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Name
UOP MOLEX
Owner
/ UOP LLC
Brand
MOLEX™
Process
Separation Processes
Type
Molecular Sieve Adsorption for Hydrocarbon Separation
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#TE426

Description

1. Executive summary

Molex is a continuous, liquid-phase adsorptive separation process developed by UOP (Universal Oil Products; today Honeywell UOP) to recover normal (linear) paraffins from isoparaffins, cycloparaffins and aromatics. It applies the UOP Sorbex simulated-moving-bed (SMB) technique to a Ca2+-exchanged zeolite A (5A molecular sieve), whose pores admit linear molecules and exclude all branched and cyclic ones [6][7][8].

The process was announced in 1959 for gasoline-range feeds [1] and extended in 1961 to kerosene and light gas oil, producing concentrates of up to 95% C10–C22 normal paraffins [2]. Its principal application is the production of C10–C14 normal paraffins from straight-run kerosene as feedstock for linear alkylbenzene (LAB) and biodegradable detergents [9][11]. A typical unit delivers about 99 wt% normal-paraffin purity at about 98 wt% recovery [9]; product purity is typically above 99.5% [7]. The raffinate returns to the refinery for jet-fuel blending [11][13].

UOP lists 37 Molex units licensed in its Sorbex portfolio [6][8]; product capacities of commissioned units range from 2,500 to 155,000 t/y [9]. Documented reference sites include Cepsa Química Puente Mayorga (Spain; Molex I and II) [16] and Farabi Petrochemicals (Yanbu, Saudi Arabia) [13].

2. Technology snapshot

Item Data
Licensor Honeywell UOP (predecessor: Universal Oil Products Co.) [3][13]
Process family Sorbex (simulated moving bed), rotary-valve design [8]
Separation Normal paraffins from isoparaffins, cycloparaffins and aromatics [9]
Adsorbent 5A molecular sieve (Ca-exchanged zeolite A) [7][8]
Phase / thermal regime Liquid phase, isothermal, continuous [2][9]
Typical feed Straight-run kerosene with 18–50% normal paraffins [11]
Carbon ranges C6–C10 plasticizers; C10–C14 LAB; C10–C18+ detergent alcohols [9]
Purity / recovery ~99 wt% / ~98 wt% [9]
First commercial Molex unit Start-up reported as 1960 [6] and 1964 [7][8]
Units licensed 37 (Sorbex portfolio table, as of July 2001) [6]

3. Process history

Year Milestone
1957 UOP files the Broughton–Gerhold patent on continuous sorption with a fixed sorbent bed and moving inlets and outlets (filed May 22, 1957; granted May 23, 1961) — the basis of the SMB/Sorbex technique [3].
1959 UOP begins licensing Molex. D. B. Carson presents it at the 47th Western Petroleum Refiners Association meeting (San Antonio): an isothermal fixed bed with continuous feed and product streams, moderate temperatures and pressures, ordinary construction materials. The initial target is gasoline octane improvement by n-paraffin removal; pentane/hexane feeds are paired with Penex isomerization [1]. The UOP rotary-valve patent (Carson and Purse) is filed April 10, 1959 [4].
1960–1964 First commercial Molex unit starts up; products serve biodegradable-detergent manufacture [6][7][8].
1961 UOP extends Molex to kerosene and light gas oil; the continuous pilot plant makes concentrates of up to 95% C10–C22 normal paraffins. The detergent industry's shift to linear alkylbenzene sulfonates creates the demand [2][10].
1965 UOP distributing-valve patent (Gerhold and Broughton) issued July 6, 1965 [5].
1989 Gasoline Molex commercialized for light-naphtha octane upgrading (C5/C6 normal paraffins to Penex) [7].
2002 26 Molex units commissioned, 3 more in design or construction; capacities 2,500–155,000 t/y [9].
2013 Latest LAB-complex designs combine Molex, Pacol, DeFine, PEP and Detal-Plus improvements for about 25% lower energy and capital cost [12].

Alternative n-paraffin adsorption technologies built in the early 1960s included vapor-phase processes from Union Carbide (IsoSiv), Esso, BP, Shell and Texaco; at least 12 kerosene-range adsorption plants were built worldwide [10].

4. Process summary, chemistry and adsorbent

4.1 Separation principle

The separation is physical; no chemical reaction takes place in the Molex step. Zeolite A in its calcium form has an effective pore opening of about 4.7 Å. Linear paraffins (kinetic diameter <4.4 Å) enter the pores; branched paraffins (e.g. isopentane, 6.2 Å), cycloparaffins and aromatics are completely excluded. Selectivity for linear molecules is therefore infinite and the adsorbent acts as a true molecular sieve [7][8].

