analysis of alkyl dibenzothiophenes with the fpd + …...page 34 gulf coast conference 2013 title...

Gulf Coast Conference 20131

Analysis of Alkyl Dibenzothiophenes with the FPD + and Deans Switching

Roger L FirorAgilent Technologies Inc.Wilmington, DE

Intro to FPD+Deans SwitchApplications FPD/FIDApplications FPD/MSDSummary

FPD Plus: Analysis of Alkyl Dibenzothiophenes


• Detail on sulfur content is vital for optimal hydrotreating or hydrocracking conditions.

• Profiling dibenzothiophenes is of particular importance to achieve the lowest sulfur levels in final products.

• These include dibenzothiophene, methyl (C1) substituted dibenzothioiphenes, dimethyl (C2) dibenzothiophenes, C3, and C4 dibenzothiophenes.

• To achieve optimal results the FPD should be operated at temperatures above 325 °C when dealing with heavier feedstocks.

FPD Plus with Outer Cover Removed


Redesigned area: The emission block is thermally isolated from the transfer Line by the thin-walled tube and unique purged gap.

This makes high temperature operation possible.

Emission block can be kept at an optimal 150 °C while the transfer line is heated as high as 400 °C

Maximum temperature is 400 °C for the transfer line

Column Connection Cross Section for the FPD +


Standard capillary column fitting is used. Adapter is available for 1/8” packed columns.

FPD Plus Specifications


Sensitivity (Sulfur mode) 2.5 pgS/sec

Sensitivity (Phosphorous mode) 45 fgP/sec

Maximum Transfer line temp 400 °C

ModesConstant makeup + fuelColumn + makeup = constantColumn + fuel = constant

Previous Generation FPD

Sulfur: 4 pg/sPhosphorous: 60 fg/s

Hydrocarbon Quenching


Hydrocarbon Quenching can occur when a high concentration of CO2 from a hydrocarbon enters the flame at the same time as a sulfur species

Some of the emitted light from the activated sulfur (S2*) is adsorbed by CO2

Activity in the detector ( i.e. transfer line) can contribute to quenching due to possible free radical formation


Deans Switch System for Sulfur Determination in Petroleum Feedstocks

7890B Deans Configuration with the New FPD Plus

FID

MMI

FPD+

PCM

Restrictor

Primary - HP-130m x 0.25 mm x 0.25um

Secondary – DB17 HT30m x 0.25 mm x 0.25um

Analysis of Alkyl Dibenzothiophenes in Fuels and Distillates


Samples analyzed:

Road Diesel Two Light Cycle Oils with different processing Cracked Gas Oil Heavy Vacuum Gas Oil

DBT Standards: Chiron Norway, US distributor is RTCorp, Laramie, WY

Typical Parameters


GC 7890BInlet Multi Mode Inlet (MMI)MMI program 250 °C to 350 °C at 50 °C/minSplit ratio 25-150 to 1

Typical oven program40 °C ( 0 min) to 250 °C (10 min) @ 10 °C/minthen 15 °C/min to 350 °C (10 min)

Primary column flow 1.25 mL/min He @ constant flowSecondary column flow 2.20 mL/min He @ constant flow

FPD transfer line 325 °C to 360 °CFPD Emission block 150 °C

Road DieselDeans Cut: 18 to 24 min.

4,6 DMDBT


Identified by retention time using pure standard

Calibration of 4,6 DMDBT from 1 to 100 ppm


ug/mL

Sq.

Rt.

Are

a

Split ratio: 25 to 1

Road Diesel


Split: 25 to 1

4,6 DM DBT

4E,6M DBT

Identified by retention time using pure standard

LCO Typical Sulfur Speciation

Total sulfur, wt.% 0.7

4,6 dimethydibenzothiophene 56 ppm

4-methyldibenzothiophene 231 ppm

Other dibenzothiophenes 702 ppm

Reference: V. Thakkar, S. Abdo, V. Gembicki, J. Gehee, LCO Upgrading, UOP LLC, 2005


LCO 2: FIDCut 18 to 24 min.


