Column Liquid Chromatography

chromatography


The establish of CLC method 2.1 Column, support and heating apparatus
The dimension of glass chromatographic column is 90 mm length and 6 mm I. D. Silica gel with particle size range from 100 to 200 meshes was provided by marine chemical plant of Qingdao China.Silica gel was active under temperature of 180 o C for 4 hours before use.Oxide of alumna 0.047-0.147mm used was purchased from chemical and medical reagent company in Shanghai China.Muffle furnace (50 °C-1000 °C) and oven was used for sample preparation and heating.

Analytical instruments
Fourier transforms FT-IR spectra were measured by a Bio-Rad Excalibur Series FTS 3000 spectrometer in the range of 4000-400 cm −1 using KBr pellets. 1 H NMR measurements were made with a Bruker Avance 500 spectrometer operating at 500.1 MHz.

Optimum chromatographic condition
As a base line, some pure reagents were chosen as model components prepared for CLC.These model compounds were tetracosane for saturates, dibenz [ah]anthracen for aromatics and acetanilide for resins.There is no appropriate pure reagent used for asphaltene fraction, so the insoluble fraction of tetrahydrofuran in one asphalt sample was used for asphaltene fraction.
Through a series of investigations,the optimum chromatographic operation was performed.The final optimum conditions were obtained as follows: Chromatographic column was glass column being 90 mm length, 6 mm i.d.The amount of silica gel used was from 1 to 1.5 gram.
The amount of alumina was from 1.5 to 1.8 gram.Total sample used was about 0.1 gram.The solvent of heptanes, mixture of heptanes/ dichloromethane (1/2.5, V/V) and mixture of dichloromethane/ trichloromethane (1/3, V/V) were as elutes corresponding to saturated hydrocarbon, aromatic hydrocarbon and resin respectively.The amount of heptanes, heptanes/ dichloromethane, and dichloromethane/ trichloromethane was 20ml, 35ml and 30ml respectively.Each fraction collected was dried in vacuum under 60 o C until the weight keep constant.
Through above group analysis, the experimental deviation and recovery of CLC method are summarized in Table

Check of chromatographic resolution rate by FT-IR
The result of CLC method was checked by Fourier transform infrared (FT-IR) method .The spectra IR were acquired in the transmission mode as 64 scan in the IR range from 4000 to 500cm -1 at a resolution of 4cm -1 .KBr standard pellets were used, and the samples were dried and then mixed with KBr, ground, and palletized.
IR spectrums of pure reagents including tetracosane, dibenz(ah)anthracen and acetanilide were obtained and used for standards.The IR spectrums of different fractions collected from flow out separated of the mixture reagents, and spectrums were compared with above standard spectrums.The results were shown in Figure 1.It is important to indicate that the IR spectra of fraction 1 collected (from 1202# sample) show similarity with pure tetracosane reagent.IR spectra for fraction 2 and fraction 3 show accordant results with dibenz(ah)anthracen and acetanilide respectively.

Check of chromatographic resolution rate by 1 H NMR
The CLC method was checked also by 1 H NMR. It measured different fractions collected from flow out separated of the mixture reagents and spectrums were compared with above standard spectrums.The high resolution 1 H NMR spectra of pure model compounds and fraction 1-3 are shown in Figure 2.
It is difficult to separate complex and heavy sample, however the IR and 1 H NMR analysis of the prepared fractions from CLC were all good agreement with pure reagents.This observation indicate the optimum CLC parameter in this work guarantee a good qualitative results. www.intechopen.com

Evaluation of analysis of group composition by CLC
The recover rate and experiment deviations for model compounds were summarized in Table 1.It can be seen that the experiment result are fine.
Compared with routine ASTM method, these optimum chromatographic conditions show many advantages.First, the reagent and sample consumed was fewer than total solvent of 300 ml of classic ASTM method.Second, the dichloromethane and trichloromethane used in present study, compared with toluene and benzotrichloride used, has lower toxicity.

The application in making high grade road asphalt
Coal is used as the main source of energy in China.The crude oil produced in China is paraffinic; therefore, it is not suitable for road asphalt.China is trying to produce high grade road asphalt from the mixture of coal and petroleum [11,12].
Three asphalt samples from petroleum and coal processing for high grade paving asphalt were characterized by established method.Sample NE-6, NE-9, NE-11 were the heavy products by co-processing of Shijiazhuang oil (a petroleum factory in China) and Yanzhou coal (a typical coal in China).The coal and oil ratio was 1:1.Among asphalt samples, the preparation of NE-6 sample was under the role of Fe catalyst during co-processing.NE-9 sample was related to Mo catalyst.The sample TLA is from Trindid Lake Asphalt.The results of group type analysis for four asphalt samples were shown in Table 2.It is important to note intense absorption peaks for saturated fraction (Fig. 3).Based the standard IR handbook, the absorption peaks around 719.45cm -1 , 1377.17 cm -1 , 2850.78 cm -1 , 2918.29 cm -1 and 2959.79 cm -1 was attributed to characteristics peak for δ(CH 2 ) N N>6,δ(CH 3 ),υ s CH 3 ,υ as (CH 2 ) and υ as CH 3 respectively.These data show that the prepared saturated fraction has a high purity.

