Thermocatalytic Degradation of Polypropylene in Presence of Aluminum Silicates

Abstract

The process of thermocatalytic conversion of polypropylene into liquid hydrocarbons using amorphous aluminum silicates with aluminum content of 1.6-12.9 wt.% as catalysts was studied. The aluminum silicates were synthesized by sol-gel method using hydrolysis of tetraethoxysilane in a presence of aluminum salt at pH=9. All samples possessed acidic sites with pKa value of 3.46-5.00 and had a developed surface. Textural properties of the aluminum silicates were determined. Thermocatalytic conversion of polypropylene was carried out in a flow fixed-bed reactor with a fixed layer of the mixture of the catalyst and the reagent at a mass ratio of polymer : catalyst of 3 : 1 in argon atmosphere with a gradual rise of temperature in the range of 300 – 450 ºС. The sample of silica, which did not contain aluminum, was demonstrated to be inactive in polypropylene degradation, while other catalysts provided conversion of polypropylene into liquid products. The highest yield of liquid products was 80% for a catalyst with an aluminum content of 8.1 wt.%. According to the results of GLC saturated hydrocarbons were identified among the products for all samples. The effect of the concentration of acidic centers on the chemical and fractional composition of the target products was shown. For the studied aluminum silicates with the same pKa values, an increase in the aluminum content favored the formation of a lighter hydrocarbon fraction. For the catalyst with the highest aluminum content the n-alkanes of С5-С10 composition were identified. These products were closest to gasoline oil fraction. This provides a possibility to consider secondary polyolefins as an alternative source of motor fuels. An influence of catalyst composition on maximal temperature of polyethylene degradation was determined by differential thermal analysis.

Catalytic Conversion of Polyolefins in the Presence of MCM-41 Type Mesoporous Materials

“…Thermogravimetric analysis revealed a more significant decrease in temperature of the polypropylene degradation over H-MCM-41(70) compared to H-MCM-41(140). However, this observation cannot be regarded as a common pattern, because our earlier experiments on polypropylene degradation in the presence of amorphous aluminosilicates with different aluminum contents revealed the lack of dependence of the decrease in the maximum temperature of polypropylene degradation on the increase in the aluminum content of the catalyst sample [28].…”

Thermocatalytic Conversion of Plastics into Liquid Fuels over Clays

“…The process of the thermocatalytic transformation using these catalysts mostly depends on the presence of acid sites [ 2 ] and the number and size of catalyst pores [ 3 ]. Many works, including those of our group, are devoted to the use of synthetic aluminosilicates [ 4 , 5 ]. In particular, the synthesis and application of specific nanosponges of solid acids, named “acidic aluminosilicates”, should be mentioned as one of the latest achievements [ 6 ].…”

Impact on Humans of Pollutants in Moscow

“…На их долю приходится около 95% выбросов вредных веществ в атмосферу с разным классом опасности. Все данные загрязнители образуются в результате деятельности промышленных [4,5], железнодорожных предприятий, объектов энергетики [1] и автотранспорта. Так, например, промышленность является главным источником тяжелых металлов и их соединений [1,10,12,39].…”

“…Кроме перечисленных веществ, также в атмосферный воздух поступают различные специфические вещества, выбрасываемые отдельными производствами, предприятиями, цехами. Действие данных веществ (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) может приводить к атмосферным загрязнениям, к изменению рН и, как следствие, может сказаться как на почве, так и на организме человека.…”