text: an essential feature of the process of the instant invention is an elapo molecular sieve . elapos are molecular sieves which have a three - dimensional microporous framework structure of alo 2 , po 2 and elo 2 tetrahedral units . generally the elapos have the empirical formula where el is a metal selected from the group consisting of silicon , magnesium , zinc , iron , cobalt , nickel , manganese , chromium and mixtures thereof , &# 34 ; x &# 34 ; is the mole fraction of el and has a value of at least 0 . 005 , &# 34 ; y &# 34 ; is the mole fraction of al and has a value of at least 0 . 01 , &# 34 ; z &# 34 ; is the mole fraction of p and has a value of at least 0 . 01 and x + y + z = 1 . when el is a mixture of metals , &# 34 ; x &# 34 ; represents the total amount of the metal mixture present . preferred metals ( el ) are silicon , magnesium and cobalt with silicon being especially preferred . the preparation of various elapos are well known in the art and may be found in u . s . pat . no . 4 , 554 , 143 ( feapo ); u . s . pat . no . 4 , 440 , 871 ( sapo ); u . s . pat . no . 4 , 853 , 197 ( mapo , mnapo , znapo , coapo ); u . s . pat . no . 4 , 793 , 984 ( capo ), u . s . pat . no . 4 , 752 , 651 and u . s . pat . no . 4 , 310 , 440 , all of which are incorporated by reference . generally , the elapo molecular sieves are synthesized by hydrothermal crystallization from a reaction mixture containing reactive sources of el , aluminum , phosphorus and a templating agent . reactive sources of el are the metal salts such as the chloride and nitrate salts . when el is silicon a preferred source is fumed , colloidal or precipitated silica . preferred reactive sources of aluminum and phosphorus are pseudo - boehmite alumina and phosphoric acid . preferred templating agents are amines and quaternary ammonium compounds . an especially preferred templating agent is tetraethylammonium hydroxide ( teaoh ). the reaction mixture is placed in a sealed pressure vessel , optionally lined with an inert plastic material such as polytetrafluoroethylene and heated preferably under autogenous pressure at a temperature between about 50 ° c . and 250 ° c . and preferably between about 100 ° c . and 200 ° c . for a time sufficient to produce crystals of the elapo molecular sieve . typically the time varies from about 1 hour to about 120 hours and preferably from about 24 hours to about 48 hours . the desired product is recovered by any convenient method such as centrifugation or filtration . by using the above procedure , one obtains an elapo molecular sieve which has a crystal morphology in which the average smallest crystal dimension is at least 0 . 1 micron and preferably at least 0 . 2 micron . with respect to the shape of the crystallite , they can have any shape including plate , platelet , cubic , spherical etc . as long as the average smallest dimension is at least 0 . 1 micron . as is shown in the examples , the average smallest crystal dimension is determined by examining the elapo molecular sieve using scanning electron microscopy ( sem ) and measuring the crystals in order to obtain an average value for the smallest dimension . without wishing to be bound by any one particular theory , it appears that a minimum thickness is required so that the diffusion path for the desorption of ethylene and propylene is sufficiently long to allow differentiation of the two molecules . since ethylene is a more valuable product , by controlling the crystal dimensions one can maximize the formation of ethylene . as will be shown in the examples , when the smallest dimension is less than 0 . 1 , the ratio of ethylene to propylene ( c 2 = / c 3 = ) is about 1 . 2 , whereas when the smallest dimension is greater than 0 . 1 microns , the ratio of c 2 = / c 3 = is about 1 . 4 . this provides a greater production of ethylene . the elapos which are synthesized using the process described above will usually contain some of the organic templating agent in its pores . in order for the elapos to be active catalysts , the templating agent in the pores must be removed by heating the elapo powder in an oxygen containing atmosphere at a temperature of about 200 ° to about 700 ° c . until the template is removed , usually a few hours . a preferred embodiment of the invention is one in which the metal ( el ) content varies from about 0 . 005 to about 0 . 05 mole fraction . if el is more than one metal then the total concentration of all the metals is between about 0 . 005 and 0 . 05 mole fraction . an especially preferred embodiment is one in which el is silicon ( usually referred to as sapo ). the sapos which can be used in the instant invention are any of those described in u . s . pat . no . 4 , 440 , 871 . of the specific crystallographic structures described in the &# 39 ; 871 patent , the sapo - 34 , i . e ., structure type 34 , is preferred . the sapo - 34 structure is characterized in that it adsorbs zenon but does not adsorb isobutane , indicating that it has a pore opening of about 4 . 2 å . the elapo molecular sieve of this invention may be used alone or they may be mixed with a binder and formed into shapes such as extrudates , pills , spheres , etc . any inorganic oxide well known in the art may be used as a binder . examples of the binders which can be used include alumina , silica , aluminum - phosphate , silica - alumina , etc . when a binder is used , the amount of elapo which is contained in the final product ranges from 10 to 90 weight percent and preferably from 30 to 70 weight percent . the conversion of methanol to light olefins is effected by contacting the methanol with the elapo catalyst at conversion conditions , thereby forming the desired light olefins . the methanol can be in the liquid or vapor phase with the vapor phase being preferred . contacting the methanol with the elapo catalyst can be done in a continuous mode or a batch mode with a continuous mode being preferred . the amount of time that the methanol is in contact with the elapo catalyst must be sufficient to convert the methanol to the desired light olefin products . when the process is carried out in a batch process , the contact time varies from about 0 . 