Distillation cannot perform the separation because the boiling ranges of linear, branched and cyclic paraffins overlap in the C5–C6 and heavier ranges [7].

4.2 Adsorbent and desorbent

  • Cation exchange of zeolite A sets the pore size: the potassium form (3 Å) dries olefinic streams, the sodium form dries non-reactive hydrocarbons, and calcium substitution produces a pore that admits n-paraffins and excludes all other hydrocarbons [6].
  • The desorbent must be physically separable from the feed and product by boiling point and must compete with feed components for pore space. For paraffin separations a paraffin desorbent is the preferred family [6][7]; n-pentane is listed for C10–C14 n-paraffin recovery on calcium zeolite A [7].
  • Reliance Industries identifies its Molex adsorbent as ADS-14, a sodium silico-aluminate molecular sieve that extracts n-paraffins from hydrotreated C10–C14 kerosene by adsorption [19].
  • Olefins in the feed cause rapid loss of sieve activity; activity lost to carbon deposition can be restored by burning off the carbon [2]. Liquid-phase operation avoids the coke build-up of vapor-phase operation and allows continuous operation for many years without regeneration [9].

4.3 Catalysis

No catalyst is used in Molex. Catalytic steps occur upstream (Unionfining hydrotreating of the kerosene) and downstream (Pacol dehydrogenation, Detal-Plus alkylation) in the LAB complex [11][12].

5. Detailed process description

5.1 The Molex complex

Molex is delivered as part of a complex: prefractionation, kerosene Unionfining and the Molex unit [11].

 

Straight-runkerosene Prefractionation StripperRerun column Kerosene Unionfining Charge heaterReactor Product separatorProduct stripper S, N, oxygenate removal Molex unit Adsorbent chamberRotary valve Extract / raffinatecolumns n-Paraffins(to Pacol) Light kerosene (C9−) Heavy kerosene (C14+) Make-up H2 Light ends

Raffinate (iso- and cyclo-paraffins) to jet blending Figure 1 – Molex complex, simplified block flow diagram (after UOP 4217-19)

5.2 Step-by-step description

  1. Feed preparation. Any straight-run kerosene containing 18–50% normal paraffins is suitable [11]. Prefractionation columns (stripper and rerun) tailor the kerosene to the carbon range required; a C10–C13 product, for example, is produced by removing light kerosene (C9−) and heavy kerosene (C14+) [11][12].
  2. Hydrotreating. The kerosene is hydrotreated in a Unionfining unit — charge heater, reactor, product separator and product stripper, with make-up hydrogen, recycle gas and light-ends removal — to a low level of sulfur, nitrogen and oxygenates that protect the adsorbent. Hydrotreating severity is set by feed impurities and by the required raffinate quality; the raffinate can be designed to meet jet-fuel specifications [11].
  3. Adsorption (Sorbex SMB). The adsorbent chamber contains a stationary bed of 5A sieve divided into a number of beds, each supported on a grid with a flow distributor connected by a bed line to the rotary valve. The chamber has no top or bottom: a pumparound pump circulates liquid from the last bed to the first. Four net streams are distributed by the rotary valve: feed in, desorbent in, dilute extract out and dilute raffinate out. Only four bed lines are active at any moment; stepping the valve moves the injection and withdrawal points along the bed and so simulates counter-current movement of the solid [8]. The pumparound pump runs at four different flow rates, one for each zone passing it [7].
  4. Zone functions. Zone I (between feed and raffinate) adsorbs the normal paraffins; Zone II (between extract and feed) purifies the adsorbed phase by displacing non-normal components from the pores and voids; Zone III (between desorbent and extract) desorbs the normal paraffins with desorbent; Zone IV (between raffinate and desorbent) is a buffer that stops raffinate components reaching the extract [7][8].
  5. Extract and raffinate fractionation. The dilute extract passes through the rotary valve to the extract column, and the dilute raffinate to the raffinate column. Desorbent is recovered in both columns, collected in a desorbent surge drum, and recycled through the rotary valve to the chamber. The extract column delivers the high-purity normal-paraffin product; the raffinate column delivers the raffinate [8][9].
  6. Products. The normal-paraffin product is fractionated into the carbon ranges required downstream and typically feeds Pacol dehydrogenation [7]. The raffinate (isoparaffins and cyclic hydrocarbons) returns to the refinery for jet-fuel blending [11]; it has Jet A-1 quality when the complex is designed for it [13].

