Spectra are from as-synthesized materials and. are referred to ThlS ..56 Figure 3.3 Nitrogen adsorption at 77K extracted. sulfonated phenethyl-functionalized Beta and calcined Beta after pretreatment under vacuum at. 77 Figure 4.2 XRD patterns of aminopropyl beta, Top: the extracted one. aminopropyl beta, h: extracted aminopropyl beta, c: calcined beta. The illustrated slight weight gain is due to incorrect buoyancy corrections in the TGA.80 Figure 4.5 Raman spectra of aminopropyl silica (Aldrich), From.
S. Patent Application
CHAPTER ONE
Introduction and Objectives
Introduction
These cations reside within the micropores of the zeolite and are therefore accessible to adsorbed species. When the cations are protons, the zeolites are solid acids capable of promoting acid-catalyzed reactions within the micropores of the molecular sieve crystals. However, smaller molecules that are able to diffuse into the molecular sieve react across the active sites.
Scheme 1.1
- OFMS Synthesis
- Objectives
- References
Subsequently, Ahmad and Davis studied the functionalization of the molecular sieve SSZ-33 by grafting and found similar results [14]. Synthetic routes for the synthesis of OFMSs that both required and did not require an organic SDA were evaluated, with the investigations leading to the synthesis of the first OFMSs. Incorporation of an organic species followed by modification of the species using organic chemical techniques.
CHAPTER TWO
Investigations into the Synthesis of OFMS's from Hydrophilic,
Organic SDA-free Gels
- Introduction
- Experimental .1 Syzthrsis
- Results and Discussion .1 Zeolite syntlzesis .1 Zeolite syntlzesis
- Summary
For shape-selective applications, the organic groups must be largely located within the micropores of the zeolite. This indicates that the organic species in these materials reside in places other than the micropores of the zeolite. Thus, in the case of this organosilane, a fraction of the functional groups may be located within the zeolite micropores.
Wave Number (cm-')
CHAPTER THREE
Organic-Functionalized Molecular Sieves (OFMS's)
Organic-Functionalized Molecular Sieves as
Introduction
Zeolites and related crystalline molecular sieves possess intracrystalline voids of uniform size and shape that can be used to control the nature of the products obtained from chemical reactions taking place within the crystals. Because most of these materials contain acidic sites, it is not surprising that shape-selective, acid-mediated reactions, for example the formation of para-xylene, dimethylamine and para-ethyltoluene, are accomplished commercially with zeolites [II]. Moreover, there are a limited number of laboratory-scale results showing that other classes of catalysis, e.g.
It is clear that the range of active sites available in zeolites is quite restrictive compared to antibodies, enzymes. In order to expand the classes of shape-selective catalytic chemistries possible using zeolites and crystalline molecular sieves, we have prepared a new family of shape-selective catalysts, namely organic functionalized molecular sieves. These materials provide the means to create a wide range of active site types, opening new opportunities for design-selective catalysis.
Results and Discussion
It is clear from the spectrum of the hybrid material that the phenethyl group is covalently linked to a framework silicon atom (peak at -68 ppm: C-Si-OSi, [9,14]). Organic functionalities on the outer surface of the beta crystals can be removed by reacting the as-synthesized material with concentrated sodium hydroxide solutions (-8 M NaOH, 5% methanol, 2S°C, 1 hour). Subsequently, extraction of TEAF from the hybrid material is possible by repeated exposure to acetic acid water mixtures at.
Substantially complete removal of TEAF is achieved for the sample described here (>99% removed as determined by thermogravimetric analysis and I3C MAS NMR). The extracted organic-functionalized molecular sieve is sulfonated by contact with steam from 30% SO,/H,SO, - at room temperature after heating to -100°C under less than Torr vacuum overnight. Scanning electron microscopy (SEM) images of this fully modified material look no different than images of the as-prepared materials.
Prior to use as a catalyst, the solid is dehydrated at -100°C for at least 6 hours under less than Torr vacuum. The reaction of a cyclic ketone with ethylene glycol is used to illustrate the catalytic activity and form selectivity of sulfonated and extracted phenethyl. This activity is due to the phenyl-sulfonic acid groups covalently linked to the zeolite framework.
All OFh4S synthesis intermediates and the unfunctionalized pure silica materials are not active catalysts.
Scheme 3.1
- Methods
- References
The results clearly indicate that on BetalPEThlSIS0,H the phenylsulfonic acid site is the active center Ha). Addition of a small poison that can penetrate the pores of the molecular sieve, triethylamine (Et,N), stops all reaction after 0.5 h, as indicated by the data in Figure 3.5. As an additional control, phencthyl sulfonic acid sites are prepared on the surface of CPG-210. This material has a uniform pore diameter of 240 Å and cannot be a shape-selective catalyst.
Thus, the shape selectivity of the OFMS catalyst is demonstrated by the fact that NPM poisons all active sites in CPG-240PETMS/SO,H but has little effect on Thus, the aluminosilicate is not as shape-selective due to the reactivity of the outer crystal surface. The pores in the h.1Chl-41-type mesoporous materials can be narrowed to the micropore region by silanization treatments.
Organic-functional materials of the type described here offer new opportunities for shape-selective catalysis. So far, we have prepared OFhlS using zeolite beta (TEAF as SDA), ZSM-5 (hexamethylenediamine as SDA) and NaY and placed multiple functional groups in their structures. The reactor was charged with 10 g of toluene, 10 mmol of reactant in the case of HEX or 3 mmol in the case of PYC, and 13 mg of catalyst.
