Solid crystalline phosphoric acid hydrocarbon conversion catalyst

Abstract: A solid crystalline phosphoric acid catalyst comprising crystallites of both silicon orthophosphate and silicon pyrophosphate and having a total X-ray intensity of at least 30 percent relative to alpha-alumina is disclosed. The solid crystalline phosphoric acid catalyst is produced by crystallizing an amorphous mixture of an acid oxide of phosphorus and a siliceous material at a temperature of from 250 to 450 o C and in the presence of from 3 to 50 mole percent water vapor based upon the total vapor rate to the crystallizing step. The catalyst is particularly useful in extending the life of a hydrocarbon conversion reaction such as olefin polymerization before catalyst replacement or regeneration becomes necessary.

Description: This invention relates to an improved solid crystalline phosphoric acid catalyst having a total silicon phosphate X-ray intensity greater than 40 percent relative to alpha-alumina and comprising crystallites of both silicon orthophosphate and silicon pyrophosphate and to a method for the production therof. The catalyst is particularly useful in the conversion of hydrocarbons. Solid phosphoric acid is a catalyst well known for its usefulness in various hydrocarbon conversion processes such as aromatic alkylation and olefin polymerization. The catalyst is composed of a support or substrate portion onto which is incorporated an acid fraction for catalytic activity. It is believed that the substrate portion is formed from the silica-phosphoric acid reaction, principally silicon orthophosphate, Si 3 (PO 4 ) 4 , silicon pyrophosphate, SiP 2 O 7 , as well as derivatives of these compounds. The catalyst is typically prepared by mixing silica with phosphoric acid followed by extrusion and calcination. The reactions are simply illustrated as follows: 3 SiO 2 + 4 H 3 PO 4 → Si 3 (PO 4 ) 4 + 6 H 2 O SiO 2 + 2 H 3 PO 4 → SiP 2 O 7 + 3 H 2 O The above reactions indicate that the phosphoric acid will react with silica to yield both types of phosphates in proportions depending upon stoichiometry and reaction conditions. The silicon orthophosphate can also be dehydrated during drying to give the silicon pyrophosphate, and this is believed to be the alternative mechanism for the silicon pyrophosphate formation. The silicon ortho- to pyrophosphate conversion also depends on factors such as temperature and hydration, as illustrated by the following equations: Si 3 (PO 4 ) 4 + 2 H 3 PO 4 → 3 SiP 2 O 7 + 3 H 2 O Si 3 (PO 4 ) 4 + heat → 2 SiP 2 O 7 + SiO 2 These reactions have made the catalyst manufacturing more complex. Low activity or low stability catalysts have resulted from prior art manufacturing procedures due to low crystallinity caused by poor crystallization conditions. It has now been found that stability of these catalysts in hydrocarbon conversion service is significantly improved by controlling this crystallinity at a relatively high level Solid phosphoric acid catalysts and methods of optimizing the physical properties such as crush strength of such catalysts are well known in the prior art. Improving stability in hydrocarbon conversion service by maximizing the total silicon phosphates crystallinity is heretofore unknown and is the subject of the present invention. U.S. Patent 2,650,201 describes a process for improving the structural strength of a calcined solid phosphoric acid catalyst by adding a hydrolyzable compound of a metal selected from a group consisting of titanium, zirconium, and tin to the composite prior to calcination of the metal containing solid phosphoric acid catalyst. The desirable calcination temperature ranges from 100° to 500°C. In distinction, the catalyst of the instant invention does not comprise any added metal component, nor does the '201 disclosure mention the benefit obtained by maximizing the silicon phosphate crystallinity. U.S. Patent 3,112,350 discloses a process for the polymerization of hydrocarbon olefins in the presence of a specific solid phosphoric acid catalyst. This specific catalyst comprises a specific high P 2 O 5 to SiO 2 mole ratio in excess of about 1.08. The catalyst is also required to be a calcined at a temperature of preferably above 560°C. The '350 disclosure teaches of the advantages of calcining the catalyst at above 560°C to achieve a specific crystallite ratio of crystalline form C to crystalline form B of about 28:1. However, when the P 2 O 5 to SiO 2 mole ratio exceeds 1.08, only materials with phosphate content higher than silicon pyrophosphate (SiP 2 O 7 , P 2 O 5 /SiO 2 = 1) are likely to be present. Silicon orthophosphate (Si 3 (PO 4 ) 4 ) is not likely to be present since it only has the P 2 O 