Dr. Junhang Dong (PI)Dr. Robert Lee (Manager)

Mr. Liangxiong Li (Ph.D. student)Dr. Xuehong Gu (Postdoc)

Report of Research Progress In 2003

Petroleum Recovery Research Center (PRRC)New Mexico Institute of Mining and Technology

Patent Pending

ACKNOWLEDGEMENTS

New Mexico Tech: the president’s office provided $100K for equipment

DOE: funding through the NPTO in NETL under contract No. DE-FC26-00BC15326

Petroleum Recovery Research Center, A Division of the New Mexico Institute of Mining and

TechnologyPRRC

PRRC/NM Tech:Delivery is our Job #1

• A research arm of New Mexico oil and gas industry, only for oil and gas industry, dedicated to industry’s interests alone.

• PRRC/NM Tech research directions are governed by its advisory board members including:(1) New Mexico Oil & Gas Association (NMOGA)(2) Independent Producers Association (IPANM) (3) New Mexico Oil Conservation Division (NMOCD)(4) New Mexico State Land Office (NMSLO)

• NMOGA, IPANM, NMOCD, and SLO are policy-making organizations but PRRC/NM Tech is for research only.

AcknowledgementNPTO/NETL/DOE State of New Mexico (Governor, Senators, Representatives)NM Tech President Office (Dr. Lopez)NMOGA, IPANM, NMOCD, and SLO(Bob Gallagher, Deborah Seligman, Jeff Harvard, Tucker Bayless, Lori Wrotenbery, and Jami Baily)

PRRC Separation group members:Dr. Junhang Dong (group leader)Ashlee RyanXuehong GuAditi MajumdarKatsuya SugimotoAmber WoodyattLiangxiong Li

• PART I: Desalination of Produced Water– Supported clay membranes– Zeolite membranes

• PART II: CO2 Separation By Clay Membranes– Development of PILC membranes for high temperature

CO2 capture– Preliminary results on plain clay membranes

• PART III: Nonoxidative CH4 Conversion– Concept of the new catalytic membrane– Proof of concept

Presentation Plan

PART I

Desalination of Produced Water

• Supported Clay Membranes

• Zeolite Membranes

Stainless steel mold for mounting the compacted clay membrane

Schematic showing the mechanism of desalination on clay membranes

1. Compacted bentonite membranes as thin as 60m were prepared.

2. Desalination was demonstrated on compacted clay membranes.

3. Problems: — Not suitable for produced water due to the rapidly diminishing ion rejection with increasing ion concentration. — Too brittle to be practical. — Extremely low flux due to thickness.

• For practical applications, supported, thin membranes must be developed

Previous Work

Refining of clay nanoparticles (dia.< 50 nm) from commercial powders

1. Dispersion2. Washing & centrifuging3. Freeze drying

Redispersion of nanoparticles

PVA Binder

pH control

Colloidal suspension for membrane coating: 0.7 wt% clay + 0.05 wt% PVA pH = ~7.5

Membrane Synthesis Route

Dip-coating or slip-casting

Controlled drying:40oC, ~60%RH

Calcination: 0.5oC/min; 450 - 600oC

SEM Pictures of the Alumina-Supported Clay Membrane

Cross-section Surface

Membrane thickness = 2 ~ 3 mBET surface area = ~ 60 m2g-1

Mesopore volume = ~ 0.075 cm3g-1

Mean pore size = 5 ~ 9 nm

TEM image of the clay membraneparticle size: dia. < 50 nm

0 10 20 30 40 502

Rel

ativ

e In

tens

ity

A

B

C

XRD patterns. A – -alumina substrate, B – refined powders fired at 600°C, C – -alumina-supported clay membrane

fired at 600°C

Material Characterizations

Water bottle

Sample collector Feed outlet

Feed tank

Water analysis

Membrane cell

Feed pressure control

Flow control valve

Feed solution

High pressure N2 cylinder

The RO Desalination System

The cell

The I.C.

Calcination

conditions

Thickness,

m pf

*, MPa Flux, mol·m-2·h-1 r, %

450oC for 3h ~2.0 0.41 34.11 4.5

500C for 3h ~2.0 0.82 8.33 44.5

600C for 3h ~2.0 No flux under feed pressure of up to 1.03 MPa

700C for 3h ~2.0 No flux under feed pressure of up to 1.03 MPa

Results of RO Desalination for a 0.1M NaCl Solution

%100)(

)()(

feeds

permsfeeds

CCC

rRejection:

pf is the applied pressure.

