Treatment of cha-type molecular sieves and their use in the conversion of oxygenates to olefins
A technology of molecular sieves and oxygenates, applied in molecular sieve catalysts, including molecular sieve catalysts, and producing hydrocarbons from oxygen-containing organic compounds, etc., can solve the problems of reducing MTO performance and high selectivity
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Embodiment 1
[0116] Example 1: Synthesis of high silica chabazite (no use of fluoride)
[0117] 42.72 g of N, N, N-trimethyladamantyl ammonium hydroxide (TMAAOH) 11.9 wt % aqueous solution was added to 9.24 g of deionized water, and then 8.04 g of 233 silica (PPG Industries, USA) was added to the mixture. Stir the mixture until a homogeneous gel results. 233 silica contains 0.53 wt% Na, 0.01 wt% K, 0.42 wt% alumina, and 82.2 wt% silica (the material has a Si / Al ratio of 164), and thus the composition of the gel is as follows:
[0118] 0.2TMAA:(1 / 120)Na 2 O:(1 / 328)Al 2 o 3 :1.0SiO2 2 :22H 2 o
[0119] The gel was divided into four equal fractions, denoted A-D, and each fraction was crystallized as described below.
[0120] Part A was aged at room temperature for 2 hours before adding 200PPM colloidal LEV seeds (14 wt% solids content, Si / Al=6 for the molecular sieve) based on the weight of the gel. The resulting mixture was sealed in a 23 mL Teflon-lined Parr autoclave and heated ...
Embodiment 2
[0127] Example 2: Calcination and NH 4 exchange
[0128] Calcined product A using the following protocol: (a) in flowing nitrogen, ramp to 400 °C at 10 °C / min and hold for 30 minutes; (b) switch to flowing air and start ramp at 10 °C / min to a temperature of 650°C and hold at 650°C for 4 hours. The calcined samples were ion-exchanged twice with 5 wt% ammonium chloride solution. Elemental analysis gave the following data (wt%) for the calcined and exchanged samples: Na 0.0125; Al 2 o 3 0.531 and SiO 2 84.4, which corresponds to Na 0.05 al 1.00 Si 134 .
Embodiment 3
[0129] Example 3: Gentle Steam Treatment
[0130] Calcination from Example 2 and NH 4 The exchanged samples were loaded into two enamel-bottomed quartz tubes with the enamel in the middle of the quartz tubes. The large pipe and two smaller pipes are arranged vertically in the pipe furnace. Nitrogen alone or nitrogen and steam in a molar ratio of 660:100 are fed into the pipe from the bottom of the large pipe. The total pressure is atmospheric pressure, and the temperature is increased rapidly to 500°C at a rate of 10°C / min, while continuing to feed nitrogen. After the temperature had stabilized at 500° C., feeding of nitrogen with steam was started. A first sample was recovered after 48 hours of steaming and a second sample was recovered after 96 hours. The MTO performance of these samples as well as the non-steamed samples prepared in Example 2 was tested.
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