A process for producing a molecular sieve material having an X-ray diffraction pattern with at least one peak at a position greater than 18 Angstrom Units d-spacing with a relative intensity of 100, and a benzene adsorption capacity of greater than 15 grams benzene per 100 grams anhydrous crystal at 50 torr and 25°C, wherein said molecular sieve is MCM-41, said process comprising the steps: (a) preparing a synthesis mixture capable of forming said molecular sieve material by combining in a reactor equipped with a mixer having a Froude number of at least 1, at least water, a source of at least one oxide selected from the group consisting of trivalent element X and tetravalent element Y, a source of an alkali or alkaline earth metal M, and an organic directing agent having the formula R 1 R 2 R 3 R 4 Q +, wherein Q is nitrogen or phosphorus and wherein at least one of R 1, R 2, R 3 and R 4 is selected from the group consisting of aryl of from 6 to 36 carbon atoms, alkyl of from 6 to 36 carbon atoms and combinations thereof and the remainder of R 1, R 2, R 3 and R 4 is selected from the group consisting of hydrogen, alkyl of from 1 to 5 carbon atoms and combinations thereof, said synthesis mixture having a solids content of at least 20 wt%; (b) heating the synthesis mixture in the reactor while agitating the mixture with said mixer to form a product mixture comprising water and crystals of said molecular sieve material; and then (c) unsealing the reactor and removing at least part of the water from the product mixture in the reactor so as to decrease the water content of product mixture inside the reactor by at least 5 wt%; wherein the reactor has a capacity of at least 5 liters and a length to diameter ratio greater than 0.75, and the mixer comprises at least one blade located on a shaft rotatable about an axis oriented at no more than 10 degrees from horizontal, and wherein the Froude number (Fr) of the mixer having an impeller of diameter (d) in meters and rotating at N revolutions per second is defined by the following equation: Fr = N 2 d / g where g is the acceleration due to gravity (9.81 m/s 2). (a) preparing a synthesis mixture capable of forming said molecular sieve material by combining in a reactor equipped with a mixer having a Froude number of at least 1, at least water, a source of at least one oxide selected from the group consisting of trivalent element X and tetravalent element Y, a source of an alkali or alkaline earth metal M, and an organic directing agent having the formula R 1 R 2 R 3 R 4 Q +, wherein Q is nitrogen or phosphorus and wherein at least one of R 1, R 2, R 3 and R 4 is selected from the group consisting of aryl of from 6 to 36 carbon atoms, alkyl of from 6 to 36 carbon atoms and combinations thereof and the remainder of R 1, R 2, R 3 and R 4 is selected from the group consisting of hydrogen, alkyl of from 1 to 5 carbon atoms and combinations thereof, said synthesis mixture having a solids content of at least 20 wt%; (b) heating the synthesis mixture in the reactor while agitating the mixture with said mixer to form a product mixture comprising water and crystals of said molecular sieve material; and then (c) unsealing the reactor and removing at least part of the water from the product mixture in the reactor so as to decrease the water content of product mixture inside the reactor by at least 5 wt%;