5 /SiO 2 ratio of 0.75. Although the '350 disclosure discusses catalyst crystallinity ratio as a basis for optimizing the performance, no mention on the total crystallinity amount requirement is specified. U.S. Patent 3,673,111 discloses a process for the manufacture of a solid phosphoric acid catalyst by two-step calcination to improve the catalyst physical strength. Higher crush strength was obtained when the unfinished catalyst is exposed to steam at a temperature of from 260° to 426°C for a period of time followed by a second calcination in the absolute absence of steam. US-A-4521638 discloses a process for preparing tertiary olefins employing a solid phosphoric acid catalyst. The useful catalyst of the process is calcined at a temperature of greater than 500°C, preferably above 600°C, especially preferably above 700°C in an inert atmosphere. If the calcination temperature is lower than 500°C, a catalyst having a sufficient activity and a long life cannot be obtained (column 4, line 63 to column 5, line 2). This differs from that of the instant invention in which the high stability solid phosphoric acid catalyst was obtained by improving the total silicon phosphates crystalline content in part by calcining at temperatures lower than 450°C. US-A-3758627 discloses an olefine polymerization catalyst consisting essentially of a silica carrier and phosphoric acid, the molar ratio of P 2 O 5 to SiO 2 being between 0.6 and 0.95, and the content of crystalline C form of silicum phosphate being between 75 and 95 percent. The catalyst is produced by heating a mixture of silica with phosphoric acid at 550° to 1,000°C and then, in a second step, activating the heated catalyst with steam at 100° to 300°C. US-A-2275182 discloses a process for manufacturing polymerization catalysts by mixing a phosphoric acid with a siliceous material, calcining the mixture at a temperature of at least 600°F (316°C), steaming the mixture at a temperature not substantially above 600°F (316°C) and treating the steamed mixture with dry inert gas at 400° to 600°F (204° to 316°C). It is apparent that a variety of mutually inconsistent treatment conditions, has been employed in the production of solid phosphoric acid catalysts. The object of this invention is to provide novel catalysts particularly having improved stability, to establish the factors controlling such stability, and to establish a means of producing such catalysts. It has been discovered that improved catalyst stability in the catalytic condensation reaction is achieved by maximizing the total and type of crystalline content in a solid phosphoric acid catalyst. Furthermore, the higher silicon phosphate crystallinity product is obtained in a controlled manner by closely controlling steam levels and temperatures during the crystallization step. A principal objective of this invention is to provide an improved solid phosphoric acid catalyst. The improved catalyst exhibits enhanced catalyst life due to improved catalyst crystallinity and crystallinity distribution. The present invention provides a solid crystalline phosphoric acid catalyst having a total silicon phosphate X-ray intensity greater than 40 percent relative to alpha-alumina, said X-ray intensity being calculated by integrating the (002) peak of silicon pyrophosphate and the (113) peak of silicon orthophosphate, and dividing by the integrated (012), (104) and (113) peaks of an alpha alumina external standard, said catalyst comprising crystallites of both silicon orthophosphate and silicon pyrophosphate, the silicon pyrophosphate crystallites exhibiting at least 1.0 percent X-ray intensity, and the silicon orthophosphate crystallites exhibiting at least 30 percent X-ray intensity, both relative to alpha-alumina, said catalyst being obtainable by crystallizing an amorphous mixture of an acid oxide of pentavalent phosphorus and a siliceous material providing a weight ratio of phosphorus pentoxide to siliceous material from 1.8:1 to 6:1, in a crystallizing step comprising contacting the mixture with a steam-containing atmosphere at elevated temperature, the crystallizing step being operated in one or more crystallization zones, said crystallization zone, or at least the final crystallization zone, being operated at a temperature of from 392°C to 450°C, and at a steam concentration of from 5 to 30 mole percent, based upon the total vapor in the crystallizing step, for a total period of time ranging from 20 to 120 minutes or more, until a desired catalyst is produced. The present invention provides a method for the production of a solid crystalline phosphoric acid catalyst by crystallizing an amorphous mixture of an acid oxide of pentavalent phosphorus and a siliceous