Mem* Solution

m

Pf

MPa

Flux

mol·m-2·h-1

Permeance

mol·m-2·kPa-1·h-1

Permeability

mol·m-1·kPa-1·h-1 r, % Ref.

CP 0.60M NaCl 2200 27.4 0.088 3.21x10-6 7.06x10-8 60.0 ( 2 )

CP 0.8M

NaCl+0.15M CaCl2

5000 13.9 0.452 3.25x10-5 1.62x10-7 60.0 ( 5 )

CP 5.04M NaCl

+ 0.45M CaCl2

16,000 13.8 0.275 1.99x10-5 3.19x10-7 25.0 ( 6 )

CP 0.10M NaCl 60 5.2 7.22 1.38x10-3 8.33x10-8 62.9 ( 7 )

SP 0.10M NaCl 2 0.82 5.5 6.71x10-3 1.34x10-8 44.5 This study

Comparison Between Supported Membrane and Compacted Membranes

* CP – compacted membrane; SP – supported membrane

ab PP

pfa pp

FP

FP

tAQFm

w

MwRT

CC

CC

feeds

s

perms

s

100100

1. Supported mesoporous clay membranes have been synthesized for the first time

2. The supported thin membranes is superior to the compacted membrane:

- Mechanical strength- Rejection comparable to the compacted - High flux and low operation pressure

3. Clay membranes are less likely to succeed in the real world- Structurally unstable in aqueous conditions (swelling)- Rejection lost in high concentration solution

4. Potentially excellent for CO2 and other gas separation

5. Need new membrane with separation mechanisms not inhibited by high concentration

Conclusions for Clay Membranes

• Separation mechanisms – Molecular sieving– Selective adsorption– Diffusion

• Current synthesis methods– In situ crystallization– Seeding/secondary growth– Vapor-phase transport

• Extensively studied for gas separations

• Not explored for RO desalination

Film formation

Nucleation Crystal growth

Zeolite Membranes

MFI dp: 5.6Å

• Computer simulation showed 100% Na+ rejection on zeolite-A perfect membranes• RO test for EtOH/water separation on A-type zeolite membrane

Rejection of hydrated ion by molecular sieving effect through intracrystal pores

Two types of pores in polycrystalline membranes:(1) Intracrystal pore (zeolitic) and (2) intercrystal pores

Rejection by overlapping double layers in intercrystal pores

5 m

MFI membrane synthesized by seeding-secondary growth. No template used

MFI membrane synthesized by in situ crystallization method (templated).

MFI Membranes Synthesized by Different Methods

0 100 200 300 400 500Temperature, C

-2.5

-1.5

-1.0

-0.5

0.5

1.0

1.5

-2.0

0.0

Ther

mal

exp

ansi

on/c

ontra

ctio

n ra

tio, %

o

MFI zeolite on alumina support

MFI zeolite on YZ support

MFI zeolite powder

Fitted line

a

aa

a 25 C after template removalo

Mismatch of thermal expansion between the

MFI layer and substrates

Microstructure Evolution for Supported MFI Membranes During Template Removal

Strong bonding between zeolite layer and support formed prior to H.T. (e.g.

on alumina)

Illustration of an intercrystal pore

0 20 40 60 80 100Time, h

0.15

0.25

0.35

0.10

0.20

0.30

0.40

Flux

, kg

m h

-10

10

20

30

50

60

70

0

40

80

Reje

ctio

n (R

), %

-2

-1

Flux

Rejection

Water Flux and Na+ Rejection as Functions of OR Operation Time for the 0.1M NaCl Solution

Flux 50% higher than supported clay membranesRejection almost twice as high as that on supported clay membranes

25 75 1250 50 100 150Time, h

-20

-10

10

20

30

50

60

70

90

100

0

40

80

Reje

ctio

n (R

), %

Na

K

NH

Ca

Mg+

+

+4

2+

2+

Ion Rejection as a Function of Operation Time for a Multicomponent Feed Solution

Feed composition

NaCl 0.1M

KCl 0.1M

NH4Cl 0.1M

CaCl2 0.1M

MgCl2 0.1M

(Total ~ 80,000ppm)

