An understanding of the thermodynamics of the complexation process utilized in sustaining drug release in clay matrices is of great importance.Several characterisation techniques as well as isothermal calorimetry were...An understanding of the thermodynamics of the complexation process utilized in sustaining drug release in clay matrices is of great importance.Several characterisation techniques as well as isothermal calorimetry were utilized in investigating the adsorption process of a model cationic drug(diltiazem hydrochloride,DIL)onto a pharmaceutical clay system(magnesium aluminium silicate,MAS).X-ray powder diffraction(XRPD),attenuated total reflectance Fourier transform infrared spectroscopy(ATRFTIR)and optical microscopy confirmed the successful formation of the DIL-MAS complexes.Drug quantification from the complexes demonstrated variable behaviour in the differing media used with DIL degrading to desacetyl diltiazem hydrochloride(DC-DIL)in the 2 M HCl media.Here also,the authors report for the first time two binding processes that occurred for DIL and MAS.A competitor binding model was thus proposed and the thermodynamics obtained suggested their binding processes to be enthalpy driven and entropically unfavourable.This information is of great importance for a formulator as care and consideration should be given with appropriate media selection as well as the nature of binding in complexes.展开更多
As the core technology of methanol-to-olefins(MTO),the development of a high-efficiency and low-cost molecular sieve catalyst has always been the most important challenge.Herein,SAPO-34 molecular sieves were synthesiz...As the core technology of methanol-to-olefins(MTO),the development of a high-efficiency and low-cost molecular sieve catalyst has always been the most important challenge.Herein,SAPO-34 molecular sieves were synthesized by using three different compositions of amorphous aluminium silicate as both Si and Al source under the same conditions.The structure and composition of synthesized SAPO-34s were investigated using X-ray diffraction and X-ray fluorescence,while the morphology and physical properties were characterized using scanning electron microscopy,N2 adsorption-desorption and ammonia temperature-programmed desorption measurements.Compared to the silica sol as the Si source,the SAPO-34s prepared with amorphous aluminium silicate show the higher solid yields and crystallinity,larger surface area and lower numbers of acid sites.Besides the effect of Si,the effect of the Al source on the textural structure and catalytic performance of SAPO-34s in MTO reactions was investigated in detail.The results confirmed that the SAPO-34s prepared using amorphous aluminium silicate have low Si content and hierarchical structure,which results in a longer catalytic lifetime and higher selectivity for light olefins.The sample S2 exhibited the longest lifetime of 214 min and the highest selectivity for light olefins of 85.37%.This also provides a potential for the approach to obtain a high-efficiency catalyst with enhanced catalytic performance and low cost.展开更多
文摘An understanding of the thermodynamics of the complexation process utilized in sustaining drug release in clay matrices is of great importance.Several characterisation techniques as well as isothermal calorimetry were utilized in investigating the adsorption process of a model cationic drug(diltiazem hydrochloride,DIL)onto a pharmaceutical clay system(magnesium aluminium silicate,MAS).X-ray powder diffraction(XRPD),attenuated total reflectance Fourier transform infrared spectroscopy(ATRFTIR)and optical microscopy confirmed the successful formation of the DIL-MAS complexes.Drug quantification from the complexes demonstrated variable behaviour in the differing media used with DIL degrading to desacetyl diltiazem hydrochloride(DC-DIL)in the 2 M HCl media.Here also,the authors report for the first time two binding processes that occurred for DIL and MAS.A competitor binding model was thus proposed and the thermodynamics obtained suggested their binding processes to be enthalpy driven and entropically unfavourable.This information is of great importance for a formulator as care and consideration should be given with appropriate media selection as well as the nature of binding in complexes.
基金supported by the Technology Innovation Project of CHN Energy(No.ST930019SH12).
文摘As the core technology of methanol-to-olefins(MTO),the development of a high-efficiency and low-cost molecular sieve catalyst has always been the most important challenge.Herein,SAPO-34 molecular sieves were synthesized by using three different compositions of amorphous aluminium silicate as both Si and Al source under the same conditions.The structure and composition of synthesized SAPO-34s were investigated using X-ray diffraction and X-ray fluorescence,while the morphology and physical properties were characterized using scanning electron microscopy,N2 adsorption-desorption and ammonia temperature-programmed desorption measurements.Compared to the silica sol as the Si source,the SAPO-34s prepared with amorphous aluminium silicate show the higher solid yields and crystallinity,larger surface area and lower numbers of acid sites.Besides the effect of Si,the effect of the Al source on the textural structure and catalytic performance of SAPO-34s in MTO reactions was investigated in detail.The results confirmed that the SAPO-34s prepared using amorphous aluminium silicate have low Si content and hierarchical structure,which results in a longer catalytic lifetime and higher selectivity for light olefins.The sample S2 exhibited the longest lifetime of 214 min and the highest selectivity for light olefins of 85.37%.This also provides a potential for the approach to obtain a high-efficiency catalyst with enhanced catalytic performance and low cost.