material providing a weight ratio of phosphorus pentoxide to siliceous material from 1.8:1 to 6:1, in a crystallizing step comprising contacting the mixture with a steam-containing atmosphere at elevated temperature. According to the invention, the crystallizing step is operated in one or more crystallization zones, said crystallization zone, or at least the final crystallization zone, being operated at a temperature of from 392° to 450°C, and at a steam concentration of from 5 to 30 mole percent, based upon the total vapor in the crystallizing step, for a total period of time ranging from 20 to 120 minutes or more, until a desired catalyst is produced having a total silicon phosphate X-ray intensity greater than 40 percent relative to alpha-alumina, said X-ray intensity being calculated by integrating the (002) peak of silicon pyrophosphate and the (113) peak of silicon orthophosphate, and dividing by the integrated (012), (104) and (113) peaks of an alpha alumina external standard, said catalyst comprising crystallites of both silicon orthophosphate and silicon pyrophosphate, the silicon pyrophosphate crystallites exhibiting at least 1.0 percent X-ray intensity, and the silicon orthophosphate crystallites exhibiting at least 30 percent X-ray intensity, both relative to alpha-alumina. The invention also provides a process for the conversion of hydrocarbons comprising contacting a hydrocarbon feedstock with the solid crystalline phosphoric acid obtainable by a method as defined above. The figure is a graphical representation of the catalyst properties in gallons of hydrocarbon processed per pound of solid phosphoric (conversion fraction equals 8.34 x 10 -3 m 3 /kg per gal/lb) acid catalyst in relation to total crystallinity of the catalyst. The propylene condensation reaction was used for obtaining this catalyst life data. Solid phosphoric acid catalysts are well known for their utility in various important hydrocarbon conversion processes. However, there have always been problems associated with the use of solid phosphoric acid catalyst in such processes including catalyst activity, catalyst dissolution, catalyst strength, catalyst life, and the like. Therefore, ways to produce active, strong catalysts are always being pursued. To approach this goal, a method for the production of a long life catalyst formulation has now been discovered. The essential and active ingredient of the solid catalyst herein contemplated is an acid of phosphorus, in which the phosphorus has a valence of +5. The acid may constitute from 60 to 80 wt.% or more of the catalyst mixture ultimately produced, and is preferred to be over 80 wt.% thereof. Of the various acids of phosphorus, orthophosphoric acid (H 3 PO 4 ) and pyrophosphoric acid (H 4 P 2 O 7 ) find general application in the primary mixture, due mainly to their cheapness and to the readiness with which they may be procured, although this invention is not restricted to their use but may employ any of the other acids of pentavalent phosphorus insofar as they are adaptable. It is not intended to imply, however, that the different acids of phosphorus, which may be employed will produce catalysts which have identical effects upon any given organic reactions as each of the catalysts produced from different acids and by slightly varied procedure will exert its own characteristic action. However, it is believed that the catalyst produced having the crystallizing properties disclosed herein will have superior hydrocarbon conversion properties in comparison to catalysts using similar precursors but different manufacturing methods. In using orthophosphoric acid as a primary ingredient, different concentrations of the aqueous solution may be employed from approximately 75 to 100 percent or acid containing some free phosphorus pentoxide may even be used. By this is meant that the ortho acid may contain a definite percentage of the pyro acid corresponding to the primary phase of dehydration of the orthophosphoric acid. Within these concentration ranges, the acids will be liquids of varying viscosities and will readily mix with adsorbent materials. In practice, it has been found that pyrophosphoric acid corresponding to the formula H 4 P 2 O 7 can be incorporated with siliceous materials at temperatures somewhat above its melting point (61°C) and that the period of heating which is given to the pyro acid adsorbent mixtures may be different from that used when the ortho acid is so employed. Triphosphoric acid which may be represented by the formula H 5 P 3 O 10 may also be used as a starting material for preparation of the catalyst of this invention. These catalytic compositions may also be prepared from the siliceous materials