Name
As Figure 4 show, the absorption peaks around 748.38 cm -1 , 812.03 cm -1 , 877.61 cm -1 and 3049.45cm -1 belong to character peak of aromatic C-H absorption.The peaks at 1602.84 cm - 1 ,1580 cm -1 and 1410 cm -1 were characteristics absorption peak of aromatic carbon.Obviously, the obtained aromatic hydrocarbon fraction has a good purity.The results from Figure 5 show that the resin fractions concentrate some oxygen-containing compounds.This conclusion can be approved by the appearing peak around 1215.15 cm-1, which is characteristics absorption peak for phenol compounds, and peak around 3649.31 cm-1, which is characteristics absorption peak for dissociate OH.The peaks at 1033.84 cm-1 and 1608.63 cm-1 attribute to the absorption from OH and C-O-C group.This is comprehensible because OH group in the structure the phenol connects to the aryl group, which may induce some aromatic absorption peaks.
The FTIR results show high resolution of CLC method established.It is difficult to separate complex and heavy sample, however the IR analysis of the prepared fractions from the CLC chow all good results This observation indicate that chromatographic parameter guarantee a good qualitative results.

The determination of MWDs by CLC coupled with SEC
Among characteristics of heavy oil, the size exchange chromatography (SEC) can be used to determine molecular weight distributions (MWDs), weight average molecular weight (Mw) and number average molecular weight (Mn), etc.With heavy oil of a group as example, the conditions of SEC are summarized as follows.
The analysis conditions are: a Shimadzu LC-10A high performance liquid chromatograph with an SPD-10AUP UV detector, the chromatographic column of SHIMPACK -801 (30 cm length, 0.8 cm i.d., polystyrene 6 µm), mobile phase of THF; flow rat with 1.2 ml/min; column temperature at 25 o C.
The SEC chromatograms are shown in Figure 6, MWDs results are listed in Table 3.
In Figure 6, the sources of coal asphalt , KP petroleum asphalt, ethylene residue oil and vacuum residue oil are from Shanxi coking plant in China, Korea refining, Xinjiang oil refinery in China and Saudi Arabia's oil refining, respectively.How much is the "representative" characteristics of this SEC method?This is an important problem to need know to treating these spectra and data of SEC.The so-called "representative" refers that extent which could be determined out of sample.Because most present SEC method is only suitable to compounds having UV adsorbent and soluble of THF, so, it is needed to know representative of whole sample.This problem will be completed only by CLC.Because the four groups: saturates, aromatics, resins and asphaltenes quantitatively could be obtained by CLC determination, then the "representative "(R index) will be calculated as the following.
R =100 %-W asp % -W a1k % Which R represents the representation index; W asph % and W a1k % represent the weight percent of asphaltene in sample and the weight percent of saturated hydrocarbons in sample, respectively.
With samples of Figure 6 as example, their R indexes from this CLC analysis are listed in Table 4.These results show that the CLC coupled with SEC is an effective mean to analyze MWDs.

Analysis of resin component by CLC coupled with HPLC
As components of resin of heavy oil are very complicated, so to analyze them is very difficult by only one method.However, CLC coupled with high performance liquid chromatography (HPLC) can separate successfully, quality and quantity these compositions.
Because the resin fraction got concentrate oxygen-containing compounds and other heteroatom-containing compounds by CLC separation, then the analysis of these hetero-atomcontaining compounds became easy to by HPLC.With slurry oil (Tianjing Refinery of China) as an example, the analysis of components in resin was summarized as follows.
The preparation of resin fraction was same as that of above description of CLC; the HPLC was performed on a Shimadzu LC-3A chromatogram with a SPD-1 UV detector, operated at 254 nm.Two ODS (4.6×20 cm) columns in series were operated at 40 o C with methanol /water=78:22(V/V) as the mobile phase, flowing at a rate of 0.8 ml/min.Typical separation chromatogram is shown in Figure 7.
From Figure 7 it can be seen the high resolution separation rate of complex compositions, these confirmed that the CLC preparation is successful and HPLC analysis is better.
The three qualitative methods of HPLC were selected to determine compositions of resin fraction.The three methods [13] are follows.
1.The qualitative method of relative retention time (RRT).
2. The qualitative method of stop-flow UV scanning.
3. The qualitative method of UV characteristic index V'.
The quantitative determination of compositions was by the method of external standard (E-X) and the calculation formula uses the following.
where W x % is the weight content percent of x composition in heavy oil sample, R x % and C ex % are the concentration of preparation solution of resin fraction and external standard solution, respectively, S x and S ex are the peak areas of component x and external standard, respectively, V ex and V x are the injection volumes of external standard solution and resin solution, respectively, R es % is the weight percent of resin fraction in heavy oil sample.The qualitative and quantitative results are in Table 5.

Conclusion
A modified method for group type analysis of asphalt using CLC was established.The small-type CLC technique shows many advantages, such as high resolution rate, rapid operation, and requires minimal quantities of sample and solvent.The both of IR and 1 H NMR results check the high resolution of this method.
The CLC method compared with routine ASTM method, the reagents used in this method are small amount and lower toxicity.These are beneficial to environmental protection and human health.This is very important for modern analysis.
The CLC method of this paper is an important and indispensable analysis method to study heavy oils.It is not only a separation means, but is also analysis means.This method was successfully applied to many analysis aspects, such as making high grade road asphalt, characterizing MWDs and analysis heterocyclic of aromatic compositions of heavy oils.
The analysis of heavy oil is a long and difficult task.We systematically summarized these studies and hope that these will help our colleagues.

FTIR experiments were performed
to check the qualitative ability of established method.IR spectra of saturated fraction, aromatic fraction and resin fraction for sample NE-9 were shown in Figure from 3 to 5.

Table 1 .
. From Table, it can be seen that the average of deviation and recover are -1.546% and 100.681% respectively; the results are good.Experimental deviation and recovery of model compound.

Table 2 .
Results of groups composition of asphalts (W%).From Table2it can be seen that the application of established method to real asphalt samples show good results.Different samples have different group composition characterize.The experiment deviations of contents(W%) are in the ranges from 0.255% to 1.800%.

Table 3 .
The MWDs of typical heavy oils www.intechopen.com

Table 4 .
The R indicators.

Table 5 .
Results of components of resin (ppm).