編者

前言

第1章 沸石分子篩膜——現狀和前景 Juergen Caro和Manfred Noack

    1.簡介:建立概念

    2.沸石分子篩膜的制備

    3.沸石分子篩膜的分離特性

    4.沸石分子篩膜的工業應用

    5.新的合成概念

    6.未來展望

    致謝

    參考文獻

第2章 沸石分子篩催化劑在芳構化過程中的進展 C. Perego和P. Pollesel

    1.簡介

    2.沸石分子篩催化劑用於烴類芳構化反應

    3.二甲苯

    4.烷基化反應生產烷基苯

    5.結論

    參考文獻

第3章 介孔非硅材料及其功能 Ajayan Vinu

    1.簡介

    2.介孔非硅金屬氧化物的制備

    3.介孔金屬

    4.介孔合金和金屬金屬氧化物納米復合材料

    5.介孔半導體

    6.介孔聚合物

    7.介孔碳

    8.介孔氮化碳

    9.介孔氮化硼和介孔硼碳氮

    10.總結與未來展望

    致謝

    術語表

    參考文獻

第4章 含過渡金屬微孔磷酸鋁和微孔磷酸硅鋁的催化作用 Martin Hartmann和S. P. Elangovan

    1.簡介

    2.固體酸催化作用

    3.雙功能催化作用

    4.氧化還原催化作用

    5.其他的催化應用

    6.結論和展望

    致謝

    參考文獻

主題詞索引

CHAPTER1

Zeolite Membranes-Status

and Prospective

Juergen Caro1,and Manfred Noack2

1Leibniz University of Hannover,Institute of Physical Chemistry and
Electrochemistry,

Callinstr.3-3A,D-30167 Hannover,Germany

2Leibniz Institute for Catalysis at the University Rostock,Berlin
Branch (former ACA),

Richard-Willsta¨tter-Str.12,D-12489 Berlin,Germany

Contents

1.Introduction: Setting the Scene 2

2.Preparation of Zeolite Membranes 5

2.1.Peculiarities of zeolite membrane crystallization 5

2.2.Direct in situ crystallization on supports 8

2.3.Secondary crystallization using seeded supports 9

2.4.Use of silica nanoblocks as precursor 13

3.Separation Behavior of Molecular Sieve Membranes 14

3.1.Apparatus and definitions 14

3.2.Characterization of zeolite membranes by permporosimetry
18

3.3.Permeation of single components 22

3.4.Separation of binary mixtures 29

3.5.Case study: Hydrogen separation 33

3.6.Case study: Carbon dioxide separation 37

3.7.Membrane reactors on the laboratory scale 44

3.8.Micromembrane reactor 46

4.Industrial Applications of Zeolite Membranes 49

4.1.De-watering of ethanol and propanol by hydrophilic
zeolite

membranes 49

4.2.Ethanol removal from fermentation batches by hydrophobic
zeolite

membranes 54

4.3.Further R&D on zeolite membrane-based separation processes
57

4.4.Cost analysis: Need for cheaper supports 58

5.Novel Synthesis Concepts 62

5.1.Crystallization by microwave heating 62

5.2.Use of intergrowth supporting substances 65

5.3.Growth of oriented zeolite layers on supports 69

5.4.Bi-layer membranes 73

5.5.Metal organic frameworks as molecular sieve membranes 75

5.6.Functional zeolite films 79

5.7.Mixed matrix membranes 81

6.Outlook 82

Acknowledgment 84

References 84

Abstract

The introduction of industrial membrane-based separation
technologies can

dramatically reduce the separation costs in comparison with
thermally based

separation technologies.In addition,membrane technologies allow the
energy

effective use and recovery of both valuable raw materials and the
separation of

wastes.Organic polymer membranes are increasingly used,but they
suffer from

stability at elevated temperatures and toward attack of organic
solvents.

Therefore,much effort is put into the development of temperature
stable and

solvent resistant inorganic membranes.Pd-based metal membranes
for

hydrogen separation,perovskite-type membranes for oxygen separation
and

zeolite-type molecular sieve membranes are on the jump into the
industrial

practice.This increasing application of inorganic membranes in gas
separation-

and on a later timescale in chemical membrane reactors-is a slow
process.