mentioned herein and phosphoric acid mixtures containing orthophosphoric, pyrophosphoric, triphosphoric, and other polyphosphoric acids. The materials which may be employed as adsorbents or carriers for oxygen acids of phosphorus are divided into two classes. The first comprises materials of predominantly siliceous character and includes diatomaceous earth, kieselguhr, and artificially prepared porous silica. The second class of materials which may be employed either alone or in conjunction with the first class comprises generally certain members of the class of alumina silicates and includes such naturally occurring substances as various fullers earth and clays such as bentonite, montmorillonite, acid treated clays, and the like. In producing the catalyst composites which are utilized in the present invention, an oxygen acid of phosphorus and a solid siliceous material are mixed at a temperature of from 10° to 232°C and preferably at a temperature of from 95° to 180°C to form a composite. Thus, satisfactory results have been obtained by heating polyphosphoric acid (82% P 2 O 5 content) at a temperature of about 170°C and then mixing this hot acid with diatomaceous earth. The polyphosphoric acid and diatomaceous earth form a composite in which the weight ratio of phosphorus pentoxide to diatomaceous adsorbent is from 1.8:1 to 6:1. This composite is slightly moist to almost dry in appearance but becomes plastic when subjected to pressure in a hydraulic press-type or auger-type extruder by which the composite is formed into pieces that are cut into shaped particles. This amorphous extrudate is then crystallized to produce the final catalyst with desired properties. The crystallization of the amorphous extrudate may be accomplished in any known crystallizing step known in the art in which temperature, steam rate, and time in the crystallizing apparatus may be controlled. Conditions of temperature, steam addition rate, and time in the crystallization apparatus all directly impact on the final type and amount of crystallites in the finished solid phosphoric acid catalysts. As mentioned, it is essential that the finished solid phosphoric acid catalyst have a total silicon phosphate X-ray intensity of at least 40 percent relative to an alpha-alumina standard, and comprise crystallites of both silicon orthophosphates and silicon pyrophosphates. The term "crystallization" means apparatus or process as used in the instant application and refers to any type of apparatus in which one may control temperature, steam rate, and time in the apparatus in order to optimize the desired crystallinity properties of the solid phosphoric acid catalyst of this invention. Specifically, such crystallizing apparatus will be an oven or furnace. Typical of such apparatuses known in the art are muffle ovens or furnaces, kilns, and batch or continuous calciners. The crystallization can obviously be accomplished in a batch or continuous manner. Such a crystallizing means may contain one or more zones where temperature, time, and steam level can be controlled. Temperature is the first critical crystallization condition. Temperature is important in both dehydrating the amorphous material and in controlling the type of crystallites produced as a result of the crystallizing procedures. It is well known that high temperatures, especially those above 500°C result in a solid phosphoric acid catalyst comprising essentially only crystallites of silicon pyrophosphate. As a result of desiring a catalyst with crystallites of both silicon orthophosphate and silicon pyrophosphate, it was determined that crystallization temperatures ranging from 392 to 450°C were most desirable (and so are used according to the invention). In conjunction with a specific crystallizing temperature, it is also an important aspect of this invention that the steam, or moisture content of the crystallizing step be controlled closely to result in the desired crystallinity properties of the catalyst. The steam content of the vapor of the crystallization step is from 5 to 30 mole percent based on the total vapor rate to the crystallization zone. It should be noted that controlling the steam content of the crystallization zone vapors does not necessarily mean that all or even part of the steam to the crystallization zone must be added from an outside source. It is quite possible that much of the steam will be present in the vapor in the crystallization zone as a result of evaporation of water from the catalyst during the crystallization. Steam addition to the crystallization zone or zones will likely be required but the variable might also be controlled by controlling such variables as total vapor rate through the crystallization