Overall rejection (stabilized) ~ 80%Stabilized water flux ~ 0.6 - 0.12 kg/m2 h

New Synthesis Method: Wet Gel VPT-Seeding and Secondary Growth

5 m

Step 2Secondary growth

Step 1 Wet gel VPT

1. First demonstration of RO desalination on zeolite membranes

2. Highly stable structure and unique separation mechanism- Can handle high concentration (produced water)- Can tolerate organic materials - High rejection and flux

3. Issues that need further investigation- Zeolite with different pore size- Minimize intercrystal pores and thickness- Better understanding of separation mechanism and effects of

operation conditions- Tests with real produced water- Finding cheap way to fabricate membrane

4. Promising results obtained on a new synthesis method of VPT and secondary growth

- Better reproducibilty- Higher success ratio (low cost)

Summary for Zeolite Membranes

PART II

CO2 Separation with Clay Membranes

• A new type of PILC membrane for high temperature CO2 separation

• Preliminary results on plain bentonite membranes

• High temperature CO2 capture is the key to realizing CO2 sequestration strategies.

• Current industrial methods are not economical.

• Membrane approach is energy-saving, thus the future direction.

- Polymeric membrane for T<150oC- Organic-inorganic composite membrane for T<300oC but has low permeability- Ceramic membranes for T>300oC but has very low

selectivity, S<2

• Challenge: developing highly CO2-selective, porous inorganic membranes

Current Status

ASSUMPTIONS: i) Chemisorption of CO2 and negligible N2 adsorption; ii) Single layer adsorption, = Kp. iii) CO2 transport via surface diffusion with minimized Knudsen flow

2

2

)()(

NK

COKsc P

PPS

CO2 permeability of surface diffusion (Ps)

Selectivity (Sc) of CO2/N2 for a 50/50 feed

WK M

RTRT

rP

832

Permeability of Knudsen diffusion (PK)

RTaQ

rANKDP c

As

)1(exp200

Requirements for A Porous Ceramic Membrane — Theoretical Analysis

THEORETICAL MODEL

-alumina (A) MgO/-alumina (B)

d/dp (Pa-1) 8x10-7 9x10-7

-Qc (kJ mol-1) 45 56

T (K) 543 573

Ds (kJ mol-1 K-1) 1.8x10-8 8.1x10-9

Ps (mol m-1 s-1 Pa-1) 2.7x10-11 1.2x10-11

(PK)CO2 (mol m-1 s-1 Pa-1) 5.8x10-12 5.6x10-12

(PK)N2 (mol m-1 s-1 Pa-1) 7.3x10-12 7.1x10-12

CO2 permeance (PCO2) (mol m-2 s-1 Pa-1) 3.28x10-6 1.76x10-6

Selectivity SCO2/N2 for a 50/50 feed 4.5 2.5

Calculated CO2/N2 separation on mesoporous membranes (dp=10nm, thickness=10m) — influence of adsorbing strength

(assuming negligible viscous flow)

* Based on data of Horiuchi et al., 1996.

Requirements for A Porous Ceramic Membrane

Ideal scenario of adsorption-diffusion membrane separation

(1) Pore diameter < 1 nm to inhibit Knudsen diffusion and increase the selectivity.

(2) Optimal CO2 adsorbing strength to maximize the permeability and selectivity.

(3) Large microporous surface area to enhance the surface diffusion permeability

OLIGOMERIC HYDROXY METAL CATIONS e.g. [Al13O4(OH)24(H2O)12]7+ (Vercauteren et al., 1996)

CLAY SHEETS (LAYERS)

DRYING AND RE-CALCINATION

METAL OXIDE PILLARS ION XECHANGE

The Proposed Microporous PILC Membrane

(1) Established membrane synthesis method.

(2) Controllable pore size between 4Å to 30Å by adjusting pillaring materials.

(3) Adjustable surface adsorbing strength, from physical adsorption to chemisorption, by ion-doping and pillaring.

Surface modification by alkali metal oxides

Test of CO2 Separation on Plain Clay Membrane

1 3 50 2 4 6Perm eation tim e, h

5.0

15.0

25.0

0.0

10.0

20.0

30.0

Sepa

ratio

n fe

acto

r for

N2

over

CO

2 25 C

100 C

Knudsen factor = 1.25

o

o

Separation of a 50(CO2)/50(N2) mixture on the mesoporous bentonite membrane

(1) Weak adsorption — adsorption heat: 15 - 33

kJ/mol.

