GB2084552A - Silica polymorph - Google Patents

Abstract

A new silica polymorph exhibiting a similar X-ray powder diffraction pattern to Zeolite ZSM-5 is produced by inclusion of phosphate or sulphate ions in the silica so reaction mixture which is refluxed or autoclaved. The polymorph exhibits improved thermal stability and an absence of an infrared adsorption band at a wave number of 700 cm<-1>.

Description

SPECIFICATION Silica polymorph This invention relates to crystalline silica polymorphs having a zeolite crystal structure similar to that of zeolite ZSM-5.

A large number of articles and patents on molecular shape-selective catalysis have been published in the literature since the first article by Weisz and Frilette which were issued almost two decades ago.

(J. Phys. Chem., 64,382(1960)).

Recently a group of crystalline aluminosilicates, designated as those of the ZSM-5 type, have been found to be shape selective. This group of zeolites is particularly described in U.S. Patent No.

3,702,886. These zeolites have been synthesized, for example, from a solution containing an oxide of aluminum or gallium, an oxide of silicon or germanium, an oxide of sodium, a tetraalkylammonium hydroxide and water. This group of zeolites is characterized by a specific X-ray diffraction pattern.

Another group of crystalline compounds which are mostly silica have been shown to have a ZSM-5 type X-ray pattern. Examples are silicalite and a silica polymorph which are described in U.S.

Patents 4,061,724 and 4,073,865, respectively.

In the present invention we report the synthesis of novel silica containing crystalline compounds, which are essentially free of aluminum and have, surprisingly, been found to have an X-ray diffraction pattern similar to that of the ZSM-5 type crystalline aluminosilicates. These materials are synthesized from a mixture containing an oxide of sodium (or potassium), an oxide of silicon, tetraalkyl or tetraarylammonium cation, sulfuric acid or its salt, or phosphoric acid or its salt and water.

The product of the present invention, when prepared under autogenous pressure and using an acid (or its salt) in the mix, are extremely stable towards heating. They consist of well separated twinned rectangular prismatic crystals exhibiting extreme uniformity in size and shape. The crystal size and thermal stability can be controlled depending on the nature of the acid and the pressure at which the synthesis is carried out The absence of the acid leads to a mixture of relatively high pH. This mixture, when crystallized under autogenous pressure, leads to yet another product composed of relatively large crystalline nests.

The nests are made of rectangular prismatic crystals that are growing into each other.

The above products contain SiO2, (TPA)20, Na2O and in all except the last, occluded phosphorous or sulfur. The product could also contain very low levels of alumina which is attributed primarily to alumina impurities in the raw materials used. The sodium can be removed by first firing the material in air at 5370C. followed by treatment with H+ or NH+4 containing solution. The treated product is then calcined in air.

Materials of this invention are useful as catalysts for organic compound conversion and as selective sorbents.

SPECIFIC PREFERRED EXAMPLES OF THE INVENTION EXAMPLE 1 a. A reaction mixture was prepared by dissolving 650 gm NaOH in 11000 cc H20, followed by the addition of 872 gm H3PO4 and 851 gm (C3H7)4NBr (TPABr). To the resulting solution 3375 gm of silica sol (40% by weight SiO2) were added with continuous agitation.The overall reaction mixture, which had a pH of 10.8, had the following oxide mole ratios: P,OdSiO, = 0.20 Na2O/SiO2 = 0.36 (TPA)20/SiO2 = 0.07 H20/SiO2 = 33.10 The synthesis mixture was placed in a five gallon jacketed autoclave equipped with a helical agitator and an oil heating unit, and allowed to crystallize at 1 450C. The mixture was maintained at that temperature for 52 hours, during which intermediate samples were withdrawn, filtered, washed with water then dried overnight at 1 100C.

b. Portions of the solids obtained in Example 1-a were subjected to X-ray analysis. The data are summarized in Table I.

The X-ray powder diffractions of samples listed in Table I were obtained by standard technique.

The K-alpha doublet of copper was the radiation source, and a scintillation counter spectrometer fitted with a strip chart pen recorder was employed. The peak heights and their positions as a function of two times the Bragg angle (theta) were read from the spectrometer chart. The relative intensities, 100 1/1,.

where 1o is the intensity of the strongest peak, and the observed interplanar spacing in Angstrom units (d) corresponding to the recorded lines were then determined.

The samples listed in Table I all showed the same X-ray pattern. Table II shows a typical X-ray diffraction pattern.

Portions of samples a and g of Table I were examined by scanning electron microscopy (SEM).

Both samples were highly crystalline and consist of well separated highly twinned curved edge rectangular prismatic crystals exhibiting extreme uniformity in size. Sample a (6 hour autoclaving time) showed extremely small amounts of amorphous material. The sides of the individual crystals measure about 5.5 x 9 x 3.5,um. SEM of sample g after air calcination at 5370C. for four hours was quite the same as that without calcination.