zone or zones, temperature, and green catalyst moisture content among others. Time in the crystallization step is also important. The total crystallization time will vary from 20 to 120 minutes or more. When more than one crystallization zone is used, the total time in each may vary such that the total crystallization time ranges from 20 to 120 minutes. It is a further preferred aspect of this invention that where there is more than one crystallization zone, at least the terminal or final crystallization zone in a multiple step crystallization process is operated at the desired process conditions detailed above. Keeping in mind that the desired temperature range will typically be the highest crystallization temperature the catalyst will see, it becomes reasonable to operate the terminal crystallization zone at the temperature and steam conditions that will optimize the catalyst total crystallinity and crystallite type. This is not to say that other crystallization zones besides the terminal zone cannot be operated at the preferred operating conditions. It is believed that this is the most efficient way of producing the catalyst disclosed herein. A solid phosphoric acid catalyst produced by the method above will have a total silicon phosphate X-ray intensity greater than 40 percent relative to an alpha-alumina standard. The catalyst also will comprise silicon pyrophosphate crystallites with at least 1 percent X-ray intensity relative to alpha-alumina and silicon orthophosphate crystallites with at least 30 percent X-ray intensity relative to alpha-alumina. The crystallinity type and total crystallinity of the finished solid phosphoric acid catalyst is determined by X-ray diffraction using a National Bureau of Standards alpha-alumina reference material. This analysis provides relative values of silicon orthophosphate and silicon pyrophosphate both with respect to alpha-alumina not relative to each other and not absolute values of crystallinity. To determine the relative crystallinity of a finished solid phosphoric acid catalyst sample, the sample is first ground to fine powder (particle size less than 44 µm). The sample is then inserted into an X-ray diffractometer equipped with preferably copper anode X-ray tube and a quantitative diffraction scan is acquired. Raw integrated intensities of silicon phosphate phases are acquired by integrating the (002) peak of silicon pyrophosphate and (113) peak of silicon orthophosphate. Also obtained is the raw integrated intensity of an alpha-alumina external standard by integrating the (012), (104), and (113) peaks. Relative X-ray intensities of silicon phosphate phases are obtained by dividing their respective raw integrated intensities by the sum of raw integrated intensities of three peaks of an alpha-alumina external standard. The result is multiplied by 100 and expressed in percent units. The X-ray diffraction results reported herein are expressed in values such as total relative crystallinity, silicon orthophosphate crystallinity and silicon pyrophosphate crystallinity, and finally in terms of a relative intensity ratio. Total relative crystallinity is synonymous to total crystallinity. The total crystallinity of the solid phosphoric acid catalyst is the sum of the silicon orthophosphate crystallinity relative to alpha-alumina, and silicon pyrophosphate crystallinity relative to alpha-alumina. The relative intensity ratio refers to the ratio of the silicon orthophosphate crystallinity relative to alpha-alumina divided by the silicon pyrophosphate crystallinity relative to alpha-alumina. The catalyst of this invention is useful in catalytic condensation, aromatic alkylation, and other types of hydrocarbon conversion processes. When employed in the conversion of olefinic hydrocarbons into polymers, the catalyst formed as heretofore set forth is preferably employed as a granular layer in a heated reactor which is generally made from steel and through which the preheated hydrocarbon fraction is directed. Thus, the solid catalyst of this process may be employed for treating mixtures of olefin-containing hydrocarbon vapors to effect olefin polymerization, but the same catalyst may also be used at operating conditions suitable for maintaining liquid phase operation during polymerization of olefinic hydrocarbons, such as butylenes, to produce gasoline fractions. When employed in the polymerization of normally gaseous olefins, the formed catalyst particles are generally placed in a vertical, cylindrical treating tower and the olefin-containing gas mixture is passed downwardly therethrough at a temperature of from 140° to 290°C and at a pressure of from 0.7 to 10.3 MPa (6.8 to 102 atmospheres). These conditions