Because of the high investment costs,many companies prefer to play
the role

of an“observer.”In this contribution,we reflect the state of the
art of zeolite

membranes.We report the first industrial application of zeolite
membranes in

bio-ethanol de-watering and parallel ongoing fundamental research
on

improving the thin zeolite layer crystallization on porous
asymmetric supports

following new synthesis concepts and the development of novel
diagnostics.In

this chapter,we also treat the molecular understanding of zeolite
membrane

separations since this knowledge is crucial for the proper use of
zeolite

membranes and for the exploration of new application fields.

1.INTRODUCTION: SETTING THE SCENE

Intelligent membrane engineering can help to realize the
process

intensification strategy.Integrated membrane separations and
new

membrane operations such as catalytic membrane reactors and
membrane

contactors will play a crucial role in future
technologies.However,so far no

inorganic membrane is used in large-scale industrial gas
separation.The

increase of the 235U isotope concentration in a 238U/235U mixture
from

0.7% in natural uranium to approximately 3.5% for nuclear fuel
applications

by separation of 235UF6 and 238UF6 on porous ceramic
membranes

according to the Knudsen mechanism1 with an ideal separation factor
of

1.0043 is an exception.However,nowadays exclusively gas centrifuges
are

used for uranium isotope separation.Membrane reactor technology has
a

huge potential in the development of processes that are more
compact,less

capital intensive,giving higher conversions and selectivities in
both

thermodynamically and kinetically controlled
reactions,respectively.

Membrane reactors are expected to save energy and costs of
feed/product

separation [1].So far,no high-temperature membrane reactor for
chemical

reactions is in industrial operation.The use of porous ceramic
filter

membranes in biotechnology is an exception.

Inorganic membranes such as ceramics,metals,and glass show
promising

properties different from the organic ones.They can be
backwashed

frequently without damaging the separation layer.Inorganic
membranes are

highly resistant to cleaning chemicals,they can be sterilized and
autoclaved

repeatedly at 130–180 1C and can withstand temperatures up to at
least

500 1C.These properties recommend them for biotechnological
processes

as well.Inorganic membranes should have longer life spans than
organic

ones.The life span of a typical hydrophilic organic membrane
is

approximately 1 year,of a hydrophobic membrane 2 years,and of

fluoropolymers up to 4 years [2].Inorganic membranes
are,however,much

more expensive than polymeric ones,and they are brittle.

Three types of inorganic membranes are near to a
commercialization:

Pd-based membranes in H2 separation,perovskites in O2
separation,and

zeolite membranes in shape-selective separations.The regular pore
structure

of a zeolite molecular sieve suggests that a thin supported zeolite
membrane

layer can discriminate between molecules of different size and
shape.The

pore diameter of the separating zeolite layer is in the range of
the kinetic

diameter of the molecules to be separated to force molecular
sieving as the

determining diffusional regime.Furthermore,beside the
molecular

exclusion effect,due to the interplay of mixture adsorption and
mixture

diffusion,reasonable separation effects on zeolite membranes can
be

expected according to specific adsorptive interactions and/or
differences in

the molecular mobilities.The rapidly growing progress in the field
of

zeolite membranes is reflected by some recent reviews [3–10].It
is,

therefore,not the aim of this contribution to give a comprehensive
picture

of zeolite membranes and to present all the fundamentals in
detail,but to

highlight and evaluate recent developments.

By the end of the 1980s,the idea was born to develop zeolite
membranes

and the first attempts to prepare them were reported,the first
patents were

claimed.With some pioneering papers,R.M.Barrer triggered the

experimental work on zeolite membranes [11,12].In parallel,he
contributed

Zeolite Membranes-Status and Prospective

to the theoretical understanding of mixture permeation through
porous

membranes [13,14].The first one and the last one of Barrers
altogether 407

publications were dealing with membranes [15,16].The unit Barrer of
gas

permeability (flux in moles per time and area through a membrane of
a given

thickness and pressure difference) honours R.M.Barrer (Section
3.1).

Today,LTA (Linde Type A) membranes in the de-watering of alcohol
by

steam permeation or pervaporation have reached the commercial
state.For

shape-selective separations,other zeolite membranes with structure
types

such as MFI and DDR (deca-dodecasil 3R) are already in the
technicum

scale [8,17,18].Further molecular sieve structures are tested as
membranes

(Table 1).Most progress in the development of molecular sieve
membranes

was achieved for MFI-type membranes (silicalite-1 and ZSM-5) since
their

preparation is relatively easy.They can be synthesized highly
siliceous,which

provides chemical stability and allows for oxidative regeneration
[7].