The composition of sample g of Table I was 8.66 wt% C, 0.68 wt% N, 80.21 wt% SiO2, 0.12 wt% Na2O and 0.08 wt% P205 content remained the same upon airfiring the sample at 5370C. forfour hours.

EXAMPLE 2 The DTA of samples a through g of Table I were measured. All samples showed the same DTA; several intense bands at 350-5000C; and a symmetrical exotherm of a lower intensity at 1093 l 70C.

EXAMPLE 3 This is a duplicate of Example 1 except that the intermediate samples were taken at slightly different times, namely 2, 4, 5.5, 12, 30,46 and 54 hours. As in Example 1, the collected washed and dried solids were analyzed by X-ray. The lines at 10.78, 9.82 and 3.80 A started to develop in the two hour samples. Between 4 and 5.5 hours of crystallization times the X-ray pattern, showed in Table II, was fully developed.

EXAMPLE 4 Portions of samples a, e, and g of Table I were calcined in air at 5370C. for four hours. The resulting products were then subjected to X-ray analysis. The diffraction patterns were all the same.

Table Ill shows a typical X-ray diffraction pattern. The technique used in collecting the data of Table Ill is described in Example 1-b.

EXAMPLE 5 Portions of samples a, e and g of Table I were calcined in air at 5370C. for four hours. The thermogram (DTA) of the resulting products were then measured. The 350-5000C. bands of Example 2 disappeared. The high temperature exotherm was still there but was slightly shifted towards a lower temperature (1076 + 40 C.). Also a broad weak endotherm centered at about 11 50C. appeared.

EXAMPLE 6 Portions of the calcined e and g samples of Example 5 were refluxed for two hours with 17% solution of ammonium acetate. The ratio of solution to powder was 10:1 by weight. The DTA of the isolated washed and dried (1100) solids showed that the 350--5000C. bands and the high temperature exotherm have disappeared.

EXAMPLE 7 a. An aqueous solution of 410 gm NaOH and 455 gm of 96% H2SO4 in 11222 cc H2O was prepared. While the solution was being stirred, 851 gm of tetra-n-propylammonium bromide (TPABr) was added. To the resulting solution 3375 gm of silica sol (40% by weight SiO2) was added with continuous stirring. The mixture after stirring for 15 minutes, had a pH of 10.95. The composition, in terms of mole oxide ratios, was: St:)31siO2 = 0.20 Na2O/SiO2 - 0.23 (TPA)20jSiO2 = 0.07 H20/SiO2 = 32.97 The reaction mixture was autoclaved at 145 C. for 69 hours. As in Example 1-a, intermediate samples were withdrawn, filtered, washed then dried at 110 C b. Portions of the collected solids in Example 7-a were analyzed by X-ray. The data are summarized in Table iV.

Sample c through h all had the same X-ray pattern which is described in Table II. Only the strongest bands were about 2530% developed in sample b.

SEM examination of sample i shows the same type of crystal morphology seen in the phosphorous based product of Example 1. There are some differences, however. In this example the crystals are larger (12.5 x 11 x 5 Hm) and the twinning contains more than two crystals. The crystal size and morphology did not change upon calcining the sample in air at 537 OC. for four hours. Sample c (12 hour autoclaving time) showed some amorphous materials when examined by SEM.

Chemical analysis of sample i showed the following composition: 8.85 wt% C, 0.79 wt%N, 77.41 wt% SiO2, 0.085 wt% Na2 0.04 wt% SO2 The SO2 content stayed at 0.04 wt% upon air firing the sample at 5370C. for four hours.

EXAMPLE 8 Portions of the sulfuric acid (or sodium sulfate) samples c through i of Table IV were calcined in air at 537cC. for four hours, then analyzed by X-ray. All samples showed the same X-ray pattern as described in Table Ill.

EXAMPLE 9 Samples C through i (made with sulfuric acid) of Table IV were analyzed by DTA. All samples showed the same thermograms as described in Example 2 with the exception that the high temperature exotherm (10941 70C.) was absent. in fact, no bands were seen in the 500-11 1 100C. temperature range. Upon calcining these samples at 5370C. for four hours in air the 350-5000C. bands disappeared.