are particularly applicable when dealing with olefin-containing material which may contain from approximately 10 to 50 percent or more of propylene and butylenes. When operating on a mixture comprising essentially propylene and butylenes, this catalyst is effective at temperatures from 140° to 250°C and at a pressure of from 3.4 to 10.3 MPa (34 to 102 atmospheres). When employed in the alkylation of aromatic hydrocarbons, the catalyst of this invention may be located in tubular reactors or single, fixed beds of catalyst. Temperatures which are suitable for the alkylation of aromatics with the instant catalyst are those temperatures which initiate a reaction between an aromatic substrate and the particular olefin used to selectively produce the desired monoalkylaromatic compound. Generally, temperatures suitable for use are from 100° to 390°C, especially from 150° to 275°C. Pressures which are suitable for use herein preferably are above 0.1 MPa (1 atmosphere) but should not be in excess of 13.2 MPa (130 atmospheres). An especially desirable pressure range is from 1 to 4 MPa (10 to 40 atmospheres) with a liquid hourly space velocity (LHSV) based upon the aromatic feed rate of from 0.1 to 50 h -1 , and especially from 0.5 to 5 h -1 . It should be noted that the temperature and pressure combination used herein is to be such that the alkylation reaction takes place in essentially the liquid phase. In an essentially liquid phase process for producing alkylaromatics, the catalyst is continuously washed with reactants, thus preventing buildup of coke precursors on the catalyst. This results in reduced amounts of carbon forming on said catalyst in which case, catalyst cycle life is extended as compared to a gas phase alkylation process in which coke formation and catalyst deactivation is a major problem. By "essentially liquid phase", it is meant that all of the active reactants are in the liquid phase, however, there may be inert compounds that exist in the vapor phase such as light paraffins. During use of this catalyst in hydrocarbon conversion processes, it is often of value to add small amounts of moisture to prevent excessive dehydration and subsequent decrease in catalyst activity and in order to substantially prevent loss of water from the catalyst. An amount of water or water vapor such as steam is added to the charged hydrocarbon so as to substantially balance the water content of the catalyst. This amount of water vapor varies from 0.1 to 6.0 percent by volume of the organic material charged. The following examples are presented in illustration of the method of this invention. EXAMPLE I This example illustrates the general preparation method for the amorphous form phosphoric acid catalyst extrudate that is converted by various crystallization methods of the subsequent examples into crystalline forms of solid phosphoric acid catalyst. Kieselguhr clay, and phosphoric acid having a P 2 O 5 content of 82 percent or greater, were combined at a weight ratio of 1 to 2 at a temperature of 170°C. This material was extruded with an extruder through a die to produce extrudates approximately 5 mm diameter. Only amorphous character was detected by X-ray with the green extrudates. The extrudates thus produced were then used in the crystallization experiments described in the following Examples II to VIII. The crystallinity of the finished catalysts was determined by X-ray diffraction. The method employed used standard X-ray diffraction techniques using NBS alpha-alumina as a reference material (see the specifications for the exact test method). Therefore, the crystallinity values of orthophosphate and pyrophosphate reported in the following examples are not absolute crystallinity values but are instead relative to alpha-alumina. EXAMPLE II A batch of amorphous solid phosphoric acid green extrudates from Example I was subjected to a crystallization process in a small oven in batches of 100 to 150 grams. The oven contained a means of allowing once through air and steam to be added at a controled rate as well as a means for closely controlling the oven temperature. After about 20 minutes under 3 percent steam level at an oven temperature of 250°C, the catalyst was removed and analyzed for its crystallinity. Only crystalline silicon orthophosphate was detected with an X-ray intensity of 10.7 percent relative to an alpha-alumina standard. No crystalline silicon pyrophosphates were detected. EXAMPLE III A batch of amorphous solid phosphoric acid green extrudates from Example I was subjected to a crystallization process in the same small oven as in Example II. After about 20 minutes under 22 percent steam level at 250°C oven temperature, the catalyst was removed and