001 hr . to about 1 hr . and preferably from about 0 . 01 hr . to about 1 . 0 hr . the longer contact times are used at lower temperatures while shorter times are used at higher temperatures . further , when the process is carried out in a continuous mode , the weight hourly space velocity ( whsv ) based on methanol can vary from about 1 hr - 1 to about 1000 hr - 1 and preferably from about 1 hr - 1 to about 100 hr - 1 . generally , the process must be carried out at elevated temperatures in order to form light olefins at a fast enough rate . thus , the process should be carried out at a temperature of about 300 ° c . to about 600 ° c ., preferably from about 400 ° c . to about 550 ° c . and most preferably from about 450 ° c . to about 525 ° c . the process may be carried out over a wide range of pressure including autogenous pressure . thus , the pressure can vary from about 0 kpa ( 0 psig ) to about 1724 kpa ( 250 psig ) and preferably from about 34 kpa ( 5 psig ) to about 345 kpa ( 50 psig ). optionally , the methanol feedstock may be diluted with an inert diluent in order to more efficiently convert the methanol to olefins . examples of the diluents which may be used are helium , argon , nitrogen , carbon monoxide , carbon dioxide , hydrogen , steam , paraffinic hydrocarbons , e . g ., methane , aromatic hydrocarbons , e . g ., benzene , toluene and mixtures thereof . the amount of diluent used can vary considerably and is usually from about 5 to about 90 mole percent of the feedstock and preferably from about 25 to about 75 mole percent . the actual configuration of the reaction zone may be any well known catalyst reaction apparatus known in the art . thus , a single reaction zone or a number of zones arranged in series or parallel may be used . in such reaction zones the methanol feedstock is flowed through a bed containing the elapo catalyst . when multiple reaction zones are used , one or more elapo catalyst may be used in series to produce the desired product mixture . instead of a fixed bed , a dynamic bed system , e . g ., fluidized or moving , may be used . such a dynamic system would facilitate any regeneration of the elapo catalyst that may be required . if regeneration is required , the elapo catalyst can be continuously introduced as a moving bed to a regeneration zone where it can be regenerated by means such as oxidation in an oxygen containing atmosphere to remove carbonaceous materials . the following examples are presented in illustration of this invention and are not intended as undue limitations on the generally broad scope of the invention as set out in the appended claims a series of molecular sieves ( sapos ) were prepared by the following procedure . in a container orthophosphoric acid ( 85 %) was combined with water . to this there was added a silica sol and a 35 wt . % aqueous solution of tetraethylammonium hydroxide ( teaoh ). finally , alumina in the form of pseudoboehmite along with water and sapo - 34 seed material were added and blended in . the resulting mixtures had compositions in molar oxide ratios as set forth in table 1 below . table 1______________________________________reaction mixture compositions for sapos reactionsample i . d . time teach sio . sub . 2 al . sub . 2 o . sub . 3 p . sub . 2 o . sub . 5 h . sub . 2 o______________________________________a 48 1 . 0 0 . 10 1 . 0 1 . 0 35b 48 1 . 0 0 . 10 1 . 0 1 . 0 35c 48 1 . 0 0 . 10 1 . 0 1 . 0 45d 24 1 . 0 0 . 10 1 . 0 1 . 0 45e 36 1 . 0 0 . 15 1 . 0 1 . 0 40f 48 1 . 0 0 . 20 1 . 0 1 . 0 45______________________________________ the mixture was now placed in a steel pressure reactor equipped with a turbine stirrer . the mixture was now stirred and heated to 100 ° c . over a 6 hour period , held at 100 ° c . for 6 hours , then heated to 175 ° c . over a period of 3 hours and held there for the reaction time of 24 , 36 or 48 hours . finally , the reaction mixture was cooled to ambient temperature and the solid product recovered by centrifugation and washed with water . all the products were analyzed and found to be sapo - 34 molecular sieves . the catalysts prepared in example 1 were evaluated for the conversion of methanol to light olefins in a fixed bed pilot plant . a 4 gram sample in the form of 20 - 40 mesh agglomerates was used for the testing . before testing , each sample was calcined in air in a muffle oven at 650 ° c . for 2 hours and then pretreated in situ by heating to 400 ° c . for 1 hour under nitrogen . the pretreated sample was now contacted with a feed consisting of methanol and h 2 o in a 1 / 0 . 44 molar ratio at 435 ° c ., 5 psig and 2 . 5 hr - 1 meoh whsv . the composition of the effluent was measured by an on - line gc after 30 minutes on stream to determine initial conversion and selectivities . complete conversion was obtained initially with all catalysts but it fell with time on stream as the catalysts deactivated . table 2 presents the selectivity to ethylene and propylene and the ethylene / propylene product ratio at the point where conversion was 99 % for each catalyst . table 2______________________________________effect of crystal dimension on ethylene / propylene production average smallest c . sub . 2 . sup .= + c . sub . 3 . sup .= catalyst i . d . dimension ( microns ) selectivity (%) c . sub . 2 . sup .= / c . sub . 3 . sup .= ______________________________________a 0 . 07 82 . 4 1 . 17b 0 . 08 79 . 2 1 . 18c 0 . 09 82 . 2 1 . 25d 0 . 13 80 . 8 1 . 40e 0 . 17 81 . 2 1 . 41f 0 . 58 78 . 7 1 . 48______________________________________ the average smallest crystallite dimension was determined by measuring 20 representative crystallites in one or more micrographs obtained using a scanning electron microscope at 30 , 000 × magnification . the data indicate that when the smallest crystal dimension is less than 0 . 1 micron , the ratio of c 2 = to c 3 = is lower , i . e ., propylene production is greater .