COMPARATIVE-EXAMPLES A AND B Samples of silicalite and a silica polymorph were prepared according to U.S. Patent 3,702,886 and U.S. Patent 4,073,865, respectively. The silicalite was prepared by adding a solution of 14.2 gm (C3H)4NBr in 68 cc H20 to 160.7 gm Ludox (Registered Trade Mark) HS-40 silical sol (40% SiO2) with manual stirring. This mixture was mixed with another solution, containing 6.1 gm NaOH in 101 cc H2O, using manual stirring. The overall mixture thus had a molar oxide composition of 2.0 (TPA)20, 6.5 Na2O, 80SiO2, 1105 H2O (Na2O/SiO2=0.081; (TPA)2/SiO2=0.025; H2O/SiO2=13.81). The mixture was placed in a stainless steel bomb, sealed and heated at 2000C. for 43 hours.The product was thereafter recovered by filtration, followed by washing and drying at 11 00C. from the X-ray analysis the product was free of quartz and was identified as silicalite. This sample was used for further studies. (Another mixture was autoclaved at 2000C. for 72 hours - the product showed quartz).

The silica polymorph was prepared by adding a solution of 8.0 gm NH F dissolved in 39 cc H20 to 154 gm Ludox HS-40 silica sol (40% SiO2) diluted with 71 cc H20. To this was added a solution of 5.7 gm NaOH in 20 cc H20, followed by the addition of another solution containing 13.8 gm (C3H7)4NBr in 39.2 cc H20. The overall mixture thus had a molar composition of 0.791 SiO2.0.063 Na2O. 0.166 NH4F, 0.02 (TPA)20. 11.2 H20 (Na20/SiO2 = 0.080; NH4F/SiO2 = 0.210; (TPA)20/SiO2 = 0.025; H20/SiO2 =14.159). The mixture was placed in a stainless steel bomb, sealed and heated at 2000C. for 92 hours.

The product was recovered by filtration, washed then dried at 11 00C. From the X-ray analysis the product was identified as silica polymorph described in U.S. Patent 4,073,865 (the pattern showed no quartz).

Portions of the silicalite and silica polymorph were analyzed by DTA. Both samples showed the 350-5000C. bands seen previously. The silicalite showed an exotherm at 9600C. (including the one which showed quartz). The silica polymorph showed none in the 500-11 000C. temperature range.

Samples of the silicalite (quartz free) and silica polymorph were also examined by SEM. The silicalite product consists of twinned crystals in which the surface is striated (layered structure). The silica polymorph consists of rather large rod shaped crystals.

EXAMPLE 10 One-tenth by weight of the reaction mixture described in Example 1-a was placed in a three liter flask fitted with a condenser and a mechanical stirrer. The mixture was allowed to reflux for 700 hours under atmospheric pressure. Intermediate samples were collected, filtered, washed, then dried at 11 00C.The collected solids were analyzed by DTA and X-ray. The data are summarized in Table V.

SEM of sample j shows that the crystals have the same morphology as that of Example 1 with the exception of more twinning and smaller crystal size (3.5 x 5 x 1.75 m).

EXAMPLE 11 One-tenth by weight of the reaction mixture described in Example 7-a was placed in a three liter flask fitted with a condenser and a mechanical stirrer. The mixture was allowed to reflux for 700 hours under atmospheric pressure. Intermediate samples were collected, filtered and then dried at 110 C. The collected solids were analyzed by DTA and X-ray. The data are summarized in Table VII.

For convenience, the high temperature (500-11 000C) DTA bands of products of the present invention, silicalite and silica polymorph are listed in Table VI.

Again, the same twinning was obtained but the crystal size was much smaller than that of Example 10.

EXAMPLE 12 The infrared (IR) of sample b of Table I, sample h of Table IV, sample f of Table V and sample k of Table VII were measured on wafers containing 2 mg sample and 200 mg KBr. Also the IR of silicalite and silica polymorph of comparative Examples A and B were recorded.

Silicalite and silica polymorph showed a weak, well defined band at 700 cam~: as opposed to none in samples of the present invention (acid based products).

EXAMPLE 13 Portions of sample g in Table I, sample i in Table IV, sample j in Table V and sample k in Table VII were simultaneously air fired at 5370C. for four hours. The silicalite and silica polymorph of the comparative example were fired at 6000 C. for two hours in air. This is the recommended temperature according to U.S. Patents 4,061,724 and 4,073,865. All samples were then refluxed for two hours with 17 wt% solution of ammonium acetate. The ratio of solution to sample was 10:1 by weight. The samples were then filtered followed by thorough washing with water. This step was repeated once more followed by drying at 1 1 OOC. overnight.

Portions of the above samples were simultaneously air fired in shallow beds at 5370C. for four hours. Using fresh samples more firings were carried out at 1200, 1250, 1300 and 1 3500C. for various times. All samples were then subjected to X-ray analysis. In addition to these samples, a commercial hydrogen mordenite powder from the Norton Company was air fired at 11 500 C. for two hours, then analyzed by X-ray.