analyzed for its crystallinity. Only crystalline form of silicon orthophosphate was detected with a relative X-ray intensity of 6.4 percent relative to an alpha-alumina standard. The results of this example and the results of Example II indicate that steam has no effect on the production of crystalline silicon pyrophosphates at temperatures below 250°C. EXAMPLE IV A batch of amorphous solid phosphoric acid green extrudates from Example I was subjected to a crystallization process in the same small oven as in Example II. After about 50 minutes under 3 percent steam level at 392°C oven temperature, the catalyst was removed and analyzed for its crystallinity. Only crystalline form of silicon orthophosphate was detected with a relative X-ray intensity of 44.9 percent relative to an alpha-alumina standard. EXAMPLE V A portion of the crystalline solid phosphoric acid catalyst from Example IV was subjected to a reconditioning process in the same small oven as in Example II for an additional 20 minutes at 392°C under 26 percent steam. This additional treatment reduced the total silicon phosphate X-ray intensity to 41.7 percent relative to the alpha-alumina standard with the relative intensity ratio between silicon orthophosphate and silicon pyrophosphate of 7.1:1. This example shows that both steam and a temperature are critical factors in producing a solid phosphoric acid catalyst having crystallites of both ortho and pyrophosphates EXAMPLE VI A batch of amorphous solid phosphoric acid green extrudates from Example I was subjected to a crystallization process in the same small oven as in Example II. After about 50 minutes in an 18 percent steam atmosphere at 392°C oven temperature, the catalyst was removed and analyzed for its crystallinity. Crystallites of both silicon orthophosphate and silicon pyrophosphate were detected with a total X-ray intensity of 40 percent relative to an alpha-alumina standard. The relative intensity ratio between the silicon orthophosphate and silicon pyrophosphate was 17.2:1. EXAMPLE VII A portion of the crystalline solid phosphoric acid catalyst from Example VI was subjected to a reconditioning process in the same small oven as in Example II for an additional 20 minutes at 392°C in a 3 percent steam atmosphere. This additional treatment reduced the total silicon phosphate X-ray intensity to 38.0 percent relative to the alpha-alumina standard while the relative intensity ratio between silicon orthophosphate and silicon pyrophosphate dropped to 12.7:1 EXAMPLE VIII A batch of amorphous solid phosphoric acid green extrudates from Example I was subjected to a crystallization process in the same small oven as in Example II. After about 70 minutes in a 27 percent steam atmosphere at 430°C oven temperature, the catalyst was removed and analyzed for its crystallinity. Crystalline form of both silicon orthophosphate and silicon pyrophosphate were detected with a total X-ray intensity of 47.7 percent relative to an alpha-alumina standard. The relative intensity ratio between the silicon orthophosphate and silicon pyrophosphate was 12.3:1. EXAMPLE IX A number of solid phosphoric acid catalysts prepared essentially as set forth in Example I and finished at various calcination conditions were analyzed for relative silicon orthophosphate and silicon pyrophosphate X-ray intensity. The results of this analysis can be found in Table 1 below. The analyzed catalysts were then tested for catalyst life by placing the catalysts in an olefin polymerization process plant. The testing was conducted at a pressure of about 6.9 MPa (68 atmospheres), with propylene feed, at a liquid hourly space velocity of from 1.8-2.1 h -1 , and at a temperature of from 149° to 230°C. The testing occurred in a plant operated at constant conversion directed toward making a commercial product. Solid Phosphoric Acid Catalyst Test Results Catalyst Relative Total X-ray Intensity Silicon Orthophosphate to Silicon Pyrophosphate Relative Intensity Ratio Relative Catalyst Life 1 37.4 10.1 1.00 2 38.5 19.0 1.47 3 40.1 31.9 1.21 4 41.4 10.3 1.76 5 42.2 11.5 1.59 6 41.4 16.3 1.65 7 44.5 152.4 1.62 8 44.5 9.2 1.68 9 45.5 83.3 1.91 10 45.0 3.5 1.97 11 45.4 18.2 1.97 12 45.2 2.7 2.00 13 46.8 5.9 1.94 14 46.9 60.6 2.09 15 45.7 40.2 2.21 A comparison of the total crystallinity values of Table 1, that is the Relative Total X-ray Intensity Values, to the catalyst life values demonstrates that total crystallinity is directly related to catalyst stability. The greater the total silicon phosphate relative X-ray intensity of the solid phosphoric acid catalyst, the more stable the solid phosphoric acid catalyst will be during the olefin polymerization processes as measured by the catalyst life.