Therefore,this contribution will mainly deal with MFI-type
membranes.

Table 1 Claimed structures and common modifications of zeolite
membranes [20]

New ways of synthesis,improved permeation tests,and proper
applications

shall improve the zeolite membranes for their technical
use.Increasing R&D

activities are reflected by increasing publication activities
(Fig.1).It is the aim

of this contribution to summarize the state of R&D on zeolite
membranes as

a relative young branch of the inorganic membrane family,250 years
after the

discovery of zeolites by Cronsted [19].It will be shown that the
application

of a crystalline molecular sieve as a zeolite membrane layer offers
huge

promises but it is still a challenge in itself.

2.PREPARATION OF ZEOLITE MEMBRANES

2.1 Peculiarities of zeolite membrane crystallization

As it will be described in more detail in Section 3.1,for high
fluxes and a

proper handling of zeolite membranes,a thin zeolite layer with a
thickness

of 1–20 mm is crystallized on a mechanically stable
support.However,the

chemical compositions of the crystallization solutions and their
handling for

zeolite membrane preparation as a thin supported layer differ from
the

standard recipes for a zeolite powder crystallization
[21–23].

The following points are characteristic of the zeolite layer
crystallization

on supports [7]:

At sufficient supersaturation,heterogeneous nucleation takes place
on

both the geometric outer surface of the support and inside the
pores of

the support.If externally prepared seed crystals are attached to
the surface

of the support,primarily the crystal growth of the seeds takes
place but

the simultaneous secondary nucleation at the surface of the
seed

crystallites and in/on the support cannot be suppressed
completely.

Therefore,diluted crystallization solutions are used to prevent
the

formation of new seeds and to have only growth of the attached
seeds to

a continuous layer.

In the beginning of the growth of the seeds,the surface-to-volume
ratio

increases like in the case of the crystallization in the free
solution.This is

based on the effect that in the beginning of crystal growth,usually
a

parallel nucleation takes place,which results in a surface
enlargement.In

the subsequent process of crystal intergrowth,the individual
crystals

grow together to a continuous layer and the surface-to-volume
ratio

decreases drastically.

The diffusion of the precursor species in the solution is not rate
limiting.

Since crystal growth is controlled by a first-order surface
process,the

growth rate decreases with the reduction of accessible
surface.

For the crystal intergrowth that is important for the sealing of
voids

between crystals,the viscosity of the synthesis solution should be
low to

enable mass transport in narrow slits.The driving force of the
diffusion

process is the concentration gradient.Therefore,the low viscosity
should

be realized rather by higher temperatures than by dilution.Another
way

to decrease the viscosity consists in an increase of the pH,which
results in

a higher concentration of low-connected silica species.

During the crystal intergrowth of isolated crystals to a continuous
layer,a

large slit surface is in contact with a small volume of synthesis
solution.

Therefore,besides crystal growth,a strong heterogeneous
secondary

nucleation inside the slit can occur,which can lead to a closure of
the

macroscopic slit pore by many small crystals with
intercrystalline

transport pores between them.A post-synthesis thermal or
hydrothermal

treatment can result in a reorganization of these domains with
improved

membrane properties.

The starting chemicals for the preparation of the synthesis batch
should

be selected with the aim to have low salt concentrations in the
solution.

Whereas these salts are not disturbing in the formation of the
free

crystals,the incorporation of neutral salt species-especially in
multicrystal

layer formation-can be disturbing since defect pores are
formed

by their thermal decomposition (e.g.,NH4NO3 and carbonate

decomposition).

It was found in a large number of studies that it is de facto
impossible to

crystallize defect-free Al-containing zeolite layers.Because of the
strong

negative surface charge (zeta potential) of Al-containing
zeolites,the

intergrowth of the crystals in the membrane layer is poor,and the
grain

boundaries represent defect pores in the mesopore region.This
holds

true for both the in situ-growth and the secondary growth with
seeds.By

using Intergrowth Supporting Substances (ISS),the crystal
intergrowth

in the zeolite membrane layer can be improved (Section 5.2).