No decline in crystallinity was detected at 5370C. (same as in Table Ill). Crystallinity of these materials was considered a reference. The crystallinity of the 1200-1 3500C. fired samples was calculated using the following formula: Sum of intensity X-ray lines at d = 1 1.05 A, 9.94 A, 3.83 A and 3.71 Aof material a, fired at TOC x 100 %Crystallinity = Sum of intensity X-ray lines at d 1 1.05 A, 9.94 A, 3.83 A and 3.71 Aof material a, fired at 5370C.

The data are presented in Table VIII. The table also includes other phase(s) which developed at certain firing temperature/time. Only one crystalline phase could be detected from X-ray, namely alphacristobalite which is a form of silica.

The hydrogen mordenite sample was completely decomposed (amorphous) at 11 500 C.

EXAMPLE 14 Portions of autoclaved and refluxed H3PO4 and H2SO4 product, silicalite and silica polymorph of Example 1 3 were tested for N2 sorption. The data were collected at liquid nitrogen temperature and a nitrogen partial pressure of 0.20. In addition, the BET surface area was also measured. Both data are shown in Table IX.

SUMMARY OF EXAMPLES 1 TO 14 EXAMPLE 1 This example simply describes the synthesis of the crystalline organosilicate using phosphoric acid in the formulation. It also shows that the product reaches maximum crystallinity after about six hours of crystallization. The fact that the X-ray pattern remained unchanged for 52 hours, indicates that the product is highly stable under the synthesis conditions.

It also shows that the product contains an organic component, namely a tetrapropylammonium compound and a phosphorus containing component. The fact that the phosphorous content remained the same after calcining the material at 5370C. for four hours suggests that it (phosphorous) is present in a nonvolatile form.

Another important observation is the extreme uniformity in crystal size, which was maintained throughout the entire autoclaving period. Also there was no crystal deformation or shrinkage upon calcining the product at 5370C. in air.

EXAMPLE 2 Here we show the thermal behaviour of the product upon calcination in air. The 350-5000C.

DTA bands are due to the decomposition of the tetrapropylammonium component. The exotherm at 1 0930C. indicates a phase transformation.

EXAMPLE 3 This is a duplicate of Example 1 which shows that the synthesis procedure is reproducible.

EXAMPLE 4 This example shows that calcining the product in air at 5370C. leads to a change in composition and/or crystal structure as indicated by the change in the X-ray diffraction.

EXAMPLE 5 Here we provide more evidence of the presence of the tetrapropylammonium (TPA) component in the product as indicated by the disappearance of the 350-5000C. DTA bands when the material was previously calcined. The 1076 + 40C. DTA exotherm indicates that the product retains its high temperature phase transformation when the TPA component is removed. The 11 50C. weak endotherm is attributed to water.

EXAMPLE 6 This example shows that the transformation, which occurs at 1 0760C. in the calcined product (made from the H3PO4 containing mix) does not take place upon treating the sample with ammonium acetate. This indicates that the product, before the ammonium treatment, contains sodium whose presence destabilizes the structure.

EXAMPLE 7 Here we show that using sulfuric acid in the mix leads to a product which has the same X-ray diffraction pattern as the phosphoric acid based product. Also the product contains the PTA component and sulfur. As in the phosphoric acid based product the sulfur exists in a nonvolatile form as indicated from the composition (same sulfur content) of the 5370C. fired sample.

The SEM examination indicates that the H2SO4 based product crystallizes somewhat slower than the H3PO4 derivative. Another observation is the extreme uniformity in crystal size. Neither the crystal size nor their uniformity change even with 69 hours of autoclaving time. This was also seen in the H3PO4 based products. Notice also that the H2SO4 product crystals are larger than that H3PO4 material. This illustrates that the nature or strength of the acid dictates the crystal size. Another difference between the two products (H2SO4 and H3PO4) is that the twinning in the H2SO4 based products consists of more than two crystals.

EXAMPLE 8 This example shows that calcining the H2SO4 based product gives an X-ray pattern similar to that of the calcined H3PO4 based material.

EXAMPLE 9 Here we show that the product (calcined or uncalcined) prepared from a sulfuric acid based mix, does not behave the same as that made with H3PO4, when heated in air from 500-1 1000C. This is shown by the absence of the 1 0930C. exotherm which appeared in the phosphorous case. The 350-5000C. DTA bands indicate that the uncalcined product, just like that made with the H3PO4, contain the TPA component.

COMPARATIVE EXAMPLES A AND B Here we show that the DTA's of silicalite and the silica polymorph, which have similar X-ray patterns, are different from the HYPO4 based product. The silicalite has an exotherm at 9600C. as opposed to 1 0930C. in the H3PO4 product. The silica polymorph showed none in the 500-11 000C.

temperature range.

The crystal morphology of silicalite and silica polymorph are different from all species of the present invention. The silicalite exhibits the same twinning but the individual crystals do not have sharp boundaries as in others. Also the crystal faces are striated (layered structured).

