60 minutes) and alt-rnately to the HPLC unit 61 and therQin analyz~d ~or saturate~, mono- and multi-aromatic ring moleculQs and polar molQcules ~which latter will contain hetQroatoms such as nitrogen and oxygen). ~he analysi~ by the HPLC unit 61 is efrected in the manner herein described in general, and al~o in particular with refQrencQ to FigurQs 2 and 3 From the analy~is in the unit 61, ~ignals arQ derived in ~ignal lincs 67 and 68, repre~-ntative of the composition of t~e raw feed Information on th- fe-d may be usQd in a "feed-foruard" control s-n~ to set thQ be~t esti-mated condition~ of flow rate, temperaturQ and bydrog-n pre~ur in thR hydrotreater I~ the product in line 59 has an unacceptably high content o~ multi-ring aromatic molacule~ and polar ~olecul-s, the hydrogon control unit 63 op rates to incrQa~- the partial pressurQ of hydrog-n and th- ratio o~ hydrog-n to raw fe~d in th- hydrotreat-r 54 ~ub~-ct to progr~mm d C08t con traint signals to th unit 63 provided ~rom the control comput-r via ~ignal line 69 The normal sQtting of the temperature control unit 64 i~ ehat appropriate for th~ satura-tion of aromatic nuclei, i - a relatively low - :
.

, ~
. , .
. .

- 132489~

hydrotreating temperature within the range of ~rom about 300 to 5100C The normal setting, however, is subject to modulation by signals from the control computer which reach the te~perature control unit 64 via signal line 70 to increase the hydrotreating temperature in order to reduce the heteroatom content (i e polar molecule content) of the raw feed to an acceptable level commensurate with an acceptabl- level o~ saturation of aromatic rings in the raw feed T~ ~etting of the valve 56 may be varied by human intervention or by a signal from the control computer (signàl line 71) to the ~tr~am and frequency at which it is analyzed So~e additional illustrationQ of the method disclo~ed herein are now giv-n in the follow-ing non-limitative xa~pl-~

ExamDle 1 Production o~ LubR Basestock Th- ob~ectiv~ in producing lube basestock is to separate mol-cule- from a feedstock which has good lubricating properties, principally including a high viscosity ind-x Saturated hydrocarbons and aromatic~ not exce ding on- ring ar- most desirable Two of th~ i~portant steps in th- production of a h-avy lukeJtock of the typ- known as brightstock are dea~phalting a vacuu~ resid with propane to produce a deasphalt-d oil, and extraction o~ the condensed ring aromatics and resins from the deasphalted oil with a polar ~olvent ~uch as phenol to produce a raffinate The a~phalt produced in the first step and the aromatics-rich extract produced , - 52 - 1324~7 in the secondl are ~yproducts which have other uses HPLC techni~es as described herein are used to monitor the molecular composition of each stream and to regulate the process conditions to achieve the highest yield of raffinate within quality specifica-tions which are based on molecular composition Samples of each proce~s stream were obtainQd and analyzed according to the description of FiqurQs 2 and 3 The evaporative light-scattering dat~ctor was e~ployed It was lin-arized according to equations (2) and ~3) abov- by mQasur-ing its peak rasponsa to known concentrations of a vac~m gas oil T~e integratad l~val of each compon~nt, whose r~tention time limits are dQ~ined by model components, is qiven in term~ of weight percent of total sample in Table 3 Observations of the data sugge~t process modification~ which will b- obvious to those skilled in production of lub- basestock The re~ected asphalt str am from th d-asphalting step contains lS 7% ~aturate~ Some or all of these could be included in the d asphalt-d oil by lowering the temp~rature or increasinq the treat ratio ~i e., the ~olvont to fe dstock ratio) in th- deaQphalter The dea-phalt-d oil conta~ns ~mounts of 3- and 4-ring aromatic~ which are b~low th d-taction limit but which are concantrated in th~ xtract The extrac-tion st-p wa~ ff-ctiv at r-moving the 2- 3- and 4-ring aromatic~ from the ra~finat- but there is a trac- u~ount o~ r-sins (polar compounds) remaining and some saturate~ w-re also r-moved The ~electiv-ity of this separation could be improved by increasing the trezlt ratio for example It is assumed that proc-ss changes aro made by balancing . ..

~, ;

1 32~ 897 the cost of ma~ing the change versue the benef its in improved product quality or quantity.

