Natural mordenite originated from volcanic soils in Greek islands was treated with sulfuric acid aqueous solutions of different concentrations and solid mass/solution volumes. The samples were characterized using various techniques (N₂-physisorption, XRD, ATR-FTIR, SEM-EDS, TEM, Microelectrophoresis, Equilibrium pH) and tested in the transformation of limonene into p-cymene in the presence of atmospheric air at various temperatures and reaction times. The acid treatment is causing the removal of sodium oxide located inside the framework micropores and the small inter-fiber mesopores. This, in turn, increases drastically the BET specific surface area and unmasks negatively charged surface sites which are transformed into acid sites by adsorbing H⁺/H₂O⁺ ions. The relatively low extent removal of Al³⁺ ions does not disturb the framework of natural mordenite nor its fibrous morphology. The development of micropores and small mesopores surface area and surface acid sites are transforming the catalytically inactive natural mordenite into very active catalysts. The increase in the conversion and the yield of p-cymene follows the increase in the BET specific surface area. A novel mechanism was experimentally established involving a catalytic step followed by a non catalytic one. The first step involves adsorption of limonene on acid sites via the exocyclic double bond to form the more stable tertiary carbenium ion from which terpinolenes, terpinenes and “polymeric species” are formed. The “transition state shape selectivity” manifested by the catalysts studied does not allow the formation of intermediate disproportionation products. In the second step, catalyst-free aromatization and “polymerization” of terpinolenes and terpinenes were found to occur. The aromatization was proposed to proceed by abstraction of an allylic hydrogen resulting to free radical (R) followed by combination with O₂ and radical chain propagation to yield allylic peroxides ([ROO]) which by elimination of (HOO) lead to the production of p-cymene. Moreover, high molecular weight compounds may be formed as radicals are combined to alkyl and peroxyl dimmers that may be polymerized. The experimental parameters concerning the acid treatment and reaction conditions were optimized for maximizing the amount of the produced p-cymene keeping as low as possible the amount of the produced polymeric species.

用不同浓度和固体质量/溶液体积的硫酸水溶液处理源自希腊岛屿火山土壤的天然丝光沸石。使用各种技术（N _2-物理吸附，XRD，ATR-FTIR，SEM-EDS，TEM，微电泳，平衡pH）对样品进行表征，并在不同温度下存在大气的条件下对柠檬烯向对甲基苯甲基的转化进行了测试。和反应时间。酸处理导致去除位于框架微孔和较小的纤维间中孔内部的氧化钠。反过来，这会大幅增加BET比表面积，并掩盖带负电荷的表面位点，这些表面位点通过吸附H ⁺ / H转变为酸性位点₂ O ⁺离子。Al ³⁺离子的去除程度相对较低，不会干扰天然丝光沸石的骨架，也不会破坏其纤维形态。微孔和小中孔表面积和表面酸位的发展正在将无催化活性的天然丝光沸石转变为活性很高的催化剂。转化率的提高和p的收率-cymene跟随BET比表面积的增加。实验上建立了一种新的机制，包括催化步骤，然后是非催化步骤。第一步涉及柠檬烯通过环外双键在酸性位点上的吸附，从而形成更稳定的叔碳鎓离子，从而形成萜品油烯，萜品烯和“聚合物”。由研究的催化剂表现出的“过渡态形状选择性”不允许形成中间歧化产物。在第二步中，发现发生了松油松烯和松油烯的无催化剂芳构化和“聚合”。提出通过以下方式进行芳构化：提取烯丙基氢以产生自由基（R ），然后与O ₂结合自由基链的繁殖产生烯丙基过氧化物（[ROO ]），通过消除（HOO ）导致生成对-甲基异丙基苯。此外，当自由基与可聚合的烷基和过氧二聚体结合时，可形成高分子量化合物。优化了有关酸处理和反应条件的实验参数，以使所产生的对甲基苯甲基的量最大化，并保持尽可能低的所产生的聚合物种类的量。