EXAMPLE 10 This example shows that refluxing the H3PO4 based mixture leads to a crystalline product which has the same X-ray pattern as that prepared by autoclaving (autogeneous pressure). The rate of crystallization, however, is low. The product of this example still contain the TPA component (the 350-5000C. DTA bands). It differs, however, from the autoclaved product when heated in air at 500-11 000C. This is shown by the absence of any DTA bands in this temperature range.

Another difference between the product of this example and that prepared by autoclaving is in the morphology and size of the crystals. The product made by refluxing appears to have more twinning and most importantly, the size of the crystals are much smaller than the autoclaved material. This small crystal size might be desirable in certain catalytic applications. Crystals of both products (refluxed and autoclaved) show the same high degree of uniformity in size.

EXAMPLE 11 Here we show that refluxing.the H2SO4 containing mixture leads to a crystalline product which has the same X-ray pattern as that prepared by autoclaving. The product still contains the TPA component as indicated by the 350-5000C. DTA bands. It differs, however, in behaviour from that prepared by autoclaving as indicated by the presence of a DTA exotherm at 950-1 0050C. when heated in air. As in the refluxed H3PO4 based product, the rate of crystallization is low.

For comparison Table VI shows the 500-11 1 OOcC. portion of the DTA of products of the present invention, silicalite, and silica polymorph.

Crystals of this example still have the same high degree of uniformity in size and twinning seen in previous examples. The crystals, however, are much smaller in size (1-2.5 ,um) than any of the other products (autoclaved H3PO4 and H2SO4 and refluxed HYPO4 products).

The crystal size decreases in the following order: autoclaved H2SO4 material > autoclaved H3PO4 material > refluxed H3PO4 material > refluxed H2SO4 material.

EXAMPLE 12 This example shows that the products of the present invention (made in the presence of acid by autoclaving or refluxing) are structurally different from silicalite and the silica polymorph. This is because silicalite and the silica polymorph have IR bands at 700 cam~' as opposed to none in products of the present invention. Bands in the mid-infrared region (200-1 300 cm-') do represent structural characteristics of zeolite frameworks. (Breck, D. W., "Zeolite Molecular Sieves," John Wiley and Sons, N.Y. (1974), page 415).

EXAMPLE 13 This example shows that including an acid in the mix (as exemplified by H2S04) and carrying out the reaction under autogeneous pressure leads to products which have exceptionally high thermal stability. This thermal stability is much higher than that of silicalite, silica polymorph, and H-mordenite.

The data of this example were collected on the ammonium salt treated materials, i.e. soda was removed (the mordenite was in hydrogen form). In almost all catalytic applications, it is desirable that the catalyst has very little or no soda.

Based on the results of this example the thermal stability decreases in the following order: autoclaved H3PO4 based product > autoclaved H2SO4 based product > silicalite > refluxed H3PO4 based product ~ silica polymorph > refluxed H2S04 based product H-mordenite.

This example also shows that the thermal stability can be varied depending on the nature of the acid used and the pressure at which the synthesis is carried out.

EXAMPLE 14 This example shows that the H2SO4 and H3PO4 based products (autoclaved and refluxed) have porous structures as indicated by their large affinity to adsorb nitrogen and their large surface area.

These characteristics make these products useful as catalysts for organic compound conversion and as adsorbents.

EXAMPLE 15-CATALYSIS A portion of sample g of Table i (autoclaved H3PO4 product - 52 hours) was calcined in air at 537 C. for four hours. This was followed by two treatments with NH4OAc solution as described in Example 6. The resulting powder was extruded into 1/1 6" pellets using 20% Al203 (source of Awl 203 was boehmite). The pellets were dried at 1 1 OOC. then air fired at 5370C. for five hours.

The pellets, 20 cc, were loaded into a tubular reactor and subjected to a feed of normal pentane and H2 at a temperature range of 254-3740C. The n-pentane was converted to other hydrocarbons which are listed in Table Xl. The table also shows detailed operating conditions under which the catalyst was tested.

This example illustrates that the autoclaved H3PO4 product is active for n-pentane conversion to other hydrocarbons. The total conversion and selectivity to cracked products increased as the temperature was raised. The total conversion increased exponentially with temperature.

Close examination of the data reveal that at low temperature (254-31 60C) the isomerization activity dominates over hydrocracking, whereas at high temperatures (31 6-3750C.) the hydrocracking activity is the preferred one. It is interesting to note that the CsHs is the major component among the cracked products. The relative amounts of cracked products decrease in the following order: C3H8 > i-C4H1o + n-C4H10 > H2H6, CH4 EXAMPLE 16-CATALYSIS Some of the ammonium acetate treated powder of Example 1 5 was extruded into 1/1 6" pellets using 5% Al203. The pellets were dried at 1 1 OOC. then air calcined at 537 CC. for five hours. The resulting catalyst was then subjected to n-pentane conversion using similar conditions to those employed in Example 15 except that the liquid hourly space velocity (LHSV) was increased from 1.00 to 1.25 hr-1. Results and detailed operating conditions are shown in Table Xil.