5.3 Molex unit process flow diagram

 

ACAdsorbent chamber RVRotary valve RaffinateChargeExtractDesorbent Mixed paraffin charge DSDDesorbent surge drum RCRaffinate column Rec. ECExtract column Rec. Dilute raffinate Dilute extract Raffinate product High-purity n-paraffin product

Desorbent recycle (pump and cooler) to DSD and rotary valve Figure 2 – Molex unit, schematic after UOP process design characteristics (AC, RV, RC, EC, DSD)

6. Feed, product and operating parameters

Parameter Value
Feed Straight-run kerosene; 18–50% n-paraffins [11]; 20–40% depending on crude [7]; 1961 pilot feeds: 23 vol% straight-chain [2]
Feed carbon range C10–C15 (reference design) [9]; C10–C22 from kerosene and light gas oil (1961 pilot) [2]
Feed pretreatment Hydrotreating to low sulfur, nitrogen and oxygenates; low olefins [2][11]
Phase Liquid phase, isothermal, continuous [2][9]
Pressure Moderate [2]
Temperature Not above the atmospheric boiling point of the charge stock [2]
Materials of construction Ordinary construction materials [1]
Normal-paraffin product ~99 wt% [9]; >99.5% [7]
Recovery ~98 wt%, depending on adsorbent quantity relative to feed volume [9]
Raffinate Isoparaffins, cycloparaffins; jet-fuel blending component [11]

Note: UOP does not publish numerical adsorption temperature, pressure, zone flow ratios, bed count, adsorbent inventory or desorbent circulation for Molex; these are provided in a licensor design basis.

7. Technology performance

7.1 Yield and selectivity

  • About 99 wt% normal-paraffin purity at about 98 wt% recovery [9].
  • Product purity typically above 99.5% with very low levels of cyclic compounds; C10–C13 normal paraffins at 99.5% [7][8].
  • Selectivity for linear versus branched and cyclic hydrocarbons is infinite on 5A sieve [7].
  • Gasoline Molex recovers n-C5 and n-C6 at about 95% purity and recovery [7].
  • Pilot-plant onstream efficiency about 90%; sieve life expected to exceed two years [2].

7.2 Pilot-plant material balance on light gas oil (1961)

Carbon number Feed (vol%) Product (vol%)
C9 0.1 0.3
C10 0.2 1.0
C11 0.2 1.6
C12 0.3 1.4
C13 0.5 2.0
C14 0.9 3.3
C15 1.6 7.3
C16 3.4 16.3
C17 4.8 25.8
C18 4.5 20.3
C19 3.6 13.0
C20 1.9 4.9
C21 0.4 1.3
C22 0.1 0.1
Total 22.5 98.6

7.3 Safety and environment

  • Liquid-phase isothermal operation at moderate temperature and pressure, with ordinary construction materials [1][2].
  • Vapor-phase adsorption requires large temperature and/or pressure variations and leaves residual coke needing cyclic regeneration; Molex avoids both [9].
  • The product supports biodegradable detergents: linear alkylbenzene sulfonates are degraded by bacteria in streams, whereas branched-chain detergents persist and cause foaming [2]. More than 85% of worldwide biodegradable detergent production uses Honeywell UOP process technologies [18].
  • Process heaters of the Molex II and Unifining II units at Puente Mayorga were designed for natural-gas firing [16].

8. Comparative economic performance

8.1 Reference economics

Case Data
1995 reference unit [9] Feed 383,000 t/y paraffinic kerosene (C10–C15, ~34% n-paraffins); 96,000 t/y n-paraffins at 99% purity; fully erected cost within battery limits about US$25 million (1995).
Utilities per tonne of product [9] Electric power 54.3 kWh; cooling water 5.1 m3 (15 °C rise).
1961 pilot-based estimate [2] 4,350 bbl/d kerosene or gas-oil feed (23 vol% straight-chain); 850 bbl/d n-paraffins; operating and overhead cost (excl. payout) 31 ¢/bbl of charge, equal to 58 ¢/lb of product; erected cost about US$2.5 million including initial sieve and chemicals.

Feed quality drives cost: prefractionation and hydrotreating may be needed to control contaminants that affect adsorbent life [9].

8.2 Molex versus fractionation (1959 pilot study, gasoline range)

Basis: 2,500 bbl/d mixed pentanes and hexanes feeding a Penex isomerization unit, product 100.3 research octane [1].