Table 3 Mo~çcula~ comDosition of Lube Stocks ~%~
Deasphalted Raffi-~Q~i~ As~halt Oil__ ~x~çt n~te saturates 30 0 15 7 60 5 19 1 75 2 Aromatic~ 1 19 414 6 28 8 34 5 22 6 Aromatics 2 7.8 7.7 5.8 17.4 0.0 Aromatie~ 3 2 9 5.7 0.0 10.1 0.0 Aromatics 4 2.2 4.9 0.0 8.1 0.0 Polar~ 37 8 51 4 2 7 8 g o s ExamDle 2 Produe~ion ~ ~at_Cra~klng_Fi~5tCk~

A haavy vacuu~ gas oil and a heavy coker gas oil ~ro produe d by vaeuu~ di~tillation and a fluid coking proco~, re~pectively ~These stream~
are found to b- too hlgh in ~ulfur, nitrogen, 3~-ring arooatie~, and polar~ for efficient cat cracking They are, th-refore, blended and sub-~ect-d to a hydrotreating process wherein they are pa~ d throug~ two reactors in series Both r actor- ~r load d with a commercial Co-Mo on alunina hydrotreating eatalyst The feed is eocingl~d ~ith hydrogen ga~ at a partial pr ssure of 1200 p~i ~8278 kPa) and th- av~rag~ bed temperature in 705F ~373 ~C) Th- re~id-ne- timo is about 22 min in each reactor The molecular compo~ition of the feed is compared to the product of the first reactor and the seeond ~-ri-~ reactor by th- HPLC method of the 132~8~7 invention The separation i~ ~ffected by the method described with reference to Figures 2 and 3 The detector is a W diode array spectrophotometer The integrated oscillator strength is calculated as in equation (1) above and converted to weight percent of aromatic carbon by the correlation of Figure 1 The composition of each stream is given in Table 4 It is apparent that the feQdstock is upgraded across 2ach r~actor Th~ net upgrade result~ in a content of 3+-ring aromatics and polars which i~ only about hal~ of tho starting level ~oth 1- and 2-ring aromatic~ ar- produc-d by hydrogenation oS the polynucle~r aromatic~

T~e inform~tion availabl~ in Tablc 4 may be used to regulate the process I~ the product 1QVQ1 of 3+-ring aro~atic-~ plus polar~ is below a ~t point d~t~rmin~d to provide good cat crackar ~edstock, the plant operator may decida either to d~crea-~o th- re-QidQnc~ tim~ through both reactor~ or to bypass th~ s~cond r-actor al~ogeth-r, ~or ~xampl~ Oth-r comoon mean~ of control would be to v~ry hydrog n partial prBssure or temperature or both .
.' ' , '. ' ~:
.
"

132~97 Table 4 Molecular Compositions a~ Affected by Hydrotreating Upgrade (Units are Weight Percent aromatiç Carbon) First Second Reactor Reactor Com~on~nt EQ~ ELQ~ E~çg~t l-Ring Aromatic Core 3 ~ S 6 6 2-Ring Aromatic Core S 0 6 4 6 ~
3-Ring Aroaatic Coro 5 5 6 0 4 7 4-Rlng Aro~tic Core 8 9 5 2 3 7 Polar Cora 10 0 6 2 5 0 The invention dofin~d by tho app-nd~d claim~ i~ not confined to thQ ~pecific e~bodi~ent~
~erein disclo~d Moreover, any f~atura w~ich i~
do~crib~d in connection with one mbodim nt may be e~ploy d wit~ any other ~bodi~ nt without d-parting from th inv ntion as dofin d by tha append~d claims It i~ furth r r narX d that tho W d-t-c-tion t chnlguo disclo~ d h r-ln, d~rivlng th int grat d o-cillator str ngth, may bo us d alon- in HP~C for d t-r ining t~ vel of aromatic carbon pr~sont or in comblnation with tho ma~s sensltive measuring t chniqu~ (using at least w-ak and strong aluting olv~nt~) for ~ asuring tho 1QVO1 of sat-urat--, aro~tic~ and polar~ in th~ oil ~a~ple ' :

Claims (15)

1. a method for the chromatographic analysis of hydrocarbon oil, comprising the steps of:
(a) passing a mixture of the hydrocarbon oil and a carrier phase in contact with a chromatographic stationary phase over a first time interval so as to retain components of said hydrocarbon oil on said stationary phase;
(b) passing a mobile phase in contact with said stationary phase after step (a) over a second time interval, for eluting different retained components of said oil from said stationary phase at different time intervals, and recovering the mobile phase which has contacted the stationary phase together with the components eluted from the stationary phase;
(c) irradiating the recovered mobile phase with UV light having a wavelength range of which at least a part is within about 200 nm to about 400 nm over a sufficient time period that the recovered compo-nents in the recovered mobile phase are subjected to said irradiation, said mobile phase being substantially trans-parent to UV light within said wavelength range;
(d) monitoring the absorbance of said UV
light by said irradiated components across said wavelength range and deriving the integral of absorbance as a function of photon energy across said wavelength range; and (e) measuring the magnitude of said derived integral in at least one selected time interval corresponding with the elution of one or more components.

2. A method as claimed in claim 1, wherein the recovered mobile phase from the stationary phase is irradiated with UV light having a wavelength range within the range 230 to 400 nm, and wherein a scaling factor of 2 is applied to the derivation of the integral of absorbance so that the magnitude of said derived integral of absorbance is doubled, and the said magnitude is measured in step (e) in a time interval corresponding with polar components in said mobile phase recovered from the stationary phase.

3. A method as claimed in claim 1, wherein the absorbance of said UV light by said irradiated components is monitoring using a diode array detector.