This example further illustrates that the autoclaved H3PO4 based product can be used as a catalyst for n-pentane conversion to other hydrocarbons of different molecular weights as seen in Example 1 5.

The fact that the activity was lower than that seen in Example 1 5 is because the space velocity was higher, which means a shorter contact time between the feed and the catalyst.

EXAMPLE 17 METHANOL CONVERSION At the end of the testing of Example 1 6, the catalyst was kept in the reactor and subjected to a feed of methanol. The testing was carried out at one atmosphere, LHSV of 1.25 hrs and temperature of 429 and 4470C. The results are summarized in Table XIII.

Here we show that the autoclaved H3PO4 based material is active for converting methanol to other hydrocarbons. Some of the products were identified as being C1-C4 hydrocarbons. The rest are high molecular weight hydrocarbons which could be either aliphatic or aromatic in nature.

The results of this example confirm that the product is a shape selective type zeolite.

EXAMPLE 18 Nitrogen sorption and BET surface area of autoclaved H3PO4 and H2SO4 based products, silicalite and refluxed H3PO4 product, which were air fired at 1 3000C. for two hours (see Table VIII - Example 13), were measured. The data are shown in Table X. The table also shows data of materials fired in air at 5370C. for four hours. As in Example 16, the 1 3000F. firing data were collected at liquid nitrogen temperature and a nitrogen pressure of .20.

In this example we provide more evidence supporting the fact stated in Example 1 3 t'hat the thermal stability of the autoclaved acid based products are much higher than that of silicalite. For example, in case of the H3PO4 based product, about 21% of the nitrogen sorption capacity or surface area was retained after calcination at 1 3000C. for two hours - the silicalite retained only 7.4%. The retained N2 sorption and surface area of the H2SO4 derivative (12.613.2%) were also higher than that of silicalite.

TABLE I CRYSTALLINITY VS CRYSTALLIZATION TIME OF UNCALCINED PRODUCTS (H3PO4 based mix, Example 1-b) Crystallization Time Sample hours X-ray Diffraction a 6.0 Highly Crystalline b 12.5 Highly Crystalline c 22.0 Highly Crystalline d 30.0 Highly Crystalline e 36.0 Highly Crystalline f 46.0 Highly Crystalline g 52.0 Highly Crystalline TABLE II TYPICAL X-RAY DIFFRACTION PATTERN OF UNCALCINED PRODUCTS (H3PO4 based formulation, Example 1-b) d (A) Relative Intensity 10.78 Medium-Strong 9.82 Medium-Strong 9.61 Medium-Weak 8.85 Weak 7.38 Medium-Weak 6.97 Weak 6.61 Weak 6.28 Medium-Weak 5.99 Medium-Weak 5.91 Medium-Weak 5.64 Medium-Weak 5.50 Medium-Weak 4.93 Weak 4.55 Medium-Weak 4,,33 Medium-Weak 4.23 Medium-Weak 3.97 Medium-Weak 3.80 Very-Strong 3.72 Strong 3.69 Strong 3.62 Strong 3.43 Medium-Weak 3.33 Medium-Weak 3.29 Medium-Weak 3,03 Medium-Weak 2C97 Medium-Weak 2.92 Weak 2.71 Weak 2.59 Weak 2.48 Weak 2.39 Weak 2.00 Medium-Weak 1.99 Medium-Weak 1.95 Weak 1.91 Weak 1.87 Weak 1.65 Weak 1.48 Weak TABLE Ill X-RAY DIFFRACTION PATTERN OF CALCINED PRODUCT (H3PO4 based formulation, Example 4) d (A) Relative Intensity 11.05 Very-Strong 9.94 Very-Strong 9.72 Medium-Weak (Shoulder) 6.61 Weak 6.33 Medium-Weak 5.95 Medium-Strong 5.64 Medium-Strong 5.54 Medium-Strong 5.31 Weak 4.96 Weak 4.58 Weak 4.35 Weak 4.23 Medium-Weak 3.97 Weak 3.83 Very-Strong 3.82 Strong (Shoulder) 3.74 Strong (Shoulder) 3.71 Strong 3.62 Medium-Weak 3.43 Weak 3.29 Weak 3.04 Weak 2.98 Medium-Weak 2.94 Weak 2.73 Weak 2.61 Weak 2.47 Weak 2.38 Weak 2.01 Medium-Weak 1.99 Medium-Weak 1.95 Weak 1.91 Weak 1.87 Weak 1.66 Weak TABLE IV CRYSTALLINITY VS CRYSTALLIZATION TIME OF UNCALCINED PRODUCTS (H2SO4 based mix;Example 7-b) Crystallization Time Sample hours X-ray Diffraction a 2.5 Mostly Amorphous b 5 Crystalline c 12 Highly Crystalline d 21 Highly Crystalline e 29 Highly Crystalline f 36 Highly Crystalline g 45 Highly Crystalline h 53 Highly Crystalline 69 Highly Crystalline TABLE V DTA AND CRYSTALLINITY VS CRYSTALLIZATION (H3PO4 based mix/reflux, Example 10) Crystallization Time Sample hours X-Ray 1 DTA2 a 24 Amorphous b 48 Amorphous c 72 Crystalline d 96 Crystalline e 168 Highly Crystalline 350-500 C. bands f 192 Highly Crystalline g 216 Highly Crystalline 350-500"C. bands h 267 Highly Crystalline 350-500"C. bands 578 Highly Crystalline 350-5000C. bands 700 Highly Crystalline 350-500"C. bands Samples e through j showed the same X-ray pattern as in Table II of Example 1-b.