Item Penex + fractionation Penex + Molex
Investment (US$) 1,680,000 1,505,000
Operating cost (US$/day) 1,412 1,060
Isomerized product (bbl/d) 2,417 2,455
Fuel gas (106 Btu/d) 573 298
Added yield value (US$/day) 55 (fuel gas) 239 (product)

Molex separates mixtures that cannot be separated by fractionation; its capital and utility needs do not rise sharply with separation difficulty, whereas those of fractionation do [1].

8.3 Molex versus batch adsorption and vapor-phase adsorption

  • In continuous countercurrent operation the liquid composition at any bed level is invariant with time and every part of the bed works at all times; the height equivalent of a theoretical plate is about one third of that in batch chromatography, and for difficult separations batch operation can require 25 times more adsorbent and twice the desorbent circulation [6].
  • Kerosene IsoSiv (vapor phase) typically recovers 95 wt% of the normal paraffins at 98.5 wt% purity [10], against about 98 wt% recovery at about 99 wt% purity for Molex [9].

8.4 Current LAB-complex improvements

A 100 kt/y LAB plant built with the latest Molex, Pacol/DeFine, PEP and Detal-Plus designs achieves 25% lower energy cost and 25% lower capital cost, stated by UOP as a 50% improvement in internal rate of return. Molex-specific changes: shorter rotary-valve cycle times (higher throughput) and an added tertiary flush with reduced circulation and reflux rates (smaller columns, lower utilities) [12].

9. Commercial experience and deployments

9.1 Unit counts

Statement Reference
37 Molex units among 134 industrial Sorbex units (Parex 78, MX Sorbex 6, Olex 6, Sarex 5, Cresex 1, Cymex 1), as of July 2001 [6][8]
26 Molex units commissioned and 3 in design or construction (early 2002); capacities 2,500–155,000 t/y [9]
28 Molex units licensed (2004 and 2007 brochures) [11][20]

9.2 Reference installations

Site Facts
Cepsa Química (now Moeve), Puente Mayorga, San Roque, Cádiz, Spain Two Molex units (Molex I and II) and two Unifining units; Molex II and Unifining II were built in the 2002 expansion. First LAB plant at San Roque started in 1969 (HF alkylation); converted to Detal in 2021, raising LAB capacity by 50,000 t/y to 250,000 t/y. The Cepsa/Honeywell release of Jul 11, 2018 lists Molex, Pacol, DeFine and PEP with Detal-Plus as the integrated complex. Kerosene feed: 2.40 Mt (2021), 2.13 Mt (2022), 1.53 Mt (2023). Linear paraffins are a sales product. [14][15][16]
Farabi Petrochemicals, Yanbu, Saudi Arabia New complex announced July 2017 with Unionfining, Molex, Pacol, DeFine and Detal units; 246,000 t/y normal paraffins and more than 120,000 t/y LAB; feed: diesel from the Saudi Aramco refinery and kerosene from the Saudi Aramco ExxonMobil refinery in Yanbu; completion expected 2020. Farabi's first integrated normal-paraffin and LAB complex with UOP technology started in 2006; LAB capacity doubled in 2012. [13]
Reliance Industries Ltd, Raigad district, India (Patalganga) LAB route documented in a CESTAT (Mumbai) order: kerosene is prefractionated to C10–C14, hydrotreated, passed through the Molex unit (adsorbent ADS-14) for n-paraffin extraction, dehydrogenated in the Pacol unit and alkylated with benzene to LAB. Both LAB plants (Patalganga, Maharashtra and Vadodara, Gujarat; combined 135 kt/y) are licensed with UOP HF-alkylation technology and have captive normal-paraffin plants that also produce heavy (HNP) and light (LNP) normal paraffins. [19][21]
Egyptian Linear Alkyl Benzene (ELAB), Egypt (UOP LAB complex; Molex not named in the source) UOP licensed the original LAB unit in 2003; in 2026 Honeywell was selected to add new units and revamp existing assets to expand normal-paraffin production. [17]
UOP pilot plant, suburban Chicago Molex pilot work for the 1959 pentane/hexane studies [1]; a continuous pilot plant produced the 1961 kerosene and light-gas-oil concentrates [2].

