A new family of high charge density crystalline microporous silicometallophosphate designated SAPO-79 has been synthesized. These silicometallophosphate are represented by the empirical formula of:

R.sup.p+.sub.rM.sub.m.sup.+E.sub.xPSi.sub.yO.sub.z

where M is an alkali metal such as potassium, R is an organoammonium cation such as diethyldimethylammonium and E is a trivalent framework element such as aluminum or gallium. The SAPO-79 family of materials represent the first alkali-stabilized phosphate-based molecular sieves to have the ERI topology and have catalytic properties for carrying out various hydrocarbon conversion processes and separation properties for separating at least one component.

A new family of crystalline microporous high charge density silicometallophosphates has been synthesized. These silicometallophosphate are represented by the empirical formula of:

R.sup.p+.sub.rM.sub.m.sup.+E.sub.xPSi.sub.yO.sub.z

where M is an alkali metal such as potassium, R is any quaternary ammonium cation such as ethyltrimethylammonium and E is a trivalent framework element such as aluminum or gallium. This family of high charge density silicometallophosphate molecular sieves has catalytic properties for carrying out various hydrocarbon conversion processes and separation properties for separating at least one component.

A process for preparing acrylic acid, comprising (i) providing a stream S4 comprising a formaldehyde source and acetic acid; (ii) contacting stream S4 with an aldol condensation catalyst comprising a zeolitic material comprising aluminum in the framework structure to obtain a stream S6 comprising acrylic acid, the framework structure of the zeolitic material in (ii) comprising YO.sub.2 and Al.sub.2O.sub.3, and Y being a tetravalent element; where the total content of alkali metal and alkaline earth metal in the zeolitic material in (ii), calculated as alkali metal oxide and alkaline earth metal oxide, is from 0% to 0.1% by weight, based in each case on the total weight of the zeolitic material, and where the aldol condensation catalyst in (ii) comprises, outside the framework structure of the zeolitic material present therein, from 0% to 1% by weight of vanadium, based on vanadium as vanadium(V) oxide.

A catalytic cracking agent has an active component consisting of a phosphorus-modified molecular sieve and a non-phosphorus-modified molecular sieve or only consisting of a phosphorus-modified molecular sieve. According to an electron probe microanalysis (EPMA), the D value of phosphorus in the catalytic cracking agent is 65%, preferably 68%, provided that the active component consists of the phosphorus-modified molecular sieve and the non-phosphorus-modified molecular sieve, or the D value of phosphorus in the catalytic cracking agent is 82%, preferably 84%, provided that the active component only consists of the phosphorus-modified molecular sieve.