The band intensities of samples c and d were 45 and 80% respectively when compared to the other highly crystalline samples.

No bands appeared between 500 and 1110CC.

TABLE VI DTA OF VARIOUS CRYSTALLINE SILICA CONTAINING COMPOUNDS 500-11000C. RANGE (Example 11) Material * Exotherm Temperature, C.

H3 P04 based product Autoclaved (Example 1) 1093 + 7 H2SO4 based product (Autoclaved (Example 7) None Acid-free product Autoclaved (Example 10) 915-1035 H3PO4 based product Refluxed (Example 12) None H2SO4 based product Refluxed (Example 13) 950-1003 Silicalite (Example 11) 960 Si I icapolymorph None * All material showed the 350-5000C. DTA Bands.

** Work was carried out under a secrecy agreement with Amoco.

This information is for internal use ONLY.

TABLE Vll DTA AND CRYSTALLINITY VS CRYSTALLIZATION TIME (H2SO4 Based Mix/Reflux, Example 11) Crystallization Time Sample hours X-ray 1 DTA2 a 24 Amorphous b 34 Some Crystallinity c 44 Medium Crystallinity Exotherm 950 C.

48 Strong Medium Crystallinity Exotherm 952 C.

e 52 High Crystallinity Exotherm 955 C.

f 72 High Crystallinity 350-500 C. bands, Exotherm 970 C.

g 97 High Crystallinity Exotherm 970 C.

h 218 High Crystallinity Exotherm 985 C.

385 High Crystallinity Exotherm 1000 C.

528 High Crystallinity Exotherm 1005 C k 700 High Crystallinity Exotherm 1003 C.

Samples e through k showed the same x-ray pattern as in Table II of Example 1-b. The band intensities of samples b, c and d were 20, 50 and 70% respectively when compared to the other highly crystalline samples.

2 The 350-500 C. bands were the same as described in Example 2.

TABLE VIII X-RAY CRYSTALLINITY OF MATERIALS AIR FIRED AT 1200-13500C.

(Example 13) Residual Crystallinity, %** 1200"C. 1250 C. 13000C. 13500C.

Material 2 hours 6 hours 2 hours 5 hours 8 hours 2 hours 2 hours H3PO4 based product 109 101 86 81 39* 75 23** (autoclaved) H2 804 based product 95 96 95 73 25* 60 11* (autoclaved) Silicalite 91 81 78 58* 22* 43* 6* H3PO4 based product 89 80 74 53* 25* 38* 6* (refluxed) Silicapolymorph 86 80 49* 54* 12* 28* H2 SO4 based product 87 63 45 30* 7* 15* (refluxed) * Cristobalite present. ** Very little cristobalite present. *** All converted to cristobalite.