A few drops of phenolphthalein solution were added to the filtrate and then this solution was titrated to neutrality with 0.001 M NaOH.
CHAPTER FOUR
Organic-Functionalized
Molecular Sieves (OFMSSs)
Synthesis and Characterization of OFMSSs with Polar
Functional Groups
Organic-functionalized Rlolecular Sieves (OFMS's)
Synthesis and Characterization of OFRlS's with Polar Functional Groups
- Introduction
- Experimental
- Results and discussion .1 Synri?esis of OFhfS's .1 Synri?esis of OFhfS's
For the case of the reaction of aminopropyl-linked beta with DMBA, the specific procedure is given below. This is probably due to the increased homogeneity of the reaction components in the synthesis gel when using TEAF. Several methods were investigated for the extraction of TEAF from synthesized pure silica beta (not functionalized with organic groups).
This is also a characteristic of calcined beta and indicates that SDA has been removed from the material. The CP-MAS NMR spectrum of extracted aminopropyl-bonded beta is shown in Figure 4.3. TGA analyzes of the synthesized and extracted aminopropyl-beta materials are given in Figure 4.3 with the results of calcined pure beta silica.
There is a large weight loss from 200 to 400°C and this is the typical temperature range for combustion of SDA. Elemental analyzes of the extracted aminopropyl-beta (C: 1.3%, N: 0.2% and Si: 42%) are in reasonable agreement with the TGA results (R-SiISiO, calculated from the carbon to silicon ratio is 0.024). It is clear that the organic moieties are present in OFhlS, but the integrity of the functional groups and their locations need to be determined.
While DMBA is small enough to migrate into the pores of the BEA structure, DMNA is not.
Scheme 4.1
- Summary
- Extracted aminopropyl-beta, B: Calcined aminopropyl- beta
The spectrum of aminopropyl-beta contacted with DMBA (Figure 4.6-top) has an intense band at 1640 cm-' while this peak is hardly observed after contact with DMNA (Figure 4.6 middle). The apparent location of the aminopropyl groups is within the pores of the BEA structure. This is the case of cyclohexane adsorption; The amount absorbed in aminopropyl-beta is 0.226 ml/g sample while calcined.
If the aminopropyl group density is assumed to be similar to I-propylamine (0.719 glml), the amount of aminopropyl groups within the aminopropyl-beta material calculated from these data is R-Si/Si02=0.025 which agrees very well with the results. of TGA (0.027) and elemental analysis (0.024). On contact with DMNA, aminopropyl-silica turns yellow while aminopropyl-beta turns very faintly colored. Aminopropyl-silica contacted with DMBA and DMNA have intense absorption below 500 nm [Figure 4.8-c and Figure 4.9-c) as expected.
This intense peak is also observed in the spectrum of aminopropyl-beta in contact with DMBA (Figure 4. 8 4 k, is around 350 nm). However, there is an additional shoulder at 470 nm in the spectrum of the aminopropyl beta in contact with DMNA, which is not seen in calcined beta. Thus, a trace amount of imine can be formed by contacting the aminopropyl-beta with DhINA.
The color and spectrum of the material obtained by reacting aminopropyl-beta (without ammonia pretreatment) with DMBA are similar to those of aminopropyl-beta (yellow) treated with ammonia, while acid-treated aminopropyl-silica gives a red color. product that has a.
CHAPTER FIVE
Synthesis, Characterization and the Transformation of
Functional Groups into Solid Acids
Organic-Functionalized Molecular Sieves (OFhllS's)
I1 Synthesis, Characterization and the Transformation of OFMS's containing Non-Polar Functional
Groups into Solid Acids
Introduction
We recently reported the first synthesis of crystalline, microporous silicates with organic functionalities covalently bound within the micropores [I]. These materials (designated organically functionalized molecular sieves (OFMS)) have been shown to be suitable for the design of shape-selective catalysts based on organic active sites. In both cases, the vast majority of both aminopropyl 121 and phenethyl [I] groups were shown to be located within the micropores.
Therefore, various organic groups can be incorporated into the micropores by design (aromatic, sulfonic acid [I]; amine, imine 121). These materials hold promise for low-temperature applications, liquid-phase catalytic applications, and molecular recognition, as the active sites can be tailored to the needs of the reaction of interest. In addition, the synthesis of *BEA containing several other organic moieties is provided to further demonstrate the breadth of this approach.
- Results
- Discussion
- References
Incorporation of aluminum or boron into the gel results in the formation of the aluminum and horosilicate forms of BetalPE. The XRD patterns of the synthesized materials are identical for the samples synthesized in the presence and absence of PE. The XRD patterns of the samples synthesized with variable amount of PE are shown in Figure 5.3.
These are present in addition to the smaller crystals that can be seen in other parts of the image. Clearly, the integrity of the PE group in this extracted material is unchanged by the extraction method. Raman spectroscopy allows elucidation of the nature of the organic species in the OFMS materials.
If Beta-S is extracted by method 3 at an elevated temperature (120°C) in an autoclave, the porosity of the sample decreases. Previously, we reported the synthesis of the molecular sieve "BEA in the presence of various organosilanes [2]. The properties of the OFMSs can be tailored by the choice of synthetic (crystal size) and extraction method (hydrophobicity, pore volume).
The high hydrophobicity of the calcined samples is due to the defect-free nature of the material (all Q4 silicon). As the amount of PE in the synthesis increases, there is evidence of the formation of an additional, amorphous phase. Sulfonation of the synthesized material results in the formation of no sulfonic acids, indicating this.
CHAPTER SIX