LCO 2


DBT

4M DBT

4,6 DM DBT

Cut: 18 to 24 min

2M DBT, 3M DBT

2,4,6 TM DBT

FID

FPD +

cut

LCO 2: FPD +


2,4,6 TMDBT

1,4 DMDBT

4,6 DMDBT

4 MDBT

3 MDBT

DBT

1 MDBT

2 MDBT

LCO 1: FPD +


4,6 DM DBT

4M DBT

C3 DBT’s

Cut: 18 to 24 min

Cracked Gas Oil


FID

Backflush

Cut to FPDCut: 23 to 25 min

Flow Programming for Backflush


Flow program primary column:1.25 mL/min for 27 min. , then 100 mL/min to -3.8 mL/min

Flow program secondary column:2.2 ml/min for 27 min. , then 100 mL/min to 4 mL/min

The primary column in a Deans switch can be backflushed with flow programming

Cracked Gas Oil: FPD +


C3 DBT’s

2,3,

6 TM

DB

T

1M D

BT

2M &

3M

DB

T

4,6

DM

DB

T

2,8

DM

DB

T

1,4

DM

DB

T

Cut: 20 to 24 min.

Cracked Gas Oil: Late Cut


Cut: 25 to 26 minC3+ DBT’s

FID

FPD

BackflushStarts

C3 Plus Alkylated Dibenzothiophenes in Heavy Vacuum Gas Oil


FID

FPDMany compounds are unresolved due to sample complexity

Backflush


Deans Switch System with FPD+ and 5977 MSD

MSD

MMI

FPD+

PCM

Restrictor

Primary: DB5-ms30m x 0.25 mm x 0.25um

Secondary: DB17 HT30m x 0.25 mm x 0.25um

0.63 m x .10 mm

No Heart Cut: Pure Standards


• Standards injected

• No switching to the MSD

• Peak shows only on FPD

4,6 Dimethyldibenzothiophene

4 methydibenzothiophene

TIC: Significant Hydrocarbon Response in Scan


LCO1

Methyl substituted DBT

Use extracted ion and SIM to gain selectivity

Identification of 4,6- Dimethydibenzothiphene


LCO 1

TIC

FPD

4,6 DMDBT

Cut: 23.8 to 24.0 min

Extracted Ions for 4,6- Dimethyldibenzothiophene


LCO 1

SIM: 4,6- Dimethydibenzothiophene


Cut: 24.8 to 25.0

LCO 1

SIM-SCAN: LC02


SCAN

SIM

FPD

Uncut dibenzothiophenes

Ions: 212, 211,197,105

50 to 250 amu

Extracted Ion Chromatogram: 4,6 Dimethyldibenzothiophene


LCO 2

212

211

197

105

165

FPD / SIM: 4- Methyldibenzothiophene


LCO 2

4 M DBT

FPD Plus: Higher Temperature Operation


• The FPD + has two temperature controlled zones> Emission block> Transfer line

• Maximum temperature is 400 °C for the inert transfer line

• New range of higher temp applications are possible

• Deans Switching (heart cutting) is used to minimize hydrocarbon quenching and help with identification

• Backflushing can also be implemented with the Deans system. This allows heavier feedstocks to be analyzed

Summary

• A Flame Photometric Detector available on the 7890B gas chromatograph is capable of operating at 400 C which enables a new range of applications particularly in the sulfur analysis of fuels , distillates, and feedstocks.

• To maximize selectivity and minimize co-elution, a Deans switch system is used. Heart cuts are made from a non-polar HP-1 or DB-1 column to a mid-polar DB-17HT column.

• CFT enables the Deans switch to be used in a backflush mode. Utilizing backflush with the Deans switch allows heavy distillates and feedstocks with carbon numbers over C50 to be analyzed without damaging the column set with temperatures above 350 C.

• The system can successfully determine the distribution of alkyl dibenzothiophenes in a wide variety of distillates, fuels, and feedstocks.

• A Deans FPD-MSD system adds additional compound confirmation possibilities


References

Xiaoliang Ma, Kinya Sakanishi, Isao Mochida, “Hydrodesulfurization Reactivities of Various Sulfur Compounds in Diesel Fuel”, Ind. Eng. Chem. Res. 1994, 33, 218-222.

S. Shin, H. Yang, K. Sakanishi, I. Mochida, D. Grudoski, J. Smith, “Inhibition and deactivation in staged hydrodenitrogenation and hydrodesulfurization of medium cycle oil over NiMoS/Al2O3 catalyst”, Applied Catalysis A, 205, 2001,101-108.

X. Ma, K. Sakanishi, I. Mochida, “Hydrodesulfurization Reactivities of Various Sulfur Compounds in Vacuum Gas Oil”, Ind. Eng. Chem. Res. 1996, 35, 2487-2494.

R.L. Firor, “An Improved Flame Photometric Detector for the Analysis of Dibenzothiophenes in Diesel, Distillates, and Feedstocks Using the Agilent 7890B Series GC”, Application Note 5991-1752EN, 2013.


analysis of alkyl dibenzothiophenes with the fpd + …...page 34 gulf coast conference 2013 title...

Documents