** Calculated based on crystallinity of material fired at 5370C. for four hours.

TABLE IX N2 SORPTION AND SURFACE AREA OF VARIOUS SILICA CONTAINING MATERIALS (EXAMPLE 14) N2 Sorption Surface Area Material Scc N2/gram M2/gm Autoclaved H3PO4 110.5 378.5 based product Autoclaved H2SO4 113.7 396.9 based product Refluxed H3PO4 119.3 421.9 based product Refluxed H2 804 96.6 330.0 based product Silicalite 97.74 330.5 Silicapolymorph 121.0 434.7 TABLE X EFFECT OF FIRING TEMPERATURE ON N2 SORPTION AND SURFACE AREA OF VARIOUS SILICA CONTAINING MATERIALS (Example 15) Surface Area, cc /gm N2 Sorption, Scc /gm 537 C/ 1300 C./ % 537 C./ 1300"C./ Material 4 hrs. 2 hrs. Residual 4 hrs. 2 hrs.Residual Autoclaved H3PO4 378.5 78.30 20.7 7 110.5 23.47 21.2 based product Autoclaved H2SO4 396.9 50.15 12.6 113.7 14.97 13.2 based product Silicalite 330.5 24.32 7.4 97.74 7.20 7.4 Refluxed H3PO4 421.9 22.10 5.2 119.3 6.47 5.4 based product TABLE XI n-PENTANE CONVERSION ACTIVITY OF AUTOCLAVED H3PO4 PRODUCT* (Example 15) Cat. Yield of n-C5 Cracked to Ratio of n-C5 Converted to Life Total C1, C2, C3, C4 Temp. cc/cc Conv.Selectivity, % % C5 C1 C2 C3 C4 C1/ C2/ C3/ C4 C. hr. % C5 i-C5 Cracked isomerised 253 21.80 5.34 12.63 87.37 0.67 4.67 - 0.015 0.25 0.40 - 1.0 16.7 26.7 263 37.75 5.27 13.17 86.83 0.69 4.58 0.005 0.01 0.27 0.40 1.0 2.0 54 80 274 39.50 6.19 19.32 80.68 1.195 4.994 0.007 0.03 0.49 0.67 1.0 4.3 70 95.7 285 40.75 6.81 23.43 76.57 1.59 5.21 0.013 0.05 0.67 0.86 1.0 3.8 51.5 66.2 305 44.50 9.74 35.34 64.66 3.44 6.30 0.07 0.21 1.49 1.67 1.0 3.0 21.3 23.9 316 46.00 11.14 38.86 61.14 4.33 6.81 0.13 0.31 1.86 2.03 1.0 2.4 14.3 15.6 316 51.85 18.72 73.19 26.81 13.70 5.02 0.74 1.28 6.16 5.52 1.0 1.7 8.3 7.5 374 59.75 43.84 89.36 10.64 39.18 4.66 1.65 3.55 19.88 14.09 1.0 2.2 12.0 8,5 * Autoclaved H3PO4 product bonded with 20% Al2O3 (1/16" pellets).

OPERATING CONDITIONS Initiation: 450 psig, 257 C. 135 cc of H2/min, 0.333 cc of n-C5/min, 1 hour.

Aging: 450 psig, 237 C. 735 cc of H2/min, 2.000 cc of n-C5/min, 3.17 hours.

Testing: 450 psig, LHSV-1.00 hr-1 H2/C5 = 2.06, Cat Vol = 20.00 cc.

TABLE XII n-PENTANE CONVERSION ACTIVITY OF AUTOCLAVED H3PO4 PRODUCT* (Example 15) Cat. Yield of n-C5 Cracked to Ratio of n-C5 Converted to Life Total C1, C2, C3, C4 Temp. cc/cc Conv. Selectivity, % % C5 C. hr. % C5 i-C5 Cracked isomerised C1 C2 C3 C4 C1/ C2/ C3/ C4 254 27.13 1.41 30.94 69.06 0.44 0.97 0.007 0.014 0.19 0.23 1.0 2.0 27.1 32.9 260 29.00 1.68 38.55 61.45 0.65 1.03 0.008 0.03 0.26 0.35 1.0 3.8 32.5 43.8 324 52.87 7.63 77.09 22.91 5.88 1.75 0.17 0.58 2.65 2.49 1.0 3.3 15.6 14.6 342 57.67 13.02 83.72 16.28 10.90 2.12 0.38 1.21 5.09 4.22 1.0 3.2 13.4 11.1 363 60.53 26.97 90.09 9.91 24.30 2.67 0.92 2.81 11.90 8.66 1.0 3.1 12.9 9.4 371 62.80 37.37 91.72 8.28 34.28 3.09 1.36 3.85 17.17 11.89 1.0 2.8 12.6 8.7 TABLE XIII METHANOL CONVERSION ACTIVITY OF AUTOCLAVED H3PO4 PRODUCT (Example 17) Temp. Cat Life Area % Composition MeOH C cc/cc hr Recovered MeOH Products Flow, cc/hr 447 6.7 32.27 67.73 20.0 429 7.33 31.99 69.01 20.0 Reaction Conditions: Pressure, atm 1 LHSV, hr1 1.25 Cat Vol, cc 15

Claims (3)

1. A silica polymorph having an X-ray powder diffraction pattern containing the d spacings set forth in Table Ill, and retaining more than 50% of its crystallinity after calcination at 1 3000C. for two hours.

2. A silica polymorph as in claim 1, which has no infrared adsorption band at 700 cm-1.

3. A silica polymorph according to claim 1 , substantially as herein described with reference to the Examples.