10. Applications and downstream chain

  • LAB / LAS detergents (C10–C14): about 80% of normal paraffins are used for LAB [11]. Chain: Molex → Pacol (dehydrogenation to mono-olefins) → DeFine (diolefin hydrogenation) → PEP (aromatics removal) → Detal-Plus (formerly Detal; solid-bed benzene alkylation) → LAB [12][14][18]. Olex (olefin/paraffin adsorptive separation) is an optional additional step listed in the UOP LAB complex [18]; it recovers olefins from paraffin–olefin mixtures such as Pacol effluent [7][8].
  • Detergent alcohols (C10–C18+), plasticizers (C6–C10), solvents and lubricants [9][11].
  • Chlorinated paraffins: flameproofing agents, plasticizers and lube-oil additives; chlorinated waxes from normal paraffins are more stable to heat and ultraviolet light than those from non-normal paraffins [2].
  • Gasoline Molex: C5/C6 normal paraffins from light naphtha recycled to Penex isomerization; used to remove tetraethyl lead as an octane component [7].

11. References

  1. Chemical & Engineering News (American Chemical Society) — UOP Unveils Molex, vol. 37, no. 13, p. 39 (Mar 30, 1959)
  2. Chemical & Engineering News (American Chemical Society) — UOP Extends Range of Molex Process, vol. 39, no. 21, p. 56 (May 22, 1961)
  3. Universal Oil Products Co. (D. B. Broughton, C. G. Gerhold) — US 2,985,589: Continuous sorption process employing fixed bed of sorbent and moving inlets and outlets (May 23, 1961)
  4. Universal Oil Products Co. (D. B. Carson, F. V. Purse) — US 3,040,777: Rotary valve (Jun 26, 1962)
  5. Universal Oil Products Co. (C. G. Gerhold, D. B. Broughton) — US 3,192,954: Distributing valve (Jul 6, 1965)
  6. UOP LLC (S. A. Gembicki, J. A. Johnson, A. R. Oroskar, J. E. Rekoske), Kirk-Othmer Encyclopedia of Chemical Technology, Wiley — Adsorption, Liquid Separation (Jul 19, 2002)
  7. UOP LLC (S. Kulprathipanja, J. A. Johnson), Handbook of Porous Solids, Wiley-VCH — Liquid Separations, chapter 6.4 (Oct 10, 2002)
  8. UOP LLC (J. A. Johnson), Handbook of Petroleum Refining Processes, 3rd ed., McGraw-Hill — UOP Sorbex Family of Technologies, chapter 10.3, pp. 10.29–10.35 (2004)
  9. UOP LLC (S. W. Sohn), Handbook of Petroleum Refining Processes, 3rd ed., McGraw-Hill — UOP Molex Process for Production of Normal Paraffins, chapter 10.7, pp. 10.75–10.77 (2004)
  10. UOP LLC (S. W. Sohn), Handbook of Petroleum Refining Processes, 3rd ed., McGraw-Hill — Kerosene IsoSiv Process for Production of Normal Paraffins, chapter 10.6, pp. 10.69–10.71 (2004)
  11. UOP LLC — Molex Complex for Upgrading Refinery Kerosene to Normal Paraffins, brochure UOP 4217-19 (2004)
  12. Honeywell UOP (L. C. Erickson, S. W. Sohn, Y. K. Whang) — Energy Efficient Plant Designs for Linear Alkylbenzene (LAB), brochure 6035-1 (Apr 19, 2013)
  13. Honeywell UOP — Honeywell to Provide Detergent Manufacturing Technologies to Farabi Petrochemical Complex in Saudi Arabia (Jul 17, 2017)
  14. Honeywell (PR Newswire) — Cepsa To Convert Detergent Plant From Hydrofluoric Acid To Honeywell UOP Solid Bed Technology (Jul 11, 2018)
  15. Hydrocarbon Engineering — Cepsa to convert alkylation unit (Jul 12, 2018)
  16. Cepsa Química, S.A. — Declaración Medioambiental 2023, Cepsa Química Puente Mayorga (May 13, 2024)
  17. Oil & Gas Middle East — ELAB selects Honeywell technology to expand paraffin production in Egypt (May 11, 2026)
  18. Honeywell UOP — Detergents (accessed: Oct 9, 2026)
  19. Customs, Excise and Service Tax Appellate Tribunal, West Zonal Bench, Mumbai — Reliance Industries Limited vs Commissioner of Central Excise, Raigad, Appeal No. E/1432/06 (Jan 5, 2017)
  20. UOP LLC — UOP Molex Complex for Upgrading Refinery Kerosene to Normal Paraffins, brochure UOP 4522-27 (2007)
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