4. a method as claimed in claim 1 for determining the different ring-numbers of aromatics present in the hydrocarbon oil, wherein the station-ary phase is calibrated by effecting steps which corresponds with steps (a) to (d) but in which selected molecules containing different numbers of aromatic rings which are known are used in place of said hydrocarbon oil, so as to associate the differ-ent times at which the selected molecules are observed in the step corresponding with (d) to elute from the stationary phase with the corresponding ring-numbers of the respective selected molecules, and wherein the ring numbers of the aromatics in the hydrocarbon oil are determined by comparing the time response in step (d) with the different times, determined in the calibration, which correspond respectively with the different aromatic ring numbers

5. A method as claimed in claim 4, wherein molecules of toluene, anthracene and coronene are used for calibrating the stationary phase for 1-ring, 3-ring and 6-ring aromatics.

6. A method as claimed in claim 1, wherein said mobile phase is a weak solvent for eluting saturates and aromatics (but not polars) from the stationary phase, and wherein, after substantially all the saturates and aromatics have been eluted, a strong solvent is substituted for said weak solvent for eluting polars from said stationary phase.

7. A method as claimed in claim 6, wherein said stationary phase comprises an amine-functionalized silica stationary phase, said weak solvent has a solubility parameter in the range 7.6 to 8.8 cal0.5 cm-1.5 and said strong solvent has a solubility parameter in the range 8.9 to 10.0 cal0.5 cm-1.5.

8. A method as claimed in claim 1, wherein the mobile phase is a solvent and wherein said method further comprises the further step (f) of detecting the total mass of components eluted from the stationary phase by a technique selected from: (1) determining the refractive index of the eluate; (2) solvent evaporation followed by flame ionization of the solvent-free eluate; and (3) solvent evaporation followed by monitoring of light-scattering of an aerosol of the solvent-free eluate.

9. A method as claimed in claim 8, wherein the magnitude of said derived integral is measured in step (e) in a time interval correspond-ing with the presence of aromatics in said solvent, and further comprising the step of deriving the difference or ratio between the measured level of aromatics present and the detected total mass of hydrocarbon components eluted from the stationary phase.

10. A method as claimed in claim 6, wherein after some polars have been eluted by the strong solvent, that solvent is modified with a hydrogen-bonding solvent which is miscible with the strong solvent, for eluting more highly polar components of the oil.

11. A process for refining or upgrading a petroleum hydrocarbon feed, in which samples of hydrocarbon oil produced in the process are each chromatographically analyzed by a method as claimed in claim 1 to determine the level present of at least one component in the oil, and in which the operation of the process is controlled in dependence upon the determined level present of said at least one component.

12. A process as claim d in claim 11, in which the control of the operation or the process is such as to oppose any rise in value of the level present of said at least one component above a predetermined value.

13. A process for refining or upgrading a petroleum hydrocarbon feed containing asphaltenic materials in which the feed is passed to a frac-tionation unit having a temperature and pressure gradient thereacross for separation into components according to the boiling ranges thereof said components being recovered from respective regions of the fractionation unit and including a gas oil component boiling in a gas oil boiling range which is recovered from a gas oil recovery region of the unit, wherein discrete samples of gas oil fraction are taken from the recovered gas oil fraction at intervals and each analyzed by the method of claim 1, and wherein a signal representative of the amount of asphalt material present in each sample is generated and employed to modulate the operation of the fractionation unit to that the amount of polar component in the gas oil component is maintained below a predetermined amount.

14. A process for refining or upgrading a petroleum hydrocarbon feed in which the feed is passed to a catalytic cracking unit and converted to cracked products including upgraded hydrocarbon materials, wherein discrete samples of the feed passing to the catalytic cracking unit are taken at intervals and each analyzed by the method of claim 1, and a signal representative of the amounts of polar components and aromatic components having at least 3 rings ("3+-ring aromatics") is generated, and the feed is either blended with a higher quality food or subjected to a catalytic hydrogenation treatment or both blended and catalytically hydrogenated if and/or when said signal corresponds to amounts of 3+-ring aromatic components and polar components in excess of predetermined amounts, the intensity of said catalytic hydrogenation treatment being increased and decreased with respective increases and decreases in the magnitude of the said signal

15. A process for refining and upgrading a petroleum hydrocarbon feed containing undesirable contaminating components selected from asphaltenic materials, aromatic components containing at least three conjugated aromatic rings ("3+aromatics") polar components and mixtures comprising at least two of said contaminating components, comprising the steps of mixing a stream of a selective refining agent at selected refining conditions and separately recovering from the resulting mixture: (i) a hydrocarbon raffinate stream having a reduced content of polar components and aromatic components;
and (ii) a stream of a mixture containing solvent and at least on of said contaminating components, wherein discrete samples of the raffinate stream are taken at intervals and each analyzed by the method of claim 1 and wherein a signal representative of the amount of contaminating component is derived, and employed directly or indirectly to vary the said refining conditions so as to maintain the amount of contaminating component in the raffinate below a selected amount.