(2) Mesoporous (6-9nm) — Knudsen flow is significant.

(3) Adsorption of CO2 on the pore surface slows down the transport of CO2.

(4) Membrane in good quality — indicated by selectivity greater than Knudsen factor.

(5) Microporous PILC membranes needs to be developed.

PART III

Novel Catalytic Membrane for CH4 Conversion to C2+ and H2

• Concept• Catalytic membranes synthesis• Preliminary results

Background

1. DOE and the energy industry seek more efficient and cleaner new technology for natural gas conversion to H2 and C2+

2. Oxidative membrane reactor — membrane instability, low conversion at high selectivity; emission of CO2, high reaction temperature >850oC …

3. Direct CH4 conversionAdvantages:

- 100% selectivity - Low operation temperature, 250~450oC- Zero CO2 emission …

Disadvantages:- Thermodynamically limited two-step process- Endothermic and very low equilibrium conversion

Principle of Nonoxidative CH4 Conversion

A new membrane reactor must be developed to overcome the two-step limitation and the thermodynamic barrier

Pulse Feed Reactor

Illustration of continuous operation of single-step CH4 conversion through a zeolitic channel

Mechanism of the New Catalytic Membrane

Feed side Membrane Permeate side

MS

Reactor

The Experimental System

Pt-Co/NaY

NaY only

Ionic and Catalytic Membrane Characterization Apparatus

0 10 20 30t(m in )

0

1E-008

2E-008

3E-008

4E-008

5E-008

AM

PS

2E-010

4E-010

6E-010

8E-010

AM

PS

m /e=44

m /e=16

A

0 10 20 30t(m in )

0

1E -008

2E -008

3E -008

4E -008

5E -008

AM

PS

0

2E-010

4E-010

6E-010A

MP

S

m /e=44

m /e=16

B

Proof of Concept

Results of CH4 conversion on Pt-Co/NaY Membrane

C3H8

CH4

CH4

A: The main product of conversion on the Pt-Co/NaY membrane is C3H8, which accounts for ~80% of the total C2+. Membrane deactivated in ten min due to excessive carbon formation on the catalyst surface — significantly longer than in pulse feed reactor (<one min).

B: On a NaY membrane without catalyst under identical conditions. No intensity change at m/e=44 (C3H8) was observed, proving that C3H8 was generated in a single-step, continuous manner on the Pt-Co/NaY membrane.

Nonoxidative In Situ Membrane Regeneration

0 40 80 120 160t(m in)

0

2E -008

4E -008

6E -0080

2E -0114E -0116E -0118E -011

0

5E -010

1E -009

1 .5E -009

AM

PS

0

1E -011

2E -011

3E -0110

1E -011

2E -011

3E -011m /e=72 (C 5H 12)

m /e=58 (C 4H 10)

m /e= 44 (C 3H 8)

m /e=30 (C 2H 6)

m /e=16 (C H 4)

1. Minor increases in the intensities of m/e = 30 (C2H6), 44 (C3H8), 58 (C4H10), 72 (C5H12) were observed within the first 10 minutes after introducing CH4 into the feed.

2. In about 120 minutes after introducing CH4, significant increases in conversion rate of m/e = 30 (C2H6), 44 (C3H8), 58 (C4H10), 72 (C5H12).

3. The results suggest that (i) the carbon deposit was in reactive forms; (ii) activation of Co might take longer time than Pt; and (iii) the Pt-Co bimetallic catalyst had higher catalytic activity than single metal (Pt).

4. Deactivation significantly reduced.

Using H2 to rehydrogenate reactive carbon deposit

• The new type of metal-loaded zeolite membrane, e.g. Pt- Co/NaY membranes, can overcome the two-step limitation of nonoxidative CH4 conversion into C2+ and H2.

• Other metal-loaded microporous membranes, e.g. microporous silica membranes, microporous pillared clay membranes, and microporous carbon membranes, etc., may also be used for such purpose.

• A breakthrough in the area of nonoxidative CH4 conversion.

• This invention may lead to a completely new technology for efficient conversion of natural gas into more valuable higher hydrocarbons and hydrogen.

Summary for PART III

First realization of direct conversion of CH4 into C2+ and H2 by Continuous Operation

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