NMR of Sulfuric Acid Alkylation Process - Process NMR Associates

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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