On-Line Acid Strength and Sulfuric Acid Alkylation Process
Control Using Process NMR
John Edwards and Paul GiammatteoProcess NMR Associates, LLC
Danbury, Connecticut
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Sulfuric Acid Alkylation
2CH3
CH3
CH CH3
CH3CH3
CH3
CH3
CH3
CH3
CH3+ H2SO4 (88-96 wt%)
Isobutene Isobutane Trimethylpentane
Composition of Sulfuric Acid Reaction Stream:• H2SO4 Acid• Water• Acid Soluble Oils (ASO)• Gaseous Hydrocarbons• Alkylate Product
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Process NMR :General Characteristics
• Radio Frequency Spectroscopy (~54 MHz)• Inherently Quantitative• Uniform Response/Sensitivity• Real Time Analysis• Sample State Independent (Solid,Liquid,Gas)• Sample Environment Independent (T, P)• Non-Invasive• Sample Conditioning Minimal
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Advantage of On-Line NMR Analysis
• Tighter Process Control • Fewer Process Disruptions• Improved Operating Efficiencies
> Lower Total Acid Costs *• Higher Productivity• Improved Safety* Amount Depends on Acid Supply Costs
Estimated that 1 wt% reduction of acid strength set point corresponds to 10% savings in acid costs
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Process NMR Installation Position
NMR
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On-Line Process NMR Unit
InstalledApril 1997
NMR DowntimeNone
DisruptionsBrief AC Failures
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Sampling Point From Reaction Zone
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Sample Lines In/Out of NMR
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Process NMR Spectrum of Acid/Hydrocarbon Emulsion
0
2
4
6
15 10 5 0 PPMAcid/Water Hydrocarbons
Intensity
Olefin
AcidSoluble
Oils
Alkylate + C3,C4,C5 HydrocarbonsCH3CH2
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NMR Calculated Parameters To DCS
•Acid Strength (Wt%)>Based on Chemical Shift
•Emulsion Character (HC/Acid Ratio)>Ratio of 2 Integrated Regions
•Saturate/Olefin Ratio>Ratio of 2 Integrated Regions
•ASO Content>Normalized Integration Region
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Hydrocarbon Region
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On-Line Process NMR DataThree Acid Emulsion Samples
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Chemical Shift Difference
Acid/Water Peaks at 3 Acid Strengths
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Full Range Predictive Equation
0 20 40 60 80 100Acid Strength (Wt%)
0
1
2
3
4
5
6
7
Ch
emic
al S
hif
t D
iffe
ren
ce (
ppm
)R2=0.99945th Order
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Operational Range Predictive Equation
80 85 90 95 100
Acid Strength (Wt%)
5.5
5.75
6
6.25
6.5
6.75C
hem
ical
Sh
ift
Dif
fere
nce
(pp
m)R2=0.9981
3rd Order
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Lab Versus Process NMR Comparison
87
88
89
90
91
92
93
NM
R A
cid
Stre
ngt
h (
Wt%
)
87
88
89
90
91
92
93
LAB
Aci
d St
ren
gth
(W
t%)
Day1 Day2 Day3 Day4 Day5 Day6 Day7
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Alternate NMR Approaches
• Process NMR at Settler (Rather Than Reaction Zone)
* Characterize the Spent Acid
> Utilize the Shift Difference Between ASO and Acid/Water Peaks
> Obtain Fewer Parameters (Acid Strength, ASO Content)
> Hydrocarbon Content of Spent Acid is not a Problem(no outgassing required)
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New Process NMR Enclosure Design
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Fuel Oil Streams
Vac
uum
Tow
er
Cok
er
FCCU*
HCDESAL
HTU
HTU
HTU
HTU
REF Ar EXT
Gas
Pla
nt
ALKY
Aromatics
Kerosene/Diesel
Fuel Oil
Coke
Gas
Lt Naphtha
Hv Naphtha
Kerosene
AGO
Crude
Resid
Olefins
i-C4
Reformate
FCC Gasoline
Naphtha
Gasoline StreamsDiesel/Kerosene/AvJet
HeavyOilUpgradingUnit
BlendHead
Process NMR in the RefineryP N A LPGPOLY
H2GenAlkylate
Atm
osph
eric
Tow
erGasoline
VGO
Lubricant Oils*or Visbreaker
Asphalt
Future Investigations
Feasibility Performed
Feasibility CompleteInstallations Scheduled
Current Commercial NMR Units
Future Applications - Diesel Blending
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12 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2 12 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2 ppm
Diesel
ppm
Light Jet
• Pour Point• Cloud Point• Distillation• Cetane Index• Gravity
• Sulfur• Flash• Viscosity• Water
Future Applications - Gasoline Blending
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11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4 11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4 12 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2 12 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2
Oxygenated Gasoline Gasoline
• RON• MON• Aromatics• Olefins• Distillation
• Oxygenate Content• Density• PNA Content• RVP
Future Applications - Heavy Ends
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11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4 11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4
Sour LCGO FC LCGO
11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4 11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4
11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4 11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4
FCCU Feed
11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4 11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4
Upgraded Heavy Oil
Future Applications - Light Ends
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12 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2 12 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2
Light Platformate
12 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2 12 10.8 9.6 8.4 7.2 6 4.8 3.6 2.4 1.2 0 -1.2
Heavy Platformate
11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4 11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4
Light FC Naphtha
11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4 11.8 10.6 9.4 8.2 7 5.8 4.6 3.4 2.2 1 -.2 -1.4
Heavy FC Naphtha
Acknowledgements
Ed Ross - Equilon (Los Angeles)
The Foxboro Company
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