Claims: A solid crystalline phosphoric acid catalyst having a total silicon phosphate X-ray intensity greater than 40 percent relative to alpha-alumina, said X-ray intensity being calculated by integrating the (002) peak of silicon pyrophosphate and the (113) peak of silicon orthophosphate, and dividing by the integrated (012), (104) and (113) peaks of an alpha alumina external standard, said catalyst comprising crystallites of both silicon orthophosphate and silicon pyrophosphate, the silicon pyrophosphate crystallites exhibiting at least 1.0 percent X-ray intensity, and the silicon orthophosphate crystallites exhibiting at least 30 percent X-ray intensity, both relative to alpha-alumina, said catalyst being obtainable by crystallizing an amorphous mixture of an acid oxide of pentavalent phosphorus and a siliceous material providing a weight ratio of phosphorus pentoxide to siliceous material from 1.8:1 to 6:1, in a crystallizing step comprising contacting the mixture with a steam-containing atmosphere at elevated temperature, the crystallizing step being operated in one or more crystallization zones, said crystallization zone, or at least the final crystallization zone, being operated at a temperature of from 392°C to 450°C, and at a steam concentration of from 5 to 30 mole percent, based upon the total vapor in the crystallizing step, for a total period of time ranging from 20 to 120 minutes or more, until a desired catalyst is produced. A method for the production of a solid crystalline phosphoric acid catalyst according to Claim 1 by crystallizing an amorphous mixture of an acid oxide of pentavalent phosphorus and a siliceous material providing a weight ratio of phosphorus pentoxide to siliceous material from 1.8:1 to 6:1, in a crystallizing step comprising contacting the mixture with a steam-containing atmosphere at elevated temperature, characterized in that the crystallizing step is operated in one or more crystallization zones, said crystallization zone, or at least the final crystallization zone, being operated at a temperature of from 392°C to 450°C, and at a steam concentration of from 5 to 30 mole percent, based upon the total vapor in the crystallizing step, for a total period of time ranging from 20 to 120 minutes or more, until a desired catalyst is produced having a total silicon phosphate X-ray intensity greater than 40 percent relative to alpha-alumina, said X-ray intensity being calculated by integrating the (002) peak of silicon pyrophosphate and the (113) peak of silicon orthophosphate, and dividing by the integrated (012), (104) and (113) peaks of an alpha alumina external standard, said catalyst comprising crystallites of both silicon orthophosphate and silicon pyrophosphate, the silicon pyrophosphate crystallites exhibiting at least 1.0 percent X-ray intensity, and the silicon orthophosphate crystallites exhibiting at least 30 percent X-ray intensity, both relative to alpha-alumina. A method according to Claim 2 chacterized in that the siliceous material component of the solid phosphoric acid catalyst is kieselguhr' clay, diatomaceous earth, or artificially prepared porous silica. A method according to Claim 2 or 3, characterized in that the acid oxide of phosphorus is a polyphosphoric acid. A process for the conversion of hydrocarbons comprising contacting a hydrocarbon feedstock with the solid crystalline phosphoric acid catalyst obtainable by a method according to any one of Claims 2 to 4. A process according to Claim 5 characterized in that the process for the conversion of hydrocarbons is the alkylation of an aromatic hydrocarbon with an olefin-acting agent. A process according to Claim 6 characterized in that the alkylation of an aromatic hydrocarbon with an aliphatic hydrocarbon occurs at a temperature from 100° to 390°C, a pressure from 0.1 to 13.2 MPa (1 to 30 atmospheres) and a liquid hourly space velocity from 0.5 to 50 h -1 . A process according to claim 5 characterized in that the process for the conversion of hydrocarbons is catalytic condensation. A process according to Claim 8 characterized in that the catalytic condensation process occurs at a temperature of from 170° t 290°C and a pressure of from 0.7 to 10.3 MPa (6.8 to 102 atmopheres).

Inventors: CHAO TAI-HSIANG, FORD MARK R, RINGWELSKI ANDRZEJ Z, WILCHER FIONA, CHAO, TAI-HSIANG, FORD, MARK R., RINGWELSKI, ANDRZEJ Z., WILCHER, FIONA, WILCHER, FIONA PLACE
Applicants: UOP INC, UOP
Application year: 1990
Main classification: B01J27
IPC codes: B01J29, C07C2, C07C11, B01J37, C07C15, C10G45, B01J27