纳孔材料进展

本书介绍了纳米多孔材料的*研究进展。首先介绍了分子筛膜制备、分离及工业应用。其次介绍了分子筛催化剂在芳烃化反应中的应用进展情况。接下来全面介绍了新型的微孔与介孔材料，例如，多孔非硅质金属氧化物材料、多孔合金材料、金属氧化物纳米复合物、多孔聚合物材料、微孔磷酸铝催化剂等内容。本书内容全面，附有大量图表来阐述相关内容，同时附有大量参考文献以供读者参考。本书适合化学化工、材料等专业的研究人员阅读使用。

编者
前言
第1章 沸石分子筛膜——现状和前景 Juergen Caro和Manfred Noack
    1.简介:建立概念
    2.沸石分子筛膜的制备
    3.沸石分子筛膜的分离特性
    4.沸石分子筛膜的工业应用
    5.新的合成概念
    6.未来展望
    致谢
    参考文献
第2章 沸石分子筛催化剂在芳构化过程中的进展 C. Perego和P. Pollesel
    1.简介
    2.沸石分子筛催化剂用于烃类芳构化反应
    3.二甲苯
    4.烷基化反应生产烷基苯
    5.结论
    参考文献
第3章 介孔非硅材料及其功能 Ajayan Vinu
    1.简介
    2.介孔非硅金属氧化物的制备
    3.介孔金属
    4.介孔合金和金属金属氧化物纳米复合材料
    5.介孔半导体
    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.总结与未来展望
    致谢
    术语表
    参考文献
第4章 含过渡金属微孔磷酸铝和微孔磷酸硅铝的催化作用 Martin Hartmann和S. P. Elangovan
    1.简介
    2.固体酸催化作用
    3.双功能催化作用
    4.氧化还原催化作用
    5.其他的催化应用
    6.结论和展望
    致谢
    参考文献
主题词索引

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).